全文获取类型
收费全文 | 14004篇 |
免费 | 1262篇 |
国内免费 | 225篇 |
专业分类
15491篇 |
出版年
2023年 | 101篇 |
2022年 | 178篇 |
2021年 | 364篇 |
2020年 | 232篇 |
2019年 | 245篇 |
2018年 | 323篇 |
2017年 | 265篇 |
2016年 | 407篇 |
2015年 | 673篇 |
2014年 | 655篇 |
2013年 | 809篇 |
2012年 | 959篇 |
2011年 | 887篇 |
2010年 | 578篇 |
2009年 | 535篇 |
2008年 | 743篇 |
2007年 | 662篇 |
2006年 | 592篇 |
2005年 | 562篇 |
2004年 | 591篇 |
2003年 | 519篇 |
2002年 | 476篇 |
2001年 | 414篇 |
2000年 | 343篇 |
1999年 | 315篇 |
1998年 | 158篇 |
1997年 | 101篇 |
1996年 | 109篇 |
1995年 | 135篇 |
1994年 | 107篇 |
1993年 | 94篇 |
1992年 | 173篇 |
1991年 | 197篇 |
1990年 | 143篇 |
1989年 | 162篇 |
1988年 | 144篇 |
1987年 | 131篇 |
1986年 | 112篇 |
1985年 | 136篇 |
1984年 | 114篇 |
1983年 | 90篇 |
1982年 | 64篇 |
1981年 | 66篇 |
1980年 | 64篇 |
1979年 | 71篇 |
1978年 | 75篇 |
1977年 | 65篇 |
1975年 | 53篇 |
1974年 | 49篇 |
1973年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
G. Matthew Hebdon Harry Le Vine Naji E. Sahyoun Claus J. Schmitges Pedro Cuatrecasas 《Life sciences》1980,26(17):1385-1396
3T3C2 mouse fibroblasts rendered permeable to (α?32P)NAD+ show cholera toxin-dependent labeling of a 45,000 m.w. protein and of a doublet of polypeptides around 52,000 m.w. These same bands are ADP-ribosylated in broken cells. Membranes prepared from pigeon erythrocytes pretreated with choleragen show a decrease in subsequent cholera toxin-specific ADP-ribosylation of a 43,000 m.w. polypeptide. Both whole cell and broken cell adenylate cyclase activation and toxin-specific ADP-ribosylation are reversed specifically by low pH and high concentrations of toxin and nicotinamide in all systems. Thus ADP-ribosylation appears to be relevant to the molecular action of choleragen in whole cells as well as in broken cells. 相似文献
22.
23.
Chap T. Le 《Biometrical journal. Biometrische Zeitschrift》1988,30(1):87-92
The distribution-free test against ordered alternatives proposed by Jonckheere (1954) is based on the Kendall's rank correlation coefficient τ. A new rank test is proposed and illustrated with a numerical example. The proposed test is based on Spearman's σ and has similar functional structure as the Kruskal-Wallis test. A useful by-product is a test for departure from a trend. 相似文献
24.
25.
Six bisindole alkaloids have been isolated from the leaves of Dyera costulata (Apocynaceae). One is the known ochrolifuanine A and the others are the novel ochrolifuanines E and F, and the 18-dehydroochrolifuanines A, E and F. 相似文献
26.
Jorge E. Ramos Gretta T. Pecl Natalie A. Moltschaniwskyj Jan M. Strugnell Rafael I. León Jayson M. Semmens 《PloS one》2014,9(8)
Understanding the response of any species to climate change can be challenging. However, in short-lived species the faster turnover of generations may facilitate the examination of responses associated with longer-term environmental change. Octopus tetricus, a commercially important species, has undergone a recent polewards range shift in the coastal waters of south-eastern Australia, thought to be associated with the southerly extension of the warm East Australian Current. At the cooler temperatures of a polewards distribution limit, growth of a species could be slower, potentially leading to a bigger body size and resulting in a slower population turnover, affecting population viability at the extreme of the distribution. Growth rates, body size, and life span of O. tetricus were examined at the leading edge of a polewards range shift in Tasmanian waters (40°S and 147°E) throughout 2011. Octopus tetricus had a relatively small body size and short lifespan of approximately 11 months that, despite cooler temperatures, would allow a high rate of population turnover and may facilitate the population increase necessary for successful establishment in the new extended area of the range. Temperature, food availability and gender appear to influence growth rate. Individuals that hatched during cooler and more productive conditions, but grew during warming conditions, exhibited faster growth rates and reached smaller body sizes than individuals that hatched into warmer waters but grew during cooling conditions. This study suggests that fast growth, small body size and associated rapid population turnover may facilitate the range shift of O. tetricus into Tasmanian waters. 相似文献
27.
28.
29.
Maria A. Papathanasopoulos Francois Krier Anne-Marie Revol-Junelles Gerard Lefebvre Jean Pierre Le Caer Alexander von Holy John W. Hastings 《Current microbiology》1997,35(6):331-335
Leuconostoc (Lc.) mesenteroides TA33a produced three bacteriocins with different inhibitory activity spectra. Bacteriocins were purified by adsorption/desorption
from producer cells and reverse phase high-performance liquid chromatography. Leucocin C-TA33a, a novel bacteriocin with a
predicted molecular mass of 4598 Da, inhibited Listeria and other lactic acid bacteria (LAB). Leucocin B-TA33a has a predicted molecular mass of 3466 Da, with activity against Leuconostoc/Weissella (W.) strains, and appears similar to mesenterocin 52B and dextranicin 24, while leucocin A-TA33a, which also inhibited Listeria and other LAB strains, is identical to leucocin A-UAL 187. A survey of other known bacteriocin-producing Leuconostoc/Weissella strains for the presence of the three different bacteriocins revealed that production of leucocin A-, B- and C-type bacteriocins
was widespread. Lc. carnosum LA54a, W. paramesenteroides LA7a, and Lc. gelidum UAL 187-22 produced all three bacteriocins, whereas W. paramesenteroides OX and Lc. carnosum TA11a produced only leucocin A- and B-type bacteriocins.
Received: 11 April 1997 / Accepted: 10 June 1997 相似文献
30.
Abdulrazak Osama Han Ming Gan Cindy Shuan Ju Teh Kien-Pong Yap Kwai-Lin Thong 《Journal of bacteriology》2012,194(24):6933
The genome sequence analysis of a clinical Vibrio cholerae VC35 strain from an outbreak case in Malaysia indicates multiple genes involved in host adaptation and a novel Na+-driven multidrug efflux pump-coding gene in the genome of Vibrio cholerae with the highest similarity to VMA_001754 of Vibrio mimicus VMA223. 相似文献