全文获取类型
收费全文 | 501883篇 |
免费 | 57825篇 |
国内免费 | 3751篇 |
出版年
2021年 | 5702篇 |
2020年 | 4963篇 |
2019年 | 6176篇 |
2018年 | 7234篇 |
2017年 | 6230篇 |
2016年 | 8444篇 |
2015年 | 12165篇 |
2014年 | 14194篇 |
2013年 | 17956篇 |
2012年 | 20326篇 |
2011年 | 19946篇 |
2010年 | 12731篇 |
2009年 | 11880篇 |
2008年 | 15648篇 |
2007年 | 15386篇 |
2006年 | 13974篇 |
2005年 | 12918篇 |
2004年 | 12083篇 |
2003年 | 11870篇 |
2002年 | 11093篇 |
2001年 | 20865篇 |
2000年 | 20964篇 |
1999年 | 16841篇 |
1998年 | 6065篇 |
1997年 | 6657篇 |
1996年 | 6281篇 |
1995年 | 6047篇 |
1994年 | 5854篇 |
1993年 | 5876篇 |
1992年 | 13917篇 |
1991年 | 13631篇 |
1990年 | 12940篇 |
1989年 | 12627篇 |
1988年 | 11491篇 |
1987年 | 11096篇 |
1986年 | 10335篇 |
1985年 | 10337篇 |
1984年 | 8577篇 |
1983年 | 7409篇 |
1982年 | 5664篇 |
1981年 | 5029篇 |
1979年 | 7992篇 |
1978年 | 6391篇 |
1977年 | 5818篇 |
1976年 | 5480篇 |
1975年 | 6024篇 |
1974年 | 6219篇 |
1973年 | 6145篇 |
1972年 | 5549篇 |
1971年 | 5104篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Characteristics of morphology and number of melanomacrophage centers (MMCs) in the liver and spleen of the roach Rutilus rutilus and the amount of pigments in MMCs during the Haff disease outbreak and the death of fish in Lake Kotokel in relation to these parameters in the roach from Lake Baikal are described. Pathological changes in the microvasculature and parenchyma in the liver of the roach from Lake Kotokel were found. The area of melanomacrophage centers in the liver of the roach from this lake was significantly smaller, whereas the number and size of these centers in the spleen was significantly larger than in the roaches from Lake Baikal. Among the pigments studied, the strongest response to the content of this toxin in the water body was shown by hemosiderin. An increase in its amount in the spleen MMCs testifies to an enhanced degradation of erythrocytes and iron release, which may be caused by the damage of cells of the erythrocyte lineage by the toxin. 相似文献
4.
5.
6.
Robin D. Clugston Jason J. Yuen Yunying Hu Nada A. Abumrad Paul D. Berk Ira J. Goldberg William S. Blaner Li-Shin Huang 《Journal of lipid research》2014,55(2):239-246
CD36 is a scavenger receptor with multiple ligands and cellular functions, including facilitating cellular uptake of free fatty acids (FFAs). Chronic alcohol consumption increases hepatic CD36 expression, leading to the hypothesis that this promotes uptake of circulating FFAs, which then serve as a substrate for triglyceride (TG) synthesis and the development of alcoholic steatosis. We investigated this hypothesis in alcohol-fed wild-type and Cd36-deficient (Cd36−/−) mice using low-fat/high-carbohydrate Lieber-DeCarli liquid diets, positing that Cd36−/− mice would be resistant to alcoholic steatosis. Our data show that the livers of Cd36−/− mice are resistant to the lipogenic effect of consuming high-carbohydrate liquid diets. These mice also do not further develop alcoholic steatosis when chronically fed alcohol. Surprisingly, we did not detect an effect of alcohol or CD36 deficiency on hepatic FFA uptake; however, the lower baseline levels of hepatic TG in Cd36−/− mice fed a liquid diet were associated with decreased expression of genes in the de novo lipogenesis pathway and a lower rate of hepatic de novo lipogenesis. In conclusion, Cd36−/− mice are resistant to hepatic steatosis when fed a high-carbohydrate liquid diet, and they are also resistant to alcoholic steatosis. These studies highlight an important role for CD36 in hepatic lipid homeostasis that is not associated with hepatic fatty acid uptake. 相似文献
7.
Hemant Kulkarni Peter J. Meikle Manju Mamtani Jacquelyn M. Weir Marcio Almeida Vincent Diego Juan Manuel Peralta Christopher K. Barlow Claire Bellis Thomas D. Dyer Laura Almasy Michael C. Mahaney Anthony G. Comuzzie Harald H. H. G?ring Joanne E. Curran John Blangero 《Journal of lipid research》2014,55(5):939-946
Plasma lipidome is now increasingly recognized as a potentially important marker of chronic diseases, but the exact extent of its contribution to the interindividual phenotypic variability in family studies is unknown. Here, we used the rich data from the ongoing San Antonio Family Heart Study (SAFHS) and developed a novel statistical approach to quantify the independent and additive value of the plasma lipidome in explaining metabolic syndrome (MS) variability in Mexican American families recruited in the SAFHS. Our analytical approach included two preprocessing steps: principal components analysis of the high-resolution plasma lipidomics data and construction of a subject-subject lipidomic similarity matrix. We then used the Sequential Oligogenic Linkage Analysis Routines software to model the complex family relationships, lipidomic similarities, and other important covariates in a variance components framework. Our results suggested that even after accounting for the shared genetic influences, indicators of lipemic status (total serum cholesterol, TGs, and HDL cholesterol), and obesity, the plasma lipidome independently explained 22% of variability in the homeostatic model of assessment-insulin resistance trait and 16% to 22% variability in glucose, insulin, and waist circumference. Our results demonstrate that plasma lipidomic studies can additively contribute to an understanding of the interindividual variability in MS. 相似文献
8.
Yuan Zhang Wei Zou Fenggong Cui Nan Wang Dongyan Zhang Yuying Cui Peng Liu Jing Liu 《The Journal of membrane biology》2014,247(1):73-80
The absorption of phospholipid may improve the fluidity of membrane and enzyme activities. Phospholipids also play a role in promoting Caveolae formation and membrane synthesis. Caveolin-1 has a significant effect on signaling pathways involved in regulating cell proliferation and stress responsiveness. Thus, we can speculate that Caveolin-1 could affect the sense of environmental stress. We use Chang liver cell line to investigate the ability of Caveolin-1 to modulate the cellular response to ethanol injury. Caveolin-1 downregulate cells (Cav-1?/?) were established by stable transfecting with psiRNA-CAV1 plasmids, which were more sensitive to toxic effects of ethanol than the untransfected parental cells (WT). Releasing of ALT and electric conductivity were changed significantly in Cav-1?/? cells compared with WT. Caveolin-1 gene silencing could obviously down-regulate the activities of protein kinase C-α (PKC-α) and phospho-p42/44 MAP kinase, indicating cell proliferation and self-repairing abilities were inhibited. However, the levels of Caveolin-1 and PKC-α were increased by phosphatidylcholine administration. The results indicated that the inhibition of lipid peroxidation by phosphatidylcholine could lead to the prevention of membrane disruption, which closely correlated with the level of Caveolin-1. Since the protective effects of phosphatidylcholine against ethanol-induced lipid peroxidation might be regulated by phospholipid-PKC-α signaling pathway, related with Caveolin-1, the potential effects of phosphatidylcholine on membranes need to be verified. 相似文献
9.
Frugivorous and nectarivorous bats rely largely on hepatic glycogenesis and glycogenolysis for postprandial blood glucose disposal and maintenance of glucose homeostasis during short time starvation, respectively. The glycogen synthase 2 encoded by the Gys2 gene plays a critical role in liver glycogen synthesis. To test whether the Gys2 gene has undergone adaptive evolution in bats with carbohydrate-rich diets in relation to their insect-eating sister taxa, we sequenced the coding region of the Gys2 gene in a number of bat species, including three Old World fruit bats (OWFBs) (Pteropodidae) and two New World fruit bats (NWFBs) (Phyllostomidae). Our results showed that the Gys2 coding sequences are highly conserved across all bat species we examined, and no evidence of positive selection was detected in the ancestral branches leading to OWFBs and NWFBs. Our explicit convergence test showed that posterior probabilities of convergence between several branches of OWFBs, and the NWFBs were markedly higher than that of divergence. Three parallel amino acid substitutions (Q72H, K371Q, and E666D) were detected among branches of OWFBs and NWFBs. Tests for parallel evolution showed that two parallel substitutions (Q72H and E666D) were driven by natural selection, while the K371Q was more likely to be fixed randomly. Thus, our results suggested that the Gys2 gene has undergone parallel evolution on amino acid level between OWFBs and NWFBs in relation to their carbohydrate metabolism. 相似文献
10.