全文获取类型
收费全文 | 14788篇 |
免费 | 1296篇 |
国内免费 | 6篇 |
专业分类
16090篇 |
出版年
2022年 | 109篇 |
2021年 | 231篇 |
2020年 | 150篇 |
2019年 | 199篇 |
2018年 | 210篇 |
2017年 | 202篇 |
2016年 | 357篇 |
2015年 | 524篇 |
2014年 | 664篇 |
2013年 | 800篇 |
2012年 | 1007篇 |
2011年 | 1012篇 |
2010年 | 643篇 |
2009年 | 606篇 |
2008年 | 816篇 |
2007年 | 821篇 |
2006年 | 810篇 |
2005年 | 719篇 |
2004年 | 723篇 |
2003年 | 682篇 |
2002年 | 666篇 |
2001年 | 228篇 |
2000年 | 175篇 |
1999年 | 198篇 |
1998年 | 153篇 |
1997年 | 140篇 |
1996年 | 125篇 |
1995年 | 143篇 |
1994年 | 104篇 |
1993年 | 140篇 |
1992年 | 125篇 |
1991年 | 102篇 |
1990年 | 132篇 |
1989年 | 113篇 |
1988年 | 97篇 |
1987年 | 108篇 |
1986年 | 107篇 |
1985年 | 111篇 |
1984年 | 125篇 |
1983年 | 99篇 |
1982年 | 118篇 |
1981年 | 114篇 |
1980年 | 86篇 |
1979年 | 89篇 |
1978年 | 75篇 |
1977年 | 64篇 |
1976年 | 56篇 |
1975年 | 60篇 |
1974年 | 84篇 |
1973年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
13.
Deborah Shaw Ian R. Poxton John R.W. Govan 《FEMS immunology and medical microbiology》1995,11(2):99-106
Abstract Burkholderia cepacia has emerged as an important multiresistant pathogen in cystic fibrosis (CF), associated in 20% of colonised patients with a rapid and fatal decline in lung function. Although knowledge of B. cepacia epidemiology has improved, the mechanisms involved in pathogenesis remain obscure. In this study, B. cepacia lipopolysaccharide (LPS) was assessed for endotoxic potential and the capacity to induce tumour necrosis factor (TNF). LPS preparations from clinical and environmental isolates of B. cepacia and from the closely related species Burkholderia gladioli exhibited a higher endotoxic activity and more pronounced cytokine response in vitro compared to preparations from the major CF pathogen Pseudomonas aeruginosa . This study may help to explain the vicious host immune response observed during pulmonary exacerbations in CF patients colonised by B. cepacia and lead to therapeutic advances in clinical management. 相似文献
14.
Harjot K. Saini-Chohan Michael G. Holmes Adam J. Chicco William A. Taylor Russell L. Moore Sylvia A. McCune Diane L. Hickson-Bick Grant M. Hatch Genevieve C. Sparagna 《Journal of lipid research》2009,50(8):1600-1608
Cardiolipin (CL) is responsible for modulation of activities of various enzymes involved in oxidative phosphorylation. Although energy production decreases in heart failure (HF), regulation of cardiolipin during HF development is unknown. Enzymes involved in cardiac cardiolipin synthesis and remodeling were studied in spontaneously hypertensive HF (SHHF) rats, explanted hearts from human HF patients, and nonfailing Sprague Dawley (SD) rats. The biosynthetic enzymes cytidinediphosphatediacylglycerol synthetase (CDS), phosphatidylglycerolphosphate synthase (PGPS) and cardiolipin synthase (CLS) were investigated. Mitochondrial CDS activity and CDS-1 mRNA increased in HF whereas CDS-2 mRNA in SHHF and humans, not in SD rats, decreased. PGPS activity, but not mRNA, increased in SHHF. CLS activity and mRNA decreased in SHHF, but mRNA was not significantly altered in humans. Cardiolipin remodeling enzymes, monolysocardiolipin acyltransferase (MLCL AT) and tafazzin, showed variable changes during HF. MLCL AT activity increased in SHHF. Tafazzin mRNA decreased in SHHF and human HF, but not in SD rats. The gene expression of acyl-CoA: lysocardiolipin acyltransferase-1, an endoplasmic reticulum MLCL AT, remained unaltered in SHHF rats. The results provide mechanisms whereby both cardiolipin biosynthesis and remodeling are altered during HF. Increases in CDS-1, PGPS, and MLCL AT suggest compensatory mechanisms during the development of HF. Human and SD data imply that similar trends may occur in human HF, but not during nonpathological aging, consistent with previous cardiolipin studies. 相似文献
15.
16.
Summary H-Y (male-specific) antigen has been detected on the plasma membranes of both caput and caudal ram spermatozoa using both immunoperoxidase and immunofluorescence labelling techniques. In these spermatozoa the distribution of H-Y antigen appears to be confined to both the posterior region of the head and the mid-piece region of the flagellum. In addition, caput spermatozoa also exhibit intense immunoperoxidase staining of the cytoplasmic droplet which is situated on the flagellum at the base of the head. Western blot analyses of purified plasma membranes from the flagella of caudal spermatozoa have revealed the presence of a malespecific protein with an estimated molecular weight of 25,000–27,000. 相似文献
17.
Ian Higgins 《BMJ (Clinical research ed.)》1988,297(6664):1704
18.
19.
Genetic analysis of a proposed cis-acting temporal locus ( Adh-3t ), which regulates alcohol dehydrogenase C2 (ADH-C2 ) acitivity in mouse epididymis extracts, among F1 (ddN × BALB/c) × ddN male backcross progeny provided evidence for genetic distinctness between the structural ( Adh-3 ) and temporal ( Adh-3t ) loci on chromosome 3. Genetic analysis also confirmed the close, linkage of Adh-1 (encoding liver and kidney ADH-A2 ) and Adh-3 (encoding stomach ADH-C2 ) to within 0.3 centimorgans on the mouse genome. Evidence is presented for a proposed closely linked cis-acting temporal locus (designated Adh-1t ) for the A2 isozyme (encoded by Adh-1 ) controlling the activity of this enzyme in mouse kidney extracts, but having no apparent affect on liver and intestine ADH-A2 activities. An extensive survey of the distribution of Adh-1, Adh-3 and Adh-3t alleles among 65 strains of mice is reported — with the exception of two Japanese strains (ddN and KF), linkage disequilibrium between Adh-3 and Adh-3t was observed. Sex differences in mouse liver and kidney ADH-A2 activities were observed, with male/female ratios of approximately 0.6 and 3 respectively for these tissue extracts. 相似文献
20.