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   17385篇
  免费   143篇
  国内免费   112篇
安全科学   407篇
废物处理   656篇
环保管理   1911篇
综合类   5389篇
基础理论   3603篇
环境理论   2篇
污染及防治   4108篇
评价与监测   880篇
社会与环境   623篇
灾害及防治   61篇
  2018年   204篇
  2017年   188篇
  2016年   287篇
  2015年   217篇
  2014年   319篇
  2013年   1159篇
  2012年   372篇
  2011年   519篇
  2010年   496篇
  2009年   561篇
  2008年   577篇
  2007年   601篇
  2006年   530篇
  2005年   469篇
  2004年   506篇
  2003年   461篇
  2002年   437篇
  2001年   619篇
  2000年   417篇
  1999年   284篇
  1998年   206篇
  1997年   196篇
  1996年   196篇
  1995年   236篇
  1994年   245篇
  1993年   208篇
  1992年   223篇
  1991年   233篇
  1990年   253篇
  1989年   231篇
  1988年   182篇
  1987年   181篇
  1986年   182篇
  1985年   181篇
  1984年   200篇
  1983年   187篇
  1982年   199篇
  1981年   209篇
  1980年   172篇
  1979年   180篇
  1978年   149篇
  1976年   140篇
  1974年   149篇
  1973年   146篇
  1968年   157篇
  1967年   187篇
  1966年   156篇
  1965年   150篇
  1964年   151篇
  1963年   140篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
151.
The female silkmoth Bombyx mori L. emits a second pheromone component bombykal (E-10, Z-12-hexade-cadien-1-al) in addition to the well-known sexual attractant bombykol (E-10, Z-12-hexadecadien-1-ol). Bombykal stimulates its own specialized and highly sensitive olfactory cells of the male moth. Surprisingly, the aldehyde inhibits the release of the male's wing-fluttering response to bombykol.  相似文献   
152.
153.
154.
As screening for Down syndrome becomes increasingly sophisticated, it is important to evaluate the newer technologies in terms of their cost-effectiveness. One recent addition to Down syndrome screening programmes is maternal serum unconjugated oestriol (uE3), especially when used in conjunction with maternal serum α-fetoprotein and human chorionic gonadotropin. Using assumptions used in a California proposal to justify an expanded screening programme for Down syndrome, we calculated both the average and the incremental cost-effectiveness of adding uE3. Using the base case assumptions, including an $8 fee for the uE3, the incremental cost-effectiveness of adding uE3 to the proposed California programme is $119 100 per case detected, a value that compares favourably with other Down syndrome screening programmes. The sensitivity analysis supports this conclusion over a wide range of assumptions. However, because of the uncertainty with some key data, it is still too early to fully support the inclusion of uE3 in Down syndrome screening programmes.  相似文献   
155.
In recent years, an increasing number of inherited diseases in man have been recognized in which there is an impairment in the peroxisomal β-oxidation of very-long-chain fatty acids. In general, these disorders are associated with severe neurological and physical abnormalities and death within the first years of life. In this paper we describe our experience with regard to the prenatal diagnosis of a number of different inborn errors of peroxisomal β-oxidation. Eleven pregnancies at risk were monitored by measuring very-long-chain fatty acid levels as well as very-long-chain fatty acid β-oxidation in cultured chorionic villous fibroblasts and/or amniotic fluid cells. Five affected fetuses were identified. It is concluded that prenatal diagnosis in this group of diseases can be done reliably using cultured chorionic villous fibroblasts or amniotic fluid cells.  相似文献   
156.
Chorionic villus sampling (CVS) with either transcervical catheters or transabdominal needles is a widely-accepted method for prenatal diagnosis. However, there exists a small subset of patients in whom sampling is difficult or impossible with either route because of individual anatomic variations. A new method of chorionic villus biopsy has been developed to circumvent these problems, utilizing transvaginal chorionic needle aspiration guided by an intravaginal ultrasound probe. This technique was performed successfully in 15 patients in whom villi could not be obtained by either of the conventional methods. This method now makes CVS possible in essentially all women regardless of their uterine anatomy or placental placement; it may also prove useful for very early chorionic sampling.  相似文献   
157.
158.
159.
Plasticity of honeybee castes   总被引:1,自引:0,他引:1  
  相似文献   
160.
Prenatal real-time ultrasonographic diagnosis of microphthalmia is presented. Diagnosis was made at 18 weeks' gestation in a fetus of a patient with a previous infant affected with the syndrome of cryptophthalmia with absence of septum nasi and ambiguous genitalia (Fraser syndrome). Recognition of microphthalmia as a part of Fraser syndrome and the easy visualization of fetal facial bones and orbits in the second trimester made the diagnosis possible.  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