全文获取类型
收费全文 | 1752篇 |
免费 | 176篇 |
国内免费 | 53篇 |
出版年
2024年 | 4篇 |
2023年 | 24篇 |
2022年 | 39篇 |
2021年 | 86篇 |
2020年 | 52篇 |
2019年 | 62篇 |
2018年 | 64篇 |
2017年 | 43篇 |
2016年 | 66篇 |
2015年 | 98篇 |
2014年 | 119篇 |
2013年 | 126篇 |
2012年 | 149篇 |
2011年 | 146篇 |
2010年 | 78篇 |
2009年 | 68篇 |
2008年 | 88篇 |
2007年 | 77篇 |
2006年 | 59篇 |
2005年 | 71篇 |
2004年 | 49篇 |
2003年 | 45篇 |
2002年 | 41篇 |
2001年 | 23篇 |
2000年 | 40篇 |
1999年 | 39篇 |
1998年 | 9篇 |
1997年 | 16篇 |
1996年 | 25篇 |
1995年 | 10篇 |
1994年 | 15篇 |
1993年 | 6篇 |
1992年 | 20篇 |
1991年 | 11篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 14篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有1981条查询结果,搜索用时 468 毫秒
961.
Que Dang Sonya Whitted Robert M. Goeken Jason M. Brenchley Kenta Matsuda Charles R. Brown Bernard A. P. Lafont Matthew F. Starost Ranjini Iyengar Ronald J. Plishka Alicia Buckler-White Vanessa M. Hirsch 《Journal of virology》2012,86(24):13795-13799
Simian immunodeficiency virus (SIV) infection of macaques can result in central nervous system disorders, such as meningitis and encephalitis. We studied 10 animals inoculated with brain-derived virus from animals with SIV encephalitis. Over half of the macaques developed SIV-induced neurologic disease. Elevated levels of systemic immune activation were observed to correlate with viral RNA in the cerebral spinal fluid but not with plasma viral load, consistent with a role for SIV in the pathogenesis of neurologic disease. 相似文献
962.
Le Dinh Hung Bui Minh Ly Vo Thi Dieu Trang Ngo Thi Duy Ngoc Le Thi Hoa Phan Thi Hoai Trinh 《Journal of applied phycology》2012,24(2):227-235
Aqueous extracts from 42 species of Vietnamese marine macroalgae, including 17 Chlorophyta, 22 Rhodophyta, and three Phaeophyta
species, were examined for hemagglutination activity using native and enzyme-treated different animal and human erythrocytes.
All extracts agglutinated at least one type of erythrocytes tested. Strong activity was detected in extracts from four Chlorophyta
(Caulerpa serulata var. boryana, Caulerpa sertularioides f. longipes, Halimeda velasquezii, and Halimeda discoidea) and two Rhodophyta species (Gelidiella acerosa and Titanophora pulchra) with enzyme-treated rabbit and horse erythrocytes. The hemagglutinins of some active species were examined for sugar-binding
specificity, pH, temperature stability, and divalent cation independency using ammonium sulfate precipitates prepared from
their extracts. In a hemagglutination–inhibition test with various monosaccharides and glycoproteins, none of the hemagglutinins
had affinity for monosaccharides. The activity of the hemagglutinins was inhibited by some glycoproteins tested. The inhibition
profiles with glycoproteins were different depending on hemagglutinin species, suggesting the presence of lectins specific
for complex N-glycans, high mannose N-glycans or O-glycans. On the other hand, the activities of almost all algal hemagglutinins
were stable over a wide range of pH and temperature, and independent of the presence of divalent cations, except Gelidiopsis scoparia hemagglutinin, its activity was dependent on the presence of divalent cations. These results suggest that Vietnamese marine
macroalgae may be good sources of useful lectins for many biological applications. 相似文献
963.
A number of case-control studies were conducted to investigate the association of IL6 gene polymorphisms with colorectal cancer (CRC). However, the results were not always consistent. We performed a systematic review and meta-analysis to examine the association between the IL6 gene polymorphisms and CRC. Data were collected from the following electronic databases: PubMed, EMBASE, Web of Science, BIOSIS Previews, HuGENet, and Chinese Biomedical Literature Database, with the last report up to July 2011. A total of 17 studies involving 4 SNPs were included (16 for rs1800795, 2 for rs1800796, 2 for rs1800797, and 1 for rs13306435). Overall, no significant association of these polymorphisms with CRC was found in heterozygote comparisons as well as homozygote comparison, dominant genetic model and recessive model. In subgroup analysis, among studies using population-based controls, fulfilling Hardy-Weinberg equilibrium, or using Taqman genotyping method, we did not find any significant association. However, the rs1800795 C allele was significantly associated with reduced risk for CRC among persons who regularly or currently took NSAIDs (four studies, OR = 0.750; 95 % CI, 0.64-0.88; P = 0.474 for heterogeneity test), and with increased risk for CRC among persons who drank (one study, OR = 1.97; 95 % CI, 1.32-2.94). Individuals with the rs1800795 C allele in the IL6 gene have a significantly lower risk of CRC, but in the setting of NSAIDs use. Further studies are merited to assess the association between the IL6 gene polymorphisms and CRC risk among persons who take NSAIDs, drink or smoke, etc. 相似文献
964.
965.
966.
Dang TC Fujii M Rose AL Bligh M Waite TD 《Applied and environmental microbiology》2012,78(5):1574-1583
A continuous culturing system (chemostat) made of metal-free materials was successfully developed and used to maintain Fe-limited cultures of Microcystis aeruginosa PCC7806 at nanomolar iron (Fe) concentrations (20 to 50 nM total Fe). EDTA was used to maintain Fe in solution, with bioavailable Fe controlled by absorption of light by the ferric EDTA complex and resultant reduction of Fe(III) to Fe(II). A kinetic model describing Fe transformations and biological uptake was applied to determine the biologically available form of Fe (i.e., unchelated ferrous iron) that is produced by photoreductive dissociation of the ferric EDTA complex. Prediction by chemostat theory modified to account for the light-mediated formation of bioavailable Fe rather than total Fe was in good agreement with growth characteristics of M. aeruginosa under Fe limitation. The cellular Fe quota increased with increasing dilution rates in a manner consistent with the Droop theory. Short-term Fe uptake assays using cells maintained at steady state indicated that M. aeruginosa cells vary their maximum Fe uptake rate (ρ(max)) depending on the degree of Fe stress. The rate of Fe uptake was lower for cells grown under conditions of lower Fe availability (i.e., lower dilution rate), suggesting that cells in the continuous cultures adjusted to Fe limitation by decreasing ρ(max) while maintaining a constant affinity for Fe. 相似文献
967.
We performed suppression subtractive hybridization to identify genomic differences between Streptococcus mitis and Streptococcus pneumoniae. Based on the pheA gene, a primer set specific to S. mitis detection was found in 18 out of 103 S. mitis-specific clones. Our findings would be useful for discrimination of S. mitis from other closely related cocci in the oral environment. 相似文献
968.
Genistein exerts its anticarcinogenic effects by inducing G2/M arrest and apoptosis of cancer cells. However, the precise molecular mechanism of action of genistein has not been completely elucidated. In this study, we used quantitative proteomics to identify the genistein-induced protein alterations in gastric cancer cells and investigate the molecular mechanism responsible for the anti-cancer actions of genistein. Total 86 proteins were identified to be regulated by genistein, most of which were clustered into the regulation of cell division and G2/M transition, consistent with the anti-cancer effect of genistein. Many proteins including kinesin family proteins, TPX2, CDCA8, and CIT were identified for the first time to be regulated by genistein. Interestingly, five kinesin family proteins including KIF11, KIF20A, KIF22, KIF23, and CENPF were found to be simultaneously downregulated by genistein. Significantly decreased KIF20A was selected for further functional studies. The silencing of KIF20A inhibited cell viability and induced G2/M arrest, similar to the effects of genistein treatment in gastric cancer. And the silencing of KIF20A also increased cancer cell sensitivity to genistein inhibition, whereas overexpression of KIF20A markedly attenuated genistein-induced cell viability inhibition and G2/M arrest. These observations suggested that KIF20A played an important role in anti-cancer actions of genistein, and thus may be a potential molecular target for drug intervention of gastric cancer. 相似文献
969.
Mangrove sediment had high natural attenuation potential with more than 50% of total PAHs being removed within 15 days. The efficiency in degrading PAHs varied with the declining order of phenanthrene (Phe), fluoranthene (Fla), and pyrene (Pyr). The Most Probable Number (MPN) of PAH-degrading bacteria in the PAH-contaminated slurries was 2 to 4 orders of magnitude higher than that in the non-contaminated mangrove slurries. The biodegradation ability of the indigenous microbial community in mangrove sediment slurry was significantly increased after exposure to polycyclic aromatic hydrocarbons. Such enhancement effect was dependent on the level and time of exposure, as well as the types of PAH compounds. The lowest contamination level of 3 mg kg?1 was effective in promoting the degradation of Phe and Fla after seven days, but the enhancement effect for Pyr degradation was only found in the slurries exposed to contamination levels of 9 mg kg?1 for 30 days, suggesting a threshold concentration of PAHs to stimulate growth and activity of pyrene-degrading bacteria. The contamination level higher than the threshold concentration did not lead to more degradation. The present study provides insights into the natural attenuation of PAH-contaminated mangrove sediments. 相似文献
970.
Le A Lane AN Hamaker M Bose S Gouw A Barbi J Tsukamoto T Rojas CJ Slusher BS Zhang H Zimmerman LJ Liebler DC Slebos RJ Lorkiewicz PK Higashi RM Fan TW Dang CV 《Cell metabolism》2012,15(1):110-121
Because MYC plays a causal role in many human cancers, including those with hypoxic and nutrient-poor tumor microenvironments, we have determined the metabolic responses of a MYC-inducible human Burkitt lymphoma model P493 cell line to aerobic and hypoxic conditions, and to glucose deprivation, using stable isotope-resolved metabolomics. Using [U-(13)C]-glucose as the tracer, both glucose consumption and lactate production were increased by MYC expression and hypoxia. Using [U-(13)C,(15)N]-glutamine as the tracer, glutamine import and metabolism through the TCA cycle persisted under hypoxia, and glutamine contributed significantly to citrate carbons. Under glucose deprivation, glutamine-derived fumarate, malate, and citrate were significantly increased. Their (13)C-labeling patterns demonstrate an alternative energy-generating glutaminolysis pathway involving a glucose-independent TCA cycle. The essential role of glutamine metabolism in cell survival and proliferation under hypoxia and glucose deficiency makes them susceptible to the glutaminase inhibitor BPTES and hence could be targeted for cancer therapy. 相似文献