全文获取类型
收费全文 | 21727篇 |
免费 | 2466篇 |
国内免费 | 1263篇 |
专业分类
电工技术 | 2014篇 |
综合类 | 2851篇 |
化学工业 | 2019篇 |
金属工艺 | 1325篇 |
机械仪表 | 2433篇 |
建筑科学 | 2125篇 |
矿业工程 | 1119篇 |
能源动力 | 865篇 |
轻工业 | 642篇 |
水利工程 | 509篇 |
石油天然气 | 818篇 |
武器工业 | 588篇 |
无线电 | 2600篇 |
一般工业技术 | 2234篇 |
冶金工业 | 729篇 |
原子能技术 | 203篇 |
自动化技术 | 2382篇 |
出版年
2024年 | 103篇 |
2023年 | 285篇 |
2022年 | 473篇 |
2021年 | 586篇 |
2020年 | 678篇 |
2019年 | 615篇 |
2018年 | 621篇 |
2017年 | 809篇 |
2016年 | 880篇 |
2015年 | 884篇 |
2014年 | 1372篇 |
2013年 | 1424篇 |
2012年 | 1665篇 |
2011年 | 1682篇 |
2010年 | 1296篇 |
2009年 | 1337篇 |
2008年 | 1184篇 |
2007年 | 1443篇 |
2006年 | 1266篇 |
2005年 | 1086篇 |
2004年 | 859篇 |
2003年 | 750篇 |
2002年 | 657篇 |
2001年 | 616篇 |
2000年 | 502篇 |
1999年 | 389篇 |
1998年 | 327篇 |
1997年 | 342篇 |
1996年 | 251篇 |
1995年 | 215篇 |
1994年 | 183篇 |
1993年 | 142篇 |
1992年 | 119篇 |
1991年 | 101篇 |
1990年 | 67篇 |
1989年 | 56篇 |
1988年 | 52篇 |
1987年 | 36篇 |
1986年 | 22篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1963年 | 3篇 |
1959年 | 4篇 |
1958年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Beebe-Frankenberger Margaret; Bocian Kathleen M.; MacMillan Donald L.; Gresham Frank M. 《Canadian Metallurgical Quarterly》2004,96(2):204
A cohort of 2nd-grade students provided comparisons of academic and social competence based on school retention/promotion decisions. Sample groups were (a) retained, (b) at risk for retention, (c) special education, and (d) promoted. Findings suggested most children with academic deficiencies are identified by schools early and are sorted into educational treatments differing in intensity that represent a continuum of competence. The authors provide empirical evidence counter to the assumptions that retained students have the requisite ability to catch up and have more problem behaviors than other low-achieving students. The relevance of high-stakes test scores for promotion/retention decisions and the parallels between schools' implementation of retention policy and implementation of regulations for identifying children with disabilities are included in the discussion. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
4.
微带型Wilkinson功分器设计与实现 总被引:2,自引:0,他引:2
小型低功耗器件是射频电路设计的研究热点,而微带技术具有小型化低功耗的优点,为此在介绍微带型Wilkin-son功分器工作原理的基础上,使用基于矩量法的ADS软件设计、仿真和优化计算相关数据参数,并制作了一个微带功分器实例,最后对加工的样品进行实测,获得与仿真值吻合较好的预期结果。 相似文献
5.
6.
在目标信号检测模块的基础上增加了测有计算模块,构成一种新型的单脉冲雷达点迹提取器,显著提高了雷达系统潜在的处理能力。 相似文献
7.
B. Bereqvist 《Strain》1987,23(1):7-13
The design and performance of precision bending equipment for testing straight beams with constant rectangular section under a pure bending moment is described. Part 1 deals with the loading arrangements and Part 2 with the rig for measuring beam deflection. The methods for recording deflection of strain gauges applied on the beam have been described elsewhere.1–4
The reactions to the deadweight gravity loads are taken via ball bearings. The total bending moment inaccuracy, i.e. the sum of estimated systematic errors and random errors, the latter expressed as the 2Ga confidence interval about the mean (2Gcim ), is about ± 25 x. 10-4% , for 23 tests with a steel beam with 15 mm × 75 mm cross sectional dimensions, loaded to 1-1.5 mm/m strain.
The measuring rig stands on the beam via hardened and polished spherical segment feet and uses a capacitive transducer system with less than 5nm resolution. Various application tasks are described. The total inaccuracy of the measured deflection, i.e. apart from bending moment inaccuracy, is about ± 35 times 104% for about 10 reproduced, not repeated, tests with the same steel beam. The deflection for such a beam is of the order of 2 to 4 mm. 相似文献
The reactions to the deadweight gravity loads are taken via ball bearings. The total bending moment inaccuracy, i.e. the sum of estimated systematic errors and random errors, the latter expressed as the 2Ga confidence interval about the mean (2G
The measuring rig stands on the beam via hardened and polished spherical segment feet and uses a capacitive transducer system with less than 5nm resolution. Various application tasks are described. The total inaccuracy of the measured deflection, i.e. apart from bending moment inaccuracy, is about ± 35 times 10
8.
W. Shang B. Robrahn F. Golding M. H. J. Koch 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2004,530(3):513-520
A data acquisition system for time resolved X-ray scattering experiments using linear, quadrant or area gas proportional detectors with delay line readout based on commercially available hardware (National Instruments) is described. The system can easily be configured for recording data from point detectors (e.g. photomultipliers and photodiodes) and/or ancillary data only. Applications involving measurements with two different types of time to digital converters illustrate the features and performances of the system. 相似文献
9.
10.
The acquisition of new skills over a life span is a remarkable human ability. This ability, however, is constrained by age of acquisition (AoA); that is, the age at which learning occurs significantly affects the outcome. This is most clearly reflected in domains such as language, music, and athletics. This article provides a perspective on the neural and computational mechanisms underlying AoA in language acquisition. The authors show how AoA modulates both monolingual lexical processing and bilingual language acquisition. They consider the conditions under which syntactic processing and semantic processing may be differentially sensitive to AoA effects in second-language acquisition. The authors conclude that AoA effects are pervasive and that the neural and computational mechanisms underlying learning and sensorimotor integration provide a general account of these effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献