全文获取类型
收费全文 | 113419篇 |
免费 | 7993篇 |
国内免费 | 3244篇 |
专业分类
电工技术 | 4743篇 |
技术理论 | 4篇 |
综合类 | 4408篇 |
化学工业 | 19815篇 |
金属工艺 | 5349篇 |
机械仪表 | 6884篇 |
建筑科学 | 5738篇 |
矿业工程 | 1364篇 |
能源动力 | 3743篇 |
轻工业 | 8165篇 |
水利工程 | 1439篇 |
石油天然气 | 2849篇 |
武器工业 | 485篇 |
无线电 | 17128篇 |
一般工业技术 | 18241篇 |
冶金工业 | 8187篇 |
原子能技术 | 1355篇 |
自动化技术 | 14759篇 |
出版年
2024年 | 283篇 |
2023年 | 1354篇 |
2022年 | 2439篇 |
2021年 | 3629篇 |
2020年 | 2613篇 |
2019年 | 2410篇 |
2018年 | 2848篇 |
2017年 | 3024篇 |
2016年 | 3349篇 |
2015年 | 3624篇 |
2014年 | 4841篇 |
2013年 | 6906篇 |
2012年 | 6844篇 |
2011年 | 7952篇 |
2010年 | 6663篇 |
2009年 | 6541篇 |
2008年 | 6356篇 |
2007年 | 5661篇 |
2006年 | 5436篇 |
2005年 | 4674篇 |
2004年 | 3872篇 |
2003年 | 3626篇 |
2002年 | 3868篇 |
2001年 | 3139篇 |
2000年 | 2689篇 |
1999年 | 2472篇 |
1998年 | 3217篇 |
1997年 | 2294篇 |
1996年 | 1981篇 |
1995年 | 1649篇 |
1994年 | 1304篇 |
1993年 | 1124篇 |
1992年 | 811篇 |
1991年 | 750篇 |
1990年 | 606篇 |
1989年 | 552篇 |
1988年 | 448篇 |
1987年 | 348篇 |
1986年 | 313篇 |
1985年 | 267篇 |
1984年 | 229篇 |
1983年 | 166篇 |
1982年 | 174篇 |
1981年 | 151篇 |
1980年 | 145篇 |
1979年 | 110篇 |
1978年 | 95篇 |
1977年 | 123篇 |
1976年 | 166篇 |
1975年 | 87篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The Journal of Supercomputing - Spark is one of the most widely used systems for the distributed processing of big data. Its performance bottlenecks are mainly due to the network I/O, disk I/O, and... 相似文献
32.
33.
34.
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
35.
36.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
37.
38.
39.
40.
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