全文获取类型
收费全文 | 2916篇 |
免费 | 49篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 289篇 |
金属工艺 | 44篇 |
机械仪表 | 92篇 |
建筑科学 | 49篇 |
矿业工程 | 4篇 |
能源动力 | 61篇 |
轻工业 | 68篇 |
水利工程 | 5篇 |
石油天然气 | 10篇 |
无线电 | 218篇 |
一般工业技术 | 396篇 |
冶金工业 | 1445篇 |
原子能技术 | 61篇 |
自动化技术 | 214篇 |
出版年
2023年 | 18篇 |
2022年 | 31篇 |
2021年 | 37篇 |
2020年 | 34篇 |
2019年 | 31篇 |
2018年 | 34篇 |
2017年 | 30篇 |
2016年 | 35篇 |
2015年 | 23篇 |
2014年 | 48篇 |
2013年 | 104篇 |
2012年 | 60篇 |
2011年 | 93篇 |
2010年 | 88篇 |
2009年 | 72篇 |
2008年 | 74篇 |
2007年 | 63篇 |
2006年 | 62篇 |
2005年 | 35篇 |
2004年 | 38篇 |
2003年 | 43篇 |
2002年 | 34篇 |
2001年 | 27篇 |
2000年 | 29篇 |
1999年 | 59篇 |
1998年 | 409篇 |
1997年 | 269篇 |
1996年 | 166篇 |
1995年 | 117篇 |
1994年 | 84篇 |
1993年 | 96篇 |
1992年 | 28篇 |
1991年 | 49篇 |
1990年 | 46篇 |
1989年 | 34篇 |
1988年 | 33篇 |
1987年 | 43篇 |
1986年 | 34篇 |
1985年 | 41篇 |
1984年 | 27篇 |
1983年 | 25篇 |
1982年 | 27篇 |
1981年 | 25篇 |
1980年 | 23篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1977年 | 44篇 |
1976年 | 74篇 |
1975年 | 8篇 |
1973年 | 9篇 |
排序方式: 共有2975条查询结果,搜索用时 15 毫秒
21.
22.
23.
In the present investigation a higher-order shear deformation theory and the conventional first-order theory are used to develop a finite element method to analyse accurately the bending and free vibration behaviour of laminated composite beams, using nine-noded isoparametric elements. The higher-order theory assumes all the displacement components, u, v and w, which contain variation up to a cubic power of z. The effects of various parameters such as fibre orientation, stacking sequence, span-to-thickness ratio and support condition on the non-dimensionalised deflections, stresses and fundamental frequencies are investigated. Cases where only the higher-order theory is likely to yield accurate results are highlighted. 相似文献
24.
Forty paediatric cases of A.R.F. (Acute Renal Failure) of various aetiology were included in the study. 60% of patients were less than 4 years of age with male predominance. 80% cases reported to us very late with oligoanuria of more than 24 hours (2-7 days). Diarrhoea, vomiting and fever were other dominant symptoms. Maximum cases were severely anaemic (87.5%) with mean Hb 7.73 +/- 1.9 gm%. 40% cases were of underweight while only one case (2.5%) was of over weight, inspite of volume excess in 40% cases. All 24 cases, who were estimated for serum albumin, found to have marked hypoalbuminemia. Mortality was found to be as high as 65% inspite of effective peritoneal dialysis in all cases. High mortality seems to be due to profound anuria of many days (because of marked delay in reaching the hospital), fever and malnutrition besides other factors as aetiology. 相似文献
25.
26.
V. Sinha M. J. Mills J. C. Williams 《Metallurgical and Materials Transactions A》2004,35(10):3141-3148
This article presents the results of a recent study of the response of an α/β-forged Ti-6Al-2Sn-4Zr-2Mo alloy during static, normal-fatigue, and dwell-fatigue loading. The plastic-strain accumulation
under different loading conditions is reported. The failure modes and associated fractographic features under static, normal-fatigue,
and dwell-fatigue loading conditions are also discussed. These results are used to obtain a better understanding of the relative
contributions of the cyclic and creep processes to the overall damage under dwell-fatigue conditions. 相似文献
27.
The basics of acoustic resonance spectroscopy (ARS), which provides data about an object's physical structure and composition, are explained. In ARS, one actively excites a large number of resonances (normal modes) in an object that has no internal vibrations by slowly sweeping the excitation frequency to obtain an acoustic spectrum of the object. The instrumentation for this nondestructive evaluation technique is described, and some applications are briefly discussed 相似文献
28.
Zaleski A. Sinha S.P. Ioannou D.E. Campisi G.J. Hughes H.L. 《Electron Devices, IEEE Transactions on》1995,42(9):1697-1700
By operating one channel of a typical SOI MOSFET in avalanche while keeping the opposite channel accumulated, charge injection into the opposite gate takes place. Three independent experiments are described that demonstrate the occurrence of this opposite-channel based charge injection. The experimental results are in agreement with PISCES numerical simulations 相似文献
29.
RK Batra JC Olsen DK Hoganson B Caterson RC Boucher 《Canadian Metallurgical Quarterly》1997,272(18):11736-11743
Gene therapy may be an important adjuvant for treating cancer in the pleural space. The initial results of retroviral gene transfer to cancer cells in malignant pleural effusions revealed that transduction was markedly inhibited, and studies to characterize the inhibitory factor(s) were performed. The inhibition was contained within the soluble, rather than cellular, components of the effusions and was demonstrated with amphotropic, gibbon ape leukemia virus, and vesicular stomatitis virus-glycoprotein pseudotyped retroviral vectors. After excluding complement proteins, a series of studies identified chondroitin sulfates (CSs) as the inhibitory substances. First, treatment of the effusions with mammalian hyaluronidase or chondroitinases, but not Streptomyces hyaluronidase, abolished the inhibitory activity. Second, addition of exogenous CS glycosaminoglycans mimicked the inhibition observed with pleural effusions. Third, immunoassays and biochemical analyses of malignant pleural effusion specimens revealed CS in relevant concentrations within pleural fluid. Fourth, proteoglycans/glycosaminoglycans isolated from the effusions inhibited retroviral gene transfer. Analyses of the mechanism of inhibition indicate that the chondroitin sulfates interact with vector in solution rather than at the target cell surface. These results suggest that drainage of the malignant pleural effusion, and perhaps enzymatic pretreatment of the pleural cavity, will be necessary for efficient retroviral vector mediated gene delivery to pleural metastases. 相似文献
30.
Comparison of interaction energy between an oligonucleotide and a DNA-binding ligand in the minor and major groove modes was made by use of restrained molecular dynamics. Distortion in DNA was found for the major groove mode whereas less significant changes for both ligand and DNA were detected for the minor groove binding after molecular dynamics simulation. The conformation of the ligand obtained from the major groove modes resembles that computed with the ligand soaked in water. The van der Waals contact energy was found to be as significant as electrostatic energy and more important for difference in binding energy between these two binding modes. The importance of van der Waals force in groove binding was supported by computations on the complex formed by the repressor peptide fragment from the bacteriophage 434 and its operator oligonucleotide. 相似文献