全文获取类型
收费全文 | 1171218篇 |
免费 | 121848篇 |
国内免费 | 642篇 |
专业分类
1293708篇 |
出版年
2018年 | 10243篇 |
2016年 | 14133篇 |
2015年 | 19338篇 |
2014年 | 22760篇 |
2013年 | 32540篇 |
2012年 | 36180篇 |
2011年 | 36601篇 |
2010年 | 24806篇 |
2009年 | 22769篇 |
2008年 | 32540篇 |
2007年 | 33661篇 |
2006年 | 31661篇 |
2005年 | 30610篇 |
2004年 | 30346篇 |
2003年 | 29174篇 |
2002年 | 28212篇 |
2001年 | 50466篇 |
2000年 | 50947篇 |
1999年 | 40926篇 |
1998年 | 14963篇 |
1997年 | 15547篇 |
1996年 | 14723篇 |
1995年 | 13999篇 |
1994年 | 13711篇 |
1993年 | 13523篇 |
1992年 | 34508篇 |
1991年 | 33693篇 |
1990年 | 33041篇 |
1989年 | 32246篇 |
1988年 | 30052篇 |
1987年 | 28379篇 |
1986年 | 26622篇 |
1985年 | 26736篇 |
1984年 | 22400篇 |
1983年 | 19157篇 |
1982年 | 14835篇 |
1981年 | 13501篇 |
1980年 | 12719篇 |
1979年 | 21280篇 |
1978年 | 16599篇 |
1977年 | 15176篇 |
1976年 | 14078篇 |
1975年 | 15736篇 |
1974年 | 16605篇 |
1973年 | 16454篇 |
1972年 | 14986篇 |
1971年 | 13440篇 |
1970年 | 11689篇 |
1969年 | 11160篇 |
1968年 | 10173篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
851.
S E Klebanoiv Iu M Bochina A L Berman 《Zhurnal evoliutsionno? biokhimii i fiziologii》1991,27(3):289-294
The method of cDNA sequences comparison is suggested. The method consists of constructing the dot matrixes for each codon position separately. The fastest disappearance of the information about relationship is observed when the third nucleotides in codon are compared, and the comparison of the second nucleotides in codon turned out to be effective so as the comparison under acids. 相似文献
852.
Histopathological effects of ectoparasites on integument were examined for a wild population of the side-blotched lizard Uta stansburiana. These included the trombiculid Neotrombicula californica, the pterygosomatid mite Geckobiella texana; the macronyssid mite Ophionyssus natricis (Macronyssidae) and the ixodid tick Ixodes pacificus. A diffuse inflammatory response occurred at the site of chigger and tick attachment which consisted of histiocyte, heterophil, fibroblast and lymphocyte infiltration that often extended into the dermis. Granuloma formation also was noted. The most prevalent parasite was N. californica which frequently occurred in large aggregations above the eyelids. Ectoparasites were most abundant from February through April. 相似文献
853.
An electron-microscopic study of the topography of carbohydrate residues on the surface of the cell body membrane of cultured spinal neurons was carried out using lectins from wheat (WGA) and snail (HPL), labeled with colloidal gold, as specific molecular probes. Mathematical methods of analysis suggested a set of surface markers, from the distribution of particles observed in electron micrographs of random sections, corresponding to two random functions. Analysis of these functions allows the required quantitative characteristics to be obtained. The Monte Carlo reconstructing model is described, and results of its use (based on the aforementioned experimental data) are demonstrated in the form of "averaged" surface topography of the studied markers in a limited section of the membrane. The results obtained are discussed in connection with cooperative properties of the membrane.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 5, pp. 595–603, September–October, 1991. 相似文献
854.
855.
856.
Extracellular complementation of a developmental mutation implicates a small sporulation protein in aerial mycelium formation by S. coelicolor 总被引:19,自引:0,他引:19
The filamentous bacterium S. coelicolor differentiates by forming aerial hyphae, which protrude into the air and metamorphose into chains of spores. Aerial hyphae formation is associated with the production of a small, abundant protein, SapB, which is present in a zone around colonies of differentiating bacteria. Production of SapB is impaired in bld mutants, which are blocked in aerial hyphae formation, but not in whi mutants in which spore formation is prevented. We report that aerial hyphae formation by a newly identified bld mutant is restored by juxtaposition of the mutant near colonies of SapB-producing bacteria or by the application of the purified protein near mutant colonies. These observations implicate SapB in aerial mycelium formation and suggest that SapB is a morphogenetic protein that enables hyphae on the surface of colonies to grow into the air. 相似文献
857.
858.
859.
Tyrone M. Reyes 《The Western journal of medicine》1991,154(5):632-633
The international community has perspective and experience that will freshen our approaches to rehabilitation. Martin Grabois, MD*, editor of this special section, has gathered articles written by experts from other countries. The intention is to stimulate thought, discussion, and action—and to broaden horizons. 相似文献
860.