全文获取类型
收费全文 | 306810篇 |
免费 | 5360篇 |
国内免费 | 1647篇 |
专业分类
电工技术 | 5935篇 |
技术理论 | 1篇 |
综合类 | 1051篇 |
化学工业 | 48853篇 |
金属工艺 | 12962篇 |
机械仪表 | 9611篇 |
建筑科学 | 8070篇 |
矿业工程 | 2125篇 |
能源动力 | 7361篇 |
轻工业 | 27854篇 |
水利工程 | 3548篇 |
石油天然气 | 7657篇 |
武器工业 | 122篇 |
无线电 | 33384篇 |
一般工业技术 | 59724篇 |
冶金工业 | 52862篇 |
原子能技术 | 7707篇 |
自动化技术 | 24990篇 |
出版年
2021年 | 3289篇 |
2019年 | 2604篇 |
2018年 | 4371篇 |
2017年 | 4412篇 |
2016年 | 4653篇 |
2015年 | 3333篇 |
2014年 | 5363篇 |
2013年 | 13408篇 |
2012年 | 8266篇 |
2011年 | 10777篇 |
2010年 | 8824篇 |
2009年 | 9846篇 |
2008年 | 10046篇 |
2007年 | 9798篇 |
2006年 | 8719篇 |
2005年 | 8011篇 |
2004年 | 7297篇 |
2003年 | 6955篇 |
2002年 | 7000篇 |
2001年 | 6831篇 |
2000年 | 6448篇 |
1999年 | 6492篇 |
1998年 | 15130篇 |
1997年 | 11323篇 |
1996年 | 8790篇 |
1995年 | 6662篇 |
1994年 | 6043篇 |
1993年 | 5887篇 |
1992年 | 4535篇 |
1991年 | 4476篇 |
1990年 | 4331篇 |
1989年 | 4338篇 |
1988年 | 4276篇 |
1987年 | 3627篇 |
1986年 | 3612篇 |
1985年 | 4195篇 |
1984年 | 3982篇 |
1983年 | 3650篇 |
1982年 | 3443篇 |
1981年 | 3585篇 |
1980年 | 3440篇 |
1979年 | 3383篇 |
1978年 | 3463篇 |
1977年 | 3953篇 |
1976年 | 5056篇 |
1975年 | 3170篇 |
1974年 | 3008篇 |
1973年 | 3029篇 |
1972年 | 2654篇 |
1971年 | 2477篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
91.
V.A. Dekhtyarenko T.V. Pryadko D.G. Savvakin V.I. Bondarchuk G.S. Mogylnyy 《International Journal of Hydrogen Energy》2021,46(11):8040-8047
The influence of phase composition and microstructure of Ti42.75Zr27Mn20.25V10 alloy on its hydrogenation kinetic and phase composition of hydrogenated product was studied. It is established that the process of dissociation of hydrogen molecules begins on the surface of Laves phase crystallites. The dissolution of atomic hydrogen in the material volume leads to the formation of cracks in the intermetallic crystallites, which further appear as additional centers of dissociation of hydrogen molecules and noticeably accelerate the diffusion of hydrogen into the bulk material. It was shown that the Laves phase acts as a donor of atomic hydrogen for the BCC solid solution during hydrogenation of two-phase structure, initiating intensive hydrogenation of the BCC phase at room temperature. 相似文献
92.
Chinh Ngo Radhika Mehta Kanchan Aggarwal Audrey G. Fikes Dr. Ines C. Santos Dr. Sylvester M. Greer Prof. Dr. Emily L. Que 《Chembiochem : a European journal of chemical biology》2019,20(8):1003-1007
One-third of all proteins are estimated to require metals for structural stability and/or catalytic activity. Desthiobiotin probes containing metal binding groups can be used to capture metalloproteins with exposed active-site metals under mild conditions so as to prevent changes in metallation state. The proof-of-concept was demonstrated with carbonic anhydrase (CA), an open active site, Zn2+-containing protein. CA was targeted by using sulfonamide derivatives. Linkers of various lengths and structures were screened to determine the optimal structure for capture of the native protein. The optimized probes could selectively pull down CA from red blood cell lysate and other protein mixtures. Pull-down of differently metallated CAs was also investigated. 相似文献
93.
Jagadeesh Babu Sriramoju Murthy Muniyappa Navya Rani Marilingaiah Chetana Sabbanahalli Manjunath Shetty Ravi Mudike Chitrabanu C.P Prasanna D. Shivaramu Nagaraju G Kanchugarakoppal S. Rangappa Ananda Kumar C.S Dinesh Rangappa 《Ceramics International》2021,47(7):10314-10321
Application of brown titanium dioxide (TiO2-x) and its modified composite forms in the photocatalytic decomposition of organic pollutants in the environment is a promising way to provide solutions for environmental redemption. Herein, we report the synthesis of effective and stable TiO2-x nanoparticles with g-C3N4, RGO, and multiwalled carbon nanotubes (CNTs) using a simple hydrothermal method. Among all the as-synthesized samples, excellent photocatalytic degradation activity was observed for RGO-TiO2-x nanocomposite with high rate constants of 0.075 min?1, 0.083 min?1 and 0.093 min?1 for methylene blue, rhodamine-B, and rosebengal dyes under UV–Visible light irradiation, respectively. The altered bandgap (1.8 eV) and the large surface area of RGO-TiO2-x nanocomposite impacts on both absorption of visible light and efficiency of photogenerated charge electron (e?)/hole (h+) pair separation. This resulted in enhanced photocatalytic property of carbon-based TiO2-x nanocomposites. A systematic study on the influence of different carbon nanostructures on the photocatalytic activity of brown TiO2-x is carried out. 相似文献
94.
95.
Kozhitov L. V. Kiselev B. G. Raykova T. B. Popkova A. V. Kostishin V. G. Muratov D. G. Yakushko E. V. Kosushkin V. G. Bebenin V. G. 《Russian Microelectronics》2019,48(8):599-612
Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical... 相似文献
96.
Kazantsev Yu. N. Kraftmakher G. A. Mal’tsev V. P. 《Journal of Communications Technology and Electronics》2019,64(6):550-554
Journal of Communications Technology and Electronics - Approximate formulas for calculating the coefficient of reflection from an artificial magnetic conductor (AMC) based on a capacitive lattice... 相似文献
97.
Simutin A. N. Deineko A. V. Zertsalov M. G. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2021,55(4):482-486
Power Technology and Engineering - The monitoring of hydraulic structures as high-risk facilities is discussed. Monitoring should ensure the reliability and functioning of a hydraulic structure... 相似文献
98.
Chertkov Yu. B. Anikin M. N. Lebedev I. I. Naimushin A. G. Smol’nikov N. V. 《Atomic Energy》2021,131(1):42-45
Atomic Energy - The results of calculations and experimental determination of the neutronics characteristics of the IRT-T research reactor are presented. The IRT-T reactor is a pool reactor with... 相似文献
99.
Lorenzo Zallocco Laura Giusti Maurizio Ronci Andrea Mussini Marco Trerotola Maria Rosa Mazzoni Antonio Lucacchini Laura Sebastiani 《International journal of molecular sciences》2021,22(9)
The autonomic nervous system (ANS) plays a crucial role both in acute and chronic psychological stress eliciting changes in many local and systemic physiological and biochemical processes. Salivary secretion is also regulated by ANS. In this study, we explored salivary proteome changes produced in thirty-eight University students by a test stress, which simulated an oral exam. Students underwent a relaxation phase followed by the stress test during which an electrocardiogram was recorded. To evaluate the effect of an olfactory stimulus, half of the students were exposed to a pleasant odor diffused in the room throughout the whole session. Saliva samples were collected after the relaxation phase (T0) and the stress test (T1). State anxiety was also evaluated at T0 and T1. Salivary proteins were separated by two-dimensional electrophoresis, and patterns at different times were compared. Spots differentially expressed were trypsin digested and identified by mass spectrometry. Western blot analysis was used to validate proteomic results. Anxiety scores and heart rate changes indicated that the fake exam induced anxiety. Significant changes of α-amylase, polymeric immunoglobulin receptor (PIGR), and immunoglobulin α chain (IGHA) secretion were observed after the stress test was performed in the two conditions. Moreover, the presence of pleasant odor reduced the acute social stress affecting salivary proteome changes. Therefore, saliva proteomic analysis was a useful approach to evaluate the rapid responses associated to an acute stress test also highlighting known biomarkers. 相似文献
100.