全文获取类型
收费全文 | 282869篇 |
免费 | 3535篇 |
国内免费 | 721篇 |
专业分类
电工技术 | 5104篇 |
综合类 | 285篇 |
化学工业 | 43150篇 |
金属工艺 | 16557篇 |
机械仪表 | 11983篇 |
建筑科学 | 5654篇 |
矿业工程 | 2783篇 |
能源动力 | 6121篇 |
轻工业 | 15236篇 |
水利工程 | 4020篇 |
石油天然气 | 8880篇 |
武器工业 | 26篇 |
无线电 | 28753篇 |
一般工业技术 | 64257篇 |
冶金工业 | 39680篇 |
原子能技术 | 7524篇 |
自动化技术 | 27112篇 |
出版年
2021年 | 2914篇 |
2020年 | 2293篇 |
2019年 | 2795篇 |
2018年 | 11753篇 |
2017年 | 12169篇 |
2016年 | 8965篇 |
2015年 | 3145篇 |
2014年 | 4599篇 |
2013年 | 10132篇 |
2012年 | 8794篇 |
2011年 | 15330篇 |
2010年 | 13462篇 |
2009年 | 12895篇 |
2008年 | 12800篇 |
2007年 | 14390篇 |
2006年 | 5919篇 |
2005年 | 8319篇 |
2004年 | 6563篇 |
2003年 | 6205篇 |
2002年 | 5083篇 |
2001年 | 4619篇 |
2000年 | 4404篇 |
1999年 | 4290篇 |
1998年 | 10312篇 |
1997年 | 7294篇 |
1996年 | 5601篇 |
1995年 | 4204篇 |
1994年 | 3676篇 |
1993年 | 3920篇 |
1992年 | 3046篇 |
1991年 | 3053篇 |
1990年 | 2929篇 |
1989年 | 2882篇 |
1988年 | 2896篇 |
1987年 | 2533篇 |
1986年 | 2601篇 |
1985年 | 2878篇 |
1984年 | 2711篇 |
1983年 | 2578篇 |
1982年 | 2320篇 |
1981年 | 2288篇 |
1980年 | 2364篇 |
1979年 | 2374篇 |
1978年 | 2399篇 |
1977年 | 2503篇 |
1976年 | 2899篇 |
1975年 | 2199篇 |
1974年 | 2077篇 |
1973年 | 2172篇 |
1972年 | 1943篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Zinov’eva I. V. Fedorov A. Ya. Milevskii N. A. Zakhodyaeva Yu. A. Voshkin A. A. 《Theoretical Foundations of Chemical Engineering》2021,55(4):663-670
Theoretical Foundations of Chemical Engineering - A choline chloride–sulfosalicylic acid deep eutectic solvent (DES) is proposed for dissolving the oxides Co(II), Cu(II), Zn(II), Fe(III),... 相似文献
102.
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
103.
Pressure-assisted infiltration was used to synthesize SiC/Al 6061 composites containing high weight percentages of SiC. A combination of PEG and glass water was used to fabricate SiC preforms and the effect of the presence of glass water on the microstructure and mechanical properties of the preforms was evaluated by performing compression tests on the preforms. Also, the compressive strength and the hardness of the SiC/Al composites were investigated. The results revealed that the glass water improved the compressive strength of the preforms by about five times. The microstructural characterization of the composites showed that the penetration of the aluminum melt into the preforms was completed and almost no porosity could be seen in the microstructures of the composites. Moreover, the composite containing 75 wt% SiC exhibited the highest compressive strength as well as the maximum hardness. The results of the wear tests showed that increasing the SiC content reduces the wear rate so that the Al-75 wt% SiC composite has a lower wear rate and a lower coefficient of friction than those of Al-67 wt% SiC composite. This indicated higher wear resistance in these composites than the Al alloy due to the formation of a tribological layer on the surface of the composites. 相似文献
104.
Abdou Safaa N. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(10):3962-3975
Journal of Inorganic and Organometallic Polymers and Materials - The reaction of potassium tetracyanocupprate(I) with triethyltin bromide in presence of phenanthroline (Phen) and quinoxaline (Qox)... 相似文献
105.
Correction to: Cloud-based vehicular networks: a taxonomy,survey, and conceptual hybrid architecture
Jabbarpour Mohammad Reza Marefat Alireza Jalooli Ali Zarrabi Houman 《Wireless Networks》2019,25(2):913-913
Wireless Networks - The original version of this article unfortunately contained a mistake in the title. The correct title has been published with this erratum. 相似文献
106.
Khalid Tauqeer Khan Abdul Nasir Ali Mazhar Adeel Adil ur Rehman Khan Atta Shuja Junaid 《Multimedia Tools and Applications》2019,78(17):24595-24615
Multimedia Tools and Applications - The world is facing many problems including that of traffic congestion. To highlight the issue of traffic congestion worldwide specially in urban areas and to... 相似文献
107.
Byakova O. V. Stepanov G. V. Vlasov A. O. Danylyuk V. E. Semenov N. V. Berezovs’kyi O. M. Gnyloskurenko S. V. 《Strength of Materials》2019,51(5):726-734
Strength of Materials - The paper addresses the investigation of high-strain rate compressive behavior of Al foams subjected to impact at the intermediate striking velocity ranged from 40 to... 相似文献
108.
The potential energy profile of the reaction between dimethyl disulfide and OH? radicals is explored by utilizing ab initio and hybrid meta density functional theory methods. Having the energies and structural data of the stationary points, statistical rate theories, such as transition state theory and variable reaction coordinate-transition state theory, are employed to compute the overall rate constants, and discuss the mechanism and product channels. On the basis of the calculations, the overall rate coefficient is predicted to be 2.49?×?10?10?cm3?molecule?1?s?1 at 298?K. It is found that in the most favorable pathway, the reaction proceeds via formation of the relatively unstable intermediate CH3S?(OH)SCH3 decomposing rapidly to yield CH3S?+CH3SOH. 相似文献
109.
Maqbool Ali Jamil Hussain Sungyoung Lee Byeong Ho Kang Kashif Sattar 《Expert Systems》2020,37(1):e12401
The case-based learning (CBL) approach has gained attention in medical education as an alternative to traditional learning methodology. However, current CBL systems do not facilitate and provide computer-based domain knowledge to medical students for solving real-world clinical cases during CBL practice. To automate CBL, clinical documents are beneficial for constructing domain knowledge. In the literature, most systems and methodologies require a knowledge engineer to construct machine-readable knowledge. Keeping in view these facts, we present a knowledge construction methodology (KCM-CD) to construct domain knowledge ontology (i.e., structured declarative knowledge) from unstructured text in a systematic way using artificial intelligence techniques, with minimum intervention from a knowledge engineer. To utilize the strength of humans and computers, and to realize the KCM-CD methodology, an interactive case-based learning system(iCBLS) was developed. Finally, the developed ontological model was evaluated to evaluate the quality of domain knowledge in terms of coherence measure. The results showed that the overall domain model has positive coherence values, indicating that all words in each branch of the domain ontology are correlated with each other and the quality of the developed model is acceptable. 相似文献
110.
A new, efficient and recoverable heterogeneous catalyst was successfully synthesized by functionalization of mesoporous silica FSM-16. The FSM-16/CPTMS-Rh- 相似文献