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   28616篇
  免费   264篇
  国内免费   223篇
安全科学   754篇
废物处理   1221篇
环保管理   3701篇
综合类   4995篇
基础理论   7169篇
环境理论   14篇
污染及防治   7742篇
评价与监测   1832篇
社会与环境   1515篇
灾害及防治   160篇
  2022年   269篇
  2021年   329篇
  2020年   197篇
  2019年   253篇
  2018年   457篇
  2017年   444篇
  2016年   699篇
  2015年   475篇
  2014年   739篇
  2013年   2234篇
  2012年   902篇
  2011年   1194篇
  2010年   957篇
  2009年   955篇
  2008年   1184篇
  2007年   1266篇
  2006年   1130篇
  2005年   911篇
  2004年   972篇
  2003年   881篇
  2002年   827篇
  2001年   1070篇
  2000年   749篇
  1999年   462篇
  1998年   344篇
  1997年   319篇
  1996年   327篇
  1995年   390篇
  1994年   400篇
  1993年   326篇
  1992年   345篇
  1991年   349篇
  1990年   356篇
  1989年   347篇
  1988年   302篇
  1987年   267篇
  1986年   228篇
  1985年   250篇
  1984年   286篇
  1983年   284篇
  1982年   281篇
  1981年   256篇
  1980年   219篇
  1979年   240篇
  1978年   198篇
  1977年   186篇
  1975年   188篇
  1974年   196篇
  1973年   164篇
  1972年   187篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
Dedicated to Prof. H. Autrum on the occasion of his 85th birthday.  相似文献   
95.
96.
Long-term copper smelting in the Anaconda and Deer Lodge Valley area of Montana has resulted in an extensive area of trace element contamination. Aerial extent of contamination is generally established, but total analysis of soils does not correlate to relative degree of impact on vegetation growth. Three pedons (Beaverell, Cetrack and Judco) were analyzed by routine soil characterization methods, aqua regia microwave digestion, sequential chemical extraction, and X-ray diffraction analysis with the objective of providing a better understanding of chemical forms and potential reactivity of selected trace elements (Cd, Co, Cr, Cu, Hg, Mn, Ni, P, Pb). Surface horizons of soils are more acidic than subsoils, with pH for all horizons ranging from 4.0 to 8.7. Beaverell is the most contaminated in the upper 20 cm with the sum of total extractable (SUMTE) trace elements by microwave digestion ranging from 1836 to 3605 mg kg−1, largest H2O-soluble (WS) and exchangeable (EX) fractions (e.g. 1.6 and 9.3%, respectively), and smallest residual (RES) fraction (e.g. 14.3%). Cetrack has greater SUMTE elements than Judco, though a lower WS+EX fraction due to the effects of alkaline pH, carbonates and high P. Oxide (OX), organic matter/sulfide (OM/S), and RES fractions predominate over WS, EX, and specially-sorbed/carbonate-bound fractions (SS/CAR) for all horizons. Copper, Zn, Pb and Cd are elevated in surface over subsurface horizons in these latter fractions, indicating these elements were anthropogenic additions. X-ray data indicate that Pb, Cu, Cr and Cd partially exists as both OX and sulfide mineral forms.  相似文献   
97.
Microorganisms are able to synthesize three different polyamides by enzymatic processes independently from ribosomal protein biosynthesis: poly(gamma-D-glutamic acid), poly(epsilon-L-lysine) and multi-L-arginyl-poly(L-aspartic acid) which is also referred to as cyanophycin. These polyamides, which occur mainly in Bacillus spp. (and only a few other eubacteria and the nematocysts of Cnidaria, in Streptomyces albulus or in cyanobacteria, respectively), have recently attracted considerable interest of the chemical industry and may be suitable for various applications. This review summarizes our current knowledge on the occurrence, biosynthesis, physiological functions, and biodegradation as well as on the properties and putative applications of these polyamides. Emphasis is placed on the enzymology of the polymerization and on the genes encoding the polymerizing enzymes, which have only recently become available for cyanophycin synthetases. Prospects for novel production processes. in particular for cyanophycin, are also presented.  相似文献   
98.
99.
Intergeneric transmission of a marine plant DNA virus   总被引:1,自引:0,他引:1  
  相似文献   
100.
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