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901.
Changes in the activity of membrane bound ATPase of Sarcoma 180 cells caused by immunoglobulin G (IgG) of anti-Sarcoma 180 was investigated in relation to the incorporation of amino acid by the cells. Enzymatic activity of ATPase was increased up to 160% of the original activity upon incubation of the cell with IgG. Kinetic studies showed that IgG did not change the affinity of this enzyme for the substrate, but exerted influence upon catalytic efficiency of the enzyme. The rate of incorporation of leucine into Sarcoma 180 cells was also affected by IgG, as observed in the effect of IgG on the enzymatic reaction of the cells. 相似文献
902.
The effects of copper on photosynthetic electron transfer systemsin isolated spinach chloroplasts were studied. Two differentinhibitions were observed. First, copper markedly inhibitedferredoxin-catalyzed reactions such as NADP+ photoreduction.The concentration required for 50% inhibition was about 2 µMof cupric sulfate. However, electron flow from reduced 2,6-dichloroindophenol(DCIP) to methyl viologen was not affected. The dissociationconstant between ferredoxin and ferredoxin-NADP+ reductase wasunchanged in the presence of 2.5 µM of cupric sulfate.In enzymic reaction systems, the ferredoxin-dependent electronflow from NADPH to cytochrome c was also strongly inhibitedin the presence of cupric sulfate, while DCIP reduction withNADPH as the electron donor was not affected. Second, DCIP photoreductionwas weakly blocked by copper and the lost activity could notbe recovered by adding 1,5-diphenylcarbazide (DPC). It can be concluded that copper directly interacted with ferredoxincausing inhibition of ferredoxin-dependent reactions. Further,copper caused weak inactivation between the oxidizing side ofthe reaction center of photosystem II and the electron donatingsite of DPC. (Received August 8, 1977; ) 相似文献
903.
Yoshimasa Kyogoku Byung Sul Yu Hideo Akutsu Mayumi Watanabe Keiichi Kawano 《Biochemical and biophysical research communications》1978,83(1):172-179
Triostin A exists as two symmetrical conformers in weakly polar solvents like chloroform. Adenine and guanine derivatives were found to specifically interact with one of the two conformers, but uracil and cytosine derivatives did not. From the analysis of nmr and infrared spectra, it was concluded that the purine derivatives form cyclic hydrogen bonds with the alanine residue of triostin A in addition to the stacking interaction between the purine base and the quinoxaline ring. 相似文献
904.
-Aminolevulinic acid dehydratase (-aminolevulinic acid hydrolyaseEC 4.2.1.24
[EC]
) which catalyzes the formation ofporphobilinogenfrom two molecules of -aminolevulinic acid (ALA) was purifiedfrom Chlorella regularis 737-fold by acetone and ammonium sulfatefractionations, DEAE-cellulose column chromatography, and SephadexG-200 gel filtration. The enzyme had an optimum pH of 8.5 inTris-HCl buffer and required either Mg2+ or Mn2+ for its maximumactivity. The Km values for Mg2+, Mn2+ and ALA were 15 µM,10µM, and 0.5 mM, respectively. The enzyme was not activatedby thiol compounds, but was inhibited by p-chloromercuribenzoate.The molecular weight estimated by gel filtration was 316,000and the isoelectric point was 5.25. (Received October 18, 1978; ) 相似文献
905.
Uchida T Nakamura T Hashimoto N Matsuda T Kotani K Sakaue H Kido Y Hayashi Y Nakayama KI White MF Kasuga M 《Nature medicine》2005,11(2):175-182
The protein p27(Kip1) regulates cell cycle progression in mammals by inhibiting the activity of cyclin-dependent kinases (CDKs). Here we show that p27(Kip1) progressively accumulates in the nucleus of pancreatic beta cells in mice that lack either insulin receptor substrate 2 (Irs2(-/-)) or the long form of the leptin receptor (Lepr(-/-) or db/db). Deletion of the gene encoding p27(Kip1) (Cdkn1b) ameliorated hyperglycemia in these animal models of type 2 diabetes mellitus by increasing islet mass and maintaining compensatory hyperinsulinemia, effects that were attributable predominantly to stimulation of pancreatic beta-cell proliferation. Thus, p27(Kip1) contributes to beta-cell failure during the development of type 2 diabetes in Irs2(-/-) and Lepr(-/-) mice and represents a potential new target for the treatment of this condition. 相似文献
906.
Transient inhibition of BMP signaling by Noggin induces cardiomyocyte differentiation of mouse embryonic stem cells 总被引:11,自引:0,他引:11
Yuasa S Itabashi Y Koshimizu U Tanaka T Sugimura K Kinoshita M Hattori F Fukami S Shimazaki T Ogawa S Okano H Fukuda K 《Nature biotechnology》2005,23(5):607-611
Embryonic stem (ES) cells are a promising source of cardiomyocytes, but clinical application of ES cells has been hindered by the lack of reliable selective differentiation methods. Differentiation into any lineage is partly dependent on the regulatory mechanisms of normal early development. Although several signals, including bone morphogenetic protein (BMP), Wnt and FGF, are involved in heart development, scarce evidence is available about the exact signals that mediate cardiomyocyte differentiation. While investigating the involvement of BMP signaling in early heart formation in the mouse, we found that the BMP antagonist Noggin is transiently but strongly expressed in the heart-forming region during gastrulation and acts at the level of induction of mesendoderm to establish conditions conducive to cardiogenesis. We applied this finding to develop an effective protocol for obtaining cardiomyocytes from mouse ES cells by inhibition of BMP signaling. 相似文献
907.
Rad51 siRNA delivered by HVJ envelope vector enhances the anti-cancer effect of cisplatin 总被引:2,自引:0,他引:2
Ito M Yamamoto S Nimura K Hiraoka K Tamai K Kaneda Y 《The journal of gene medicine》2005,7(8):1044-1052
908.
Comparison of effects of nitric oxide synthase (NOS) inhibitors on plasma nitrite/nitrate levels and tissue NOS activity in septic organs 总被引:6,自引:0,他引:6
Hayashi Y Abe M Murai A Shimizu N Okamoto I Katsuragi T Tanaka K 《Microbiology and immunology》2005,49(2):139-147
An excessive production of nitric oxide (NO) by NO synthase (NOS) is considered to contribute to circulatory disturbance, tissue damage, and refractory hypotention, which are often observed in septic disorders. It is anticipated that a selective inducible NOS (iNOS) inhibitor with excellent pharmacokinetics may be potentially effective as a novel and potent therapeutic intervention in sepsis. We examined whether or not a selective iNOS inhibitor shows iNOS selectivity at the tissue level, when administered systemically. The effects of four NOS inhibitors on plasma nitrite/nitrate (NOx) and tissue NOS levels were compared in major organs (lungs, liver, heart, kidneys, and brain) 6 hr after the injection of E. coli lipopolysaccharide (LPS) into male Wistar-King rats. The rats treated with the three iNOS inhibitors (N-(3-(aminomethyl)benzyl)acetamidine (1400W), (1 S, 5 S, 6 R, 7 R )-2-aza-7-chloro-3-imino-5-methylbicyclo [4.1.0] heptane hydrochloride (ONO-1714), and aminoguanidine) administered 1 hr after LPS injection, showed dose-dependent decreases in plasma NOx levels and NOS activity in the lungs. The non-selective NOS inhibitor (N(G)-methyl-L-arginine (L-NMMA)) had an effect only at the maximum dose. The differences in in vitro iNOS selectivity among these drugs did not correlate with iNOS selectivity at the tissue level. The relationship between plasma NOx levels and NOS activity in the lungs showed a linear relationship with or without the NOS inhibitors. In conclusion, the iNOS selectivity of these drugs does not seem to differ at the tissue level. Plasma NOx levels may be a useful indicator of lung NOS activity. 相似文献
909.
Shimamoto S Tamai E Matsushita O Minami J Okabe A Miyata S 《Microbiology and immunology》2005,49(3):245-253
Epsilon-toxin (ET) of Clostridium perfringens, which causes fatal enterotoxemia in ungulates, was previously shown to bind to and form a heptameric pore within the detergent-resistant membranes (DRMs) of MDCK cells. Depletion of cholesterol has also been shown to decrease the cytotoxicity of ET and its heptamerization. In this study, we investigated the effects of changes in sphingolipids, other DRM components of MDCK cells, on the cells' susceptibility to ET. Treatment with fumonisin B1 and PDMP, inhibitors of sphingolipid and glycosphingolipid syntheses, respectively, increased the susceptibility, while D609, a sphingomyelin synthesis inhibitor, had the opposite effect. The exogenous addition of ganglioside G(M1) dramatically decreased the ET binding, heptamerization and cytotoxicity. These effects were shown not to be due to ET binding to G(M1) or to denaturation of ET. We also found that the ET cytotoxicity towards MDCK cells decreased with an increase in culture time. In accordance with the resistance observed for prolonged cultured cells, G(M3), a major ganglioside component, increased and sialidase treatment increased their susceptibility. These results suggest that membrane-anchored sialic acid of G(M3) within DRMs inhibits ET binding, leading to prevention of the heptamerization of ET and cell death. It is also suggested that sialidase produced by this organism aids the targeting of ET to MDCK cells. 相似文献
910.
Trialkyltin compounds bind retinoid X receptor to alter human placental endocrine functions 总被引:1,自引:0,他引:1