全文获取类型
收费全文 | 233007篇 |
免费 | 28067篇 |
国内免费 | 19234篇 |
专业分类
电工技术 | 19218篇 |
技术理论 | 11篇 |
综合类 | 25708篇 |
化学工业 | 21942篇 |
金属工艺 | 9517篇 |
机械仪表 | 17733篇 |
建筑科学 | 28578篇 |
矿业工程 | 11021篇 |
能源动力 | 10345篇 |
轻工业 | 10370篇 |
水利工程 | 12544篇 |
石油天然气 | 16993篇 |
武器工业 | 3812篇 |
无线电 | 16200篇 |
一般工业技术 | 20660篇 |
冶金工业 | 8769篇 |
原子能技术 | 2661篇 |
自动化技术 | 44226篇 |
出版年
2024年 | 1109篇 |
2023年 | 3250篇 |
2022年 | 6505篇 |
2021年 | 7630篇 |
2020年 | 8361篇 |
2019年 | 6929篇 |
2018年 | 6599篇 |
2017年 | 8387篇 |
2016年 | 9446篇 |
2015年 | 9903篇 |
2014年 | 14632篇 |
2013年 | 14819篇 |
2012年 | 17452篇 |
2011年 | 18616篇 |
2010年 | 14247篇 |
2009年 | 14396篇 |
2008年 | 13750篇 |
2007年 | 16163篇 |
2006年 | 14427篇 |
2005年 | 12544篇 |
2004年 | 10397篇 |
2003年 | 8887篇 |
2002年 | 7298篇 |
2001年 | 6149篇 |
2000年 | 5234篇 |
1999年 | 4101篇 |
1998年 | 3427篇 |
1997年 | 2807篇 |
1996年 | 2572篇 |
1995年 | 2216篇 |
1994年 | 1814篇 |
1993年 | 1214篇 |
1992年 | 1046篇 |
1991年 | 788篇 |
1990年 | 647篇 |
1989年 | 551篇 |
1988年 | 341篇 |
1987年 | 238篇 |
1986年 | 182篇 |
1985年 | 172篇 |
1984年 | 141篇 |
1983年 | 72篇 |
1982年 | 88篇 |
1981年 | 71篇 |
1980年 | 117篇 |
1979年 | 92篇 |
1964年 | 40篇 |
1959年 | 61篇 |
1956年 | 30篇 |
1955年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
V. A. Kazakov 《Measurement Techniques》2004,47(5):494-499
A method of measuring the current–voltage characteristics of nonlinear components is proposed, which involves applying a sinusoidal voltage to the object being measured, finding the Fourier spectrum to read out the output current, and a calculation using the spectrum of the coefficients of the expansion of the measured characteristic in Chebyshev polynomials. The properties of the Hammerstein–Chebyshev model are considered, a block diagram of a measuring instrument is presented, and recommendations are made for minimizing the systematic errors due to approximating their characteristics by Chebyshev polynomials. 相似文献
993.
Co-evolution as a computational and cognitive model of design 总被引:6,自引:0,他引:6
Co-evolutionary design has been developed as a computational model that assumes two parallel search spaces: the problem space
and the solution space. The design process iteratively searches each space using the other space as the basis for a fitness
function when evaluating the alternatives. Co-evolutionary design can also be developed as a cognitive model of design by
characterizing the way in which designers iteratively search for a design solution, making revisions to the problem specification.
This paper presents the computational model of co-evolutionary design and then describes a protocol study of human designers
looking for evidence of co-evolution of problem specifications and design solutions. The study shows that co-evolutionary
design is a good cognitive model of design and highlights the similarities and differences between the computational model
and the cognitive model. The results show that the two kinds of co-evolutionary design complement each other, having strengths
in different aspects of the design process.
Electronic Publication 相似文献
994.
995.
996.
基于感知器的快速彩色图像无损压缩算法 总被引:2,自引:0,他引:2
针对彩色图像像素和颜色分量之间存在的相关性,将神经网络中的感知器技术引入彩色图像的无损压缩算法中,提出了一种新的预测模型。应用感知器的自学习和自适应能力,对预测值进行自适应调整,使算法在运行过程中具有很小的预测残差并具有较小的动态范围。同时应用颜色空间变换来减小颜色分量间的相关性。相对于新的国际标准JPEG—LS,这种预测模型具有较低的计算复杂性。对比实验结果说明,这种算法的性能明显优于传统算法,在压缩比损失很小的前提下,其执行速度高于JPEG—LS。 相似文献
997.
1 IntroductionWiththerapiddevelopmentofInternetandmobilecommunications,theresearchonwirelessmobilenetworkshasbecomethenewhotspotinin formationtechnologyfield .Asweknow ,mobileterminals (mobilephone,forexample)arethetooltohelppeopletoaccessanyinformationtheyneedbyanymediaatanytimeandanywhere .However,itissometimesdifficultformobileterminalstoplaysucharolebecauseofthelimitationssuchaslimitedca pacity ,lowpower,andinconvenienceinoperating .So,peoplehopetofindanotherwaytoaccessnet workinformatio… 相似文献
998.
环境因子的定义及研究现状 总被引:12,自引:0,他引:12
胡斌 《太赫兹科学与电子信息学报》2003,1(1):88-92
从普遍接受的三个基本假设出发,讨论环境因子的定义和失效机理不变的约束条件,重点综述环境因子的研究现状和常用方法,并探讨引入反应论模型解决环境因子预测问题的可能途径。 相似文献
999.
The effect of reducing the reactor air pressure on the morphology of spray dried magnesium sulphate powders is investigated, experimentally. A reactor, capable of drying and pyrolyzing solution sprays at low pressures, is designed and manufactured. A vibrating mesh nebulizer is employed to generate the spray. Four different pressures, starting from 60 Torr to the atmospheric pressure, and two different reactor air temperatures of 130°C and 420°C, are considered. In addition, two different concentrations of magnesium sulphate solutions are tested. The results are explained based on the effect of reactor air pressure on the droplet evaporation rate. 相似文献
1000.
J.V. Lobato N. Sooraj Hussain C.M. Botelho A.C. Maurício A. Afonso J.D. Santos 《Thin solid films》2006,515(1):362-367
Synthetic bone grafts have been developed to provide an alternative to autografts and allografts. Bonelike® is a patented synthetic osteoconductive bone graft that mimics the mineral composition of natural bone. In the present preliminary animal studies a user-friendly version of synthetic bone graft Bonelike® have been developed by using a resorbable matrix, Floseal®, as a vehicle and raloxifene hydrochloride as a therapeutic molecule, that is known to decrease osteoclast activity and therefore enhanced bone formation. From histological and scanning electron microscopy evaluations, the use of Bonelike® associated with Floseal® and raloxifene hydrochloride showed that new bone was rapidly apposed on implanted granules and also that the presence of the matrix and therapeutic molecule does not alter the proven highly osteoconductivity properties of Bonelike®. Therefore, this association may be one step-forward for the clinical applications of Bonelike® scaffolds since it is much more easy-to-handle when compared to granular materials. 相似文献