首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2083篇
  免费   221篇
  国内免费   173篇
  2024年   4篇
  2023年   32篇
  2022年   57篇
  2021年   112篇
  2020年   82篇
  2019年   113篇
  2018年   130篇
  2017年   78篇
  2016年   110篇
  2015年   158篇
  2014年   165篇
  2013年   152篇
  2012年   184篇
  2011年   139篇
  2010年   87篇
  2009年   78篇
  2008年   99篇
  2007年   94篇
  2006年   84篇
  2005年   67篇
  2004年   62篇
  2003年   69篇
  2002年   84篇
  2001年   41篇
  2000年   30篇
  1999年   29篇
  1998年   23篇
  1997年   15篇
  1996年   16篇
  1995年   10篇
  1994年   12篇
  1993年   5篇
  1992年   3篇
  1991年   15篇
  1990年   3篇
  1989年   5篇
  1988年   2篇
  1987年   5篇
  1985年   4篇
  1983年   3篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1975年   2篇
  1974年   1篇
  1973年   2篇
  1972年   1篇
  1970年   1篇
排序方式: 共有2477条查询结果,搜索用时 15 毫秒
41.
Journal of Physiology and Biochemistry - Cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP) belong to the same gene family. Liver-specific expression of CETP...  相似文献   
42.
Glyphosate [N-(phosphonomethyl)-glycine] is a herbicide widely used in large quantities in agricultural applications. It is also known to form complexes with metal ions, although its influence on metal behavior, such as lead (Pb) in soil, is not well understood. In this study, the adsorption and co-adsorption of Pb and glyphosate were determined on two soils [a red (RS) soil, Udic Ferrisol, and a yellow-brown (YB) soil, Udic Luvisol] of distinctly different chemical characteristics at varying pH conditions. Results indicate that the adsorption of lead and glyphosate strongly depends on soil types: the RS soil, characterized by a relatively high iron/aluminum content but a low pH and organic matter content, shows a much lower adsorption capacity for Pb but a higher sorption for glyphosate than the YB soil. The co-existence of Pb and glyphosate in soils resulted in complex interactions among Pb, glyphosate, Pb-glyphosate complexes, and soil minerals. The presence of glyphosate decreased Pb adsorption on the two soils, which was attributed primarily to the formation of soluble Pb-glyphosate complexes having relatively low affinities to soil surfaces. On the other hand, addition of Pb increased the adsorption of glyphosate on both soils, which was attributed to: (1) a decreased solution pH due to the ion exchange between Pb2+ and H+ on soil surfaces; and (2) increased sorption sites where Pb was adsorbed and acted as a bridge between glyphosate and the soil. The present study illustrates that the complex interactions among glyphosate, Pb, and soil may have important implications for the mobility and bioavailability of Pb in soil and should thus be considered in future environmental risk assessments.  相似文献   
43.
This study investigated the effect of glutamate decarboxylase from Neurospora crassa OR74A on GABA production in Escherichia coli. GABA is one of the inhibitory neurotransmitters in the mammalian central nervous system, and can be used as a precursor of promising biopolymer Nylon 4. E. coli that overexpressed N. crassa glutamate decarboxylase was cultured at various pH levels and temperatures to determine optimum conditions for GABA production. When the recombinant E. coli strain was cultured at 30°C and pH 3, a final GABA concentration of 5.26 g/L was obtained from 10 g/L of monosodium glutamate (MSG), corresponding to a GABA yield of 86.23%.  相似文献   
44.
A series of naphthoquinone-benzothiazole conjugates were synthesized as algicides, and their efficacies against harmful algal blooming species, such as Chattonella marina, Heterosigma akashiwo and Cochlodinium polykrikoides, were examined. The introduction of substituted benzothiazole at the C2 position of 1,4-naphthoquinone (compounds 19) resulted in higher algicidal activity against C. polykrikoides than the C6 conjugates (compounds 1020). On the other hand, of the C6 conjugates, compounds 11 and 12 exhibited better algicidal activity against H. akashiwo, C. marina, and C. polykrikoides than the C2 conjugates. Further structure-activity analysis indicated that a replacement of the methoxy groups with hydroxyl groups (compounds 2126) decreased the algicidal activity significantly. Among the various synthetic naphthoquinonebezothiazole conjugates tested, compound 12 was found to affect the most significant decrease in the level of C. polykrikoides growth, with an IC50 of 0.19 μM. Compound 11 was found to be the most potent inhibitor against H. akashiwo and C. polykrikoides, with IC50 values of 0.32 and 0.12 μM, respectively. Overall, these results highlight a possible method for controlling and inhibiting red tide forming algae using NQ derivatives.  相似文献   
45.
We studied the inhibitory effect of gastrodin on tyrosinase using inhibition kinetics and computational simulation. Gastrodin reversibly inhibited tyrosinase in a mixed-type manner with Ki = 123.8 ± 20.2 mM. Time-interval kinetics revealed the inhibition to be a first-order process with mono- and bi-phasic components. Using AutoDock Vina, we calculated a binding energy of ?6.3 kcal/mol for gastrodin and tyrosinase, and we performed a molecular dynamics simulation of the tyrosinase–gastrodin interaction. The simulation results suggested that gastrodin interacts primarily with histidine residues in the active site. A 10-ns molecular dynamics simulation showed that one copper ion in the tyrosinase active site was responsible for the interaction with gastrodin. Our study provides insight into the inhibition of tyrosinase by the hydroxyl groups of gastrodin. A combination of inhibition kinetics and computational calculations may help to confirm the inhibitory action of gastrodin on tyrosinase and define the mechanisms of inhibition.  相似文献   
46.
Background aimsMany rodent experiments and human studies on stem cell therapy have shown promising therapeutic approaches to liver diseases. We investigated the clinical outcomes of five patients with liver failure of various causes who received autologous CD34-depleted bone marrow-derived mononuclear cell (BM-MNC) transplantation, including mesenchymal stromal cells, through the hepatic artery.MethodsCD34-depleted BM-MNCs were obtained from five patients waiting for liver transplantation by bone marrow aspiration and using the CliniMACS CD34 Reagent System (Miltenyi Biotech, Bergisch Gladbach, Germany), and autologous hepatic artery infusion was performed. The causes of hepatic decompensation were hepatitis B virus (HBV), hepatitis C virus (HCV), propylthiouracil-induced toxic hepatitis and Wilson disease.ResultsSerum albumin levels improved 1 week after transplantation from 2.8 g/dL, 2.4 g/dL, 2.7 g/dL and 1.9 g/dL to 3.3 g/dL, 3.1 g/dL, 2.8 g/dL and 2.6 g/dL. Transient liver elastography data showed some change from 65 kPa, 33 kPa, 34.8 kPa and undetectable to 46.4 kPa, 19.8 kPa, 29.1 kPa and 67.8 kPa at 4 weeks after transplantation in a patient with Wilson disease, a patient with HCV, and two patients with HBV. Ascites decreased in two patients. One of the patients with HBV underwent liver transplantation 4 months after the infusion, and the hepatic progenitor markers (cytokeratin [CD]-7, CD-8, CD-9, CD-18, CD-19, c-Kit and epithelial cell adhesion molecule [EpCAM]) were highly expressed in the explanted liver.ConclusionsSerum albumin levels, liver stiffness, liver volume, subjective healthiness and quality of life improved in the study patients. Although these findings were observed in a small population, the results may suggest a promising future for autologous CD34-depleted BM-MNC transplantation as a bridge to liver transplantation in patients with liver failure.  相似文献   
47.
Cardiomyocyte apoptosis is a common pathological alteration in heart disease which results in systolic dysfunction or sudden death. Klotho is a novel anti-aging hormone. We tested the effects of klotho on cell apoptosis in isoproterenol-treated cardiomyocytes. In BALB/c mice, cardiac injury was induced by subcutaneous injection of isoproterenol (5mg/kg, for 9days, sc). Klotho (0.01 mg/kg, every other day for 4days, ip) was administered to determine the changes in isoproterenol-induced apoptosis. Mouse heart was harvested at day 2, day 5, and day 9 after isoproterenol injection. Isoproterenol induced cardiac apoptosis and endoplasmic reticulum (ER) stress in a time-dependent manner. However, klotho partly reversed isoproterenol-induced cardiac apoptosis and ER stress. These same effects were observed in cultured cardiomyocytes. Furthermore, the results also showed that SB203580, a p38 inhibitor, and SP600125, a c-Jun NH2-terminal kinase (JNK) inhibitor, reduced cardiomyocyte apoptosis and ER stress, however, klotho suppressed isoproterenol-induced activation of p38 and JNK. Taken together, these results indicated that cardioprotection by klotho was related to the attenuation of ER stress and ER stress-induced apoptosis, at least partly, through suppressing activation of the p38 and JNK pathway.  相似文献   
48.
Coral harbor diverse and specific bacteria play significant roles in coral holobiont function. Bacteria associated with three of the common and phylogenetically divergent reef-building corals in the South China Sea, Porites lutea, Galaxea fascicularis and Acropora millepora, were investigated using 454 barcoded-pyrosequencing. Three colonies of each species were sampled, and 16S rRNA gene libraries were constructed individually. Analysis of pyrosequencing libraries showed that bacterial communities associated with the three coral species were more diverse than previous estimates based on corals from the Caribbean Sea, Indo-Pacific reefs and the Red Sea. Three candidate phyla, including BRC1, OD1 and SR1, were found for the first time in corals. Bacterial communities were separated into three groups: P. lutea and G. fascicular, A. millepora and seawater. P. lutea and G. fascicular displayed more similar bacterial communities, and bacterial communities associated with A. millepora differed from the other two coral species. The three coral species shared only 22 OTUs, which were distributed in Alphaproteobacteria, Deltaproteobacteria, Gammaproteobacteria, Chloroflexi, Actinobacteria, Acidobacteria and an unclassified bacterial group. The composition of bacterial communities within each colony of each coral species also showed variation. The relatively small common and large specific bacterial communities in these corals implies that bacterial associations may be structured by multiple factors at different scales and that corals may associate with microbes in terms of similar function, rather than identical species.  相似文献   
49.
50.
Homeobox D10 (HoxD10) plays important roles in the differentiation of embryonic cells and progression of breast cancer. Our previous report revealed that insulin-like growth factor binding protein-3 (IGFBP3) was regulated by HoxD10 in gastric cancer cells; however, the functional roles and underlying mechanisms of IGFBP3 in gastric cancer remain unclear. Here, we found that the expression of IGFBP3 were upregulated after ectopic expression of HoxD10 in gastric cancer cells. Chromatin immunoprecipitation assay showed that HoxD10 bound to three potential regions of IGFBP3 promoter. Exogenous HoxD10 significantly enhanced the activity of luciferase reporter containing these binding regions in gastric cancer cells. Further data showed that all of these binding sites had Hox binding element “TTAT”. Immunohistochemical staining results revealed that IGFBP3 expression was significantly downregulated in 86 gastric adenocarcinomas tissues relative to their adjacent non-cancerous tissues (p<0.001). Moreover, IGFBP3 expression was significantly lower in gastric tumor with lymph node metastasis compared with that without lymph node metastasis (p=0.045). Patients with high expression level of IGFBP3 showed favorable 5 year overall survival (p=0.011). Knockdown of IGFBP3 accelerated gastric cancer cell migration and invasion and induced the expression of invasive factors including MMP14, uPA and uPAR. Thus, our data suggest that HoxD10-targeted gene IGFBP3 may suppress gastric cancer cell invasion and favors the survival of gastric cancer patients.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号