全文获取类型
收费全文 | 9832篇 |
免费 | 1170篇 |
国内免费 | 992篇 |
专业分类
电工技术 | 804篇 |
综合类 | 1452篇 |
化学工业 | 668篇 |
金属工艺 | 218篇 |
机械仪表 | 669篇 |
建筑科学 | 481篇 |
矿业工程 | 164篇 |
能源动力 | 248篇 |
轻工业 | 143篇 |
水利工程 | 396篇 |
石油天然气 | 338篇 |
武器工业 | 130篇 |
无线电 | 1107篇 |
一般工业技术 | 1165篇 |
冶金工业 | 146篇 |
原子能技术 | 85篇 |
自动化技术 | 3780篇 |
出版年
2024年 | 20篇 |
2023年 | 113篇 |
2022年 | 125篇 |
2021年 | 191篇 |
2020年 | 206篇 |
2019年 | 273篇 |
2018年 | 235篇 |
2017年 | 299篇 |
2016年 | 358篇 |
2015年 | 317篇 |
2014年 | 494篇 |
2013年 | 579篇 |
2012年 | 648篇 |
2011年 | 678篇 |
2010年 | 553篇 |
2009年 | 616篇 |
2008年 | 690篇 |
2007年 | 781篇 |
2006年 | 665篇 |
2005年 | 613篇 |
2004年 | 480篇 |
2003年 | 466篇 |
2002年 | 361篇 |
2001年 | 306篇 |
2000年 | 299篇 |
1999年 | 235篇 |
1998年 | 208篇 |
1997年 | 211篇 |
1996年 | 179篇 |
1995年 | 132篇 |
1994年 | 142篇 |
1993年 | 104篇 |
1992年 | 79篇 |
1991年 | 75篇 |
1990年 | 47篇 |
1989年 | 57篇 |
1988年 | 41篇 |
1987年 | 25篇 |
1986年 | 8篇 |
1985年 | 15篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1962年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
1.
In this paper, a new inverse identification method of constitutive parameters is developed from full kinematic and thermal field measurements. It consists in reconstructing the heat source field from two different approaches by using the heat diffusion equation. The first one requires the temperature field measurement and the value of the thermophysical parameters. The second one is based on the kinematic field measurement and the choice of a thermo-hyperelastic model that contains the parameters to be identified. The identification is carried out at the local scale, ie, at any point of the heat source field, without using the boundary conditions. In the present work, the method is applied to the challenging case of hyperelasticity from a heterogeneous test. Due to large deformations undergone by the rubber specimen tested, a motion compensation technique is developed to plot the kinematic and the thermal fields at the same points before reconstructing the heterogeneous heat source field. In the present case, the constitutive parameter of the Neo-Hookean model has been identified, and its distribution has been characterized with respect to the strain state at the surface of a cross-shaped specimen. 相似文献
2.
3.
Jean-Charles Passieux Robin Bouclier 《International journal for numerical methods in engineering》2019,119(6):453-468
Today, effective implementations of digital image correlation (DIC) are based on iterative algorithms with constant linear operators. A relevant idea of the classic finite element (or, more generally, global) DIC solver consists in replacing the gradient of the deformed state image with that of the reference image, so as to obtain a constant operator. Different arguments (small strains, small deformations, equality of the two gradients close to the solution, etc) have been given in the literature to justify this approximation, but none of them are fully accurate. Indeed, the convergence of the optimization algorithm has to be investigated from its ability to produce descent directions. Through such a study, this paper attempts to explain why this approximation works and what is its domain of validity. Then, an inverse compositional Gauss-Newton implementation of finite element DIC is proposed as a cost-effective and mathematically sound alternative to this approximation. 相似文献
4.
Because of the introduction of new processing parameters in water-assisted injection molding (WAIM), processes control has become more difficult. First, design of experiment (DOE) was carried out by using optimized Latin hypercubes (Opt LHS). On the basis of this, computational fluid dynamics (CFD) method was used to simulate and calculate hollowed core ratios and wall thickness differences of cooling water pipe at different positions. Then inverse radial basis function (RBF) neural network model reflecting the fitting relationship between processing parameters and molding quality was established, and accuracy of the model was detected by cross validation. Finally, expected molding quality was applied to predict processing parameters, and the obtained molding quality under the predicted processing parameters was verified by computer aided engineering (CAE) simulation and experimental methods. The results showed that mean relative precisions of processing parameters such as melt temperature, delay time, short shot size, water pressure, and mold temperature for inverse RBF model were 98.6%, 93.6%, 98.5%, 93.9%, and 97.9%, respectively, which met the accuracy requirements. Furthermore, compared with expected values of hollowed core ratios and wall thickness differences, the average errors of CAE and experiment were 2.3% and 4.9%, respectively. 相似文献
5.
Thioux Marc; Stark David E.; Klaiman Cheryl; Schultz Robert T. 《Canadian Metallurgical Quarterly》2006,32(5):1155
Some individuals are able to determine the weekday of a given date in a few seconds (finding for instance that June 12, 1900, was a Tuesday). This ability has fascinated scientists for many years because it is predominantly observed in people with limited intelligence and may appear very early in life. Exceptional visual memory, exceptional concentration abilities, or privileged access to lower levels of information not normally available through introspection have been advanced to explain such phenomena. In the present article, the authors show that a simple cognitive model can explain all aspects of the performance of Donny, a young autistic savant who is possibly the fastest and most accurate calendar prodigy ever described. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
介绍了我国流域生态需水研究现状,在对流域生态环境需水计算的前提条件进行阐述的基础上,根据生态需水的水文学原理以及生态系统学原理,从8个方面提出了流域生态环境需水的计算方法,以确定整个流域的生态环境需水量,从而合理量化生态需水总量,达到水资源优化配置的目的. 相似文献
7.
含缺陷压力管道经缺陷评定合乎使用后,其疲劳寿命的估计具有重要的工程意义。将整个含缺陷压力管道作为一个整体,分析了含缺陷压力管道的疲劳裂纹扩展特点,提出了相应的含缺陷压力管道疲劳寿命的计算过程,并在基于可靠性评价的基础上,给出了核压力管道的可接受失效概率,最终得到了含缺陷核压力管道疲劳寿命预测方法。 相似文献
8.
Superconducting qubits are solid state electrical circuits fabricated using techniques borrowed from conventional integrated circuits. They are based on the Josephson tunnel junction, the only non-dissipative, strongly non-linear circuit element available at low temperature. In contrast to microscopic entities such as spins or atoms, they tend to be well coupled to other circuits, which make them appealling from the point of view of readout and gate implementation. Very recently, new designs of superconducting qubits based on multi-junction circuits have solved the problem of isolation from unwanted extrinsic electromagnetic perturbations. We discuss in this review how qubit decoherence is affected by the intrinsic noise of the junction and what can be done to improve it.
PACS: 03.67.-a, 03.65.Yz, 85.25.-j, 85.35.Gv 相似文献
9.
介绍Cable Modem的基本概念、传输方式、标准规范,并对影响Cable Modem工作稳定性的反向噪声问题进行技术分析,并提出预防控制措施。 相似文献
10.
Adriana Brancaccio Giovanni Leone Rocco Pierri 《AEUE-International Journal of Electronics and Communications》2004,58(6):382-390
In this paper, by applying a non linear model for the electromagnetic inverse scattering, a technique for the dielectric profiling of a planarly layered medium is investigated and applied to void localization and diagnostics inside a homogeneous lossless slab (one-dimensional geometry). Data are collected under plane wave multifrequency normal incidence. Suitable finite dimensional representations for the unknown functions are introduced and their influence on the model is discussed. The resulting functional equation is solved by the method of weighted residuals and the solution algorithm amounts to minimizing a non quadratic function, where particular attention is devoted to reduce the occurrence of local minima. Finally, the inversion algorithm is validated by applications to both simulated and experimental data. 相似文献