全文获取类型
收费全文 | 382325篇 |
免费 | 37395篇 |
国内免费 | 4113篇 |
专业分类
423833篇 |
出版年
2021年 | 4559篇 |
2019年 | 3941篇 |
2018年 | 5243篇 |
2017年 | 4782篇 |
2016年 | 6387篇 |
2015年 | 7398篇 |
2014年 | 9206篇 |
2013年 | 11841篇 |
2012年 | 13326篇 |
2011年 | 13709篇 |
2010年 | 9316篇 |
2009年 | 8413篇 |
2008年 | 11211篇 |
2007年 | 11176篇 |
2006年 | 10577篇 |
2005年 | 9765篇 |
2004年 | 9459篇 |
2003年 | 9244篇 |
2002年 | 8843篇 |
2001年 | 20696篇 |
2000年 | 20418篇 |
1999年 | 15590篇 |
1998年 | 4431篇 |
1997年 | 4573篇 |
1996年 | 4333篇 |
1995年 | 3989篇 |
1994年 | 3831篇 |
1993年 | 3615篇 |
1992年 | 11519篇 |
1991年 | 11076篇 |
1990年 | 10672篇 |
1989年 | 10442篇 |
1988年 | 9578篇 |
1987年 | 8784篇 |
1986年 | 7902篇 |
1985年 | 8092篇 |
1984年 | 6257篇 |
1983年 | 5469篇 |
1982年 | 3838篇 |
1981年 | 3439篇 |
1979年 | 5717篇 |
1978年 | 4413篇 |
1977年 | 4000篇 |
1976年 | 3777篇 |
1975年 | 4329篇 |
1974年 | 4583篇 |
1973年 | 4638篇 |
1972年 | 4031篇 |
1971年 | 3740篇 |
1970年 | 3314篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
F N Dodoo 《Social biology》1992,39(1-2):102-108
Data from the 1988 Ghana Demographic and Health Survey is employed to determine the existence of a relationship between the amount of education a woman has and her intent to cease childbearing. The findings are that with increasing levels of education, a female's desire to cease reproduction also increases. However, this relationship is obscured if parity is not controlled. 相似文献
992.
M Chen-Zion Y Bassukevitz R Beitner 《The International journal of biochemistry》1992,24(10):1661-1667
1. Time-curves of insulin effects on energy-producing systems in different cellular compartments of rat diaphragm muscle have revealed: (a) a rapid (within minutes) and transient stimulatory effect of insulin on cytoskeletal phosphofructokinase and aldolase and mitochondrial hexokinase. (b) A slower and consistent stimulatory effect on glucose 1,6-bisphosphate level, with concomitant gradual activation of cytosolic phosphofructokinase. Fructose 2,6-bisphosphate levels were not changed by insulin. (c) Lactate concentration correlated with the stimulation of cytoskeletal and cytosolic glycolysis. 2. Calmodulin antagonists, trifluoperazine or CGS 9343B, prevented all these effects of insulin. 3. These results suggest that cytoskeletal glycolysis and mitochondrial oxidation are the source of ATP for the rapid actions of insulin, whereas cytosolic glycolysis is the source of ATP for the slow actions of insulin. Calmodulin is involved in all these effects of insulin. 相似文献
993.
994.
Baby hamster kidney cells were seeded onto Western blots of fetal serum proteins which had been extracted from several foreign surfaces. This revealed that the major cell adhesive proteins adsorbed onto these surfaces from fetal serum were (1) fibronectin of Mr 220,000 Da and (2) vitronectin of Mr 65,000 and 78,000 Da. Two minor bands of cell attachment were observed at Mr 153,000 and Mr 134,000 Da in the fetal serum proteins extracted from heparin-agarose and serotonin-agarose. However, by exposing the Western blots of separated proteins to a second round of serum proteins, prior to cell blotting, very strong cell adhesive bands were revealed at Mr 153,000, 134,000, and 120,000 Da. By (i) modifying the composition of the serum proteins used to treat the Western blots, (ii) using specific antibodies to fibronectin, and (iii) using radiolabeled fibronectin, it was conclusively demonstrated that the new cell adhesive bands owed their increased cell attachment activity to secondary binding of fibronectin. The new bands were shown (i) to be trypsin sensitive and collagenase sensitive and therefore to be collagen-like proteins and (ii) to react negatively in immunoblots using anti-fibronectin, anti-vitronectin, anti-fibrinogen, anti-fetuin or anti-thrombospondin. In SDS-PAGE (i) the Mr 120,000-Da protein comigrated with the alpha 2-chain of Type I collagen, (ii) the Mr 134,000-Da protein comigrated with the alpha 1-chain of Type I collagen, and (iii) the Mr 153,000-Da protein comigrated with the pN-alpha 1-chain of Type III collagen. Since the novel collagen-like proteins acted as strong sites of cell attachment on nitrocellulose blots by binding fibronectin, they might well promote cell attachment on the foreign surfaces from which they were extracted. 相似文献
995.
H Kobayashi A Inoue T Mikawa H Kuwayama Y Hotta T Masaki S Ebashi 《Journal of biochemistry》1992,112(6):786-791
Two proteins with myosin light chain kinase activity and electrophoretic molecular weights of 155,000 and 130,000 were each isolated from bovine stomach smooth muscle [Kuwayama, H., Suzuki, M., Koga, R., & Ebashi, S. (1988) J. Biochem. 104, 862-866]. The 155 kDa component showed a much higher superprecipitation-inducing activity than the 130 kDa component, when compared on the basis of equivalent myosin light chain kinase activity. In this study, we isolated a cDNA for the entire coding region of the 155 kDa protein. The deduced amino acid sequence revealed a high degree of similarity to those of chicken and rabbit smooth muscle myosin light chain kinases. Multiple motifs, such as three repeats of an immunoglobulin C2-like domain, a fibronectin type III domain, and unusual 20 repeats of 12 amino acids were detected in the sequence. Part of the amino-terminal sequence was similar to that of the actin- and calmodulin-binding domain of smooth muscle caldesmon. These observations suggest that the 155 kDa protein has additional functions other than its enzymatic activity. Two mRNAs of 6.0 and 2.6 kb in length in the bovine stomach smooth muscle RNAs were hybridized with cDNA probes. The 2.6-kb RNA probably encodes telokin, which is the carboxyl terminus of smooth muscle myosin light chain kinase. mRNAs with identical lengths were also detected in bovine aorta. 相似文献
996.
997.
998.
999.
1000.