全文获取类型
收费全文 | 18516篇 |
免费 | 1676篇 |
国内免费 | 966篇 |
专业分类
电工技术 | 2620篇 |
综合类 | 1869篇 |
化学工业 | 1115篇 |
金属工艺 | 345篇 |
机械仪表 | 733篇 |
建筑科学 | 3903篇 |
矿业工程 | 719篇 |
能源动力 | 556篇 |
轻工业 | 449篇 |
水利工程 | 1103篇 |
石油天然气 | 867篇 |
武器工业 | 167篇 |
无线电 | 1881篇 |
一般工业技术 | 1360篇 |
冶金工业 | 439篇 |
原子能技术 | 233篇 |
自动化技术 | 2799篇 |
出版年
2024年 | 58篇 |
2023年 | 147篇 |
2022年 | 341篇 |
2021年 | 393篇 |
2020年 | 491篇 |
2019年 | 382篇 |
2018年 | 380篇 |
2017年 | 501篇 |
2016年 | 562篇 |
2015年 | 640篇 |
2014年 | 1485篇 |
2013年 | 1163篇 |
2012年 | 1589篇 |
2011年 | 1624篇 |
2010年 | 1285篇 |
2009年 | 1274篇 |
2008年 | 1128篇 |
2007年 | 1343篇 |
2006年 | 1114篇 |
2005年 | 910篇 |
2004年 | 754篇 |
2003年 | 703篇 |
2002年 | 588篇 |
2001年 | 479篇 |
2000年 | 396篇 |
1999年 | 272篇 |
1998年 | 213篇 |
1997年 | 167篇 |
1996年 | 151篇 |
1995年 | 135篇 |
1994年 | 102篇 |
1993年 | 88篇 |
1992年 | 67篇 |
1991年 | 40篇 |
1990年 | 34篇 |
1989年 | 41篇 |
1988年 | 30篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 2篇 |
1964年 | 2篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
91.
主要介绍系统防雷技术的具体防护方法。包括电源系统、UPS电源系统、终端设备电源、通讯网络系统、电话线及专线、局域网线路、卫星接收天馈线的防护以及接地保护系统。 相似文献
92.
J. Schanda 《Color research and application》2007,32(3):233-235
This is a comment to the editorial by J. Hutchings on “Talking about Color… and Ethics.” © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 233–235, 2007 相似文献
93.
94.
O. V. Konstantinova A. V. Kuz’mov V. V. Skorokhod M. B. Shtern 《Powder Metallurgy and Metal Ceramics》2007,46(1-2):25-31
A theoretical method for determining the percolation limit and effective conductivity of composites based on polydisperse
mixtures of insulator and conductor powders is proposed. The effect of the particle size ratio between the insulator and conductor
on the percolation limit and effective conductivity is studied. Numerical simulation of the microstructure, effective properties,
and percolation limit in composites is discussed.
__________
Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 1–2(453), pp. 31–40, 2007. 相似文献
95.
96.
97.
The efficiency characteristics of multicast key distribution schemes based on (v, b, r, λ)-designs are investigated. The stability
and connectivity of such designs are estimated. These estimates generalize and enhance the well-known estimates for the efficiency
characteristics of multicast key distribution schemes based on incomplete block designs.
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 100–111, May–June 2007. 相似文献
98.
采用精确的有限元非线性分析方法对小高跨比单层单跨实腹门式刚架的平面内弹性整体稳定性进行了大量的参数分析,指出在梁上均布荷载作用下,当柱梁高跨比小于某一数值时,一般不发生传统理论所认为的反对称失稳模式,而是以对称失稳模式为主。给出了修正的柱计算长度系数,并与规范给出的数值进行了对比,认为这种对称失稳模式更不利于门式刚架的整体稳定,应该引起足够的重视。 相似文献
99.
Edoardo Ballico Claudio Fontanari 《Applicable Algebra in Engineering, Communication and Computing》2006,17(2):135-139
Here we apply the so-called Horace method for zero-dimensional schemes to error-correcting codes on complete intersections. In particular, we obtain sharper estimates on the minimum distance. 相似文献
100.
The mechanisms governing the solubilizing interactions between zwitterionic/anionic mixed surfactant systems at different
molar fractions of the zwitterionic surfactant (Xzwitter) and neutral or electrically charged unilamellar liposomes were investigated. The mixed systems were formed by N-dodecyl-N,N-dimethylbetaine
and sodium dodecyl sulfate in the presence of piperazine-1,4-bis-(2-ethanesulfonic acid) buffer at pH 7.20. Unilamellar liposomes formed by egg phosphatidylcholine, in some cases together
with stearylamine or phosphatidic acid, were used. Solubilization was detected as a decrease in static light-scattering of
liposomes. Two parameters were regarded as corresponding to the effective surfactant/lipid molar ratios (Re) at which the
surfactant system (i) saturated the liposomes, Resat, and (ii) led to a total solubilization of liposomes, Resol. From these parameters the bilayer/aqueous medium surfactant partition coefficients for the saturation (Ksat) and complete bilayer solubilization (Ksol) were determined. When Xzwitter was 0.40, The Re and K parameters showed a maximum, whereas the critical micellar concentration (CMC) of these systems exhibited
a minimum, regardless of the electrical charge of bilayers. Given that the ability of the surfactant systems to saturate or
solubilize liposomes is inversely related to the Resat and Resol parameters, these capacities appear to be directly correlated with the CMC of the mixed systems. The similarity of both Ksat and Ksol (particularly for Xzwitter=0.2–0.8) suggests that a similar partition equilibrium governs both the saturation and the complete solubilization of bilayers,
the free surfactant concentration (Sa,Sb), remaining almost constant with similar values to the CMC for each mixed system studied. 相似文献