全文获取类型
收费全文 | 13240篇 |
免费 | 1161篇 |
国内免费 | 588篇 |
专业分类
电工技术 | 795篇 |
技术理论 | 1篇 |
综合类 | 806篇 |
化学工业 | 2080篇 |
金属工艺 | 848篇 |
机械仪表 | 741篇 |
建筑科学 | 985篇 |
矿业工程 | 344篇 |
能源动力 | 418篇 |
轻工业 | 848篇 |
水利工程 | 235篇 |
石油天然气 | 757篇 |
武器工业 | 92篇 |
无线电 | 1682篇 |
一般工业技术 | 1646篇 |
冶金工业 | 782篇 |
原子能技术 | 163篇 |
自动化技术 | 1766篇 |
出版年
2024年 | 63篇 |
2023年 | 190篇 |
2022年 | 323篇 |
2021年 | 498篇 |
2020年 | 368篇 |
2019年 | 330篇 |
2018年 | 409篇 |
2017年 | 425篇 |
2016年 | 381篇 |
2015年 | 494篇 |
2014年 | 631篇 |
2013年 | 692篇 |
2012年 | 807篇 |
2011年 | 829篇 |
2010年 | 725篇 |
2009年 | 718篇 |
2008年 | 726篇 |
2007年 | 736篇 |
2006年 | 711篇 |
2005年 | 612篇 |
2004年 | 403篇 |
2003年 | 462篇 |
2002年 | 444篇 |
2001年 | 390篇 |
2000年 | 370篇 |
1999年 | 369篇 |
1998年 | 336篇 |
1997年 | 315篇 |
1996年 | 303篇 |
1995年 | 211篇 |
1994年 | 170篇 |
1993年 | 126篇 |
1992年 | 96篇 |
1991年 | 81篇 |
1990年 | 65篇 |
1989年 | 45篇 |
1988年 | 33篇 |
1987年 | 25篇 |
1986年 | 19篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 7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
131.
Riccardo Carli Raymond Le Van Mao Claudia L. Blanchi Vittorio Ragaini 《Catalysis Letters》1993,21(3-4):265-274
Gallium species which were incorporated initially in the oxide form, were all in the (+3) oxidation state in the hybrid catalyst and exhibited two types of hydrogen chemisorption sites, shw and shs. The stronger sorption sites shs which predominated at higher gallium dispersion, corresponded probably to the most effective surface configuration for gallium in the aromatization ofn-butane. 相似文献
132.
133.
Fen Yang Xuejun Zhang Xuhui Mao Fuxing Gan 《Journal of the American Ceramic Society》2007,90(4):1019-1028
Highly dispersed antimony (Sb)-doped stannic hydroxide nanoparticles have been successfully prepared using the solution chemistry method. The properties and microstructures of the nanoparticles are investigated in detail by means of infrared, transmission electron microscope, X-ray diffractometer, and Brunauer-Emmett-Teller nitrogen surface area measurements. The results indicate that the properties and microstructures of the nanoparticles strongly depend on the azeotropic solvents used to remove water at the drying stage. Various azeotropic solvents are screened to investigate their effects on the size and dispersivity of dried Sb-doped stannic hydroxide. Three empirical rules are drawn for selecting an effective azeotropic solvent: (1) the solvent molecule should contain at least one atom such as oxygen as the hydrogen (H)-bond acceptor to form H bonds with the surface –OH (acting as an H-bond donor) of polymer particle; (2) the H-bond acceptor should locate in the middle of the alkane chain rather than on the terminal so that the alkane chain can stretch out and cover more surface area, improving the dispersivity of the dried product; and (3) the solvent should have a higher boiling point (∼140°C) to reduce the time of azeotropic distillation for removing water and maintain a lower residual amount of azeotropic agent. Based on the empirical rules, it is discovered that iso-amyl acetate is the most effective azeotropic solvent. 相似文献
134.
MAH接枝EPDM增韧PA66的研究 总被引:7,自引:0,他引:7
研究了MAH(马来酸酐)接枝三元乙丙橡胶(EPDM—g-MAH)对尼龙66(PA66)的增韧作用。利用SEM(扫描电镜)观察了共混体系的微观形貌(形态结构),并运用小角激光散射(SALS)方法研究了EPDM的加入对PA66结晶性能的影响。结果表明,未接枝的EPDM与PA66的相容性很差,而EPDM—g—MAH与PA66相容性明显增加,EPDM-g—MAH粒子均匀分散在PA66中,共混体系力学性能有很大提高。随着EPDM—g—MAH用量的增加,PA66球晶尺寸变小,共混体系界面结合更加紧密。 相似文献
135.
This paper presents a novel Hough context model for detecting and localizing instances of a certain object class. In particular, our approach detects the object in parameter space by applying Hough voting in context. First, in Hough context, the features around object center or a point in parameter space are sampled and organized in context sense respectively for both training images and test images. Then a parametric discriminant function is constructed based on the Hough context. Such function scores the existence likelihood of object centers in parameter space. Finally, we formulate the training process of this discriminative model as a structure learning problem, which has already been well solved. Compared with the ISM-related methods that the voting is performed by the features independently, the core contribution of our method is that the voting based on context information is available. The experiments on several popular and challenging object datasets (i.e., ETHZ Shape, UIUC Cars, and PASCAL VOC 2007) demonstrate that the detection accuracy can be improved and the voting speed are impressively accelerated via using Hough context. 相似文献
136.
高耐蚀性Zn—Co合金镀层钝化工艺的研究 总被引:1,自引:0,他引:1
研究了电镀Zn-Co合金镀层的钝化液的组成及工艺条件,溶液各成分及工艺条件对钝化膜质量的影响,通过几种腐蚀试验方法,测量了钝化膜的耐蚀性,结果表明,研究的钝化工艺可以得到耐蚀性良好的钝化膜。 相似文献
137.
138.
139.
140.
A method for the preparation of high surface area coatings and its application towards fabrication of prospective composite electrocatalysts for hydrogen evolution is proposed. Exploratory studies with such a composite, (Ni/LaNiO3), as a hydrogen electrode in alkaline solutions indicate that it is a more active electrocatalyst than sintered or electrodeposited nickel. The electrocatalytic properties were found to be a strong function of the deposition parameters as well as of the history of the oxide powder. 相似文献