全文获取类型
收费全文 | 11735篇 |
免费 | 353篇 |
国内免费 | 3篇 |
专业分类
财政金融 | 1726篇 |
工业经济 | 796篇 |
计划管理 | 1672篇 |
经济学 | 2139篇 |
综合类 | 220篇 |
运输经济 | 43篇 |
旅游经济 | 133篇 |
贸易经济 | 1516篇 |
农业经济 | 393篇 |
经济概况 | 1123篇 |
水利工程 | 2299篇 |
信息产业经济 | 1篇 |
邮电经济 | 30篇 |
出版年
2020年 | 122篇 |
2019年 | 153篇 |
2018年 | 257篇 |
2017年 | 262篇 |
2016年 | 254篇 |
2015年 | 173篇 |
2014年 | 242篇 |
2013年 | 956篇 |
2012年 | 384篇 |
2011年 | 395篇 |
2010年 | 300篇 |
2009年 | 333篇 |
2008年 | 352篇 |
2007年 | 403篇 |
2006年 | 346篇 |
2005年 | 309篇 |
2004年 | 324篇 |
2003年 | 226篇 |
2002年 | 185篇 |
2001年 | 234篇 |
2000年 | 220篇 |
1999年 | 196篇 |
1998年 | 192篇 |
1997年 | 232篇 |
1996年 | 205篇 |
1995年 | 199篇 |
1994年 | 191篇 |
1993年 | 183篇 |
1992年 | 212篇 |
1991年 | 222篇 |
1990年 | 170篇 |
1989年 | 174篇 |
1988年 | 148篇 |
1987年 | 143篇 |
1986年 | 144篇 |
1985年 | 203篇 |
1984年 | 177篇 |
1983年 | 194篇 |
1982年 | 154篇 |
1981年 | 187篇 |
1980年 | 163篇 |
1979年 | 186篇 |
1978年 | 166篇 |
1977年 | 142篇 |
1976年 | 153篇 |
1975年 | 127篇 |
1974年 | 128篇 |
1973年 | 105篇 |
1972年 | 87篇 |
1971年 | 80篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Stormwater reuse is increasing in popularity as a technique for overcoming water shortages in urban Australia. However, technology for the reliable treatment of stormwater for reuse is still not fully developed. This paper presents the first steps in refining biofilters for stormwater reuse. Six different filter media were selected, to target specific stormwater pollutants, as well as support plant growth. They were tested in the laboratory, where the filters were dosed three times per week with semi-synthetic stormwater for five weeks. Pollutant removal performance was monitored, and revealed that all soil-based filters performed similarly (while sand filters behaved somewhat differently). All filters removed more than 80% of solids and greater than 90% of lead, copper, and zinc. Three filter types were able to remove some phosphorus (particularly in the top 30 cm of the media). Apart from sand, all filter media were net producers of nitrogen, leading to an important conclusion that non-vegetated, soil-based filters are not suitable for targeting nutrients. However, since heavy metals are the primary pollutant of concern with respect to stormwater reuse for irrigation (the most popular end-use), it was concluded that biofilters may be promising technologies for treatment of stormwater for reuse. 相似文献
52.
S B Watson M Charlton Y R Rao T Howell J Ridal B Brownlee C Marvin S Millard 《Water science and technology》2007,55(5):1-8
The Laurentian Great Lakes of North America are a drinking water source for millions of Canadian and US consumers. These waterbodies have undergone extensive change over the past century as a result of widespread degradation and remediation. Many of the Lakes are prone to taste and odour (T&O), and although these outbreaks have been poorly monitored, evidence suggests that they are increasing in frequency. Tracing and controlling T&O in such large systems presents a challenging task, due to their physical size and complexity. This paper presents an overview of recent investigative and management approaches to T&O in Lake Ontario and its outflow, the St. Lawrence River. We have identified three distinct patterns of T&O in these source-waters, caused by geosmin and 2-methylisoborneol and differing in their planktonic and benthic sources, and temporal and spatial dynamics. Each pattern has required a different approach by scientists and management, in partnership with the water industry. We have shown these T&O outbreaks are caused and moderated by physical, chemical and biological mechanisms over a spectrum of spatial and temporal scales. Canadian municipalities affected by these outbreaks have been key to the investigation of the links between T&O and ecosystem processes with the aim to develop more proactive water treatment and long-term management. 相似文献
53.
The Uniform Covering by Probabilistic Rejection (UCPR) algorithm was used, in conjunction with the Soil and Water Assessment Tool (SWAT) model, to identify P loads from point source and nonpoint source polluters in the upper Etowah River basin (UERB) in Georgia. The key findings of the research are as follows. The mean absolute error was preferred over the root mean square error as a search criterion for the UCPR algorithm when water quality observations are scarce. The undocumented P load from point sources in the UERB was consistently estimated as about 43 kg/d by the proposed method; but the method was not able to identify the broiler litter application rate to the poultry/beef operation pastures. Point sources (both documented and undocumented), poultry/beef operation pastures, and forests are the three major contributors of P. During 1992-1996, on average they accounted for 36.4, 31.7, and 17.2% of P load from the UERB, respectively. 相似文献
54.
Leiser Silva Eugenio Figueroa B. Jennifer Gonzlez-Reinhart 《Information and Organization》2007,17(4):232-265
This paper centers on the interpretation attributed by organizational members to the information systems (IS) alignment concept. Its objective is to study IS alignment in professional organizations. Specifically, it reports on an interpretive study conducted in five Chilean organizations; four professional and one entrepreneurial, of which two are private and three are public. The theoretical background of our study is derived from three IS strategic alignment conceptualizations: managerial, emergent and critical. These concepts formed our theoretical framework that guided data collection and analysis. The study centers on the meanings organizational members assigned to IS strategic alignment, as well as their views on the barriers that hinder achieving this level of organizational integration. The analysis results are summarized in seven hermeneutic themes that point out the different connotations the organizations assigned to IS alignment. The significance of the findings are summarized in four insights that formulate theoretical and practical implications. These insights refer to: (1) the difficulties of achieving alignment for professional organizations, particularly public ones, (2) the limitations these organizations have in being agile, (3) the rationale for acquiring technology and determining IT skills, and (4) the imperative meaning that CIOs attribute to IS alignment. The paper concludes with a reflection on the limitations and relevance of the research. 相似文献
55.
Norman B. Macintosh 《International Review of Financial Analysis》2003,12(4):453-465
This paper, following McGoun's (1997) seminal article comparing the economy of financial securities to a hyperreal poker game, argues that finance and accounting researchers should take the “linguistic turn” that has rejuvenated theory and research in many, if not most, of the social science and humanities in recent decades. In general terms, this means following Ludwig Wittgenstein's language game paradigm rather than Karl Popper's scientific deductive hypothesis testing methodology. The paper illustrates this by drawing on some of Jean Baudrillard's' ideas, particularly his concept of hyperreality and his phases of the image theoretic.The paper presents a poststructuralist genealogical analysis of the radical ruptures and reformulation of the meaning attributed to the accounting sign of earnings over the feudal, counterfeit, production, and simulation eras. It concludes that, as with many other signs in contemporary society, the earnings sign no longer has any relationship with, nor does it any longer refer to, any real or intrinsic profit but instead floats ungrounded in today's financial economy.The paper recommends that researchers in finance and accounting adopt paradigms from literary theory, semiotics, linguistics, and semiology rather than continue to rely on economics-based theory, which has lost its power for explaining and predicting happenings in today's financial economy of self-referencing models and images. 相似文献
56.
57.
Progress and Backwardness in English Agriculture, 1500-1650 总被引:2,自引:0,他引:2
R. B. OUTHWAITE 《The Economic history review》1986,39(1):1-18
58.
俄罗斯极北地区的水电工程解决了许多在严寒条件和永冻土上进行施工的难题;表明水电站的修建是可行的,投入是很低的。这些水电站建成后都能在一定程度上满足北方地区的用电需求。 相似文献
59.
A Product and Process Model of the Technology-Sourcing Decision 总被引:1,自引:0,他引:1
The technology‐sourcing decision traditionally has examined the choice either to innovate internally or to acquire technology from outside sources. The increasing complexity of this decision requires a move beyond the simple “make‐versus‐buy” dichotomy. We seek to test factors that influence the technology decision of subsidiaries for product and process technology across the continuum of options from internal development to outsourcing. We also explore concordance between the research streams of new product development and technology sourcing. Regression models are used to analyze data from 187 subsidiaries that suggest product and process technology development decisions sometimes are associated with similar factors and at other times they diverge. In particular, we find that external product and process technology acquisition decisions are associated negatively with differentiation goals and associated positively with product dynamism. While external product acquisition is associated negatively with a low cost goal and positively with increasing distance between primary marketing and R&D operations, external process technology acquisition is associated positively with high competitive intensity. Implications include the following: (1) While external product technology acquisition may provide quicker or even less expensive initial solutions, external reliance makes it difficult to maintain a long‐term positional advantage; (2) When greater distances separate key functional activities, external partners may provide solutions that are more responsive to local consumer needs, and the potential for improved communication may allow for quicker adaptation and increased flexibility; (3) In highly dynamic product situations, internal development, while providing greater control, can be expensive and can result in technologies that are not accepted by the marketplace; and (4) As competitive intensity increases, strategic imperatives may reduce the focus on product design and development and may require increasing concentration on manufacturing costs and efficiencies. 相似文献
60.
Industrial solid-liquid separation processes, such as pressure filtration or membrane processes, involve the application of pressure to suspensions. In response, some water is extracted, the suspension volume is reduced, and the dispersed aggregates start to form a network. In recent works, we aimed to make a prediction for the response of aggregates to stress which occurs during a filtration. We chose model systems made of aggregated silica nanoparticles. Some of these systems offer a strong resistance to applied stresses, and retain their permeability; others yield and collapse. We used small angle neutron scattering by which we can locally quantify the particle distribution withi the network to determine the processes by which particles reorganise during collapse: we found that reordering processes at the scale of 1 to 10 particle diameters control the course of collapse and the loss of permeability. Finally we constructed a numerical model for describing the processes by which colloidal aggregates are compressed. This model predicts that the response of such networks to pressure follows some scaling laws, which depend only on the elastic vs. dissipative nature of interparticle bonds. 相似文献