全文获取类型
收费全文 | 27748篇 |
免费 | 15838篇 |
国内免费 | 4篇 |
出版年
2023年 | 16篇 |
2022年 | 100篇 |
2021年 | 427篇 |
2020年 | 2202篇 |
2019年 | 3738篇 |
2018年 | 3839篇 |
2017年 | 4121篇 |
2016年 | 4126篇 |
2015年 | 4086篇 |
2014年 | 3744篇 |
2013年 | 4144篇 |
2012年 | 1851篇 |
2011年 | 1565篇 |
2010年 | 3085篇 |
2009年 | 1828篇 |
2008年 | 749篇 |
2007年 | 333篇 |
2006年 | 322篇 |
2005年 | 374篇 |
2004年 | 344篇 |
2003年 | 359篇 |
2002年 | 325篇 |
2001年 | 342篇 |
2000年 | 256篇 |
1999年 | 204篇 |
1998年 | 56篇 |
1997年 | 44篇 |
1996年 | 40篇 |
1995年 | 48篇 |
1994年 | 41篇 |
1993年 | 36篇 |
1992年 | 71篇 |
1991年 | 48篇 |
1990年 | 56篇 |
1989年 | 56篇 |
1988年 | 49篇 |
1987年 | 42篇 |
1986年 | 41篇 |
1985年 | 43篇 |
1984年 | 33篇 |
1983年 | 41篇 |
1982年 | 19篇 |
1981年 | 25篇 |
1980年 | 19篇 |
1979年 | 28篇 |
1978年 | 22篇 |
1977年 | 25篇 |
1976年 | 23篇 |
1974年 | 22篇 |
1972年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 174 毫秒
911.
Hong Wang Gang Liu Chunxia Li Ann L. T. Powell Michael S. Reid Zhen Zhang Cai‐Zhong Jiang 《Molecular Plant Pathology》2013,14(5):453-469
Ethylene and jasmonate (JA) have powerful effects when plants are challenged by pathogens. The inducible promoter‐regulated expression of the Arabidopsis ethylene receptor mutant ethylene‐insensitive1‐1 (etr1‐1) causes ethylene insensitivity in petunia. To investigate the molecular mechanisms involved in transgenic petunia responses to Botrytis cinerea related to the ethylene and JA pathways, etr1‐1‐expressing petunia plants were inoculated with Botrytis cinerea. The induced expression of etr1‐1 by a chemical inducer dexamethasone resulted in retarded senescence and reduced disease symptoms on detached leaves and flowers or intact plants. The extent of decreased disease symptoms correlated positively with etr1‐1 expression. The JA pathway, independent of the ethylene pathway, activated petunia ethylene response factor (PhERF) expression and consequent defence‐related gene expression. These results demonstrate that ethylene induced by biotic stress influences senescence, and that JA in combination with delayed senescence by etr1‐1 expression alters tolerance to pathogens. 相似文献
912.
913.
914.
915.
Lei Wang Jie Zheng Yanzhong Luo Tao Xu Qiuxue Zhang Lan Zhang Miaoyun Xu Jianmin Wan Ming‐Bo Wang Chunyi Zhang Yunliu Fan 《Plant biotechnology journal》2013,11(8):997-1005
Long hairpin RNA (hpRNA) transgenes are a powerful tool for gene function studies in plants, but a genomewide RNAi mutant library using hpRNA transgenes has not been reported for plants. Here, we report the construction of a hpRNA library for the genomewide identification of gene function in rice using an improved rolling circle amplification‐mediated hpRNA (RMHR) method. Transformation of rice with the library resulted in thousands of transgenic lines containing hpRNAs targeting genes of various function. The target mRNA was down‐regulated in the hpRNA lines, and this was correlated with the accumulation of siRNAs corresponding to the double‐stranded arms of the hpRNA. Multiple members of a gene family were simultaneously silenced by hpRNAs derived from a single member, but the degree of such cross‐silencing depended on the level of sequence homology between the members as well as the abundance of matching siRNAs. The silencing of key genes tended to cause a severe phenotype, but these transgenic lines usually survived in the field long enough for phenotypic and molecular analyses to be conducted. Deep sequencing analysis of small RNAs showed that the hpRNA‐derived siRNAs were characteristic of Argonaute‐binding small RNAs. Our results indicate that RNAi mutant library is a high‐efficient approach for genomewide gene identification in plants. 相似文献
916.
Leonardus W. J. E. Beurskens Lieske H. Schrijver Dick Tibboel Mark F. Wildhagen Maarten F. C. M. Knapen Jan Lindemans Jeanne de Vries Régine P. M. Steegers‐Theunissen 《Birth defects research. Part A, Clinical and molecular teratology》2013,97(1):60-66
BACKGROUND
Vitamin A has been related to the etiology of congenital diaphragmatic hernia (CDH). We performed a case‐control study to investigate whether maternal dietary vitamin A intake is related to CDH in the offspring.METHODS
Thirty‐one pregnancies diagnosed with CDH and 46 control pregnancies were included during the study. After CDH diagnosis and inclusion of controls by risk set sampling, maternal vitamin A intake was investigated with a food frequency questionnaire. Serum retinol and retinol‐binding protein were determined. Univariable and multivariable logistic regression models were used to calculate risk estimates with adjustment for potential confounders.RESULTS
We found no significant differences in the overall nutrient and vitamin A intake between case and control mothers. After stratification in body mass index (BMI) categories, case mothers with normal weight showed a lower energy adjusted vitamin A intake (685 vs. 843 μg retinol activity equivalents [RAEs] / day; p = 0.04) and a slightly lower serum retinol (1.58 vs. 1.67 μmol/L; p = 0.08) than control mothers. Vitamin A intake <800 μg retinol activity equivalents (recommended daily intake) in normal weight mothers was associated with a significantly increased CDH risk (odds ratio [OR], 7.2; 95% confidence interval [CI], 1.5–34.4; p = 0.01). Associations were not significantly different in underweight and overweight mothers.CONCLUSIONS
In normal‐weight mothers, dietary vitamin A intake during pregnancy below the recommended daily intake is significantly associated with an increased risk of a child with CDH. This finding supports the retinoid hypothesis in human CDH, but warrants further investigation in larger study populations. Birth Defects Research (Part A), 2013. © 2013 Wiley Periodicals, Inc. 相似文献917.
918.
Tracie Pennimpede Stefanie Wolter Lars Wittler Anne‐Karoline Ebert Wolfgang Rösch Raimund Stein Enrika Bartels Dominik Schmidt Thomas M. Boemers Eberhard Schmiedeke Per Hoffmann Susanne Moebus Bernhard G. Herrmann Markus M. Nöthen Heiko Reutter Michael Ludwig 《Birth defects research. Part A, Clinical and molecular teratology》2013,97(3):133-139
919.