全文获取类型
收费全文 | 5344篇 |
免费 | 300篇 |
国内免费 | 51篇 |
专业分类
化学 | 3872篇 |
晶体学 | 46篇 |
力学 | 148篇 |
综合类 | 2篇 |
数学 | 631篇 |
物理学 | 996篇 |
出版年
2023年 | 48篇 |
2022年 | 65篇 |
2021年 | 86篇 |
2020年 | 109篇 |
2019年 | 112篇 |
2018年 | 84篇 |
2017年 | 45篇 |
2016年 | 170篇 |
2015年 | 153篇 |
2014年 | 178篇 |
2013年 | 286篇 |
2012年 | 422篇 |
2011年 | 466篇 |
2010年 | 209篇 |
2009年 | 199篇 |
2008年 | 348篇 |
2007年 | 311篇 |
2006年 | 304篇 |
2005年 | 266篇 |
2004年 | 239篇 |
2003年 | 181篇 |
2002年 | 140篇 |
2001年 | 103篇 |
2000年 | 102篇 |
1999年 | 60篇 |
1998年 | 61篇 |
1997年 | 36篇 |
1996年 | 75篇 |
1995年 | 54篇 |
1994年 | 54篇 |
1993年 | 49篇 |
1992年 | 46篇 |
1991年 | 38篇 |
1990年 | 31篇 |
1989年 | 23篇 |
1988年 | 29篇 |
1987年 | 25篇 |
1986年 | 25篇 |
1985年 | 51篇 |
1984年 | 33篇 |
1983年 | 32篇 |
1982年 | 26篇 |
1981年 | 39篇 |
1980年 | 31篇 |
1979年 | 25篇 |
1978年 | 32篇 |
1977年 | 27篇 |
1976年 | 21篇 |
1975年 | 27篇 |
1974年 | 37篇 |
排序方式: 共有5695条查询结果,搜索用时 0 毫秒
61.
62.
Wataru Ueda Damian Vitry Tomokazu Kato Nobufumi Watanabe Yusuke Endo 《Research on Chemical Intermediates》2006,32(3-4):217-233
Mo-V-O-based complex metal oxide catalysts were synthesized hydrothermally for the first time, characterized structurally and tested in the selective oxidation of propane to acrylic acid, and the results obtained were compared on the basis of catalyst crystal structures in order to clarify key aspects of alkane selective oxidation over multifunctional metal oxide catalysts. The catalysts tested were black solids of rod-shaped crystals, which had a layer structure in the direction of fiber axis and various high dimensional arrangements of metal octahedra in the cross-section plane. A strong dependency on the octahedra arrangements and a facet dependency were observed, and the roles of metal elements in the course of selective oxidation of propane were clarified by comparing the catalytic performance of various Mo-V-O-based catalysts. We discuss the multi-functional character derived from high dimensional structures of the catalysts and mechanism of the selective oxidation of propane. 相似文献
63.
Gaucher disease-associated glucocerebrosidases show mutation-dependent chemical chaperoning profiles
Sawkar AR Adamski-Werner SL Cheng WC Wong CH Beutler E Zimmer KP Kelly JW 《Chemistry & biology》2005,12(11):1235-1244
Gaucher disease is a lysosomal storage disorder caused by deficient glucocerebrosidase activity. We have previously shown that the cellular activity of the most common Gaucher disease-associated glucocerebrosidase variant, N370S, is increased when patient-derived cells are cultured with the chemical chaperone N-nonyl-deoxynojirimycin. Chemical chaperones stabilize proteins against misfolding, enabling their trafficking from the endoplasmic reticulum. Herein, the generality of this therapeutic strategy is evaluated with other glucocerebrosidase variants and with additional candidate chemical chaperones. Improved chemical chaperones are identified for N370S glucocerebrosidase. Moreover, we demonstrate that G202R, a glucocerebrosidase variant that is known to be retained in the endoplasmic reticulum, is also amenable to chemical chaperoning. The L444P variant is not chaperoned by any of the active site-directed molecules tested, likely because this mutation destabilizes a domain distinct from the catalytic domain. 相似文献
64.
Wong KL Bitter M Hammett GW Heidbrink W Hendel H Kaita R Scott S Strachan JD Tait G Bell MG Budny R Bush C Chan A Coonrod J Efthimion PC England AC Eubank HP Fredrickson E Furth HP Goldston RJ Grek B Grisham L Hawryluk RJ Hill KW Johnson D Kamperschroer J Kugel H Ma C Mansfield D Manos D McCune DC McGuire K Medley SS Mueller D Nieschmidt E Owens DK Paré VK Park H Ramsey A Rasmussen D Roquemore AL Schivell J Sesnic S Taylor G Williams MD Zarnstorff MC 《Physical review letters》1985,55(23):2587-2590
65.
66.
67.
68.
Wong DM Greenblatt HM Dvir H Carlier PR Han YF Pang YP Silman I Sussman JL 《Journal of the American Chemical Society》2003,125(2):363-373
Acetylcholinesterase (AChE) inhibitors improve the cognitive abilities of Alzheimer patients. (-)-Huperzine A [(-)-HupA], an alkaloid isolated from the club moss, Huperzia serrata, is one such inhibitor, but the search for more potent and selective drugs continues. Recently, alkylene-linked dimers of 5-amino-5,6,7,8-tetrahydroquinolinone (hupyridone, 1a), a fragment of HupA, were shown to serve as more potent inhibitors of AChE than (-)-HupA and monomeric 1a. We soaked two such dimers, (S,S)-(-)-bis(10)-hupyridone [(S,S)-(-)-2a] and (S,S)-(-)-bis(12)-hupyridone [(S,S)-(-)-2b] containing, respectively, 10 and 12 methylenes in the spacer, into trigonal TcAChE crystals, and solved the X-ray structures of the resulting complexes using the difference Fourier technique, both to 2.15 A resolution. The structures revealed one HupA-like 1a unit bound to the "anionic" subsite of the active-site, near the bottom of the active-site gorge, adjacent to Trp84, as seen for the TcAChE/(-)-HupA complex, and the second 1a unit near Trp279 in the "peripheral" anionic site at the top of the gorge, both bivalent molecules thus spanning the active-site gorge. The results confirm that the increased affinity of the dimeric HupA analogues for AChE is conferred by binding to the two "anionic" sites of the enzyme. Inhibition data show that (-)-2a binds to TcAChE approximately 6-7- and > 170-fold more tightly than (-)-2b and (-)-HupA, respectively. In contrast, previous data for rat AChE show that (-)-2b binds approximately 3- and approximately 2-fold more tightly than (-)-2a and (-)-HupA, respectively. Structural comparison of TcAChE with rat AChE, as represented by the closely related mouse AChE structure (1maa.pdb), reveals a narrower gorge for rat AChE, a perpendicular alignment of the Tyr337 ring to the gorge axis, and its conformational rigidity, as a result of hydrogen bonding between its hydroxyl group and that of Tyr341, relative to TcAChE Phe330. These structural differences in the active-site gorge explain the switch in inhibitory potency of (-)-2a and 2b and the larger dimer/(-)-HupA potency ratios observed for TcAChE relative to rat AChE. The results offer new insights into factors affecting protein-ligand complementarity within the gorge and should assist the further development of improved AChE inhibitors. 相似文献
69.
Kim SY Saxena A Kwak G Fujiki M Kawakami Y 《Chemical communications (Cambridge, England)》2004,(5):538-539
Cooperative amplification of the C-F...Si weak interaction between side chains and the main chain was found to afford rigid rodlike helical polysilanes with a preferential screw sense. 相似文献
70.
Wong JW Maleknia SD Downard KM 《Journal of the American Society for Mass Spectrometry》2005,16(2):225-233
The calcium-dependent interaction of calmodulin and melittin is studied through the application of a radical probe approach in which solutions of the protein and peptide and protein alone are subjected to high fluxes of hydroxyl and other oxygen radicals on millisecond timescales. These radicals are generated by an electrical discharge within an electrospray ion source of a mass spectrometer. Condensation of the electrosprayed droplets followed by proteolytic digestion of both calmodulin and melittin has identified residues in both which participate in the interaction and/or are shielded from solvent within the protein complex. Consistent with other theoretical models and available experimental data, the tryptophan residue of melittin at position 19 is shown to be critical to the formation of the complex with the C-terminal domain of peptide enveloped by and protected from oxidation upon binding to the protein. Furthermore, the N-terminal domain (to residue 36) and tyrosine at position 99 in calmodulin are significantly protected from limited oxidation upon the binding of melittin while exposing the phenylalanine residue at position 92 of the flexible loop domain. The N-terminus (through residue 36) of calmodulin is shown to lie in closer proximity to the melittin helix than its C-terminal counterpart (residues 127-148) based upon the protection levels measured at reactive residues within these segments of the protein. 相似文献