全文获取类型
收费全文 | 73304篇 |
免费 | 6022篇 |
国内免费 | 38篇 |
出版年
2022年 | 642篇 |
2021年 | 1203篇 |
2020年 | 914篇 |
2019年 | 965篇 |
2018年 | 1507篇 |
2017年 | 1286篇 |
2016年 | 2110篇 |
2015年 | 3151篇 |
2014年 | 3059篇 |
2013年 | 3978篇 |
2012年 | 4731篇 |
2011年 | 4421篇 |
2010年 | 2660篇 |
2009年 | 2468篇 |
2008年 | 3414篇 |
2007年 | 3350篇 |
2006年 | 3128篇 |
2005年 | 3386篇 |
2004年 | 3270篇 |
2003年 | 2830篇 |
2002年 | 2392篇 |
2001年 | 1852篇 |
2000年 | 1791篇 |
1999年 | 1586篇 |
1998年 | 724篇 |
1997年 | 677篇 |
1996年 | 703篇 |
1995年 | 592篇 |
1994年 | 578篇 |
1993年 | 526篇 |
1992年 | 1144篇 |
1991年 | 1048篇 |
1990年 | 956篇 |
1989年 | 916篇 |
1988年 | 919篇 |
1987年 | 828篇 |
1986年 | 779篇 |
1985年 | 740篇 |
1984年 | 697篇 |
1983年 | 532篇 |
1982年 | 418篇 |
1981年 | 438篇 |
1980年 | 395篇 |
1979年 | 542篇 |
1978年 | 467篇 |
1977年 | 378篇 |
1976年 | 342篇 |
1975年 | 376篇 |
1974年 | 398篇 |
1973年 | 368篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
The stoichiometric palmitoyllysophosphatidylcholine (lysoPC)/gramicidin (4:1, mol/mol) lamellar complex (Killian, J.A., De Kruijff, B., Van Echteld, C.J.A., Verkleij, A.J., Leunissen-Bijvelt, J. and De Gier, J. (1983) Biochim. Biophys. Acta 728, 141-144) is a useful model system to investigate the various aspects of lipid protein interactions. To study the effect of gramicidin on local order and motion of 1-palmitoyl-sn-glycero-3-phosphocholine (lysoPC) we employed 31P and 2H nuclear magnetic resonance (NMR) using selectively deuterated lysoPC's and we compared the results to those obtained for lysoPC in bilayers with cholesterol (1:1, mol/mol) and dipalmitoylphosphatidylcholine (DPPC) (1:4, mol/mol). 2H-NMR experiments on acyl chain deuterated lysoPC showed similar quadrupole splittings in the liquid crystalline state for the lysoPC/DPPC and the lysoPC/gramicidin samples. In the lysoPC/cholesterol sample an increase of the quadrupole splitting was found. T1 measurements showed that gramicidin decreases the lysoPC acyl chain motion, especially at the C12 position. In the lysoPC/cholesterol sample an increase of motion was observed as compared to lysoPC in fluid bilayers of DPPC. 31P-NMR and 2-H-NMR measurements of lysoPC, deuterated at the alpha- and beta-position of the choline moiety, indicated an increase in headgroup flexibility in all samples as compared to the parent compound DPPC. In addition, a change in headgroup conformation was observed. The alpha- and beta-segments in all samples exhibited concerted motion. It was found that also in the polar headgroup gramicidin induces a decrease of the rate of motion. 相似文献
83.
84.
85.
Jeroen M. G. Stevens Hilde Vervaecke Han de Vries Linda van Elsacker 《International journal of primatology》2007,28(6):1417-1430
Bonobos have a reputation as a female-dominated and egalitarian species. We examined the 2 aspects of dominance in 6 captive
bonobo groups. Females do not consistently evoke submission from all males in all contexts. Though females occupy the highest-ranking
positions in the dominance hierarchy, there are in each group males that obtain rather high ranks and are able to dominate
≥1 female. Thus female dominance is not complete and hierarchies can be better described as nonexclusive female dominance.
We studied egalitarianism by measuring linearity and steepness of dominance hierarchies. The hierarchies of all groups are
highly linear. Hierarchies among males are steeper than among females. On average, male bonobos are more despotic than females,
but females too can have despotic relations, both with other females and with males. Hence one can call bonobos in captivity
semidespotic rather than egalitarian. 相似文献
86.
Antoine Wystrach Sebastian Schwarz Patrick Schultheiss Guy Beugnon Ken Cheng 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(2):167-179
The Australian desert ant Melophorus bagoti often follows stereotypical routes through a cluttered landscape containing both distant panoramic views and obstacles (plants)
to navigate around. We created an artificial obstacle course for the ants between a feeder and their nest. Landmarks comprised
natural objects in the landscape such as logs, branches, and tussocks. Many ants travelled stereotypical routes home through
the obstacle course in training, threading repeatedly the same gaps in the landmarks. Manipulations altering the relations
between the landmarks and the surrounding panorama, however, affected the routes in two major ways. Both interchanging the
positions of landmarks (transpositions) and displacing the entire landmark set along with the starting position of the ants
(translations) (1) reduced the stereotypicality of the route, and (2) increased turns and meanders during travel. The ants
might have used the entire panorama in view-based travel, or the distal panorama might prime the identification and use of
landmarks en route. Despite the large data set, both options (not mutually exclusive) remain viable. 相似文献
87.
Martin T. R. Kuiper Marijke Holtrop Hans de Vries 《Molecular & general genetics : MGG》1988,213(2-3):519-528
88.
89.