全文获取类型
收费全文 | 41329篇 |
免费 | 4479篇 |
国内免费 | 2547篇 |
专业分类
电工技术 | 1719篇 |
综合类 | 4267篇 |
化学工业 | 7270篇 |
金属工艺 | 4528篇 |
机械仪表 | 1959篇 |
建筑科学 | 9430篇 |
矿业工程 | 1991篇 |
能源动力 | 776篇 |
轻工业 | 2151篇 |
水利工程 | 1711篇 |
石油天然气 | 1364篇 |
武器工业 | 325篇 |
无线电 | 1382篇 |
一般工业技术 | 5333篇 |
冶金工业 | 2847篇 |
原子能技术 | 298篇 |
自动化技术 | 1004篇 |
出版年
2024年 | 194篇 |
2023年 | 633篇 |
2022年 | 1232篇 |
2021年 | 1501篇 |
2020年 | 1409篇 |
2019年 | 1232篇 |
2018年 | 1287篇 |
2017年 | 1677篇 |
2016年 | 1707篇 |
2015年 | 1715篇 |
2014年 | 2523篇 |
2013年 | 2812篇 |
2012年 | 3014篇 |
2011年 | 3051篇 |
2010年 | 2258篇 |
2009年 | 2291篇 |
2008年 | 2121篇 |
2007年 | 2554篇 |
2006年 | 2332篇 |
2005年 | 2025篇 |
2004年 | 1712篇 |
2003年 | 1447篇 |
2002年 | 1263篇 |
2001年 | 1103篇 |
2000年 | 943篇 |
1999年 | 838篇 |
1998年 | 650篇 |
1997年 | 535篇 |
1996年 | 458篇 |
1995年 | 386篇 |
1994年 | 313篇 |
1993年 | 268篇 |
1992年 | 211篇 |
1991年 | 136篇 |
1990年 | 132篇 |
1989年 | 115篇 |
1988年 | 63篇 |
1987年 | 58篇 |
1986年 | 25篇 |
1985年 | 20篇 |
1984年 | 19篇 |
1983年 | 14篇 |
1982年 | 18篇 |
1981年 | 6篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1964年 | 4篇 |
1963年 | 2篇 |
1961年 | 2篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Evaluating Liquefaction Strength of Partially Saturated Sand 总被引:1,自引:0,他引:1
A method is presented for evaluating the liquefaction strength of partially saturated sand using the compression wave velocity (P-wave velocity), a new indicator of saturation. Based on laboratory test results, an empirical correlation that relates the liquefaction strength with the pore pressure coefficient B is firstly proposed. The strength is defined as the cyclic stress ratio required to cause liquefaction at a specified number of cycles. With the aid of a theoretical relation between B and the P-wave velocity, an explicit correlation of more interest is then established between the liquefaction strength of sand and its P-wave velocity. A comparison of the predictions using this explicit correlation with laboratory measurements shows a satisfactory agreement. The significance of this method lies in that it makes it possible to evaluate the liquefaction strength of sand as affected by saturation through the measurement of P-wave velocity, which can be made not only in the laboratory but particularly in the field. 相似文献
62.
一种高并行度的H.264帧内预测器的VLSI设计 总被引:3,自引:2,他引:1
分析了帧内预测的17种模式,对于每个4×4大小块的16个像素点的不同模式的预测公式之间的相同运算,采用数字强度缩减的方法去除计算的冗余,提出了一种高并行度的帧内预测器,可以每个时钟周期处理16个像素点的预测值。基于SMIC0.18μm工艺,用verilog对该设计进行了VLSI实现,综合后的电路的关键路径最大时延为10ns,电路规模不超过1.4万门,数据吞吐率可以达到1600Msamples/s。从实现结果来看,与采用可重构方法的设计相比,该设计在相同的并行度下减小了电路面积,简化了控制逻辑。 相似文献
63.
Addressing the potential for drop impact failure of Pb-free interconnects, the shear ductility after extensive aging of Sn-Ag-Cu
(SAC) solders has been improved radically by Co or Fe modifications. Several other SAC+X candidates (X=Mn, Ni, Ge, Ti, Si,
Cr, and Zn) now have been tested. Solder joint microstructures and shear strength results show that new SAC+X alloys also
suppress void formation and coalescence at the Cu (substrate)/Cu3Sn interface (and embrittlement) after aging at 150°C for up to 1,000 h. Microprobe measurements of 1,000 h aged samples suggest
that Cu substitution by X is usually accentuated in the intermetallic layers, consistent with X=Co and Fe results. 相似文献
64.
The authors study residual stresses in and cyclic strength of shaft with overlapping zones formed during roller burnishing.
The most significant decrease in fatigue strength is shown to occur in the presence of an overlapping zone with the areas
arising due to a lowered roller burnishing pressure in the second pass.
__________
Translated from Problemy Prochnosti, No. 3, pp. 144–148, May–June, 2006. 相似文献
65.
66.
Nanoadhesives of epoxy resin are synthesized and evaluated. They are organically modified by multiwalled carbon nanotubes (MWCNT) (1% by weight) as reinforcement. Tensile tests are conducted on multiple identical unnotched and notched specimens to evaluate the overloading and fracture behavior of the nanoadhesives and are compared with the neat epoxy resin. In comparison with the neat epoxy, it is found that the 1% MWCNT reinforcement increased the ultimate and residual strength by about 29% and 56%, respectively. In comparison with the neat resin, there is a 265% increase in the fracture toughness of the MWCNT adhesive. Fracture surface analysis revealed the various mechanisms by which the MWCNT adhesives acquire their superior strength and toughness in comparison with the neat resin. 相似文献
67.
68.
69.
70.