全文获取类型
收费全文 | 17304篇 |
免费 | 1427篇 |
国内免费 | 1291篇 |
出版年
2024年 | 63篇 |
2023年 | 241篇 |
2022年 | 588篇 |
2021年 | 937篇 |
2020年 | 666篇 |
2019年 | 739篇 |
2018年 | 730篇 |
2017年 | 579篇 |
2016年 | 761篇 |
2015年 | 1126篇 |
2014年 | 1279篇 |
2013年 | 1349篇 |
2012年 | 1603篇 |
2011年 | 1401篇 |
2010年 | 895篇 |
2009年 | 680篇 |
2008年 | 826篇 |
2007年 | 706篇 |
2006年 | 628篇 |
2005年 | 541篇 |
2004年 | 424篇 |
2003年 | 356篇 |
2002年 | 370篇 |
2001年 | 280篇 |
2000年 | 262篇 |
1999年 | 221篇 |
1998年 | 152篇 |
1997年 | 133篇 |
1996年 | 122篇 |
1995年 | 100篇 |
1994年 | 112篇 |
1993年 | 77篇 |
1992年 | 119篇 |
1991年 | 103篇 |
1990年 | 105篇 |
1989年 | 88篇 |
1988年 | 70篇 |
1987年 | 90篇 |
1986年 | 65篇 |
1985年 | 51篇 |
1984年 | 42篇 |
1983年 | 27篇 |
1982年 | 28篇 |
1980年 | 25篇 |
1979年 | 32篇 |
1978年 | 21篇 |
1977年 | 23篇 |
1975年 | 19篇 |
1973年 | 24篇 |
1972年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Jian‐Yong Guo Yong‐Sheng Wang Tian Chen Xiao‐Xu Jiang Ping Wu Tao Geng Zhong‐Hua Pan Meng‐Ke Shang Cheng‐Xiang Hou Kun Gao Xi‐Jie Guo 《Insect Science》2020,27(3):449-462
Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) is a major pathogen of the economic insect silkworm, Bombyx mori. Virus‐encoded microRNAs (miRNAs) have been proven to play important roles in host–pathogen interactions. In this study we identified a BmCPV‐derived miRNA‐like 21 nt small RNA, BmCPV‐miR‐1, from the small RNA deep sequencing of BmCPV‐infected silkworm larvae by stem‐loop quantitative real‐time PCR (qPCR) and investigated its functions with qPCR and lentiviral expression systems. Bombyx mori inhibitor of apoptosis protein (BmIAP) gene was predicted by both target prediction software miRanda and Targetscan to be one of its target genes with a binding site for BmCPV‐miR‐1 at the 5′ untranslated region. It was found that the expression of BmCPV‐miR‐1 and its target gene BmIAP were both up‐regulated in BmCPV‐infected larvae. At the same time, it was confirmed that BmCPV‐miR‐1 could up‐regulate the expression of BmIAP gene in HEK293T cells with lentiviral expression systems and in BmN cells by transfecting mimics. Furthermore, BmCPV‐miR‐1 mimics could up‐regulate the expression level of BmIAP gene in midgut and fat body in the silkworm. In the midgut of BmCPV‐infected larvae, BmCPV‐miR‐1 mimics could be further up‐regulated and inhibitors could lower the virus‐mediated expression of BmIAP gene. With the viral genomic RNA segments S1 and S10 as indicators, BmCPV‐miR‐1 mimics could up‐regulate and inhibitors down‐regulate their replication in the infected silkworm. These results implied that BmCPV‐miR‐1 could inhibit cell apoptosis in the infected silkworm through up‐regulating BmIAP expression, providing the virus with a better cell circumstance for its replication. 相似文献
13.
14.
Yunhe Meng Xixi Shao Yan Wang Yumei Li Xiaojian Zheng Gongyuan Wei Seon-Won Kim Chonglong Wang 《Biotechnology and bioengineering》2020,117(11):3499-3507
Squalene is a lipophilic and non-volatile triterpene with many industrial applications for food, pharmaceuticals, and cosmetics. Metabolic engineering focused on optimization of the production pathway suffer from little success in improving titers because of a limited space of the cell membrane accommodating the lipophilic product. Extension of cell membrane would be a promising approach to overcome the storage limitation for successful production of squalene. In this study, Escherichia coli was engineered for squalene production by overexpression of some membrane proteins. The highest production of 612 mg/L was observed in the engineered E. coli with overexpression of Tsr, a serine chemoreceptor protein, which induced invagination of inner membrane to form multilayered structure. It was also observed an increase in unsaturated fatty acid in membrane lipids composition, suggesting cellular response to maintain membrane fluidity against squalene accumulation in the engineered strain. This study potentiates the capability of E. coli for squalene production and provides an effective strategy for the enhanced production of such compounds. 相似文献
15.
16.
17.
18.
19.
To overcome the high energy-consuming process of microalgae drying, a two-step lipase catalysis technique for the preparation of biodiesel from microalgae lipid of Chlorella spp. was developed. In the first step, free fatty acids (FAAs) and triacylglycerols (TAGs) are released after cell disruption and extracted, while the TAGs were hydrolysed by free lipase in aqueous phase. In the second step, FAAs were esterified with ethanol in the catalysis of free suspended lipase. The maximum rate of hydrolysis and esterification was 93.6% and 91.3%, respectively. The effects of reaction parameters, such as reaction time, enzyme amount, water content and molar ratio of lipid to ethanol on hydrolysis or esterification, were investigated. The results indicated that two-step reaction process (hydrolyse esterify) for biodiesel production were feasible. 相似文献
20.