全文获取类型
收费全文 | 1897篇 |
免费 | 159篇 |
出版年
2015年 | 40篇 |
2014年 | 54篇 |
2013年 | 59篇 |
2012年 | 67篇 |
2011年 | 52篇 |
2010年 | 65篇 |
2009年 | 46篇 |
2008年 | 69篇 |
2007年 | 88篇 |
2006年 | 48篇 |
2005年 | 61篇 |
2004年 | 48篇 |
2003年 | 40篇 |
2002年 | 41篇 |
2001年 | 28篇 |
2000年 | 23篇 |
1999年 | 34篇 |
1998年 | 31篇 |
1997年 | 25篇 |
1996年 | 25篇 |
1994年 | 27篇 |
1993年 | 28篇 |
1992年 | 30篇 |
1991年 | 32篇 |
1990年 | 26篇 |
1989年 | 30篇 |
1988年 | 40篇 |
1987年 | 33篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 23篇 |
1980年 | 20篇 |
1979年 | 25篇 |
1976年 | 20篇 |
1974年 | 26篇 |
1973年 | 26篇 |
1972年 | 23篇 |
1971年 | 21篇 |
1969年 | 19篇 |
1968年 | 23篇 |
1965年 | 41篇 |
1964年 | 19篇 |
1963年 | 32篇 |
1962年 | 25篇 |
1961年 | 39篇 |
1960年 | 23篇 |
1959年 | 28篇 |
1958年 | 28篇 |
排序方式: 共有2056条查询结果,搜索用时 343 毫秒
51.
52.
53.
54.
55.
56.
57.
Postural effect on ventilatory control 总被引:1,自引:0,他引:1
58.
The site specificity of the apicomplexans Gregarina cuneata and Gregarina sleini , in larval Tenebrio molitor was investigated. Gregarina cuneata was found to inhabit the anteriormost region of the larval midgut, while G. steini was restricted to the posterior portion of the intestine. The site specificity of the pair was conserved in single and concurrent infections. Interspecific interactions do not seem to be presently responsible for the resource partitioning by the 2 gregarine species. Key words. Gregarina, site specificity, Tenebrio molitor. 相似文献
59.
A Karasik S S Reddy R B Pepinsky T Brock C R Kahn 《Journal of cellular physiology》1990,142(2):231-235
Epidermal growth factor (EGF) may either stimulate or inhibit cell growth. To elucidate the mechanism of these varied effects, we compared EGF action in parental A431 cells in which cell growth is inhibited, and clone 15, a mutant of these cells resistant to EGF growth inhibition. In both lines, EGF receptor was present in similar concentrations and underwent tyrosine phosphorylation to the same extent. Likewise, in both lines, acute exposure to EGF stimulated an increase in free cytoplasmic [Ca2+], as well as a similar increase in phosphorylation of lipocortin 1, a major substrate for the EGF receptor kinase whose phosphorylation is calcium-dependent. On the other hand, pretreatment of clone 15 cells with EGF for 72 h abolished EGF-induced phosphorylation of lipocortin 1 and led to a loss of the increase in cytoplasmic free [Ca2+], whereas no such desensitization was seen in the parental A431 cells. These data indicate a link between EGF-induced increase in cytoplasmic calcium, lipocortin phosphorylation, and cell growth and suggest that differences in mechanisms of desensitization to these immediate actions of EGF may lead to altered growth response to this hormone. 相似文献
60.
VESSEY J KEVIN; RAPER C DAVID JR; HENRY LESLIE TOLLEY 《Journal of experimental botany》1990,41(12):1579-1584
Net uptake of by non-nodulated soybean plants [Glycme max(L ) Merr cv Ransom] growing in flowing hydroponicculture was measured daily during a 63 d period of reproductivedevelopment between the first florally inductive photopenodand late seed growth Removal of from a replenished solution containing 10 mol m was determined by ion chromatography Uptake of continued throughout reproductive development The net uptakerate of cycled between maxima and minima with a periodicity of oscillation of 3 to 7 d during the floralstage and about 6 d during the fruiting stage. Coupled withincreasing concentrations of carbon and C:N ratios in tissues,the oscillations in net uptake rates of are evidence that the demand for carbohydrate by reproductiveorgans is contingent on the availability of nitrogen in theshoot pool rather than that the demand for nitrogen followsthe flux of carbohydrate into reproductive tissues. Key words: Nitrate uptake rate, carbon-nitrogen partitioning, Glycme max (L ) Merrill 相似文献