全文获取类型
收费全文 | 771206篇 |
免费 | 90765篇 |
国内免费 | 570篇 |
专业分类
862541篇 |
出版年
2016年 | 8391篇 |
2015年 | 12482篇 |
2014年 | 14262篇 |
2013年 | 20313篇 |
2012年 | 22963篇 |
2011年 | 23133篇 |
2010年 | 15349篇 |
2009年 | 14349篇 |
2008年 | 20375篇 |
2007年 | 21176篇 |
2006年 | 19558篇 |
2005年 | 19167篇 |
2004年 | 18857篇 |
2003年 | 18015篇 |
2002年 | 17528篇 |
2001年 | 34941篇 |
2000年 | 35647篇 |
1999年 | 28469篇 |
1998年 | 10132篇 |
1997年 | 10473篇 |
1996年 | 10020篇 |
1995年 | 9286篇 |
1994年 | 9263篇 |
1993年 | 9131篇 |
1992年 | 22928篇 |
1991年 | 22059篇 |
1990年 | 21531篇 |
1989年 | 21043篇 |
1988年 | 19326篇 |
1987年 | 18593篇 |
1986年 | 17427篇 |
1985年 | 17283篇 |
1984年 | 14495篇 |
1983年 | 12524篇 |
1982年 | 9963篇 |
1981年 | 9100篇 |
1980年 | 8395篇 |
1979年 | 14037篇 |
1978年 | 11064篇 |
1977年 | 10175篇 |
1976年 | 9528篇 |
1975年 | 10442篇 |
1974年 | 11408篇 |
1973年 | 11224篇 |
1972年 | 10318篇 |
1971年 | 9455篇 |
1970年 | 8071篇 |
1969年 | 7947篇 |
1968年 | 7166篇 |
1967年 | 6169篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
912.
913.
W. H. Inman 《BMJ (Clinical research ed.)》1994,309(6954):608-609
914.
915.
916.
917.
Background
Evolution of parasite traits is inextricably linked to their hosts. For instance one common definition of parasite virulence is the reduction in host fitness due to infection. Thus, traits of infection must be viewed in both protagonists and may be under shared genetic and physiological control. We investigated these questions on the oomycete Hyaloperonospora arabidopsis (= parasitica), a natural pathogen of the Brassicaceae Arabidopsis thaliana. 相似文献918.
Expanded thermal niche for a diving vertebrate: A leatherback turtle diving into near-freezing water
Michael C. James Graeme C. Hays 《Journal of experimental marine biology and ecology》2006,335(2):221-226
The global distribution of extant reptiles is more limited than that of mammals or birds, with low reptilian species diversity at high latitudes. Central to this limited geographical distribution is the ectothermic nature of reptiles, which means that they generally become torpid at cold temperatures. However, here we report the first detailed telemetry from a leatherback turtle (Dermochelys coriacea) diving in cold water at high latitude. An individual equipped with a satellite tag that relayed temperature-depth profiles dived continuously for many weeks into sub-surface waters as cold as 0.4 °C. Global warming will likely increase the foraging range of leatherback turtles further into temperate and boreal waters. 相似文献
919.
Thirteen model alpha-ketocarboxylic acids and alpha-dicarbonyl compounds have been observed to be reduced by titanium(III) chloride. The products of these reactions were shown by melting (boiling) points, mixed melting points, derivatives, refractive indices, infrared, and NMR comparisons with authentic compounds or literature information to be the corresponding alpha-hydroxycarboxylic acids or alpha-hydroxyketones. 相似文献
920.
U H Lewinski G M Mavligit P M Epstein E M Hersh R A Ortez W J Thompson 《Biomedicine / [publiée pour l'A.A.I.C.I.G.]》1980,33(7):217-219
Endogenous cyclic adenosine and guanosine monophosphate (cAMP, cGMP) levels were studied in human peripheral blood lymphocytes during mixed leukocyte reactions (MLR). cAMP level was consistently elevated in one-way MLR, with good correlation to 3H-thymidine uptake in these reactions. In contrast, cGMP level was practically unchanged. Irradiation of reacting cell populations resulted in inhibition of cyclic nucleotide phosphodiesterase (PDE) activity. These results suggest that metabolic alterations in cAMP may be associated with immune reactions of cellular recognition. 相似文献