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   34718篇
  免费   345篇
  国内免费   226篇
安全科学   879篇
废物处理   1432篇
环保管理   4316篇
综合类   7891篇
基础理论   8631篇
环境理论   12篇
污染及防治   8609篇
评价与监测   1979篇
社会与环境   1356篇
灾害及防治   184篇
  2018年   409篇
  2017年   413篇
  2016年   636篇
  2015年   479篇
  2014年   732篇
  2013年   2524篇
  2012年   878篇
  2011年   1248篇
  2010年   1070篇
  2009年   1114篇
  2008年   1301篇
  2007年   1339篇
  2006年   1201篇
  2005年   1044篇
  2004年   1056篇
  2003年   992篇
  2002年   969篇
  2001年   1276篇
  2000年   897篇
  1999年   552篇
  1998年   422篇
  1997年   438篇
  1996年   432篇
  1995年   510篇
  1994年   493篇
  1993年   452篇
  1992年   450篇
  1991年   446篇
  1990年   487篇
  1989年   461篇
  1988年   396篇
  1987年   365篇
  1986年   362篇
  1985年   346篇
  1984年   415篇
  1983年   371篇
  1982年   421篇
  1981年   382篇
  1980年   321篇
  1979年   346篇
  1978年   298篇
  1977年   262篇
  1976年   243篇
  1975年   246篇
  1974年   270篇
  1973年   285篇
  1972年   254篇
  1971年   250篇
  1968年   231篇
  1967年   261篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
391.
Environmental Science and Pollution Research - Hydroxyurea (HDU), a class of antineoplastic drugs, has a powerful efficacy in the treatment of several types of malignancies. However, it has...  相似文献   
392.
393.
394.
395.
A study of the effects of different XAD-resins, bed volume, flow rate, pH and type of eluent on the extraction of organic mutagens from surface water is presented. XAD-4/8 is as effective as XAD-2 in concentrating organic mutagens from surface water and dimethylsulfoxide (DMSO) is as efficient as acetone in eluting the adsorbed organic mutagens. The latter allows direct testing up to 0.5 ml of DMSO concentrate in the Ames test. Variation of the pH of the water after passing the XAD-4/8, followed by readsorption, shows that the majority of the mutagenic activity due to dissolved organics is adsorbed at neutral pH. Only a minor fraction is readsorbed at pH 3. Further a XAD-4/8 concentrate and a similar concentrate prepared by freeze drying gives similar mutagenic activity. This indicates that many of the organic mutagens are recovered in the XAD-4/8 concentrate.It is concluded that adsorption on XAD-4/8, followed by direct testing of the DMSO eluates in the Ames test, presents a rapid and relatively simple way to detect low concentrations of organic mutagens in surface water. The general suitability of the method is shown for different types of surface water.  相似文献   
396.
397.
398.
Seasonal changes in structure of a rocky intertidal community affected by sewage pollution at Quequén (Argentina) were studied over a period of 2 years. Most species showed a decrease in cover values in the polluted area. On the other hand, a small proportion of organisms favoured by organic enrichment predominated around the outfall during the period of study. Community structure was not significantly altered by frosts or windstorms. Desiccation is identified as the main physical stress. A combination of late spring high temperatures with extreme midday low-tides caused by northerly winds was responsible for heavy losses in dominant algae. Major seasonal changes in community structure were primarily due to variations in area covered by the chlorophyte Ulva lactuca, and crusts of blue-green algae and diatoms in the vicinity of the outfall. Highest diversity values were attained during either late winter or spring, due to increased abundances of several seasonal algae. Abundance of the dominant organism, the bivalve Brachidontes rodriguezi, remained stable, showing only slight, non-seasonal, changes. Since the absence of B. rodriguezi is an indication of heavy pollution, temporal stability of this species suggests that the intensity of sewage discharges did not vary over the period of study.  相似文献   
399.
Newark Bay, New Jersey, is particularly vulnerable to ecological damage from petroleum and chemical spills, as a result of the enclosed nature and shallow depth of the bay, the high frequency of shipping traffic, and the numerous chemical and petroleum transfer terminals located alongs its shores. To evaluate the potential impacts to the natural resources of this coastal estuarine ecosystem, chemical and petroleum accidents reported to the US Coast Guard (USCG) between 1982 and 1991 were compiled to determine the frequency and volume of these incidents in Newark Bay and in each of its major tributaries. Records obtained from the USCG National Response Center's computerized database indicated that more than 1453 accidental incidents, resulting in the release of more than 18 million US gallons of hazardous materials and petroleum products, occurred throughout Newark Bay during this period of time. The bulk of the materials released to the aquatic environment consisted of petroleum products, specifically No. 6 Fuel Oil (103 spills, 12 829 272 US gal) and gasoline (207 spills, 48 816 US gal). The majority of the reported incidents occurred in the Arthur Kill and its tributaries, as well as in the Kill Van Kull and the Passaic River. The results of this study indicated that the accidental discharge of petroleum and hazardous chemicals represents a significant source of chemical pollution in Newark Bay. Based on the frequency of spills and the volume of materials released to the aquatic environment, it is likely that these events are having a deleterious effect on the Newark Bay ecosystem.  相似文献   
400.
To study problems associated with pesticide container disposal, a small vegetable production area in southwestern Ontario, the Thedford Marsh, was selected as the site for a model study. A container collection system was organized during the 1981 growing season, with collections being made from the ca. 50 growers on the marsh twice each month. In addition to the regular collection program a cleanup service for empty pesticide containers stored on farms or discarded on public lands also was initiated. More than 3600 containers were collected and disposed of at an authorized landfill site. Ca. 2/3 were herbicide containers, ca. 1/4 were insecticide containers, and 3% were fungicide containers. Unrinsed containers contained as much as 5 1/2% of the original contents with an average of 1%. Containers rinsed by the triple rinse method or using rinsing devices (E-Z Rinse, JET Rinse) generally contained less than 0.1% of the original content. Some formulations presented rinsing problems due to settling and caking. The results indicated that, while unacceptable quantities of pesticide residues remain in unrinsed containers, most rinsed pesticide containers will be acceptable for disposal at municipal sanitary landfill sites.  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