全文获取类型
收费全文 | 15486篇 |
免费 | 1841篇 |
国内免费 | 951篇 |
专业分类
电工技术 | 1590篇 |
技术理论 | 5篇 |
综合类 | 1287篇 |
化学工业 | 1428篇 |
金属工艺 | 797篇 |
机械仪表 | 1199篇 |
建筑科学 | 2903篇 |
矿业工程 | 1334篇 |
能源动力 | 681篇 |
轻工业 | 276篇 |
水利工程 | 757篇 |
石油天然气 | 522篇 |
武器工业 | 153篇 |
无线电 | 1167篇 |
一般工业技术 | 1640篇 |
冶金工业 | 683篇 |
原子能技术 | 225篇 |
自动化技术 | 1631篇 |
出版年
2024年 | 53篇 |
2023年 | 247篇 |
2022年 | 436篇 |
2021年 | 562篇 |
2020年 | 557篇 |
2019年 | 456篇 |
2018年 | 422篇 |
2017年 | 579篇 |
2016年 | 664篇 |
2015年 | 716篇 |
2014年 | 1249篇 |
2013年 | 980篇 |
2012年 | 1304篇 |
2011年 | 1260篇 |
2010年 | 987篇 |
2009年 | 944篇 |
2008年 | 786篇 |
2007年 | 977篇 |
2006年 | 818篇 |
2005年 | 720篇 |
2004年 | 572篇 |
2003年 | 486篇 |
2002年 | 429篇 |
2001年 | 445篇 |
2000年 | 303篇 |
1999年 | 268篇 |
1998年 | 188篇 |
1997年 | 179篇 |
1996年 | 129篇 |
1995年 | 131篇 |
1994年 | 117篇 |
1993年 | 51篇 |
1992年 | 46篇 |
1991年 | 44篇 |
1990年 | 41篇 |
1989年 | 26篇 |
1988年 | 22篇 |
1987年 | 19篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
高扭曲向列液晶显示器件的特性研究 总被引:2,自引:1,他引:1
本文研究了高扭曲向列液晶显示器件(HTNLCD)(扭曲角90~180°),此器件与扭曲向列液晶显示器件(TNLCD)相比较,能够增加液晶显示器件扫描行数并改善视角特性,其制造技术与TN器件相似,具有很大的应用价值。 相似文献
32.
33.
34.
提高大直径井眼机械钻速的几项措施 总被引:1,自引:0,他引:1
随着我国西部地区石油勘探开发的进展,5000-7000m的深探井所钻数量不断增多,套管程序增加,特别是大尺寸井眼所钻深度明显加大。由于国产大尺寸钻头结构单一、型号少,破岩机械能量和水力能量不足,在易斜井段目前尚无可靠的防斜保直措施,以及钻井液性能不适宜等原因,大尺寸井眼的钻这远远低于215.9mm井眼的钻速。据此,提出了几项可以提高大尺寸井眼钻速的措施:增加大尺寸钻头的种类,采用阶梯式扩眼钻头,强化钻井参数和水力参数,选用中速动力钻具,改善钻井液性能以及采用冲击旋转钻具等。 相似文献
35.
36.
Nowadays different kinds of double-skin facades are developed and used in new architectural projects. The aim of these facades is, on the one hand, to increase internal comfort and, on the other hand, to decrease energy consumption. In order to optimise the overall performance of the double-skin façades, their detailed behaviour needs to be better understood. The prediction of the airflow within the channel (between the two glazings) is very important for understanding of the double-skin facades behaviour, especially in summer conditions. A comprehensive modelling of a compact double-skin facade equipped with a venetian blind and forced ventilation is proposed here. The modelling is done using the CFD (computational fluid dynamics) approach to assess the air movement within the ventilated facade channel. Three-dimensional airflow is modelled using a homogeneous porous media representation, in order to reduce the size of the mathematical model. A parametric study is proposed here, analysing the impact of three parameters on the airflow development: slat tilt angle, blind position and air outlet position. The distance between the blind and the external glazing was found to have a major impact on the velocity profiles inside the double-skin facade channel. 相似文献
37.
38.
A. G. ATKINS Z. CHEN B. COTTERELL 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(1):67-77
In this paper, energy dissipation rate D vs. Δa curves in ductile fracture are predicted using a ‘conversion’ between loads, load‐point displacements and crack lengths predicted by NLEFM and those found in real ELPL propagation. The NLEFM/ELPL link was recently discovered for the DCB testpiece, and we believe it applies to other cracked geometries. The predictions for D agree with experimental results. The model permits a crack tip toughness R(Δa) which rises from Jc and saturates out when (if) steady state propagation is reached after a transient stage in which all tunnelling, crack tip necking and shear lip formation is established. JR is always greater than the crack tip R(Δa) and continues to rise even after R(Δa) levels off. The analysis is capable of predicting the usual D vs. Δa curves in the literature which have high initial values and fall monotonically to a plateau at large Δa. It also predicts that D curves for CCT testpieces should be higher than those for SENB/CT, as found in practice. The possibility that D curves at some intermediate Δa may dip to a minimum below the levelled‐off value at large Δa is predicted and confirmed by experiment. Recently reported D curves that have smaller initial D than the D‐values after extensive propagation can also be predicted. The testpiece geometry and crack tip R(Δa) conditions required to produce these different‐shaped D vs. Δa curves are established and confirmed by comparison with experiment. The energy dissipation rate D vs. Δa is not a transferable property as it depends on geometry. The material characteristic R(Δa) may be the ‘transferable property’ for scaling problems in ELPL fracture. How it can be deduced from D vs. Δa curves (and by implication, JR vs. Δa curves) is established. 相似文献
39.
大规格圆钢质量分析和控制 总被引:1,自引:0,他引:1
针对湘钢棒材厂生产大规格圆钢出现的表面质量问题,重点介绍了在成品轧机后采用U形辊道和立活套替换棍道;冷床输入辊道采用镶WT合金套;增设高压水除鳞装置;中间轧件尺寸精度控制等措施,成功的解决了大规格圆钢表面擦伤、“麻面”、尺寸超差等表面质量问题,产品质量显著提高。 相似文献
40.
The present paper is devoted to the analysis of the contact problems with Coulomb friction and large deformation between two hyperelastic bodies. One approach to separate the material nonlinearity and contact nonlinearity is presented. The total Lagrangian formulation is adopted to describe the geometrically nonlinear behavior. Nondifferentiable contact potentials are regularized by means of the augmented Lagrangian method. Numerical examples are carried out in two cases: rigid-deformable contact and deformable-deformable contact with large slips. The numerical results prove that the proposed approach is robust and efficient concerning numerical stability. 相似文献