全文获取类型
收费全文 | 1528篇 |
免费 | 71篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 32篇 |
综合类 | 4篇 |
化学工业 | 324篇 |
金属工艺 | 87篇 |
机械仪表 | 173篇 |
建筑科学 | 11篇 |
能源动力 | 33篇 |
轻工业 | 123篇 |
水利工程 | 1篇 |
无线电 | 197篇 |
一般工业技术 | 274篇 |
冶金工业 | 167篇 |
原子能技术 | 34篇 |
自动化技术 | 146篇 |
出版年
2023年 | 14篇 |
2022年 | 9篇 |
2021年 | 46篇 |
2020年 | 20篇 |
2019年 | 32篇 |
2018年 | 31篇 |
2017年 | 48篇 |
2016年 | 43篇 |
2015年 | 24篇 |
2014年 | 44篇 |
2013年 | 85篇 |
2012年 | 93篇 |
2011年 | 95篇 |
2010年 | 59篇 |
2009年 | 69篇 |
2008年 | 71篇 |
2007年 | 60篇 |
2006年 | 71篇 |
2005年 | 59篇 |
2004年 | 41篇 |
2003年 | 51篇 |
2002年 | 51篇 |
2001年 | 33篇 |
2000年 | 46篇 |
1999年 | 44篇 |
1998年 | 64篇 |
1997年 | 49篇 |
1996年 | 55篇 |
1995年 | 27篇 |
1994年 | 26篇 |
1993年 | 13篇 |
1992年 | 9篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 20篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 12篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1968年 | 3篇 |
排序方式: 共有1606条查询结果,搜索用时 15 毫秒
101.
JS Chang DY Noh IA Park MJ Kim H Song SH Ryu PG Suh 《Canadian Metallurgical Quarterly》1997,57(24):5465-5468
Phospholipase C-gamma1 (PLC-gamma1) mediates signals from various extracellular origins to evoke cellular events such as mitogenesis. Previously, we reported that PLC-gamma1 was highly expressed in colorectal cancer and familial adenomatous polyposis, suggesting that PLC-gamma1 might be oncogenic. In this study, we have established rat 3Y1 fibroblasts that overexpress whole PLC-gamma1 and src homology 2 (SH2)-SH2-SH3 domain of PLC-gamma1. These cells showed a transformed phenotype and were tumorigenic when transplanted into nude mice. These results indicate that overexpression of PLC-gamma1 could transform rat fibroblasts, and the transformation is mediated by SH2-SH2-SH3 domain of PLC-gamma1. 相似文献
102.
We compared the dose-response relationships of cisatracurium, mivacurium, atracurium, vecuronium and rocuronium and examined the interactions of cisatracurium with mivacurium, atracurium, vecuronium and rocuronium in humans by isobolographic and fractional analyses. We studied 180 adult patients during nitrous oxide-fentanyl-propofol anaesthesia. Neuromuscular block was monitored using mechanomyography to detect the twitch response of the ulnar nerve at the wrist. The dose-response curves were determined by probit analysis. The calculated ED50 values and their 95% confidence intervals were 40.9 (38.1-43.7), 49.8 (47.0-52.6), 187.2 (175.1-199.3), 36.6 (34.7-38.5) and 136.4 (129.2-143.6) micrograms.kg-1 for cisatracurium, mivacurium, atracurium, vecuronium and rocuronium, respectively. Corresponding ED95 values were 57.6 (53.5-61.7), 91.8 (88.1-95.5), 253.1 (238.9-267.3), 52.9 (49.1-56.7) and 288.7 (276.2-301.2) micrograms.kg-1, respectively. The interaction between cisatracurium and mivacurium, vecuronium or rocuronium was found to be synergistic, but the interaction between cisatracurium and atracurium was found to be additive. Synergy between cisatracurium and vecuronium or rocuronium was greater than between cisatracurium and mivacurium. 相似文献
103.
104.
Abrasive wear mechanisms and the grit size effect 总被引:2,自引:0,他引:2
The classical cutting model for abrasive wear deviates from reality in that it cannot predict the effect of grit size on wear and that the observed wear rates are at least an order of magnitude smaller than the predicted values. Through experimental and theoretical work it is shown in this paper that the grit size effect is a consequence of the transition from a cutting mechanism to a sliding wear mechanism. The wear coefficient is shown to be less than that predicted by a cutting model owing to the plastic deformation of the surface being worn. 相似文献
105.
Natural convection thermo fluid dynamics in a volumetrically heated rectangular pool 总被引:1,自引:0,他引:1
During a severe accident the nuclear reactor core may melt and, further, relocate to the lower plenum in the reactor vessel. Should there be no effective cooling mechanism, the core debris may heat up on account of the volumetric decay heat generation to form a molten pool in natural convection. The Simulant Internal Gravitated Material Apparatus Rectangular Pool (SIGMA RP) tests were performed to study high modified Rayleigh number (Ra′) natural convection in a rectangular pool. The test apparatus was 500 mm long, 500 mm high and 160 mm wide. Forty thin cartridge heaters, with a sheath diameter of 4.2 mm and a length of 600 mm, were used to simulate internal heating in the pool. They were uniformly distributed in the rectangular pool so as to supply a maximum of 2.5 kW power to the pool. Ra′ based on the power input was varied from 109 to 1014. The working fluid Prandtl number (Pr) ranged from 4 to 8 for water, and 0.7 for air. Particular attention was paid to the Pr influence on natural convection heat transfer in the pool. The relation between the Nusselt number (Nu) and Ra′ was determined for different boundary conditions in the rectangular pool. In one case the upper wall was cooled isothermally, while the lower wall was kept adiabatic. In the other case both the upper and lower walls were cooled isothermally. The experimental results indicated that both the upward and downward natural convection heat transfer rates were affected by Pr. The resultant engineering correlations were applied to simulation of a spectrum of loss-of-coolant accidents to determine the reactor vessel failure time. 相似文献
106.
Suh J.-Y. Byun J.-S. Shim J.-H. Oh Y.-J. Shim J.-D. 《Materials Science & Technology》2013,29(11-12):1277-1281
AbstractDifferent microstructures having acicular ferrite as the major phase but with various types and amounts of microphases were obtained by applying different cooling processes to C–Mn steels containing fine non-metallic inclusions. Optical and electron microscopy were carried out to identify the various microphases in the acicular ferrite microstructure, and their mechanical properties were measured and compared to study the effect of the microphases on the microstructure–properties relationship in C–Mn wrought steels. The existence and increase of the fraction of small isolated martensite between the acicular ferrite laths were found to play an important role in determining the tensile strength and low temperature impact toughness of the steels. However, the elongation and room temperature impact toughness were rather insensitive to the microphases. This may be attributed to the uniform distribution and isolation of relatively small martensite due to the fine interlocking character of the acicular ferrite microstructure. 相似文献
107.
108.
It is necessary to describe properly anisotropic material behavior for realistic numerical analyses of sheet metal forming processes. The implementation of many yield criteria in finite element analysis is very complicated. Various material tests are also required to determine yield function coefficients. Stress ratios and anisotropy coefficients are not constant during forming processes due to deformation induced anisotropy. This paper introduces a yield function using strain dependent plastic strain ratios and stress ratios. The main advantage is to fully utilize the data of uniaxial tensile tests. The described material behavior shows a significantly improved agreement with experimental data. 相似文献
109.
This paper proposes a miniature bending joint composed of serial rolling joints; it refers to the classification of small joints of other products and studies on surgical applications according to the structures and transmissions. To achieve this, a pulleyless rolling joint is introduced as a unit component and the basic design principle is established for the joint. A simple mechanism guarantees a smooth rolling contact using elastic fixtures. Underactuation, which prevents S-shaped curvature similar to buckling, is applied to drive the bending joint with a limited number of wire cables. Using a 1-DOF real-sized prototype, experiments were performed to measure the motion accuracy and payload capacity from various angles to evaluate the efficacy of an improved design that enhances the payload on the distal end. This novel joint is applicable to a wider variety of surgical tools and catheters relative to other candidates owing to its small constant curvature, reasonable payload capacity, and miniature size. 相似文献
110.
Sang‐Yoon Kim Jaemoon Yang Bongjune Kim Jungmin Park Jin‐Suck Suh Yong‐Min Huh Seungjoo Haam Jungho Hwang 《Small (Weinheim an der Bergstrasse, Germany)》2013,9(13):2325-2330
An electrohydrodynamic atomization (EHDA) system that generates an electrospray can achieve particle formation and encapsulation by accumulating an electric charge on liquid flowing out from the nozzle. A novel coaxial EHDA system for continuous fabrication of water‐stable magnetic nanoparticles (MNPs) is established, based on a cone‐jet mode of electrospraying. Systemic variables, such as flow rates from dual nozzles and inducing voltages, are controlled to enable the preparation of water‐soluble MNPs coated by polysorbate 80. The PEGylated MNPs exhibit water stability. The magnetic resonance imaging potential of these MNPs is confirmed by in vivo imaging using a gastric cancer xenograft mouse model. Thus, this advanced coaxial EHDA system demonstrates remarkable capabilities for the continuous encapsulation of MNPs to render them water‐stable while preserving their properties as imaging agents. 相似文献