全文获取类型
收费全文 | 3733篇 |
免费 | 591篇 |
国内免费 | 2篇 |
专业分类
4326篇 |
出版年
2021年 | 49篇 |
2019年 | 40篇 |
2018年 | 45篇 |
2016年 | 62篇 |
2015年 | 105篇 |
2014年 | 111篇 |
2013年 | 132篇 |
2012年 | 171篇 |
2011年 | 180篇 |
2010年 | 135篇 |
2009年 | 99篇 |
2008年 | 153篇 |
2007年 | 147篇 |
2006年 | 128篇 |
2005年 | 128篇 |
2004年 | 130篇 |
2003年 | 113篇 |
2002年 | 140篇 |
2001年 | 120篇 |
2000年 | 113篇 |
1999年 | 99篇 |
1998年 | 46篇 |
1997年 | 40篇 |
1996年 | 46篇 |
1995年 | 43篇 |
1994年 | 47篇 |
1993年 | 41篇 |
1992年 | 87篇 |
1991年 | 91篇 |
1990年 | 76篇 |
1989年 | 81篇 |
1988年 | 95篇 |
1987年 | 75篇 |
1986年 | 70篇 |
1985年 | 55篇 |
1984年 | 52篇 |
1983年 | 51篇 |
1982年 | 37篇 |
1981年 | 54篇 |
1980年 | 43篇 |
1979年 | 62篇 |
1978年 | 47篇 |
1977年 | 44篇 |
1976年 | 40篇 |
1975年 | 37篇 |
1974年 | 61篇 |
1973年 | 60篇 |
1972年 | 39篇 |
1970年 | 36篇 |
1967年 | 39篇 |
排序方式: 共有4326条查询结果,搜索用时 15 毫秒
91.
92.
Crystals of a sarcoplasmic Ca(2+)-binding protein from the protochordate amphioxus have been grown from solutions of ammonium sulfate. The crystals are orthorhombic, space group C222(1), with unit cell axes a = 59.6(1) A, b = 81.3(1) A and c = 82.4(1) A. There is one molecule in the asymmetric unit. The crystals diffract beyond 2.5 A and show less than 20% decline in diffraction intensities after a three day exposure to X-rays from a laboratory rotating anode source. 相似文献
93.
Clostridium novyi type B alpha toxin was purified to homogeneity and shown to have a molecular weight of 200 kD by SDS polyacrylamide gel electrophoresis. The toxin was toxoided and used to produce a pair of non-interfering monoclonal antibodies. Their specificity was confirmed by immunoblotting and bioassay. The monoclonal antibodies were used to develop an enzyme immunoassay which was more sensitive than bioassay, and permitted less than 1 ng/ml toxin to be detected in a rapid 10 min assay format. Use of the assay can eliminate the requirement for in vivo testing of novyi toxin and toxoid, provided measurements of biological activity are not required. Because of its speed and sensitivity, the assay can be used to monitor toxin production during fermentation and as an alternative to bioassay to measure antigen content during toxoiding and vaccine formulation. 相似文献
94.
K S Lau W J Herring J L Chuang M McKean D J Danner R P Cox D T Chuang 《The Journal of biological chemistry》1992,267(33):24090-24096
95.
96.
97.
Wayne Chris Hawkes Calvin C. Willhite Kimberly A. Craig Stanley T. Omaye Douglas N. Cox Wai Nang Choy Andrew G. Hendrickx 《Biological trace element research》1992,35(3):281-297
Forty pregnant long-tailed macaques were treated daily for 30 d with 0, 25, 150 or 300 μg selenium as L-selenomethionine/kg
body weight. Erythrocyte and plasma selenium and glutathione peroxidase specific activities, hair and fecal selenium, and
urinary selenium excretion were increased by and were linearly related to L-selenomethionine dose. Hair selenium was most
sensitive to L-selenomethionine dose, with an 84-fold increase in the 300 μg selenium/(kg-d) group relative to controls (r=0.917). Daily urinary selenium excretion (80-fold,r=0.958), plasma selenium (22-fold,r=0.885), erythrocyte selenium (24-fold,r=0.920), and fecal selenium (18-fold,r=0.911) also responded strongly to L-selenomethionine. Erythrocyte and plasma glutathione peroxidase specific activities increased
154% and 69% over controls, respectively. Toxicity was associated with erythrocyte selenium >2.3 μg/mL, plasma selenium >2.8
μg/mL, and hair selenium >27 μg/g. Plasma, erythrocyte, and hair selenium concentrations may be useful for monitoring and
preventing the toxicity of L-selenomethionine administered to humans in cancer chemoprevention trials. 相似文献
98.
C W Fisher K S Lau C R Fisher R M Wynn R P Cox D T Chuang 《Biochemical and biophysical research communications》1991,174(2):804-809
We have amplified the cDNA for the transacylase (E2) subunit of the branched-chain alpha-ketoacid dehydrogenase (BCKAD) complex from a thiamine-responsive MSUD cell line (WG-34) by the polymerase chain reaction. Sequencing of the amplified WG-34 cDNA showed a 17-bp insertion (AAATACCTTGTTACCAG) apparently resulting from an aberrant splicing of the E2 gene, and a missense (T----G) mutation that changes Phe215 to Cys in the E2 subunit. The existence of these two mutations was confirmed by probing the amplified E2 cDNA or genomic DNA with allele-specific oligonucleotides. The above results support the thesis that the thiamine-responsive MSUD patient (WG-34) is a compound heterozygote at the E2 locus. The implication of the E2 mutations for the thiamine-responsiveness observed in this patient is discussed. 相似文献
99.
PCR analysis of dystrophin gene mutation and expression. 总被引:2,自引:0,他引:2
J S Chamberlain N J Farwell J R Chamberlain G A Cox C T Caskey 《Journal of cellular biochemistry》1991,46(3):255-259
100.
Maple syrup urine disease (MSUD) is caused by the deficiency of the mitochondrial branched-chain alpha-keto acid dehydrogenase complex. The multienzyme complex is a macromolecule (Mr 4 X 10(6] consisting of at least six distinct subunits. In this study, the human E1 beta gene (BCKDHB) has been localized to human chromosome 6 by hybrid somatic cell analysis, and regionally assigned to chromosome bands 6p21-22 by in situ hybridization. The E2 gene (DBT), which was previously localized to chromosome 1, is regionally assigned to the chromosome band 1p31 also by in situ hybridization. Localization of the E1 beta gene to chromosome 6p21-22 assigns another major human disease locus to a region that contains several important genes, including the major histocompatability complex, tumor necrosis factor, and heat-shock protein HSP70. Mapping of the E1 beta and the E2 genes may provide information for the linkage analysis of MSUD families with mutations in these two loci. 相似文献