全文获取类型
收费全文 | 92644篇 |
免费 | 9875篇 |
国内免费 | 5352篇 |
专业分类
电工技术 | 7366篇 |
技术理论 | 8篇 |
综合类 | 7564篇 |
化学工业 | 14016篇 |
金属工艺 | 5524篇 |
机械仪表 | 6168篇 |
建筑科学 | 7730篇 |
矿业工程 | 3252篇 |
能源动力 | 3023篇 |
轻工业 | 6854篇 |
水利工程 | 2327篇 |
石油天然气 | 4495篇 |
武器工业 | 1183篇 |
无线电 | 10591篇 |
一般工业技术 | 9978篇 |
冶金工业 | 3701篇 |
原子能技术 | 1308篇 |
自动化技术 | 12783篇 |
出版年
2024年 | 258篇 |
2023年 | 1555篇 |
2022年 | 3033篇 |
2021年 | 4449篇 |
2020年 | 3225篇 |
2019年 | 2586篇 |
2018年 | 2889篇 |
2017年 | 3299篇 |
2016年 | 2883篇 |
2015年 | 4219篇 |
2014年 | 5206篇 |
2013年 | 6065篇 |
2012年 | 7073篇 |
2011年 | 7151篇 |
2010年 | 6670篇 |
2009年 | 6424篇 |
2008年 | 6255篇 |
2007年 | 5711篇 |
2006年 | 5393篇 |
2005年 | 4303篇 |
2004年 | 3029篇 |
2003年 | 2338篇 |
2002年 | 2374篇 |
2001年 | 2046篇 |
2000年 | 1795篇 |
1999年 | 1646篇 |
1998年 | 1156篇 |
1997年 | 982篇 |
1996年 | 870篇 |
1995年 | 659篇 |
1994年 | 580篇 |
1993年 | 414篇 |
1992年 | 340篇 |
1991年 | 251篇 |
1990年 | 182篇 |
1989年 | 157篇 |
1988年 | 96篇 |
1987年 | 69篇 |
1986年 | 48篇 |
1985年 | 33篇 |
1984年 | 23篇 |
1983年 | 18篇 |
1982年 | 21篇 |
1981年 | 24篇 |
1980年 | 26篇 |
1979年 | 13篇 |
1974年 | 2篇 |
1970年 | 2篇 |
1959年 | 12篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
61.
Multimedia Tools and Applications - In Wyner-Ziv (WZ) video coding, decoder side information (SI) takes a key role in a WZ video codec among other building blocks. In this paper, we review the... 相似文献
62.
This paper discusses the compressive performance of perforated brick masonry after fire exposure. Compressive strength tests of the mortar, clay perforated brick, and perforated brick masonry specimens were performed in accordance with ISO834 fire tests of different durations. The temperature distribution of the masonry materials and specimens was simulated using the finite element software ABAQUS, with the thermal parameters of masonry materials recommended by European standard Eurocode 6 and related literature. The compressive strength reduction factors of mortar and clay perforated brick exposed to different fire durations were calculated via the layered method suggested by European standard Eurocode 1. In addition, the compressive strength reduction factors after cooldown were obtained from the experimental data of the masonry materials, and by considering further reductions in the compressive strength after cooling from high temperatures. Experimental data of the masonry specimens were compared with the numerical results obtained using the reduction factors proposed in this work. The comparison revealed an overall acceptable approximation. Thus, the method presented in this paper can be used to evaluate the residual capacity of masonry structures after fire. 相似文献
63.
64.
To improve the electrochemical properties of rare-earth–Mg–Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the ... 相似文献
65.
面向激光增材制造钛合金表面的光整加工需求,设计出一种多磁极耦合旋转磁场光整加工装置来研究光整加工特性。基于ANSYS Maxwell仿真软件分析了光整加工装置的磁场强度分布。搭建了实验光整平台,分析了主轴转速、C轴转速和加工间隙对表面质量的影响。结果表明,在主轴转速500 r/min、C轴转速160 r/min和加工间隙0.7 mm的加工条件下,表面粗糙度Ra由5.991 μm下降至0793 μm。扫描电子显微镜(SEM)观测表明,光整后的钛合金表面沉积层消失,表面质量得到显著改善。 相似文献
66.
Xueli Du Yuelong Wang Rongna Shi Zhiyong Mao Zhihao Yuan 《Journal of the European Ceramic Society》2018,38(10):3512-3517
The PbClxS1-x and Pb1-xBixS (x? =?0–0.05) bulks were fabricated with a facile method of hydrothermal synthesis and microwave sintering, and the effect of anionic and cationic donors on the thermoelectric performance of PbS was investigated. Although Cl? and Bi3+ both effectively improved the thermoelectric properties of n-type PbS, more excellent thermoelectric performance was obtained from Cl? doped samples because of higher electrical property and lower thermal conductivity at higher temperature (T? >?600?K). The thermoelectric figure of merit (ZT) reaches 1.04 for PbCl0.015S0.985 at 800?K and increases with temperature increasing without sign of saturation, which is probably the highest value ever reported for single-phase polycrystalline n-type PbS. The results also indicate that the hydrothermal synthesis and microwave sintering can realize anion doping as well as cation doping for n-type PbS at low cost, and PbS should be a robust alternative for PbTe thermoelectric materials. 相似文献
67.
部分空间科学实验对环境温度有较高的要求,环境温度高于或低于空间科学系统能够提供的热沉温度,需要有可靠有效的加温降温处理措施。使用可靠性强的热电制冷片作为制冷制热方式和气液换热器二次换热来实现环境温度控制的需求,并对不同流体温度制冷制热效果进行分析,结果表明流体温度和目标温度差越小,热电制冷制热的效果越好。在环境温度制冷工况中,热电单元数量随电流增加先减少后增加,在制热工况中则单调递减,设计中需按照制冷工况进行热电单元数量的确定。当流体温度接近制冷制热的目标温度时,会出现整个系统总效率优于热电系统效率的区间。通过对热电单元和气液换热器的组合系统的性能计算,提供一种适于热电环控系统的计算方法和部件选型思路,对空间站环控系统的设计有重要参考意义。 相似文献
68.
Qiang Xia Tao Feng Xiaowei Lou Ying Wang Yangying Sun Daodong Pan Jinxuan Cao 《International Journal of Food Science & Technology》2020,55(2):669-680
As a decisive attribute, flavour could be influenced by HP treatments through multiple physical and chemical pathways within the high pressure (HP)-assisted meat curing process. This investigation aimed to identify the major pathway influencing volatile flavour patterns of two representative vinasse-cured duck (VCD) products with HP treatments (150–300 MPa/15 min), including wet and dry types, by employing headspace fingerprinting as an untargeted approach. Results suggested that HP treatments greatly lowered moisture contents and increased Warner-Bratzler shear force and thiobarbituric acid reactive substances of the cured samples. According to multivariate models, the volatile flavour patterns of the HP-processed VCD could be clearly separated from the unprocessed samples, but the VCD pressurised at different intensities represented similar volatile fingerprinting, which was validated by e-nose analysis. The discriminant analysis (OPLS-DA) model outlined vinasse-derived ethanol, acetic acid, 3-methyl-1-butanol, 2-methyl-1-butanol, phenethyl alcohol and 2-methyl-3-octanone as the major discriminant aromas across the unpressurised and pressurised samples. 相似文献
69.
针对流体输送埋地管道泄漏问题,设计了一种利用管道机器人携带封堵气囊进行快速应急封堵修复的埋地管道泄漏内封堵装置。采用矩阵变换方法建立了牵引系统驱动轮过弯方程,利用MATLAB软件对过弯方程进行了验证,同时利用ADAMS软件仿真分析过弯路径与驱动轮转角对牵引系统行走速度的影响。研究结果表明:由两个串联封堵器组成的应急封堵系统可满足复杂工况下的管道泄漏封堵要求;牵引系统驱动轮在弯管内部行走时,单轮速度呈周期性变化,但三个驱动轮整体周期运动特性一致;驱动轮转角在25°~40°时,牵引系统行走速度与驱动轮转角成正比,且转角为30°时驱动效果最好。该内封堵装置的结构设计可为管道泄漏应急封堵领域装备的研发提供重要参考。 相似文献
70.