全文获取类型
收费全文 | 6948篇 |
免费 | 894篇 |
国内免费 | 336篇 |
专业分类
电工技术 | 221篇 |
技术理论 | 1篇 |
综合类 | 318篇 |
化学工业 | 695篇 |
金属工艺 | 118篇 |
机械仪表 | 246篇 |
建筑科学 | 262篇 |
矿业工程 | 49篇 |
能源动力 | 679篇 |
轻工业 | 290篇 |
水利工程 | 154篇 |
石油天然气 | 101篇 |
武器工业 | 53篇 |
无线电 | 738篇 |
一般工业技术 | 444篇 |
冶金工业 | 112篇 |
原子能技术 | 456篇 |
自动化技术 | 3241篇 |
出版年
2024年 | 12篇 |
2023年 | 49篇 |
2022年 | 129篇 |
2021年 | 136篇 |
2020年 | 111篇 |
2019年 | 118篇 |
2018年 | 154篇 |
2017年 | 281篇 |
2016年 | 314篇 |
2015年 | 328篇 |
2014年 | 439篇 |
2013年 | 392篇 |
2012年 | 455篇 |
2011年 | 517篇 |
2010年 | 438篇 |
2009年 | 459篇 |
2008年 | 466篇 |
2007年 | 401篇 |
2006年 | 462篇 |
2005年 | 475篇 |
2004年 | 433篇 |
2003年 | 404篇 |
2002年 | 277篇 |
2001年 | 157篇 |
2000年 | 126篇 |
1999年 | 106篇 |
1998年 | 78篇 |
1997年 | 77篇 |
1996年 | 54篇 |
1995年 | 47篇 |
1994年 | 52篇 |
1993年 | 44篇 |
1992年 | 32篇 |
1991年 | 33篇 |
1990年 | 15篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1959年 | 2篇 |
排序方式: 共有8178条查询结果,搜索用时 0 毫秒
11.
12.
Inverse surface design problems from light transport behavior specification usually represent extremely complex and costly processes, but their importance is well known. In particular, they are very interesting for lighting and luminaire design, in which it is usually difficult to test design decisions on a physical model in order to avoid costly mistakes. In this survey, we present the main ideas behind these kinds of problems, characterize them, and summarize existing work in the area, revealing problems that remain open and possible areas of further research. 相似文献
13.
Vitrification of TRISO-coated gas reactor fuel particles was achieved via two methods: glass melting and sintering. Inert TRISO-coated fuel particles and a borosilicate glass were used. With glass melting at 1200-1300 °C floatation and decomposition of carbon and silicon carbide occurred. Thermal pre-treatment of the particles for oxidation of pyrocarbon did not improve the coating properties of the glass. During cooling most of the particles floated and sorbed on the crucible or mold walls. The sintered glass at 700 °C showed better coating properties of the TRISO-coated fuel particles despite higher porosity compared to glass made by melting. Aqueous leaching properties of glass with particles are similar regardless the mode of fabrication, indicating the good chemical durability of the sintered glass. Sintered glasses may constitute a good technique for TRISO-coated fuel particles immobilization for an eventual deep geological disposal. 相似文献
14.
The relationship between hydrogen concentration precipitated as hydride particles and ultrasonic parameters, such as velocity and attenuation, was examined in Zircaloy-4 samples for potential applications in the Non-Destructive Test Field. Different amounts of hydrogen (up to 517 ppm) were introduced in the samples by gaseous charging. Ultrasonic attenuation measurements were performed with compressive waves at frequencies of 10 and 30 MHz, and propagation velocity measurements were performed at 10 MHz. Ultrasonic velocity showed an approximately linear increase with hydrogen concentration and it could be used as an assessment parameter when the hydrogen level is high enough. Attenuation versus hydrogen concentration has been fitted by a logarithmic equation at 10 MHz. At 30 MHz a fluctuating behavior of the attenuation prevented measurement of the hydrogen concentration. 相似文献
15.
An experiment to remove re-deposited layers and to release hydrogen using a glow discharge in oxygen (O-GDC) has been performed in the HT-7 superconducting tokamak. In the absence of magnetic fields, the O-GDC wall conditioning had produced rapid, controlled co-deposit removal. Average removal rates, 5.2 × 1022 H-atoms/h, 5.65 × 1021 D-atoms/h and 5.53 × 1022 C-atoms/h, respectively, were obtained during 145 min O-GDC experiment in the pressure range 0.5-1.5 Pa. The corresponding removal rate of co-deposited films was ∼1.19 μm/day (26.5 g/day for carbon) based on an area of 12 m2. Compared to thermo-oxidation and O-ICR experiment, high pressure O-GDC wall conditioning promoted the oxidation and improved the C and D atoms removal. In the O-GDC experiment, the removal rates of H-atoms and D-atoms as H2O, HDO and D2O were higher than that of H2 and D2 by factors of about 20 and 50, respectively. During the 145 min O-GDC experiment, about 14.5% O-atoms were converted into carbon oxides and hydroxides, and about 5.37 × 1022 O-atoms were adsorbed on the walls corresponding to a coverage of 4.5 × 1021 O/m2 on an wall area of 12 m2. In a 100 min helium glow discharge (He-GDC) following the O-GDC experiment, 1.53 × 1022 O-atoms, about 28.5% oxygen retained on the walls, were removed. The removal rate of H-atoms in He-GDC cleaning after O-GDC experiment was lower than that in He-GDC cleaning before O-GDC experiment, which indicates that the O-GDC wall conditioning had effectively reduced hydrogen retention on the walls. 相似文献
16.
有限转角无刷力矩电动机位置伺服系统的电流控制 总被引:3,自引:0,他引:3
提出了有限转角无刷力矩电动机 (LABLTM)位置伺服系统电流控制策略 ,给出了实施方法 ,进行了开关管频率特性的分析。该方法可实现在不同误差时自动调节电动机电流 ,进而控制输出转矩 ,并具有稳态精度高、动态响应快等特点。 相似文献
17.
M. Hara Y. Hatano T. Abe K. Watanabe T. Naitoh S. Ikeno Y. Honda 《Journal of Nuclear Materials》2003,320(3):265-271
To improve the durability of hydrogen storage materials against surface poisoning by impurity gases, effectiveness of Pd-coating layer prepared by using a Barrel-Sputtering System was examined for ZrNi powder. The effectiveness of Pd-coating was evaluated by activation temperature, at which Pd/ZrNi poisoned by air could be activated to absorb hydrogen. Characterization of Pd-coated ZrNi (denoted as Pd/ZrNi) by scanning electron microscopy, electron probe microanalysis and X-ray diffraction showed that a uniform Pd-coating layer was formed with the barrel-sputtering system. It was found that the poisoned Pd/ZrNi sample could be activated even at 423 K to absorb hydrogen at room temperature. This exhibits remarkable contrast to bare ZrNi, which could be only activated appreciably above 1073 K. It is concluded that the Pd-coating by barrel sputtering is quite effective to avoid the effect of surface poisoning of powdery hydrogen storage materials. However, the activation at excessively high temperature resulted in the loss of high activity to absorb hydrogen. It was concluded that this phenomenon was associated with reactions between Pd and ZrNi to form PdZr and other byproducts. 相似文献
18.
BOOTSTRAP CONTROL CHARTS 总被引:1,自引:0,他引:1
19.
多传感器数据融合技术已在军事领域受到广泛重视,并逐步走向实际应用,本文简要介绍它的一般组成、特点以及在军事C^3I系统应用中的主要功效。 相似文献
20.
定量描述了实际生产过程中三辊斜轧穿孔所产生的钢管壁厚极差和波浪形内螺纹,初步探讨了三辊轧管机对钢管壁厚极差和波浪形内螺纹的影响。 相似文献