全文获取类型
收费全文 | 130799篇 |
免费 | 10029篇 |
国内免费 | 5169篇 |
专业分类
电工技术 | 7236篇 |
技术理论 | 8篇 |
综合类 | 11183篇 |
化学工业 | 20968篇 |
金属工艺 | 3997篇 |
机械仪表 | 4043篇 |
建筑科学 | 21368篇 |
矿业工程 | 6914篇 |
能源动力 | 7253篇 |
轻工业 | 8593篇 |
水利工程 | 20014篇 |
石油天然气 | 9657篇 |
武器工业 | 384篇 |
无线电 | 4656篇 |
一般工业技术 | 8135篇 |
冶金工业 | 5020篇 |
原子能技术 | 1775篇 |
自动化技术 | 4793篇 |
出版年
2024年 | 419篇 |
2023年 | 1509篇 |
2022年 | 2885篇 |
2021年 | 3563篇 |
2020年 | 3824篇 |
2019年 | 3235篇 |
2018年 | 3225篇 |
2017年 | 3863篇 |
2016年 | 4242篇 |
2015年 | 4303篇 |
2014年 | 7841篇 |
2013年 | 7845篇 |
2012年 | 9308篇 |
2011年 | 9964篇 |
2010年 | 7204篇 |
2009年 | 7618篇 |
2008年 | 6809篇 |
2007年 | 8685篇 |
2006年 | 8067篇 |
2005年 | 7218篇 |
2004年 | 5750篇 |
2003年 | 5103篇 |
2002年 | 4484篇 |
2001年 | 3692篇 |
2000年 | 3122篇 |
1999年 | 2501篇 |
1998年 | 1926篇 |
1997年 | 1614篇 |
1996年 | 1256篇 |
1995年 | 1106篇 |
1994年 | 826篇 |
1993年 | 590篇 |
1992年 | 486篇 |
1991年 | 356篇 |
1990年 | 265篇 |
1989年 | 295篇 |
1988年 | 189篇 |
1987年 | 169篇 |
1986年 | 139篇 |
1985年 | 127篇 |
1984年 | 120篇 |
1983年 | 70篇 |
1982年 | 39篇 |
1981年 | 23篇 |
1980年 | 43篇 |
1979年 | 23篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
A. Alt Dr.‐Ing. H. Mertens U. Arz L. Blessing C. Berger 《Materialwissenschaft und Werkstofftechnik》2007,38(5):402-409
High cycle fatigue of bolted connections Extensive tests regarding the influences on the fatigue of bolt‐nut‐connections of preloading with torsion, of preloading with yielding, of loading with superimposed bending and of the tested lot are processed. These influences are not yet known according to VDI 2230. New testing devices were designed for these tests, which allow a far less expensive operation and may easily be used for bolts of diameters up to M100 and testing frequencies up to 1000 Hz. The validity of fatigue resistance according to VDI 2230 is specified with respect to the test results. The determined influence of the tested lots is unexpectedly high. The manufacturing process of bolts should be improved to minimize this influence. 相似文献
24.
This paper evaluates the behavior and performance of laminated circular elastomeric bearings and compares them to those of square and rectangular bearings. The study included an experimental evaluation and a nationwide survey of state Department of Transportations on the use and performance of circular bearings and bearings in general in their states. The experimental investigation studied the bearings' behavior in compression, compression and rotation, and compression and shear. Results from this limited study showed that the three bearings have similar stress-strain behavior in compression and they are in agreement with the AASHTO LRFD guide stress–strain curves. In compression and rotation, the AASHTO LRFD substructure moments are slightly less than the measured values for circular bearings and rectangular bearings rotated about their strong axis for a compressive stress of 10.3?MPa (1.5?ksi) and slightly higher than those of rectangular bearings rotated about their weak axis. In compression and shear, the shear stiffness of circular and square bearings is in agreement with theoretical values within the range of design displacements. Results from the survey showed that many states are using circular bearings and more states would consider using them, however no maintenance or monitoring data were available on their short-term and long-term performance. 相似文献
25.
一种复合型数值方法的改进与算法实现 总被引:3,自引:1,他引:2
文中对原有的复合方法进行了改进,提出了一种新的复合型数值方法,这种方法解决了原方法求解含源项的问题时存在数值震荡的缺点。为了验证算法的有效性,对计算流体力学中一阶浅水波问题的两个典型的算例进行了数值模拟,在解的光滑性、锐利性等几个方面做了分析,结果表明改进后的方法既消除了数值震荡现象,又能准确地逼近真解,求出锐利的间断,是一种行之有效的数值方法。 相似文献
26.
简要介绍了鞍钢现有人造富矿生产能力,分析了鞍钢生产1600万t/a生铁所需要的炉料数量、品种和质量,并提出了解决炉料缺口的方法和措施。 相似文献
27.
官泓 《有色冶金设计与研究》2003,24(3):49-51
阐述水厂设计中对水厂规模、水源地、净水厂位置及净水工艺的确定过程,根据原水的特点,通过分析对无阀滤池进行改良。 相似文献
28.
The eye movements of young and older adults were tracked as they read sentences varying in syntactic complexity. In Experiment 1, cleft object and object relative clause sentences were more difficult to process than cleft subject and subject relative clause sentences; however, older adults made many more regressions, resulting in increased regression path fixation times and total fixation times, than young adults while processing cleft object and object relative clause sentences. In Experiment 2, older adults experienced more difficulty than young adults while reading cleft and relative clause sentences with temporary syntactic ambiguities created by deleting the that complementizers. Regression analyses indicated that readers with smaller working memories need more regressions and longer fixation times to process cleft object and object relative clause sentences. These results suggest that age-associated declines in working memory do affect syntactic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
30.
高频数字锁相环的研究 总被引:5,自引:0,他引:5
论文阐述了100MHz数字锁相环的设计过程,用10MHz晶体振荡器对100MHz数字压控振荡器进行锁相,使100MHz输出信号指标得到很大改善。论文还分析了各单元电路,关键点时域波形测试,频谱测试。 相似文献