全文获取类型
收费全文 | 7704篇 |
免费 | 78篇 |
国内免费 | 54篇 |
专业分类
系统科学 | 41篇 |
丛书文集 | 90篇 |
教育与普及 | 13篇 |
理论与方法论 | 17篇 |
现状及发展 | 3359篇 |
研究方法 | 411篇 |
综合类 | 3822篇 |
自然研究 | 83篇 |
出版年
2016年 | 49篇 |
2012年 | 106篇 |
2011年 | 206篇 |
2010年 | 57篇 |
2009年 | 53篇 |
2008年 | 153篇 |
2007年 | 180篇 |
2006年 | 134篇 |
2005年 | 139篇 |
2004年 | 240篇 |
2003年 | 125篇 |
2002年 | 133篇 |
2001年 | 296篇 |
2000年 | 294篇 |
1999年 | 214篇 |
1992年 | 118篇 |
1991年 | 123篇 |
1990年 | 106篇 |
1989年 | 99篇 |
1988年 | 106篇 |
1987年 | 120篇 |
1986年 | 114篇 |
1985年 | 158篇 |
1984年 | 121篇 |
1983年 | 98篇 |
1982年 | 84篇 |
1981年 | 116篇 |
1980年 | 109篇 |
1979年 | 251篇 |
1978年 | 198篇 |
1977年 | 183篇 |
1976年 | 137篇 |
1975年 | 160篇 |
1974年 | 210篇 |
1973年 | 173篇 |
1972年 | 193篇 |
1971年 | 212篇 |
1970年 | 274篇 |
1969年 | 209篇 |
1968年 | 188篇 |
1967年 | 211篇 |
1966年 | 181篇 |
1965年 | 144篇 |
1959年 | 53篇 |
1958年 | 104篇 |
1957年 | 76篇 |
1956年 | 73篇 |
1955年 | 52篇 |
1954年 | 75篇 |
1948年 | 49篇 |
排序方式: 共有7836条查询结果,搜索用时 15 毫秒
981.
982.
983.
984.
985.
Drosophila Toll and IL-1 receptor. 总被引:21,自引:0,他引:21
986.
987.
988.
T N Schumacher M L De Bruijn L N Vernie W M Kast C J Melief J J Neefjes H L Ploegh 《Nature》1991,350(6320):703-706
Synthetic peptides have been used to sensitize target cells and thereby screen for epitopes recognized by T cells. Most epitopes of cytotoxic T lymphocytes can be mimicked by synthetic peptides of 12-15 amino acids. Although in specific cases, truncations of peptides improves sensitization of target cells, no optimum length for binding to major histocompatibility complex (MHC) class I molecules has been defined. We have now analysed synthetic peptide captured by empty MHC class I molecules of the mutant cell line RMA-S. We found that class I molecules preferentially bound short peptides (nine amino acids) and selectively bound these peptides even when they were a minor component in a mixture of longer peptides. These results may help to explain the difference in size restriction of T-cell epitopes between experiments with synthetic peptides and those with naturally processed peptides. 相似文献
989.
N S Latman 《Experientia》1987,43(1):32-38
There appears to be ample evidence to conclude that various meteorological factors do exert a significant impact on some people with various rheumatic diseases. The data is, however, crude relative to our general understanding. Most of this research on RA has dealt with the primary signs and symptoms of inflammation. We know, however, many of the chemical mediators of inflammation. It seems like a logical progression of research to determine the effects of the meteorological/atmospheric factors of concern on these specific intrinsic mediators of inflammation. In general, gout can be very well controlled through medication. The evidence suggests, however, that we may gain a much better understanding of how atmospheric factors such as temperature can effect the body through changes in its physico-chemical processes by using Gout as a model. The work with SLE has already yielded useful applications. Sun screening pharmaceuticals have been quite successful in reducing exacerbations of symptoms. But we don't know why only some people are photosensitive. The previous research on the effects of atmospheric factors on the rheumatic diseases has illustrated key issues in methodology: large sample sizes are critical, objective and quantifiable disease variables are important, the variables measured must be specific to the questions investigated, the diseases investigated must be as specifically and accurately defined as possible, and the various aspects of 'weather' to be investigated must be specifically defined and quantified. It is apparent that there is much more important and useful work to be performed before we can understand the effects of atmospheric factors on the rheumatic diseases. 相似文献
990.
Crude, partially purified and purified fractions of pigeon milk injected subcutaneously in newborn mice brought about precocious opening of eyelids by 2–3 days and eruption of incisors by 3–4 days. The biological activity of pigeon milk-derived growth factor (PMGF) compared well with that of mouse epidermal growth factor (mEGF). 相似文献