全文获取类型
收费全文 | 5784篇 |
免费 | 539篇 |
国内免费 | 6篇 |
出版年
2023年 | 32篇 |
2022年 | 64篇 |
2021年 | 146篇 |
2020年 | 88篇 |
2019年 | 110篇 |
2018年 | 153篇 |
2017年 | 120篇 |
2016年 | 217篇 |
2015年 | 293篇 |
2014年 | 353篇 |
2013年 | 375篇 |
2012年 | 525篇 |
2011年 | 521篇 |
2010年 | 303篇 |
2009年 | 274篇 |
2008年 | 370篇 |
2007年 | 366篇 |
2006年 | 342篇 |
2005年 | 263篇 |
2004年 | 288篇 |
2003年 | 226篇 |
2002年 | 246篇 |
2001年 | 67篇 |
2000年 | 55篇 |
1999年 | 49篇 |
1998年 | 65篇 |
1997年 | 38篇 |
1996年 | 32篇 |
1995年 | 34篇 |
1994年 | 25篇 |
1993年 | 21篇 |
1992年 | 31篇 |
1991年 | 29篇 |
1990年 | 22篇 |
1989年 | 16篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1984年 | 19篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 13篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1972年 | 6篇 |
1971年 | 6篇 |
排序方式: 共有6329条查询结果,搜索用时 15 毫秒
31.
Expression of a human cytomegalovirus gp58 antigenic domain fused to the hepatitis B virus nucleocapsid protein 总被引:1,自引:0,他引:1
Maryam R. Tarar Vincent C. Emery Tim J. Harrison 《FEMS immunology and medical microbiology》1996,16(3-4):183-192
Abstract Hepatitis B virus core antigen (HBcAg) has been used as a carrier for expression and presentation of a variety of heterologous viral epitopes in particulate form. The aim of this study was to produce hybrid antigens comprising HBcAg and an immunogenic epitope of human cytomegalovirus (HCMV). A direct comparison was made of amino and carboxyl terminal fusions in order to investigate the influence of position of the foreign epitope on hybrid core particle formation, antigenicity and immunogenicity. HCMV DNA encoding a neutralising epitope of the surface glycoprotein gp58 was either inserted at the amino terminus or fused to the truncated carboxyl terminus of HBcAg and expressed in Escherichia coli . The carboxyl terminal fusion (HBc3–144 -HCMV) was expressed at high levels and assembled into core like particles resembling native HBcAg. Protein with a similar fusion at the amino terminus (HCMV-HBc1–183 ) could not be purified or characterised immunologically, although it formed core like particles. HBc3–144 -HCMV displayed HBc antigenicity but HCMV antigenicity could not be detected by radioimmunoassay or western blotting using anti-HCMV monoclonal antibody 7–17 or an anti-HCMV human polyclonal antiserum. Following immunisation of rabbits with HBc3–144 -HCMV, a high titre of anti-HBc specific antibody was produced along with lower titres of HCMV/gp58 specific antibody. 相似文献
32.
Microtubules Orient the Mitotic Spindle in Yeast through Dynein-dependent Interactions with the Cell Cortex 总被引:31,自引:9,他引:22 下载免费PDF全文
Proper orientation of the mitotic spindle is critical for successful cell division in budding yeast. To investigate the mechanism of spindle orientation, we used a green fluorescent protein (GFP)–tubulin fusion protein to observe microtubules in living yeast cells. GFP–tubulin is incorporated into microtubules, allowing visualization of both cytoplasmic and spindle microtubules, and does not interfere with normal microtubule function. Microtubules in yeast cells exhibit dynamic instability, although they grow and shrink more slowly than microtubules in animal cells. The dynamic properties of yeast microtubules are modulated during the cell cycle. The behavior of cytoplasmic microtubules revealed distinct interactions with the cell cortex that result in associated spindle movement and orientation. Dynein-mutant cells had defects in these cortical interactions, resulting in misoriented spindles. In addition, microtubule dynamics were altered in the absence of dynein. These results indicate that microtubules and dynein interact to produce dynamic cortical interactions, and that these interactions result in the force driving spindle orientation. 相似文献
33.
The ant’s path integration system: a neural architecture 总被引:3,自引:0,他引:3
A model is developed by which path integration as observed in many animal species could be implemented neurobiologically.
The proposed architecture is able to describe the navigation behaviour of Cataglyphis ants, and that of other social insects, at the level of interacting neurons. The basic idea of this architecture is the concept
of activity patterns travelling along neural chains. Although experimental evidence has yet to be provided, this concept seems
biologically plausible and not limited to the navigation problem. Neural chains are able to represent variables by activity
patterns with high accuracy and temporal stability. Moreover, they are able to integrate incremental signals with high precision.
Cyclical chains of neurons show superior performance as soon as cyclical variables are to be represented and integrated. Finally,
representation of cyclical variables by travelling activity peaks allows simple approximations of goniometric functions as
they are used in path integration systems.
Received: 15 November 1994/Accepted in revised form: 30 May 1995 相似文献
34.
35.
Mutagenicity of 5,6-dimethoxysterigmatocystin, a metabolite from Aspergillus multicolor, in the Salmonella/microsome system. 总被引:1,自引:1,他引:0 下载免费PDF全文
The natural sterigmatocystin derivative, 5,6-dimethoxysterigmatocystin, was found to be a mutagen for Salmonella typhimurium strains TA98 and TA100 after metabolic activation in a mammalian microsome system. 相似文献
36.
Tim B. Bruhns 《Plant Systematics and Evolution》1981,139(1-2):1-10
Two homoeologous sets of chromosomes in pentaploidAllium neapolitanum
Cyr. (Liliaceae) are recognizable by their C-bands. The banding pattern is the same for one Californian and five Yugoslavian populations, suggesting a common chromosomal origin. Predominant meiotic association of identically banded homologues indicates a genomic formula of AA AI BB, confirms an allopolyploid origin, and argues against genetically controlled pairing. 相似文献
37.
Summary Specific detection of iota-Carrageenan (i-CAR) at the ultrastructural level has been obtained by coupling with ruthenium red (RR) — an electron microscopic stain. The i-CAR-RR complex showed electron density on carbon layers. Peritoneal macrophages were treated with the complex and after 3 h it caused the same morphological changes in macrophages as iota-Carrageenan alone. On the surfaces of macrophages, fine filamentous electron dense material — the i-CAR-RR complex — was detected. 相似文献
38.
Lectin-binding glycoproteins in seven populations of two burrowing nematode sibling species were probed with five different biotinylated lectins on Western blots, and differences were correlated with nematode ability to parasitize citrus and to overcome citrus rootstock resistance. Banding patterns of molecular weight standards were fit best by an exponential decay function, and a predictive equation was used to estimate molecular weights (r² = 0.999). A band (131 kDa) that labeled with the lectin Concanavalin A (Con A) occurred in extracts from cuticles and egg shells of populations of Radopholus citrophilus that parasitize citrus. Wheat germ agglutin labeled a band (58 kDa) in aqueous homogenates of populations that reproduce in roots of citrus rootstock normally resistant to burrowing nematodes. The two sibling species R. citrophilus and R. similis were distinguished by a high molecular weight Con A-labeled band (608 kDa) from cuticle and egg shells. Probing blots with the lectin Limulus polyphemus agglutinin indicated that each population contained a band (12-16 kDa) specifically inhibited by the addition of 25 mM neuraminic acid, suggesting that glycoproteins with sialic acid moieties are present in burrowing nematodes. 相似文献
39.
Factors affecting population density, group size and territory size of the European badger, Meles meles 总被引:4,自引:0,他引:4
This paper discusses the relationship between the distribution and biomass of the main prey of European badgers, Meles meles and the badgers group size, territory size and population density. The distribution of areas rich in earthworms, Lumbricus spp., is correlated with badger range size, whilst badger group size increases with the biomass of worms per badger territory and badger density increases with overall worm biomass. Regulation of badger density in an area is likely to take place through regulation of group size, in the absence of other factors such as persecution and lack of suitable sett-sites. 相似文献
40.
The genormic organization of the multiple actin DNA sequences in the lower eukaryote Physarum polycephalum was investigated by Mendelian mapping. Actin-homologous restriction endonuclease cleavage fragments detected by DNA blotting showed length polymorphisms when different strains were compared. These length polymorphisms were used as phenotypic markers for actin sequences in the genome. The meiotic assortment of the polymorphic restriction fragments was analysed, revealing four unlinked actin loci. The data for three-of the actin loci, ardB, C and D, are consistent with a single sequence or gene at each locus. The data for the other actin locus. ardA, is consistent with multiple linked actin sequences or genes. 相似文献