全文获取类型
收费全文 | 76748篇 |
免费 | 4241篇 |
国内免费 | 857篇 |
学科分类
工业技术 | 81846篇 |
出版年
2024年 | 79篇 |
2023年 | 772篇 |
2022年 | 807篇 |
2021年 | 1946篇 |
2020年 | 1461篇 |
2019年 | 1442篇 |
2018年 | 1785篇 |
2017年 | 1900篇 |
2016年 | 2177篇 |
2015年 | 2005篇 |
2014年 | 2869篇 |
2013年 | 4569篇 |
2012年 | 4373篇 |
2011年 | 5168篇 |
2010年 | 4045篇 |
2009年 | 4204篇 |
2008年 | 4028篇 |
2007年 | 3521篇 |
2006年 | 3381篇 |
2005年 | 3048篇 |
2004年 | 2549篇 |
2003年 | 2364篇 |
2002年 | 2256篇 |
2001年 | 1816篇 |
2000年 | 1877篇 |
1999年 | 1907篇 |
1998年 | 2831篇 |
1997年 | 1988篇 |
1996年 | 1701篇 |
1995年 | 1419篇 |
1994年 | 1060篇 |
1993年 | 937篇 |
1992年 | 701篇 |
1991年 | 665篇 |
1990年 | 550篇 |
1989年 | 520篇 |
1988年 | 411篇 |
1987年 | 320篇 |
1986年 | 300篇 |
1985年 | 274篇 |
1984年 | 217篇 |
1983年 | 156篇 |
1982年 | 164篇 |
1981年 | 143篇 |
1980年 | 138篇 |
1979年 | 108篇 |
1978年 | 97篇 |
1977年 | 125篇 |
1976年 | 163篇 |
1975年 | 80篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
31.
32.
Jie-Long He An-Te Chen Jyong-Huei Lee Shih-Kang Fan 《International journal of molecular sciences》2015,16(9):22319-22332
The basic structural and functional unit of a living organism is a single cell. To understand the variability and to improve the biomedical requirement of a single cell, its analysis has become a key technique in biological and biomedical research. With a physical boundary of microchannels and microstructures, single cells are efficiently captured and analyzed, whereas electric forces sort and position single cells. Various microfluidic techniques have been exploited to manipulate single cells through hydrodynamic and electric forces. Digital microfluidics (DMF), the manipulation of individual droplets holding minute reagents and cells of interest by electric forces, has received more attention recently. Because of ease of fabrication, compactness and prospective automation, DMF has become a powerful approach for biological application. We review recent developments of various microfluidic chips for analysis of a single cell and for efficient genetic screening. In addition, perspectives to develop analysis of single cells based on DMF and emerging functionality with high throughput are discussed. 相似文献
33.
34.
Wenshu Chen Jiajun Gu Yongping Du Fang Song Fanxing Bu Jinghan Li Yang Yuan Ruichun Luo Qinglei Liu Di Zhang 《Advanced functional materials》2020,30(25)
Large‐scale production of hydrogen from water‐alkali electrolyzers is impeded by the sluggish kinetics of hydrogen evolution reaction (HER) electrocatalysts. The hybridization of an acid‐active HER catalyst with a cocatalyst at the nanoscale helps boost HER kinetics in alkaline media. Here, it is demonstrated that 1T–MoS2 nanosheet edges (instead of basal planes) decorated by metal hydroxides form highly active / heterostructures, which significantly enhance HER performance in alkaline media. Featured with rich / sites, the fabricated 1T–MoS2 QS/Ni(OH)2 hybrid (quantum sized 1T–MoS2 sheets decorated with Ni(OH)2 via interface engineering) only requires overpotentials of 57 and 112 mV to drive HER current densities of 10 and 100 mA cm?2, respectively, and has a low Tafel slope of 30 mV dec?1 in 1 m KOH. So far, this is the best performance for MoS2‐based electrocatalysts and the 1T–MoS2 QS/Ni(OH)2 hybrid is among the best‐performing non‐Pt alkaline HER electrocatalysts known. The HER process is durable for 100 h at current densities up to 500 mA cm?2. This work not only provides an active, cost‐effective, and robust alkaline HER electrocatalyst, but also demonstrates a design strategy for preparing high‐performance catalysts based on edge‐rich 2D quantum sheets for other catalytic reactions. 相似文献
35.
36.
37.
38.
Jeongchan Lee Dr. Joonwon Kim Hyun Kim Eun-Jung Kim Prof. Dr. Hee-Jin Jeong Prof. Dr. Kwon-Young Choi Prof. Dr. Byung-Gee Kim 《Chembiochem : a European journal of chemical biology》2020,21(10):1446-1452
Tryptophan halogenases are found in diverse organisms and catalyze regiospecific halogenation. They play an important role in the biosynthesis of halogenated indole alkaloids, which are biologically active and of therapeutic importance. Here, a tryptophan 6-halogenase (SatH) from Streptomyces albus was characterized by using a whole-cell reaction system in Escherichia coli. SatH showed substrate specificity for chloride and bromide ions, leading to regiospecific halogenation at the C6-position of l -tryptophan. In addition, SatH exhibited higher performance in bromination than that of previously reported tryptophan halogenases in the whole-cell reaction system. Through structure-based protein mutagenesis, it has been revealed that two consecutive residues, A78/V79 in SatH and G77/I78 in PyrH, are key determinants in the regioselectivity difference between tryptophan 6- and 5-halogenases. Substituting the AV with GI residues switched the regioselectivity of SatH by moving the orientation of tryptophan. These data contribute to an understanding of the key residues that determine the regioselectivity of tryptophan halogenases. 相似文献
39.
40.