全文获取类型
收费全文 | 169145篇 |
免费 | 9076篇 |
国内免费 | 4898篇 |
专业分类
电工技术 | 7560篇 |
技术理论 | 8篇 |
综合类 | 5257篇 |
化学工业 | 20314篇 |
金属工艺 | 9510篇 |
机械仪表 | 7428篇 |
建筑科学 | 7549篇 |
矿业工程 | 2519篇 |
能源动力 | 4989篇 |
轻工业 | 10295篇 |
水利工程 | 2301篇 |
石油天然气 | 4025篇 |
武器工业 | 814篇 |
无线电 | 23831篇 |
一般工业技术 | 29067篇 |
冶金工业 | 28028篇 |
原子能技术 | 2285篇 |
自动化技术 | 17339篇 |
出版年
2024年 | 425篇 |
2023年 | 1549篇 |
2022年 | 3215篇 |
2021年 | 4313篇 |
2020年 | 3247篇 |
2019年 | 2749篇 |
2018年 | 3514篇 |
2017年 | 3684篇 |
2016年 | 3540篇 |
2015年 | 4239篇 |
2014年 | 5460篇 |
2013年 | 9315篇 |
2012年 | 7770篇 |
2011年 | 9329篇 |
2010年 | 7793篇 |
2009年 | 8102篇 |
2008年 | 8121篇 |
2007年 | 7893篇 |
2006年 | 7285篇 |
2005年 | 6263篇 |
2004年 | 5153篇 |
2003年 | 4461篇 |
2002年 | 3965篇 |
2001年 | 4010篇 |
2000年 | 3707篇 |
1999年 | 3982篇 |
1998年 | 10109篇 |
1997年 | 6704篇 |
1996年 | 5324篇 |
1995年 | 3557篇 |
1994年 | 3117篇 |
1993年 | 2963篇 |
1992年 | 1834篇 |
1991年 | 1713篇 |
1990年 | 1620篇 |
1989年 | 1400篇 |
1988年 | 1246篇 |
1987年 | 904篇 |
1986年 | 920篇 |
1985年 | 945篇 |
1984年 | 817篇 |
1983年 | 709篇 |
1982年 | 712篇 |
1981年 | 689篇 |
1980年 | 577篇 |
1979年 | 483篇 |
1978年 | 414篇 |
1977年 | 536篇 |
1976年 | 966篇 |
1975年 | 301篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
31.
32.
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
34.
J. Cochard P. Léonide J. Borgomano Y. Guglielmi G. Massonnat J-P. Rolando L. Marié A. Pasquier 《Journal of Petroleum Geology》2020,43(1):75-94
Upper Barremian – Lower Aptian inner platform “Urgonian” limestones in the Mont de Vaucluse region, SE France, consist of alternating metre-scale microporous and tight intervals. This paper focuses on the influence of structural deformation on the reservoir properties of the Urgonian limestone succession in a study area near the town of Rustrel. Petrographic, petrophysical and structural data were recovered from five fully-cored boreholes, from the walls of a 100 m long underground tunnel, and from a 50 m long transect at a nearby outcrop. The data allowed reservoir property variations in the Urgonian limestones to be studied from core to reservoir scale. Eleven Reservoir Rock Types (RRTs) were identified based on petrographic features (texture, grain size), reservoir properties (porosity, permeability), and the frequency of structural discontinuities such as fractures, faults and stylolites. Tight and microporous reservoir rock types were distinguished. Tight reservoir rock types were characterised by early cementation of intergranular pore spaces and by the presence of frequent structural discontinuities. By contrast microporous reservoir rock types contained preserved intragranular microporosity and matrix permeability, but had very few structural discontinuities. Observed vertical alternations of microporous and tight rock types are interpreted to have been controlled by the early diagenesis of the Urgonian carbonates. Deformation associated with regional-scale tectonic phases, including Albian – Cenomanian “Durancian” uplift (∼105 to 96 Ma) and Pyrenean compression (∼55 to 25 Ma), resulted in the modification of the initial petrophysical properties of the Urgonian limestones. An early diagenetic imprint conditioned both the intensity of structural deformations and the associated circulations of diagenetic and meteoric fluids. Evolution of the Reservoir Rock Types is therefore linked both to the depositional conditions and to subsequent phases of structural deformation. 相似文献
35.
36.
37.
38.
39.
Xuejing Lin Zhangxiao Peng Changqing Su 《International journal of molecular sciences》2015,16(5):10888-10906
Costunolide (CE) and dehydrocostuslactone (DE) are derived from many species of medicinal plants, such as Saussurea lappa Decne and Laurus nobilis L. They have been reported for their wide spectrum of biological effects, including anti-inflammatory, anticancer, antiviral, antimicrobial, antifungal, antioxidant, antidiabetic, antiulcer, and anthelmintic activities. In recent years, they have caused extensive interest in researchers due to their potential anti-cancer activities for various types of cancer, and their anti-cancer mechanisms, including causing cell cycle arrest, inducing apoptosis and differentiation, promoting the aggregation of microtubule protein, inhibiting the activity of telomerase, inhibiting metastasis and invasion, reversing multidrug resistance, restraining angiogenesis has been studied. This review will summarize anti-cancer activities and associated molecular mechanisms of these two compounds for the purpose of promoting their research and application. 相似文献
40.