全文获取类型
收费全文 | 866篇 |
免费 | 39篇 |
专业分类
林业 | 94篇 |
农学 | 12篇 |
基础科学 | 1篇 |
87篇 | |
综合类 | 113篇 |
农作物 | 14篇 |
水产渔业 | 66篇 |
畜牧兽医 | 486篇 |
园艺 | 17篇 |
植物保护 | 15篇 |
出版年
2021年 | 15篇 |
2020年 | 10篇 |
2019年 | 20篇 |
2018年 | 16篇 |
2017年 | 14篇 |
2016年 | 8篇 |
2015年 | 16篇 |
2014年 | 19篇 |
2013年 | 37篇 |
2012年 | 45篇 |
2011年 | 52篇 |
2010年 | 20篇 |
2009年 | 19篇 |
2008年 | 39篇 |
2007年 | 27篇 |
2006年 | 36篇 |
2005年 | 38篇 |
2004年 | 29篇 |
2003年 | 38篇 |
2002年 | 33篇 |
2001年 | 27篇 |
2000年 | 20篇 |
1999年 | 20篇 |
1998年 | 14篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 18篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 17篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1979年 | 7篇 |
1973年 | 8篇 |
1972年 | 9篇 |
1970年 | 6篇 |
1969年 | 5篇 |
1968年 | 7篇 |
1966年 | 6篇 |
1913年 | 6篇 |
1910年 | 6篇 |
1909年 | 6篇 |
排序方式: 共有905条查询结果,搜索用时 15 毫秒
71.
Genetics and phenogenetics of mitochondria 总被引:6,自引:0,他引:6
R P Wagner 《Science (New York, N.Y.)》1969,163(871):1026-1031
72.
The Vinca alkaloids vinblastine sulfate and vincrystine sulfate, which are mitotic poisons, inhibit RNA synthesis in human (HEp-2) cells cultured in vitro. Analyses of RNA synthesis by cells treated with these drugs by acrylamide gel electrophoresis show that 28s rRNA and to a lesser extent 18s rRNA are preferentially inhibited. The synthesis of tRNA is affected much less than that of rRNA. The present experiments suggest that the drugs inhibit both the synthesis and processing of the nucleolar RNA precursors of rRNA. An explanation is also given for previous reports that these alkaloids preferentially inhibit the synthesis of tRNA in animal cells in vitro. 相似文献
73.
Horowitz HS McLain SJ Sleight AW Druliner JD Gai PL Vankavelaar MJ Wagner JL Biggs BD Poon SJ 《Science (New York, N.Y.)》1989,243(4887):66-69
Evidence suggests that superconducting, orthorhombic YBa(2)Cu(3)O(6+x)+ (x greater, similar 0.5) is always produced by oxidation of the oxygen-deficient, tetragonal form (x less, similar 0.5) of this phase (commonly referred to as 123). A synthetic route whereby solution-derived, carbon-free precursors are decomposed at 650 degrees to 700 degrees C in inert atmosphere to yield tetragonal 123 is now available. Appropriate precursors include hydrated oxides derived from the hydrolysis of organometallic solutions and aqueous solution-derived hyponitrites. Subsequent oxidation of the tetragonal phase at 400 degrees C results in submicrometer particles of orthorhombic 123. Superconductivity (T(c) onset approximately 87 K) has been confirmed in these materials by both Meissner effect and specific-heat measurements. 相似文献
74.
The Australasian and Ivory Coast deep-sea microtektites have fission track ages of 0.71 and 1.09 million years, respectively. These ages are in good agreement with the ages of deposition of the microtektites determined from paleomagnetic data. Both the fission track ages and ages of deposition of the microtektites agree with the potassium/ argon and fission track ages of tektites from the respective tektite strewn fields. 相似文献
75.
The T cell coreceptors CD4 and CD8 both associate via their cytoplasmic tails with the N-terminus of the Src-family tyrosine kinase Lck. These interactions require zinc and are critical for T cell development and activation. We examined the folding and solution structures of ternary CD4-Lck-Zn2+ and CD8alpha-Lck-Zn2+ complexes. The coreceptor tails and the Lck N-terminus are unstructured in isolation but assemble in the presence of zinc to form compactly folded heterodimeric domains. The cofolded complexes have similar "zinc clasp" cores that are augmented by distinct structural elements. A dileucine motif required for clathrin-mediated endocytosis of CD4 is masked by Lck. 相似文献
76.
Excavations of a workshop and cemetery in the high Venezuelan Andes yielded winged artifacts made of serpentinite at various stages of finish. Serpentinites are unknown in the Venezuelan Andes, and the raw material was obtained from natural sources located in northern South American or possibly the Antilles, or by trade. 相似文献
77.
78.
The passage of large-sized herpesviral capsids through the nuclear lamina and the inner nuclear membrane to leave the nucleus requires a dissolution of the nuclear lamina. Here, we report on the functions of M50/p35, a beta-herpesviral protein of murine cytomegalovirus. M50/p35 inserts into the inner nuclear membrane and is aggregated by a second viral protein, M53/p38, to form the capsid docking site. M50/p35 recruits the cellular protein kinase C for phosphorylation and dissolution of the nuclear lamina, suggesting that herpesviruses target a critical element of nuclear architecture. 相似文献
79.
Walensky LD Kung AL Escher I Malia TJ Barbuto S Wright RD Wagner G Verdine GL Korsmeyer SJ 《Science (New York, N.Y.)》2004,305(5689):1466-1470
BCL-2 family proteins constitute a critical control point for the regulation of apoptosis. Protein interaction between BCL-2 members is a prominent mechanism of control and is mediated through the amphipathic alpha-helical BH3 segment, an essential death domain. We used a chemical strategy, termed hydrocarbon stapling, to generate BH3 peptides with improved pharmacologic properties. The stapled peptides, called "stabilized alpha-helix of BCL-2 domains" (SAHBs), proved to be helical, protease-resistant, and cell-permeable molecules that bound with increased affinity to multidomain BCL-2 member pockets. A SAHB of the BH3 domain from the BID protein specifically activated the apoptotic pathway to kill leukemia cells. In addition, SAHB effectively inhibited the growth of human leukemia xenografts in vivo. Hydrocarbon stapling of native peptides may provide a useful strategy for experimental and therapeutic modulation of protein-protein interactions in many signaling pathways. 相似文献
80.
Reinherz EL Tan K Tang L Kern P Liu J Xiong Y Hussey RE Smolyar A Hare B Zhang R Joachimiak A Chang HC Wagner G Wang J 《Science (New York, N.Y.)》1999,286(5446):1913-1921
The crystal structure of a complex involving the D10 T cell receptor (TCR), 16-residue foreign peptide antigen, and the I-Ak self major histocompatibility complex (MHC) class II molecule is reported at 3.2 angstrom resolution. The D10 TCR is oriented in an orthogonal mode relative to its peptide-MHC (pMHC) ligand, necessitated by the amino-terminal extension of peptide residues projecting from the MHC class II antigen-binding groove as part of a mini beta sheet. Consequently, the disposition of D10 complementarity-determining region loops is altered relative to that of most pMHCI-specific TCRs; the latter TCRs assume a diagonal orientation, although with substantial variability. Peptide recognition, which involves P-1 to P8 residues, is dominated by the Valpha domain, which also binds to the class II MHC beta1 helix. That docking is limited to one segment of MHC-bound peptide offers an explanation for epitope recognition and altered peptide ligand effects, suggests a structural basis for alloreactivity, and illustrates how bacterial superantigens can span the TCR-pMHCII surface. 相似文献