全文获取类型
收费全文 | 23243篇 |
免费 | 1949篇 |
国内免费 | 876篇 |
专业分类
电工技术 | 320篇 |
综合类 | 3293篇 |
化学工业 | 2049篇 |
金属工艺 | 2817篇 |
机械仪表 | 3527篇 |
建筑科学 | 4773篇 |
矿业工程 | 647篇 |
能源动力 | 267篇 |
轻工业 | 424篇 |
水利工程 | 628篇 |
石油天然气 | 1666篇 |
武器工业 | 175篇 |
无线电 | 832篇 |
一般工业技术 | 2524篇 |
冶金工业 | 707篇 |
原子能技术 | 72篇 |
自动化技术 | 1347篇 |
出版年
2024年 | 117篇 |
2023年 | 340篇 |
2022年 | 518篇 |
2021年 | 664篇 |
2020年 | 677篇 |
2019年 | 626篇 |
2018年 | 700篇 |
2017年 | 852篇 |
2016年 | 876篇 |
2015年 | 815篇 |
2014年 | 1479篇 |
2013年 | 1341篇 |
2012年 | 1624篇 |
2011年 | 1771篇 |
2010年 | 1530篇 |
2009年 | 1459篇 |
2008年 | 1238篇 |
2007年 | 1656篇 |
2006年 | 1438篇 |
2005年 | 1125篇 |
2004年 | 1040篇 |
2003年 | 806篇 |
2002年 | 599篇 |
2001年 | 530篇 |
2000年 | 494篇 |
1999年 | 352篇 |
1998年 | 255篇 |
1997年 | 232篇 |
1996年 | 188篇 |
1995年 | 194篇 |
1994年 | 98篇 |
1993年 | 84篇 |
1992年 | 84篇 |
1991年 | 53篇 |
1990年 | 38篇 |
1989年 | 33篇 |
1988年 | 41篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1980年 | 5篇 |
1960年 | 4篇 |
1959年 | 4篇 |
1957年 | 3篇 |
1956年 | 5篇 |
1955年 | 6篇 |
1954年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
81.
82.
硬粒子对聚合物材料表面的冲击摩擦研究 总被引:3,自引:3,他引:0
冲击摩擦为接触面切向与法向冲量之比。用聚合物材料试件与弹簧钢片组成振动测试系统 ,硬粒子以一定入射角冲击试件水平面引起系统振动 ,接触冲量通过振幅反映出来 ,记录初始振幅值而计算出一个冲击过程的冲击摩擦因数。结果表明 ,当入射角α在 2 5°-60°变化时 ,冲击摩擦因数f从 0 .5降至 0 .2左右。文章同时分析讨论了摩擦对聚合物表面接触强度的影响。 相似文献
83.
The determination of the Young’s modulus and damping coefficient Q−1 by means of non-destructive vibrating techniques has been applied to bulk and coated industrial materials. Extensions of a previous analytic model of composite beam allow to determine accurately the macroscopic modulus of each component of multilayered structural materials as coated superalloys or nitride-hardened steels. Furthermore, the study of glasses and polymers has been investigated. An attempt of normalisation of the modulus versus temperature curves allows to establish master curves depending on the specific structure, from metallic glasses to polymeric glasses. Finally a comparison of dynamical modulus and Q−1 values measured between resonant (>1 kHz) and subresonant techniques (10−3 to 10 Hz) in relation to the loading frequencies applied in real conditions has been under folder. For metallic materials such as forged or rolled titanium alloys, the brittle-to-fragile transition occurs abruptly or smoothly with a shift of 300 K following the range of excitation frequencies. 相似文献
84.
The mechanical and microstructural properties of 6061+20% Al2O3p and 7005+10% Al2O3p aluminium based metal matrix composites joined by friction stir welding were analyzed in the present study. The two materials were welded into the form of sheets of 7 mm thickness after T6 treatment and were tested in tension at room temperature. The microstructure of the joints was observed by optical microscopy and the fracture surfaces were analyzed by employing a scanning electron microscope equipped with field emission gun in order to study the micromechanisms involved during the deformation. 相似文献
85.
Reports an error in "Temporal Encoding in Fear Conditioning Revealed Through Associative Reflex Facilitation" by Derick H. Lindquist and Thomas H. Brown (Behavioral Neuroscience, 2004[Apr], Vol 118[2], 395-402). The article contained several errors. On page 396, second paragraph, the sentence beginning on line 6 should read as follows: "Having a stable baseline is critical for studies of reflex facilitation because the experimental designs invariably entail repetitive CR testing, if only to achieve reasonable statistical power (see Choi et al., 2001b; Lindquist & Brown, 2004)." On page 400, the first heading should read as follows: "Comparison of New and Old Reflex Facilitation Procedures." On page 400, the first sentence under the abovementioned heading should read as follows: "We decided not to use the original measure of reflex facilitation, developed by J. S. Brown et al. (1951), because it suffers from severe interpretational limitations, elaborated in detail elsewhere (Choi et al., 2001b; Leaton & Cranney, 1990; Lindquist & Brown, 2004)." (The following abstract of the original article appeared in record 2004-12681-016.) Temporal encoding in Pavlovian fear conditioning was examined through conditional facilitation of the short-latency (Rl) component of the rat eyeblink reflex. Rats were fear-conditioned to a tone conditional stimulus (CS) with either a 3- or 9-s interstimulus interval (ISI) between CS onset and the onset of the grid-shock unconditional stimulus (US). Rl facilitation was tested over 2 days, in counterbalanced order, at a latency of 3 s and 9 s from CS onset. CS-produced Rl facilitation, the conditional response (CR), was 3-4 times larger when the test latency equaled the conditioning ISI. These results, coupled with the known neurophysiology of Rl facilitation, suggest that this CR could disclose differences in the time course of CS-generated output from the amygdala when driven by cortical versus subcortical CS-CR pathways. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
86.
本文通过对摩擦片厚度在线测量装置系统构成的全面分析,对其驱动电路子系统进行了理论探索和技术研究,完成了相应的电路设计、误差分析及器件选择等工作,并进行了具体的实验验证,证明该驱动电路具有良好的性能,可圆满实现摩擦片厚度在线检测和实时分析的工作任务。 相似文献
87.
We have used a resonant ultrasound spectroscopy technique to measure the bulk and shear modulus of fully dense, polycrystalline MgB2 between 4 and 300 K. Both moduli show good agreement with published first principle calculations. The internal friction shows a broad maximum around 40 K. 相似文献
88.
Unconrolled agglomeration of particles and adhesion of the particulate mass to wall surfaces are common severe problems in many drying operations. This paper reviews the mechanisms of interparticle and particle-surface attraction as well as the theory and the existing tests for characterising powders in terms of internal strength, wall friction and adhesion. The usefulness of the information obtained from these tests in dryer design and operation is critically reviewed. The importance of powder stickiness in various types of dryers is discussed and established methods of combating the problem are presented Recommendations an made for further research in the area of powder cohesion and adhesion. 相似文献
89.
The present investigation showed that the re-laxation peak at about 200℃ (f≈1Hz) was relatedto bainitic transformation in a CuZnAl alloy.Thepeak decreased when bainite precipitated.Theactivation energy of the peak was the same as theapparent activation energy of bainitic transforma-tion.According to the relations between the peakand the bainitic transformation,the mechanism ofthe peak has been discussed. 相似文献
90.