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   453篇
  免费   61篇
  国内免费   314篇
安全科学   30篇
废物处理   17篇
环保管理   23篇
综合类   539篇
基础理论   105篇
环境理论   1篇
污染及防治   90篇
评价与监测   7篇
社会与环境   8篇
灾害及防治   8篇
  2024年   1篇
  2023年   10篇
  2022年   13篇
  2021年   22篇
  2020年   30篇
  2019年   32篇
  2018年   24篇
  2017年   27篇
  2016年   31篇
  2015年   30篇
  2014年   30篇
  2013年   48篇
  2012年   41篇
  2011年   54篇
  2010年   42篇
  2009年   37篇
  2008年   23篇
  2007年   52篇
  2006年   56篇
  2005年   34篇
  2004年   27篇
  2003年   23篇
  2002年   26篇
  2001年   23篇
  2000年   15篇
  1999年   14篇
  1998年   9篇
  1997年   7篇
  1996年   9篇
  1995年   7篇
  1994年   12篇
  1993年   1篇
  1992年   3篇
  1991年   8篇
  1989年   2篇
  1988年   2篇
  1987年   1篇
  1980年   1篇
  1970年   1篇
排序方式: 共有828条查询结果,搜索用时 15 毫秒
41.
A cap‐and‐trade system for managing whale harvests represents a potentially useful approach to resolve the current gridlock in international whale management. The establishment of whale permit markets, open to both whalers and conservationists, could reveal the strength of conservation demand, about which little is known. This lack of knowledge makes it difficult to predict the outcome of a hypothetical whale permit market. We developed a bioeconomic model to evaluate the influence of economic uncertainty about demand for whale conservation or harvest. We used simulations over a wide range of parameterizations of whaling and conservation demands to examine the potential ecological consequences of the establishment of a whale permit market in Norwegian waters under bounded (but substantial) economic uncertainty. Uncertainty variables were slope of whaling and conservation demand, participation level of conservationists and their willingness to pay for whale conservation, and functional forms of demand, including linear, quadratic, and log‐linear forms. A whale‐conservation market had the potential to yield a wide range of conservation and harvest outcomes, the most likely outcomes were those in which conservationists bought all whale permits.  相似文献   
42.
Environmental Ethics is the ethics of how we humans are to relate to each other about the environment we live in. The best way to adjust inevitable differences among us in this respect is by private property. Each person takes the best care of what he owns, and ownership entails the free market, which enables people to make mutually advantageous trades with those who might use it even better. Public regulation, by contrast, becomes management in the interests of the regulators, or of special interests, such as lovers of rare species-not the people they're supposed to be serving.  相似文献   
43.
44.
45.
Originally prenatal diagnosis was confined to the diagnosis of metabolic disorders and depended on assaying enzyme levels in amniotic fluid. With the development of recombinant DNA technology, molecular diagnosis became possible for some genetic conditions late in the 1970s. Here we briefly review the history of molecular prenatal diagnostic testing, using Duchenne muscular dystrophy as an example, and describe how over the last 30 years we have moved from offering testing to a few affected individuals using techniques, such as Southern blotting to identify deletions, to more rapid and accurate PCR-based testing which identifies the precise change in dystrophin for a greater number of families. We discuss the potential for safer, earlier prenatal genetic diagnosis using cell free fetal DNA in maternal blood before concluding by speculating on how more recent techniques, such as next generation sequencing, might further impact on the potential for molecular prenatal testing. Progress is not without its challenges, and as cytogenetics and molecular genetics begin to unite into one, we foresee the main challenge will not be in identifying the genetic change, but rather in interpreting its significance, particularly in the prenatal setting where we frequently have no phenotype on which to base interpretation. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
46.
47.
48.
49.
以库区天然水培养的二形栅藻(Scenedesmus dimorphus)为研究对象,利用大气压强电场电离放电产生羟基自由基(·OH),结合压力溶气气浮前处理工艺处理高藻水.实验结果表明,对于藻密度为65.6×10~4 cells/mL,浊度为10.8NTU,COD_(Mn)为6.74mg/L的高藻水,在总氧化剂TRO浓度为1.03 mg/L时,藻类去除效率达到100%;总细菌,总大肠菌群和大肠埃希氏菌均未检出;出水COD_(Mn)由1.43 mg/L降至1.25mg/L,降低了10%;浊度由0.66NTU降至0.54NTU,降低了12.59在排放高藻水的主管路中·OH杀藻的接触反应时间仅为6s.因此汽浮-·OH强氧化组合工艺可高效快速地处理高藻水,为保障水源水的供水安全探索了一种新的思路.  相似文献   
50.
化能自养细菌对全球CO2固定具有重要的意义.研究了4种典型氢氧化细菌(HOB,分别是Alcaligenes hydrogenophilus DSM 2625、Pelomonas saccharophila DSM 654、Variovorax paradoxus DSM 30034和Acidovorax facilis DSM 649)的固碳特性及其种间差异性,并探究了胞外游离有机碳(EFOC)对不同种类HOB固碳效率差异性的影响.结果表明:①不同HOB自养培养过程中表观固碳量随时间呈显著差异性,其中,DSM 2625生长速度较快,其平均固碳量分别是DSM 654、DSM 649和DSM 30034的6.30、8.76和7.02倍.②不同HOB之间cbbL基因转录量与 表观固碳量的相关系数为0.980 (p<0.05),cbbL基因转录量是造成不同菌种之间表观固碳效率差异的关键因素.③HOB细胞蛋白质含量与cbbL基因丰度和转录量之间也存在显著正相关,相关系数分别为0.999(p<0.01)和0.976(p<0.05),即化能自养细菌CO2同化途径所固定的有机碳进一步参与细胞蛋白质的合成,进而影响其生长速度和表观固碳效率.④HOB在自养培养过程中产生的EFOC对cbbL基因转录效率产生反馈抑制作用,且不同HOB之间,EFOC/TOC比例越低,表观固碳效率越高.  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