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   249434篇
  免费   16690篇
  国内免费   35653篇
安全科学   23290篇
废物处理   11556篇
环保管理   28814篇
综合类   102049篇
基础理论   47360篇
环境理论   211篇
污染及防治   50369篇
评价与监测   16413篇
社会与环境   14798篇
灾害及防治   6917篇
  2024年   515篇
  2023年   3280篇
  2022年   8902篇
  2021年   9012篇
  2020年   8637篇
  2019年   6774篇
  2018年   7857篇
  2017年   9216篇
  2016年   9150篇
  2015年   8893篇
  2014年   11273篇
  2013年   20803篇
  2012年   16003篇
  2011年   17924篇
  2010年   15691篇
  2009年   15463篇
  2008年   15852篇
  2007年   15556篇
  2006年   14473篇
  2005年   11189篇
  2004年   8575篇
  2003年   7582篇
  2002年   6684篇
  2001年   6154篇
  2000年   5224篇
  1999年   3571篇
  1998年   2418篇
  1997年   2207篇
  1996年   2223篇
  1995年   2293篇
  1994年   2029篇
  1993年   1494篇
  1992年   1508篇
  1991年   1367篇
  1990年   1253篇
  1989年   1145篇
  1988年   1013篇
  1987年   906篇
  1986年   860篇
  1985年   870篇
  1984年   895篇
  1983年   825篇
  1982年   918篇
  1981年   817篇
  1980年   627篇
  1979年   686篇
  1978年   585篇
  1977年   513篇
  1975年   467篇
  1974年   461篇
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
141.
Environmental Science and Pollution Research - The effects of diazinon (DZN), an organophosphate pesticide, on lipid profiles have been extensively reported. However, controversy on this issue...  相似文献   
142.
Environmental Fluid Mechanics - A 3D dry deposition scheme for particulate matter (PM) is presented as a Free-Libre and Open-Source Software (FOSS) library, DePaSITIA (RSE SpA). This combines some...  相似文献   
143.
以江苏历史文献记录的洪涝灾害为研究对象,分析历史时期江苏地区洪涝灾害发生的时空差异性特征,探讨影响洪涝灾害时空差异性的原因。时间尺度上,历史时期江苏地区洪涝灾害明清时期多发,集中于夏秋季节,其影响因素有长时间异常降水、风暴潮以及厄尔尼诺事件等。空间尺度上,洪涝灾害多发生于太湖平原、里下河平原及沿江地区。唐宋时期,太湖平原、沿江地区是江苏省洪涝灾害最为集中的地区,明代以降苏北平原洪涝灾害更为集中,原因应该是宋代太湖平原人口激增,涸湖造田破坏了太湖东泄水道,明清后泄洪能力得到提升,长江口的演变则使得沿江地区潮灾逐渐减少,而里下河平原因为黄河夺淮入海,导致泥沙沉降,水流不畅,成为洪涝走廊。  相似文献   
144.
This study evaluated the hydrolysis and photolysis kinetics of pyraclostrobin in an aqueous solution using ultra-high-performance liquid chromatography–photodiode array detection and identified the resulting metabolites of pyraclostrobin by hydrolysis and photolysis in paddy water using high-resolution mass spectrometry coupled with liquid chromatography. The effect of solution pH, metal ions and surfactants on the hydrolysis of pyraclostrobin was explored. The hydrolysis half-lives of pyraclostrobin were 23.1–115.5?days and were stable in buffer solution at pH 5.0. The degradation rate of pyraclostrobin in an aqueous solution under sunlight was slower than that under UV photolysis reaction. The half-lives of pyraclostrobin in a buffer solution at pH 5.0, 7.0, 9.0 and in paddy water were less than 12?h under the two light irradiation types. The metabolites of the two processes were identified and compared to further understand the mechanisms underlying hydrolysis and photolysis of pyraclostrobin in natural water. The extracted ions obtained from paddy water were automatically annotated by Compound Discoverer software with manual confirmation of their fragments. Two metabolites were detected and identified in the pyraclostrobin hydrolysis, whereas three metabolites were detected and identified in the photolysis in paddy water.  相似文献   
145.
146.
147.
148.
149.
Wildlife provides food, medicine, clothing, and other necessities for humans, but overexploitation can disrupt the sustainability of wildlife resources and severely threaten global biodiversity. Understanding the characteristics of consumer behavior is helpful for wildlife managers and policy makers, but the traditional survey methods are laborious and time-consuming. In contrast, culturomics may more efficiently identify the features of wildlife consumption. As a case study of the culturomics approach, we examined tiger bone wine consumption in China based on social media and Baidu search engine data. Tiger bone wine is one of the most purchased tiger products; its consumption is closely related to tiger poaching, which greatly threatens wild tiger survival. We searched a popular social media website for the term “tiger bone wine” and focused on posts that were originally created from 1 January 2012 to 31 December 2018. We filtered and classified posts related to the purchase, sale, or consumption of tiger bone wine and extracted information on providers, consumption motivations, year of production, and place of origin of the tiger bone wines based on the texts and photos of these posts. We found 756 posts related to tiger bone wine consumption, 113 of which mentioned providers of tiger bone wine, including friends (53%), elder relatives (37%), peer relatives (7%), and others (3%). Out of the 756 posts, 266 indicated the motivations of tiger bone wine consumption. Tiger bone wines were consumed as a tonic (34%), medicine (23%), game product (30%), and a symbol of wealth (28%). Some posts indicated ≥2 consumption motivations. These findings were consistent with the search queries from Baidu index. Such information could help develop targeted strategies for tiger conservation. The culturomics approach illustrated by our study is a rapid and cost-efficient way to characterize wildlife consumption.  相似文献   
150.
为全面了解北京城市湿地的现状及近年来的动态变化情况,利用高分辨率卫星遥感数据,综合运用GIS技术与景观生态学方法,定量分析了北京市6环内的湿地空间格局。结果表明,北京6环内城市湿地以河流湿地和湖库湿地为主;2016—2018年间湿地面积有所下降,2年间减少了126.58 hm2,主要转化为草地,少量转化为建设用地和林地;由于城市外围的开发建设强度较大,5-6环湿地被侵占面积相对较大,而4环内湿地面积的波动较小;2016—2018年,北京城市湿地的斑块密度增加,平均斑块面积有所减小,表明湿地斑块随时间变化呈破碎化的趋势,且从城市中心向城市边缘,湿地斑块的破碎化程度增强。  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