全文获取类型
收费全文 | 10570篇 |
免费 | 832篇 |
国内免费 | 1029篇 |
专业分类
12431篇 |
出版年
2024年 | 145篇 |
2023年 | 198篇 |
2022年 | 485篇 |
2021年 | 641篇 |
2020年 | 477篇 |
2019年 | 562篇 |
2018年 | 506篇 |
2017年 | 331篇 |
2016年 | 442篇 |
2015年 | 673篇 |
2014年 | 781篇 |
2013年 | 786篇 |
2012年 | 989篇 |
2011年 | 913篇 |
2010年 | 495篇 |
2009年 | 493篇 |
2008年 | 577篇 |
2007年 | 461篇 |
2006年 | 402篇 |
2005年 | 341篇 |
2004年 | 268篇 |
2003年 | 215篇 |
2002年 | 156篇 |
2001年 | 132篇 |
2000年 | 109篇 |
1999年 | 150篇 |
1998年 | 89篇 |
1997年 | 103篇 |
1996年 | 64篇 |
1995年 | 58篇 |
1994年 | 54篇 |
1993年 | 45篇 |
1992年 | 52篇 |
1991年 | 44篇 |
1990年 | 43篇 |
1989年 | 31篇 |
1988年 | 27篇 |
1987年 | 19篇 |
1986年 | 27篇 |
1985年 | 21篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Three new phthalate acid derivatives, 2,12-diethyl-11-methylhexadecyl 2-ethyl-11-methylhexadecyl phthalate (1), 2-ethyldecyl 2-ethylundecyl phthalate (2), and bis(2-ethyldodecyl) phthalate (3), were isolated from seahorse, Hippocampus Kuda Bleeler, together with a known natural analog bis(2-ethylheptyl) phthalate (4). The structures of these compounds were elucidated mainly by means of the comprehensive analysis of their NMR spectroscopic data. The four phthalate derivatives showed dose-dependent cathepsin B inhibitions activities with IC(50) values of 0.13 mM (1), 0.21 mM (2), 0.18 mM (3), and 0.29 mM (4), respectively. 相似文献
22.
Boggiano C Jiang S Lu H Zhao Q Liu S Binley J Blondelle SE 《Biochemical and biophysical research communications》2006,347(4):909-915
Entry of human immunodeficiency virus type 1 (HIV-1) virion into host cells involves three major steps, each being a potential target for the development of entry inhibitors: gp120 binding to CD4, gp120-CD4 complex interacting with a coreceptor, and gp41 refolding to form a six-helix bundle. Using a D-amino acid decapeptide combinatorial library, we identified peptide dC13 as having potent HIV-1 fusion inhibitory activity, and effectively inhibiting infection by several laboratory-adapted and primary HIV-1 strains. While dC13 did not block binding of gp120 to CD4, nor disrupt the gp41 six-helix bundle formation, it effectively blocked the binding of an anti-CXCR4 monoclonal antibody and chemokine SDF-1alpha to CXCR4-expressing cells. However, because R5-using primary viruses were also neutralized, the antiviral activity of dC13 implies additional mode(s) of action. These results suggest that dC13 is a useful HIV-1 coreceptor antagonist for CXCR4 and, due to its biostability and simplicity, may be of value for developing a new class of HIV-1 entry inhibitors. 相似文献
23.
Chen Z Zheng Z Huang H Song Y Zhang X Ma J Wang B Zhang C Ju J 《Bioorganic & medicinal chemistry letters》2012,22(9):3332-3335
Three new mycophenolic acid derivatives, penicacids A-C (1-3), together with two known analogues, mycophenolic acid (MPA, 4) and 4'-hydroxy-MPA (5), were isolated from a fungus Penicillium sp. SOF07 derived from a South China Sea marine sediment. The structures of compounds 1-3 were elucidated on the basis of MS and NMR ((1)H, (13)C, HSQC and HMBC) data analyses and comparisons with the known compounds. Structure-activity relationship studies of compounds 1-5 focused on inosine-monophosphate dehydrogenase inhibition revealed that hydroxylation at C-4', methylation at C-7-OH, dual hydroxylation at C-2'/C-3' double bond of MPA diminished bioactivity whereas glucosyl hydroxylation at C-4' correlated to bioactivity comparable to that observed for MPA. 相似文献
24.
25.
Liu Siqi Wang Bo Li Xiaojing Pan Jingxian Qian Xuexue Yu Yahui Xu Ping Zhu Jian Xu Xiaofeng 《Plant Cell, Tissue and Organ Culture》2019,137(3):485-494
Plant Cell, Tissue and Organ Culture (PCTOC) - Callus is a remarkable regeneration tissue. The genes correlated with root development can be involved in regulating callus development in higher... 相似文献
26.
Liyuan Ma Qian Li Li Shen Xue Feng Yunhua Xiao Jiemeng Tao Yili Liang Huaqun Yin Xueduan Liu 《Journal of industrial microbiology & biotechnology》2016,43(10):1441-1453
Acidophilic microorganisms involved in uranium bioleaching are usually suppressed by dissolved fluoride ions, eventually leading to reduced leaching efficiency. However, little is known about the regulation mechanisms of microbial resistance to fluoride. In this study, the resistance of Acidithiobacillus ferrooxidans ATCC 23270 to fluoride was investigated by detecting bacterial growth fluctuations and ferrous or sulfur oxidation. To explore the regulation mechanism, a whole genome microarray was used to profile the genome-wide expression. The fluoride tolerance of A. ferrooxidans cultured in the presence of FeSO4 was better than that cultured with the S0 substrate. The differentially expressed gene categories closely related to fluoride tolerance included those involved in energy metabolism, cellular processes, protein synthesis, transport, the cell envelope, and binding proteins. This study highlights that the cellular ferrous oxidation ability was enhanced at the lower fluoride concentrations. An overview of the cellular regulation mechanisms of extremophiles to fluoride resistance is discussed. 相似文献
27.
Gang Tang Li-wei Qian Gao-feng Wei Hong-sheng Wang 《Computer methods in biomechanics and biomedical engineering》2013,16(3):275-283
Muscle force estimation (MFE) has become more and more important in exploring principles of pathological movement, studying functions of artificial muscles, making surgery plan for artificial joint replacement, improving the biomechanical effects of treatments and so on. At present, existing software are complex for professionals, so we have developed a new software named as concise MFE (CMFE). CMFE which provides us a platform to analyse muscle force in various actions includes two MFE methods (static optimisation method and electromyographic-based method). Common features between these two methods have been found and used to improve CMFE. A case studying the major muscles of lower limb of a healthy subject walking at normal speed has been presented. The results are well explained from the effect of the motion produced by muscles during movement. The development of this software can improve the accuracy of the motion simulations and can provide a more extensive and deeper insight in to muscle study. 相似文献
28.
29.
Androgen receptor binding to an androgen‐responsive element in the promoter of the Srsf4 gene inhibits its expression in mouse Sertoli cells 下载免费PDF全文
30.
Thomas M Davis Melanie E Shields Qian Zhang Denise Tombolato-Terzić Jeffrey L Bennetzen Ana C Pontaroli Hao Wang Qin Yao Phillip SanMiguel Kevin M Folta 《BMC plant biology》2010,10(1):81