全文获取类型
收费全文 | 12812篇 |
免费 | 1562篇 |
国内免费 | 917篇 |
专业分类
电工技术 | 833篇 |
技术理论 | 3篇 |
综合类 | 2025篇 |
化学工业 | 971篇 |
金属工艺 | 351篇 |
机械仪表 | 552篇 |
建筑科学 | 1335篇 |
矿业工程 | 929篇 |
能源动力 | 711篇 |
轻工业 | 627篇 |
水利工程 | 1410篇 |
石油天然气 | 696篇 |
武器工业 | 303篇 |
无线电 | 759篇 |
一般工业技术 | 1151篇 |
冶金工业 | 651篇 |
原子能技术 | 122篇 |
自动化技术 | 1862篇 |
出版年
2024年 | 42篇 |
2023年 | 153篇 |
2022年 | 382篇 |
2021年 | 446篇 |
2020年 | 502篇 |
2019年 | 418篇 |
2018年 | 390篇 |
2017年 | 491篇 |
2016年 | 579篇 |
2015年 | 546篇 |
2014年 | 837篇 |
2013年 | 840篇 |
2012年 | 969篇 |
2011年 | 952篇 |
2010年 | 750篇 |
2009年 | 796篇 |
2008年 | 697篇 |
2007年 | 854篇 |
2006年 | 726篇 |
2005年 | 594篇 |
2004年 | 511篇 |
2003年 | 396篇 |
2002年 | 356篇 |
2001年 | 297篇 |
2000年 | 280篇 |
1999年 | 232篇 |
1998年 | 166篇 |
1997年 | 140篇 |
1996年 | 125篇 |
1995年 | 128篇 |
1994年 | 106篇 |
1993年 | 81篇 |
1992年 | 70篇 |
1991年 | 57篇 |
1990年 | 56篇 |
1989年 | 47篇 |
1988年 | 43篇 |
1987年 | 27篇 |
1986年 | 26篇 |
1985年 | 17篇 |
1984年 | 15篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1979年 | 8篇 |
1968年 | 13篇 |
1966年 | 6篇 |
1965年 | 9篇 |
1964年 | 9篇 |
1963年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
The purpose of this paper is the modelling of the mechanical behaviour of an elastomeric material, through detailed experimental and numerical procedures, specific to large strains. The experimental technique is based on in-plane kinematics measurements using a speckle extensometer, from which the whole two-dimensional field of in-plane displacements is obtained by a digital image processing [Polymer (2002)]. This part of the work concerns the identification of the constitutive equation for a carbon black natural rubber (NR) vulcanizate. We start by quoting some theoretical considerations relative to rubber elasticity and stress-softening effect, which is the counterpart of the filler reinforcement. Then, we describe the experimental procedure and present data for both non-preconditioned and preconditioned samples. Next, the identification of the constitutive law parameters using a minimization algorithm is driven. Finally, we present the validation of the constitutive model, by its implementation into the finite element code SYSTUS and the numerical simulation of the response of a double edge notched tensile (DENT) specimen. 相似文献
42.
通过模型试验 ,对位于西安市东郊因采沙使河道破坏严重的灞河河段进行了复现试验和研究 ,并以此为依据 ,通过优化比较为设计部门提供了合理的橡胶坝坝址和坝座高程。在此基础上 ,又对建坝后橡胶坝对上下游冲淤变化的影响进行了试验研究和分析 ,解决了工程设计中的一些关键技术问题 相似文献
43.
Denis Rodrigue 《加拿大化工杂志》2002,80(2):289-292
Recently, the author (Rodrigue, 2001 a, b) proposed a generalized correlation for the steady rise of gas bubbles in uncontaminated viscous Newtonian fluids of infinite extent. It is the purpose of this note to show that this model can be modified for inelastic non‐Newtonian power‐law fluids. Using data taken from six different studies, it is shown that the modified model can predict quite nicely the bubble velocity for these non‐Newtonian inelastic fluids. 相似文献
44.
Zhang Sheng-ming Yangtze River Scientific Research Institute Wuhan Hubei P. R. China 《水动力学研究与进展(B辑)》1992,(2)
Through a series of model tests of five scales for 2-D free hydraulic jump, the da-ta of fluctuating pressure acting on the floor level within the hydraulic jump were obtained. Dur-ing the experiments, Froude number varied from 2.94 to 8.61, and Reynolds number rangedfrom 2×10~4 to 6×10~5. Experiment results indicate that the amplitude scale of fluctuating pres-sure is the length scale of model, i. e. P'=L, which agrees with gravity similarity law: Thefrequency scale of the fluctuating pressure is a unity i. e., f=1, which does not satisfy thegravity similarity law. 相似文献
45.
The equilibrium CO2 sorption isotherms and isobars for rubbery EVA containing various amounts of vinyl acetate (VA) over a wide pressure range 10-340 atm and 25-52 °C were investigated. The normalized CO2 sorption concentration (in cm3 (STP) CO2/mole VA) isotherms of these polymers as a function of pressure consisted of two distinct regions turning at near Pc. The normalized sorption isotherms in these two distinct regions could be fairly described by two respective power laws: C=KaPna for above Pc and C=kbPnb for below Pc. The normalized CO2 sorption isotherms were found to be about the same for four EVA samples having different VA contents for below Pc, suggesting that the sorption process at below Pc may be mainly driven by the presence of carbonyl groups. At above Pc, the degree of crystallinity of the polymer appeared to be a major factor to affect the sorption process, with the higher the degree of crystallinity, the lower the normalized CO2 sorption concentration in the polymer. The sorption isobars of the polymer as a function of temperature were governed by the interplay of density, viscosity, and diffusivity of CO2 depending on the pressure studied. 相似文献
46.
朱成宏 《勘探地球物理进展》2007,30(3):226-237
介绍了2006年SEG年会上所反映的各向异性研究的新进展,主要包括:提高速度分析精度的各向异性速度分析参数正交化方法;影响裂隙储层预测的地震波动力学与运动学特征差异分析;验证现行裂隙硬币理论模型可靠性的不规则裂隙有效弹性参数计算分析;提高计算效率的波场延拓各向异性参数参考值优选Lloyd算法;常见TTI介质不同成像方法试验效果的比较。 相似文献
47.
A generalized diffusion coefficient correlation for a binary system of liquids has been developed to represent the data for a wide range of temperatures. Detailed analysis shows that the proposed correlation fits the experimental measurements of diffusivity with the corresponding calculated values with an acceptable percentage error. 相似文献
48.
Theprecipitationofpro eutectoidferritefromausteniteiscontrolledbydiffusioninFe Calloys .Withtheassumptionthatthemigratinginterfaceisalwaysinlocalequilibrium ,earlyin 194 9,ZenerC[1] explainedthediffusionalgrowthofpro eutec toidferritebyusingtheFick’slaw .Since… 相似文献
49.
宜昌水文站是葛洲坝、三峡水利枢纽的设计依据站。葛洲坝水利枢纽动工修建和运行 ,对该站水位流量关系中低水部分产生了影响。探讨了该河段泄流能力的变化对葛洲坝水利枢纽设计洪水有无影响的问题。用1 967~ 1 999年实测资料对宜昌站以汛期平均水位为参数的水位流量关系曲线簇进行了检验 ,大部分年份最大日平均流量、3、7、1 5、30d洪量的偏差在± 4 %之间 ,说明曲线簇推流具有相当的精度。证明了宜昌河段中低水泄流能力的变化对葛洲坝水利枢纽设计流量和校核流量基本没有影响 相似文献
50.
Tai-Shang ChenJia-Ming Chern 《Chemical engineering science》2002,57(3):457-467
The network reduction technique and the Bodenstein approximation of quasi-stationary behavior of reaction intermediates were systematically applied to derive general yield ratio and rate equations for multi-cycle reaction networks in homogeneous catalysis. Dual-cycle reaction networks connected by a linear pathway, multi-cycle networks stemming from the same intermediate, and single-cycle with arbitrary number of pathways between two intermediates were considered. The general yield ratio and rate equations derived in this study are applicable for most enzymatic reactions and for homogeneous catalytic reactions. Examples of homogeneous catalysis were used to illustrate the application of the general yield ratio and rate equations for network elucidation. 相似文献