全文获取类型
收费全文 | 41136篇 |
免费 | 4101篇 |
国内免费 | 2972篇 |
专业分类
电工技术 | 1866篇 |
综合类 | 3786篇 |
化学工业 | 6250篇 |
金属工艺 | 2138篇 |
机械仪表 | 1657篇 |
建筑科学 | 4825篇 |
矿业工程 | 1825篇 |
能源动力 | 1619篇 |
轻工业 | 3321篇 |
水利工程 | 1419篇 |
石油天然气 | 2321篇 |
武器工业 | 436篇 |
无线电 | 5182篇 |
一般工业技术 | 6381篇 |
冶金工业 | 2149篇 |
原子能技术 | 943篇 |
自动化技术 | 2091篇 |
出版年
2024年 | 201篇 |
2023年 | 698篇 |
2022年 | 1209篇 |
2021年 | 1443篇 |
2020年 | 1500篇 |
2019年 | 1384篇 |
2018年 | 1199篇 |
2017年 | 1561篇 |
2016年 | 1523篇 |
2015年 | 1584篇 |
2014年 | 2321篇 |
2013年 | 2481篇 |
2012年 | 2758篇 |
2011年 | 2996篇 |
2010年 | 2281篇 |
2009年 | 2370篇 |
2008年 | 2208篇 |
2007年 | 2656篇 |
2006年 | 2437篇 |
2005年 | 2011篇 |
2004年 | 1736篇 |
2003年 | 1524篇 |
2002年 | 1348篇 |
2001年 | 1057篇 |
2000年 | 987篇 |
1999年 | 780篇 |
1998年 | 619篇 |
1997年 | 582篇 |
1996年 | 486篇 |
1995年 | 420篇 |
1994年 | 360篇 |
1993年 | 303篇 |
1992年 | 239篇 |
1991年 | 200篇 |
1990年 | 170篇 |
1989年 | 137篇 |
1988年 | 102篇 |
1987年 | 65篇 |
1986年 | 45篇 |
1985年 | 32篇 |
1984年 | 36篇 |
1983年 | 22篇 |
1982年 | 19篇 |
1981年 | 12篇 |
1980年 | 18篇 |
1979年 | 23篇 |
1965年 | 5篇 |
1963年 | 5篇 |
1959年 | 9篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
An analytical method is presented for calculating the resonant frequency andQ-factor of a superconducting dielectric disk resonator operating in millimeter-wave regime with whispering-gallery mode. Resonant frequency shift due to the optical generation of quasi-particles in superconducting film is investigated as a function of photon flux. An optically tunable resonant frequency of about 500 MHz is estimated, and good agreement is found between numerical results and experimental ones. 相似文献
32.
《Drying Technology》2007,25(3):475-481
A method to minimize twist has been investigated; i.e., drying the boards in a pre-twisted position. It has been found that Norway spruce boards can be deformed toward straightness by this method. The force exerted by a board on its holders during drying in a pre-twisted position has been measured. When the variation in torsional stiffness as a function of temperature and moisture content is accounted for, it is found that a creep deformation of the board occurs both during the drying phase and the cooling phase. In addition to mechano-sorptive creep, a deformation released by a change in temperature also seems to occur. 相似文献
33.
对不同能量、不同质量数、不同初始条件的入射束和有无空间电荷效应的离子束流在高梯度加速管中的传输进行了计算,并讨论了一些影响加速管聚焦作用的主要因素,计算结果与实际情况相符。 相似文献
34.
A modified CIECAM02 colour appearance model, named CIECAM02‐m2, is proposed to enable CIECAM02 to predict the simultaneous contrast effect. The structure of the CIECAM02‐m2 is a development from CIECAM02, and contains two different procedures for modifying the reference white; one is for lightness and the other is for hue. The model was tested using a data set accumulated in this study and the LUTCHI data. The CV values for three colour attributes between predictions and experimental data were used to evaluate the accuracy of the model. The low CV values obtained show the performance of the CIECAM02‐m2 model to predict the simultaneous contrast effect satisfactorily. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 121 – 129, 2007 相似文献
35.
The feasibility of a new alloy design concept utilizing the principle of ‘tungsten bronze effect’ is critically evaluated for the development of metallic bipolar plates for proton exchange membrane fuel cell (PEMFC). An austenitic stainless steel (ASS) is modified with W and La to improve the stability of the passive film in an acidic environment as well as to reduce the contact resistance by the tungsten bronze effect. The experimental ASS containing W and La was evaluated in a simulated PEMFC environment of H3PO4 and H2SO4 solutions at 80 °C, and the electrical property was evaluated by performing a contact resistance test. The test results show that the ASS modified with W and La has good passive film stability for corrosion resistance and low contact resistance. The X-ray photoelectron spectroscopy (XPS) analysis clearly suggests the possibility of the tungsten bronze effect from the change in valency state of W6+ to W5+ in the passive film formed on the modified ASS. The feasibility of a new alloy design concept utilizing the ‘tungsten bronze effect’ is well demonstrated; however, more study is highly required for the development of metallic bipolar plates of PEMFC. 相似文献
36.
混合溶剂对Ru(Ⅳ)萃取的研究 总被引:2,自引:0,他引:2
一、前言 在一定浓度盐酸介质中,Ru(Ⅳ)以RuCl_6~(2-)络阴离子状态存在,可被C类溶剂TOA(三辛胺)以离子缔合机制定量地萃入有机相。由实验得到在相同条件下,TOA对Ru(Ⅳ)的萃取率随稀释剂介电常数的增加而下降。 相似文献
37.
The paramagnetic Meissner effect (PME) was observed on the field-cooled M-T curvesof melt-textured Y0.99Nd0.01Ba2Cu3O7-y in applied magnetic fields from 1kOe toJ0kOe. In the magnetic field below 1kOe, the sample undergoes the typical transi-tion from the normal state to the superconducting state when it was cooled down. Theapplied magnetic fields in which the PME occurs, are very high compared with thefields reported in literatures. We propose that the occurrence of the PME may be dueto a phase transition of flux vortices in the superconductors. 相似文献
38.
一种新的位错运动理论及对材料动态力学行为的描述 总被引:3,自引:0,他引:3
通过对位错在晶格内运动的动力学过程的全面分析。本文提出了一种考虑到粘性阻尼效应和热激活的位错集体运动统一理论。其特点是可用一简单的方程对从低速到高速运动的大量位错的平均行为进行统一描述。对KCl晶体的典型实验怕拟合发现理论描述与实验结果相当一致。 相似文献
39.
A simple transient performance of floating cum tilted-wick type solar still has been presented by incorporating the effects of water flowing over a glass cover, heat capacity of tilted-wick water surface and floating-wick water surface. Explicit expressions for flowing water, glass, tilted-wick water surface and floating-wick water surface temperature and efficiency of the system have been derived. Numerical calculations have been carried out for a typical day in the month of March 2004. The relative standard deviations between the numerical and experimental results of different temperature components of the proposed still have been found. The results indicate that the relative standard deviations between theoretical and experimental results are less than 8% (glass cover), 2% (tiltedwick water surface), 1% (floating-wick water surface) and 2% (flowing water at the lower end of the glass cover) an average for the working hours of the day. Moreover, based on the numerical results, the following conclusions have been drawn: (i) glass cover temperature decreases significantly; (ii) the effect of water flowing over the glass cover has a fascinating effect on the production of distillate output during peak sunny hours; (iii) water flow rate of 1.5 m/s is optimum, and beyond it the efficiency decreases. Experimental investigations have been performed at Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore, India. 相似文献
40.
Experimental results are presented of wall effect for the slow motion of spheres in elastic, constant-viscosity liquids. The results are correlated in terms of diameter ratio for d/D < 0.3, and Weissenberg number We < 5. Weissenberg number is defined as We = 2θVm/d, with θ the Maxwellian relaxation time (θ = N1/2τγ). The wall effect is found to be adequately described by Newtonian expressions for small Weissenberg number, We < 0.01. For larger values of the Weissenberg number, We > 0.2, virtually no wall effect is discernible; the small effect observed is correlated by the wall factor expression The wall effect observed is ascribed to the influence of fluid elasticity alone, since all the fluids used were elastic to a greater or lesser extent, but showed no shear thinning. 相似文献