全文获取类型
收费全文 | 2178篇 |
免费 | 202篇 |
出版年
2022年 | 15篇 |
2021年 | 31篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 27篇 |
2017年 | 25篇 |
2016年 | 49篇 |
2015年 | 83篇 |
2014年 | 102篇 |
2013年 | 120篇 |
2012年 | 187篇 |
2011年 | 164篇 |
2010年 | 101篇 |
2009年 | 110篇 |
2008年 | 128篇 |
2007年 | 148篇 |
2006年 | 127篇 |
2005年 | 135篇 |
2004年 | 104篇 |
2003年 | 111篇 |
2002年 | 106篇 |
2001年 | 37篇 |
2000年 | 19篇 |
1999年 | 33篇 |
1998年 | 33篇 |
1997年 | 33篇 |
1996年 | 27篇 |
1995年 | 29篇 |
1994年 | 21篇 |
1993年 | 22篇 |
1992年 | 31篇 |
1991年 | 10篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1979年 | 8篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1972年 | 7篇 |
1970年 | 3篇 |
1968年 | 4篇 |
1967年 | 3篇 |
1966年 | 3篇 |
1964年 | 3篇 |
排序方式: 共有2380条查询结果,搜索用时 109 毫秒
1.
2.
Abstract Immunoblotting profiles of whole or protease-K-digested organisms with homologous antisera demonstrated the presence of a characteristic ladder pattern of smooth LPS in Treponema phagedenis . Periodic acid silver staining of SDS-PAGE gels confirmed these findings. However, when heterologous or homologous serum was reacted with Treponema pallidum , no such pattern or cross-reactions were observed. The significance of apparent absence of LPS in T. pallidum is discussed. 相似文献
3.
The biosynthesis of glyantrypine from radiolabelled amino acid precursors has been shown experimentally to involve anthranilic acid, tryptophan and glycine. Low values for percentage incorporation of radiolabel into glyantrypine were partly influenced by a complex array of other novel alkaloids shown by the radiolabelling experiments to be related to glyantrypine. Interpretation of radiolabel incorporation from [14C-carboxyl]-anthranilic acid into microbial metabolites seen to contain an anthranilyl moiety in various biosynthetic arrangements is discussed. The possibility of diversion of anthranilic acid from the kynurenine pathway to glyantrypine biosynthesis is recognised. 相似文献
4.
Summary We have made pairwise comparisons between the coding sequences of 21 genes from coldblooded vertebrates and 41 homologous sequences from warm-blooded vertebrates. In the case of 12 genes, GC levels were higher, especially in third codon positions, in warm-blooded vertebrates compared to cold-blooded vertebrates. Six genes showed no remarkable difference in GC level and three showed a lower level. In the first case, higher GC levels appear to be due to a directional fixation of mutations, presumably under the influence of body temperature (see Bernardi and Bernardi 1986b). These GC-richer genes of warm-blooded vertebrates were located, in all cases studied, in isochores higher in GC than those comprising the homologous genes of cold-blooded vertebrates. In the third case, increases appear to be due to a limited formation of GC-rich isochores which took place in some cold-blooded vertebrates after the divergence of warm-blooded vertebrates. The directional changes in the GC content of coding sequences and the evolutionary conservation of both increased and unchanged GC levels are in keeping with the existence of compositional constraints on the genome. 相似文献
5.
6.
Bacterial flagellar diversity and significance in pathogenesis 总被引:4,自引:0,他引:4
Bacterial flagella are structurally diverse, ranging from the thoroughly investigated model examples found in Escherichia coli and Salmonella typhimurium to the more exotic sheathed flagella of, for example, Helicobacter pylori, and the complex multi-flagellin endoflagella found in many spirochaetes. We summarize some of the emerging structural and genetic findings relating to these more novel flagellar types, and outline their possible significance in the pathogenicity of some medically important bacteria. 相似文献
7.
A. F. Travers E. Burns N. D. Penn S. C. Mitchell G. P. Mulley 《BMJ (Clinical research ed.)》1992,304(6831):878-879
OBJECTIVE--To assess the quality of toilet facilities available for disabled people in a large provincial teaching hospital. DESIGN--Survey of toilet facilities for patients on the wards and in the outpatient department. SETTING--Teaching hospital in Leeds. RESULTS--Although the quality of toilet facilities varied, none met the standards recommended by the British Standards Institution. The worst facilities were found on a ward accommodating elderly patients, where the toilets were unsuitable for use by disabled people and bedside commodes had to be used instead. CONCLUSION--Toilet provision within a major hospital failed to meet standards required for disabled people. Admission to hospital may therefore result in loss of independence and dignity. If hospitals are to be centres of excellence, greater consideration must be given to the requirements of disabled people in the design of new wards, and current inadequate facilities should be upgraded. 相似文献
8.
Low-molecular-weight constituents of isolated insulin-secretory granules. Bivalent cations, adenine nucleotides and inorganic phosphate. 总被引:14,自引:3,他引:11
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The concentrations of Zn2+, Ca2+, Mg2+, Pi and adenine nucleotides were determined in insulin-secretory granules prepared from a transplantable rat insulinoma. Differential and density-gradient centrifugation analyses revealed that Zn2+ in this tissue was principally localized in the secretory granule, a second major fraction being found in association with cytosolic proteins. Pi was principally recovered in the latter fraction, whereas Ca2+ and Mg2+ were more widely distributed. Intragranular ion-distribution experiments suggested that Zn2+ was complexed mainly to insulin and its precursor forms and remained in the granule in an insoluble state. The Zn2+/insulin ratio (0.54) was greater than that expected for insulin molecules having two centrally co-ordinated Zn2+ atoms/hexamer, but less than the maximal Zn2+-binding capacity of the molecule. Most of the granular Ca2+, Mg2+ and Pi was released in a soluble form when granules were disrupted by sonication. Simulation in vitro of the ionic composition of the granule suggested that up to 90% of its Ca2+ was complexed to Pi and adenine nucleotides. Granular macromolecules also bound Ca2+, as shown by equilibrium-dialysis studies of granule lysates. However, such binding was displaced by Mg2+. Examination of the efflux of Ca2+ from granules incubated in iso-osmotic suspensions at 37 degrees C suggested that the passive permeability of the granule membrane to Ca2+ was very low. Nevertheless, more than 50% of the granular Ca2+ was rapidly released in an ionized form on hypo-osmotic or detergent-induced disruption of the granule membrane. This may represent a potentially mobilizable pool of Ca2+ in vivo. 相似文献
9.
10.