全文获取类型
收费全文 | 15410篇 |
免费 | 563篇 |
国内免费 | 2篇 |
出版年
2022年 | 91篇 |
2021年 | 195篇 |
2020年 | 143篇 |
2019年 | 153篇 |
2018年 | 318篇 |
2017年 | 262篇 |
2016年 | 387篇 |
2015年 | 446篇 |
2014年 | 519篇 |
2013年 | 708篇 |
2012年 | 716篇 |
2011年 | 776篇 |
2010年 | 466篇 |
2009年 | 368篇 |
2008年 | 508篇 |
2007年 | 587篇 |
2006年 | 577篇 |
2005年 | 519篇 |
2004年 | 489篇 |
2003年 | 501篇 |
2002年 | 452篇 |
2001年 | 302篇 |
2000年 | 245篇 |
1999年 | 201篇 |
1998年 | 121篇 |
1992年 | 251篇 |
1991年 | 237篇 |
1990年 | 190篇 |
1989年 | 218篇 |
1988年 | 236篇 |
1987年 | 241篇 |
1986年 | 222篇 |
1985年 | 253篇 |
1984年 | 208篇 |
1983年 | 168篇 |
1979年 | 240篇 |
1978年 | 158篇 |
1977年 | 140篇 |
1976年 | 142篇 |
1975年 | 172篇 |
1974年 | 272篇 |
1973年 | 262篇 |
1972年 | 254篇 |
1971年 | 252篇 |
1970年 | 262篇 |
1969年 | 247篇 |
1968年 | 195篇 |
1967年 | 198篇 |
1966年 | 176篇 |
1965年 | 131篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Igor Loncaric Gabrielle L. Stalder Kemal Mehinagic Renate Rosengarten Franz Hoelzl Felix Knauer Chris Walzer 《PloS one》2013,8(12)
In order to test whether rooks (Corvus frugilegus) represent good indicators for the potential circulation of antibiotics in their native habitat, two populations with different migratory behavior were tested for the presence of beta-lactamase producing Enterobacteriaceae and methicillin-resistant Staphylococcus aureus (MRSA). In all, 54 and 102 samples of fresh feces of a migratory and a resident population were investigated. A total of 24 and 3 cefotaxime-resistant enterobacterial isolates were obtained from the migratory and resident population, respectively. In these isolates CTX-M-1 (n = 15), CTX-M-3 (n = 3), and CTX-M-15 (n = 3) genes were detected. TEM-1 and OXA-1 were associated with CTX-M in 3 and 2 isolates, respectively. In two E. coli isolates CMY-2 could be detected, where from one isolate displayed an overexpression of chromosomal AmpC as well. Among E. coli isolates the most common phylogenetic group was A (n = 11) and ST1683 (n = 5). In one E. coli of B2-ST131 the rfbO25b locus was detected. Three Enterobacter isolates were stably derepressed AmpC-producers. In five samples of the migratory population, PVL positive MRSA could be isolated. Two isolates were typed SCCmec IVa, spa type t127, and ST1. Three isolates carried a SCCmec type IVc, with spa type t852 and ST22. The highly significant difference of the occurrence of antibiotic resistance between the migratory population from eastern Europe compared to resident population in our study indicates that rooks may be good indicator species for the evaluation of environmental contamination with antibiotic resistant bacteria, especially due to their ecology, foraging behavior and differing migratory behavior. 相似文献
2.
3.
4.
5.
I P Grigor'ev A A Neokesari?ski? 《Biulleten' eksperimental'no? biologii i meditsiny》1986,102(9):288-289
The effects of different concentrations of L-ascorbic acid (Asc) on Na+-dependent binding of 3H-GABA and 3H-DL-glutamic acid to rat brain cortical synaptosomes were studied. Asc, at a concentration nearly equal to brain extracellular one (3 X 10(-4) M), had no effect on specific and nonspecific 5H-GABA binding. At higher concentrations (10(-3) M) Asc strongly inhibited, and at lower concentrations (10(-6) M) considerably stimulated 3H-GABA binding. At a concentration of 10(-5)-10(-3) M Asc tended to decrease 3H-DL-glutamic acid binding. 相似文献
6.
7.
8.
9.
M. Filek J. Biesaga-Kościelniak I. Marcińska M. Cvikrová I. Macháčková J. Krekule 《Biologia Plantarum》2010,54(3):483-487
The contents of endogenous free and conjugated polyamines, putrescine (Put) and spermidine (Spd), were determined during 9
week of vernalization (at 5 °C) in winter wheat seedlings cultivated on Murashige and Skoog media without (MS0) and with 2
mg dm−3 zearalenone (MSZEN). At the 4th week of chilling treatment, which is sufficient to induce generative development in 30 % of plants, the marked increase in
free and conjugated forms of Put and free Spd were observed. The presence of ZEN in medium significantly accelerated the vernalization.
About 20 % of plants treated with ZEN flowered already after 2 weeks and 40 % after 3 weeks of chilling. Significantly higher
content of free Put was determined in roots grown on MSZEN compared with MS0 during the first 5 weeks of vernalization with
maximum at the 4th week. After germination, a marked decrease in free Spd content was observed both in plants grown on MS0 and MSZEN. Application
of ZEN significantly slowed down the Spd decline in leaves and roots during the first and second week of vernalization. The
content of Spd and its conjugates decreased in vernalized plants after 1 week of cultivation at 20 °C. 相似文献
10.