全文获取类型
收费全文 | 425658篇 |
免费 | 48007篇 |
国内免费 | 162篇 |
出版年
2018年 | 3920篇 |
2016年 | 5300篇 |
2015年 | 6957篇 |
2014年 | 8194篇 |
2013年 | 11288篇 |
2012年 | 12851篇 |
2011年 | 13301篇 |
2010年 | 9119篇 |
2009年 | 8465篇 |
2008年 | 12164篇 |
2007年 | 12675篇 |
2006年 | 11867篇 |
2005年 | 11354篇 |
2004年 | 11388篇 |
2003年 | 10670篇 |
2002年 | 10493篇 |
2001年 | 17426篇 |
2000年 | 17438篇 |
1999年 | 13920篇 |
1998年 | 5026篇 |
1997年 | 5274篇 |
1996年 | 4924篇 |
1995年 | 4624篇 |
1994年 | 4495篇 |
1993年 | 4538篇 |
1992年 | 11612篇 |
1991年 | 11539篇 |
1990年 | 11300篇 |
1989年 | 10912篇 |
1988年 | 10489篇 |
1987年 | 10076篇 |
1986年 | 9364篇 |
1985年 | 9239篇 |
1984年 | 7751篇 |
1983年 | 6707篇 |
1982年 | 5166篇 |
1981年 | 4620篇 |
1980年 | 4464篇 |
1979年 | 7423篇 |
1978年 | 5865篇 |
1977年 | 5399篇 |
1976年 | 5207篇 |
1975年 | 5596篇 |
1974年 | 6306篇 |
1973年 | 6173篇 |
1972年 | 5768篇 |
1971年 | 5228篇 |
1970年 | 4637篇 |
1969年 | 4574篇 |
1968年 | 4425篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
182.
183.
184.
V Ia Gotlib I I Pelevina E F Konoplia A A Al'ferovich A A Konradov 《Radiobiologiia》1991,31(3):318-325
On the basis of their own data and the literature the authors have analyzed the mechanism of biological action of low-level radiation on cells. In studying the harmful effect of gamma-radiation (10-40 cGy) on HeLa cells it was shown that damages occurred in 12 postirradiation generations. Analysis of cell distribution within the colonies has demonstrated that the share of colonies with low cell content and the number of giant cell increase. These data indicate that low-level radiation causes reproductive cell death that can occur not immediately but in later generations. 相似文献
185.
186.
E T Iwamoto 《Life sciences》1988,43(6):503-508
Intracerebroventricular (i.c.v.) administration of dynorphin A [1-17] induced significant place preference conditioning in male, Sprague-Dawley rats. Place preferences were induced by 2.3 and 3.5 nmole, but not 1.2 nmole of dynorphin A. Co-administration of naloxone, 27.5 nmole but not 5.5 nmole, antagonized the reward response induced by 2.3 nmole of dynorphin A. Leu-enkephalin, 5 or 25 nmole, and dynorphin A [2-17], 2.3 or 3.5 nmole, had no effect in the place conditioning paradigm. 相似文献
187.
E A Rybnikova V G Shaliapina O N Zamuruev 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1999,49(1):77-83
The effects of corticotropin-releasing hormone (CRH) injected into the dorsal neostriatum on the open-field and shuttle-box behavior were studied in rats with high (Koltushi high avoidance, KHA) and low (Koltushi low avoidance, KLA) capability for avoidance learning. The effects of this hormone on the behavior of these rat strains were different. In KLA rats with passive strategy of behavior the CRH injection led to a rapid locomotor activation in the open field, while the rats with active behavioral strategy (KHA) reacted to the injection by a significant decrease in locomotion and change for the passive mode of behavior. The same CRH effects on locomotion were obtained in the shuttle-box experiments. Moreover, in the KLA rats the neurohormone injection resulted in an improvement of avoidance learning in contrast to the KHA rats, in which CRH substantially impaired avoidance learning. The obtained evidence is discussed in terms of the important role of striatal CRH in the choice of behavioral strategy in stress. 相似文献
188.
X-IRRADIATION of mammalian cells in culture yields a survival curve of the threshold type (for review see ref. 1). It isjnter-esting to ask how one can enhance the radiation response by small changes of the physical environment of the cells, as can be done chemically, for example, by incorporation of 5-bromo-deoxyuridine into DNA1,2. Elevation of the temperature is a likely prospect for enhancement of radiosensitivity for the following reasons. It is known that proteins are heat labile and that temperature sensitive mutants of bacteria and phage can be obtained for many different enzymes3 which are operative at 37° C but not at 42° or 43°C. For example4, DNA polymerase is reversibly temperature sensitive; it is rendered inoperative above 42°C, but will be functional again when the temperature is lowered. It is not unreasonable to expect that temperature sensitive mutations for many enzymes occur frequently and that the use of temperatures somewhat higher than the normal range at which the cells grow might disclose sensitivities for specific enzymes in normal cells of higher organisms. 相似文献
189.
190.