全文获取类型
收费全文 | 60136篇 |
免费 | 5588篇 |
国内免费 | 3149篇 |
专业分类
电工技术 | 3971篇 |
技术理论 | 4篇 |
综合类 | 4344篇 |
化学工业 | 9883篇 |
金属工艺 | 3434篇 |
机械仪表 | 3945篇 |
建筑科学 | 4565篇 |
矿业工程 | 1335篇 |
能源动力 | 1710篇 |
轻工业 | 4418篇 |
水利工程 | 1200篇 |
石油天然气 | 2692篇 |
武器工业 | 487篇 |
无线电 | 7681篇 |
一般工业技术 | 7836篇 |
冶金工业 | 2435篇 |
原子能技术 | 769篇 |
自动化技术 | 8164篇 |
出版年
2024年 | 245篇 |
2023年 | 887篇 |
2022年 | 1707篇 |
2021年 | 2389篇 |
2020年 | 1719篇 |
2019年 | 1546篇 |
2018年 | 1631篇 |
2017年 | 1842篇 |
2016年 | 1855篇 |
2015年 | 2501篇 |
2014年 | 3002篇 |
2013年 | 3662篇 |
2012年 | 3929篇 |
2011年 | 4332篇 |
2010年 | 3913篇 |
2009年 | 3560篇 |
2008年 | 3594篇 |
2007年 | 3314篇 |
2006年 | 3298篇 |
2005年 | 2848篇 |
2004年 | 2102篇 |
2003年 | 2002篇 |
2002年 | 2281篇 |
2001年 | 1907篇 |
2000年 | 1528篇 |
1999年 | 1334篇 |
1998年 | 1074篇 |
1997年 | 890篇 |
1996年 | 806篇 |
1995年 | 714篇 |
1994年 | 602篇 |
1993年 | 452篇 |
1992年 | 334篇 |
1991年 | 264篇 |
1990年 | 198篇 |
1989年 | 162篇 |
1988年 | 130篇 |
1987年 | 75篇 |
1986年 | 61篇 |
1985年 | 42篇 |
1984年 | 33篇 |
1983年 | 16篇 |
1982年 | 22篇 |
1981年 | 21篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1959年 | 4篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Block preconditioner with circulant blocks (BPCB) has been used for solving linear systems with block Toeplitz structure since 1992 [R. Chan, X. Jin, A family of block preconditioners for block systems, SIAM J. Sci. Statist. Comput. (13) (1992) 1218–1235]. In this new paper, we use BPCBs to general linear systems (with no block structure usually). The BPCBs are constructed by partitioning a general matrix into a block matrix with blocks of the same size and then applying T. Chan’s optimal circulant preconditioner [T. Chan, An optimal circulant preconditioner for Toeplitz systems, SIAM J. Sci. Statist. Comput. (9) (1988) 766–771] to each block. These BPCBs can be viewed as a generalization of T. Chan’s preconditioner. It is well-known that the optimal circulant preconditioner works well for solving some structured systems such as Toeplitz systems by using the preconditioned conjugate gradient (PCG) method, but it is usually not efficient for solving general linear systems. Unlike T. Chan’s preconditioner, BPCBs used here are efficient for solving some general linear systems by the PCG method. Several basic properties of BPCBs are studied. The relations of the block partition with the cost per iteration and the convergence rate of the PCG method are discussed. Numerical tests are given to compare the cost of the PCG method with different BPCBs. 相似文献
992.
Adaptive binary tree for fast SVM multiclass classification 总被引:1,自引:0,他引:1
This paper presents an adaptive binary tree (ABT) to reduce the test computational complexity of multiclass support vector machine (SVM). It achieves a fast classification by: (1) reducing the number of binary SVMs for one classification by using separating planes of some binary SVMs to discriminate other binary problems; (2) selecting the binary SVMs with the fewest average number of support vectors (SVs). The average number of SVs is proposed to denote the computational complexity to exclude one class. Compared with five well-known methods, experiments on many benchmark data sets demonstrate our method can speed up the test phase while remain the high accuracy of SVMs. 相似文献
993.
Hyun Uk Yun Chul Jin Kim Sung Joo Kim No Cheol Park Hyunseok Yang Young-Pil Park 《Microsystem Technologies》2009,15(10-11):1531-1538
Microactuators for micromirror system have found many applications in various areas including projection displays, optical switches, RF switches and so on. In this paper we demonstrated micromirror actuator using ionic polymer metal composites (IPMC) that is a suitable candidate, since it has many attractive qualities such as durability, aquatic, miniature and light-weighted. Specially, IPMC has extraordinary advantages which are simple bending motion for low driving voltage (1–2 V), low power consumption, and simple structure. The IPMC actuator is made of Nafion NE-1110 (Dupont Co, Ltd., 260 µm thick) layer and electrode (platinum) layers and driven by 1–4 V. The displacement measured vertically is 0.25 mm and tilting angle is 11.3°. The angular motion, which is more than 10°, is a good advantage in the field of display module. This paper shows that the IPMC actuator has enough possibility for other applications. 相似文献
994.
In this article, based on the standard linear solid model, the Euler-Bernoulli hypothesis and the Galerkin method, an analysis
of the nonlinear dynamic stability for a clamped-guided viscoelastic microbeam under both a periodic axial force and a symmetric
electrostatic load is presented. By using the incremental harmonic balanced method, the boundary of the principal region of
instability is got. In the numerical calculation, the effect of the environmental and inner damping, geometric nonlinear,
creep quantity and the symmetric electrostatic load on the principal region of instability is discussed. 相似文献
995.
Structure identification of Bayesian classifiers based on GMDH 总被引:1,自引:0,他引:1
This paper introduces group method of data handing (GMDH) theory to Bayesian classification, and proposes GMBC algorithm for structure identification of Bayesian classifiers. The algorithm combines two structure identification ideas of search & scoring and dependence analysis, and is able to accomplish the process of adaptive structure identification. We experimentally test two versions of Bayesian classifiers (GMBC-BDe and GMBC-BIC) over 25 data sets. The results show that, the structure identification of the two Bayesian classifiers especially GMBC-BDe is very effective. And when the data sets contain lots of noise, the superiority of Bayesian classifiers learned by GMBC is more obvious. Finally, giving a classification domain without any prior information about the noise, we recommend adopting GMBC-BDe rather than GMBC-BIC. 相似文献
996.
Choonjong Kwak Jin Sung Choi Chang Ouk Kim Ick-Hyun Kwon 《Expert systems with applications》2009,36(5):9039-9045
In this research, we deal with VMI (Vendor Managed Inventory) problem where one supplier is responsible for managing a retailer’s inventory under unstable customer demand situation. To cope with the nonstationary demand situation, we develop a retrospective action-reward learning model, a kind of reinforcement learning techniques, which is faster in learning than conventional action-reward learning and more suitable to apply to the control domain where rewards for actions vary over time. The learning model enables the inventory control to become situation reactive in the sense that replenishment quantity for the retailer is automatically adjusted at each period by adapting to the change in customer demand. The replenishment quantity is a function of compensation factor that has an effect of increasing or decreasing the replenishment amount. At each replenishment period, a cost-minimizing compensation factor value is chosen in the candidate set. A simulation based experiment gave us encouraging results for the new approach. 相似文献
997.
The traditional way of state estimation in semiconductor manufacturing, known as “threaded” state estimation, segregates the process data into different bins and uses the ones that match the current event of the specific context information (such as tools, layers, products) to update the process state. The limitation of threaded state estimation is that a narrowly defined process stream can result in too many different threads and insufficient data for each thread. This limitation becomes more severe in high-mix manufacturing, where there can be many products and many tools. Hence there is great interest in estimation methods that utilize all available data in the analysis. In this work, the characteristics inherent in state estimation of high-mix semiconductor manufacturing processes are analyzed, and a general framework is introduced for the non-threaded state estimation methods, i.e., state estimation without segregating the process data into different bins. The framework is based on the best linear unbiased estimate (BLUE) of a simplified stationary singular Gauss–Markov process, and non-threaded state estimation methods based on the Kalman filter, least squares and recursive least squares (RLS) are analyzed using the general framework. Simulation examples are presented to illustrate the equivalence between different algorithms. As real processes are rarely stationary, modifications to the Kalman filter and RLS are discussed. We show that in non-threaded state estimation, how to regulate the estimate covariance plays a significant role in estimation performance. To handle nonstationary disturbances that often occur in semiconductor processes, Bayesian-enhanced adaptive versions of the Kalman filter and RLS are proposed. Both simulated and industrial nonstationary processes are used to demonstrate the effectiveness of the proposed adaptive methods. 相似文献
998.
999.
1000.