全文获取类型
收费全文 | 11753篇 |
免费 | 318篇 |
专业分类
财政金融 | 1828篇 |
工业经济 | 820篇 |
计划管理 | 1695篇 |
经济学 | 2125篇 |
综合类 | 119篇 |
运输经济 | 69篇 |
旅游经济 | 153篇 |
贸易经济 | 1493篇 |
农业经济 | 475篇 |
经济概况 | 1070篇 |
水利工程 | 2202篇 |
信息产业经济 | 1篇 |
邮电经济 | 21篇 |
出版年
2021年 | 98篇 |
2020年 | 142篇 |
2019年 | 218篇 |
2018年 | 279篇 |
2017年 | 279篇 |
2016年 | 293篇 |
2015年 | 171篇 |
2014年 | 263篇 |
2013年 | 1076篇 |
2012年 | 428篇 |
2011年 | 430篇 |
2010年 | 332篇 |
2009年 | 371篇 |
2008年 | 405篇 |
2007年 | 390篇 |
2006年 | 433篇 |
2005年 | 321篇 |
2004年 | 333篇 |
2003年 | 219篇 |
2002年 | 237篇 |
2001年 | 234篇 |
2000年 | 245篇 |
1999年 | 214篇 |
1998年 | 221篇 |
1997年 | 209篇 |
1996年 | 219篇 |
1995年 | 185篇 |
1994年 | 180篇 |
1993年 | 187篇 |
1992年 | 195篇 |
1991年 | 198篇 |
1990年 | 185篇 |
1989年 | 145篇 |
1988年 | 127篇 |
1987年 | 126篇 |
1986年 | 137篇 |
1985年 | 196篇 |
1984年 | 158篇 |
1983年 | 146篇 |
1982年 | 120篇 |
1981年 | 144篇 |
1980年 | 136篇 |
1979年 | 133篇 |
1978年 | 139篇 |
1977年 | 74篇 |
1976年 | 102篇 |
1975年 | 78篇 |
1974年 | 73篇 |
1973年 | 75篇 |
1972年 | 71篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
Sound financial planning and financial advice is necessary to achieve retirement income adequacy. The shift from defined benefit to defined contribution pension plans and the recent bankruptcy of Enron Corporation underscore the importance of managing retirement accumulation and liquidation risks. This study analyzes the effectiveness and adequacy of institutional-provided information and advice on employees' retirement planning decisions and their satisfaction with financial resources during retirement. Results suggest that retirement planning should begin earlier in an employee's career and that employer-provided retirement information and advice is a highly valued service. Gender, planning practices, job classification, and age are all significant predictors of satisfaction with financial resources during retirement. Targeting women and union employees with retirement information and advice that focuses on allocating contributions using a balanced portfolio approach should result in significant increases in satisfaction with financial resources during retirement. Regulatory objectives should focus on reducing retirement accumulation and liquidation risks, improving the delivery of professional financial advice to plan participants, and expanding qualified retirement plan choice for all labor force participants. To encourage employer participation in employee retirement planning, employers acting in "good faith" should be federally protected from liability for providing retirement planning information and advice to employees. 相似文献
122.
A pilot-scale fluidised pellet bed (FPB) bioreactor, which combines chemical coagulation, biological degradation, particle pelletisation and separation in one unit, was applied for onsite wastewater treatment and reuse. As a result of rational use of inorganic coagulant and organic polymer and moderate mechanical agitation, spherical particles were generated in the upflow column and a well-fluidised bed was formed. With a continuous supply of dissolved oxygen through a recycling loop, an aerobic condition was kept in the bottom section of the FPB column. Under such conditions the pellets in the FPB column showed the following characteristics: (1) compact structure and high density; (2) rich in microorganisms; and (3) high MLSS and MLVSS concentrations. Therefore, the FPB bioreactor achieved more than 90% removal of SS, COD, BOD and TP from raw domestic wastewater within a total hydraulic retention time (HRT) of only about 30 minutes. It also showed nitrification and denitrification ability and the TN removal could be about 50% as the recycling ratio was increased to 1:1. The treated water quality is generally competitive with the secondary effluent from a conventional activated sludge process. With these advantages the FPB bioreactor is recommendable as a compact system for onsite wastewater treatment and reuse. 相似文献
123.
Kiyatkin A. K. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》1989,23(6):325-328
Power Technology and Engineering - 相似文献
124.
Uncertainty in water quality model predictions is inevitably high due to natural stochasticity, model uncertainty, and parameter uncertainty. An integrated modelling system (modified-BASINS) under uncertainty is described and demonstrated for use in receiving-water quality prediction and watershed management. A Monte Carlo simulation was used to investigate the effect of various uncertainty types on output prediction. Without pollution control measures in the watershed, the concentrations of total nitrogen (T-N) and total phosphorus (T-P) in the Hwaong Reservoir, considering three uncertainty types, would be less than about 4.4 and 0.23 mg L(-1), respectively, in 2012, with 90% confidence. The effects of two watershed management practices, wastewater treatment plants (WWTP) and constructed wetlands (WETLAND), were evaluated. The combined scenario (WWTP + WETLAND) was the most effective at improving reservoir water quality, bringing concentrations of T-N and T-P in the Hwaong Reservoir to less than 3.4 and 0.14 mg L(-1), 24 and 41% improvements, respectively, with 90% confidence. Overall, the Monte Carlo simulation in the integrated modelling system was practical for estimating uncertainty and reliable in water quality prediction. The approach described here may allow decisions to be made based on the probability and level of risk, and its application is recommended. 相似文献
125.
K Lenz S N Mahnik N Weissenbacher R M Mader P Krenn S Hann G Koellensperger M Uhl S Knasmüller F Ferk W Bursch M Fuerhacker 《Water science and technology》2007,56(12):141-149
Cytostatic agents are applied in cancer therapy and subsequently excreted into hospital wastewater. As these substances are known to be carcinogenic, mutagenic and toxic for reproduction, they should be removed from wastewater at their source of origin.In this study the fate and effects of the cancerostatic platinum compounds (CPC) cisplatin, carboplatin, oxaliplatin, 5-fluorouracil (5-FU) and the anthracyclines doxorubicin, daunorubicin and epirubicin were investigated in hospital wastewater. Wastewater from the in-patient treatment ward of a hospital in Vienna was collected and monitored for the occurrence of the selected drugs. A calculation model was established to spot the correlation between administered dosage and measured concentrations. To investigate the fate of the selected substances during wastewater treatment, the oncologic wastewater was treated in a pilot membrane bioreactor system (MBR) and in downstream advanced wastewater treatment processes (adsorption to activated carbon and UV-treatment). Genotoxic effects of the oncologic wastewater were assessed before and after wastewater treatment followed by a risk assessment.Monitoring concentrations of the selected cytostatics in the oncologic wastewater were in line with calculated concentrations. Due to different mechanisms (adsorption, biodegradation) in the MBR-system 5 - FU and the anthracyclines were removed < LOD, whereas CPC were removed by 60%. In parallel, genotoxic effects could be reduced significantly by the MBR-system. The risk for humans, the aquatic and terrestrial environment by hospital wastewater containing cytostatic drugs was classified as small in a preliminary risk assessment. 相似文献
126.
P. K. Edwards 《Industrial Relations Journal》1995,26(3):204-220
Three outcomes of personnel practice (rates of discipline, quitting and absence) are analysed. There was no firm association with measures of practices associated with Human Resource Management. By contrast, unionisation was strongly associated with the low use of discipline and low quit rates: union ‘voice’ remains influential in the 1990s. 相似文献
127.
In Western Europe in the last two decades the unemployment rate has increased during cyclical downturns only to persist at or around the higher level in the following phase of economic recovery. One of the most notable exceptions to this pattern of unemployment persistence, often termed hysteresis, is the United States. The following article examines the empirical evidence and the possible theoretical explanations for this difference. 相似文献
128.
Astashev M. G. Lunin K. A. Panfilov D. I. Petrov M. I. Rashitov P. A. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2021,55(2):310-313
Power Technology and Engineering - The article describes the issues of the operation of semiconductor regulators-stabilizers of alternating voltage for distribution networks (PRSPN). The relevance... 相似文献
129.
Anakhaev K. N. Belikov V. V. Amshokov B. Kh. Anakhaev K. K. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2021,55(3):344-347
Power Technology and Engineering - Advanced methods for determining the hydrological and geomorphological characteristics of torrential pools, which are important for the design of reliable and... 相似文献
130.
Professor Rolf Färe Dr. James Logan Professor C. A. K. Lovell 《Journal of Economics》1989,50(2):171-180
We are grateful to a perceptive referee for many constructive comments on an earlier version of this paper entitled The Economics of Content Protection: A Dual Approach. The usual disclaimer applies. 相似文献