全文获取类型
收费全文 | 14599篇 |
免费 | 1742篇 |
国内免费 | 1028篇 |
专业分类
电工技术 | 4383篇 |
综合类 | 980篇 |
化学工业 | 1408篇 |
金属工艺 | 848篇 |
机械仪表 | 640篇 |
建筑科学 | 315篇 |
矿业工程 | 417篇 |
能源动力 | 807篇 |
轻工业 | 354篇 |
水利工程 | 72篇 |
石油天然气 | 468篇 |
武器工业 | 592篇 |
无线电 | 1984篇 |
一般工业技术 | 2020篇 |
冶金工业 | 698篇 |
原子能技术 | 267篇 |
自动化技术 | 1116篇 |
出版年
2024年 | 63篇 |
2023年 | 261篇 |
2022年 | 422篇 |
2021年 | 432篇 |
2020年 | 497篇 |
2019年 | 445篇 |
2018年 | 419篇 |
2017年 | 589篇 |
2016年 | 681篇 |
2015年 | 664篇 |
2014年 | 877篇 |
2013年 | 796篇 |
2012年 | 1009篇 |
2011年 | 1144篇 |
2010年 | 836篇 |
2009年 | 857篇 |
2008年 | 817篇 |
2007年 | 909篇 |
2006年 | 904篇 |
2005年 | 694篇 |
2004年 | 571篇 |
2003年 | 574篇 |
2002年 | 489篇 |
2001年 | 420篇 |
2000年 | 367篇 |
1999年 | 270篇 |
1998年 | 229篇 |
1997年 | 216篇 |
1996年 | 183篇 |
1995年 | 153篇 |
1994年 | 128篇 |
1993年 | 102篇 |
1992年 | 96篇 |
1991年 | 61篇 |
1990年 | 37篇 |
1989年 | 39篇 |
1988年 | 24篇 |
1987年 | 18篇 |
1986年 | 17篇 |
1985年 | 19篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1966年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
简要介绍了鞍钢现有人造富矿生产能力,分析了鞍钢生产1600万t/a生铁所需要的炉料数量、品种和质量,并提出了解决炉料缺口的方法和措施。 相似文献
22.
23.
24.
The effect of the charge fluctuation of dust particles on ion acoustic wave (IAW) excited through ionization instability was investigated. The hydrodynamic equations and linear time-dependent perturbation theory served as the starting point of theory, by which the dispersion relation and growth rate of the IAW were given. By comparing the results with the case of constant dust charges, it was found that the charge fluctuation of dust particles reduces the instability of the wave mode. 相似文献
25.
Osmotic pressure measurements were satisfactorily used to compute the effective charge of poly(acrylic) acid (PAA) at different pHs and with different monovalent and divalent counterions. This experimental method is sensitive to the osmotically active species (polymer and counterions). After correction for the polymer contribution to the total osmotic pressure (solvency and excluded volume), the remaining pressure can be attributed to the polyelectrolyte counterions and processed with Donnan and equation of state in order to compute the effective charge number per polymeric chain (Zeff). The behavior of Zeff against the chain concentration and pH was investigated after neutralization of PAA with LiOH, NaOH, and TMAOH. The results clearly indicate that the nature of the monovalent counterion has no effect on Zeff leading to the conclusion that the interaction between monovalent counterions and the acrylate functionality is purely electrostatic in agreement with conductimetric and potentiometric results reported in the literature. The behavior of Zeff against the degree of ionization of the polymer and its concentration is also in good agreement with the theoretical expectations of the theory of ionic condensation. Osmotic measurements were also used in order to understand the influence of divalent cations (Mg2+, Ca2+, Ba2+) on Zeff of the sodium salt of PAA at pH 9 and at different divalent/acrylate molar ratio. All the divalent cations depress Zeff each of one at different degrees, confirming a specific divalent/polymer interaction. The energy of hydration of cations can explain most of the observed results with divalents. 相似文献
26.
通过对某型杀伤枪榴弹引信所发生的三次弹道炸的原因进行分析,提出用延期索替代延期药盘,并对有关机构进行再设计的对策。 相似文献
27.
28.
V. A. Zheligovsky 《Journal of scientific computing》1993,8(1):41-68
The article discusses computational aspects of the kinematic problem of magnetic field generation by a Beltrami flow in a sphere. Galerkin's method is applied with a functional basis consisting of Laplace operator eigenfunctions. Dominant eigenvalues of the magnetic induction operator and associated magnetic eigenmodes are obtained numerically for a certain Beltrami flow for magnetic Reynolds numbers up to 100. The eigenvalue problem is solved by a highly optimized iterative procedure, which is quite general and can be applied to numerical treatment of arbitrary linear stability problems. 相似文献
29.
Dynamic web sites commonly return information in the form of lists and tables. Although hand crafting an extraction program for a specific template is time-consuming but straightforward, it is desirable to automatically generate template extraction programs from examples of lists and tables in html documents. Supervised approaches have been shown to achieve high accuracy, but they require manual labelling of training examples, which is also time consuming. Fully unsupervised approaches, which extract rows and columns by detecting regularities in the data, cannot provide sufficient accuracy for practical domains. We describe a novel technique, Post-supervised Learning, which exploits unsupervised learning to avoid the need for training examples, while minimally involving the user to achieve high accuracy. We have developed unsupervised algorithms to extract the number of rows and adopted a dynamic programming algorithm for extracting columns. Our method achieves high performance with minimal user input compared to fully supervised techniques. 相似文献
30.
磁性研磨是一种利用磁场中的磁性磨料,对具有相对运动的工件表面进行光整加工的新技术。选择铝、镍、钴磁粉作为磁性磨料时,对奥氏体不锈钢精密薄壁件外表面具有良好的研磨作用。 相似文献