全文获取类型
收费全文 | 20049篇 |
免费 | 231篇 |
国内免费 | 188篇 |
专业分类
安全科学 | 536篇 |
废物处理 | 865篇 |
环保管理 | 3023篇 |
综合类 | 3974篇 |
基础理论 | 4567篇 |
环境理论 | 11篇 |
污染及防治 | 4933篇 |
评价与监测 | 1300篇 |
社会与环境 | 1168篇 |
灾害及防治 | 91篇 |
出版年
2022年 | 125篇 |
2021年 | 164篇 |
2019年 | 152篇 |
2018年 | 261篇 |
2017年 | 273篇 |
2016年 | 409篇 |
2015年 | 338篇 |
2014年 | 453篇 |
2013年 | 1562篇 |
2012年 | 563篇 |
2011年 | 813篇 |
2010年 | 633篇 |
2009年 | 722篇 |
2008年 | 858篇 |
2007年 | 897篇 |
2006年 | 805篇 |
2005年 | 645篇 |
2004年 | 689篇 |
2003年 | 679篇 |
2002年 | 626篇 |
2001年 | 692篇 |
2000年 | 482篇 |
1999年 | 381篇 |
1998年 | 249篇 |
1997年 | 260篇 |
1996年 | 287篇 |
1995年 | 299篇 |
1994年 | 287篇 |
1993年 | 272篇 |
1992年 | 259篇 |
1991年 | 246篇 |
1990年 | 246篇 |
1989年 | 208篇 |
1988年 | 200篇 |
1987年 | 189篇 |
1986年 | 195篇 |
1985年 | 181篇 |
1984年 | 208篇 |
1983年 | 209篇 |
1982年 | 208篇 |
1981年 | 194篇 |
1980年 | 173篇 |
1979年 | 141篇 |
1978年 | 157篇 |
1977年 | 132篇 |
1976年 | 115篇 |
1975年 | 118篇 |
1974年 | 124篇 |
1971年 | 110篇 |
1967年 | 106篇 |
排序方式: 共有10000条查询结果,搜索用时 968 毫秒
291.
Data from 2907 transcervical CVS cases performed on singleton pregnancies were reviewed retrospectively and villus sample size was correlated with cytogenetic results, placental location, maternal age at the expected date of confinement (EDC), gestational age at the time of sampling, birth weight, gestational age at the time of delivery, and pregnancy outcome. No correlation was noted between villus sample size and maternal age, gestational age at sampling, gestational age at delivery, birth weight, or pregnancy outcome. An inverse correlation between villus sample size and percentage of abnormal cytogenetic findings was statistically significant (X2 = 8·53, p <0·01). The percentage of small samples was greater when the placenta was anterior, lateral, or fundal than when the placenta was posterior. 相似文献
292.
293.
294.
G. Piekarski 《Die Naturwissenschaften》1980,67(1):29-34
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
295.
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
296.
297.
298.
W. Götz 《Die Naturwissenschaften》1963,50(17):567-567
299.
300.
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