全文获取类型
收费全文 | 54810篇 |
免费 | 4220篇 |
国内免费 | 2042篇 |
专业分类
电工技术 | 2845篇 |
技术理论 | 5篇 |
综合类 | 3043篇 |
化学工业 | 9460篇 |
金属工艺 | 3309篇 |
机械仪表 | 3276篇 |
建筑科学 | 3900篇 |
矿业工程 | 1787篇 |
能源动力 | 1704篇 |
轻工业 | 3818篇 |
水利工程 | 911篇 |
石油天然气 | 3888篇 |
武器工业 | 397篇 |
无线电 | 5899篇 |
一般工业技术 | 6562篇 |
冶金工业 | 3086篇 |
原子能技术 | 673篇 |
自动化技术 | 6509篇 |
出版年
2024年 | 250篇 |
2023年 | 906篇 |
2022年 | 1653篇 |
2021年 | 2370篇 |
2020年 | 1721篇 |
2019年 | 1480篇 |
2018年 | 1681篇 |
2017年 | 1818篇 |
2016年 | 1627篇 |
2015年 | 2128篇 |
2014年 | 2741篇 |
2013年 | 3169篇 |
2012年 | 3369篇 |
2011年 | 3683篇 |
2010年 | 3256篇 |
2009年 | 2917篇 |
2008年 | 2868篇 |
2007年 | 2784篇 |
2006年 | 2950篇 |
2005年 | 2524篇 |
2004年 | 1584篇 |
2003年 | 1382篇 |
2002年 | 1295篇 |
2001年 | 1009篇 |
2000年 | 1222篇 |
1999年 | 1511篇 |
1998年 | 1206篇 |
1997年 | 1035篇 |
1996年 | 1031篇 |
1995年 | 907篇 |
1994年 | 718篇 |
1993年 | 473篇 |
1992年 | 376篇 |
1991年 | 303篇 |
1990年 | 246篇 |
1989年 | 198篇 |
1988年 | 177篇 |
1987年 | 111篇 |
1986年 | 97篇 |
1985年 | 63篇 |
1984年 | 58篇 |
1983年 | 39篇 |
1982年 | 32篇 |
1981年 | 30篇 |
1980年 | 17篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 14篇 |
1975年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
43.
氪气和氙气的制备与应用 总被引:1,自引:0,他引:1
详细介绍了氪气、氙气的性质与应用,阐述了其制备的方法与特点,介绍了武钢氧气公司氪气、氙气生产的技术和产量等情况。 相似文献
44.
BaXO4 (X = Mo, W) nanobelts and a variety of hierarchical superstructures assembled from the nanobelts have been synthesized in a catanionic reverse‐micelle system. The effects of various factors, such as the mixing ratio (r) between the anionic and cationic surfactants, the temperature, and the presence of polymeric additives, on the formation of the nanobelts and their hierarchical assembly have been examined in detail. In particular, r has been shown to be powerful in modulating the formation and assembly of the BaMoO4 and BaWO4 nanobelts. Architectural control of the penniform nanobelt superstructures has been readily achieved by changing the experimental parameters. A plausible two‐stage growth mechanism has been proposed for the formation of penniform BaXO4 nanobelt superstructures in catanionic reverse micelles. 相似文献
45.
S. V. Prikhodko Y. Ma A. J. Ardell D. G. Isaak J. D. Carnes S. Moser 《Metallurgical and Materials Transactions A》2003,34(9):1863-1868
The adiabatic elastic stiffness constants C
ij of Ni-Si single-crystal solid-solution alloys of two slightly different compositions, 10.78 and 11.17 at. pct Si, were measured
over the temperature range from 20 °C to 900 °C using the rectangular parallelepiped resonance method. The isotropic elastic
constants of the polycrystalline ordered intermetallic compound Ni3Si containing 23 at. pct Si were also measured over this temperature range. Values of the C
ij for Ni3Si were estimated from the data on the polycrystalline alloy, as well as from published data in the literature on isomorphous
ternary ordered intermetallic compounds containing different amounts of Si. Using measured values and previously published
data, the stiffness constants of Ni3Ti were estimated; these are the only available data on this alloy. The estimated single-crystal elastic constants of Ni3Si, as well as the experimentally measured bulk modulus, are considerably smaller than published values calculated from first-principles
methods. The same is true for the C
ij of Ni3Ti, but the discrepancies are smaller. 相似文献
46.
煤基链篦机-回转窑一步法直接还原设备改造及技术操作要点 总被引:2,自引:0,他引:2
本文主要论述了煤基链篦机-回转窑一步法直接还原关键设备改造及有关技术操作要点,并提出了进一步提高产量,稳定操作,延长作业周期,降低生产成本的技术改造方案。 相似文献
47.
质子交换铌酸锂波导MMI光功分器 总被引:1,自引:1,他引:0
利用三维非旁轴近似光束传输法对退火质子交换铌酸锂渐变折射率分布波导中的自镜像效应进行分析与模拟 .在此基础上 ,利用退火质子交换技术在 X切 Y传铌酸锂衬底上进一步制作了 1× 8MMI光功分器 .测试表明器件实现了 1路分成 8路的光功分功能 . 相似文献
48.
针对TPS/TDC30 0 0系统串口通讯方式、机理进行了一般性的介绍 ,对规划与应用中常见的的问题 ,根据实际工程应用经验提出了解决方案。 相似文献
49.
采用二甲苯为溶剂,将不同乙烯含量(5% ̄15%质量)的抗冲聚丙烯用特定程序进行分级,将各样品分为室温下可溶于甲苯和不可溶于甲苯的两部分。使用^13C-NMR方法和FT-IR方法对各组分进行表征,明确了乙烯链段在聚丙烯链上的分布,并在此基础上提出了产生这种链结构的聚合工艺的特点。 相似文献
50.
AK Ma?ek O Rowiński T Ostrowski L Hilgertner M Januszewicz M Szostek 《Canadian Metallurgical Quarterly》1995,50(40-44):19-22
Subclavian steal syndrome (SSS) appears when the origin of the subclavian artery (SA) is occluded or stenosed. Introduction of transcranial Doppler sonography (TCD) provided an opportunity to evaluate parameters of the blood flow in the vertebral (VA) and basilar artery (BA). Measurements of blood flow velocities performed at rest and after the brachial hyperemia test allow one to classify hemodynamic types of SSS. The aim of the study was to categorize types of steal and to compare the differences of flow patterns before and after percutaneous transluminal SA balloon angioplasty (SA-PTA). Fourty-eight patients with angiographically confirmed SSS (aged from 27 to 68 years, mean 53; 2/1 f/m ratio) were examined with 2 MHz range-gated, pulsed transcranial Doppler device (TC 2-64B EME). Both VA and BA were evaluated by the transoccipital approach at rest and during the brachial hyperemia. In 5 cases (10.4%) permanent reversal blood flow in the BA was observed (complete basilar steal). In flow in the BA blood flow was in the normal direction at rest and altered (reversed or decreased) when induced with brachial hyperemia test (transient basilar steal). In the next 14 patients (29.2%) permanently reversed VA blood flow was observed with only a slight or no alterations of the BA flow after the hyperemia test (complete vertebral steal). In the last 19 cases (39.6%) alterations of the VA blood flow without changes in BA flow were observed (latent vertebral steal). Between 1991 and 1994 twenty seven symptomatic patients with different hemodynamic types of SSS were treated with SA-PTA. TCD evaluation of VA's and BA using the hyperemia test was performed before, 3 to 7 days and 3 months after morphologically and hemodynamically successful subclavian artery balloon PTA. Normal results of vertebrobasilar examinations were obtained in 26 cases after this procedure. In one case the latent vertebral steal was detected. The 28 months mean follow-up revealed no significant changes in TCD flow patterns recorded from VA's and BA. After collecting data of about 60 patients with SSS we examined with TCD we conclude that: in patients with a hemodynamically significant SA stenosis the presence of reversed ipsilateral VA blood flow (a radiologic steal) its not a good determinant of either the presence or type of presenting symptoms and after successful PTA or recanalisation and PTA of SA in almost all cases we examined close to normal TCD recordings in BA and VA. 相似文献