全文获取类型
收费全文 | 1119222篇 |
免费 | 91440篇 |
国内免费 | 1373篇 |
专业分类
1212035篇 |
出版年
2021年 | 17530篇 |
2020年 | 12510篇 |
2019年 | 16068篇 |
2018年 | 16577篇 |
2017年 | 15330篇 |
2016年 | 27168篇 |
2015年 | 41711篇 |
2014年 | 49662篇 |
2013年 | 75944篇 |
2012年 | 28962篇 |
2011年 | 15513篇 |
2010年 | 40790篇 |
2009年 | 42999篇 |
2008年 | 15793篇 |
2007年 | 13047篇 |
2006年 | 19905篇 |
2005年 | 21041篇 |
2004年 | 20441篇 |
2003年 | 18204篇 |
2002年 | 16487篇 |
2001年 | 20657篇 |
2000年 | 17521篇 |
1999年 | 21215篇 |
1998年 | 23843篇 |
1997年 | 23615篇 |
1996年 | 23446篇 |
1995年 | 21550篇 |
1994年 | 21431篇 |
1993年 | 20430篇 |
1992年 | 19063篇 |
1991年 | 17512篇 |
1990年 | 16300篇 |
1989年 | 17498篇 |
1988年 | 15943篇 |
1987年 | 15055篇 |
1986年 | 14441篇 |
1985年 | 16535篇 |
1984年 | 17871篇 |
1983年 | 15945篇 |
1982年 | 18092篇 |
1981年 | 17701篇 |
1980年 | 16449篇 |
1979年 | 13794篇 |
1978年 | 14199篇 |
1977年 | 13915篇 |
1976年 | 13269篇 |
1975年 | 12217篇 |
1974年 | 12277篇 |
1973年 | 12741篇 |
1972年 | 10477篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
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
82.
A putative GDP–GTP exchange factor is required for development of the excretory cell in Caenorhabditis elegans 下载免费PDF全文
Norio Suzuki Matthew Buechner Kiyoji Nishiwaki David H. Hall Hiroyuki Nakanishi Yoshimi Takai Naoki Hisamoto Kunihiro Matsumoto 《EMBO reports》2001,2(6):530-535
The Caenorhabditis elegans excretory cell extends tubular processes, called canals, along the basolateral surface of the epidermis. Mutations in the exc-5 gene cause tubulocystic defects in this canal. Ultrastructural analysis suggests that exc-5 is required for the proper placement of cytoskeletal elements at the apical epithelial surface. exc-5 encodes a protein homologous to guanine nucleotide exchange factors and contains motif architecture similar to that of FGD1, which is responsible for faciogenital dysplasia. exc-5 interacts genetically with mig-2, which encodes Rho GTPase. These results suggest that EXC-5 controls the structural organization of the excretory canal by regulating Rho family GTPase activities. 相似文献
83.
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
84.
85.
86.
87.
V. Grant 《Plant Systematics and Evolution》2001,230(1-2):89-96
This paper deals with the use of cladistic methods and cladograms in phylogeny reconstruction in plant groups containing
numerous taxa. How accurate are the cladograms as to details? Accuracy tests at the level of details require an independently
known phylogeny, which excludes most plant groups, but such tests can be carried out in domesticated and experimental plant
groups which have documented pedigrees. Four such tests are known and are presented here: a new case in Gilia and three previously published cases in Avena, Hordeum, and Helianthus. The four cases include domesticated and experimental plants, use of morphological and molecular evidence, and presence of
dichotomous as well as reticulate phylogenies. The cladograms of the four plant groups all differ in significant details from
the known pedigrees. These results are discussed in relation to problems of interpretation of cladograms.
Received March 21, 2000 Accepted August 16, 2001 相似文献
88.
89.
90.
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