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   19070篇
  免费   172篇
  国内免费   141篇
安全科学   368篇
废物处理   750篇
环保管理   1965篇
综合类   5054篇
基础理论   4257篇
环境理论   10篇
污染及防治   4632篇
评价与监测   1167篇
社会与环境   1122篇
灾害及防治   58篇
  2022年   145篇
  2021年   149篇
  2019年   126篇
  2018年   250篇
  2017年   232篇
  2016年   373篇
  2015年   290篇
  2014年   439篇
  2013年   1224篇
  2012年   499篇
  2011年   687篇
  2010年   571篇
  2009年   650篇
  2008年   736篇
  2007年   798篇
  2006年   695篇
  2005年   582篇
  2004年   600篇
  2003年   602篇
  2002年   556篇
  2001年   677篇
  2000年   463篇
  1999年   347篇
  1998年   228篇
  1997年   249篇
  1996年   247篇
  1995年   270篇
  1994年   266篇
  1993年   242篇
  1992年   211篇
  1991年   238篇
  1990年   225篇
  1989年   190篇
  1988年   190篇
  1987年   168篇
  1986年   167篇
  1985年   174篇
  1984年   187篇
  1983年   176篇
  1982年   194篇
  1981年   156篇
  1980年   151篇
  1979年   155篇
  1978年   156篇
  1977年   136篇
  1974年   128篇
  1967年   145篇
  1964年   124篇
  1963年   126篇
  1957年   124篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
341.
The impact of prenatal sonographic diagnosis of oesophageal and gastrointestinal obstructions has been analysed over a 10-year period. Three groups of patients were evaluated. The first group consisted of 46 newborns with abnormal prenatal sonogratns, 41 of which were confirmed to have intestinal obstruction postnatally. The second group consisted of 17 neonates with normal prenatal sonograms who had intestinal obstruction postnatally. The third group included 56 newborns who did not undergo a prenatal sonogram but who had intestinal obstruction confirmed at surgery. Polyhydramnios without the appearance of a stomach on ultrasound was diagnostic of pure oesophageal atresia. Polyhydramnios with intestinal dilation was diagnostic of intestinal obstruction. Although surgery was performed earlier in the infants diagnosed prenatally with ultrasound, mortality was no less than in the group that did not undergo a prenatal sonogram, probably because of the high incidence of associated anomalies.  相似文献   
342.
343.
344.
345.
346.
347.
The increasing interest in the parasites of man in the Federal Republic of Germany is connected with the unbounded keenness of German people to travel. They favor southern regions with warm climates which are usually infested with parasites. Thus the general practitioner is nowadays confronted in his daily routine with “imported” pathogenic organisms and diseases as yet unknown to him or with which he need not have reckoned in the past. Furthermore, new information now exists on the development of well-known parasites of our regions, which can be pathogenic to man. Fortunately, new reliable drugs have come on the market, rendering some parasitic diseases harmless.  相似文献   
348.
Circulating placental [human chorionic gonadotrophin (hCG), Schwangerschafts protein 1 (SP1), pregnancy-associated plasma protein A (PAPP-A), decidual (pregnancy protein) 12 (PP12), and fetal alphafetoprotein (AFP)] proteins were measured immediately before and within 1 h in 18 women undergoing diagnostic chorionic villus sampling (CVS) in the first trimester. An elevation of serum AFP levels was consistently seen, while fluctuations in excess of 10 per cent of the pre-CVS levels of SP1 and PP12 were seen in the majority of patients. Fluctuations in hCG and PAPP-A were consistently less than 10 per cent of pre-CVS values. Post-CVS changes in levels were not apparently associated with any feature of the technique, the pregnancy, or its outcome (one missed abortion). As feto-maternal haemorrhage is a common event, anti-D should be offered to rhesus-negative women undergoing CVS. In the prediction of subsequent miscarriage, only hCG and PAPP-A measurements should be considered.  相似文献   
349.
350.
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