全文获取类型
收费全文 | 345篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
系统科学 | 5篇 |
理论与方法论 | 2篇 |
现状及发展 | 49篇 |
研究方法 | 37篇 |
综合类 | 241篇 |
自然研究 | 12篇 |
出版年
2019年 | 2篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2013年 | 1篇 |
2012年 | 16篇 |
2011年 | 24篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 11篇 |
2007年 | 20篇 |
2006年 | 13篇 |
2005年 | 14篇 |
2004年 | 10篇 |
2003年 | 4篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 13篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 9篇 |
1976年 | 3篇 |
1975年 | 6篇 |
1974年 | 10篇 |
1973年 | 5篇 |
1972年 | 7篇 |
1971年 | 11篇 |
1970年 | 7篇 |
1969年 | 3篇 |
1968年 | 9篇 |
1967年 | 8篇 |
1966年 | 4篇 |
1965年 | 6篇 |
排序方式: 共有346条查询结果,搜索用时 31 毫秒
71.
It is important that migration is measured accurately, for example to inform population estimates and projections. However, current sources of information present challenges in producing robust estimates of emigration from Great Britain. This article reports on work carried out by the Office for National Statistics to investigate the potential for using administrative data sources to contribute to the measurement of emigration. 相似文献
72.
Association scan of 14,500 nonsynonymous SNPs in four diseases identifies autoimmunity variants 总被引:2,自引:0,他引:2
Wellcome Trust Case Control Consortium;Australo-Anglo-American Spondylitis Consortium 《Nature genetics》2007,39(11):1329-1337
We have genotyped 14,436 nonsynonymous SNPs (nsSNPs) and 897 major histocompatibility complex (MHC) tag SNPs from 1,000 independent cases of ankylosing spondylitis (AS), autoimmune thyroid disease (AITD), multiple sclerosis (MS) and breast cancer (BC). Comparing these data against a common control dataset derived from 1,500 randomly selected healthy British individuals, we report initial association and independent replication in a North American sample of two new loci related to ankylosing spondylitis, ARTS1 and IL23R, and confirmation of the previously reported association of AITD with TSHR and FCRL3. These findings, enabled in part by increased statistical power resulting from the expansion of the control reference group to include individuals from the other disease groups, highlight notable new possibilities for autoimmune regulation and suggest that IL23R may be a common susceptibility factor for the major 'seronegative' diseases. 相似文献
73.
Two novel prenylated flavones, termed Cannflavin A and B, were isolated from the cannabinoid free ethanolic extract of Cannabis sativa L. Both compounds inhibited prostaglandin E2 production by human rheumatoid synovial cells in culture. 相似文献
74.
75.
Increased neurovirulence associated with a single nucleotide change in a noncoding region of the Sabin type 3 poliovaccine genome 总被引:11,自引:0,他引:11
D M Evans G Dunn P D Minor G C Schild A J Cann G Stanway J W Almond K Currey J V Maizel 《Nature》1985,314(6011):548-550
Most of the small number of cases of poliomyelitis which occur in countries where Sabin's attenuated poliovirus vaccines are used are temporally associated with administration of vaccine and involve polioviruses of types 2 and 3 (ref. 1). Recent studies have provided convincing evidence that the Sabin type 2 and 3 viruses themselves may revert to a neurovirulent phenotype on passage in man. We report here that a point mutation in the 5' noncoding region of the genome of the poliovirus type 3 vaccine consistently reverts to wild type in strains isolated from cases of vaccine-associated poliomyelitis. Virus with this change is rapidly selected on passage through the human gastrointestinal tract. The change is associated with a demonstrable increase in the neurovirulence of the virus. 相似文献
76.
Nuclear receptor that identifies a novel retinoic acid response pathway 总被引:147,自引:0,他引:147
77.
D. J. Evans 《武汉大学学报:自然科学英文版》1996,1(3-4):292-308
Parallel algorithms have been designed for the past 20 years initially by parallelising existing sequential algorithms for many different parallel architectures. More recently parallel strategies have been identified and utilised resulting in many new parallel algorithms. However the analysis of such algorithms reveals that further strategies can be applied to increase the parallelism. One of these, i.e., increasing the computational capacity in each processing node can reduce the congestion/communication for shared memory/distributed memory multiprocessor systems and dramatically improve the performance of the algorithm. Two algorithms are identified and studied, i.e., the cyclic reduction method for solving large tridiagonal linear systems in which the odd/even sequence is increased to a ‘stride of 3’ or more resulting in an improved algorithm. Similarly the Gaussian Elimination method for solving linear systems in which one element is eliminated at a time can be adapted to parallel form in which two elements are simultaneously eliminated resulting in the Parallel Implicit Elimination (P.I.E.) method. Numerical results are presented to support the analyses. 相似文献
78.
A view of manufacturing processes is presented in which five distinct categories are defined as casting, deformation, machining, joining, and solid freeforming. Solid freeforming is essentially biomimetic and shares problems of morphogenesis with natural processes. Our team in University of London has been exploring three mechanisms of solid freeforming. In dry powder deposition and direct ink-jet printing, the emphasis has turned to the problem of delivering a complex shape in which the three dimensional spatial arrangement of composition is delivered from the design file. In extrusion freeforming, the aim is to control microstructure at hierarchical levels also from the design file. The quest for 3-D functional gradients is satisfied by acoustic and ultrasonic dispensing and mixing of powders so that each layer can be patterned. These methods could be extended to deliver the complex patterns demanded by left-handed microwave metamaterials. Dry powder deposition and direct ink-jet printing are turning towards combinatorial methods in which multiple sample libraries are used to accelerate discovery. In turn, this paves the way for ‘autonomous research machines’ which steer their own search refinements in response to our requests for new materials. In this way, solid freeforming used for sample preparation can give an ‘arm’ to an intelligent machine so that it can conduct its own experimentation and learning; an idea that originated with Alan Turing in the late 1940s. 相似文献
79.
80.
Characterization of the human cysteinyl leukotriene CysLT1 receptor. 总被引:29,自引:0,他引:29
K R Lynch G P O'Neill Q Liu D S Im N Sawyer K M Metters N Coulombe M Abramovitz D J Figueroa Z Zeng B M Connolly C Bai C P Austin A Chateauneuf R Stocco G M Greig S Kargman S B Hooks E Hosfield D L Williams A W Ford-Hutchinson C T Caskey J F Evans 《Nature》1999,399(6738):789-793
The cysteinyl leukotrienes-leukotriene C4(LTC4), leukotriene D4(LTD4) and leukotriene E4(LTE4)-are important mediators of human bronchial asthma. Pharmacological studies have determined that cysteinyl leukotrienes activate at least two receptors, designated CysLT1 and CysLT2. The CysLT1-selective antagonists, such as montelukast (Singulair), zafirlukast (Accolate) and pranlukast (Onon), are important in the treatment of asthma. Previous biochemical characterization of CysLT1 antagonists and the CysLT1 receptor has been in membrane preparations from tissues enriched for this receptor. Here we report the molecular and pharmacological characterization of the cloned human CysLT1 receptor. We describe the functional activation (calcium mobilization) of this receptor by LTD4 and LTC4, and competition for radiolabelled LTD4 binding to this receptor by the cysteinyl leukotrienes and three structurally distinct classes of CysLT1-receptor antagonists. We detected CysLT1-receptor messenger RNA in spleen, peripheral blood leukocytes and lung. In normal human lung, expression of the CysLT1-receptor mRNA was confined to smooth muscle cells and tissue macrophages. Finally, we mapped the human CysLT1-receptor gene to the X chromosome. 相似文献