全文获取类型
收费全文 | 4376篇 |
免费 | 620篇 |
国内免费 | 233篇 |
专业分类
电工技术 | 74篇 |
综合类 | 484篇 |
化学工业 | 651篇 |
金属工艺 | 82篇 |
机械仪表 | 258篇 |
建筑科学 | 2101篇 |
矿业工程 | 75篇 |
能源动力 | 29篇 |
轻工业 | 42篇 |
水利工程 | 177篇 |
石油天然气 | 61篇 |
武器工业 | 62篇 |
无线电 | 142篇 |
一般工业技术 | 446篇 |
冶金工业 | 77篇 |
原子能技术 | 8篇 |
自动化技术 | 460篇 |
出版年
2024年 | 67篇 |
2023年 | 175篇 |
2022年 | 267篇 |
2021年 | 228篇 |
2020年 | 217篇 |
2019年 | 137篇 |
2018年 | 147篇 |
2017年 | 164篇 |
2016年 | 179篇 |
2015年 | 232篇 |
2014年 | 373篇 |
2013年 | 261篇 |
2012年 | 332篇 |
2011年 | 338篇 |
2010年 | 227篇 |
2009年 | 266篇 |
2008年 | 233篇 |
2007年 | 297篇 |
2006年 | 255篇 |
2005年 | 212篇 |
2004年 | 102篇 |
2003年 | 120篇 |
2002年 | 111篇 |
2001年 | 70篇 |
2000年 | 50篇 |
1999年 | 40篇 |
1998年 | 32篇 |
1997年 | 19篇 |
1996年 | 27篇 |
1995年 | 6篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有5229条查询结果,搜索用时 15 毫秒
1.
Bahram Rashidi 《International Journal of Circuit Theory and Applications》2020,48(8):1227-1243
In this paper, low-cost and two-cycle hardware structures of the PRINCE lightweight block cipher are presented. In the first structure, we proposed an area-constrained structure, and in the second structure, a high-speed implementation of the PRINCE cipher is presented. The substitution box (S-box) and the inverse of S-box (S-box−1) blocks are the most complex blocks in the PRINCE cipher. These blocks are designed by an efficient structure with low critical path delay. In the low-cost structure, the S-boxes and S-boxes−1 are shared between the round computations and the intermediate step of PRINCE cipher. Therefore, the proposed architecture is implemented based on the lowest number of computation resources. The two-cycle implementation of PRINCE cipher is designed by a processing element (PE), which is a general and reconfigurable element. This structure has a regular form with the minimum number of the control signal. Implementation results of the proposed structures in 180-nm CMOS technology and Virtex-4 and Virtex-6 FPGA families are achieved. The proposed structures, based on the results, have better critical path delay and throughput compared with other's related works. 相似文献
2.
3.
4.
大掺量粉煤灰轻质墙体砌块是以粉煤灰为主要原材料 ,普通硅酸盐水泥为胶凝材料 ,配以各种外加剂 ,经发泡剂发泡 ,在常温、常压条件下养护而成。具有重量轻、导热系数小、抗冻性高以及粉煤灰掺量大、成型方便、工艺简单、投资小、见效快等优点。 相似文献
5.
用电化学方法测定砂浆试件中钢筋的极化电阻,并测定了砂浆的孔隙率,结果发现:砂浆的孔隙率、孔径分布与钢筋极化电阻大小有良好的对应关系。电化学方法能可靠、快速测定砂浆配合比、添加剂对钢筋腐蚀速度的影响。 相似文献
6.
荆江分洪北闸加固工程2号护坦(斜面)混凝土的保温层采用了水泥膨胀珍珠岩砂浆,并对这种材料的保温效果进行了试验研究。试验表明:水泥膨胀珍珠岩砂浆降低最高温差,减小内表温差,缩小表温变幅和防止混凝土表面裂缝效果显著。在北闸2号护坦混凝土表面铺设1万平方米保温层,获得良好效果。 相似文献
7.
8.
Properties of latex blends and its modified cement mortars 总被引:1,自引:0,他引:1
In this paper, the mechanical properties of three latex blends and the mechanical properties and chloride diffusivity of the latex-modified mortars are studied. The relationships between the properties of polymer films formed from latex blends and the properties of the latex blend-modified mortars are illustrated. The test results showed that the modified mortar with the blend of styrene-acrylic ester (SAE) and styrene-butadiene rubber (SBR) showed synergistic effect; especially the flexural strength of the SAE/SBR blend-modified mortars was about 20-40% higher than that of monolatex-modified mortars. However, the vinyl chloride-vinylidene chloride copolymer (PVDC)/SBR and PVDC/SAE blends-modified mortars showed antisynergistic effect. The compressive strength of the modified mortars increased with the increasing of the tensile strength of the latex films, while the flexural strength of the modified mortars did not depend on the tensile strength of the latex films. When PVDC with the mass fraction of 0.2 or SAE copolymer emulsion with mass fraction of 0.4 was blended into SBR latex, the latex blend-modified mortars showed lower chloride diffusivity. The chloride diffusivity of the modified mortars increased approximately linear with the tensile strength of the latex blend films, and decreased with increase of the elongation at rupture of the latex blend films. When the elongation at rupture of the latex blend films increased from 200-300% to more than 800%, the chloride diffusivity of the modified mortars decreased from 10-15×10−12 to 3-4×10−12 m2/s. 相似文献
9.
10.
以云南鸡石一级公路青鱼湾大桥为例,介绍了在软弱地层中施工桥梁钻孔灌注桩遇孔壁开裂漏浆时的处理方法,经试验证明,取得了较好的技术经济效果。 相似文献