全文获取类型
收费全文 | 2372篇 |
免费 | 205篇 |
国内免费 | 1篇 |
出版年
2022年 | 20篇 |
2021年 | 41篇 |
2020年 | 14篇 |
2019年 | 19篇 |
2018年 | 31篇 |
2017年 | 26篇 |
2016年 | 55篇 |
2015年 | 86篇 |
2014年 | 86篇 |
2013年 | 98篇 |
2012年 | 143篇 |
2011年 | 134篇 |
2010年 | 95篇 |
2009年 | 114篇 |
2008年 | 113篇 |
2007年 | 129篇 |
2006年 | 117篇 |
2005年 | 122篇 |
2004年 | 102篇 |
2003年 | 97篇 |
2002年 | 127篇 |
2001年 | 49篇 |
2000年 | 43篇 |
1999年 | 39篇 |
1998年 | 32篇 |
1997年 | 23篇 |
1996年 | 28篇 |
1995年 | 31篇 |
1994年 | 22篇 |
1993年 | 25篇 |
1992年 | 41篇 |
1991年 | 33篇 |
1990年 | 41篇 |
1989年 | 45篇 |
1988年 | 28篇 |
1987年 | 25篇 |
1986年 | 24篇 |
1985年 | 28篇 |
1984年 | 24篇 |
1983年 | 19篇 |
1982年 | 21篇 |
1981年 | 23篇 |
1980年 | 21篇 |
1979年 | 23篇 |
1978年 | 25篇 |
1977年 | 13篇 |
1976年 | 14篇 |
1975年 | 11篇 |
1974年 | 11篇 |
1973年 | 11篇 |
排序方式: 共有2578条查询结果,搜索用时 171 毫秒
1.
2.
When fibrin polymerizes in a strong magnetic field, it can be highly oriented. The structural diffraction study of the oriented polymer becomes thus possible. The magnetic birefringence can also be used to study the development of the polymer Fibrinogen in solution is weakly oriented in high magnetic fields. In this work we present complementary results and discussion. The validity of the comparison of the orientation parameters of fibrinogen and fibrin with those of other orientable known biological structures is discussed. The orientation of fibrin formed from fibrin monomer solution is compared to that of fibrin formed by the action of thrombin on fibrinogen. The conditions to obtain highly oriented fibrin gels suitable for three dimensional structure studies are also briefly discussed. 相似文献
3.
Using benzo(a)pyrene (BaP) as a probe for aryl hydrocarbon hydroxylase (AHH) activity, differences in mixed-function oxidase (MFO) activity were observed using microspectrofluorimetry in single living cells during long term treatment with 3-methylcholanthrene (3-MC) or carbaryl. Although these two compounds differ in chemical structure, similar effects were observed in 3T3 cell populations. The results suggest that the two compounds activate the same enzymatic system and that individual cells of a supposed homogeneous cell population are not equally sensitive to xenobiotics, i.e. subpopulations were observed which have differences in AHH activity. 相似文献
4.
Jean-Marie Delaissé Philippe Martin Marie-Françoise Verheyen-Bouvy Edmond-Jacques Nyns 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,676(1):77-90
The subcellular localization of the ω-hydroxylase of Saccharomycopsis lipolytica was assessed by the analytical fractionation technique, originally described by de Duve C., Pressman, B.C., Gianetto, R., Wattiaux, R. and Appelmans, F., and hitherto little, if at all, applied to yeast. Protoplasts were separated in six fractions by differential centrifugation. Some of these fractions were further fractioned by density gradient centrifugation. The distribution of ω-hydroxylase and 15 other constituents chosen as possible markers of its subcellular membranes has been established. ω-Hydroxylase resulted in being bound to a membrane that containes also cytochrome P-450 and NADPH-cytochrome c reductase. This membrane clearly differs from five other subcellular entities. (1) Mitochondria were characterized by particulate malate dehydrogenase, particulate Antimycin A-insensitive NADH-cytochrome c reductase, oligomycin-sensitive and K+-stimulated ATPase pH 9. (2) Most if not all of the catalase and urate oxidase is peroxisomal. (3) Free ribosomes account for most RNA. (4) Nucleoside diphosphatase is for the first time reported in a yeast and appears to belong to an homogeneous population of small membranes. (5) The soluble compartment contains magnesium pyrophosphatase, alkaline phosphatase, 5′-nucleotidase and part of the NADH-cytochrome c reductase. Latent arylesterase and ATPase pH7 have an unspecific distribution. Alkaline phosphodiesterase I has not been detected. 相似文献
5.
Jean-Michel Panoff Bouachanh Thammavongs Jean-Marie Laplace Axel Hartke Philippe Boutibonnes Yanick Auffray 《Cryobiology》1995,32(6)
The physiology of the cold-shock response in Lactococcus lactis subsp. lactis IL1403 at a subzero temperature, and cold-induced adaptation to heat shock, were investigated. Preincubation of cells at 8°C led to the development of cryotolerance, i.e., an enhanced capacity to survive exposure to freezing temperature (-20°C). Pretreatment with chemicals considered to be chaotropic agents did not induce cryotolerance or, in contrast, led to a decrease in survival capacity at -20°C. Interestingly, preincubation at 8°C led also to thermololerance to a 52°C challenge, but preincubation of cells at 42°C for 30 min did not improve their capacity to survive freezing-thawing exposure. These results demonstrate that cold- and heat-shock responses are physiologically linked by a complex relation. Furthermore, food processing at low temperature before subzero or heat treatment may need to be reconsidered. 相似文献
6.
7.
8.
9.
10.
Is progesterone a pre-hormone in the CNS? 总被引:3,自引:0,他引:3
In this paper, experimental evidences have been presented indicating that progesterone per se appears to be a powerful modulatory steroid of presynaptic striatal dopaminergic terminals of the central nervous system of the rat. This effect of the progesterone signal is concentration as well as infusion mode dependent. Low pulsatile doses of the steroid positively modulate the mechanism by which dopamine terminals respond to amphetamine stimulation and increase tissue dopamine concentration. Whereas, continuous and/or high doses of this steroid negatively modulate the response of the dopamine terminals to amphetamine stimulation and decreases tissue dopamine concentration. This effects occurs through a membrane mediated mechanism either upon the dopamine neuron directly and/or upon an interneuron. Pregnanolone a 5- beta-3 beta-metabolite of progesterone known to activate the hypothalamic LHRH neural apparatus at the level of the hypothalamus of ovariectomized estrogen primed rats in both in vitro as well as in vivo preparations was completely ineffective at the level of the corpus striatum of similar animal preparations. Therefore, it is reasonable to assume that site specific mechanisms exist within the central nervous system which may control differentially the final action of progesterone. In the hypothalamus, pregnanolone appears to be the final signal for its action on the LHRH neural apparatus, whereas in the corpus striatum, the steroid per se, and dependent on the modality and/or the strength of the signal can either directly or indirectly up-regulate (stimulatory component) or down-regulate (inhibitory component) the activity of striatal dopaminergic terminals. 相似文献