全文获取类型
收费全文 | 407篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 1篇 |
丛书文集 | 53篇 |
理论与方法论 | 1篇 |
现状及发展 | 69篇 |
研究方法 | 30篇 |
综合类 | 250篇 |
自然研究 | 5篇 |
出版年
2016年 | 2篇 |
2013年 | 2篇 |
2012年 | 17篇 |
2011年 | 13篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2008年 | 17篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 16篇 |
2004年 | 7篇 |
2003年 | 9篇 |
2002年 | 14篇 |
2001年 | 9篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1983年 | 4篇 |
1981年 | 1篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 7篇 |
1970年 | 11篇 |
1969年 | 10篇 |
1968年 | 3篇 |
1967年 | 13篇 |
1966年 | 8篇 |
1965年 | 5篇 |
1959年 | 16篇 |
1958年 | 31篇 |
1957年 | 22篇 |
1956年 | 11篇 |
1955年 | 15篇 |
1954年 | 23篇 |
1948年 | 7篇 |
1947年 | 3篇 |
排序方式: 共有409条查询结果,搜索用时 31 毫秒
1.
2.
3.
德力 《内蒙古大学学报(自然科学版)》2004,35(3):260-261
Sauer引理是统计学习理论中的基本结论.在许多实际问题中,需要研究N类模式识别问题.本文将Sauer引理推广到N类分类问题. 相似文献
4.
5.
J A Martignetti A A Aqeel W A Sewairi C E Boumah M Kambouris S A Mayouf K V Sheth W A Eid O Dowling J Harris M J Glucksman S Bahabri B F Meyer R J Desnick 《Nature genetics》2001,28(3):261-265
The inherited osteolyses or 'vanishing bone' syndromes are a group of rare disorders of unknown etiology characterized by destruction and resorption of affected bones. The multicentric osteolyses are notable for interphalangeal joint erosions that mimic severe juvenile rheumatoid arthritis (OMIMs 166300, 259600, 259610 and 277950). We recently described an autosomal recessive form of multicentric osteolysis with carpal and tarsal resorption, crippling arthritic changes, marked osteoporosis, palmar and plantar subcutaneous nodules and distinctive facies in a number of consanguineous Saudi Arabian families. We localized the disease gene to 16q12-21 by using members of these families for a genome-wide search for homozygous-by-descent microsatellite markers. Haplotype analysis narrowed the critical region to a 1.2-cM region that spans the gene encoding MMP-2 (gelatinase A, collagenase type IV; (ref. 3). We detected no MMP2 enzymatic activity in the serum or fibroblasts of affected family members. We identified two family-specific homoallelic MMP2 mutations: R101H and Y244X. The nonsense mutation effects a deletion of the substrate-binding and catalytic sites and the fibronectin type II-like and hemopexin/TIMP2 binding domains. Based on molecular modeling, the missense mutation disrupts hydrogen bond formation within the highly conserved prodomain adjacent to the catalytic zinc ion. 相似文献
6.
Summary Following engorgement, female ixodid ticks secrete a tick salivary gland degeneration factor (TSGDF) into the hemolymph. Here we show that the arthropod ecdysteroid hormones, ecdysome and 20-hydroxyecdysone, induce degeneration of tick salivary glands maintained in organ culture. The effective dose range in vitro is 30–300 ng/ml, a range reported to be physiological for this species following repletion. In addition, infusion of 20-hydroxyecdysome in vivo induces salivary gland degeneration. We therefore propose that TSGDF may be an ecdysteroid.Acknowledgments. Some of the data reported here were presented to the annual meeting of the Canadian Society of Zoologists, 15–18 May 1983; Program of abstracts, page 53. Financial support of the Canadian National Sportsmen's Fund and NSERC Canada to W.R.K. is gratefully acknowledged. 相似文献
7.
Genetics of the alkaline phosphatase polymorphism of the human placenta 总被引:27,自引:0,他引:27
8.
Summary The concentrations of testosterone (T) and 5-dihydrotestosterone were measured in fluid collected from the rete testis of immature and adult rats. The results indicate that adult levels of T are attained in the seminiferous tubules much earlier than in the peripheral circulation.This work was performed at the Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts, USA and supported by the National Institutes of Health through grants HD12641 and HD12642. We thank Dr B.V. Caldwell for antiserum to testosterone. 相似文献
9.
M. D. Adams J. T. Earnhardt B. R. Martin L. S. Harris W. L. Dewey R. K. Razdan 《Cellular and molecular life sciences : CMLS》1977,33(9):1204-1205
Summary Abnormal-8-tetrahydrocannabidiol (ABN-8-THC) failed to elicit central nervous system and cardiovascular effects in laboratory animals. Abnormal-cannabidiol (ABN-CBD) was also devoid of overt behavioral effects but produced marked hypotension with only slight bradycardia in anesthesized dogs.Acknowledgment. This work was supported by NIDA (grant No. DA-00574-01 and DA-00490) and Virginia Heart Society (grant No. RR-05697) 相似文献
10.
乙醇三维内微肋热管的传热性能 总被引:4,自引:0,他引:4
采用实验研究的方法对三维内微肋热管的强化传热特性进行研究,首次报道了以乙醇为工质的三维内微肋热管的传热性能。在实验范围内,与光管相比,竖直放置时,沸腾换热系数可以提高98%—190%,凝结换热系数可以提高76%—178%。三维内微肋结构能够同时明显地强化热管的沸腾换热与凝结换热,可以有效地减小热管的内热阻。 相似文献