全文获取类型
收费全文 | 245171篇 |
免费 | 21956篇 |
国内免费 | 11341篇 |
专业分类
电工技术 | 15564篇 |
技术理论 | 30篇 |
综合类 | 24986篇 |
化学工业 | 29211篇 |
金属工艺 | 10276篇 |
机械仪表 | 12685篇 |
建筑科学 | 38624篇 |
矿业工程 | 14101篇 |
能源动力 | 8777篇 |
轻工业 | 16684篇 |
水利工程 | 12258篇 |
石油天然气 | 12476篇 |
武器工业 | 3483篇 |
无线电 | 15623篇 |
一般工业技术 | 19316篇 |
冶金工业 | 12175篇 |
原子能技术 | 1836篇 |
自动化技术 | 30363篇 |
出版年
2024年 | 1223篇 |
2023年 | 3387篇 |
2022年 | 6332篇 |
2021年 | 8122篇 |
2020年 | 7997篇 |
2019年 | 6068篇 |
2018年 | 5706篇 |
2017年 | 7171篇 |
2016年 | 8495篇 |
2015年 | 9278篇 |
2014年 | 16769篇 |
2013年 | 14633篇 |
2012年 | 17720篇 |
2011年 | 19531篇 |
2010年 | 14554篇 |
2009年 | 14814篇 |
2008年 | 13549篇 |
2007年 | 16387篇 |
2006年 | 14698篇 |
2005年 | 12861篇 |
2004年 | 10645篇 |
2003年 | 9243篇 |
2002年 | 7575篇 |
2001年 | 6180篇 |
2000年 | 5259篇 |
1999年 | 4117篇 |
1998年 | 2982篇 |
1997年 | 2597篇 |
1996年 | 2119篇 |
1995年 | 1755篇 |
1994年 | 1470篇 |
1993年 | 1049篇 |
1992年 | 863篇 |
1991年 | 593篇 |
1990年 | 513篇 |
1989年 | 469篇 |
1988年 | 266篇 |
1987年 | 206篇 |
1986年 | 177篇 |
1985年 | 202篇 |
1984年 | 149篇 |
1983年 | 122篇 |
1982年 | 74篇 |
1981年 | 83篇 |
1980年 | 99篇 |
1979年 | 45篇 |
1978年 | 24篇 |
1977年 | 25篇 |
1964年 | 33篇 |
1959年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Human facial gestures often exhibit such natural stochastic variations as how often the eyes blink, how often the eyebrows and the nose twitch, and how the head moves while speaking. The stochastic movements of facial features are key ingredients for generating convincing facial expressions. Although such small variations have been simulated using noise functions in many graphics applications, modulating noise functions to match natural variations induced from the affective states and the personality of characters is difficult and not intuitive. We present a technique for generating subtle expressive facial gestures (facial expressions and head motion) semi‐automatically from motion capture data. Our approach is based on Markov random fields that are simulated in two levels. In the lower level, the coordinated movements of facial features are captured, parameterized, and transferred to synthetic faces using basis shapes. The upper level represents independent stochastic behavior of facial features. The experimental results show that our system generates expressive facial gestures synchronized with input speech. 相似文献
12.
F Javier Benítez Ana I Leal Francisco J Real Juan L Acero Gloria Roldán 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(3):309-316
BACKGROUND: The first stage of the cork industrial process generates great volumes of wastewater with moderate to high organic pollutant content that must be purified using different procedures, such as filtration by membranes. RESULTS: The tangential filtration of these wastewaters was studied using two different laboratory equipments. In the first one, three ultrafiltration (UF) membranes were tested, with molecular weight cut‐off (MWCO) 100 kDa and 30 kDa, and two operating modes were used: total recycling of permeate and retentate streams, and in continuous mode, without recycling both streams. In the total recycling UF experiments, the influence of the operating variables on the permeate flux was first established. The effectiveness of the different membranes was determined by evaluating the rejection coefficients for several parameters that measure the global pollutant content of the effluent. The values found for these rejection coefficients were in the following order: ellagic acid and color > absorbance at 254 nm > tannic content > COD (chemical oxygen demand). In the continuous mode experiments, the fouling mechanism for each membrane was established by fitting the experimental data to various filtration fouling models given in the literature. The operating mode in the second equipment was batch concentration, and additional experiments were carried out with an UF membrane (2 kDa), and with a NF membrane (with MWCO in the range 150–300 Da). CONCLUSIONS: The three operating modes tested provided different rejection levels of organic matter; among them, the most effective procedure tested was batch concentration mode using a NF membrane. Copyright © 2007 Society of Chemical Industry 相似文献
13.
提出了基于压电技术的微操作系统的自动标定方法,采用混合式步进电机直接驱动的宏动平台,实现系统大行程宏动定位,安装在宏动平台上的压电陶瓷驱动的微动平台和精密光栅,实现亚微米级的分辨率和定位精度,通过以上两部分实现定位机构的全闭环反馈控制,采用显微视觉反馈获取微动台操作器在图像中的位置信息进行标定。实验结果表明:系统的动态和稳定性能良好,自动标定运算速度快,运行速度达到11 frame/s,实现了对系统的精确标定,标定精度达到0.1μm。 相似文献
14.
This study develops a mathematical model for coupled heat and mass transfer in an unsaturated porous slab exposed to a flowing hot gas. Effects of the initial saturation conditions on associated variables, i.e., total pressure, temperature, moisture content, and multiphase flow, are studied. The Newton-Raphson method based on a finite volume technique is applied. This study emphasizes the influence of initial saturation level and gravitational effect in heat and multiphase flow phenomena associated with this system. Gravity enhances the downward flow of liquid within the porous slab. Pressure buildup occurs near the interface between the wet and the dry zone. However, it appears that the order of magnitude to the total pressure is small. This study explains the fundamental mechanism of multiphase flow that involves heat and mass transfer in a heated unsaturated porous slab. 相似文献
15.
Joel P. Martin J. Edward Swan II Robert J. Moorhead II Zhanping Liu Shangshu Cai 《Computer Graphics Forum》2008,27(3):991-998
We present the results from a user study looking at the ability of observers to mentally integrate wind direction and magnitude over a vector field. The data set chosen for the study is an MM5 (PSU/NCAR Mesoscale Model) simulation of Hurricane Lili over the Gulf of Mexico as it approaches the southeastern United States. Nine observers participated in the study. This study investigates the effect of layering on the observer's ability to determine the magnitude and direction of a vector field. We found a tendency for observers to underestimate the magnitude of the vectors and a counter‐clockwise bias when determining the average direction of a vector field. We completed an additional study with two observers to try to uncover the source of the counter‐clockwise bias. These results have direct implications to atmospheric scientists, but may also be able to be applied to other fields that use 2D vector fields. 相似文献
16.
17.
A. F. Kurbatskii 《High Temperature》2004,42(1):79-87
The difference in the turbulent diffusion between the active (heat) and passive (mass) scalars in a thermally stably stratified medium is investigated. The axisymmetric problem is treated on the formation of a turbulent circulation flow above a heated disk and on the turbulent diffusion of a passive scalar (impurity) from a continuous surface source in a stably stratified medium. The results indicate that the thermal stratification causes appreciable differences in the coefficients of turbulent transfer between the active (heat) and passive (mass) scalars. This means that the assumption of the identity of the coefficient of turbulent diffusion of heat and mass, employed in conventional models of turbulence, produces significant errors in estimating the heat and mass transfer in a thermally stably stratified medium. 相似文献
18.
ETRⅠ-30调速器是瑞士爱舍维斯工厂生产的具有PID调节规律的电液调速器。本文对其液压控制系统作了较详细的介绍,供有关人员参考。 相似文献
19.
We analyze specific features of the design of equipment used for mechanical testing of sheet structural materials under the conditions of biaxial static, cyclic, or dynamic loading. We propose original solutions of the problems related to the fatigue testing of crosslike specimens performed without using complex hydraulic systems and their dynamic testing carried out by using very simple testing machines for uniaxial tension–compression. 相似文献
20.
Storozhuk V. N. Romashchenko V. A. Lepikhin P. P. Zhurakhovskii S. V. 《Strength of Materials》2002,34(3):300-304
Large deflections of pulse-loaded elliptic and round plates made of hardenable elastoplastic materials are investigated analytically using an energy-based approach. Formulas that are convenient for engineering design have been derived. 相似文献