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   30514篇
  免费   447篇
  国内免费   444篇
安全科学   1011篇
废物处理   1206篇
环保管理   4409篇
综合类   5516篇
基础理论   7812篇
环境理论   16篇
污染及防治   7663篇
评价与监测   1792篇
社会与环境   1754篇
灾害及防治   226篇
  2022年   259篇
  2021年   266篇
  2020年   266篇
  2019年   245篇
  2018年   432篇
  2017年   463篇
  2016年   669篇
  2015年   541篇
  2014年   738篇
  2013年   2499篇
  2012年   989篇
  2011年   1383篇
  2010年   1079篇
  2009年   1217篇
  2008年   1325篇
  2007年   1400篇
  2006年   1214篇
  2005年   1019篇
  2004年   1003篇
  2003年   972篇
  2002年   879篇
  2001年   1084篇
  2000年   839篇
  1999年   519篇
  1998年   387篇
  1997年   386篇
  1996年   400篇
  1995年   447篇
  1994年   385篇
  1993年   384篇
  1992年   361篇
  1991年   361篇
  1990年   354篇
  1989年   328篇
  1988年   282篇
  1987年   243篇
  1986年   285篇
  1985年   280篇
  1984年   314篇
  1983年   295篇
  1982年   301篇
  1981年   287篇
  1980年   256篇
  1979年   265篇
  1978年   185篇
  1977年   195篇
  1975年   158篇
  1974年   178篇
  1973年   160篇
  1972年   187篇
排序方式: 共有10000条查询结果,搜索用时 750 毫秒
511.
The nature of the cosmic redshift is one of the most fundamental questions in modern science. Hubble's discovery of the apparent Expansion of the Universe is derived from observations on a small number of galaxies at very low redshifts. Today, quasar redshifts have a range more than 1000 times greater than those in Hubble's sample, and represent more than 100 times as many objects. A recent comprehensive compilation of published measurements provides the basis for a study indicating that quasar observations are not in good agreement with the original predictions of the Expanding Universe theory, but are well fit by the predictions of an alternative theory having fewer adjustable parameters.  相似文献   
512.
513.
514.
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   
515.
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   
516.
Dedicated to Prof. Dr. A. Buchs, University of Geneva, on the occasion of his 60th birthday.  相似文献   
517.
518.
We are very grateful to A. Gessner for his great help in the construction of the apparatus and A. Meyer for performance of some pressure bomb experiments. This work was supported by grants of the Deutsche Forschungsgemeinschaft (Forschergruppe Ökophysiologie) to U.Z. and O.L.L.  相似文献   
519.
520.
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