全文获取类型
收费全文 | 127390篇 |
免费 | 4470篇 |
国内免费 | 820篇 |
出版年
2021年 | 377篇 |
2019年 | 353篇 |
2018年 | 12158篇 |
2017年 | 10938篇 |
2016年 | 8015篇 |
2015年 | 1589篇 |
2014年 | 1380篇 |
2013年 | 1654篇 |
2012年 | 5891篇 |
2011年 | 14321篇 |
2010年 | 12956篇 |
2009年 | 9163篇 |
2008年 | 11146篇 |
2007年 | 12705篇 |
2006年 | 1577篇 |
2005年 | 1750篇 |
2004年 | 2195篇 |
2003年 | 2248篇 |
2002年 | 1902篇 |
2001年 | 1236篇 |
2000年 | 1121篇 |
1999年 | 881篇 |
1998年 | 517篇 |
1997年 | 463篇 |
1996年 | 430篇 |
1995年 | 387篇 |
1994年 | 377篇 |
1993年 | 410篇 |
1992年 | 747篇 |
1991年 | 712篇 |
1990年 | 667篇 |
1989年 | 702篇 |
1988年 | 613篇 |
1987年 | 644篇 |
1986年 | 511篇 |
1985年 | 594篇 |
1984年 | 520篇 |
1983年 | 431篇 |
1982年 | 441篇 |
1981年 | 394篇 |
1980年 | 356篇 |
1979年 | 458篇 |
1978年 | 404篇 |
1977年 | 363篇 |
1976年 | 329篇 |
1975年 | 357篇 |
1974年 | 413篇 |
1973年 | 380篇 |
1972年 | 566篇 |
1971年 | 569篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
123.
J K Skipper F I Davidson D F Smith T H Hamilton 《The Journal of biological chemistry》1985,260(9):5399-5405
Conditions are defined which permit analysis of estrogen receptors from the mammalian uterus by polyacrylamide gel electrophoresis, thereby solving a longstanding problem encountered in previous attempts at such analysis, namely the failure of a large portion of the receptor population to enter such gels. A paramount requirement for entry of the estrogen-receptor complex into polyacrylamide gels is its maintenance in an untransformed state which does not form aggregates that are excluded from these gels. Of the multiple estrogen-binding proteins separated, only one (relative mobility of 0.5-0.6) possessed the definitive characteristics of the classical estrogen receptor. The inclusion of molybdate in extraction buffers selectively enhanced receptor recovery and facilitated its separation. Moreover, the estrogen-receptor complex so resolved is separated from other types of estrogen-binding proteins present in the uterine cytosol. These findings show that the molybdate-stabilized estrogen receptor exists in a single discrete form, but otherwise exhibits multiple forms that are probably artifactual. Electrophoresis in discontinuous buffers, but not in a continuous buffer system, promoted aggregate formation. This finding has implications concerning the subunit structure of the untransformed receptor. 相似文献
124.
125.
Mingyue Wang Pranab K Mukherjee Jyotsna Chandra Ali Abdul Lattif Thomas S McCormick Mahmoud A Ghannoum 《BMC microbiology》2008,8(1):31
Background
We have previously shown that supernatant from Candida albicans (CA) culture contains a Secretory Interleukin (IL)-12 Inhibitory Factor (CA-SIIF), which inhibits IL-12 production by human monocytes. However, the effect of CA-SIIF on secretion of other cytokines by monocytes is unknown, and detailed characterization of this factor has not been performed. 相似文献126.
Dana M. Bergstrom George R. Stewart Patricia M. Selkirk Susanne Schmidt 《Oecologia》2002,130(2):309-314
'15N signatures of fossil peat were used to interpret past ecosystem processes on tectonically active subantarctic Macquarie Island. By comparing past vegetation reconstructed from the fossil record with present-day vegetation analogues, our evidence strongly suggests that changes in the '15N signatures of fossil peat at this location reflect mainly past changes in the proportion of plant nitrogen derived from animal sources. Associated with uplift above sea level over the past 8,500 years, fossil records in two peat deposits on the island chronicle a change from coastal vegetation with fur and elephant seal disturbance to the existing inland herbfield. Coupled with this change are synchronous changes in the '15N signatures of peat layers. At two sites 15N-enriched peat '15N signatures of up to +17 were associated with a high abundance of pollen of the nitrophile Callitriche antarctica (Callitrichaceae). At one site fossil seal hair was also associated with enriched peat '15N. Less 15N enriched '15N signatures (e.g. -1.9 to +3.9) were measured in peat layers which lacked animal associated C. antarctica and Acaena spp. Interpretation of a third peat profile indicates continual occupation of a ridge site by burrowing petrels for most of the Holocene. We suggest that 15N signatures of fossil peat remained relatively stable with time once deposited, providing a significant new tool for interpreting the palaeoecology. 相似文献
127.
Colin K.W. Watts Robert L. Sutherland 《Biochemical and biophysical research communications》1984,120(1):109-115
Saturation and competitive binding analyses demonstrated the presence of a high affinity (KD = 0.92 nM), specific antiestrogen binding site (AEBS) in rat liver microsomes and at least 75% of total liver AEBS was recovered in this fraction. When microsomes were further separated into smooth and rough fractions, AEBS was concentrated in the latter. Subsequent dissociation of ribosomes from the rough membranes revealed that AEBS was associated with the membrane and not the ribosomal fraction. Antiestrogen binding activity could not be extracted from membranes with 1 M KCl or 0.5 M acetic acid but could be solubilized with sodium cholate. These data indicate that AEBS is an integral membrane component of the rough microsomal fraction of rat liver. 相似文献
128.
F F Smith J R Mertz I Krebs L L Tres C B Chae Z Zakeri J Engelhardt D Hoover M Tenniswood A L Kierszenbaum 《Molecular reproduction and development》1992,33(4):363-372
We have previously reported that a heterodimeric protein secreted by rat Sertoli cells is antigenically related to a protein associated with outer dense fibers of the sperm tail. Therefore, we have explored the possibility that Sertoli and spermatogenic cells express a similar gene encoding a homologous protein. A Sertoli cell heterodimeric protein cDNA probe recognizes specific mRNA in pachytene and round spermatids fractionated by centrifugal elutriation; however, this specific mRNA was less prominent than in cultured Sertoli cells. In agreement with these observations, in situ hybridization experiments show that Sertoli cells are predominantly engaged in active heterodimeric protein mRNA synthesis, while meiotic prophase spermatocytes and spermatids also show significant but less abundant specific mRNA. Immunoblotting experiments demonstrate that, while Sertoli cells synthesize a heterodimeric protein consisting of two disulfide-linked components with molecular masses of 45 and 35 kD, both primary spermatocytes and round spermatids synthesize single 30 kD monomers not associated by disulfide linkage but recognized by antisera to Sertoli cell heterodimeric protein. Immunoblotting and immunogold electron microscopic studies show that antisera to Sertoli cell heterodimeric protein recognize a protein associated with outer dense fibers. This immunoreactivity was abolished by a 5-min pronase treatment, without affecting the integrity of outer dense fibers. Results of this study and previous studies demonstrate that both Sertoli and spermatogenic cells express a similar gene and that an antigenically related product encoded by this gene becomes associated with outer dense fibers during their assembly at spermiogenesis. 相似文献
129.
130.