全文获取类型
收费全文 | 793636篇 |
免费 | 106244篇 |
国内免费 | 64132篇 |
学科分类
工业技术 | 964012篇 |
出版年
2024年 | 4701篇 |
2023年 | 12681篇 |
2022年 | 20641篇 |
2021年 | 28040篇 |
2020年 | 25391篇 |
2019年 | 30597篇 |
2018年 | 33993篇 |
2017年 | 36960篇 |
2016年 | 35010篇 |
2015年 | 40647篇 |
2014年 | 46302篇 |
2013年 | 51514篇 |
2012年 | 53612篇 |
2011年 | 54896篇 |
2010年 | 48251篇 |
2009年 | 43487篇 |
2008年 | 41709篇 |
2007年 | 39649篇 |
2006年 | 40301篇 |
2005年 | 35869篇 |
2004年 | 27054篇 |
2003年 | 23393篇 |
2002年 | 21737篇 |
2001年 | 19593篇 |
2000年 | 19726篇 |
1999年 | 21402篇 |
1998年 | 17790篇 |
1997年 | 15103篇 |
1996年 | 14190篇 |
1995年 | 12365篇 |
1994年 | 10247篇 |
1993年 | 7800篇 |
1992年 | 6668篇 |
1991年 | 5049篇 |
1990年 | 3889篇 |
1989年 | 3358篇 |
1988年 | 2715篇 |
1987年 | 1448篇 |
1986年 | 1120篇 |
1985年 | 749篇 |
1984年 | 528篇 |
1983年 | 392篇 |
1982年 | 425篇 |
1981年 | 321篇 |
1980年 | 285篇 |
1979年 | 145篇 |
1976年 | 282篇 |
1975年 | 223篇 |
1972年 | 249篇 |
1960年 | 208篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
101.
无刷同步电机的励磁系统对励磁电流的测量是制约该励磁方式发展的一大障碍。设计了一个射频系统可以用来解决同步电机的励磁电流的测量问题。该系统可以方便地检测到同步电机励磁机的整流二极管的工作状态并且可以动态地显示励磁电流,极大地方便了运行人员做出判断,而且结构简单、方便实用。 相似文献
102.
Ye Wan Jun Tan Guangling Song Chuanwei Yan 《Metallurgical and Materials Transactions A》2006,37(7):2313-2316
The focused ion beam technique was employed to investigate the atmospheric corrosion morphology of AZ91D. It was found that
the α matrix of the alloy was preferentially corroded in the areas adjacent to intermetallic phases. The most interesting
finding was that the corrosion products in corrosion cavities were pelletlike, which has never been reported before. 相似文献
103.
The toughness of 31Mn2SiRE wear-resistance cast steel were increased by means of RE compound modification and high temperature austenitizing. The results show that the microstructures can be refined, needle and network ferrite are eliminated, the dislocation density and the quantity of dislocated martensite are increased remarkably, and the shape and distribution of inclusions are improved by the addition of RE. Therefore, the mechanical properties of the modified steel can be greatly increased, especially the toughness (αK) by 44%, yield strength (σs) by 10%, and elongation (δ5) by 42%. 相似文献
104.
Supported metal catalysts, particularly noble metals supported on SiO2, have attracted considerable attention due to the importance of the silica–metal interface in heterogeneous catalysis and in electronic device fabrication. Several important issues, e.g., the stability of the metal–oxide interface at working temperatures and pressures, are not well-understood. In this review, the present status of our understanding of the metal–silica interface is reviewed. Recent results of model studies in our laboratories on Pd/SiO2/Mo(1 1 2) using LEED, AES and STM are reported. In this work, epitaxial, ultrathin, well-ordered SiO2 films were grown on a Mo(1 1 2) substrate to circumvent complications that frequently arise from the silica–silicon interface present in silica thin films grown on silicon. 相似文献
105.
High-performance and power-efficient CMOS comparators 总被引:1,自引:0,他引:1
Chung-Hsun Huang Jinn-Shyan Wang 《Solid-State Circuits, IEEE Journal of》2003,38(2):254-262
Several design techniques for high-performance and power-efficient CMOS comparators are proposed. First, the comparator is based on the priority-encoding (PE) algorithm, and the dynamic circuit technique developed specifically for the priority encoder can be applied. Second, the PE function and the subsequent logic functions are merged and efficiently realized in the multiple output domino logic (MODL) to result in a shortened logic depth. The circuit in MODL CMOS is also compact and power efficient because few transistors are needed. Third, the multilevel look-ahead technique is used to shorten the path of priority-token propagation. Finally, the circuit is realized with a latch-based two-stage pipelined structure, and the comparison function is partitioned into two parts, with each part executed in each half of the clock cycle in a delay-balanced manner. Post-layout simulation results show that a 64-b comparator designed with the proposed techniques in a 3-V 0.6-/spl mu/m CMOS technology is 16% faster, 50% smaller, and 79% more power efficient as compared with the all-n-transistor comparator, which is the fastest among the conventional comparators. Measurement results of the test chip conform with simulation results and prove the feasibility of the proposed techniques. 相似文献
106.
Popular biorthogonal wavelet filters via a lifting scheme and its application in image compression 总被引:2,自引:0,他引:2
Cheng L. Liang D.L. Zhang Z.H. 《Vision, Image and Signal Processing, IEE Proceedings -》2003,150(4):227-232
A technique using a lifting scheme is presented for constructing compactly supported wavelets whose coefficients are composed of free variables locating in an interval. An efficient approach-based wavelet for image compression is developed by selecting the coefficients of the 9-7 wavelet filter and associated lifting scheme. Furthermore, the rationalised coefficients wavelet filter that can be implemented with simple integer arithmetic is achieved and its characteristic is close to the well known original irrational coefficients 9-7 wavelet filters developed by A. Cohen et al. (Commun. Pure Appl. Maths., vol.45, no.1, p.485-560, 1992). To reduce the computational cost of image coding applications further, an acceleration technique is proposed for the lifting steps. Software and hardware simulations show that the new method has very low complexity, and simultaneously preserves the high quality of the compressed image. 相似文献
107.
大牛地气田为低渗-致密气田,因存在启动压力梯度等因素,修正等时试井曲线按常规方法处理出现异常,无法准确获取气井的产能方程.采用LIT法和异常曲线校正法对气田异常试井资料进行了重新处理,最终获得气井产能方程,为同类气藏产能试井可能出现的异常资料处理解释探索了新的途径. 相似文献
108.
109.
水工混凝土修补技术应用 总被引:1,自引:0,他引:1
针对水工混凝土的老化病害,介绍了不同类型修补材料的特点、性能、适用范围,以及修补技术应用中的一些实例和经验。 相似文献
110.
文章介绍了一种新型的短波跳频通信技术——差分跳频,分析了差分跳频技术区别于常规跳频技术的主要特点。针对按序列检测的信号接收方法,对差分跳频通信系统在AWGN信道下的性能进行了理论分析,同时做出相应的计算机仿真,证实了差分跳频通信技术和按序列检测方法的结合,使通信系统在AWGN信道下的性能得到了比较显著的提升。 相似文献