全文获取类型
收费全文 | 508452篇 |
免费 | 6746篇 |
国内免费 | 1463篇 |
专业分类
电工技术 | 9325篇 |
综合类 | 505篇 |
化学工业 | 77820篇 |
金属工艺 | 20413篇 |
机械仪表 | 15479篇 |
建筑科学 | 12607篇 |
矿业工程 | 2809篇 |
能源动力 | 12351篇 |
轻工业 | 44658篇 |
水利工程 | 5289篇 |
石油天然气 | 9988篇 |
武器工业 | 84篇 |
无线电 | 60130篇 |
一般工业技术 | 98654篇 |
冶金工业 | 91740篇 |
原子能技术 | 11540篇 |
自动化技术 | 43269篇 |
出版年
2021年 | 4085篇 |
2019年 | 3837篇 |
2018年 | 6672篇 |
2017年 | 6705篇 |
2016年 | 7224篇 |
2015年 | 4699篇 |
2014年 | 7881篇 |
2013年 | 22054篇 |
2012年 | 12611篇 |
2011年 | 17122篇 |
2010年 | 13749篇 |
2009年 | 15469篇 |
2008年 | 16359篇 |
2007年 | 16133篇 |
2006年 | 14539篇 |
2005年 | 13383篇 |
2004年 | 12626篇 |
2003年 | 12255篇 |
2002年 | 12057篇 |
2001年 | 11858篇 |
2000年 | 11321篇 |
1999年 | 11469篇 |
1998年 | 26844篇 |
1997年 | 19633篇 |
1996年 | 15484篇 |
1995年 | 11917篇 |
1994年 | 10715篇 |
1993年 | 10520篇 |
1992年 | 8290篇 |
1991年 | 7860篇 |
1990年 | 7579篇 |
1989年 | 7431篇 |
1988年 | 7247篇 |
1987年 | 6254篇 |
1986年 | 6162篇 |
1985年 | 7197篇 |
1984年 | 6804篇 |
1983年 | 6137篇 |
1982年 | 5804篇 |
1981年 | 6034篇 |
1980年 | 5740篇 |
1979年 | 5497篇 |
1978年 | 5462篇 |
1977年 | 6335篇 |
1976年 | 8048篇 |
1975年 | 5022篇 |
1974年 | 4866篇 |
1973年 | 4903篇 |
1972年 | 4100篇 |
1971年 | 3858篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Multimedia Tools and Applications - Remote Sensing categorical signature classification has gained significant implications on spatial resolution image analysis due to differences in the... 相似文献
2.
Knaust Thiemo Felnhofer Anna Kothgassner Oswald D. Hllmer Helge Gorzka Robert-Jacek Schulz Holger 《Virtual Reality》2022,26(3):925-938
Virtual Reality - It is generally accepted that natural environments reduce stress and improve mood. Since access to natural environments is sometimes limited, virtual natural environments,... 相似文献
3.
Kuznetsov Yu. A. Markov M. A. Kravchenko I. N. Krasikov A. V. Bykova A. D. 《Refractories and Industrial Ceramics》2021,62(4):421-425
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized... 相似文献
4.
Chumakov Yu. A. Knyazeva A. G. Pribytkov G. A. 《Theoretical Foundations of Chemical Engineering》2021,55(3):490-503
Theoretical Foundations of Chemical Engineering - On the basis of the classic concepts of the theory of solid-phase combustion, for the first time, a model with a detailed scheme of chemical... 相似文献
5.
6.
Engineering new glass compositions have experienced a sturdy tendency to move forward from (educated) trial-and-error to data- and simulation-driven strategies. In this work, we developed a computer program that combines data-driven predictive models (in this case, neural networks) with a genetic algorithm to design glass compositions with desired combinations of properties. First, we induced predictive models for the glass transition temperature (Tg) using a dataset of 45,302 compositions with 39 different chemical elements, and for the refractive index (nd) using a dataset of 41,225 compositions with 38 different chemical elements. Then, we searched for relevant glass compositions using a genetic algorithm informed by a design trend of glasses having high nd (1.7 or more) and low Tg (500 °C or less). Two candidate compositions suggested by the combined algorithms were selected and produced in the laboratory. These compositions are significantly different from those in the datasets used to induce the predictive models, showing that the used method is indeed capable of exploration. Both glasses met the constraints of the work, which supports the proposed framework. Therefore, this new tool can be immediately used for accelerating the design of new glasses. These results are a stepping stone in the pathway of machine learning-guided design of novel glasses. 相似文献
7.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical... 相似文献
8.
To investigate the evolution of the structural and enhanced magnetic properties of GdMnO3 systems induced by the substitution of Mn with Cr, polycrystalline GdMn1-xCrxO3 samples were synthesized via solid-state reactions. XRD characterization shows that all GdMn1-xCrxO3 compounds with single-phase structures crystallize well and that Cr3+ ions entering the lattice sites of GdMnO3 induce structural distortion. SEM results indicate that the grain size of the synthesized samples (a few microns) decreases as the Cr substitution concentration increases. Positron annihilation lifetime spectroscopy reveals that vacancy-type defects occur in GdMn1-xCrxO3 ceramics and that the vacancy size and concentration clearly change with the Cr content. The temperature and field dependence of the magnetization curves show that Cr substitution significantly influences the magnetic ordering of the gadolinium sublattice, improving the weak ferromagnetic transition temperature and magnetization of GdMn1-xCrxO3. The enhanced magnetization of GdMn1-xCrxO3 is closely related to the vacancy defect concentration. 相似文献
9.
Seredin P. V. Radam Ali Obaid Goloshchapov D. L. Len’shin A. S. Buylov N. S. Barkov K. A. Nesterov D. N. Mizerov A. M. Timoshnev S. N. Nikitina E. V. Arsentyev I. N. Sharafidinov Sh. Kukushkin S. A. Kasatkin I. A. 《Semiconductors》2022,56(4):253-258
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid... 相似文献
10.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is... 相似文献