全文获取类型
收费全文 | 3476篇 |
免费 | 424篇 |
国内免费 | 2篇 |
出版年
2021年 | 34篇 |
2016年 | 52篇 |
2015年 | 71篇 |
2014年 | 80篇 |
2013年 | 118篇 |
2012年 | 150篇 |
2011年 | 144篇 |
2010年 | 94篇 |
2009年 | 85篇 |
2008年 | 127篇 |
2007年 | 128篇 |
2006年 | 126篇 |
2005年 | 134篇 |
2004年 | 137篇 |
2003年 | 124篇 |
2002年 | 124篇 |
2001年 | 87篇 |
2000年 | 91篇 |
1999年 | 60篇 |
1998年 | 47篇 |
1997年 | 43篇 |
1996年 | 29篇 |
1995年 | 34篇 |
1994年 | 42篇 |
1993年 | 45篇 |
1992年 | 51篇 |
1991年 | 71篇 |
1990年 | 66篇 |
1989年 | 48篇 |
1988年 | 61篇 |
1987年 | 70篇 |
1986年 | 53篇 |
1985年 | 69篇 |
1984年 | 62篇 |
1983年 | 64篇 |
1982年 | 32篇 |
1981年 | 49篇 |
1980年 | 55篇 |
1979年 | 61篇 |
1978年 | 46篇 |
1977年 | 39篇 |
1976年 | 65篇 |
1975年 | 42篇 |
1974年 | 59篇 |
1973年 | 58篇 |
1972年 | 46篇 |
1971年 | 55篇 |
1970年 | 36篇 |
1969年 | 34篇 |
1965年 | 28篇 |
排序方式: 共有3902条查询结果,搜索用时 750 毫秒
1.
A Rauch R A Pfeiffer G Leipold H Singer M Tigges M Hofbeck 《American journal of human genetics》1999,64(2):659-666
2.
3.
4.
The specificity of the syngeneic mixed leukocyte response, a primary anti-I region T cell proliferative response, is determined intrathymically 总被引:6,自引:0,他引:6
L H Glimcher R H Schwartz D L Longo A Singer 《Journal of immunology (Baltimore, Md. : 1950)》1982,129(3):987-991
In previous studies, the syngeneic MLR of peripheral T cells was shown to be predominantly an I region-restricted function. In this report we show that adult thymocytes are also capable of responding to syngeneic irradiated stimulator cells in a syngeneic MLR, provided that TCGF is added to the culture system. Using this assay, it was possible for the first time to examine the pattern of I region restriction within the thymus itself. Analysis of the thymocyte syngeneic MLR in thymuses from radiation-induced bone marrow chimeras demonstrated that the MHC preference seen in the peripheral T cell population also existed in cells resident within the thymus. Experiments utilizing congenitally athymic mice transplanted with allogeneic thymic grafts demonstrated that both peripheral T cells and thymocytes from such animals displayed a strong preferential proliferation toward stimulator cells bearing thymic-type MHC determinants. The results in the nude model thus demonstrate that the thymus by itself is sufficient to impart such restriction specificity on a developing T cell repertoire. These results are consistent with the notion that the thymus exerts selective pressure on maturing T cell populations that results in a skewing of the T cell repertoire toward the recognition of thymic-type I region products, and that this MHC preference exists before expansion of T cells in the periphery. 相似文献
5.
6.
Charles Romeo Naoko Moriwaki Kerry T. Yasunobu Irwin C. Gunsalus Hideo Koga 《Journal of Protein Chemistry》1987,6(3):253-261
The first 12 NH2-terminal amino acids of the Pseudomonas putida putidaredoxin reductase were shown to be Met-Asn-Ala-Asn-Asp-Asn-Val-Val-Ile-Val-Gly-Thr. Comparison of these data with the DNA sequence of the BamHI-HindIII 197-base fragment derived from the PstI 2.2-kb fragment obtained from the P. putida plasmid showed that the putidaredoxin reductase gene was downstream from the cytochrome P-450 gene and the intergenic region had the 24-nucleotide sequence TAAACACATGGGAGTGCGTGCTAA. The Shine-Dalgarno sequence GGAG was detected in this region. The initiating triplet for the reductase gene was GTG, which normally codes for valine, but in the initiating codon position codes for methionine. From the amino acid sequence and X-ray data comparisons with other flavoproteins, what appears to be the AMP binding region of the FAD can be recognized in the NH2-terminal portion of the reductase involving residues 5–35.This article was presented during the proceedings of the International Conference on Macromolecular Structure and Function, held at the National Defence Medical College, Tokorozawa, Japan, December 1985. 相似文献
7.
Eliot C. Bush Anne E. Clark Chris M. DeBoever Lillian E. Haynes Sidra Hussain Singer Ma Matthew M. McDermott Adam M. Novak John S. Wentworth 《PloS one》2012,7(11)
A significant proportion of enzymes display cooperativity in binding ligand molecules, and such effects have an important impact on metabolic regulation. This is easiest to understand in the case of positive cooperativity. Sharp responses to changes in metabolite concentrations can allow organisms to better respond to environmental changes and maintain metabolic homeostasis. However, despite the fact that negative cooperativity is almost as common as positive, it has been harder to imagine what advantages it provides. Here we use computational models to explore the utility of negative cooperativity in one particular context: that of an inhibitor binding to an enzyme. We identify several factors which may contribute, and show that acting together they can make negative cooperativity advantageous. 相似文献
8.
Marian Irwin 《The Journal of general physiology》1922,5(2):223-224
1. An accurate quantitative method of measuring the penetration of dye into the living cell is described. 2. Cresyl blue is unable to penetrate rapidly unless the pH outside the cell is decidedly greater than that inside. The rate of penetration increases with increasing pH. 3. Around pH 9 penetration of the dye is rapid while the reverse is true of exosmosis. At low pH values (5.9) exosmosis is rapid and penetration is very slow. 相似文献
9.
Summary Aluminum extraction from two aluminum-rich fly-ashes by commercial and microbiologically-produced citric acids was tested. Up to 12% Al2O3 of the total was extracted by a 21 hrs1 shaking treatment at 60° C. Extraction efficiency is considerably affected by extracting acid concentration and extraction temperature. The extraction efficiency of microbiologically-produced citric acids was only slightly lower than that of commercial citric acid of equal molarity. 相似文献
10.
N Shamala L W Lim F S Mathews W McIntire T P Singer D J Hopper 《Journal of molecular biology》1985,183(3):517-518
Single crystals of p-cresol methylhydroxylase, a flavocytochrome c from Pseudomonas putida, have been prepared. The crystals are orthorhombic, space group P212121 with unit cell parameters; a = 140.3 A, b = 130.6 A and c = 74.1 A. They contain a single non-symmetric dimer per asymmetric unit and diffract to at least 2.5 A resolution. 相似文献