全文获取类型
收费全文 | 41533篇 |
免费 | 3748篇 |
国内免费 | 4605篇 |
出版年
2024年 | 126篇 |
2023年 | 551篇 |
2022年 | 1245篇 |
2021年 | 2077篇 |
2020年 | 1477篇 |
2019年 | 1805篇 |
2018年 | 1725篇 |
2017年 | 1317篇 |
2016年 | 1736篇 |
2015年 | 2622篇 |
2014年 | 3099篇 |
2013年 | 3300篇 |
2012年 | 4009篇 |
2011年 | 3550篇 |
2010年 | 2318篇 |
2009年 | 2080篇 |
2008年 | 2382篇 |
2007年 | 2121篇 |
2006年 | 1834篇 |
2005年 | 1644篇 |
2004年 | 1372篇 |
2003年 | 1259篇 |
2002年 | 1094篇 |
2001年 | 768篇 |
2000年 | 653篇 |
1999年 | 601篇 |
1998年 | 381篇 |
1997年 | 321篇 |
1996年 | 292篇 |
1995年 | 228篇 |
1994年 | 221篇 |
1993年 | 147篇 |
1992年 | 207篇 |
1991年 | 177篇 |
1990年 | 157篇 |
1989年 | 130篇 |
1988年 | 114篇 |
1987年 | 107篇 |
1986年 | 84篇 |
1985年 | 88篇 |
1984年 | 47篇 |
1983年 | 40篇 |
1982年 | 40篇 |
1981年 | 25篇 |
1980年 | 28篇 |
1979年 | 33篇 |
1978年 | 25篇 |
1977年 | 27篇 |
1975年 | 22篇 |
1973年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
31.
Plasmonics - We investigate aluminum nanopatch/nanohole arrays surrounded by a dielectric material on plastic substrates for large area color printing. In this specific arrangement, metallic... 相似文献
32.
33.
Xiao-Long Lin Yan-Min Zhao Li-Ping Yan Wen-Bin Liu Wen-Jun Bu Xin-Hua Wang Chen-Guang Zheng 《Zoologica scripta》2022,51(1):119-132
Evolutionary analysis of Prodiamesinae has long been impeded by lack of information, and its phylogenetic relationship with Orthocladiinae remains questionable. Here, ten complete mitochondrial genomes (mitogenomes) of Orthocladiinae sensu lato were newly sequenced, including three Prodiamesinae species and seven Orthocladiinae species. Coupled with published mitogenomes, a total of 12 mitogenomes of Orthocladiinae sensu lato were selected for a comparative mitogenomic analysis and phylogenetic reconstruction. Mitogenomes of Orthocladiinae sensu lato are conserved in structure, and all genes arrange the same gene order as the ancestral insect mitogenome. Nucleotide composition is highly biased, and the control region displayed the highest A + T content. All protein-coding genes are under purifying selection, and the ATP8 evolves at the fastest rate. In addition, the mitogenomes of Orthocladiinae sensu lato are highly conserved, and they are practically useful for phylogenetic inference, suggesting a re-classification of Orthocladiinae by sinking Prodiamesinae as a subgroup of Orthocladiinae. 相似文献
34.
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
35.
36.
37.
38.
39.
40.
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