首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   31013篇
  免费   485篇
  国内免费   1371篇
安全科学   950篇
废物处理   1132篇
环保管理   3862篇
综合类   9550篇
基础理论   6753篇
环境理论   10篇
污染及防治   7782篇
评价与监测   1495篇
社会与环境   1066篇
灾害及防治   269篇
  2022年   350篇
  2021年   339篇
  2020年   259篇
  2019年   258篇
  2018年   458篇
  2017年   459篇
  2016年   609篇
  2015年   528篇
  2014年   773篇
  2013年   2309篇
  2012年   905篇
  2011年   1195篇
  2010年   946篇
  2009年   1074篇
  2008年   1177篇
  2007年   1149篇
  2006年   1072篇
  2005年   885篇
  2004年   864篇
  2003年   885篇
  2002年   775篇
  2001年   1052篇
  2000年   765篇
  1999年   540篇
  1998年   419篇
  1997年   382篇
  1996年   423篇
  1995年   433篇
  1994年   444篇
  1993年   390篇
  1992年   419篇
  1991年   379篇
  1990年   412篇
  1989年   401篇
  1988年   326篇
  1987年   320篇
  1986年   295篇
  1985年   308篇
  1984年   317篇
  1983年   309篇
  1982年   321篇
  1981年   337篇
  1980年   286篇
  1979年   294篇
  1978年   255篇
  1977年   230篇
  1976年   247篇
  1974年   260篇
  1973年   238篇
  1967年   260篇
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
21.
22.
23.
Energy efficiency is often stated to be the most cost-effective measure for satisfying our energy demand with minimal environmental damage. However, the potential energy savings attainable in 'the real world' are frequently overestimated, as is shown in an industrial case study of the glass industry. Nevertheless, there are significant energy savings to be realized, and the role of new technologies in this is important. However, the key to the effective use of new technology for improved energy efficiency is good management and. for best effect, it must be integrated into the normal resource management activities of a company.  相似文献   
24.
防灾预案研究   总被引:1,自引:0,他引:1  
陆立德  徐旭初 《灾害学》1992,7(2):17-20
本文提出了防御灾害预案的五要素和逻辑结构,进而讨论了防灾预案的优化准则、制定程序等问题。  相似文献   
25.
This paper demonstrates the potential for induced preference experiments to test previously unverified explanations of observed behavior in contingent valuation surveys. The NOAA Panel on Contingent Valuation called for experimental evidence on potential biases in the double referendum format. We test Carson, Groves, and Machina's (Incentives and informational properties of preference questions, Plenary address to the European Association of Resource and Environmental Economists, Oslo, Norway, June 1999) simple cost uncertainty and weighted averaging explanations of inconsistent responses to follow-up offers in such double referenda against a baseline of certainty and truthful preference revelation. The results find evidence to support the Weighted Average hypothesis. Results regarding the cost uncertainty hypothesis are more ambiguous and merit further investigation.  相似文献   
26.
ABSTRACT: Two dynamic programming models — one deterministic and one stochastic — that may be used to generate reservoir operating rules are compared. The deterministic model (DPR) consists of an algorithm that cycles through three components: a dynamic program, a regression analysis, and a simulation. In this model, the correlation between the general operating rules, defined by the regression analysis and evaluated in the simulation, and the optimal deterministic operation defined by the dynamic program is increased through an iterative process. The stochastic dynamic program (SDP) describes streamflows with a discrete lag-one Markov process. To test the usefulness of both models in generating reservoir operating rules, real-time reservoir operation simulation models are constructed for three hydrologically different sites. The rules generated by DPR and SDP are then applied in the operation simulation model and their performance is evaluated. For the test cases, the DPR generated rules are more effective in the operation of medium to very large reservoirs and the SDP generated rules are more effective for the operation of small reservoirs.  相似文献   
27.
A significant positive correlation between the lipid content of eight fish species and their bioconcentration factor (BCF) of 1,2,4-trichlorobenzene is demonstrated. The log BCF value on a lipid basis is in good agreement with the log n-octanol/water partition coefficient.  相似文献   
28.
W. F. Wood 《Marine Biology》1987,96(1):143-150
During spring and summer, 1982–1986, experiments were carried out near Marmion Reef, Western Australia. In summer, nearly 30% of the surface solar ultraviolet radiation (280 to 400 nm) penetrates offshore waters to 5 m depth. Experimental removal of the mature Ecklonia radiata kelp canopy in summer results in tissue damage, photopigment destruction, reduced growth, and low survivorship of subcanopy kelp sporophytes. These effects do not occur with canopy removal in winter. Laboratory experiments revealed that the UV component of radiation, rather than intense photosynthetically active radiation, was responsible for the inhibition of growth and photodamage. UV radiation probably affects survival of the settlement stages of E. radiata sporophytes, thus excluding them from otherwise suitable substrata in shallow waters. UV radiation is implicated in the reduction of canopy productivity in summer.  相似文献   
29.
30.
We report three siblings from consecutive pregnancies affected with restrictive dermopathy (RD). During the second pregnancy, fetal behavioural development and growth were studied extensively using ultrasound at 1–4 week intervals. Dramatic and sudden changes occurred in fetal body movements and growth but not until the end of the second trimester of pregnancy. Prominent at that time were prolonged periods of fetal quiescence and very low heart rate variability, together with abnormally executed body movements of short duration. Retarded femoral development and jerky abrupt fetal body movements (abnormal movement quality) were already present in the early second trimester of pregnancy. Facial anomalies emerged despite the presence of fetal mouth movements. The clinical features of RD were only partly explained by present knowledge of skin development and the fetal akinesia deformation sequence hypothesis. Quantitative assessment of fetal movements proved to be a poor early marker for antenatal diagnosis of this disorder. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号