全文获取类型
收费全文 | 3342篇 |
免费 | 324篇 |
专业分类
3666篇 |
出版年
2021年 | 49篇 |
2020年 | 32篇 |
2019年 | 28篇 |
2018年 | 32篇 |
2017年 | 29篇 |
2016年 | 50篇 |
2015年 | 90篇 |
2014年 | 90篇 |
2013年 | 161篇 |
2012年 | 168篇 |
2011年 | 157篇 |
2010年 | 125篇 |
2009年 | 88篇 |
2008年 | 150篇 |
2007年 | 136篇 |
2006年 | 128篇 |
2005年 | 130篇 |
2004年 | 103篇 |
2003年 | 115篇 |
2002年 | 123篇 |
2001年 | 64篇 |
2000年 | 69篇 |
1999年 | 63篇 |
1998年 | 57篇 |
1997年 | 45篇 |
1996年 | 45篇 |
1995年 | 31篇 |
1994年 | 37篇 |
1993年 | 45篇 |
1992年 | 64篇 |
1991年 | 76篇 |
1990年 | 66篇 |
1989年 | 59篇 |
1988年 | 51篇 |
1987年 | 65篇 |
1986年 | 66篇 |
1985年 | 57篇 |
1984年 | 57篇 |
1983年 | 38篇 |
1982年 | 42篇 |
1981年 | 41篇 |
1980年 | 32篇 |
1979年 | 42篇 |
1978年 | 30篇 |
1977年 | 32篇 |
1976年 | 28篇 |
1975年 | 33篇 |
1974年 | 32篇 |
1973年 | 36篇 |
1971年 | 29篇 |
排序方式: 共有3666条查询结果,搜索用时 0 毫秒
1.
B G Atkinson 《The Journal of experimental zoology》1973,184(3):335-340
2.
3.
Joshua D. Doyle Jennifer E. Stencel-Baerenwald Courtney A. Copeland Jillian P. Rhoads Judy J. Brown Kelli L. Boyd James B. Atkinson Terence S. Dermody 《PLoS pathogens》2015,11(3)
Reovirus is a nonenveloped mammalian virus that provides a useful model system for studies of viral infections in the young. Following internalization into host cells, the outermost capsid of reovirus virions is removed by endosomal cathepsin proteases. Determinants of capsid disassembly kinetics reside in the viral σ3 protein. However, the contribution of capsid stability to reovirus-induced disease is unknown. In this study, we found that mice inoculated intramuscularly with a serotype 3 reovirus containing σ3-Y354H, a mutation that reduces viral capsid stability, succumbed at a higher rate than those infected with wild-type virus. At early times after inoculation, σ3-Y354H virus reached higher titers than wild-type virus at several sites within the host. Animals inoculated perorally with a serotype 1 reassortant reovirus containing σ3-Y354H developed exaggerated myocarditis accompanied by elaboration of pro-inflammatory cytokines. Surprisingly, unchallenged littermates of mice infected with σ3-Y354H virus displayed higher titers in the intestine, heart, and brain than littermates of mice inoculated with wild-type virus. Together, these findings suggest that diminished capsid stability enhances reovirus replication, dissemination, lethality, and host-to-host spread, establishing a new virulence determinant for nonenveloped viruses. 相似文献
4.
Reconstitution of RecBC DNase activity from purified Escherichia coli RecB and RecC proteins 总被引:8,自引:0,他引:8
I D Hickson C N Robson K E Atkinson L Hutton P T Emmerson 《The Journal of biological chemistry》1985,260(2):1224-1229
The Escherichia coli RecB protein, normally synthesized in low amounts, has been amplified by linkage of the recB gene to the phage lambda leftward promoter in an expression plasmid. From strains harboring this plasmid, RecB protein has been purified to homogeneity by a simple procedure which includes affinity chromatography on a column of RecC protein bound to agarose. The purified RecB protein has DNA-dependent ATPase activity but no exonuclease activity. RecC protein alone has neither ATPase nor exonuclease activity. However, when combined together, the RecB and RecC proteins show the ATP-dependent double-stranded exonuclease properties characteristic of the RecBC DNase. 相似文献
5.
We have used internal deletions of multiples of seven residues to change the phase of the 28-residue charge repeat in a light meromyosin cDNA construct expressed in Escherichia coli. The solubility behaviour of these mutants was similar to that of the wild-type material, but the molecular packing in the aggregates formed at low ionic strength was different. Whereas wild-type material formed paracrystals in which molecules were in close contact over most of their length, molecules in the paracrystals formed by the mutants were in close contact for only a short distance, which was just short enough to exclude the deletion from the overlap. These data indicate that, although the 28-residue charge periodicity is important in myosin molecular interactions, it is probably not the major driving force for myosin assembly and instead influences the detailed axial stagger of the interacting molecules. 相似文献
6.
7.
A polymorphism of the complement regulatory protein MCP (membrane cofactor protein or gp45-70) 总被引:6,自引:0,他引:6
L Ballard T Seya J Teckman D M Lublin J P Atkinson 《Journal of immunology (Baltimore, Md. : 1950)》1987,138(11):3850-3855
Membrane cofactor protein (MCP or gp45-70) is a recently described regulatory glycoprotein of the complement system which binds iC3 or C3b and is present on human platelets, T cells, B cells, monocytes, and mononuclear-derived cell lines. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, MCP migrates as a doublet with an Mr of the upper band of 63,000 and the lower band of 58,000. The same pattern was found on all cell populations in a given individual and was stable over time. In order to further characterize the two band pattern on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, MCP was isolated by affinity chromatography or immunoprecipitation from 72 healthy unrelated donors. All individuals expressed both bands and, based on the densitometric scanning of gels, three patterns were noted: upper band predominant in 65%, approximately equal distribution of upper and lower bands in 29%, and lower band predominant in 6%. These observed phenotypic frequencies fit with expectations based on Hardy-Weinberg equilibrium for a two-allele system. Family studies also support this model as none of the 26 offspring had a phenotype that deviated from the expected, assuming an autosomal codominant model of inheritance. These results are consistent with a simple two-allele system that controls the expression of the two bands of MCP. 相似文献
8.
The isolation and characterization of bacteriophages infecting obligately thermophilic strains of Bacillus 总被引:2,自引:0,他引:2
R J Sharp S I Ahmad A Munster B Dowsett T Atkinson 《Journal of general microbiology》1986,132(6):1709-1722
Twenty-four thermophilic bacteriophages have been isolated from diverse sources such as compost, soil, silage and rotting straw. Although considerable individual host specificity was observed, the phages were able to infect most of the major taxonomic groups of Bacillus thermophiles. The phages varied considerably in morphology and size; the phage heads were either cylindrical or polyhedral with tails varying in length between 15 and 500 nm. Most of the phages were stable at 50 degrees C for 4-5 h but at 70 degrees C the plaque-forming units decreased by between 10(2)- and 10(7)-fold in 2 h. The DNA of morphologically similar phages was examined by restriction enzyme analysis, and some differences in the DNA fragment patterns were found. Efficiency of plating data indicated that 'B. caldotenax' has a restriction and modification system. These phages may be valuable for the study of the genetics of thermophilic bacilli: transduction of 'B. caldotenax' and 'B. caldovelox' by phage JS017 has been observed. 相似文献
9.
J F Ensley Z Maciorowski H Pietraszkiewicz M Hassan J Kish M Al-Sarraf J Jacobs A Weaver D Atkinson J Crissman 《Cytometry》1987,8(5):488-493
Intense interest in advanced squamous cell cancers of the head and neck (SCC of H&N) has resulted from the recent progress made in tumor responses with chemotherapy and radiotherapy. Unfortunately, the response patterns and clinical outcome of such patients are not adequately predicted on an individual patient basis using clinical parameters or conventional morphology. The study of flow cytometrically determined cellular parameters in such tumors is therefore of interest, but is hindered by inadequate tumor preparative technology. The previous article (10) in this journal describes the use of a murine SCC tumor, LC12, which was employed for comparative testing and determination of optimum techniques of preparation for this tumor. This report describes the application of these techniques to 144 specimens of human SCC of H&N. The mean total yield for these specimens is 7.4 X 10(7) cells/g of tissue. The mean viable enzymatic yield (3.3 X 10(7) cells/g) was higher than the mean viable mechanical yield (2.0 X 10(7) cells/g) except when lymph nodes were the source of the specimen (5.4 X 10(7) cells/g). The mean dye exclusion viability from enzymatically dissociated specimens were above 90%. Significant aneuploidal subpopulation losses were evident in mechanically dissociated and enucleated specimens. 65% of the enzymatically dissociated specimens were successfully cultured with a mean cloning efficiency of 2.1 X 10(-3). Preparative techniques derived from comparative testing with a murine standard tumor have been successfully applied to 144 specimens of SCC of H&N with resultant high yields and excellent viability. Technical problems detected during the preliminary testing with LC12 were confirmed in the human tumors. 相似文献
10.
The effect of concanavalin A on the rat electro-olfactogram. Differential inhibition of odorant response. 总被引:1,自引:1,他引:0 下载免费PDF全文
When the rat olfactory mucosa is treated with concanavalin A, it subsequently shows diminished sensitivity towards 60% of the 112 odorants tested (as judged by the amplitude of the electro-olfactogram response). Odorants containing four to six carbon atoms tend to show the largest (absolute) diminutions, suggesting a receptor for this kind of odorant, although the structural specificity is weak. The receptor seems to be of particular importance in the detection of thiols, carboxylic acids and hydrocarbons of the above size, since these compounds loose the highest proportion of their original signal. The concanavalin A appears to be binding to the glycan of one or more cell-surface proteins. The binding may be at, or close to, at least one odorant receptor. 相似文献