全文获取类型
收费全文 | 21858篇 |
免费 | 1216篇 |
国内免费 | 60篇 |
专业分类
电工技术 | 311篇 |
综合类 | 25篇 |
化学工业 | 4893篇 |
金属工艺 | 879篇 |
机械仪表 | 1298篇 |
建筑科学 | 426篇 |
矿业工程 | 6篇 |
能源动力 | 864篇 |
轻工业 | 1850篇 |
水利工程 | 91篇 |
石油天然气 | 16篇 |
无线电 | 3655篇 |
一般工业技术 | 4630篇 |
冶金工业 | 1541篇 |
原子能技术 | 291篇 |
自动化技术 | 2358篇 |
出版年
2024年 | 22篇 |
2023年 | 275篇 |
2022年 | 399篇 |
2021年 | 686篇 |
2020年 | 470篇 |
2019年 | 497篇 |
2018年 | 699篇 |
2017年 | 661篇 |
2016年 | 768篇 |
2015年 | 602篇 |
2014年 | 938篇 |
2013年 | 1389篇 |
2012年 | 1456篇 |
2011年 | 1789篇 |
2010年 | 1298篇 |
2009年 | 1331篇 |
2008年 | 1211篇 |
2007年 | 937篇 |
2006年 | 813篇 |
2005年 | 708篇 |
2004年 | 638篇 |
2003年 | 586篇 |
2002年 | 593篇 |
2001年 | 517篇 |
2000年 | 437篇 |
1999年 | 423篇 |
1998年 | 709篇 |
1997年 | 420篇 |
1996年 | 395篇 |
1995年 | 257篇 |
1994年 | 169篇 |
1993年 | 151篇 |
1992年 | 112篇 |
1991年 | 100篇 |
1990年 | 75篇 |
1989年 | 88篇 |
1988年 | 74篇 |
1987年 | 63篇 |
1986年 | 51篇 |
1985年 | 43篇 |
1984年 | 36篇 |
1983年 | 28篇 |
1982年 | 31篇 |
1981年 | 26篇 |
1980年 | 29篇 |
1979年 | 13篇 |
1977年 | 22篇 |
1976年 | 33篇 |
1975年 | 17篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Calculation of Mass Attenuation Coefficients of Beta Particles 总被引:1,自引:0,他引:1
Yi C.Y.; Han H.S.; Cho W.K.; Park U.J.; Jun J.S.; Chai H.S. 《Radiation protection dosimetry》1998,78(3):221-229
43.
Ha J.H. Kim S.W. Seol Y.S. Park H.K. Choi S.H. 《Semiconductor Manufacturing, IEEE Transactions on》1996,9(2):289-291
The plug loading effect occurring during the etchback of tungsten was investigated in a magnetically enhanced reactive ion etcher using SF 6/Ar mixtures. It was found that while the plug loading effect is independent of varying SF6/Ar flow rate ratio and magnetic field intensity, it is reduced under the condition of high selectivity of tungsten relative to TiN which was achieved at high chamber pressure and low RF power. It is proposed that when TiN is used as a glue layer, the W etch rate enhancement in the plug is mainly controlled by a local loading effect. Under the optimized etchback conditions the plug loss was successfully controlled without the tungsten residue left on severe topology 相似文献
44.
To determine the mechanism of measles virus-induced cell death, we studied the infection of Vero cells and monocytic cell lines with wild-type (Chicago-1) and vaccine (Edmonston) strains of measles virus. DNA fragmentation indicative of apoptosis was apparent by flow cytometry, agarose gel electrophoresis, and electron microscopy. Within syncytia, DNA strand breaks were demonstrated by end labeling with terminal transferase and then by visualization. 相似文献
45.
K.-H. Zum Gahr R. Telle B. Zimmerlin S.-H. Park 《Materialwissenschaft und Werkstofftechnik》1992,23(9):329-338
Influence of grain size on mechanical properties and dry oscillating sliding wear of Al2O3-ceramics Specimens with average grain sizes varying between about 0.8 μm and 12 μm were produced by cold isostatic pressing of high purity Al2O3-powder followed by sintering between 1300°C and 1700°C. Hardness, Young's modulus, bending strength and fracture toughness were measured as a function of average grain sizes. Tribological tests were carried out on the different microstructures at normal laboratory air and room temperature by using a ring-on-block tribometer. Experimental results showed the dependence of mechanical properties on grain size, hardness and bending strength obeying a Hall-Petch type relation, approximately. Coefficient of friction was relatively independent of grain size under the test conditions used. However, wear intensity increased substantially if a critical grain size was surpassed. This was due to a change in mechanisms of material removal which was confirmed by scanning electron microscopical studies of the worn surfaces. 相似文献
46.
47.
Experimental studies on the aerodynamic coupling effect on natural frequencies and flutter instability of rotating disks
are investigated in this paper. The experiments performed using a vacuum chamber and optical disks give two main results.
One is that the aerodynamic effect by surrounding air reduces the natural frequencies and critical speeds of the vibration
modes in pre-flutter regions. The other is that the natural frequency of the disk rotating at ambient atmospheric pressure
is equal to that in vacuum at the flutter onset speed where the disk experiences aero-induced flutter. In post-flutter regions,
the aerodynamic coupling between the disk and surrounding air increases the natural frequencies of the disk.
Received: 17 June 2002/Accepted: 7 October 2002
The work was supported by Grant No. R11-1997-042-090001-0 of the Center for Information Storage Devices designated by the
Korea Science & Engineering Foundation.
Paper presented at the 13th Annual Symposium on Information Storage and Processing Systems, Santa Clara, CA, USA, 17–18 June,
2002 相似文献
48.
The Error-in-Variables Model (EVM) applies to a large class of problems in parameter estimation in which there is error in all the variables. This property makes it of more general applicability than the widely used technique of ordinary Least Squares. While there is a voluminous literature on EVM there is nothing on a general method for designing experiments when EVM applies. In this paper we present an extension of the concept of D-optimality to provide such a general method. It is illustrated by applying it to the estimation of copolymer reactivity ratios and to fitting an ellipse. 相似文献
49.
Optical measurements of thermal diffusivity of a material 总被引:2,自引:0,他引:2
The measurement of thermal diffusivity of a material (in particular, a thin film) is important for various reasons, e.g., to predict the heat transfer in the solid subjected to a thermal process, to monitor surface composition or morphology, or to detect invisible subsurface defects like delaminations. This measurement can be done in a noncontact manner using various photothermal methods. Such methods typically involve pulsed heating of the surface by small amounts using a laser source; the decay of the surface temperature after this pulsed photothermal heating is then probed to provide the thermal diffusivity. Various probing methods have been developed in the literature, including the probing of reflection, refraction, and diffraction from the pulsed heated area, infrared thermal radiometry, and surface deformation. This paper provides an overview of such techniques and some examples of their applications. 相似文献
50.
Determining contributions of source-monitoring and inhibitory function to age-related forgetting has been an elusive goal for cognitive theorists. Five studies used a verbal working memory paradigm to examine mechanisms accounting for disproportionate retroactive interference (RI) experienced with adult aging. Participants distinguished studied target-word pairs from interfering pairs that were read aloud. Source-monitoring and inhibitory task components varied through manipulations of response requirements. RI effects were primarily due to source-monitoring failures rather than to inhibitory failures. Removing both source and inhibitory components eliminated age differences in RI. When source monitoring was emphasized, RI continued to be observed in all age groups but disproportionately for older adults. Process dissociation analyses of memory found recollection decreases and familiarity increases consistent with source failures. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献