全文获取类型
收费全文 | 13666篇 |
免费 | 1456篇 |
国内免费 | 2篇 |
专业分类
15124篇 |
出版年
2021年 | 173篇 |
2020年 | 110篇 |
2019年 | 122篇 |
2018年 | 136篇 |
2017年 | 144篇 |
2016年 | 225篇 |
2015年 | 363篇 |
2014年 | 463篇 |
2013年 | 605篇 |
2012年 | 646篇 |
2011年 | 637篇 |
2010年 | 431篇 |
2009年 | 337篇 |
2008年 | 508篇 |
2007年 | 576篇 |
2006年 | 506篇 |
2005年 | 514篇 |
2004年 | 488篇 |
2003年 | 431篇 |
2002年 | 471篇 |
2001年 | 412篇 |
2000年 | 400篇 |
1999年 | 344篇 |
1998年 | 181篇 |
1997年 | 155篇 |
1996年 | 150篇 |
1995年 | 127篇 |
1994年 | 149篇 |
1993年 | 133篇 |
1992年 | 243篇 |
1991年 | 240篇 |
1990年 | 244篇 |
1989年 | 220篇 |
1988年 | 226篇 |
1987年 | 244篇 |
1986年 | 184篇 |
1985年 | 208篇 |
1984年 | 186篇 |
1983年 | 180篇 |
1982年 | 146篇 |
1981年 | 133篇 |
1980年 | 126篇 |
1979年 | 178篇 |
1978年 | 169篇 |
1977年 | 129篇 |
1976年 | 130篇 |
1975年 | 139篇 |
1974年 | 146篇 |
1973年 | 124篇 |
1972年 | 149篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
Human hypoxanthine-guanine phosphoribosyltransferase 总被引:6,自引:0,他引:6
J M Wilson R Kobayashi I H Fox W N Kelley 《The Journal of biological chemistry》1983,258(10):6458-6460
A mutant form of human hypoxanthine-guanine phosphoribosyltransferase (HPRTToronto) was isolated from erythrocytes of a male patient with gout due to a partial deficiency of enzyme activity. The tryptic peptides of HPRTToronto were mapped by reverse-phase high pressure liquid chromatography in an attempt to define the precise abnormality in its primary structure. Sequence analysis of the single aberrant peptide in HPRTToronto revealed an arginine to glycine amino acid substitution at position 50. A single nucleotide change in the codon for arginine 50 (CGA leads to GGA) could explain this substitution. 相似文献
24.
The preparation and kinetics of lactate dehydrogenase attached to water-insoluble particles and sheets 总被引:2,自引:2,他引:0 下载免费PDF全文
1. The preparation of lactate dehydrogenase covalently attached to anion-exchange cellulose particles and sheets by use of a dichloro-sym-triazinyl dyestuff, Procion brilliant orange MGS, is described. 2. The stability and kinetic properties of these preparations were investigated. 3. An equation is derived to describe the change in concentration of a substrate when passed through a uniform bed of a substrate-inhibited enzyme. A number of theoretical curves are shown to illustrate the system. 4. A titrimetric assay for lactate dehydrogenase is described, and shown to be stoicheiometric over the range pH5.0-9.2. 5. The results are discussed in relation to previous work, and the effects of charged groups on the support, and of the diffusion film surrounding any particle in suspension, are treated qualitatively. 相似文献
25.
26.
P W Blick M W Flowers A K Marsden D H Wilson A T Ghoneim 《BMJ (Clinical research ed.)》1980,281(6233):111-112
A four-way, double-blind, prospective trial of treatment of abscesses by incision, curettage, and primary closure with and without antibiotic cover (clindamycin injection before operation or capsules after operation, or both) was conducted. There was no appreciable difference in mean healing time between the patients given both the antibiotic injection and the antibiotic capsules and those given the injection and placebo capsules, whereas healing times in those given the placebo injection and antibiotic capsules or placebo only were appreciably longer. Four of the patients who were not given the antibiotic injection developed bacteraemia; one patient who was given the antibiotic injection also developed a bacteraemia, but this was caused by clindamycin-resistant bacteria. These results show that a single injection of an effective antibiotic before operation is sufficient to protect the patient against bacteraemia and permit optimum healing. 相似文献
27.
Peter W. Wilson Katie E. Osterday Aaron F. Heneghan Anthony D. J. Haymet 《The Journal of biological chemistry》2010,285(45):34741-34745
In this study, we examined the effects that antifreeze proteins have on the supercooling and ice-nucleating abilities of aqueous solutions. Very little information on such nucleation currently exists. Using an automated lag time apparatus and a new analysis, we show several dilution series of Type I antifreeze proteins. Our results indicate that, above a concentration of ∼8 mg/ml, ice nucleation is enhanced rather than hindered. We discuss this unexpected result and present a new hypothesis outlining three components of polar fish blood that we believe affect its solution properties in certain situations. 相似文献
28.
Mutations in Aprataxin cause the neurodegenerative syndrome ataxia oculomotor apraxia type 1. Aprataxin catalyzes removal of adenosine monophosphate (AMP) from the 5′ end of a DNA strand, which results from an aborted attempt to ligate a strand break containing a damaged end. To gain insight into which DNA lesions are substrates for Aprataxin action in vivo, we deleted the Saccharomyces cerevisiae HNT3 gene, which encodes the Aprataxin homolog, in combination with known DNA repair genes. While hnt3Δ single mutants were not sensitive to DNA damaging agents, loss of HNT3 caused synergistic sensitivity to H2O2 in backgrounds that accumulate strand breaks with blocked termini, including apn1Δ apn2Δ tpp1Δ and ntg1Δ ntg2Δ ogg1Δ. Loss of HNT3 in rad27Δ cells, which are deficient in long-patch base excision repair (LP-BER), resulted in synergistic sensitivity to H2O2 and MMS, indicating that Hnt3 and LP-BER provide parallel pathways for processing 5′ AMPs. Loss of HNT3 also increased the sister chromatid exchange frequency. Surprisingly, HNT3 deletion partially rescued H2O2 sensitivity in recombination-deficient rad51Δ and rad52Δ cells, suggesting that Hnt3 promotes formation of a repair intermediate that is resolved by recombination. 相似文献
29.
30.