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   10443篇
  免费   139篇
  国内免费   102篇
安全科学   311篇
废物处理   478篇
环保管理   1392篇
综合类   1280篇
基础理论   2866篇
环境理论   2篇
污染及防治   2876篇
评价与监测   738篇
社会与环境   683篇
灾害及防治   58篇
  2023年   46篇
  2022年   118篇
  2021年   86篇
  2020年   87篇
  2019年   88篇
  2018年   166篇
  2017年   173篇
  2016年   253篇
  2015年   184篇
  2014年   265篇
  2013年   783篇
  2012年   331篇
  2011年   483篇
  2010年   399篇
  2009年   425篇
  2008年   502篇
  2007年   511篇
  2006年   446篇
  2005年   384篇
  2004年   342篇
  2003年   395篇
  2002年   338篇
  2001年   511篇
  2000年   338篇
  1999年   202篇
  1998年   146篇
  1997年   143篇
  1996年   141篇
  1995年   169篇
  1994年   130篇
  1993年   106篇
  1992年   126篇
  1991年   120篇
  1990年   134篇
  1989年   136篇
  1988年   95篇
  1987年   90篇
  1986年   66篇
  1985年   91篇
  1984年   90篇
  1983年   90篇
  1982年   85篇
  1981年   73篇
  1980年   61篇
  1979年   70篇
  1977年   54篇
  1976年   49篇
  1975年   53篇
  1974年   51篇
  1973年   53篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
91.
92.
Defense Mechanisms of Arthropods, no. 96; no. 95: Eisner et al.: Chemoecology (in press)  相似文献   
93.
Herlitz junctional epidermolysis bullosa (HJEB) is a severe blistering disorder which usually results in death during infancy. We have previously shown that the anchoring filament protein laminin-5 (kalinin/nicein), which mediates keratinocyte attachment and dermal–epidermal cohesion, is abnormally expressed in individuals with HJEB. Laminin-5 was detected by Western blot analysis in amniotic fluid from 44 consecutive normal secondtrimester control pregnancies, but was undetectable in second-trimester amniotic fluid from four pregnancies with fetuses affected by HJEB. In one case of severe non-Herlitz JEB, laminin-5 was detected in both amniotic fluid and skin. In human amniotic fluid, the laminin-5 a3 subunit was processed to a major 165 kD species and a minor 145 kD species and the β2 subunit was partially processed to 105 kD. Although laminin-5 was covalently associated with laminin-6 (K-laminin) in amniotic membrane, no covalent interaction was detected in amniotic fluid. Laminin-5 from amniotic fluid strongly supported keratinocyte attachment. These results suggest that Western blot analysis of second-trimester amniotic fluid is useful in determining the prenatal diagnosis of HJEB and that laminin-5 may serve a physiologically important function in amniotic fluid.  相似文献   
94.
The prenatal diagnosis of The Turner Syndrome is described at a menstrual age of 12 weeks. Detection of cystic hygroma was followed by vaginal chorionic villous sampling (CVS) which revealed a 45,X karyotype. Early documentation of fetal karyotype in the presence of a cystic hygroma is essential for accurate diagnosis and genetic counselling.  相似文献   
95.
Plasticity of honeybee castes   总被引:1,自引:0,他引:1  
  相似文献   
96.
The invertebrate neuromodulator octopamine is known to be involved in bees' associative learning, enhancing the responsiveness of a bee to a conditioned stimulus. In this study, we tested the effect of octopamine on the choice behavior of free-flying bumblebees using a two-phase experiment in an array of artificial flowers. During the first phase of the experiment, the bee was allowed to collect octopamine-laden sugar water from two types of equally rewarding flowers (yellow versus blue). In the second phase, one type of flower was set to be unrewarding. The behavior of the bee (proportion of visits to the unrewarding flowers) over the two phases was fitted to a sigmoid regression model. Our results show that octopamine had no significant effect on the bees' equilibrium choice or on the overall rate of the behavioral change in response to the change in reward. Rather, octopamine significantly affected the time interval between the change in reward status and the initiation of behavioral change in the bee.  相似文献   
97.
We have investigated the ability of high-resolution proton NMR spectroscopy to provide a biochemical constituent screening of human amniotic fluid (AF). Proton NMR spectra were obtained at 300 MHz on AF from patients undergoing amniocentesis in the mid-trimester. Only AF from normal pregnancies (normal fetal karyotype, normal a-fetoprotein levels, normal birth outcome) was used in this study. The AF supernatant was lyophilized and resuspended in deuterated water containing 0.1 mm phosphate buffer and 6.02 mm disodium maleate. Identification of low molecular weight compounds was confirmed by two-dimensional NMR spectra (primarily correlated spectroscopy, or COSY) and standard addition techniques. A broad profile of compounds were ‘NMR visible’ in a single proton spectrum, including creatinine, glucose, organic acids (acetate, citrate, and lactate) and several amino acids (alanine, histidine, leucine, phenylalanine, tyrosine and valine). The proton spectrum was unaffected by prior freezing/thawing of AF samples. We were able to quantify compounds by comparison with an added concentration standard (maleate) at concentrations as low as 30 μm. Good agreement with literature values based on other analytical techniques was obtained.  相似文献   
98.
99.
IntroductionSiberiaandtheFarEastaretheoldestandtherichestgold miningareasofRussia .Intensivegold miningherestartedinthebeginningofthe 19thcentury(Vyazelshchikov ,1963) .Forthemostpartgold bearingoresandsandswereprocessedwiththeuseofamalgamationmethodforgolde…  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