全文获取类型
收费全文 | 24811篇 |
免费 | 581篇 |
国内免费 | 1篇 |
专业分类
财政金融 | 3559篇 |
工业经济 | 1502篇 |
计划管理 | 3133篇 |
经济学 | 3994篇 |
综合类 | 202篇 |
运输经济 | 133篇 |
旅游经济 | 295篇 |
贸易经济 | 2838篇 |
农业经济 | 883篇 |
经济概况 | 2768篇 |
水利工程 | 6081篇 |
信息产业经济 | 1篇 |
邮电经济 | 4篇 |
出版年
2021年 | 215篇 |
2020年 | 275篇 |
2019年 | 334篇 |
2018年 | 599篇 |
2017年 | 590篇 |
2016年 | 558篇 |
2015年 | 360篇 |
2014年 | 568篇 |
2013年 | 2189篇 |
2012年 | 836篇 |
2011年 | 812篇 |
2010年 | 663篇 |
2009年 | 774篇 |
2008年 | 763篇 |
2007年 | 796篇 |
2006年 | 728篇 |
2005年 | 612篇 |
2004年 | 659篇 |
2003年 | 467篇 |
2002年 | 439篇 |
2001年 | 420篇 |
2000年 | 459篇 |
1999年 | 413篇 |
1998年 | 402篇 |
1997年 | 391篇 |
1996年 | 387篇 |
1995年 | 351篇 |
1994年 | 357篇 |
1993年 | 389篇 |
1992年 | 382篇 |
1991年 | 387篇 |
1990年 | 363篇 |
1989年 | 330篇 |
1988年 | 320篇 |
1987年 | 305篇 |
1986年 | 326篇 |
1985年 | 409篇 |
1984年 | 382篇 |
1983年 | 375篇 |
1982年 | 344篇 |
1981年 | 350篇 |
1980年 | 365篇 |
1979年 | 306篇 |
1978年 | 310篇 |
1977年 | 307篇 |
1976年 | 288篇 |
1975年 | 241篇 |
1974年 | 230篇 |
1973年 | 216篇 |
1972年 | 178篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
This article reports on the latest in a series of international comparisons of management practices and performance outcomes of industries in various countries. Here, it is the service industries in the UK and the US which come under the microscope. Among the companies surveyed, there were more world-class performers in the US than the UK, but also more low performers. The concluding part of the article is diagnostic – the authors also suggest measures which could improve performance. 相似文献
73.
74.
Willem C. Boeschoten 《De Economist》1994,142(3):341-344
Conclusion The article provides a contribution to the discussion on the net foreign assets of the commerical banks, by drawing renewed attention to the possible passivity of the banking sector, which has gained topicality with the striking developments of 1989. Indeed, the banking sector may be considerably more reactive in regards to net foreign assets formation than has been assumed by various authors and in macroeconometric models on the basis of portfolio optimizing behaviour. However, due to the above-mentioned methodological and empirical shortcomings, Bakkers's study certainly does not provide the final answer to this question. 相似文献
75.
The development of a waste discharge charge system (WDCS) in South Africa has been proposed to promote waste reduction and water conservation. The WDCS is based on the polluter pays principle and is designed such that the management of waste discharges achieves resource quality objectives (RQOs) at the minimum total cost to the catchment. Two charges are distinguished: first a charge for optimising use of the resource (incentive charge); and secondly, a charge for development and operation of mitigation measures in the resource (mitigation charge). The WDCS is applied to both point sources and non-point sources (NPS) of contamination. In the inclusion of NPS, the charge system distinguishes between registered and non-registered NPS, with the charge applied to the former group only, in the first instance. This paper introduces the WDCS by describing the principles and the theoretical basis of the WDCS, highlighting the link to RQOs as the benchmark of acceptable externalities. The paper explores the inclusion of NPS in the WDCS, describing: first, the principles of NPS inclusion in the WDCS; secondly, the types of NPS included in the present version of the WDCS; thirdly, the methodology for charge estimation; and finally, non-registered NPS and their potential inclusion in future editions of the WDCS. The paper concludes with remarks and challenges facing the first edition of the WDCS. 相似文献
76.
The aim of this article is to illustrate a framework for flood risk mapping at pan-European scale produced by the Weather-Driven Natural Hazards (WDNH) action of the EC-JRC-IES. Early results are presented in the form of flood risk index maps. We assess several flood risk factors that contribute to the occurrence of flood disasters. Among the causal factors of a flood disaster one is triggering a natural event in the form of extreme precipitation and consequently extreme river discharge and extreme flood water levels. The threatening natural event represents the hazard component in our assessment. Furthermore exposure and vulnerability are anthropogenic factors that contribute also to flood risk. In the proposed approach, flood risk is considered on the light of exposure, vulnerability and hazard. We use a methodology with a marked territorial approach for the assessment of the flood risk. Hence, based on mathematical calculations, risk is the product of hazard, exposure and vulnerability. Improvements on datasets availability and spatial scale are foreseen in the next phases of this study. This study is also a contribution to the discussion about the need for communication tools between the natural hazard scientific community and the political and decision making players in this field. 相似文献
77.
New climate change scenarios for the Netherlands. 总被引:4,自引:0,他引:4
B van den Hurk A K Tank G Lenderink A van Ulden G J van Oldenborgh C Katsman H van den Brink F Keller J Bessembinder G Burgers G Komen W Hazeleger S Drijfhout 《Water science and technology》2007,56(4):27-33
A new set of climate change scenarios for 2050 for the Netherlands was produced recently. The scenarios span a wide range of possible future climate conditions, and include climate variables that are of interest to a broad user community. The scenario values are constructed by combining output from an ensemble of recent General Climate Model (GCM) simulations, Regional Climate Model (RCM) output, meteorological observations and a touch of expert judgment. For temperature, precipitation, potential evaporation and wind four scenarios are constructed, encompassing ranges of both global mean temperature rise in 2050 and the strength of the response of the dominant atmospheric circulation in the area of interest to global warming. For this particular area, wintertime precipitation is seen to increase between 3.5 and 7% per degree global warming, but mean summertime precipitation shows opposite signs depending on the assumed response of the circulation regime. Annual maximum daily mean wind speed shows small changes compared to the observed (natural) variability of this variable. Sea level rise in the North Sea in 2100 ranges between 35 and 85 cm. Preliminary assessment of the impact of the new scenarios on water management and coastal defence policies indicate that particularly dry summer scenarios and increased intensity of extreme daily precipitation deserves additional attention in the near future. 相似文献
78.
S. M. Nikonov I. V. Elkin I. A. Lipatov A. V. Basov A. V. Kapustin A. A. Rovnov 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2007,41(6):351-354
Results of experiments conducted on a large-scale integral PSB-VVéR bench and directed toward investigation of the performance
of new passive safety systems for nuclear plants with a water-cooled power reactor, an additional system for passive flooding
of the active zone, and a system for the passive removal of heat from steam generators are presented.
__________
Translated from élektricheskie Stantsii, No. 9, September 2007, pp. 7–10. 相似文献
79.
A three-stage study has been carried out with rainbow trout (Oncorhyncus mykiss) to develop analytical approaches which can provide a fingerprint for tainting by oil sands chemicals from process-affected waters and natural sources. The objective was to find a simpler alternative to sensory evaluation. In the first stage, a set of seven test compounds was added to fish tissue which was analysed by headspace and solvent (dichloromethane, DCM) extraction followed by gas chromatography-mass spectrometry (GC-MS). In the second stage, fingerlings (5-20 g) were exposed for 96 hours to the test compound mixture at 1.0 and 0.5 times the estimated tainting threshold concentrations. In the final stage, fingerlings were exposed for 96 hours to an oil sands process water at 5, 10, 20 and 50% concentrations in clean water. None of the test compounds was identified in DCM extracts of tissue from exposed fish. Two long-chain aldehydes, hexadecanal and 9-octadecenal, were tentatively identified in these extracts by matching of mass spectra with library spectra. 相似文献
80.
This study reports on a multivariate analysis of the moving bed biofilm reactor (MBBR) wastewater treatment system at a Canadian pulp mill. The modelling approach involved a data overview by principal component analysis (PCA) followed by partial least squares (PLS) modelling with the objective of explaining and predicting changes in the BOD output of the reactor. Over two years of data with 87 process measurements were used to build the models. Variables were collected from the MBBR control scheme as well as upstream in the bleach plant and in digestion. To account for process dynamics, a variable lagging approach was used for variables with significant temporal correlations. It was found that wood type pulped at the mill was a significant variable governing reactor performance. Other important variables included flow parameters, faults in the temperature or pH control of the reactor, and some potential indirect indicators of biomass activity (residual nitrogen and pH out). The most predictive model was found to have an RMSEP value of 606 kgBOD/d, representing a 14.5% average error. This was a good fit, given the measurement error of the BOD test. Overall, the statistical approach was effective in describing and predicting MBBR treatment performance. 相似文献