全文获取类型
收费全文 | 45066篇 |
免费 | 3866篇 |
国内免费 | 37篇 |
专业分类
电工技术 | 1547篇 |
综合类 | 414篇 |
化学工业 | 14255篇 |
金属工艺 | 710篇 |
机械仪表 | 960篇 |
建筑科学 | 1531篇 |
矿业工程 | 219篇 |
能源动力 | 646篇 |
轻工业 | 7559篇 |
水利工程 | 438篇 |
石油天然气 | 192篇 |
武器工业 | 1篇 |
无线电 | 1479篇 |
一般工业技术 | 7420篇 |
冶金工业 | 5640篇 |
原子能技术 | 94篇 |
自动化技术 | 5864篇 |
出版年
2023年 | 896篇 |
2022年 | 642篇 |
2021年 | 1414篇 |
2020年 | 1348篇 |
2019年 | 1281篇 |
2018年 | 1823篇 |
2017年 | 1640篇 |
2016年 | 1900篇 |
2015年 | 1757篇 |
2014年 | 1993篇 |
2013年 | 3780篇 |
2012年 | 2407篇 |
2011年 | 2076篇 |
2010年 | 2112篇 |
2009年 | 2070篇 |
2008年 | 1646篇 |
2007年 | 1489篇 |
2006年 | 1000篇 |
2005年 | 876篇 |
2004年 | 787篇 |
2003年 | 744篇 |
2002年 | 572篇 |
2001年 | 470篇 |
2000年 | 351篇 |
1999年 | 426篇 |
1998年 | 2110篇 |
1997年 | 1347篇 |
1996年 | 937篇 |
1995年 | 593篇 |
1994年 | 476篇 |
1993年 | 555篇 |
1992年 | 255篇 |
1991年 | 196篇 |
1990年 | 220篇 |
1989年 | 237篇 |
1988年 | 225篇 |
1987年 | 239篇 |
1986年 | 244篇 |
1985年 | 243篇 |
1984年 | 234篇 |
1983年 | 212篇 |
1981年 | 269篇 |
1980年 | 228篇 |
1979年 | 198篇 |
1977年 | 255篇 |
1976年 | 356篇 |
1975年 | 228篇 |
1974年 | 213篇 |
1973年 | 397篇 |
1972年 | 214篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
105.
H. Maurer O. Univ.-Prof. Dr. phil. 《e & i Elektrotechnik und Informationstechnik》2003,120(11):411-413
In this article it is argued that in ten years’ time personal computers as we know them now won’t exist anymore — all their functions will by then be integrated in mobiles which will be our steady companions. As such, mobiles will change our lives to an enormous extent. Technology as well as consequences will be discussed in this paper. 相似文献
106.
107.
V. Ocelík V. Z. Bengus E. B. Korolkova K. Csach J. Miškuf P. Duhaj 《Journal of Materials Science》1991,26(24):6699-6705
The fracture stress and the critical stress intensity factor of the Fe40Ni40B20 amorphous metallic ribbons 20 μm thick were measured in the temperature range 4.2–300 K and at deformation rates from 3.3×10−6 to 1.25×10−3 m−1 with the aim to obtain more information on the condition for the onset and development of the inhomogeneous plastic deformation
and fracture. 相似文献
108.
In this paper, a new approach for powder cold compaction simulations is presented. A density-dependent plastic model within
the framework of finite strain multiplicative hyperelastoplasticity is used to describe the highly nonlinear material behaviour;
the Coulomb dry friction model is used to capture friction effects at die-powder contact; and an Arbitrary Lagrangian–Eulerian
(ALE) formulation is used to avoid the (usual) excessive distortion of Lagrangian meshes caused by large mass fluxes. Several
representative examples, involving structured and unstructured meshes are simulated. The results obtained agree with the experimental
data and other numerical results reported in the literature. It is shown that, contrary to other Lagrangian and adaptive h-remeshing approaches recently reported for this type of problems, the present approach verifies the mass conservation principle
with very low relative errors (less than 1% in all ALE examples and exactly in the pure Lagrangian examples). Moreover, thanks
to the use of an ALE formulation and in contrast with other simulations, the presented density distributions do not present
spurious oscillations.
Received: 20 March 2002 / Accepted: 15 October 2002
The partial financial support of the Ministerio de Ciencia y Tecnología (grant number DPI 2001-2204) is gratefully acknowledged. 相似文献
109.
Jefferson Fabrício Cardoso Lins Hugo Ricardo Z. Sandim Hans-Jürgen Kestenbach 《Journal of Materials Science》2007,42(16):6572-6577
The present paper reports the experimental results on the microstructural and textural characterization of a hot-rolled IF
steel. The IF steel was hot-rolled in multiple passes in the austenitic field (1,070 °C) followed by air-cooling. SEM, TEM,
and LOM were used to image the microstructure of the material. The global texture was determined by X-ray diffraction (XRD)
technique. The mesotexture of selected regions was investigated by electron backscatter diffraction (EBSD). Results show the
presence of a diffuse (nearly random) and weak texture in the hot-band that consists of recrystallized polygonal grains and
subgrains. The fraction of boundaries with misorientations comprised in the interval 2° ≤ ψ < 15° was found to be lower than
5%. It can be concluded that these low angle boundaries and the presence of subgrains can be associated to the existence of
a few areas softened by recovery during or after hot rolling in austenitic field. 相似文献
110.
J. Gegner Priv.‐Doz. Dr. W. Nierlich M. Brückner 《Materialwissenschaft und Werkstofftechnik》2007,38(8):613-623
Due to clearly distinguishable damage symptoms, it is differentiated between the surface and sub‐surface failure mode of rolling bearings. Material states red out by X‐ray diffraction (XRD) residual stress measurements point to a variety of loading conditions especially at raceway surfaces that are associated with several competing failure mechanisms. The corresponding lifetime reduction can range from the lower fatigue strength region to material ratcheting in extreme cases. Relevant position of the microstructural changes and nature of the failure mechanisms are characterized. The time alteration of the XRD material parameters measured at or near the surface and at the depth of the maximum equivalent stress correlates, in a different manner, with the statistical parameter of the 10 % bearing life. Both failure modes are illustrated by concrete examples. Contaminated lubricant and boundary lubrication, which represent practically important surface‐induced failures, are discussed in more detail. Gray staining, i.e. shallow pitting, often occurs without distinct indication of global material aging by means of XRD characteristics. Here, scanning electron microscopy observations and electron microprobe analyses point to corrosion fatigue as acting surface failure mechanism. The interaction between material and lubricant under complex loading regimes particularly of mixed friction and corrosion opens further failure research areas in the field of tribology. 相似文献