全文获取类型
收费全文 | 13271篇 |
免费 | 1189篇 |
国内免费 | 600篇 |
专业分类
电工技术 | 808篇 |
技术理论 | 1篇 |
综合类 | 806篇 |
化学工业 | 2097篇 |
金属工艺 | 860篇 |
机械仪表 | 743篇 |
建筑科学 | 927篇 |
矿业工程 | 353篇 |
能源动力 | 412篇 |
轻工业 | 841篇 |
水利工程 | 237篇 |
石油天然气 | 774篇 |
武器工业 | 91篇 |
无线电 | 1680篇 |
一般工业技术 | 1645篇 |
冶金工业 | 815篇 |
原子能技术 | 164篇 |
自动化技术 | 1806篇 |
出版年
2024年 | 77篇 |
2023年 | 201篇 |
2022年 | 341篇 |
2021年 | 506篇 |
2020年 | 387篇 |
2019年 | 335篇 |
2018年 | 411篇 |
2017年 | 435篇 |
2016年 | 386篇 |
2015年 | 493篇 |
2014年 | 640篇 |
2013年 | 705篇 |
2012年 | 795篇 |
2011年 | 830篇 |
2010年 | 722篇 |
2009年 | 716篇 |
2008年 | 717篇 |
2007年 | 727篇 |
2006年 | 701篇 |
2005年 | 606篇 |
2004年 | 398篇 |
2003年 | 464篇 |
2002年 | 447篇 |
2001年 | 390篇 |
2000年 | 365篇 |
1999年 | 362篇 |
1998年 | 342篇 |
1997年 | 317篇 |
1996年 | 305篇 |
1995年 | 212篇 |
1994年 | 172篇 |
1993年 | 128篇 |
1992年 | 94篇 |
1991年 | 84篇 |
1990年 | 66篇 |
1989年 | 45篇 |
1988年 | 33篇 |
1987年 | 26篇 |
1986年 | 20篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
In this study, a series of T300 carbon fiber‐reinforced polyimide (CFRPI) composites were prepared by laminating premolding polyimide (PI) films with unidirectional carbon fiber (CF) layers. On the basis of PI systems design, the effect of CF volume fraction, processing conditions, and PI molecular structure on the properties of CFRPI composites was studied in detail. In addition, two kinds of nano‐particles, including carbon nano‐tube (CNT) and SiO2 were filled into the premolding PI films with different concentrations. And the effect of nano‐particles on the properties of CFRPI composites was also investigated. The surface characteristic of T300 CF was measured by X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The properties of premolding PI film and CFRPI composites were measured by dynamic mechanical analysis (DMTA), SANS testing machine, scanning electron microscopy (SEM), and so forth. These experimental results showed that the properties of CFRPI composites were mainly affected by the premolding PI film and molding condition. The change of CF volume fraction from 55% to 65% took little effect on the mechanical properties of CFRPI composites. In addition, the incorporation of nano‐particle SiO2 could further improve the properties of CFRPI composites, but CNT hardly improved the properties of CFRPI composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 646–654, 2006 相似文献
172.
缩放管内CaCO_3污垢形成过程的数值模拟 总被引:1,自引:0,他引:1
利用从传热传质角度结合表面化学反应知识模拟CaCO3污垢形成过程的数学模型,对缩放管不同工况进行了数值模拟计算.得出不同工况下,缩放管内CaCO3污垢的沉积率、剥蚀率、污垢热阻随时间的变化规律以及它们与流速、工质浓度、温差的关系. 相似文献
173.
Yue-long Bai) Jun Xu) Zhi-feng Zhang) Wei-min Mao) Hong Xu) ) General Research Institute for Non-ferrous Metals Beijing China ) School of Materials Science Engineering University of Science Technology Beijing Beijing China ) Research Center for Foundry Engineering North University of China Taiyuan China 《北京科技大学学报(英文版)》2009,16(4):422-426
The effect of injection pressure, piston velocity, and the forming temperature of semisolid slurry on the filling behavior of the semi-solid A356 aluminum alloy was investigated by simulation methods. The simulation results show that these processing parameters have an important effect on the filling behavior of the semi-solid A356 aluminum alloy. The slurry flows steadily in the cavity when the injection pressure, the piston velocity, and the forming temperature are low, but it is prone to turbulent flow w... 相似文献
174.
构建新形势下大学生党员发展质量保障体系 总被引:2,自引:0,他引:2
做好当代大学生党员发展工作是加强新形势下党的建设的重要举措。分析了目前高校大学生党员发展工作存在的问题,根据党建的有关原则和精神,提出了构建新形势下大学生党员发展质量保障体系的对策。 相似文献
175.
毛亮清 《重庆科技学院学报(社会科学版)》2011,(9):200-201
以ESP理论为指导,从旅游英语专业学生的学习需求及用人单位的人才规格需求出发,通过对高职旅游英语专业学生及用人单位设计的问卷访谈分析,解读旅游英语专业英语课程设置与人才培养的关系。 相似文献
176.
为了寻找一种合理有效的多机器人任务分配算法,基于多机器人协作救火任务环境,以博弈论纳什均衡为基础,研究多机器人的任务分配问题。根据任务模型特点和纳什均衡的主要特征提出了一种基于博弈论的任务分配算法。博弈的效用函数同时考虑了距离、火势和燃烧时间等因素,机器人根据此效用函数选择行为策略,促使机器人尽快扑灭惩罚值较大的火灾而获得较大的奖励值。利用任务总收益函数值的大小评价算法的优劣性。收益函数与火势、燃烧时间和机器人扑灭火灾数有关,这切合实际救火模型。实验结果证明了该任务分配算法的有效性。 相似文献
177.
气化炉油气掺烧技术探讨 总被引:1,自引:0,他引:1
简要叙述了九江合成氨装置五通道气化烧嘴掺烧干气试验过程,实践证明渣油掺烧干气工艺是可行的。通过对掺烧干气试验结果的理论分析,渣油雾滴的减小和雾化角的减小。使燃烧区上移,在保证渣油充分燃烧的前提下,减少火焰对气化炉壁的冲蚀,会有效增加装置运行周期。 相似文献
178.
Zheng Peng Si‐Dong Li Mao‐Fang Huang Kui Xu Chen Wang Pu‐Wang Li Xiao‐Guang Chen 《应用聚合物科学杂志》2002,85(14):2952-2955
The thermal degradations of methyl methacrylate‐graft‐natural rubber (MG) at different heating rates (B) in nitrogen were studied by thermogravimetric analysis. The results indicate that the thermal degradation of MG in nitrogen is a one‐step reaction. The degradation temperatures increase along with the increment of heating rates. The temperature of initial degradation (T0) is 0.448B + 362.4°C, the temperature at maximum degradation rate, that is, the peak temperature on a differential thermogravimetric curve (Tp) is 0.545B + 380.7°C, and the temperature of final degradation (Tf) is 0.476B + 409.4°C. The degradation rate at Tp is not affected by B, and its average value is 48.9%; the degradation rate at Tf is not affected by B either, and its average value is 99.3%. The reaction order (n) is 2.1 and is not affected by B. The reaction activation energy (E) and the frequency factor (A) increase along with B, and the apparent reaction activation energy (E0) is 254.6 kJ/mol. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2952–2955, 2002 相似文献
179.
The preparation of very hydrophobic poly(vinylidene fluoride) (PVDF) membranes was explored by using two methods. The first one was the modified phase inversion method using a water/N,N‐dimethylacetamide (DMAc) mixture instead of pure water as a soft precipitation bath. The second method was a precipitation‐bath free method, that is, the PVDF/DMAc casting solution underwent gelation in the open air instead of being immersed into a precipitation bath. The morphology of the surface and cross section of the membranes was investigated by using scanning electron microscopy (SEM). It was found that the membranes exhibited certain micro‐ and nanoscale hierarchical roughness on the surface, which brought about an enhanced hydrophobicity of the membrane. The contact angle (CA) of the samples obtained by the second method was as high as 150° with water. The conventional phase inversion method preparing PVDF porous membrane using pure water as precipitation bath usually results in an asymmetric membrane with a dense skin layer having a CA close to that of a smooth PVDF surface. The modified approach avoided the formation of a skin‐layer and resulted in a porous and highly hydrophobic surface of PVDF. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1358–1363, 2005 相似文献
180.
Magnetic‐field probes can be used for electromagnetic interference measurement of high‐speed circuits. The main magnetic probe performance includes sensitivity, spatial resolution, electric‐field suppression ratio (EFSR), and measurement accuracy. In this article, a pair of differential magnetic‐field probes is proposed to improve measurement accuracy without reducing sensitivity. The proposed differential probes consist of two asymmetric loop probes, which are designed in the same plane and separated by a row of periodic vias. The proposed differential probes are fabricated under PCB process. High accuracy can be achieved by measuring difference between outputs of the two probes. In addition, EFSR can be improved by size optimization of the differential magnetic‐field probes. Simulation and measurement results show the operating bandwidth is from 100 MHz to 12 GHz, the measurement error is 3.4% and the EFSR is about 40 dB. The proposed probes have higher measurement accuracy and higher EFSR than the conventional single probe, and larger operation bandwidth than the stacked differential probes. 相似文献