全文获取类型
收费全文 | 547篇 |
免费 | 48篇 |
国内免费 | 9篇 |
专业分类
604篇 |
出版年
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 9篇 |
2018年 | 5篇 |
2017年 | 8篇 |
2016年 | 6篇 |
2015年 | 14篇 |
2014年 | 12篇 |
2013年 | 18篇 |
2012年 | 19篇 |
2011年 | 20篇 |
2010年 | 15篇 |
2009年 | 20篇 |
2008年 | 27篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 11篇 |
2004年 | 12篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 15篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1989年 | 6篇 |
1983年 | 4篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1971年 | 3篇 |
1959年 | 7篇 |
1958年 | 23篇 |
1957年 | 26篇 |
1956年 | 26篇 |
1955年 | 22篇 |
1954年 | 22篇 |
1953年 | 13篇 |
1952年 | 13篇 |
1951年 | 10篇 |
1950年 | 9篇 |
排序方式: 共有604条查询结果,搜索用时 0 毫秒
81.
82.
83.
Jan AM van Laar Jasper H Kappen Paul LA van Daele P Martin van Hagen 《Arthritis research & therapy》2009,11(2):109-3
Behçet's disease is a complex vasculitis of unknown etiology. Abundant neutrophils suggest the involvement of innate immunity. Cytokines are skewed to the T-helper-1 pattern. Few sterile organs are easily accessible for analysis in Behçet's disease. Cañete and coworkers identify inflamed joints as a feasible model and suggest the involvement of innate immunity in Behçet's disease. 相似文献
84.
MANUEL DE LA ESTRELLA CARLOS AEDO MAURICIO VELAYOS 《Botanical journal of the Linnean Society. Linnean Society of London》2009,159(2):268-279
A multivariate morphometric study of Daniellia, an endemic genus of tropical and subtropical Africa, indicates that nine species may be recognized: D. alsteeniana, D. klainei, D. oblonga, D. ogea, D. oliveri, D. pilosa, D. pynaertii, D. soyauxii and D. thurifera. In our study we found that some characters, not previously studied in detail, were significant in species delimitation: petiole indumentum, petiole width, number and position of glands on the lower surface of the leaflets and presence or absence of glands at the insertion of each pair of leaflets. The rare and scattered material of D. pilosa and D. soyauxii made their classification uncertain, although some qualitative characters support their differentiation. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 268–279. 相似文献
85.
86.
The effects of an auxin herbicide, 2,4-D, at a concentration of 0.01 mM, on the K+ uptake and efflux of excised roots of wheat (Triticum aestivum L. cv. Rannaya) were investigated at different pH values. The K+ movement was monitored with a K+ (86Rb) tracer. In parallel experiments the ATPase activities of microsomal fractions were determined by the inorganic phosphate liberation method. 2,4-D inhibited the K+ uptake especially at low pH, irrespective of whether Ca2+ was present or not. No marked changes were observed in the K+ efflux properties at pH values above 4. The inhibitory effect on K+ uptake exhibited a correlation with the hydrocarbon solubility of the herbicide, but not with the 2,4-D-induced decrease of the ATPase activity. It is suggested that 2,4-D exerts a non-specific effect on the lipid-protein interactions, giving rise to a generalized alteration of the transport barrier properties of the plasma membrane even at as low a concentration as 0.01 mM. 相似文献
87.
Influence of food availability on demography and local population dynamics in a long-lived seabird 总被引:2,自引:0,他引:2
Oro D Cam E Pradel R Martínez-Abraín A 《Proceedings. Biological sciences / The Royal Society》2004,271(1537):387-396
Few studies have addressed the effects of food availability as a proximate factor affecting local adult survival in long-lived organisms and their consequences at local population dynamics. We used capture-recapture analysis of resightings of 10 birth cohorts of ringed Audouin's gulls, Larus audouinii, to estimate adult survival and dispersal (both emigration and immigration). For the first time, permanent emigration (the transient effect in capture-recapture analysis) was modelled for the whole population and not only for the newly marked birds. Gulls exploit to a large extent fishes discarded from trawlers, and a trawling moratorium established since 1991 has decreased food supply for the colony. This was used as a natural experiment of food availability to assess its effects on adult survival and emigration. These and other demographic parameters were used in a projection modelling to assess the probabilities of extinction of the colony under two scenarios of lower and higher food availability. Food availability (together with the age of individuals) influenced emigration probabilities, but not adult survival, which was estimated at 0.91 (s.e. = 0.02). When food was in shorter supply during the chick-rearing period, emigration was very high (ca. 65%) for younger breeders, although this rate decreased sharply with age. Probabilities of extinction were very high when food availability was low, and when environmental stochasticity was introduced, and only stochastic immigration from the outside seemed to prevent extinction. The results highlight the importance of dispersal processes in the population dynamics of long-lived organisms. 相似文献
88.
89.
90.
Maximilian Tischer Ludmilla Sologub Gabriele Pradel Ulrike Holzgrabe 《Bioorganic & medicinal chemistry》2010,18(9):2998-3003
The bisquaternary bisnaphthalimides are a versatile class of compounds being active against the malaria parasite Plasmodium falciparum in the lower nanomolar range of concentration combined with no cytotoxicity. The series of compounds is designed as choline analogues and interfering agents of the phosphatidylcholine biosynthesis. The qualitative analysis of the structure–activity relationships (SAR) revealed the importance of a long methylene middle chain of at least 8 methylene groups between the two bisquaternary naphthalimides or a monoquaternary naphthalimide consisting of a long alkyl chain attached to the positively charged nitrogen atom. Since the SARs are different from reported biscationic antimalarial drugs the mode of action remains to be elucidated. 相似文献