全文获取类型
收费全文 | 4906篇 |
免费 | 301篇 |
国内免费 | 2篇 |
出版年
2024年 | 6篇 |
2023年 | 13篇 |
2022年 | 56篇 |
2021年 | 80篇 |
2020年 | 52篇 |
2019年 | 71篇 |
2018年 | 101篇 |
2017年 | 86篇 |
2016年 | 157篇 |
2015年 | 264篇 |
2014年 | 316篇 |
2013年 | 337篇 |
2012年 | 484篇 |
2011年 | 424篇 |
2010年 | 268篇 |
2009年 | 240篇 |
2008年 | 336篇 |
2007年 | 263篇 |
2006年 | 257篇 |
2005年 | 221篇 |
2004年 | 191篇 |
2003年 | 169篇 |
2002年 | 149篇 |
2001年 | 127篇 |
2000年 | 124篇 |
1999年 | 112篇 |
1998年 | 38篇 |
1997年 | 28篇 |
1996年 | 20篇 |
1995年 | 21篇 |
1994年 | 20篇 |
1993年 | 17篇 |
1992年 | 26篇 |
1991年 | 23篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 9篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1974年 | 7篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1969年 | 4篇 |
1967年 | 5篇 |
1966年 | 5篇 |
排序方式: 共有5209条查询结果,搜索用时 15 毫秒
221.
Oh J Pyo JH Jo EH Hwang SI Kang SC Jung JH Park EK Kim SY Choi JY Lim J 《Proteomics》2004,4(11):3485-3497
A proteomic map for human urine on two-dimensional (2-D) gels has been developed. Initial studies demonstrated that the urine proteins prepared by conventional methods showed interference and poor reproducibility in 2-D electrophoresis (2-DE). To address this issue, urine samples were dialyzed to remove any interfering molecules. The dialysis of urine proteins and the concentration by lyophilization without fractionation significantly improved the reproducibility and resolution and likely represents the total urine proteins on a 2-D gel. In addition, removing albumin from urine using Affi-Gel Blue helped to identify the low-abundant proteins. Using the developed method, we prepared proteins from urine collected from healthy females and males. The large inter- and intra-subject variation in protein profiles on 2-D gels made it difficult to establish a normal human urine proteomic 2-D map. To resolve this problem, urinary proteins were prepared from the pooled urine collected from 20 healthy females and males, respectively. The established male and female urine proteomes separated on 2-D gels were almost identical except for some potential sex-dependent protein spots. We have annotated 113 different proteins on the 2-D gel by peptide mass fingerprinting (PMF). We propose that the established total urine proteome can be used for 2-DE analysis, liquid chromatography-tandem mass spectrometry (LC-MS/MS), and identification of novel disease-specific biomarkers. 相似文献
222.
Allergen-induced proteolytic cleavage of annexin-1 and activation of cytosolic phospholipase A2 in the lungs of a mouse model of asthma 总被引:2,自引:0,他引:2
To identify proteins that might play an important role in allergen-induced asthma, we analyzed lung extracts prepared from allergen (ovalbumin)-challenged animals in a mouse model of this condition. The combination of two-dimensional gel electrophoresis and mass spectrometry revealed that annexin-1, a 37 kDa anti-inflammatory protein that inhibits the activity of cytosolic phospholipase A(2) (cPLA(2)), was down-regulated by allergen challenge in the lungs of ovalbumin-sensitized mice. Immunoblot analysis showed that this effect of ovalbumin challenge was attributable to proteolytic cleavage of annexin-1. The ovalbumin-induced degradation of annexin-1 was blocked by pretreatment of mice with the antioxidant N-acetylcysteine (NAC) or with sodium selenite, both of which have previously been shown to exert anti-inflammatory effects in this asthma model. Ovalbumin challenge also both increased the expression of cPLA(2) in lung tissue and reduced the extent of the interaction between cPLA(2) and annexin-1, and these effects were inhibited by NAC or selenite. Moreover, the concentrations of cysteinyl leukotrienes in bronchoalveolar lavage fluid and of leukotriene B(4) in lung tissue were increased by ovalbumin challenge in a NAC- or selenite-sensitive manner. Together, these results suggest that allergen-induced oxidative stress results in proteolysis of annexin-1 and consequent up-regulation of cPLA(2) activity and leukotriene production in this mouse model of asthma, and that the anti-inflammatory effects of selenite may provide a basis for the development of new antiasthmatic drugs. 相似文献
223.
To study alcohol-related metabolism across inbred mouse strains, liver tissues from C57BL/6J (B6, an alcohol-preferring mouse) and DBA/2J (D2, an alcohol-avoiding strain) mice were analyzed for proteomic expression patterns over time after a single-dose of alcohol (1.5 g/kg ingestion). Despite no significant difference in the elimination rate of blood ethanol, two-dimensional electrophoresis gel images of liver proteins showed that proteins in B6 mice exhibited faster response and more quantitative (spot numbers) and qualitative (spot densities) changes than in D2 mice. Among the differentially expressed metabolic enzymes, four variants (alpha, beta, gamma and delta) of fructose 1,6-bisphosphatase (FBPase), a key regulatory gluconeogenic enzyme, showed remarkable changes in expression with time across the strains. The degree of spot alteration in alpha- and gamma-variants of FBPase in B6 mice was much higher than in D2 mice, while the beta- and delta-forms were not changed as much. Mass spectrometry (MS) analysis showed that the 1714.9 +/- 1 mass peak from the alpha- and gamma-variants of FBPase was much stronger than that of the beta- and delta-variants in both strains regardless of spot density. This MS peak contains 2-ANHAPFETDISTLTR-16, located at the N-terminal of FBPase, where the N-terminal alanine was found to be trimethylated. Thus, we propose this N-terminal fragment as a potential site for enzyme modification in response to ethanol, allowing for differences in two-dimensional gel spot intensity of variants of FBPase in the two mouse strains. 相似文献
224.
A Gram-positive, motile, endospore-forming and rod-shaped halophilic bacterial strain MSS-155 (KCTC 3788 and KCCM 41687) was isolated from a marine solar saltern of the Yellow Sea in Korea and was subjected to a polyphasic taxonomic study. This organism grew at temperature of 10.0–42.0°C with an optimum of 35°C. Strain MSS-155 grew optimally in the presence of 10% NaCl and did not grow in the absence of NaCl. The cell wall peptidoglycan type of strain MSS-155 was A4 based on l-Orn-d-Asp. Strain MSS-155 was also characterized chemotaxonomically by having menaquinone-7 (MK-7) as the predominant isoprenoid quinone and anteiso-C15:0 as the major fatty acid. The DNA G+C content was 44.0 mol%. Phylogenetic analysis based on 16S rDNA sequences showed that strain MSS-155 falls within the radiation of the cluster comprising Halobacillus species. Levels of 16S rDNA sequence similarity between strain MSS-155 and the type strains of four Halobacillus species were in the range 97.6–98.8%. Strain MSS-155 exhibited levels of DNA-DNA relatedness of 6.2–11.2% to the type strains of Halobacillus species described previously. On the basis of phenotypic properties, phylogeny, and genomic data, strain MSS-155 should be placed in the genus Halobacillus as a member of a novel species, for which we propose the name Halobacillus locisalis sp. nov.Communicated by W.D. Grant 相似文献
225.
Mesenchymal stem/progenitor cells developed in cultures from UC blood 总被引:21,自引:0,他引:21
Background Whether umbilical cord blood (UCB) serves as a source of mesenchymal stem/progenitor cells (MSPC) is controversial. MSPC are the best candidates for cellular therapy of orthopedic skeletal tissues. In order to explore the possibility of UCB as a useful source of MSPC, we identified, expanded in culture, and characterized MSPC from UCB harvests on a large scale. Methods Mononuclear cells isolated from UCB harvests (n=411) were cultured in media supplemented with 10% FBS. MSPC-like cells cultured from each UCB harvest were expanded ex vivo by successive subcultivation. UCB harvests with a more than 1000-fold expanding capacity (n=9) were examined for surface Ag phenotypes and in vitro differentiation potentials into osteogenic, chondrogenic and adipogenic lineages. Results Ninety-five out of a total of 411 UCB units (23.1%) generated MSPC-like cells during cultivation. Nine UCB units (2.2%) yielded MSPC with more than 1000-fold expansion capacity. These cells positively expressed MSPC-related Ag, but did not express myeloid, histocompatibility or endothelial Ag. These cells also possessed multiple capacities for osteogenic, chondrogenic and adipogenic differentiation. Discussion Although the incidence of UCB harvests producing MSPC in culture was low, some of them showed a more than 1000-fold expanding capacity, which is enough in cell numbers to be an allogeneic source for cellular therapy. Our results may encourage the use of UCB as an attractive target for allogeneic cellular therapeutic options in tissue engineering. 相似文献
226.
Various thioacetal artemisinin derivatives can inhibit the angiogenesis and might be angiogenesis inhibitors. In particular, 10 alpha-phenylthiodihydroartemisinins (5), 10 beta-benzenesulfonyl-9-epi-dihydroartemisinin (11) and 10 alpha-mercaptodihydroartemisinin (13) exhibit strong growth inhibition activity against HUVEC proliferation. Compound 11 have a good inhibitiory activity upon HUVEC tube formation, and 5 and 11 show a strong inhibitory effect on angiogenesis using CAM assay at 5 microg/egg by 90%. 相似文献
227.
228.
Syndecans-2 and -4; close cousins, but not identical twins 总被引:3,自引:0,他引:3
The vertebrate syndecans, which make up a four-member family of small type I transmembrane heparan sulfate proteoglycans, constitute evolutionarily conserved family proteins. In particular, sequences in the transmembrane and cytoplasmic domains are a unifying feature within the family. However, the extracellular domain sequences are molecule-specific, implying that different syndecans have evolved to carry out similar, but non-identical, functions. While all four syndecans have been implicated in regulation of the cytoskeleton, their roles are clearly complex. Recent developments indicate that the closely related syndecan-2 and -4 have separable functions, though both bind a number of ligands through their heparan sulfate chains. The specification of these activities is probably core protein related, but is it due to a distinct expression pattern or molecule-specific regulatory mechanisms? Although there is not yet enough data to provide unambiguous answers, here we shall review the known functions and regulatory mechanisms of syndecan-2 and -4. 相似文献
229.
TNF/LTA polymorphisms and risk for gastric cancer/duodenal ulcer in the Korean population 总被引:6,自引:0,他引:6
The tumor necrosis factor-alpha (TNF) and lymphotoxin-alpha (LTA) are proinflammatory cytokines with immunoregulatory effects. TNF is also known to inhibit gastric acid secretion. Previously we have shown that the known proinflammatory genotypes, IL-1B -31C/+ and IL-1RN *2/*2, were not associated with increased risks for gastric cancer/duodenal ulcer in the Korean population. In this study, we tested the association between the polymorphisms of another candidate cytokine TNF/LTA and 341 gastric cancers, 133 duodenal ulcers, and 261 healthy controls. Five TNF promoter polymorphisms (-1031, -863, -857, -308, and -238) and two LTA polymorphisms (intron 1 and Thr26Asn) were analyzed. Individual polymorphisms were not associated with the gastric cancer and/or duodenal ulcer risk. When a haplotype analysis was performed with seven polymorphisms, differences in haplotype profile between the controls and gastric cancer and/or duodenal ulcer were not statistically significant. However, the frequencies of individual haplotypes C and D, which had opposite alleles at -1031, -863, and -857, showed statistically significant differences between the gastric cancer and duodenal ulcer (P=0.005 and P=0.02, respectively), suggesting that the TNF/LTA genotypes might play an opposite role in the pathogenesis of gastric cancer and duodenal ulcer. 相似文献
230.
We have investigated the effects of centrally administered ginsenoside Rc and Rg1 on the modulation of G protein expression in the central nervous system in rat brain. The effects of continuous infusion of ginsenosides on the modulation of G protein -subunit mRNA were investigated by using in situ hybridization study. Rats were infused with ginsenoside Rc or Rg1 (10 g/10 l/h, i.c.v.) for 7 days, through preimplanted cannula by osmotic minipumps. The level of Gs mRNA was not changed by the infusion of ginsenoside Rc or Rg1. The level of Gai mRNA was significantly elevated in frontal cortex and hippocampus following treatment with ginsenoside Rc as well as ginsenoside Rg1. However, the level of Go mRNA was significantly decreased in part of the hippocampus and cerebellum after the animals had received ginsenoside Rg1 infusion. These results suggest that prolonged infusion of ginsenosides could differentially modulate the expression of G protein -subunit mRNA in rat brain in a region-specific manner. 相似文献