全文获取类型
收费全文 | 2486篇 |
免费 | 209篇 |
国内免费 | 4篇 |
出版年
2022年 | 25篇 |
2021年 | 49篇 |
2020年 | 18篇 |
2019年 | 19篇 |
2018年 | 24篇 |
2017年 | 21篇 |
2016年 | 55篇 |
2015年 | 107篇 |
2014年 | 123篇 |
2013年 | 119篇 |
2012年 | 185篇 |
2011年 | 184篇 |
2010年 | 107篇 |
2009年 | 85篇 |
2008年 | 122篇 |
2007年 | 106篇 |
2006年 | 119篇 |
2005年 | 98篇 |
2004年 | 115篇 |
2003年 | 101篇 |
2002年 | 88篇 |
2001年 | 78篇 |
2000年 | 85篇 |
1999年 | 59篇 |
1998年 | 31篇 |
1997年 | 24篇 |
1996年 | 22篇 |
1995年 | 13篇 |
1994年 | 22篇 |
1993年 | 8篇 |
1992年 | 31篇 |
1991年 | 44篇 |
1990年 | 22篇 |
1989年 | 37篇 |
1988年 | 30篇 |
1987年 | 47篇 |
1986年 | 29篇 |
1985年 | 36篇 |
1984年 | 28篇 |
1983年 | 19篇 |
1982年 | 16篇 |
1981年 | 13篇 |
1980年 | 7篇 |
1979年 | 22篇 |
1978年 | 15篇 |
1977年 | 18篇 |
1976年 | 8篇 |
1975年 | 12篇 |
1974年 | 15篇 |
1973年 | 9篇 |
排序方式: 共有2699条查询结果,搜索用时 15 毫秒
11.
George B. Stefano Erica Braham Patrick Finn Edward Aiello Michael K. Leung 《Cellular and molecular neurobiology》1987,7(2):209-219
1. This report further demonstrates that etorphine influences presynaptic dopamine release, which in turn centrally modulates peripheral cilioinhibition. 2. In older animals cilioinhibition has become enhanced due to a lack of responsiveness to endogenous opioids which results in greater dopamine release, causing a higher level of cilioinhibition as demonstrated by challenging the visceral ganglia with etorphine or destroying the dopaminergic component with 6-hydroxydopamine. 3. Only the central cilioinhibitory, not the peripheral inhibitory response, mechanism appears to be altered in older animals. Thus, the alteration appears in the central integrative mechanisms involved with regulating ciliary activity. 4. The KCl-stimulated release of dopamine is unaltered in both young and old organisms, whereas the opiate inhibition of the KCl-stimulated release of dopamine is reduced in older organisms. Thus, the aging-associated alteration is associated with a specific process. 5. The reduction of opioid influence and the resulting enhanced cilioinhibitory activity may make the organisms more susceptible to environmental stress. 相似文献
12.
13.
Stimulation of progesterone and prostaglandin E2 production by lipoxygenase metabolites of arachidonic acid 总被引:1,自引:0,他引:1
The role of several lipoxygenase metabolites of arachidonic acid in the action of luteinizing hormone-releasing hormone (LHRH) on ovarian hormone production was investigated. Like LHRH, treatment of rat granulosa cells with 5-HETE, 5-HPETE, 12-HETE, 15-HETE or 15-HPETE stimulated progesterone (P) and prostaglandin E2 (PGE2) production. 12-HEPE was most potent and stimulated P and PGE2 equally well. By contrast, 5-HETE stimulated P better than PGE2, while 15-HETE was a potent stimulator of PGE2 but not of P. Stimulation of P and PGE2 by LHRH or 12-O-tetradecanoylphorbol 13-acetate (TPA) was further augmented by several HETEs and HPETEs. Like protein kinase C, arachidonic acid metabolites appear to mediate the multiple actions of LHRH in the ovary. 相似文献
14.
15.
16.
17.
Biochemical and ultrastructural characterization of the 1,4-dihydropyridine receptor from rabbit skeletal muscle. Evidence for a 52,000 Da subunit 总被引:10,自引:0,他引:10
A T Leung T Imagawa B Block C Franzini-Armstrong K P Campbell 《The Journal of biological chemistry》1988,263(2):994-1001
The 1,4-dihydropyridine receptor purified from rabbit skeletal muscle contains four polypeptide components of 175,000 Da (nonreduced)/150,000 Da (reduced), 170,000, 52,000, and 32,000 Da (Leung, A. T., Imagawa, T., and Campbell, K. P. (1987) J. Biol. Chem. 262, 7943-7946). A monoclonal antibody specific to the 52,000-Da polypeptide component of the dihydropyridine receptor has been produced and used in immunoprecipitation and immunoblotting experiments to demonstrate that the 52,000-Da polypeptide is an integral subunit of the purified dihydropyridine receptor. Peptide mapping experiments with 32P-labeled dihydropyridine receptor have also demonstrated that the 52,000-Da polypeptide is distinct from and not a proteolytic fragment of the 170,000-Da subunit. Densitometric scanning of Coomassie Blue-stained sodium dodecyl sulfate-polyacrylamide gels of the purified dihydropyridine receptor has demonstrated that the 52,000-Da polypeptide exists in a 1:1 stoichiometric ratio with the 170,000-, 175,000/150,000-, and 32,000-Da subunits of the dihydropyridine receptor. Electron microscopy of the freeze-dried, rotary-shadowed dihydropyridine receptor has shown that the preparation contains a homogeneous population of 16 x 22-nm ovoidal particles large enough to contain all four polypeptides of the dihydropyridine receptor. The particles have two distinct components of similar size which may represent the location in the molecule of the two larger subunits. 相似文献
18.
19.
The alpha-like globin gene cluster in rabbits contains embryonic zeta-
globin genes, an adult alpha-globin gene, and theta-globin genes of
undetermined function. The basic arrangement of genes, deduced from
analysis of cloned DNA fragments, is 5'-zeta 0-zeta 1-alpha 1-theta 1- zeta
2-zeta 3-theta 2-3'. However, the pattern of restriction fragments
containing zeta- and theta-globin genes varies among individual rabbits.
Analysis of BamHI fragments of genomic DNA from 24 New Zealand white
rabbits revealed eight different patterns of fragments containing
zeta-globin genes. The large BamHI fragments containing genes zeta 0 and
zeta 1 are polymorphic in length, whereas a 1.9-kb fragment containing the
zeta 2 gene and the 3.5-kb fragment containing the zeta 3 gene do not vary
in size. In contrast to this constancy in the size of the restriction
fragments, the copy number of the zeta 2 and zeta 3 genes does vary among
different rabbits. No length polymorphism was detected in the BamHI
fragments containing the theta-globin genes, but again the copy number
varies for restriction fragments containing the theta 2 gene. The alpha 1-
and theta 1-globin genes are located in a nonpolymorphic 7.2-kb BamHI
fragment. The combined data from hybridization with both zeta and theta
probes shows that the BamHI cleavage pattern does not vary within the
region 5'-alpha 1-theta 1- zeta 2-zeta 3-theta 2-3', but the pattern
genomic blot-hybridization patterns for the progeny of parental rabbits
with different zeta-globin gene patterns shows that the polymorphic
patterns are inherited in a Mendelian fashion. Two different haplotypes
have been mapped based on the genomic blot-hybridization data. The
variation in the alpha-like globin gene cluster in the rabbit population
results both from differences in the copy number of the duplication block
containing the zeta-zeta-theta gene set and from the presence or absence of
polymorphic BamHI sites.
相似文献
20.
K Leung K E Kim R A Maurer T D Landefeld 《Molecular endocrinology (Baltimore, Md.)》1988,2(3):272-276
Cyclic changes in the production of the pituitary gonadotrophic hormones, LH and FSH are essential events in the maintenance of the reproductive system of female mammals. While studies have examined changes in the secretion of LH and FSH during the estrous cycle and demonstrated the importance of these hormones in regulation of ovarian development and gametogenesis, considerably less is known concerning the regulation of the biosynthesis of these hormones. Although initial studies have examined changes in LH subunit mRNA concentrations during the rat and ovine estrous cycles, no information concerning the physiological regulation of FSH beta mRNA concentrations has been available. In the present study we have examined the relationship between pituitary concentrations of LH and FSH subunit mRNAs and the serum concentrations of these gonadotropins. The results demonstrate a very different pattern of change for FSH beta subunit mRNA than that observed for alpha and LH beta subunit mRNAs. In fact, FSH beta mRNA concentration decline substantially during the preovulatory period, reaching minimal values at a time when alpha and LH beta mRNA levels are near maximal. Furthermore, this decline in FSH beta mRNA amounts occurs when serum FSH concentrations are maximal. Thus, FSH beta mRNA concentrations follow a very different pattern than that of serum FSH. In contrast, LH beta mRNA and serum LH concentrations tend to increase at the same time. These findings provide evidence that concentrations of LH beta and FSH beta mRNAs are likely regulated by different mechanisms. 相似文献