全文获取类型
收费全文 | 19603篇 |
免费 | 1013篇 |
国内免费 | 27篇 |
出版年
2023年 | 163篇 |
2022年 | 351篇 |
2021年 | 722篇 |
2020年 | 421篇 |
2019年 | 453篇 |
2018年 | 662篇 |
2017年 | 619篇 |
2016年 | 805篇 |
2015年 | 919篇 |
2014年 | 1170篇 |
2013年 | 1614篇 |
2012年 | 1708篇 |
2011年 | 1485篇 |
2010年 | 869篇 |
2009年 | 768篇 |
2008年 | 891篇 |
2007年 | 872篇 |
2006年 | 727篇 |
2005年 | 664篇 |
2004年 | 539篇 |
2003年 | 457篇 |
2002年 | 423篇 |
2001年 | 347篇 |
2000年 | 315篇 |
1999年 | 289篇 |
1998年 | 114篇 |
1997年 | 86篇 |
1996年 | 89篇 |
1995年 | 88篇 |
1994年 | 67篇 |
1993年 | 67篇 |
1992年 | 174篇 |
1991年 | 158篇 |
1990年 | 133篇 |
1989年 | 109篇 |
1988年 | 143篇 |
1987年 | 116篇 |
1986年 | 100篇 |
1985年 | 101篇 |
1984年 | 93篇 |
1983年 | 63篇 |
1982年 | 46篇 |
1981年 | 57篇 |
1980年 | 44篇 |
1979年 | 65篇 |
1978年 | 44篇 |
1977年 | 51篇 |
1976年 | 38篇 |
1975年 | 37篇 |
1974年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Besides vobtusine and vobtusine-lactone, deoxyvobtusine was isolated from the leaves of Voacanga grandifolia (Miq. Rolfe. Spectral and chemical evi 相似文献
3.
4.
5.
Shailesh Kumar Atma P. Dwivedi Vivek Kr. Kashyap A.K. Saxena A.K. Dwivedi Ranjana Srivastava Devi P. Sahu 《Bioorganic & medicinal chemistry letters》2013,23(8):2404-2407
Synthesis of a library of novel trans 6-methoxy-1,1-dimethyl-2-phenyl-3-aryl-2,3-dihydro-1H-inden-4-yloxy alkyl amines and their antimycobacterial activity against drug sensitive and multidrug resistant strains of Mycobacterium tuberculosis have been reported. All the new compounds in the series exhibited MIC between 1.56 and 6.25 μg/ml. Two compounds 1i and 1j with low MIC and low cytotoxicity showed significant reduction in CFU in infected mouse macrophages at 1× MIC concentration. The compound 1i inhibited the growth of M. tuberculosis in mice at 100 mg/kg dose with 1.35 log10 reduction of CFU in lungs tissue and was active against non-replicating Mycobacterium tuberculosis under anaerobic condition. 相似文献
6.
Cerebellar granule cells (CGNs) are one of many neurons that express phasic and tonic GABAergic conductances. Although it is well established that Golgi cells (GoCs) mediate phasic GABAergic currents in CGNs, their role in mediating tonic currents in CGNs (CGN-Itonic) is controversial. Earlier studies suggested that GoCs mediate a component of CGN-Itonic that is present only in preparations from immature rodents. However, more recent studies have detected a GoC-dependent component of CGN-Itonic in preparations of mature rodents. In addition, acute exposure to ethanol was shown to potentiate the GoC component of CGN-Itonic and to induce a parallel increase in spontaneous inhibitory postsynaptic current frequency at CGNs. Here, we tested the hypothesis that these effects of ethanol on GABAergic transmission in CGNs are mediated by inhibition of the Na+/K+-ATPase. We used whole-cell patch-clamp electrophysiology techniques in cerebellar slices of male rats (postnatal day 23–30). Under these conditions, we reliably detected a GoC-dependent component of CGN-Itonic that could be blocked with tetrodotoxin. Further analysis revealed a positive correlation between basal sIPSC frequency and the magnitude of the GoC-dependent component of CGN-Itonic. Inhibition of the Na+/K+-ATPase with a submaximal concentration of ouabain partially mimicked the ethanol-induced potentiation of both phasic and tonic GABAergic currents in CGNs. Modeling studies suggest that selective inhibition of the Na+/K+-ATPase in GoCs can, in part, explain these effects of ethanol. These findings establish a novel mechanism of action of ethanol on GABAergic transmission in the central nervous system. 相似文献
7.
S Kumar M Antony N K Mehrotra 《Biochemical and biophysical research communications》1984,125(3):967-973
Single cutaneous application of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) increased epidermal oxidised glutathione reductase activity in adult mouse by almost 100%. Pretreatment of animals with vitamin A for a week resulted in 75% inhibition of TPA induced change in the enzyme activity which remained unaffected in skin treated with vitamin A alone. This biochemical change in skin induced by TPA and modulated by vitamin A has been discussed in relation to epidermal hyperplasia. 相似文献
8.
Tubulin subunit carboxyl termini determine polymerization efficiency 总被引:21,自引:0,他引:21
Cleavage of tubulin by subtilisin removes a small (Mr less than 2000) fragment from the C-terminal end of both alpha and beta subunits. The resulting protein is much reduced in negative charge. The cleaved, less acidic protein retains its competence to polymerize in a GTP-dependent and cold-, GDP-, and podophyllotoxin-sensitive manner and assembles into sheets or bundles of twisted filaments. The critical concentration for polymerization of the cleaved protein is about 50-fold lower than that for intact tubulin. It is proposed that the C termini of the subunits normally impede polymerization. 相似文献
9.
J Shobha B Bhattacharyya D Balasubramanian 《Journal of biochemical and biophysical methods》1989,18(4):287-295
Enhancement of the fluorescence intensity of colchicine occurs in media of low polarity and appreciable viscosity; this is suggested to be the basis of the intensification of its fluorescence when it is bound to and immobilized in tubulin. We show here that the tubulin-bound fluorescence features of colchicine are largely reconstructed upon solubilizing it in chosen micellar aggregates that offer optimal polarities and microviscosities. Triton X-100 and bile salt micelles intensify the colchicine emission but the maximal effects are obtained with tetrameric aggregates of the peptide melittin. Estimates of the polarity, microviscosity and binding-site dimensions of colchicine are obtained using this mimetic approach. Our results suggest that well chosen micellar systems act as good models to reconstruct and analyze the spectral properties of molecules immobilized in their binding sites. 相似文献
10.
A new brain protein is described which forms an insoluble complex with tubulin, with concomitant stoichiometric hydrolysis of GTP. The complex contains a maximum of one tubulin-binding protein (MW 52,500) per two tubulin dimers. The tubulin-binding protein (TBP) does not compete with colchicine, but in the presence of microtubule-associated proteins tubulin appeared less accessible to it. Proteins such as TBP might sequester tubulin and thereby function either to inhibit indiscriminate polymerization, or to promote ordered nucleation by maintaining high local concentrations. 相似文献