全文获取类型
收费全文 | 437篇 |
免费 | 7篇 |
专业分类
444篇 |
出版年
2020年 | 5篇 |
2018年 | 11篇 |
2017年 | 14篇 |
2016年 | 10篇 |
2014年 | 12篇 |
2013年 | 22篇 |
2012年 | 25篇 |
2011年 | 22篇 |
2010年 | 9篇 |
2009年 | 14篇 |
2008年 | 24篇 |
2007年 | 18篇 |
2006年 | 18篇 |
2005年 | 13篇 |
2004年 | 10篇 |
2003年 | 17篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1996年 | 2篇 |
1993年 | 2篇 |
1992年 | 13篇 |
1991年 | 14篇 |
1990年 | 7篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 5篇 |
1972年 | 7篇 |
1971年 | 7篇 |
1970年 | 4篇 |
1969年 | 3篇 |
1968年 | 4篇 |
1967年 | 3篇 |
1965年 | 2篇 |
排序方式: 共有444条查询结果,搜索用时 15 毫秒
41.
Fossøy F Moksnes A Røskaft E Antonov A Dyrcz A Moskat C Ranke PS Rutila J Vikan JR Stokke BG 《PloS one》2012,7(5):e36884
Sex allocation theory and empirical evidence both suggest that natural selection should favour maternal control of offspring sex ratio in relation to their ability to invest in the offspring. Generalist parasites constitute a particularly interesting group to test this theory as different females commonly utilize different host species showing large variation in provisioning ability. The common cuckoo (Cuculus canorus) is a generalist brood parasite that lays its eggs in the nest of many different passerine birds, but each female tends to specialize on one particular host species giving rise to highly specialized host races. The different host species show large variation in their ability to invest in the parasitic offspring, presenting an opportunity for female cuckoos to bias offspring sex ratio in relation to host species quality. Here, we investigate host-race specific sex allocation controlling for maternal identity in the common cuckoo. We found no evidence of any significant relationship between host race and sex ratio in one sympatric population harbouring three different host races, or in a total of five geographically separated populations. There was also no significant association between host quality, as determined by species-specific female host body mass, and cuckoo sex ratio. Finally, we found no significant relationship between individual cuckoo maternal quality, as determined by her egg volume, and sex ratio within each host race. We conclude that the generalist brood-parasitic common cuckoo show no significant sex-ratio bias in relation to host race and discuss this finding in light of gene flow and host adaptations. 相似文献
42.
Structural determinants for ligand binding and catalysis of triosephosphate isomerase. 总被引:1,自引:0,他引:1
I Kursula S Partanen A M Lambeir D M Antonov K Augustyns R K Wierenga 《European journal of biochemistry》2001,268(19):5189-5196
The crystal structure of leishmania triosephosphate isomerase (TIM) complexed with 2-(N-formyl-N-hydroxy)-aminoethyl phosphonate (IPP) highlights the importance of Asn11 for binding and catalysis. IPP is an analogue of the substrate D-glyceraldehyde-3-phosphate, and it is observed to bind with its aldehyde oxygen in an oxyanion hole formed by ND2 of Asn11 and NE2 of His95. Comparison of the mode of binding of IPP and the transition state analogue phosphoglycolohydroxamate (PGH) suggests that the Glu167 side chain, as well as the triose part of the substrate, adopt different conformations as the catalysed reaction proceeds. Comparison of the TIM-IPP and the TIM-PGH structures with other liganded and unliganded structures also highlights the conformational flexibility of the ligand and the active site, as well as the conserved mode of ligand binding. 相似文献
43.
A. S. Antonov 《Russian Journal of Genetics》2002,38(6):622-627
A survey of publications dealing with comparative analysis of genomes shows that modern genomics has naturally evolved from gene systematics—an area whose formation and development was substantially influenced by the scientific school of A.N. Belozersky. 相似文献
44.
The excitation of oscillations in a discharge with negative differential conductivity is studied experimentally. The possibility is demonstrated of amplifying oscillations in the cathode dark space at frequencies close to the electron plasma frequency of the positive-column plasma. The phase velocities of waves at these frequencies are determined. When the waves pass from the cathode dark space to the discharge positive column, their phase velocities decrease; the closer the frequency is to the electron plasma frequency, the more pronounced the decrease in the phase velocity. As the intensity of oscillations increases, the discharge becomes non-steady-state. This is confirmed by the time evolution of the current-voltage characteristic. The shape of the current-voltage characteristic, its splitting, and the rate at which it varies depend on the input RF power. The decrease in the cathode dark space indicates that the ionization processes in the discharge are strongly influenced by electron plasma oscillations excited due to the collective interaction of the electron beam formed at the cathode with the discharge plasma. It is these processes that determine the maximum values of both the frequency of the excited oscillations and the power that can be withdrawn from the discharge. 相似文献
45.
Detergent properties of apolipoprotein A1 in micellar complexes with dimyristoyl phosphatidylcholine
A Iu Misharin N Iu Zamaeva I V Antonov N G Bushmakina N V Medvedeva 《Bioorganicheskaia khimiia》1989,15(6):773-780
Bilayer micellar complexes of the human plasma apolipoprotein A1 with dimyristoyl phosphatidylcholine were prepared under kinetically controlled conditions. Detergent-like properties of Apo A1 in the complexes were expressed in terms of delta SA1 parameter (surface area of mixed micelle per an Apo A1 molecule). Analysis of our and earlier published data showed the correlation of the delta SA1 parameter with the stoichiometry of complexes. Changes of detergent-like properties were caused by cross-linking or proteolysis of Apo A1. 相似文献
46.
47.
48.
49.
In energized rat liver mitochondria the simultaneous H+, K+ and C1- transport was studied by corresponding ion selective electrodes. It was shown that the C1- transport induced by valinomycin, by valinomycin plus carbonyclyanide m-chlorophenylhydrazone was governed by the membrane potential. It is suggested that observed in energized mitochondria the C1- electrophoresis may servt as an indicator of membrane potential changes. 相似文献
50.
The fine structure of the centriolar system was studied on serial sections of 90 endothelial cells of human aorta (50 to 60 years) in regions without atherosclerotic platelets and with fibrous and atheromatous platelets and of 30 endothelial cells of human embryonic aorta (22-24 weeks). The vast majority (95%) of endothelial cells of the atheromatous platelets were shown to have a primary cilium over 1 micron long which gives on the basal surface in all the cells. In the regions without platelets and with fibrous platelets a cilium was observed in about 20% of cells and it gives in the vessel lumen. Endothelial cells with a cilium fully embedded in the cytoplasm and with abnormal cilium structure were found in the embryonic aorta. A suggestion is put forward that cilia of the endothelial cells of embryonic aorta and those of adult aorta differ by the mechanism of their formation and can have different functions. 相似文献