全文获取类型
收费全文 | 56175篇 |
免费 | 5254篇 |
国内免费 | 33篇 |
出版年
2022年 | 289篇 |
2021年 | 767篇 |
2020年 | 503篇 |
2019年 | 602篇 |
2018年 | 768篇 |
2017年 | 690篇 |
2016年 | 1260篇 |
2015年 | 2096篇 |
2014年 | 2320篇 |
2013年 | 3031篇 |
2012年 | 3584篇 |
2011年 | 3670篇 |
2010年 | 2343篇 |
2009年 | 1977篇 |
2008年 | 2992篇 |
2007年 | 3045篇 |
2006年 | 2750篇 |
2005年 | 2833篇 |
2004年 | 2751篇 |
2003年 | 2588篇 |
2002年 | 2574篇 |
2001年 | 909篇 |
2000年 | 804篇 |
1999年 | 848篇 |
1998年 | 781篇 |
1997年 | 614篇 |
1996年 | 557篇 |
1995年 | 518篇 |
1994年 | 499篇 |
1993年 | 472篇 |
1992年 | 623篇 |
1991年 | 565篇 |
1990年 | 513篇 |
1989年 | 491篇 |
1988年 | 500篇 |
1987年 | 494篇 |
1986年 | 417篇 |
1985年 | 507篇 |
1984年 | 506篇 |
1983年 | 436篇 |
1982年 | 494篇 |
1981年 | 406篇 |
1980年 | 379篇 |
1979年 | 368篇 |
1978年 | 390篇 |
1977年 | 336篇 |
1976年 | 307篇 |
1975年 | 297篇 |
1974年 | 333篇 |
1973年 | 317篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Effects of Δ8- and Δ9-tetrahydrocannabinol (Δ8- and Δ9-THC) on three experimentally induced seizure models, i.e., audiogenic seizure (AS) test, maximal electroshock seizure (MES) test and pentylenetetrazol (PTZ)-induced seizure test were determined in the audiogenic rat. Both tetrahydrocannabinols possess a dose-related anticonvulsant effect against AS, MES and PTZ-induced maximal seizure. Although anticonvulsant potencies do not significantly differ, Δ8THC is three times more neurotoxic than Δ9THC. In addition, both THC's are without effect on minimal seizure and lethality induced by PTZ. Furthermore, the low protective indexes (TD50/ED50) determined in this study suggest that Δ8 and Δ9 THC may have poor therapeutic potentials as antiepileptic drugs. 相似文献
113.
114.
115.
116.
117.
A 14 kDa polypeptide in rat ileal cytosol has been identified as the major intestinal cytosolic bile acid-binding protein (I-BABP) by photoaffinity labeling with the radiolabeled 7,7-azo derivative of taurocholate (7,7-azo-TC). To further characterize I-BABP, the protein was purified by lysylglycocholate Sepharose 4B affinity and DE-52 anion-exchange chromatography. The purified I-BABP contained a single 14 kDa band on SDS-PAGE. The 14 kDa protein showed a 26-fold increase in binding affinity for [3H]7,7-azo-TC compared to cytosolic protein. Immunoblotting of protein fractions separated by affinity chromatography showed that neither liver fatty acid binding protein (L-FABP) nor intestinal fatty acid binding protein (I-FABP) bind to the affinity column and that the 14 kDa protein which bound to the column and was subsequently eluted with detergent did not cross-react with anti-L-FABP or anti-I-FABP. The 14 kDa protein labeled with [3H]7,7-azo-TC was radioimmunoprecipitated from cytosol by rabbit antiserum raised against purified I-BABP. I-BABP was shown to have a blocked N-terminus; however, its mixed internal sequence generated from cyanogen bromide-cleaved protein and amino acid composition indicated that it was related to (although clearly distinct from) both I-FABP and L-FABP. These studies have isolated a 14 kDa bile acid-binding protein from rat ileal cytosol which is immunologically and biochemically distinct from I-FABP and L-FABP. 相似文献
118.
Energy calculations have been carried out on high-symmetry cuboctahedral Ni-Al nanoalloy clusters, of varying composition, with the interatomic interactions modelled by the Gupta many-body potential. Relaxations of cuboctahedral fragments cut from the bulk lattice of Ni3Al, with 13-561 atoms, were undertaken, as were relaxations of high symmetry clusters with 55 and 147 atoms. The lowest energy isomers were found to be dominated by three factors: the tendency toward mixing due to the favourable energy of mixing, ΔmixE; the size difference between nickel and aluminium; and the higher cohesive and surface energy of nickel compared to aluminium. The latter two factors favour Al-segregation to the surface. The most stable Ni:Al composition approaches 3:1 for larger clusters. 相似文献
119.