全文获取类型
收费全文 | 5593篇 |
免费 | 533篇 |
国内免费 | 321篇 |
专业分类
电工技术 | 142篇 |
综合类 | 848篇 |
化学工业 | 344篇 |
金属工艺 | 190篇 |
机械仪表 | 433篇 |
建筑科学 | 1945篇 |
矿业工程 | 212篇 |
能源动力 | 98篇 |
轻工业 | 111篇 |
水利工程 | 294篇 |
石油天然气 | 310篇 |
武器工业 | 85篇 |
无线电 | 433篇 |
一般工业技术 | 583篇 |
冶金工业 | 163篇 |
原子能技术 | 19篇 |
自动化技术 | 237篇 |
出版年
2024年 | 18篇 |
2023年 | 64篇 |
2022年 | 162篇 |
2021年 | 205篇 |
2020年 | 152篇 |
2019年 | 131篇 |
2018年 | 149篇 |
2017年 | 209篇 |
2016年 | 187篇 |
2015年 | 208篇 |
2014年 | 357篇 |
2013年 | 318篇 |
2012年 | 388篇 |
2011年 | 426篇 |
2010年 | 341篇 |
2009年 | 343篇 |
2008年 | 302篇 |
2007年 | 410篇 |
2006年 | 356篇 |
2005年 | 280篇 |
2004年 | 195篇 |
2003年 | 167篇 |
2002年 | 142篇 |
2001年 | 158篇 |
2000年 | 140篇 |
1999年 | 112篇 |
1998年 | 99篇 |
1997年 | 81篇 |
1996年 | 77篇 |
1995年 | 59篇 |
1994年 | 38篇 |
1993年 | 38篇 |
1992年 | 35篇 |
1991年 | 24篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1959年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有6447条查询结果,搜索用时 46 毫秒
1.
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
2.
Alia-Klein Nelly; Goldstein Rita Z.; Tomasi Dardo; Zhang Lei; Fagin-Jones Stephanie; Telang Frank; Wang Gene-Jack; Fowler Joanna S.; Volkow Nora D. 《Canadian Metallurgical Quarterly》2007,7(4):735
Reports an error in "What is in a word? No versus Yes differentially engage the lateral orbitofrontal cortex" by Nelly Alia-Klein, Rita Z. Goldstein, Dardo Tomasi, Lei Zhang, Stephanie Fagin-Jones, Frank Telang, Gene-Jack Wang, Joanna S. Fowler and Nora D. Volkow (Emotion, 2007[Aug], Vol 7[3], 649-659). The supplemental materials link should appear as follows: http://dx.doi.org/10.1037/1528-3542.7.3.649.supp. (The following abstract of the original article appeared in record 2007-11660-018.) The words "No" and "Yes" are involved in conditioning to prohibit or encourage behavior, respectively. The authors, therefore, hypothesized that these words would be attributed to endogenous valence, activating neuronal circuits involved with valence and emotional control. Functional MRI (fMRI) at 4 Tesla was used to record regional brain activity while participants were exposed to emphatic vocalizations of the words. Results showed that No and Yes were associated with opposite brain-behavior responses; while No was negatively valenced, produced slower response times, and evoked a negative signal in the right lateral orbitofrontal cortex (OFC), Yes was positively valenced, produced faster response times, and evoked a positive signal in a contiguous region of the OFC. Attribution of negative valence to No and trait anger control were associated with increased responsivity of the OFC to No. Inasmuch as sensitivity to the prohibitive command No develops during childhood through interaction with primary caregivers as the first social objects, our findings may implicate the lateral OFC in the neurobiology of emotion regulation and subsequent social development. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
4.
小高层建筑需通过剪力墙开洞(结构开洞)降低侧向刚度,本文对开洞部位以及墙肢和连梁设计提出一些看法,供设计人员参考。 相似文献
5.
New mesogenic homologous series having an azo central linkage was synthesized by fixing a rigid 4-methyl phenyl azo group
to resorcinol moiety. The terminal and lateral phenolic -OH groups were esterified, one by one, with 4-n-alkoxybenzoyl and acetyl group, respectively. All the twelve homologues synthesized exhibit mesomorphism. The methoxy ton-decyloxy andn-hexadecyloxy derivatives exhibit monotropic nematic mesophase whereas,n-dodecyloxy andn-tetradecyloxy derivatives exhibit enantiotropic nematic mesophase. The mesogenic properties of the present series was compared
with those of other structurally related mesogenic series.
Paper presented at the 5th National Seminar on Liquid Crystals, University of Jammu, Jammu, December 1997. 相似文献
6.
Ashraf Ayoub 《Computers & Structures》2003,81(7):411-421
This paper presents an inelastic element for the analysis of beams on foundations. The element is derived from a two-field mixed formulation with independent approximation of forces and displacements. The state determination algorithm for the implementation of the element in a general purpose nonlinear finite element analysis program is presented and its stability characteristics are discussed. Numerical studies are performed to compare the model with the classical displacement formulation. The studies confirm the superiority of the proposed model in describing the inelastic behavior of beams on foundations. 相似文献
7.
8.
钢结构稳定设计——理论与实践 总被引:2,自引:0,他引:2
本文提出了实际工程结构的非线性理论设计和分析方法(NIDA),并以澳门回归纪念馆的设计为例,展示了本方法的优越性.在设计过程中,设计者无需假设K系数和有效长度,在结构分析完成后便可迅速完成设计,因此本文提出的方法既经济又便利.尽管对于钢框架在往复荷载及动力荷载作用下的弹塑性大位移分析已经非常成熟,但本文的方法开创了结构的非线性分析及设计的新纪元,能够对现行的设计方法理论起到巨大的推动作用. 相似文献
9.
新型PDC钻头的防斜打快效果及评价 总被引:5,自引:0,他引:5
大庆油田海拉尔地区的地层倾角大、岩屑录井荧光级别低,亟待解决满足岩屑录井要求的防斜打直问题。为了能够在获得足够大的岩屑颗粒和提高机械钻速的基础上达到防斜打直的目的,制定了采用大切削齿B425型PDC钻头配以小钟摆钻具组合的现场试验方案。试验表明:B425钻头与牙轮钻头所破碎的岩屑颗粒基本相当,能够满足地质岩屑录井的要求;与牙轮钻头相比,B425钻头显著地提高了机械钻速,降低了钻头费用,减少了起下钻次数;单只B425的进尺可达1000m以上,相当于2~3只牙轮钻头的进尺;采用PDC钻头配以小钟摆钻具组合,可以较好地解决防斜打直问题。此外,针对试验中遇到的问题,通过改进井身结构和调整钻井参数,形成了一套适合于海拉尔地区的防斜打快技术。 相似文献
10.