全文获取类型
收费全文 | 649313篇 |
免费 | 75105篇 |
国内免费 | 352篇 |
出版年
2016年 | 7051篇 |
2015年 | 9739篇 |
2014年 | 11343篇 |
2013年 | 16707篇 |
2012年 | 18666篇 |
2011年 | 18827篇 |
2010年 | 12694篇 |
2009年 | 11901篇 |
2008年 | 17010篇 |
2007年 | 17434篇 |
2006年 | 16670篇 |
2005年 | 16084篇 |
2004年 | 15749篇 |
2003年 | 15571篇 |
2002年 | 15041篇 |
2001年 | 27304篇 |
2000年 | 27529篇 |
1999年 | 22424篇 |
1998年 | 8345篇 |
1997年 | 8700篇 |
1996年 | 8478篇 |
1995年 | 7767篇 |
1994年 | 7929篇 |
1993年 | 7770篇 |
1992年 | 19347篇 |
1991年 | 18567篇 |
1990年 | 18438篇 |
1989年 | 18306篇 |
1988年 | 16897篇 |
1987年 | 16349篇 |
1986年 | 15152篇 |
1985年 | 15324篇 |
1984年 | 12621篇 |
1983年 | 11211篇 |
1982年 | 8690篇 |
1981年 | 7983篇 |
1980年 | 7541篇 |
1979年 | 12551篇 |
1978年 | 9849篇 |
1977年 | 9084篇 |
1976年 | 8754篇 |
1975年 | 9450篇 |
1974年 | 10142篇 |
1973年 | 9960篇 |
1972年 | 9179篇 |
1971年 | 8184篇 |
1970年 | 7240篇 |
1969年 | 6989篇 |
1968年 | 6307篇 |
1967年 | 5549篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
71.
72.
The ability to metabolically label proteins with 35S-methionine is critical for the analysis of protein synthesis and turnover. Despite the importance of this approach, however, efficient labeling of proteins in vivo is often limited by a low number of available methionine residues, or by deleterious side-effects associated with protein overexpression. To overcome these limitations, we have created a methionine-rich variant of the widely used HA tag, called HAM, for use with ectopically expressed proteins. Here we describe the development of a series of vectors, and corresponding antisera, for the expression and detection of HAM-tagged proteins in mammalian cells. We show that the HAM tag dramatically improves the sensitivity of 35S-methionine labeling, and permits the analysis of Myc oncoprotein turnover even when HAM-tagged Myc is expressed at levels comparable to that of the endogenous protein. Because of the improved sensitivity provided by the HAM tag, the vectors and antisera described here should be useful for the analysis of protein synthesis and destruction at physiological levels of protein expression. 相似文献
73.
I. N. Semenchuk L. A. Taranova A. A. Kalenyuk P. V. Il’yasov A. N. Reshetilov 《Applied Biochemistry and Microbiology》2000,36(1):69-72
The operating and storage stability of a receptor element of an amperometric biosensor based on thePseudomonas rathonis strain T capable of degrading surfactants was tested. Microbial cells were immobilized by incorporation in gels (agar, agarose,
and calcium-alginate), polyvinyl alcohol membrane, adhesion to Chromatographic paper GF/A, or by cross-linking induced by
glutaric aldehyde. Incorporation of microbial cells in agar gel provides long-standing conservation of their activity and
viability during measurements of high concentrations of surfactants and allows the receptor element of the biosensor to be
rapidly recovered after measurements. 相似文献
74.
75.
Savignin, a potent thrombin inhibitor isolated from the salivary glands of the tick Ornithodoros savignyi (Acari: Argasidae). 总被引:4,自引:0,他引:4
A thrombin (E.C. 3.4.21.5) inhibitor, savignin, was isolated from the salivary glands of Ornithodoros savignyi by a combination of size exclusion, anion-exchange, and reversed-phase chromatography. The inhibitor has a molecular mass of 12,430.4 Da as determined by electrospray mass spectrometry. The behavior of savignin during anion-exchange chromatography indicated that it has an acidic pI. The available N-terminal sequence (residues 1-11) differed from that of ornithodorin with only one residue. Savignin inhibits thrombin-induced platelet aggregation, but has no effect on ADP- or collagen-induced aggregation. Kinetic studies indicated that savignin is a competitive, slow-, tight-binding inhibitor of alpha-thrombin (K(i) = 4.89 +/- 1.39 pM). Tight-binding kinetics showed that the inhibitor has a lower affinity for gamma-thrombin (K(i) = 22.3 +/- 5.9 nM). Plasmin, factor Xa, and trypsin are not inhibited by savignin. 相似文献
76.
D S Faffe G H Silva P M Kurtz E M Negri V L Capelozzi P R Rocco W A Zin 《Journal of applied physiology》2001,90(4):1400-1406
The dynamic mechanical properties of lung tissue and its contents of collagen and elastic fibers were studied in strips prepared from mice instilled intratracheally with saline (C) or silica [15 (S15) and 30 days (S30) after instillation]. Resistance, elastance, and hysteresivity were studied during oscillations at different frequencies on S15 and S30. Elastance increased from C to silica groups but was similar between S15 and S30. Resistance was augmented from C to S15 and S30 and was greater in S30 than in S15 at higher frequencies. Hysteresivity was higher in S30 than in C and S15. Silica groups presented a greater amount of collagen than did C. Elastic fiber content increased progressively along time. This increment was related to the higher amount of oxytalan fibers at 15 and 30 days, whereas elaunin and fully developed elastic fibers were augmented only at 30 days. Silicosis led not only to pulmonary fibrosis but also to fibroelastosis, thus assigning a major role to the elastic system in the silicotic lung. 相似文献
77.
Disseminated nocardiosis in three macaque monkeys 总被引:1,自引:0,他引:1
Extrapulmonary nocardiosis was diagnosed at necropsy in two rhesus monkeys (Macaca mulatta) and one pigtailed monkey (M. nemestrina) over a four-year period in a large primate center. Typical lesions were multiple pyogranulomatous foci in the liver, intestines, peritoneum, lung and brain. Partially acid-fast, branching, filamentous organisms were seen in all lesions. Nocardia sp. was isolated from two cases. We postulate that two of the monkeys were infected by the oral route because of the distribution of lesions. 相似文献
78.
79.
The marine bacteriumVibrio anguillarum causes disease in fish worldwide and is particularly devastating in aquaculture. Little is known about the ecology ofV. anguillarum in the environment and how this may relate to the pathogenicity of this organism. Combining membrane filtration and a species-specific DNA probe, culturableV. anguillarum cells were detected in water from three habitats and in chinook salmon (Onchorynchus tshawytscha) tissue samples. Results show that different marine habitats have a marked effect on cell numbers and that water temperature may play a role in the culturability and distribution ofV. anguillarum. Vibrio anguillarum was detected from the gills of salmon within 24 h of transfer of fingerlings from freshwater to seawater, with cell numbers reaching a concentration of 1.9 × 102 cells g–1 tissue 28 days post transfer.Vibrio anguillarum cell numbers were low in the colon throughout the study, andV. anguillarum was not detected in healthy kidney samples. The methodology reported in this paper allows the accurate quantification of culturableV. anguillarum cells and has allowed a preliminary study of the ecology of this species. 相似文献
80.
The fish pathogenVibrio anguillarum causes significant economic losses in commercially cultured fish species worldwide. At present, identification ofV. anguillarum requires conventional isolation and culturing techniques. Using differential hybridization, a 310 base pairV. anguillarum-specific DNA fragment was isolated for use as a probe. In specificity studies against 19 different bacterial species, including twoVibrio sp. and fish pathogens, and 223 marine bacterial isolates, the probe hybridized exclusively toV. anguillarum strains. The probe also strongly hybridizes to 7 of 9 serotypes tested, with serotype 09 giving a weak probe reaction and serotype O7 negative. The probe allows rapid and accurate detection of both pathogenic and environmental strains ofV. anguillarum. 相似文献