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   16457篇
  免费   207篇
  国内免费   153篇
安全科学   476篇
废物处理   602篇
环保管理   2324篇
综合类   3147篇
基础理论   4125篇
环境理论   10篇
污染及防治   4047篇
评价与监测   1001篇
社会与环境   954篇
灾害及防治   131篇
  2022年   124篇
  2021年   128篇
  2020年   113篇
  2019年   137篇
  2018年   207篇
  2017年   244篇
  2016年   343篇
  2015年   294篇
  2014年   382篇
  2013年   1399篇
  2012年   490篇
  2011年   643篇
  2010年   517篇
  2009年   588篇
  2008年   663篇
  2007年   686篇
  2006年   643篇
  2005年   520篇
  2004年   513篇
  2003年   520篇
  2002年   456篇
  2001年   562篇
  2000年   435篇
  1999年   255篇
  1998年   205篇
  1997年   196篇
  1996年   214篇
  1995年   223篇
  1994年   214篇
  1993年   209篇
  1992年   229篇
  1991年   211篇
  1990年   210篇
  1989年   183篇
  1988年   161篇
  1987年   136篇
  1986年   164篇
  1985年   167篇
  1984年   170篇
  1983年   173篇
  1982年   161篇
  1981年   170篇
  1980年   166篇
  1979年   152篇
  1978年   114篇
  1977年   124篇
  1974年   111篇
  1973年   91篇
  1972年   107篇
  1971年   89篇
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
311.
312.
313.
Uterine lavage affords the potential for non-invasive human blastocyst recovery, with obvious potential for preimplantation genetic diagnosis. In an effort to duplicate in women the multiple blastocyst recovery per cycle that can be achieved in several other species, we initiated a programme in which fertile women underwent superovulation, followed by lavage and embryo collection. We superovulated 15 fertile women, aged 21–40, in 29 cycles using one of four regimens. Insemination was by either intercourse or artificial intracervical donor insemination with cryopreserved sperm from men of proven fertility. In 28 of 29 cycles, the uterus was lavaged daily for 1, 2, or 3 days between 5 and 10 days after human chorionic gonadotropin (hCG) administration or luteinizing hormone (LH) surge. Almost total fluid volume was recovered in every lavage. There were no retained pregnancies and no complications. Surprisingly, only two morulae, one blastocyst, and four unfertilized ova were recovered. Thus, alterations in ovulation induction, insemination timing, or lavage techniques must be contemplated in order to increase the blastocyst yield and thus fulfil the potential of uterine lavage for preimplantation diagnosis.  相似文献   
314.
The natural desire for couples to be parents and the medical practitioner's inability to treat most genetic diseases have been responsible for some of the most exciting research into infertility and genetic disorders. This has led in the United Kingdom to the establishment of the Warnock Committee of Inquiry into Human Fertilization and its report in 1984, and to a Review of the guidance on Research Use of Fetuses and Fetal Material published in 1989 and known as the Polkinghorne Report. The Warnock Report, among other ethical issues, considers the most fundamental question which has been debated for thousands of years, namely, What is life and when does it begin? More recently, the report has been responsible for new legislation which imposes ethical and legal restrictions on the scientific and medical community. The Polkinghorne Report recommends a voluntary code of practice which is morally and ethically acceptable within our society. We are also fortunate in the U.K. to have a parliamentary structure which allows debate on such important human issues and is prepared to impose ethical restrictions.  相似文献   
315.
Dedicated to Prof. Dr. A. Buchs, University of Geneva, on the occasion of his 60th birthday.  相似文献   
316.
317.
318.
319.
Prenatal diagnosis of the cerebro-hepato-renal (Zellweger) syndrome has been performed in 10 pregnancies at risk by measuring both the activity of acyl CoA: dihydroxyacetonephosphate acyltransferase (DHAP-AT) and the de novo plasmalogen biosynthesis, either in cultured amniotic fluid cells or in fibroblasts cultured from a chorionic villus biopsy. In 7 of the pregnancies both tests indicated no abnormality. All 7 continued to term and normal infants were delivered. However, in amniotic fluid cells from 2 fetuses affected by Zellweger syndrome unequivocal differences from control values were found. The activity of DHAP-AT was clearly deficient and the de novo plasmalogen biosynthesis was impaired. In one pregnancy at risk prenatal diagnosis was performed during the first trimester by measuring both the DHAP-AT activity and the de novo plasmalogen biosynthesis in fibroblasts cultured from a chorionic villi biopsy. From the deficient DHAP-AT activity and the impaired de novo plasmalogen biosynthesis it was concluded that the fetus was affected. This was confirmed biochemically after induced abortion. It can be concluded that measurement of the DHAP-AT activity and the de novo plasmalogen biosynthesis provides convenient methods for the early prenatal detection of Zellweger syndrome.  相似文献   
320.
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