全文获取类型
收费全文 | 88592篇 |
免费 | 8878篇 |
国内免费 | 4710篇 |
专业分类
电工技术 | 5855篇 |
技术理论 | 2篇 |
综合类 | 6435篇 |
化学工业 | 13649篇 |
金属工艺 | 5186篇 |
机械仪表 | 6095篇 |
建筑科学 | 7329篇 |
矿业工程 | 2829篇 |
能源动力 | 2516篇 |
轻工业 | 6371篇 |
水利工程 | 1955篇 |
石油天然气 | 4623篇 |
武器工业 | 874篇 |
无线电 | 10871篇 |
一般工业技术 | 10088篇 |
冶金工业 | 3896篇 |
原子能技术 | 1076篇 |
自动化技术 | 12530篇 |
出版年
2024年 | 461篇 |
2023年 | 1739篇 |
2022年 | 3350篇 |
2021年 | 4533篇 |
2020年 | 3466篇 |
2019年 | 2778篇 |
2018年 | 2885篇 |
2017年 | 3312篇 |
2016年 | 2960篇 |
2015年 | 4310篇 |
2014年 | 5175篇 |
2013年 | 6055篇 |
2012年 | 6395篇 |
2011年 | 6852篇 |
2010年 | 5933篇 |
2009年 | 5767篇 |
2008年 | 5643篇 |
2007年 | 5017篇 |
2006年 | 4659篇 |
2005年 | 3791篇 |
2004年 | 2498篇 |
2003年 | 1930篇 |
2002年 | 1827篇 |
2001年 | 1589篇 |
2000年 | 1410篇 |
1999年 | 1438篇 |
1998年 | 1151篇 |
1997年 | 954篇 |
1996年 | 886篇 |
1995年 | 776篇 |
1994年 | 635篇 |
1993年 | 464篇 |
1992年 | 333篇 |
1991年 | 293篇 |
1990年 | 202篇 |
1989年 | 167篇 |
1988年 | 127篇 |
1987年 | 88篇 |
1986年 | 80篇 |
1985年 | 40篇 |
1984年 | 32篇 |
1983年 | 33篇 |
1982年 | 29篇 |
1981年 | 26篇 |
1980年 | 28篇 |
1979年 | 13篇 |
1976年 | 6篇 |
1972年 | 4篇 |
1959年 | 6篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Yang C.W. Fang Y.K. Lin C.S. Tsair Y.S. Chen S.M. Wang W.D. Wang M.F. Cheng J.Y. Chen C.H. Yao L.G. Chen S.C. Liang M.S. 《Electronics letters》2003,39(21):1499-1501
A novel technique to form high-K dielectric of HfSiON by doping base oxide with Hf and nitridation with NH/sub 3/, sequentially, is proposed. The HfSiON gate dielectric demonstrates excellent device performances such as only 10% degradation of saturation drain current and almost 45 times of magnitude reduction in gate leakage compared with conventional SiO/sub 2/ gate at the approximately same equivalent oxide thickness. Additionally, negligible flatband voltage shift is achieved with this technique. Time-dependent dielectric breakdown tests indicate that the lifetime of HfSiON is longer than 10 years at V/sub dd/=2 V. 相似文献
12.
13.
心电地图仪中工频干扰的一种滤除方法 总被引:1,自引:0,他引:1
在心电地图仪中记录到的体表心电信号往往由于电磁的影响而引进工频干扰.基于体表心电信号中工频干扰的特点,作者提出了一种滤除工频干扰的方法,即就单独—胸导联信号通过提高频谱的分辨率来估计工频干扰的频率;基于最小均方误差准则来估计各导联信号中工频干扰的幅度和相位。文中还给出了该算法的流程图和滤波性能分析。模拟结果表明了该算法的有效性。应用该算法对心电地图仪中的工频干扰进行对消,取得了满意的结果。 相似文献
14.
The purpose of this study is to examine the interface between financial strain, informal received economic support, informal anticipated financial support, and psychological distress in later life. Data provided by a large probability sample of older adults in the People's Republic of China reveal that the relationship between financial difficulty and psychological distress is stronger for older adults who receive more economic assistance. However, the results involving anticipated support are in the opposite direction. More specifically, the association between financial problems and psychological distress is lower for older adults who believe that others stand ready to help in the future should the need arise. A detailed theoretical rationale is developed to explain these results. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
15.
Two new versions of component relevancy for multistate structure functions are introduced. They are compared with some existing component-relevance conditions and their general properties are investigated. Based on the two relevance conditions, two component-importance measures for multistate systems are defined; they are most appropriate for comparing components when a certain type of system improvement is considered. Series and parallel structures are characterized within the L -superadditive and L -subadditive structure functions by imposing the two new relevance conditions 相似文献
16.
Liang Y.C. Wenjiang Zeng Pick Hong Ong Zhaoxia Gao Jun Cai Balasubramanian N. 《Electron Device Letters, IEEE》2002,23(12):700-703
In this letter, a concise process technology is proposed for the first time to enable the fabrication of good quality three-dimensional (3-D) suspended radio frequency (RF) micro-inductors on bulk silicon, without utilizing the lithography process on sidewall and trench-bottom patterning. Samples were fabricated to demonstrate the applicability of the proposed process technology. 相似文献
17.
分析了WCDMA移动通信网网管系统管理框架,在此基础上提出采用公共对象请求代理体系结构(CORBA)建立网管系统信息模型的优势,给出WCDMA网管系统的信息模型,同时介绍了对象管理组(OMG)接口描述语言(IDL)。 相似文献
18.
Interfacial segregation of Ti in the brazing of diamond grits onto a steel substrate using a Cu-Sn-Ti brazing alloy 总被引:1,自引:0,他引:1
Wen-Chung Li Shun-Tian Lin Cheng Liang 《Metallurgical and Materials Transactions A》2002,33(7):2163-2172
Diamond grits were brazed onto a steel substrate using a prealloyed Cu-10Sn-15Ti (wt pct) brazing alloy at 925 °C and 1050
°C. Due to the relatively high concentration of Ti in the brazing alloy, the braze matrix exhibited a composite structure,
composed of β-(Cu,Sn), a Cu-based solid solution, and various intermetallic compounds with different morphologies. The reaction of Ti with
diamond yielded a continuous TiC layer on the surfaces of the diamond grits. On top of the TiC growth front, an intermetallic
compound, composed of Sn and Ti, nucleated and grew into a randomly interwoven fine lacey structure. An interfacial structure
developed as the interwoven fine lacey phase was semicoherently bonded to the TiC layer, with the Cu-based braze matrix filling
its interstices. The thickness of such a composite layer was increased linearly with the square root of isothermal holding
time at 925 °C, complying with the law of a diffusion-controlled process. However, at 1050 °C, the segregation behavior of
Ti and Sn to the interfaces between the TiC layer and the braze matrix diminished, due to the increased solubility of Ti in
the Cu-based liquid phase. The enhanced dissolution of Ti in the Cu-based liquid phase at 1050 °C also caused the precipitation
of rod-like CuTi with an average diameter of about 0.2 μm during cooling. SnTi3 was the predominant intermetallic compound and existed in three different forms in the braze matrix. It existed as interconnected
grains of large size which either floated to the surface of the braze matrix or grew into faceted grains. It also exhibited
a nail-like structure with a mean diameter of about 1 μm for the rod section and a lamellar structure arising from a eutectic reaction during cooling. 相似文献
19.
Tsu-Hua Ai Jiann-Fuh Chen Tsorng-Juu Liang 《Industrial Electronics, IEEE Transactions on》2002,49(3):595-597
To overcome the problem of unequal switching loss in power switches, in conventional hybrid pulse width modulation (HPWM) full-bridge inverters, a random switching method for HPWM full-bridge inverters is proposed. The proposed method equalizes switching losses of the four switches, while also providing good output performance 相似文献
20.
茅金根 ,梁秀文 ,杨午阳 ,冯有奎 .等偏移距自动初至静校正 .石油地球物理勘探 ,2 0 0 2 ,37(5 ) :4 6 9~ 4 72 本文提出一种自动计算静校正量的新方法。它首先在等偏移距道集内对相邻道的初至波采用高精度相关构建一个关于炮、检时差的超大矩阵方程 ,然后采用优化统计迭代算法求解炮点和检波点的静校正量 ,并用概率分布函数确定精确的炮、检静校正量 ,最后用误差校正函数消除炮、检静校正误差。实际资料处理结果表明 ,本方法自动、省时、精度高。 相似文献