全文获取类型
收费全文 | 628886篇 |
免费 | 98794篇 |
国内免费 | 61855篇 |
专业分类
电工技术 | 54749篇 |
技术理论 | 58篇 |
综合类 | 50212篇 |
化学工业 | 94053篇 |
金属工艺 | 47515篇 |
机械仪表 | 36031篇 |
建筑科学 | 48277篇 |
矿业工程 | 27159篇 |
能源动力 | 21268篇 |
轻工业 | 48561篇 |
水利工程 | 15840篇 |
石油天然气 | 38486篇 |
武器工业 | 7674篇 |
无线电 | 78566篇 |
一般工业技术 | 78539篇 |
冶金工业 | 29218篇 |
原子能技术 | 5951篇 |
自动化技术 | 107378篇 |
出版年
2024年 | 4285篇 |
2023年 | 10853篇 |
2022年 | 17288篇 |
2021年 | 23059篇 |
2020年 | 21643篇 |
2019年 | 27430篇 |
2018年 | 30295篇 |
2017年 | 33069篇 |
2016年 | 31385篇 |
2015年 | 35460篇 |
2014年 | 39514篇 |
2013年 | 43451篇 |
2012年 | 45361篇 |
2011年 | 44804篇 |
2010年 | 40043篇 |
2009年 | 35773篇 |
2008年 | 33718篇 |
2007年 | 32041篇 |
2006年 | 31085篇 |
2005年 | 26828篇 |
2004年 | 21609篇 |
2003年 | 18471篇 |
2002年 | 17164篇 |
2001年 | 15544篇 |
2000年 | 14850篇 |
1999年 | 15291篇 |
1998年 | 12657篇 |
1997年 | 10775篇 |
1996年 | 10167篇 |
1995年 | 9058篇 |
1994年 | 7511篇 |
1993年 | 5841篇 |
1992年 | 5078篇 |
1991年 | 3839篇 |
1990年 | 3022篇 |
1989年 | 2656篇 |
1988年 | 2118篇 |
1987年 | 1039篇 |
1986年 | 831篇 |
1985年 | 546篇 |
1984年 | 391篇 |
1983年 | 300篇 |
1982年 | 349篇 |
1981年 | 290篇 |
1980年 | 241篇 |
1979年 | 143篇 |
1976年 | 290篇 |
1975年 | 231篇 |
1972年 | 250篇 |
1960年 | 210篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
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
13.
Introduction
The IEC central office informed in 7/543/AC that the secretariat of TC 7 would be taken over by the Chinese National Committee on January 10, 2003 and affirmed subsequently in 7/544/AC that the secretariat of TC 7 has been taken over by the Chinese National Committee which appointing secretary in Shanghai Electric Cable Research Institute as no objection has been raised by the Standardization Management Board members. It's the first IEC secretariat that assumed by China, with great significance, just as commented by the media that the commitment indicate undoubtedly China is to play a much more active and important role in the world especially after its entry into world trade organization as well as the trend of global economic integration. 相似文献
14.
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
15.
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
16.
17.
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
18.
19.
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
20.
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