全文获取类型
收费全文 | 36826篇 |
免费 | 921篇 |
国内免费 | 3篇 |
专业分类
财政金融 | 6104篇 |
工业经济 | 2523篇 |
计划管理 | 5770篇 |
经济学 | 7572篇 |
综合类 | 346篇 |
运输经济 | 221篇 |
旅游经济 | 568篇 |
贸易经济 | 5245篇 |
农业经济 | 1569篇 |
经济概况 | 4319篇 |
水利工程 | 3437篇 |
信息产业经济 | 1篇 |
邮电经济 | 75篇 |
出版年
2021年 | 256篇 |
2020年 | 389篇 |
2019年 | 542篇 |
2018年 | 784篇 |
2017年 | 749篇 |
2016年 | 744篇 |
2015年 | 528篇 |
2014年 | 786篇 |
2013年 | 3569篇 |
2012年 | 1178篇 |
2011年 | 1258篇 |
2010年 | 902篇 |
2009年 | 1069篇 |
2008年 | 1169篇 |
2007年 | 1199篇 |
2006年 | 1147篇 |
2005年 | 1087篇 |
2004年 | 1086篇 |
2003年 | 826篇 |
2002年 | 748篇 |
2001年 | 737篇 |
2000年 | 722篇 |
1999年 | 648篇 |
1998年 | 629篇 |
1997年 | 595篇 |
1996年 | 598篇 |
1995年 | 529篇 |
1994年 | 581篇 |
1993年 | 574篇 |
1992年 | 550篇 |
1991年 | 585篇 |
1990年 | 518篇 |
1989年 | 433篇 |
1988年 | 438篇 |
1987年 | 444篇 |
1986年 | 436篇 |
1985年 | 642篇 |
1984年 | 590篇 |
1983年 | 595篇 |
1982年 | 578篇 |
1981年 | 506篇 |
1980年 | 486篇 |
1979年 | 498篇 |
1978年 | 417篇 |
1977年 | 365篇 |
1976年 | 315篇 |
1975年 | 283篇 |
1974年 | 272篇 |
1973年 | 257篇 |
1972年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
51.
52.
The rise of environmentalism in the past decade has become a major transforming force in pollutive and hazard prone industries. Corporate environmental responsiveness is not simply a peripheral and one of the many ‘social’ or ‘ethical’ issues facing business. It is becoming a central concern for competitiveness, productivity, and profitability. It is creating strategic transformation of companies in a diverse range of industries such as, Autos, Chemicals, Oil, Fast Foods, Power Generation, Pharmaceuticals, etc. The process of environmentally directed self-renewal, called ‘greenewal’ here, affects all aspects of companies. It implies changes in products, production systems, waste management practices and internal systems. It seeks to make companies simultaneously more competitive and environmentally responsible. This paper describes the pressures of and responses to environmentalism in a selected set of industries. It examines the processes of greenewal that companies are undergoing. It identifies implications for strategic greening of firms. 相似文献
53.
J. J. Graafland 《De Economist》1992,140(4):501-514
Summary In most traditional macroeconomic models for The Netherlands the wage equation is specified by a Phillips curve, in which wage growth is negatively related to the unemployment rate. This paper shows, however, that wage formation can better be described by the so-called wage curve, in which the wage level, instead of wage growth, depends negatively on the unemployment rate.The author thanks S.K. Kuipers and D.A.G. Draper and other colleagues of the Central Planning Bureau for their useful comments. 相似文献
54.
S J Chung S Balaji M Matheswaran T Ramesh I S Moon 《Water science and technology》2007,55(1-2):261-266
This study investigates the hybrid mediated electrochemical oxidation (HMEO) technology, which is a newly developed non thermal electrochemical oxidation process for organic destruction. A combination of ozone and ultrasonication processes to the mediated electrochemical oxidation (MEO) process is termed as hybrid mediated electrochemical oxidation. The electrochemical cell was developed in this laboratory. In the present study, several organic compounds, such as phenol, benzoquinone and ethylenediaminetetraacetic acid (EDTA), were chosen as the model organic pollutants to be destructed by the hybrid process. The organic destruction was monitored based on the CO2 generation and total organic carbon (TOC) reduction. The HMEO process was found to be extremely effective in the destruction of all the target organics chosen in this study. The information obtained from this study will provide an insight in adopting this technique for dealing with more recalcitrant organics (POPs). 相似文献
55.
56.
P Navarro J Sarasa D Sierra S Esteban J L Ovelleiro 《Water science and technology》2005,51(1):113-120
Wine industry wastewaters contain a high concentration of organic biodegradable compounds as well as a great amount of suspended solids. These waters are difficult to treat by conventional biological processes because they are seasonal and a great flow variation exists. Photocatalytic advanced oxidation is a promising technology for waters containing high amounts of organic matter. In this study we firstly investigated the application of H2O2 as oxidant combined with light (artificial or natural) in order to reduce the organic matter in samples from wine industry effluents. Secondly, we studied its combination with heterogeneous catalysts: titanium dioxide and clays containing iron minerals. The addition of photocatalysts to the system reduces the required H2O2 concentration. Although the H2O2/TiO2 system produces higher efficiencies, the H2O2/clays system requires a H2O2 dosage between three and six times lower. 相似文献
57.
58.
A new 16S rRNA-targeted oligonucleotide probe, specific for the cluster of fatty acid beta-oxidizing syntrophic bacteria of the family Syntrophomonadaceae was designed for fluorescence in situ hybridization. This probe was evaluated with target as well as non-target cultures. Moreover this probe was assessed with butyrate and oleate degrading enrichment cultures and methanogenic sludges from full-scale plants. The results showed that the probe revealed the presence of fatty acid beta-oxidizing syntrophic bacteria in some of the samples analyzed. However, cell quantification was possible only in enrichment cultures and in a flocculent sludge from a reactor that treats lipid-rich wastewaters, but not in methanogenic granular sludges from upflow anaerobic sludge blanket reactors. 相似文献
59.
This study investigates the phenotype of turbulent (Re = 5,200) and laminar (Re = 2,000) flow-generated Pseudomonas fluorescens biofilms. Three P. fluorescens strains, the type strain ATCC 13525 and two strains isolated from an industrial processing plant, D3-348 and D3-350, were used throughout this study. The isolated strains were used to form single and binary biofilms. The biofilm physiology (metabolic activity, cellular density, mass, extracellular polymeric substances, structural characteristics and outer membrane proteins [OMP] expression) was compared. The results indicate that, for every situation, turbulent flow-generated biofilms were more active (p < 0.05), had more mass per cm(2) (p < 0.05), a higher cellular density (p < 0.05), distinct morphology, similar matrix proteins (p > 0.1) and identical (isolated strains -single and binary biofilms) and higher (type strain) matrix polysaccharides contents (p < 0.05) than laminar flow-generated biofilms. Flow-generated biofilms formed by the type strain revealed a considerably higher cellular density and amount of matrix polysaccharides than single and binary biofilms formed by the isolated strains (p < 0.05). Similar OMP expression was detected for the several single strains and for the binary situation, not dependent on the hydrodynamic conditions. Binary biofilms revealed an equal coexistence of the isolated strains with apparent neutral interactions. In summary, the biofilms formed by the type strain represent, apparently, the worst situation in a context of control. The results obtained clearly illustrate the importance of considering strain variation and hydrodynamics in biofilm development, and complement previous studies which have focused on physical aspects of structural and density differences. 相似文献
60.
Jennifer G. Winter M. Catherine Eimers Peter J. Dillon Lem D. Scott Wolfgang A. Scheider Campbell C. Willox 《Journal of Great Lakes research》2007,33(2):381-396
Total phosphorus (TP) inputs to Lake Simcoe have led to hypolimnetic dissolved oxygen (DO) depletion and loss of cold water fish habitat. Since 1990, efforts have been made to reduce the total TP input to the lake below a defined target of 75 t/year, which was predicted to lead to reductions in spring TP concentration and improvements in end-of-summer hypolimnetic DO concentrations. The total TP load to the lake during the most recent period of record (1998/99-2003/04) ranged from 53 to 76 t/yr and averaged 67 t/yr, compared to an average of 114 t/yr estimated between 1990/91 and 1997/98 (range 85-157 t/yr). Reductions in TP loads from the catchment via tributary discharge (∼26 t) accounted for the majority of the decrease in total load between the two time periods. Total P concentrations decreased significantly in four out of six long-term monitored tributaries; however, concentrations in all six tributaries remain above the level recommended to avoid nuisance plant growth (30 μg/L). Although TP loads to the lake are currently below the target 75 t/yr, excessive growths of filamentous algae and macrophytes continue to be a problem in the nearshore zone. End-of-summer minimum hypolimnetic DO concentrations (average 4.3 mg/L, 1998/99-2003/04) remain substantially below the level (7 mg/L) that is considered protective of lake trout. Efforts to reduce TP loads to the lake therefore need to continue. 相似文献