全文获取类型
收费全文 | 22350篇 |
免费 | 213篇 |
国内免费 | 179篇 |
专业分类
安全科学 | 617篇 |
废物处理 | 951篇 |
环保管理 | 2808篇 |
综合类 | 3149篇 |
基础理论 | 5854篇 |
环境理论 | 9篇 |
污染及防治 | 6635篇 |
评价与监测 | 1507篇 |
社会与环境 | 1072篇 |
灾害及防治 | 140篇 |
出版年
2023年 | 125篇 |
2022年 | 238篇 |
2021年 | 277篇 |
2020年 | 162篇 |
2019年 | 212篇 |
2018年 | 396篇 |
2017年 | 418篇 |
2016年 | 613篇 |
2015年 | 506篇 |
2014年 | 723篇 |
2013年 | 1873篇 |
2012年 | 845篇 |
2011年 | 1063篇 |
2010年 | 792篇 |
2009年 | 863篇 |
2008年 | 1087篇 |
2007年 | 1117篇 |
2006年 | 953篇 |
2005年 | 791篇 |
2004年 | 798篇 |
2003年 | 727篇 |
2002年 | 712篇 |
2001年 | 810篇 |
2000年 | 587篇 |
1999年 | 346篇 |
1998年 | 258篇 |
1997年 | 237篇 |
1996年 | 284篇 |
1995年 | 293篇 |
1994年 | 278篇 |
1993年 | 233篇 |
1992年 | 220篇 |
1991年 | 202篇 |
1990年 | 221篇 |
1989年 | 200篇 |
1988年 | 192篇 |
1987年 | 181篇 |
1986年 | 168篇 |
1985年 | 156篇 |
1984年 | 185篇 |
1983年 | 186篇 |
1982年 | 178篇 |
1981年 | 177篇 |
1980年 | 147篇 |
1979年 | 167篇 |
1978年 | 115篇 |
1977年 | 106篇 |
1975年 | 101篇 |
1973年 | 95篇 |
1972年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
C. A. Dell'Agnola V. Tomaselli E. Teruzzi B. Tadini A. G. Coran Surgeon-in-Chief 《黑龙江环境通报》1993,13(7):629-632
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
82.
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
83.
84.
85.
86.
John C. Eccles 《Die Naturwissenschaften》1979,66(3):147-153
Synaptic plasticity is manifested by long-lasting changes in synaptic potency. Increased potency is of special importance in relation to the neural basis of memory. Even mild repetitive stimulation evokes large and prolonged potentiations of hippocampal synapses, as is revealed by electrical recording either in vivo or in vitro. More importantly there is a matching hypertrophy of the synaptic spines on the dendrites of hippocampal granule cells, as is shown by most convincing electronmicrographs. The increase is to about 40% some 2 h after a mild stimulation (900 impulses) and there was relatively little decline by 23 h. There is brief reference to the metabolic processes that could be involved in this plastic response. 相似文献
87.
88.
89.
90.