全文获取类型
收费全文 | 7887篇 |
免费 | 811篇 |
国内免费 | 549篇 |
专业分类
电工技术 | 171篇 |
综合类 | 1126篇 |
化学工业 | 865篇 |
金属工艺 | 531篇 |
机械仪表 | 735篇 |
建筑科学 | 1454篇 |
矿业工程 | 284篇 |
能源动力 | 150篇 |
轻工业 | 412篇 |
水利工程 | 350篇 |
石油天然气 | 446篇 |
武器工业 | 68篇 |
无线电 | 383篇 |
一般工业技术 | 1566篇 |
冶金工业 | 164篇 |
原子能技术 | 106篇 |
自动化技术 | 436篇 |
出版年
2024年 | 24篇 |
2023年 | 90篇 |
2022年 | 153篇 |
2021年 | 177篇 |
2020年 | 218篇 |
2019年 | 202篇 |
2018年 | 201篇 |
2017年 | 239篇 |
2016年 | 278篇 |
2015年 | 298篇 |
2014年 | 414篇 |
2013年 | 481篇 |
2012年 | 498篇 |
2011年 | 524篇 |
2010年 | 384篇 |
2009年 | 399篇 |
2008年 | 413篇 |
2007年 | 577篇 |
2006年 | 526篇 |
2005年 | 422篇 |
2004年 | 374篇 |
2003年 | 312篇 |
2002年 | 294篇 |
2001年 | 253篇 |
2000年 | 250篇 |
1999年 | 201篇 |
1998年 | 167篇 |
1997年 | 142篇 |
1996年 | 133篇 |
1995年 | 103篇 |
1994年 | 91篇 |
1993年 | 83篇 |
1992年 | 52篇 |
1991年 | 59篇 |
1990年 | 33篇 |
1989年 | 35篇 |
1988年 | 30篇 |
1987年 | 28篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 17篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 2篇 |
1980年 | 9篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1974年 | 3篇 |
1951年 | 1篇 |
排序方式: 共有9247条查询结果,搜索用时 31 毫秒
41.
Measurements of the growth rate of roughness on a cathode surface can be used to study the physics of cathodic processes. But these growth rates are cell wide variables and they ordinarily depend on what is taking place at the anode as well as at the cathode. Our aim is to derive a simple condition under which the anode makes no contribution to the interpretation of growth rate measurements at the cathode.Our condition stems from the contribution of ion diffusion to the growth rate and it is satisfied for all non-small values of the wave number of a growing disturbance. This, together with the fact that surface tension is the only stabilizing factor and the fact that the surface tension coefficient multiplying the wave number is small, means that the anode ought not to be important for the fastest growing wave numbers.Once the effect of the anode is eliminated, the growth rate at the cathode can be expressed in a formula so simple that pencil and paper calculations are possible and this makes important questions in cell design easy to answer, e.g., is the growth rate diffusion controlled? 相似文献
42.
Strength reduction factors (SRFs) continue to play a key role in obtaining design forces from elastic design spectra (via
response modification factors) in ductility-based earthquake-resistant design. Despite several years of sustained research
efforts, it has not been conclusively shown how SRF for a given singledegree-of-freedom structural system depends on various
source and site parameters. A parametric study is carried out here for the explicit dependence of SRF spectrum (describing
variation of SRF with system period for a given ductility demand) on strong motion duration, earthquake magnitude, geological
site conditions, and epicentral distance in case of (non-degrading) elasto-plastic oscillators. For this, scaled response
spectra are considered for different combinations of earthquake magnitude, site conditions and epicentral distance, and SRF
spectra are generated from 1274 accelerograms recorded in western USA after making those compatible with each of these spectra.
It is shown that there is no clear and significant dependence of SRF spectrum on strong motion duration. Further, the parametric
dependence on earthquake magnitude, site conditions, and epicentral distance broadly conforms to the trends reported by earlier
investigations. In particular, this study confirms that the dependence of SRF spectra on earthquake magnitude should not be
ignored.
This paper has been contributed in honour of Professor R N Iyengar, Indian Institute of Science, on the occasion of his formal
retirement. 相似文献
43.
无键联接传动的特点及锥面弹性衬套设计和应用 总被引:5,自引:0,他引:5
无键联接在特殊行业和工况中是键联接传递动力和运动的有力补充,介绍了工程上应用的圆弧三边形型面联接、弹性环无键联接、圆柱面过盈联接等几种无键联接传动方式及其工作原理,并分析了各自的性能特点和应用情况。针对无键联接传动的特点、特殊行业和工况的应用实际,设计了锥面弹性衬套无键联接传动结构并介绍了其在工程中的实际应用。 相似文献
44.
Patterns in the solidification of a pure material are dealt with in this article. Results, deduced from a simple model based on heat conduction in the two phases and the effect of surface tension on the equilibrium temperature at the moving front, present a guide for experimental work. By introducing far-field conditions imitating what can be achieved in an experiment, we explain how the depths of the phases and the width of the container influence the patterns that can be seen if one advances the control variable to the critical point and then just beyond. Our new result is the existence of a third critical point. It occurs at small wave numbers and it is independent of surface tension. It appears because we take the depths of the phases into account. These depths are input values that offer the possibility of controlling crest-to-trough conduction, stabilizing in the solid, destabilizing in the liquid. The new critical point, and the patterns attending its appearance, can be found in cells of easily attainable widths. 相似文献
45.
A. A. Karabutov V. A. Makarov V. L. Shkuratnik E. B. Cherepetskaya 《Journal of Mining Science》2003,39(4):323-330
Using the transfer function method as a base, the analytical relations are obtained, as well as the main parameters are calculated for the ultrasonic impulses of longitudinal, transverse, and the Rayleigh waves excited in geomaterials by laser emission. 相似文献
46.
The numerical simulation of comparative elastohydrodynamic lubrication between axisymmetrical and 3D elastic approaches on the radial lip seals is presented in order to determine the 3D effect of the elastic aspect of the seal lip. Indeed, the consideration of 3D model in other words the circumferential variation of the lip elastic deformation indicated a difference in the deformation distribution of the lip compared to the axisymmetrical approach. Consequently, the results show that the presence of the circumferential variation of the seal lip deformation has a significant effect on the pumping rate values. 相似文献
47.
本文用超声浸液法测量了单向纤维增强热塑性树脂及其半互穿聚合物网络(Semi-IPN)复合材料的杨氏模量、剪切模量、泊松比和内耗,并对不同树脂、纤维和Semi-IPN中共混组成比对弹性性能的影响进行了研究。 相似文献
48.
弹性直杆热膨胀状态下的非线性振动 总被引:30,自引:2,他引:28
以KBM法为基础,引进谐波平衡观点来研究弹性直杆热膨胀状态下的非线性振动.通过实例计算表明,弹性直杆热膨胀状态下非线性振动的频率对温度的变化非常敏感. 相似文献
49.
50.
本文阐述铁铝酸盐自应力混凝土的主要物理力学特征.研究了限制膨胀应变与配筋率之间的定量函数关系.通过正交试验和方差分析,确定了复合外加剂对其性能的影响.针对其在自应力管中的应用,提出多层中空圆柱理论计算模型,按弹性理论计算出自应力管初始应力分布规律.对比以前的线性理论计算误差,给出相应的修正系数.本文对类似的自应力混凝土,具有普遍的指导意义. 相似文献