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   33412篇
  免费   312篇
  国内免费   228篇
安全科学   771篇
废物处理   1743篇
环保管理   5011篇
综合类   3934篇
基础理论   9416篇
环境理论   12篇
污染及防治   7954篇
评价与监测   2480篇
社会与环境   2448篇
灾害及防治   183篇
  2023年   134篇
  2022年   183篇
  2021年   212篇
  2020年   159篇
  2019年   214篇
  2018年   1842篇
  2017年   1755篇
  2016年   1743篇
  2015年   578篇
  2014年   691篇
  2013年   1999篇
  2012年   1267篇
  2011年   2409篇
  2010年   1609篇
  2009年   1580篇
  2008年   2019篇
  2007年   2444篇
  2006年   993篇
  2005年   937篇
  2004年   888篇
  2003年   900篇
  2002年   928篇
  2001年   873篇
  2000年   676篇
  1999年   397篇
  1998年   332篇
  1997年   282篇
  1996年   339篇
  1995年   360篇
  1994年   327篇
  1993年   298篇
  1992年   268篇
  1991年   238篇
  1990年   256篇
  1989年   235篇
  1988年   217篇
  1987年   220篇
  1986年   195篇
  1985年   190篇
  1984年   257篇
  1983年   235篇
  1982年   222篇
  1981年   213篇
  1980年   169篇
  1979年   181篇
  1978年   138篇
  1977年   124篇
  1976年   104篇
  1975年   109篇
  1972年   108篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
In a 1981 survey of 436 Florida citrus growers, 27 pesticide related poisoning incidents were reported that were to have taken place within one year of the interview date. From these reports it is possible to estimate that there are 376 citrus fieldworker related poisonings per year in Florida. This number of estimated poisonings may be developed into an incidence rate of 113 fieldworker poisonings per 10,000 fieldworkers.  相似文献   
94.
95.
Four microbial isolates, OP2, OP3, OP6, and OP7, of earthworm casts ofPontoscolex corethrurus were found to be acid tolerant actinomycetes and efficient rock phosphate (RP) solubilizers that could grow fast on NH4Cl-enriched or N-free carboxymethyl cellulose or glucose as sole carbon source. CMC (carboxymethyl cellulose) induced production of extracellular cellulase enzyme and the production of reducing sugar in all the isolates. RP solubilizing power was observed to be inversely related to glucose consumption. The most efficient RP solubilizer was found to consume the least glucose. Growth was faster on cellulose than on glucose media. N-free CMC induced greater glucose production than NH4Cl-enriched CMC medium. Both CMC and glucose media were acidified by all the isolates, however, RP solubilizing power decreased with acidification. Solubilization power was greatest with isolate OP7, which also produced the greatest amount of reducing sugar per gram CMC. Both RP solubilizing power and the cellulolytic efficiency varied among isolates. A minimum of 631 μg P/0.1 g RP and a maximum of 951.4 μg P/0.1 g RP was recorded.  相似文献   
96.
97.
98.
In this article the authors assert that successful long-term pollution prevention will require changes in the culture and business practices of an organization such that the term “pollution prevention” eventually becomes obsolete. They envision firms evolving to a point where actions that today are referred to as pollution prevention will simply be part of standard business practices and thoroughly embedded in the firms' culture. Although pollution prevention projects and programs need to be highly visible at the outset to communicate throughout the organization and to demonstrate the benefits that can be gained, companies should adopt a long-term strategy aimed at making fundamental changes in the way they do business, rather than relying solely on piecemeal projects and special plans or programs. Such evolution of the firm will maximize the chances of meeting the dual challenges of business competitiveness and environmental stewardship. This article presents a vision for integrating environmental performance with business objectives and suggests practical steps to begin moving toward that vision.  相似文献   
99.
The presence of maternal cells in fetal samples constitutes a serious potential source for prenatal misdiagnosis. Here we present our approach for detecting maternal cell contamination (MCC) at prenatal diagnosis for eight monogenic disorders (autosomal recessive: β-thalassaemia, sickle-cell anaemia, cystic fibrosis, prelingual deafness; autosomal dominant: achondroplasia, Huntington disease, myotonic dystrophy, neurofibromatosis type I; X-linked: spinobulbar muscular atrophy). Our aim was to apply a simple and low-cost approach, which would easily and accurately provide information on the fetal tissue MCC status. MCC testing was applied to cases of recessive inheritance where the primary mutation screening of the fetus revealed the presence of the maternal mutation, to cases concerning dominant inheritance and to cases of multiple gestation. The potential presence of maternal cells was determined by the amplification of the 3′-HVR/APO B, D1S80, THO1 and VNTRI of vWf polymorphic loci, which have previously demonstrated high heterozygosity in Caucasians. Among 135 prenatal diagnoses, 44 finally needed to be tested for MCC (32.6%). MCC was detected in four cases, where DNA was isolated directly from chorionic villi samples (CVS), and in one case with DNA isolated directly from amniotic fluid (AF). In almost 90% of cases a simple test of one polymorphic locus provided sufficient information about MCC. The choice of the appropriate locus is therefore essential, while the simultaneous screening of both parents provides the means for distinguishing non-informative sites about MCC. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
100.
Indices of abundance and reproduction rate are considered in some groups of aquatic and terrestrial vertebrates from the zones of technogenic disasters. Upon a critical population decline caused by external destructive factors, such as emissions of acute ecotoxicants, the ecophysiological and behavioral compensatory mechanisms are activated, which provide for restoration of the total population size to the optimum within a short period of time. Environmental pollution with substances disturbing the reproductive function has the gravest consequences for animals. In this case, population size may remain fairly high, and, therefore, the effect of enhanced reproduction as a response to population decline does not take place, which eventually leads to a gradual but irreversible destruction of the population. Pathologies of reproduction should be used as a criterion for assessing the state of animals in the zones of technogenic disasters.Translated from Ekologiya, No. 1, 2005, pp. 32–38.Original Russian Text Copyright © 2005 by Shilova, Shatunovskii.  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