全文获取类型
收费全文 | 2715篇 |
免费 | 117篇 |
国内免费 | 13篇 |
出版年
2018年 | 18篇 |
2016年 | 20篇 |
2015年 | 19篇 |
2014年 | 18篇 |
2013年 | 68篇 |
2012年 | 68篇 |
2011年 | 60篇 |
2010年 | 67篇 |
2009年 | 115篇 |
2008年 | 87篇 |
2007年 | 65篇 |
2006年 | 66篇 |
2005年 | 55篇 |
2004年 | 58篇 |
2003年 | 35篇 |
2002年 | 34篇 |
2001年 | 28篇 |
2000年 | 24篇 |
1999年 | 32篇 |
1998年 | 39篇 |
1997年 | 42篇 |
1996年 | 40篇 |
1995年 | 30篇 |
1994年 | 27篇 |
1993年 | 19篇 |
1992年 | 36篇 |
1990年 | 26篇 |
1989年 | 28篇 |
1988年 | 21篇 |
1987年 | 27篇 |
1986年 | 27篇 |
1985年 | 26篇 |
1983年 | 24篇 |
1981年 | 23篇 |
1980年 | 18篇 |
1979年 | 23篇 |
1977年 | 24篇 |
1973年 | 18篇 |
1971年 | 17篇 |
1959年 | 49篇 |
1958年 | 123篇 |
1957年 | 137篇 |
1956年 | 134篇 |
1955年 | 149篇 |
1954年 | 150篇 |
1953年 | 119篇 |
1952年 | 105篇 |
1951年 | 98篇 |
1950年 | 59篇 |
1948年 | 24篇 |
排序方式: 共有2845条查询结果,搜索用时 15 毫秒
1.
An earlier report (1) of an adverse effect of high doses of oxytocin on human memory included results of studies on women receiving oxytocin as part of the treatment to induce 2nd trimester therapeutic abortion. These women served as their own controls. We have now been able to study a group of women who have been treated in all ways like the original group, with the exception that they did not receive oxytocin. The results from this external control corroborate the finding that oxytocin affected memory. 相似文献
2.
The revision of the antarctic–subantarctic species Orchomenopsis reducta Schellenberg, 1931, has led to its attribution to a new, highly apomorphic genus: Falklandia gen.n. A new definition of the uristid group is given and Falklandia with 36 other lysianassoid genera are attributed to this supposedly monophyletic group. 相似文献
3.
4.
5.
6.
A new micronucleus test using peripheral blood erythrocytes of the newt Pleurodeles waltl to detect mutagens in fresh-water pollution 总被引:4,自引:0,他引:4
A model micronucleus test system using peripheral blood erythrocytes from larvae of Pleurodeles waltl is described. The most suitable larval stage for testing chemical treatments was determined. Larvae were reared in water containing one of the 4 compounds: benzo[a]pyrene (BaP), ethyl methanesulphonate (EMS), diethyl sulphate (DES) and N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG). Response curves as a function of treatment duration over a period of 16 days were plotted for 3 different concentrations of the 4 compounds in order to optimize conditions for a low dose micronucleus test. This model can be used as a monitoring system for the detection of fresh water pollution and can also be employed for clastogen screening of chemical compounds. The test is sensitive, reliable and easy to use. 相似文献
7.
Cyanide-Resistant Root Respiration and Tap Root Formation in Two Subspecies of Hypochaeris radicata 总被引:1,自引:0,他引:1
Root respiration of the tap root forming species Hypochaeris radicata L. was measured during tap root formation. A comparison was made of two subspecies: H. radicata L. ssp. radicata L., a subspecies from relatively rich soils, and H. radicata L. ssp. ericetorum Van Soest, a subspecies from poor acidic soils. Root respiration was high and to a large extent inhibited by hydroxamic acid (SHAM) before the start of the tap root formation, indicating a high activity of an alternative non-phosphorylative electron transport chain. The rate of root respiration was much lower and less sensitive to SHAM when a considerable tap root was present. However, root respiration was also cyanide-resistant when a tap root was present, indicating that the alternative pathway was still present. A decreased rate of root respiration coincided with an increase of the content of storage carbohydrates, mainly in the tap root. The level of reducing sugars was constant throughout the experimental period, and it was concluded that the activity of the alternative oxidative pathway was significant in oxidation of sugars that could not be utilized for purposes like energy production, the formation of intermediates for growth or for storage. Root respiration decreased after the formation of a tap root. This decrease could neither be attributed to a gradual disappearance of the alternative chain, nor to a decreased level of reducing sugars. No differences in respiratory metabolism between the two subspecies have been observed, suggesting that a high activity of the alternative oxidative pathway is not significant in adaptation of the present two subspecies to relatively nutrient-rich or poor soils. 相似文献
8.
9.
10.