全文获取类型
收费全文 | 13214篇 |
免费 | 970篇 |
国内免费 | 6篇 |
出版年
2021年 | 95篇 |
2020年 | 69篇 |
2019年 | 108篇 |
2018年 | 114篇 |
2017年 | 149篇 |
2016年 | 206篇 |
2015年 | 272篇 |
2014年 | 383篇 |
2013年 | 860篇 |
2012年 | 627篇 |
2011年 | 637篇 |
2010年 | 445篇 |
2009年 | 422篇 |
2008年 | 647篇 |
2007年 | 664篇 |
2006年 | 623篇 |
2005年 | 620篇 |
2004年 | 635篇 |
2003年 | 626篇 |
2002年 | 599篇 |
2001年 | 464篇 |
2000年 | 484篇 |
1999年 | 397篇 |
1998年 | 153篇 |
1997年 | 155篇 |
1996年 | 118篇 |
1995年 | 135篇 |
1994年 | 127篇 |
1993年 | 115篇 |
1992年 | 277篇 |
1991年 | 250篇 |
1990年 | 242篇 |
1989年 | 245篇 |
1988年 | 232篇 |
1987年 | 193篇 |
1986年 | 202篇 |
1985年 | 171篇 |
1984年 | 128篇 |
1983年 | 144篇 |
1982年 | 125篇 |
1981年 | 80篇 |
1980年 | 84篇 |
1979年 | 126篇 |
1978年 | 82篇 |
1977年 | 80篇 |
1976年 | 49篇 |
1975年 | 59篇 |
1973年 | 58篇 |
1972年 | 56篇 |
1970年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Kinetic resolution of organosilicon compounds by stereoselective dehydrogenation with horse liver alcohol dehydrogenase 总被引:3,自引:0,他引:3
Toshiaki Fukui Min-Hua Zong Takuo Kawamoto Atsuo Tanaka 《Applied microbiology and biotechnology》1992,38(2):209-213
Streoselective dehydrogenation of three isomers of trimethylsilypropanol was carried out with horse liver alcohol dehydrogenase (HLADH, EC 1.1.1.1.) and optically active organosilicon compounds were obtained in a water-organic solvent two-layer system with coenzyme regeneration. Furthermore, we examined the effects of the silicon atom on stereoselectivity of HLADH compared to the corresponding carbon compounds. Substitution of the silicon atom for the carbon atom was found to improve the stereoselectivity of HLADH. For example, the optical purity of the remaining 1-trimethylsilyl-2-propanol was higher than 99% enantiomeric excess (ee) at 50% conversion, whereas that of the carbon analogue was 84% ee. This phenomenon was probably ascribable to the bulkiness of the organosilicon compounds derived from their longer Si-C bond. Kinetic analysis in an aqueous monolayer system demonstrated that the specific properties of the silicon atom greatly affected the reactivity of these substrate compounds.Correspondence to: A. Tanaka 相似文献
33.
Expression of three clones (6-1E, 7-3G and 9-5C) selected from a chronic lymphocytic leukemia cDNA library was studied by nucleic acid hybridization in human promyelocytic leukemia cells (HL-60) treated with chemical inducers of cell differentiation and in primary cells derived from 27 patients with leukemia or myelodysplastic syndrome. The differentiation of HL-60 cells into macrophage-like cells upon induction by 12-0-tetradecanoyl phorbol-13-acetate (TPA) was accompanied by rapid induction of the expression of 6-1E and 7-3G genes. The levels of expression of the 9-5C gene were not altered during macrophage-monocytic or granulocytic differentiation of HL-60 cells. The expression of the 6-1E and/or 7-3G gene was induced by TPA in four of 6 samples derived from patients who achieved complete remission, but not in any of the acute nonlymphocytic leukemia samples from patients who failed to achieve complete remission. These findings suggest that expression of the 6-1E and 7-3G genes is related to macrophage-monocytic differentiation and that alterations of these gene expressions in fresh leukemia cells after one hour of TPA treatment are of prognostic significance in predicting the response to therapy. 相似文献
34.
Inhibitory effect of tumor necrosis factor on gene expression of hormone sensitive lipase in 3T3-L1 adipocytes 总被引:1,自引:0,他引:1
Recombinant human tumor necrosis factor (TNF) depressed the activities of both lipoprotein lipase (LPL) and hormone sensitive lipase (HSL) in 3T3-L1 adipocytes, 3 to 24 h after its introduction to the cells. HSL gene expression, as measured by Northern blotting analysis with 32P-labeled cloned HSL-cDNA, was also suppressed. These results suggested that the reduction in HSL activity caused by TNF resulted from inhibited gene expression of the enzyme. 相似文献
35.
36.
37.
Ramya Krishnan Rahul Ravikumar Menon Naoto Tanaka Hans-Jürgen Busse Srinivasan Krishnamurthi Natarajan Rameshkumar 《PloS one》2016,11(3)
A novel yellow colony-forming bacterium, strain P3B162T was isolated from the pokkali rice rhizosphere from Kerala, India, as part of a project study aimed at isolating plant growth beneficial rhizobacteria from saline tolerant pokkali rice and functionally evaluate their abilities to promote plant growth under saline conditions. The novel strain P3B162T possesses plant growth beneficial traits such as positive growth on 1-aminocyclopropane-1-carboxylic acid (ACC), production of indole acetic acid (IAA) and siderophore. In addition, it also showed important phenotypic characters such as ability to form biofilm and utilization of various components of plant root exudates (sugars, amino acids and organic acids), clearly indicating its lifestyle as a plant rhizosphere associated bacterium. Taxonomically, the novel strain P3B162T was affiliated to the genus Arthrobacter based on the collective results of phenotypic, genotypic and chemotaxonomic analyses. Moreover, molecular analysis using 16S rRNA gene showed Arthrobacter globiformis NBRC 12137T, Arthrobacter pascens DSM 20545T and Arthrobacter liuii DSXY973T as the closely related phylogenetic neighbours, showing more than 98% 16S rRNA similarity values, whereas the recA gene analysis displayed Arthrobacter liuii JCM 19864T as the nearest neighbour with 94.7% sequence similarity and only 91.7% to Arthrobacter globiformis LMG 3813T and 88.7% to Arthrobacter pascens LMG 16255T. However, the DNA-DNA hybridization values between strain P3B162T, Arthrobacter globiformis LMG 3813T, Arthrobacter pascens LMG 16255T and Arthrobacter liuii JCM 19864T was below 50%. In addition, the novel strain P3B162T can be distinguished from its closely related type strains by several phenotypic characters such as colony pigment, tolerance to NaCl, motility, reduction of nitrate, hydrolysis of DNA, acid from sucrose, cell wall sugars and cell wall peptidoglycan structure. In conclusion, the combined results of this study support the classification of strain P3B162T as a novel Arthrobacter species and we propose Arthrobacter pokkalii sp.nov.as its name. The type strain is P3B162T (= KCTC 29498T = MTCC 12358T). 相似文献
38.
G-protein-coupled receptor (GPR) 3 is a member of the GPR family that constitutively activates adenylate cyclase. We have reported that the expression of GPR3 in cerebellar granular neurons (CGNs) contributes to neurite outgrowth and modulates neuronal proliferation and survival. To further identify its role, we have analyzed the precise distribution and local functions of GPR3 in neurons. The fluorescently tagged GPR3 protein was distributed in the plasma membrane, the Golgi body, and the endosomes. In addition, we have revealed that the plasma membrane expression of GPR3 functionally up-regulated the levels of PKA, as measured by a PKA FRET indicator. Next, we asked if the PKA activity was modulated by the expression of GPR3 in CGNs. PKA activity was highly modulated at the neurite tips compared to the soma. In addition, the PKA activity at the neurite tips was up-regulated when GPR3 was transfected into the cells. However, local PKA activity was decreased when endogenous GPR3 was suppressed by a GPR3 siRNA. Finally, we determined the local dynamics of GPR3 in CGNs using time-lapse analysis. Surprisingly, the fluorescent GPR3 puncta were transported along the neurite in both directions over time. In addition, the anterograde movements of the GPR3 puncta in the neurite were significantly inhibited by actin or microtubule polymerization inhibitors and were also disturbed by the Myosin II inhibitor blebbistatin. Moreover, the PKA activity at the tips of the neurites was decreased when blebbistatin was administered. These results suggested that GPR3 was transported along the neurite and contributed to the local activation of PKA in CGN development. The local dynamics of GPR3 in CGNs may affect local neuronal functions, including neuronal differentiation and maturation. 相似文献
39.
40.