全文获取类型
收费全文 | 162篇 |
免费 | 0篇 |
专业分类
系统科学 | 1篇 |
理论与方法论 | 1篇 |
现状及发展 | 40篇 |
研究方法 | 28篇 |
综合类 | 91篇 |
自然研究 | 1篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2012年 | 7篇 |
2011年 | 8篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 9篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 10篇 |
2002年 | 3篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 11篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 4篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 7篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 6篇 |
1966年 | 4篇 |
1965年 | 1篇 |
1961年 | 1篇 |
1947年 | 1篇 |
排序方式: 共有162条查询结果,搜索用时 203 毫秒
21.
22.
A. Scriabine C. T. Ludden L. S. Watson J. M. Stavorski G. Morgan J. J. Baldwin 《Cellular and molecular life sciences : CMLS》1979,35(5):653-655
Summary 2 new 4-trifluoromethylimidazole derivatives were found which lowered mean arterial pressure in renal and spontaneously hypertensive (SH) rats by the oral route. In SH rats, compounds A and B were 0.1 and 0.3 times, respectively, as potent as hydralazine. No tolerance development was observed in SH rats with either compound over a 1-week period. In anesthetized dogs, both compounds lowered arterial pressure and peripheral vascular resistance but increased cardiac output. By intraarterial administration, both compounds increased femoral arterial blood flow. These findings represent discovery of a new class of vasodilator drugs.Deceased, May 31, 1978. 相似文献
23.
24.
25.
Newlin T. Morgan William J. Vaughn Wayne S. Rasband Thomas A. Wehr Anna Wirz-Justice 《Cellular and molecular life sciences : CMLS》1982,38(11):1296-1301
Summary A computer-based system for collection and analysis of circadian rest-activity data was developed. The system has the advantage of a minimal amount of interface hardware and uses standard laboratory computer equipment permitting easy collection and automatic visualization and analysis of the data. The flexibility of the programs allows manipulation of the presentation format as needed and further refinements of the data analyses are possible. 相似文献
26.
Antagonistic coevolution between hosts and parasites in spatially structured populations can result in local adaptation of parasites; that is, the greater infectivity of local parasites than foreign parasites on local hosts. Such parasite specialization on local hosts has implications for human health and agriculture. By contrast with classic single-species population-genetic models, theory indicates that parasite migration between subpopulations might increase parasite local adaptation, as long as migration does not completely homogenize populations. To test this hypothesis we developed a system-specific mathematical model and then coevolved replicate populations of the bacterium Pseudomonas fluorescens and a parasitic bacteriophage with parasite only, with host only or with no migration. Here we show that patterns of local adaptation have considerable temporal and spatial variation and that, in the absence of migration, parasites tend to be locally maladapted. However, in accord with our model, parasite migration results in parasite local adaptation, but host migration alone has no significant effect. 相似文献
27.
Alphabeta T lymphocytes are able to detect even a single peptide-major histocompatibility complex (MHC) on the surface of an antigen-presenting cell. This is despite clear evidence, at least with CD4+ T cells, that monomeric ligands are not stimulatory. In an effort to understand how this remarkable sensitivity is achieved, we constructed soluble peptide-MHC heterodimers in which one peptide is an agonist and the other is one of the large number of endogenous peptide-MHCs displayed by presenting cells. We found that some specific combinations of these heterodimers can stimulate specific T cells in a CD4-dependent manner. This activation is severely impaired if the CD4-binding site on the agonist ligand is ablated, but the same mutation on an endogenous ligand has no effect. These data correlate well with analyses of lipid bilayers and cells presenting these ligands, and indicate that the basic unit of helper T cell activation is a heterodimer of agonist peptide- and endogenous peptide-MHC complexes, stabilized by CD4. 相似文献
28.
Two new beta-adrenoceptor blocking drugs with acute antihypertensive and positive inotropic effects are described: Compound A (2-[4-(3-tert.butylamino-2-hydroxypropoxy)phenyl]-4-trifluoromethylimidazole) and MK-761 (2-(3-tert.butylamine-2-hydroxypropoxy)-3-cyanopyridine hydrochloride). In SH rats both compounds, given orally, lowered arterial pressure and were more potent than hydralazine. The antihypertensive effect of compound A but not of MK-761 was antagonized by timolol. Both compounds had positive inotropic activity on cat heart papillary muscles; these effects were antagonized by timolol. The pretreatment of animals with reserpine greatly reduced the positive inotropic effect of MK-761 but not of compound A. The acute antihypertensive and positive inotropic effects of compound A are like to be at least partially due to stimulation of beta-adrenoceptors, e.g. intrinsic sympathomimetic activity. The effects of MK-761 on the same parameters appear to be mediated by different mechanisms. 相似文献
29.
S Neph J Vierstra AB Stergachis AP Reynolds E Haugen B Vernot RE Thurman S John R Sandstrom AK Johnson MT Maurano R Humbert E Rynes H Wang S Vong K Lee D Bates M Diegel V Roach D Dunn J Neri A Schafer RS Hansen T Kutyavin E Giste M Weaver T Canfield P Sabo M Zhang G Balasundaram R Byron MJ MacCoss JM Akey MA Bender M Groudine R Kaul JA Stamatoyannopoulos 《Nature》2012,489(7414):83-90
30.
This paper provides an account of the ‘use-value’ of case-based research by showing how social scientists exploit cases, and case studies, in a variety of practices of inference and extension. The critical basis for making such extensions relies on the power of a case, or the account given of a case (the case-study account), to exemplify certain features of the social world in ways which prove valuable for further analysis: either of the same case, or in many domains beyond the original case study. Framing use-values in terms of exemplification compares favourably with understanding reasoning beyond the case either as a form of analogical reasoning or in taking cases as experimentable objects. 相似文献