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   16780篇
  免费   179篇
  国内免费   193篇
安全科学   455篇
废物处理   650篇
环保管理   2331篇
综合类   2674篇
基础理论   4562篇
环境理论   4篇
污染及防治   4440篇
评价与监测   1063篇
社会与环境   867篇
灾害及防治   106篇
  2022年   122篇
  2021年   142篇
  2020年   119篇
  2019年   155篇
  2018年   232篇
  2017年   235篇
  2016年   375篇
  2015年   252篇
  2014年   377篇
  2013年   1322篇
  2012年   451篇
  2011年   654篇
  2010年   559篇
  2009年   537篇
  2008年   707篇
  2007年   711篇
  2006年   680篇
  2005年   527篇
  2004年   602篇
  2003年   535篇
  2002年   498篇
  2001年   720篇
  2000年   481篇
  1999年   289篇
  1998年   242篇
  1997年   219篇
  1996年   232篇
  1995年   255篇
  1994年   278篇
  1993年   224篇
  1992年   250篇
  1991年   224篇
  1990年   254篇
  1989年   241篇
  1988年   197篇
  1987年   176篇
  1986年   160篇
  1985年   168篇
  1984年   192篇
  1983年   181篇
  1982年   187篇
  1981年   180篇
  1980年   138篇
  1979年   154篇
  1978年   132篇
  1977年   117篇
  1975年   121篇
  1974年   117篇
  1973年   110篇
  1972年   133篇
排序方式: 共有10000条查询结果,搜索用时 115 毫秒
161.
162.
163.
Research in molecular neurobiology has recently entered a new phase of rapid development as a result of the application of the techniques of molecular genetics. This is illustrated by recent work on the electric ray (Torpedo marmorata and T. californica), whose electric organ is a rich source of cholinergic synapses. Other examples from recent literature of the application of the recombinant DNA technique to the mammalian central nervous system are given and possible future developments are discussed.  相似文献   
164.
165.
Mosaicism for the Wolf-Hirschhorn syndrome, del(4)(p16), is extremely rare and has not been reported in association with a numerical chromosome abnormality. We report the prenatal diagnosis of mosaic del(4)(p16) and non-mosaic trisomy 21 in a 16-week female fetus. The pregnancy ended in spontaneous abortion at 34 weeks secondary to fetal demise. The fetus had features of both 4p – and trisomy 21.  相似文献   
166.
A case of gastric outlet obstruction diagnosed prenatally at 22 weeks' gestation is described. The differential diagnosis and the clinical management of this rare condition are discussed, and an updated literature review is presented.  相似文献   
167.
Cytomegalovirus (CMV) is the most common cause of intrauterine infection. Recent publications show amniocentesis to have an 81–100 per cent sensitivity in antenatal diagnosis after 21 weeks' gestation. Testing before 21 weeks' gestation is less well documented. We performed 36 amniocenteses between 14 and 20 weeks' gestation. The sensitivity was 45 per cent and the specificity 100 per cent. Implications and possible causes of this low sensitivity are discussed.  相似文献   
168.
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   
169.
This paper reports results of an exploratory study of prenatal diagnosis patients who experienced voluntary terminations of pregnancy following the detection of an abnormality or spontaneous miscarriages. The 121 participants were part of the national collaborative Chorionic Villus Sampling and Amniocentesis Study. They completed semi-structured telephone interviews and mailed questionnaires at 1 month and 6 months after the pregnancy losses. Scores on the Profile of Mood States showed that mood levels improved significantly over time. However, there were some declines in loss-related support from partners and others. The persisting distress and difficulties of a minority highlight the variability in women's responses to pregnancy losses. Women who lost pregnancies later in gestation, showed the greatest mood disturbances at initial assessments, used professional mental health assistance after the loss, or reported less satisfactory loss-related support from significant others showed the greatest levels of mood disturbance at the six-month assessment. Follow-up contacts with patients who lose pregnancies should be used to inform women about the variation in possible grief reactions, to assess the extent of support the women are receiving from their partners and significant others, and to provide additional follow-up or referral of those experiencing the greatest distress.  相似文献   
170.
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