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   11778篇
  免费   88篇
  国内免费   92篇
安全科学   303篇
废物处理   513篇
环保管理   1556篇
综合类   2507篇
基础理论   2634篇
环境理论   5篇
污染及防治   3067篇
评价与监测   726篇
社会与环境   581篇
灾害及防治   66篇
  2022年   91篇
  2021年   103篇
  2019年   74篇
  2018年   152篇
  2017年   135篇
  2016年   229篇
  2015年   185篇
  2014年   257篇
  2013年   876篇
  2012年   323篇
  2011年   448篇
  2010年   356篇
  2009年   411篇
  2008年   446篇
  2007年   518篇
  2006年   452篇
  2005年   369篇
  2004年   380篇
  2003年   385篇
  2002年   344篇
  2001年   437篇
  2000年   323篇
  1999年   211篇
  1998年   121篇
  1997年   128篇
  1996年   112篇
  1995年   161篇
  1994年   157篇
  1993年   132篇
  1992年   136篇
  1991年   157篇
  1990年   126篇
  1989年   131篇
  1988年   138篇
  1987年   118篇
  1986年   86篇
  1985年   101篇
  1984年   127篇
  1983年   133篇
  1982年   131篇
  1981年   103篇
  1980年   103篇
  1979年   113篇
  1978年   93篇
  1977年   87篇
  1976年   81篇
  1975年   92篇
  1974年   101篇
  1973年   70篇
  1965年   74篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Codigestion of five wastes and municipal wastewater sludge was evaluated using full-scale testing. Synergistic, antagonistic, and neutral outcomes were observed depending on codigestate identity and concentration, highlighting the value of careful blending. Yeast waste resulted in notable synergism, increasing biogas production by over 50%, whereas aircraft deicing waste resulted in antagonism at high loadings and neutral outcomes at lower loadings. Restaurant waste codigestion resulted in neutral outcomes. The synergisim with yeast codigestates may have resulted from trace nutrients (i.e., iron, nickel, and cobalt) in the wastes that increased microbiological activity. Antagonist outcomes with deicing waste may have been the result of organic overload or inhibitory deicer constituents. Codigestion of wastes at the feed rates investigated was estimated to produce 0.50 ML/d of methane having an energy equivalent of 17 500 MJ/d. This was estimated to reduce net carbon dioxide emissions by 560 tonnes/y.  相似文献   
3.
This work, carried out within the framework of the PRISMA II project, aims at evaluating the effects of the Po River flow on primary productivity, measured by C with in situ sample incubations. A total of four cruises was carried out in late winter and early summer (1996-1998) along transects from the coast offshore. In both seasons, the highest primary productivity was found in the most oligohaline stations. The effects of the Po River inputs were therefore clearly evident in the westernmost area, both in high productivity values and in the shape of productivity profiles. In late winter, extensive blooms of Skeletonema costatum and Pseudo-nitzschia delicatissima resulted in productivity values that were sometimes higher than in early summer. In early summer 1996, greatly reduced river flow clearly influenced productivity which was much lower than in 1997.  相似文献   
4.
The typical parameters of acid precipitation are evaluated in the forest of Vallombrosa (Tuscan Appennines) during the dry period 1988-89. Individual rain events (dry and wet deposition) were sampled in a clearing of the forest and below the canopy of an evergreen tree as well as a deciduous broadleaf tree.

In atmospheric precipitation the pH values usually vary around 4.4, with neutralization in the hot season due to calcareous material from distant sources. Relatively large concentrations of Pb and Cd are found in rain, but only in a small amount in canopy leachate. Aluminium, manganese and iron are more significantly washed off than Pb and Cd.  相似文献   
5.
Three monoclonal antibodies (MAbs) against trophoblast (GB17, GB21, and GB25) and flow cytometry were used to sort trophoblast-like cells (TLCs) from peripheral blood of pregnant women. Sorted TLCs were processed for electron microscopy and fetal DNA amplification of the Y-specific sequences from mothers carrying male fetuses. At the ultra-structural level, most of the nucleated cells had the morphology of leucocytes, suggesting maternal contaminants, and we did not find the characteristic features of the free inter-villous trophoblast cells. Nevertheless, polymerase chain reaction (PCR) analysis showed an amplification of Y-specific sequences in two out of three samples of sorted TLCs. These results suggest that besides the maternal leucocytes, sufficient trophoblast nucleated fetal cells can be obtained using cell enrichment by sorting. This sensitive method holds promise for non-invasive prenatal diagnosis of fetal sex and if sufficient Y(positive) nuclei are found, for the diagnosis of selected numerical chromosome abnormalities.  相似文献   
6.
7.
8.
9.
10.
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