全文获取类型
收费全文 | 13118篇 |
免费 | 2092篇 |
国内免费 | 642篇 |
专业分类
电工技术 | 1605篇 |
综合类 | 783篇 |
化学工业 | 1203篇 |
金属工艺 | 672篇 |
机械仪表 | 794篇 |
建筑科学 | 1398篇 |
矿业工程 | 117篇 |
能源动力 | 1204篇 |
轻工业 | 83篇 |
水利工程 | 120篇 |
石油天然气 | 71篇 |
武器工业 | 82篇 |
无线电 | 2247篇 |
一般工业技术 | 2046篇 |
冶金工业 | 218篇 |
原子能技术 | 253篇 |
自动化技术 | 2956篇 |
出版年
2025年 | 91篇 |
2024年 | 392篇 |
2023年 | 687篇 |
2022年 | 568篇 |
2021年 | 579篇 |
2020年 | 750篇 |
2019年 | 670篇 |
2018年 | 483篇 |
2017年 | 676篇 |
2016年 | 741篇 |
2015年 | 692篇 |
2014年 | 867篇 |
2013年 | 857篇 |
2012年 | 1090篇 |
2011年 | 992篇 |
2010年 | 724篇 |
2009年 | 899篇 |
2008年 | 538篇 |
2007年 | 898篇 |
2006年 | 746篇 |
2005年 | 348篇 |
2004年 | 190篇 |
2003年 | 136篇 |
2002年 | 152篇 |
2001年 | 151篇 |
2000年 | 112篇 |
1999年 | 92篇 |
1998年 | 46篇 |
1997年 | 39篇 |
1996年 | 43篇 |
1995年 | 24篇 |
1994年 | 26篇 |
1993年 | 24篇 |
1992年 | 31篇 |
1991年 | 15篇 |
1990年 | 19篇 |
1989年 | 18篇 |
1988年 | 42篇 |
1987年 | 101篇 |
1986年 | 102篇 |
1985年 | 13篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1979年 | 13篇 |
1970年 | 9篇 |
1967年 | 12篇 |
1966年 | 16篇 |
1964年 | 9篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Materials Science and Engineering: A》2006,415(1-2):33-39
Firstly, the compress experiment is undertaken to investigate the efficiency of repaired panels in this paper, and then modeling of the mechanical behavior of the repaired composite panel under compressive static load is conducted by using of the finite element method. The effect of geometric non-linearity on the stress–strain response is considered in the numeric analysis. Fatherly, the user material subroutine (UMAT) is integrated with the ABAQUS package with the geometric non-linearity effect for studying the damage initiation and its progression in the composite structure, and quadrilateral, linear, thick shell elements (S8R) are adopted. Finally, the predicted strain distribution, damage evolution and strength of the laminate are compared with the test results. 相似文献
2.
《International Journal of Heat and Mass Transfer》2007,50(23-24):4581-4599
An infrared imaging system is used to measure detailed distributions of local heat transfer coefficient from rectangular channels with two opposite wide walls roughened by 45° staggered ribs of twenty test cases. Nusselt number (Nu) contours over the ribbed surfaces are presented for five sets of channels with an identical rib-floor configuration, but different channel-heights where the complex Nu distributions without bleed and then with bleeds from the scanned rib-floor or from the ribbed wall opposite to the scanned rib-floor or from the smooth sidewall are analyzed to examine the synergetic effects of variable channel-heights and different bleed conditions on heat transfer. Spatially averaged heat transfer results for the entire set of test channels are generated with the thermal performance factors compared to establish the heat transfer correlations with applications to the design of coolant channels in a gas turbine blade. 相似文献
3.
Chang Yang Chengyin Liu Ning Wu Xiang Wu Yidong Li Zhiying Wang 《Neural computing & applications》2014,25(7-8):1741-1754
Collaboration representation-based classification (CRC) was proposed as an alternative approach to the sparse representation method with similar efficiency. The CRC is essentially a competition scheme for the training samples to compete with each other in representing the test sample, and the training class with the minimum representation residual from the test sample wins the competition in the classification. However, the representation error is usually calculated based on the Euclidean distance between a test sample and the weighted sum of all the same-class samples. This paper exploits alternative methods of calculating the representation error in the CRC methods to reduce the representation residual in a more optimal way, so that the sample classes compete with each other in a closer range to represent the test sample. A large number of face recognition experiments on three face image databases show that the CRC methods with optimized presentation residual achieve better performance than the original CRC, and the maximum improvement in classification accuracy is up to 12 %. 相似文献
4.
Wei Shikui Jiang Su Jin Wenxian Zhao Yao Ni Rongrong Zhu Zhenfeng 《Multimedia Systems》2015,21(2):207-216
Multimedia Systems - Recently, the frame fusion based video copy detection scheme provides a possibility to detect copies in a continuous query video stream. However, its computational complexity... 相似文献
5.
6.
In this paper, we propose a general optimization-based model for classification. Then we show that some well-known optimization-based methods for classification, which were developed by Shi et al. [Data mining in credit card portfolio management: a multiple criteria decision making approac. In: Koksalan M, Zionts S, editors. Multiple criteria decision making in the new millennium. Berlin: Springer; 2001. p. 427–36] and Freed and Glover [A linear programming approach to the discriminant problem. Decision Sciences 1981; 12: 68–79; Simple but powerful goal programming models for discriminant problems. European Journal of Operational Research 1981; 7: 44–60], are special cases of our model. Moreover, three new models, MCQP (multi-criteria indefinite quadratic programming), MCCQP (multi-criteria concave quadratic programming) and MCVQP (multi-criteria convex programming), are developed based on the general model. We also propose algorithms for MCQP and MCCQP, respectively. Then we apply these models to three real-life problems: credit card accounts, VIP mail-box and social endowment insurance classification. Extensive experiments are done to compare the efficiency of these methods. 相似文献
7.
In this paper, the air film formation behavior of air cushion belt conveyor with stable load is studied. The air cushion field is analyzed by means of theoretical derivation, numerical simulation and experimental research. An intelligent experiment platform is developed. Three dimensional pressure distribution of air film and the air film thickness distribution along the conveyor belt in the width direction are obtained. The experimental result is analyzed by comparing with theoretical calculation and numerical simulation. The numerical and theoretical results are in good agreement with those obtained from experiments. The air film formation behavior pattern of air cushion belt conveyor with stable load is presented. The optimized film thickness and pore distribution are obtained based on the comprehensive energy consumption. This study provides a basis for the optimization design of air cushion belt conveyor. 相似文献
8.
9.
《Materials Research Bulletin》2006,41(7):1403-1406
Change in the low-voltage luminescence properties of ZnGa2O4:Mn green phosphors before and after In2O3-coating was examined by cathodoluminescence. The coating state and distribution of In2O3 nano-particles on phosphors were investigated by field emission scanning electron microscopy (FE-SEM). Especially, based on FE-SEM analysis, the formation of In2O3 nano-particles on ZnGa2O4:Mn phosphor was confirmed. The improvement of the cathodoluminescence efficiency and lifetime in the In2O3-coated phosphors was associated with the coating of In2O3 nano-particles. 相似文献
10.
Lingwen ZHANG Zhenhui TAN 《Frontiers of Electrical and Electronic Engineering in China》2008,3(1):40-43
Time difference of arrival (TDOA) is the positioning technique with the most potential in cellular mobile telecommunication
systems. The Taylor series expansion method has been widely used in solving nonlinear equations for its high accuracy and
good robustness. However, the performance of the Taylor’s method depends highly on the initial estimation. Therefore, one
new algorithm, hybrid optimizing algorithm (HOA) was proposed, which combines the Taylor series expansion method with the
steepest decent method. The steepest decent method features fast convergence at the initial iteration and small computation
complexity. HOA takes great advantage of both methods. Simulation results show that HOA achieves better performance on positioning
accuracy and efficiency.
__________
Translated from Journal on Communications, 2007, 28(6): 7–11 [译自: 通信学报] 相似文献