全文获取类型
收费全文 | 10587篇 |
免费 | 957篇 |
国内免费 | 593篇 |
专业分类
电工技术 | 538篇 |
技术理论 | 1篇 |
综合类 | 1382篇 |
化学工业 | 816篇 |
金属工艺 | 177篇 |
机械仪表 | 282篇 |
建筑科学 | 2195篇 |
矿业工程 | 446篇 |
能源动力 | 161篇 |
轻工业 | 399篇 |
水利工程 | 441篇 |
石油天然气 | 319篇 |
武器工业 | 63篇 |
无线电 | 729篇 |
一般工业技术 | 620篇 |
冶金工业 | 261篇 |
原子能技术 | 79篇 |
自动化技术 | 3228篇 |
出版年
2024年 | 27篇 |
2023年 | 136篇 |
2022年 | 194篇 |
2021年 | 275篇 |
2020年 | 275篇 |
2019年 | 219篇 |
2018年 | 215篇 |
2017年 | 263篇 |
2016年 | 297篇 |
2015年 | 325篇 |
2014年 | 778篇 |
2013年 | 639篇 |
2012年 | 812篇 |
2011年 | 836篇 |
2010年 | 761篇 |
2009年 | 777篇 |
2008年 | 775篇 |
2007年 | 796篇 |
2006年 | 697篇 |
2005年 | 598篇 |
2004年 | 510篇 |
2003年 | 423篇 |
2002年 | 326篇 |
2001年 | 269篇 |
2000年 | 234篇 |
1999年 | 151篇 |
1998年 | 102篇 |
1997年 | 76篇 |
1996年 | 62篇 |
1995年 | 57篇 |
1994年 | 50篇 |
1993年 | 41篇 |
1992年 | 28篇 |
1991年 | 28篇 |
1990年 | 21篇 |
1989年 | 18篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1974年 | 1篇 |
1970年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
51.
工字梁的抗剪极限承载力 总被引:5,自引:0,他引:5
对工字梁腹板抗剪极限承载力的研究进行总结,对各种公式与文献中的试验结果进行对比,将拉力场理论和转向应力场理论的假定与ANSYS分析揭示的腹板应力发展变化规律进行对比,指出了假定和数值分析结果的不一致。提出了翼缘对腹板转动约束的合理参数,得到精度良好的考虑翼缘约束的腹板剪切屈曲系数。利用得到的屈曲系数,考虑翼缘抗弯承载力的贡献,提出新的工字梁抗剪极限承载力的计算公式。与现有试验数据和ANSYS非线性有限元分析结果的对比,证实建议方法离散性较小,适用范围广,尤其是对于通用高厚比较大的梁,较以往方法有了较大改进。 相似文献
52.
Web社区是互联网中自组织程度较高的部分,它不是一个孤立系统,而是一个耗散系统,很多时候涨落无法耗散摔,导致社区运行不稳定.基尼系数可以用来衡量Web社区稳定性,通过基尼系数的简易计算公式计算社区内部成员积分或者其它参数,可以得出Web社区稳定性的度量.该度量对于研究和利用Web社区具有重要参考意义. 相似文献
53.
Hai-Yang Li Sheng-Gang Li 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2008,12(5):487-492
This paper is devoted to congruences and ideals in pseudoeffect algebras. Let I be a normal ideal in a pseudoeffect algebra E. We show that: (1) the relation ~
I
induced by I is a congruence if and only if for every a∈E, I∩ [0,a] is upper directed; (2) the relation ~
I
induced by I is a strong congruence if and only if I is a normal weak Riesz ideal in a pseudoeffect algebra E. Moreover, we introduce a stronger concept of congruence—namely Riesz strong congruence—and we prove that, if I is a normal weak Riesz ideal in a pseudoeffect algebra E, then ~
I
is a Riesz strong congruence and, conversely, if ~ is a Riesz strong congruence, then I = [0]~ is a normal weak Riesz ideal, and ~
I
= ~.
This work was supported by the National Natural Science Foundation of China (Grant No. 10271069). 相似文献
54.
Web 2.0 has been becoming the new tendency of the Internet development. In order to get better management of web 2.0 network resource and guarantee of service quality, the architecture and the advantages of web 2.0 over Ajax technology is analyzed, and the impact of Ajax on bandwidth performance of web application is discussed. 相似文献
55.
The conversion of heavy paraffin and aromatics into a high-quality diesel fraction was performed in a microplant using a WNiPd/CeY-alumina catalyst. The effects of aromatics and naphtheno-aromatics on mild hydrocracking of hexadecane were studied at different concentrations. Two catalysts, with and without Pd and thermal treatment, were characterized by FTIR, XPS, and TPD of ammonia and ammonia plus naphthalene to complement previous study about the surface composition. The hydrocracking activity and selectivity were tested using different amounts and types of aromatics. This study demonstrated the presence of two acid strengths that contribute in different ways to paraffin and aromatics isomerization, ring opening, and cracking reactions. The product distribution obtained by mild hydrocracking of n-C16 is between amorphous (SiO2Al2O3) and Y-zeolite type of support. The aromatic adsorption on acid sites reduces the cracking rate and improves the survival of di- and tri-branched paraffin. A model for the path of reaction is discussed to explain the results. 相似文献
56.
This paper presents the Navigation Maps Modeling approach (NMM), which provides platform independent models for characterizing navigation maps of web applications. The NMM approach is conceived to obtain a trade off between high and low-level design notations. As high-level design notations, NMM models permit architectural details that may hinder the overall understanding of the web application to be left out. As low-level design notations, NMM models can easily be transformed into detailed architectural designs, which are very valuable at coding and maintenance stages. 相似文献
57.
强潮河口桩式丁坝减冲促淤效果研究 总被引:3,自引:0,他引:3
钱塘江涌潮气势雄伟,世界闻名,但对海塘具有很大的破坏力.该文提出了一种新颖的丁坝型式——桩式丁坝,从现场观测资料对比、实体模型试验和机理分析三个方面,分析桩式丁坝的减冲促淤效果,探究丁坝护滩保塘的机理.与堆石丁坝比较,桩式丁坝具有设计合理、施工简易、坝体内无内压力、有效地减轻了局部冲刷、便于维护检修等一系列优点。桩式丁坝可广泛应用于各类河道整治、海塘保护等工程中. 相似文献
58.
An ordering of magnesium is observed in the as-synthesized MAPO-36 molecular sieve. Upon calcination, part of the magnesium is removed from the sample and part occupies extraframework positions thus rendering a random distribution of magnesium in the lattice. The shoulder observed in the31P spectrum of the calcined sample is assigned to P(3Al, 1Mg) sites in conflict with the earlier assignment to P-OH groups. The bridging hydroxyl groups located at these sites are detected in the1H MAS spectrum at 3.6 ppm. Further, MAPO-36 catalyzed acetone conversion to mesityloxide that cracked at elevated temperature to yield acetic acid and aliphatics. 相似文献
59.
60.