全文获取类型
收费全文 | 3165篇 |
免费 | 294篇 |
国内免费 | 134篇 |
出版年
2023年 | 32篇 |
2022年 | 71篇 |
2021年 | 155篇 |
2020年 | 88篇 |
2019年 | 88篇 |
2018年 | 96篇 |
2017年 | 61篇 |
2016年 | 121篇 |
2015年 | 183篇 |
2014年 | 192篇 |
2013年 | 225篇 |
2012年 | 283篇 |
2011年 | 241篇 |
2010年 | 135篇 |
2009年 | 124篇 |
2008年 | 158篇 |
2007年 | 155篇 |
2006年 | 158篇 |
2005年 | 139篇 |
2004年 | 82篇 |
2003年 | 94篇 |
2002年 | 78篇 |
2001年 | 45篇 |
2000年 | 64篇 |
1999年 | 50篇 |
1998年 | 34篇 |
1997年 | 35篇 |
1996年 | 30篇 |
1995年 | 29篇 |
1994年 | 23篇 |
1993年 | 29篇 |
1992年 | 43篇 |
1991年 | 29篇 |
1990年 | 26篇 |
1989年 | 32篇 |
1988年 | 28篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1971年 | 3篇 |
排序方式: 共有3593条查询结果,搜索用时 15 毫秒
1.
2.
3.
Yanji Qu Lin Zhuo Na Li Yiqing Hu Weihua Chen Yun Zhou Jinwei Wang Qingmei Tao Jing Hu Xiaolu Nie Siyan Zhan 《PloS one》2015,10(4)
International hospital-based studies have indicated a high risk of cognitive impairment after stroke, evidence from community-based studies in China is scarce. To determine the prevalence of post-stroke cognitive impairment (PSCI) and its subtypes in stroke survivors residing in selected rural and urban Chinese communities, we conducted a community-based, cross-sectional study in 599 patients accounting for 48% of all stroke survivors registered in the 4 communities, who had suffered confirmed strokes and had undergone cognitive assessments via the Montreal Cognitive Assessment (MoCA), Mini-Mental State Examination (MMSE), and Hachinski Ischemia Scale (HIS). Detection of PSCI was based on scores in these neuropsychological scales. Factors potentially impacting on occurrence of PSCI were explored by comparing demographic characteristics, stroke features, and cardiovascular risk factors between patients with and without PSCI. The overall prevalence of PSCI was 80.97% (95%CI: 77.82%-84.11%), while that of non-dementia PSCI (PSCI-ND) and post-stroke vascular dementia (PSD) was 48.91% (95%CI: 44.91%-52.92%) and 32.05% (95%CI: 28.32%-35.79%), respectively. Prior stroke and complications during the acute phase were independent risk factors for PSCI. The risk of recurrent stroke survivors having PSCI was 2.7 times higher than for first-episode survivors, and it was 3 times higher for those with complications during the acute phase than for those without. The higher prevalence of PSCI in this study compared with previous Chinese studies was possibly due to the combined effects of including rural stroke survivors, a longer period from stroke onset, and different assessment methods. There is an urgent need to recognize and prevent PSCI in stroke patients, especially those with recurrent stroke and complications during the acute phase. 相似文献
4.
5.
Heqiao Zhang Dong-Hua Chen Rayees U.H. Mattoo David A. Bushnell Yannan Wang Chao Yuan Lin Wang Chunnian Wang Ralph E. Davis Yan Nie Roger D. Kornberg 《Molecular cell》2021,81(8):1781-1788.e4
- Download : Download high-res image (174KB)
- Download : Download full-size image
6.
7.
8.
9.
Pseudomonas sp. strains, isolated from soil, utilized toluene as their sole carbon source through ameta cleavage pathway. Strains metabolizing toluene through anortho cleavage pathway were selected from the wild typemeta strain. Theortho pathway strains were subjected to chemostat selection to obtain a fast-growing strain with doubling time reduced from 14 to 1.2 h. Benzoale and antibiotics enrichment selection procedures were utilized to select a blocked mutant. The blocked mutant grew on acetate as its sole carbon source and oxidatively converted toluene tocis, cis-muconic acid. Double-blocked and muconate-permeable mutants were also selected to reduce reversion frequency and to enhance muconic acid production. In shake-flask experiments, muconic acid at 3.5 g/l was obtained after 2 days of fermentation. In a 14 l fermenter, muconic acid was produced at 45 g/l in 4 days of controlled fed-batch fermentation. The oxidative bioconversion process was also demonstrated in a 1500 l fermenter.
Résumé Des souches dePseudomonas sp., isolées du sol, ont utilisé le toluène comme seule source de carbone par la vole de la rupture de cycle enmeta. On a sélectionné des souches métabolisant le toluène par la voie de la rupture de cycle enortho, à partir de la souche sauvage de typemeta. Les souches de la voieortho ont été soumises à la sélection en chémostat pour obtenir des souches à croissance rapide dont le temps de doublement est rédult de 14 à 1.2 h. Les procédures de sélection par enrichissement sur benzoale et antibiotiques ont été utilisées pour sélectionner un mutant bloqué. Le mutant bloqué croît sur acétate comme seule source de carbone et convertit le toluène par voie oxydative en acidecis,cis-muconique. On a également sélectionné des mutants doublement bloqués et perméables au muconate pour réduire la lréquence de réversion et pour augmenter la production d'acide muconique. En expérimentation en flacons agités, on a obtenu 3.5 g/l d'acide muconique après 2 jours de fermentation. En fermentuer de 14 l, on a produit 45 g/l d'acide muconique en 4 jours de fermentation contrôlée en milieu non renouvelé à allmentation étagée. Le processus de bioconversion oxydative a également été démontré en fermenteur de 1500 l.相似文献
10.
Cell-specific expression of pyruvate, pi dikinase : in situ mRNA hybridization and immunolocalization labeling of protein in wheat seed 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pyruvate, Pi dikinase (PPDK) is a key enzyme in the C4 photosynthetic pathway. However, its metabolic role in C3 plants remains uncertain. Northern blot analyses of PPDK mRNAs from wheat leaves and seeds probed with maize PPDK cDNA indicates the presence of organ-specific mRNAs. Immunofluorescent labeling of protein in wheat seed demonstrate that the PPDK polypeptide and the ribulose-1, 5-bisphosphate carboxylase small subunit polypeptide are localized predominantly in the aleurone layer and the chlorophyllous pericarp tissue, respectively. This differential distribution of the two polypeptides in wheat seed is paralleled by the differential localization of the their mRNAs as revealed by in situ hybridization. These results suggest a distinct role of cytoplasmic PPDK in seeds, which is different from the well established role in C4 photosynthesis. 相似文献