全文获取类型
收费全文 | 7912篇 |
免费 | 713篇 |
国内免费 | 1篇 |
专业分类
8626篇 |
出版年
2022年 | 57篇 |
2021年 | 143篇 |
2020年 | 70篇 |
2019年 | 85篇 |
2018年 | 98篇 |
2017年 | 100篇 |
2016年 | 157篇 |
2015年 | 300篇 |
2014年 | 363篇 |
2013年 | 471篇 |
2012年 | 526篇 |
2011年 | 520篇 |
2010年 | 338篇 |
2009年 | 326篇 |
2008年 | 403篇 |
2007年 | 422篇 |
2006年 | 405篇 |
2005年 | 372篇 |
2004年 | 345篇 |
2003年 | 334篇 |
2002年 | 303篇 |
2001年 | 93篇 |
2000年 | 98篇 |
1999年 | 101篇 |
1998年 | 87篇 |
1997年 | 71篇 |
1996年 | 58篇 |
1995年 | 69篇 |
1994年 | 67篇 |
1993年 | 70篇 |
1992年 | 75篇 |
1991年 | 57篇 |
1990年 | 73篇 |
1989年 | 69篇 |
1988年 | 53篇 |
1987年 | 66篇 |
1986年 | 58篇 |
1985年 | 53篇 |
1984年 | 69篇 |
1983年 | 65篇 |
1982年 | 64篇 |
1981年 | 51篇 |
1980年 | 52篇 |
1979年 | 45篇 |
1978年 | 57篇 |
1976年 | 44篇 |
1974年 | 58篇 |
1973年 | 45篇 |
1971年 | 50篇 |
1970年 | 43篇 |
排序方式: 共有8626条查询结果,搜索用时 15 毫秒
1.
2.
Bharat Lagu John M. Wetzel Carlos Forray Michael A. Patane Mark G. Bock 《Bioorganic & medicinal chemistry letters》2000,10(24)
The binding affinities and selectivities of antagonists Figure 1 and Scheme 2 for the α1A-adrenoceptor are dependent on the stereochemical orientation of the groups at the C-4 and C-5 positions of the oxazolidinone ring. The unambiguous assignment of the relative and absolute configurations of the diastereomers of SNAP 7915 (Figure 1 and Scheme 2) is reported. 相似文献
3.
4.
5.
Composition and peptide maps of cross-linked human choriogonadotropin-receptor complexes on porcine granulosa cells 总被引:4,自引:0,他引:4
Radioiodinated human choriogonadotropin was affinity-cross-linked with a cleavable (nondisulfide) homobifunctional reagent to the hormone receptor on porcine granulosa cells and the solubilized sample was electrophoresed. Cross-linked samples revealed four additional bands of slower electrophoretic mobility in addition to the hormone alpha, beta, and alpha beta dimer bands. The four bands corresponded to masses of 68, 74, 102, and 136 kDa whereas the alpha beta dimer band corresponded to 50 kDa. Formation of the four bands requires the 125I-hormone to bind specifically to the receptor with subsequent cross-linking. Binding can be prevented by excess of native hormone but not by follitropin. A monofunctional analog of the cross-linking reagent failed to produce the four bands. They were also produced by cross-linking Triton X-100-solubilized hormone-receptor complexes. Reagent concentration-dependent cross-linking revealed that their formation was sequential; smaller complexes formed first and then larger ones. When gels of the cross-linked sample were treated with reagents that cleave covalent cross-links and then electrophoresed in a second dimension gel, 18-, 24-, 28-, and 34-kDa components were released, in addition to the alpha and beta subunits of the native hormone. Simultaneous peptide mapping of the cross-linked complexes in the gel matrix with Staphylococcus V8 protease or papain revealed progressive proteolysis to generate terminal fragments of 30 or 27 kDa, respectively. These fragments were unique to and commonly present in the 74-, 102-, and 136-kDa hormone-receptor complexes but were not produced by proteolysis of the cross-linked human choriogonadotropin (hCG) alpha beta dimer or the hCG alpha subunit. Apparently, the radioactively labeled segment(s) of the alpha subunit of 125I-hCG was cross-linked to the 24-kDa component. The results demonstrate the protein nature of the receptor and suggest that 125I-hCG was initially cross-linked to the 24-kDa component to generate the 74-kDa complex, then the 28- and 34-kDa components were sequentially cross-linked to the 24-kDa component in the 74-kDa complex to generate the 102- and 134-kDa complexes. 相似文献
6.
Pinealectomy or radical sham pinealectomy were performed on adult golden-mantled ground squirrels,Spermophilus (=Citellus) lateralis, approximately 1 month prior to the date of normal winter emergence. The first hibernatory period and subsequent active season were not different in either of the operated groups from intact animals. However, although the initiation of the second hibernatory period was not affected in the pinealectomized animals, this group failed to show the progressive increase in the length of heterothermic bouts that is characteristic of normal hibernation. Also, terminal arousal occurred approximately 6 weeks earlier in the second year after pinealectomy. Male squirrels showed a corresponding time compression in their annual gonadal cycle, as was assessed by testicular state.These results suggest that the pineal gland of the golden-mantled ground squirrel is involved in the expression of the annual hibernatory cycle. In the absence of the pineal gland the adult of this species is unable to sustain the normal depth and duration of hibernation in the second over-wintering period following pinealectomy.We have carried out additional experiments with young, laboratory-bornS. lateralis and with field-caught, adultS. richardsonii. The results of these studies also are described in this paper.Presented at the Ninth International Congress of Biometeorology, 23 Sept – 1 Oct 1981, Osnabrück and Hohenheim, FRG. 相似文献
7.
8.
9.
10.