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   3776篇
  免费   85篇
  国内免费   37篇
安全科学   183篇
废物处理   138篇
环保管理   942篇
综合类   364篇
基础理论   945篇
环境理论   3篇
污染及防治   914篇
评价与监测   237篇
社会与环境   148篇
灾害及防治   24篇
  2023年   43篇
  2022年   53篇
  2021年   42篇
  2020年   44篇
  2019年   65篇
  2018年   77篇
  2017年   87篇
  2016年   132篇
  2015年   83篇
  2014年   107篇
  2013年   376篇
  2012年   139篇
  2011年   238篇
  2010年   173篇
  2009年   175篇
  2008年   185篇
  2007年   201篇
  2006年   183篇
  2005年   109篇
  2004年   138篇
  2003年   135篇
  2002年   122篇
  2001年   75篇
  2000年   48篇
  1999年   47篇
  1998年   50篇
  1997年   52篇
  1996年   59篇
  1995年   58篇
  1994年   48篇
  1993年   45篇
  1992年   29篇
  1991年   31篇
  1990年   40篇
  1989年   25篇
  1988年   38篇
  1987年   28篇
  1986年   41篇
  1985年   23篇
  1984年   38篇
  1983年   32篇
  1982年   34篇
  1981年   32篇
  1980年   21篇
  1979年   20篇
  1978年   12篇
  1977年   10篇
  1976年   10篇
  1974年   8篇
  1972年   9篇
排序方式: 共有3898条查询结果,搜索用时 93 毫秒
401.
402.
403.
404.
405.
406.
At a fixed Cd2+ concentration water hyacinth (Eichhornia crassipes) plants with greater root mass (dry weight) take up more metal ions as a function of time, and more metal ions are taken up by a plant as the solution volume is increased. Experiments in which several different metal ion complexers were present suggest that (1) the roots possess sites which initially reversibly bind free Cd2+, (2) some added complexers can compete with these root sites for free Cd2+, and (3) with time Cd2+ bound to the roots is translocated into into the root tissues effectively removing it from the equilibrium processes in solution. Many metal ions are taken up by the plant but only the micronutrient Zn2+ competes well with Cd2+ for uptake. Thus, there may be binding sites on the roots for specific metal ions.  相似文献   
407.
408.
Early pregnancy renal anhydramios (EPRA) comprises congenital renal disease that results in fetal anhydramnios by 22 weeks of gestation. It occurs in over 1 in 2000 pregnancies and affects 1500 families in the US annually. EPRA was historically considered universally fatal due to associated pulmonary hypoplasia and neonatal respiratory failure. There are several etiologies of fetal renal failure that result in EPRA including bilateral renal agenesis, cystic kidney disease, and lower urinary tract obstruction. Appropriate sonographic evaluation is required to arrive at the appropriate urogenital diagnosis and to identify additional anomalies that allude to a specific genetic diagnosis. Genetic evaluation variably includes karyotype, microarray, targeted gene testing, panels, or whole exome sequencing depending on presentation. Patients receiving a fetal diagnosis of EPRA should be offered management options of pregnancy termination or perinatal palliative care, with the option of serial amnioinfusion therapy offered on a research basis. Preliminary data from case reports demonstrate an association between serial amnioinfusion therapy and short-term postnatal survival of EPRA, with excellent respiratory function in the neonatal period. A multicenter trial, the renal anhydramnios fetal therapy (RAFT) trial, is underway. We sought to review the initial diagnosis ultrasound findings, genetic etiologies, and current management options for EPRA.  相似文献   
409.
410.
The integration of non-continuous processes such as a milk powder plant presents a challenge for existing process integration techniques. Current techniques are generally based on steady and continuous operation which for some industries is not the case. Milk production varies considerably during the year as dairy cows in New Zealand are grazed on pasture. In this paper the potential for indirect heat transfer between the several plants using a heat recovery loop and stratified tank at a typical New Zealand dairy factory is investigated. The maximum amount of heat recovery is calculated for a range of recirculation loop temperatures. The maximum amount of heat recovery can be increased considerably if the temperature of the hot fluid in the recirculation loop is varied depending on which condition the site is operating under.  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