全文获取类型
收费全文 | 34948篇 |
免费 | 2466篇 |
国内免费 | 992篇 |
专业分类
电工技术 | 1481篇 |
技术理论 | 4篇 |
综合类 | 1554篇 |
化学工业 | 6075篇 |
金属工艺 | 1535篇 |
机械仪表 | 1671篇 |
建筑科学 | 1689篇 |
矿业工程 | 759篇 |
能源动力 | 1194篇 |
轻工业 | 2230篇 |
水利工程 | 448篇 |
石油天然气 | 1010篇 |
武器工业 | 146篇 |
无线电 | 5408篇 |
一般工业技术 | 5077篇 |
冶金工业 | 2737篇 |
原子能技术 | 388篇 |
自动化技术 | 5000篇 |
出版年
2024年 | 104篇 |
2023年 | 451篇 |
2022年 | 863篇 |
2021年 | 1193篇 |
2020年 | 928篇 |
2019年 | 801篇 |
2018年 | 898篇 |
2017年 | 945篇 |
2016年 | 862篇 |
2015年 | 1071篇 |
2014年 | 1415篇 |
2013年 | 2118篇 |
2012年 | 1986篇 |
2011年 | 2311篇 |
2010年 | 1834篇 |
2009年 | 1881篇 |
2008年 | 1929篇 |
2007年 | 1740篇 |
2006年 | 1566篇 |
2005年 | 1254篇 |
2004年 | 1107篇 |
2003年 | 1191篇 |
2002年 | 1397篇 |
2001年 | 1177篇 |
2000年 | 816篇 |
1999年 | 709篇 |
1998年 | 977篇 |
1997年 | 690篇 |
1996年 | 577篇 |
1995年 | 474篇 |
1994年 | 388篇 |
1993年 | 332篇 |
1992年 | 247篇 |
1991年 | 222篇 |
1990年 | 225篇 |
1989年 | 201篇 |
1988年 | 170篇 |
1987年 | 153篇 |
1986年 | 130篇 |
1985年 | 127篇 |
1984年 | 110篇 |
1983年 | 75篇 |
1982年 | 70篇 |
1981年 | 59篇 |
1980年 | 81篇 |
1979年 | 49篇 |
1978年 | 60篇 |
1977年 | 58篇 |
1976年 | 76篇 |
1975年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
941.
Matthew Chang Author Vitae Author Vitae 《Journal of Systems and Software》2009,82(6):1036-1045
In this paper, we report our experience on the use of phrases as basic features in the email classification problem. We performed extensive empirical evaluation using our large email collections and tested with three text classification algorithms, namely, a naive Bayes classifier and two k-NN classifiers using TF-IDF weighting and resemblance respectively. The investigation includes studies on the effect of phrase size, the size of local and global sampling, the neighbourhood size, and various methods to improve the classification accuracy. We determined suitable settings for various parameters of the classifiers and performed a comparison among the classifiers with their best settings. Our result shows that no classifier dominates the others in terms of classification accuracy. Also, we made a number of observations on the special characteristics of emails. In particular, we observed that public emails are easier to classify than private ones. 相似文献
942.
Myung Geol Choi Eunjung Ju Jung‐Woo Chang Jehee Lee Young J. Kim 《Computer Graphics Forum》2009,28(7):1773-1780
The standard C/C++ implementation of a spatial partitioning data structure, such as octree and quadtree, is often inefficient in terms of storage requirements particularly when the memory overhead for maintaining parent‐to‐child pointers is significant with respect to the amount of actual data in each tree node. In this work, we present a novel data structure that implements uniform spatial partitioning without storing explicit parent‐to‐child pointer links. Our linkless tree encodes the storage locations of subdivided nodes using perfect hashing while retaining important properties of uniform spatial partitioning trees, such as coarse‐to‐fine hierarchical representation, efficient storage usage, and efficient random accessibility. We demonstrate the performance of our linkless trees using image compression and path planning examples. 相似文献
943.
944.
Wireless local area networks provide high speed data transferring rate to a mobile device. And it is crucial to integrate together two critical issues, the authentication and roaming in heterogeneous networks. For this, Tsai and Chang proposed a SIM-based authentication mechanism for wireless local area networks in 2006. Tsai and Chang's scheme provides an integration method of mobile cellular networks and wireless local area networks. Unfortunately, we found that there are some weaknesses existing in their scheme. In this paper, we propose an improved version for a user roaming in heterogeneous networks. Besides, we also proposed a mobile IP model to provide a better efficiency for a mobile user in WLAN environment. 相似文献
945.
Yih-Kuen Tsay Yu-Fang Chen Ming-Hsien Tsai Kang-Nien Wu Wen-Chin Chan Chi-Jian Luo Jinn-Shu Chang 《Formal Aspects of Computing》2009,21(3):259-275
We introduce a graphical interactive tool, named GOAL, that can assist the user in understanding Büchi automata, linear temporal
logic, and their relation. Büchi automata and linear temporal logic are closely related and have long served as fundamental
building blocks of linear-time model checking. Understanding their relation is instrumental in discovering algorithmic solutions
to model checking problems or simply in using those solutions, e.g., specifying a temporal property directly by an automaton
rather than a temporal formula so that the property can be verified by an algorithm that operates on automata. One main function
of the GOAL tool is translation of a temporal formula into an equivalent Büchi automaton that can be further manipulated visually.
The user may edit the resulting automaton, attempting to optimize it, or simply run the automaton on some inputs to get a
basic understanding of how it operates. GOAL includes a large number of translation algorithms, most of which support past
temporal operators. With the option of viewing the intermediate steps of a translation, the user can quickly grasp how a translation
algorithm works. The tool also provides various standard operations and tests on Büchi automata, in particular the equivalence
test which is essential for checking if a hand-drawn automaton is correct in the sense that it is equivalent to some intended
temporal formula or reference automaton. Several use cases are elaborated to show how these GOAL functions may be combined
to facilitate the learning and teaching of Büchi automata and linear temporal logic.
This work was partially supported by the National Science Council, Taiwan (R.O.C.) under grants NSC94-2213-E-002-089, NSC95-2221-E-002-127,
NSC95-3114-P-001-001-Y02 (iCAST 2006), NSC96-3114-P-001-002-Y (iCAST 2007), and NSC97-2221-E-002-074-MY3. 相似文献
946.
Chia-Yen Lee Zgen-Hui Chen Hsien-Tseng Chang Chih-Yung Wen Chiang-Ho Cheng 《Microsystem Technologies》2009,15(8):1171-1177
This study designs, fabricates, and characterizes a novel micro electromagnetic actuator comprising a PDMS diaphragm, a polyimide-coated
copper micro coil, and a permanent magnet. When an electrical current is passed through the micro coil, a magnetic force is
induced between the coil and the magnet which causes the diaphragm to deflect, thereby creating an actuation effect. The experimental
results demonstrate that the diaphragm deflection can be accurately controlled by regulating the current passed through the
micro coil. It is shown that the maximum diaphragm deflection within elastic limits is 150 μm; obtained by passing a current
of 0.6 A through a micro coil with a line width of 100 μm. The micro actuator proposed in this study is easily fabricated
and is readily integrated with existing bio-medical chips due to its planar structure. 相似文献
947.
A macroscopic mechanism is developed to verify a repulsive-force electrostatic actuator, which consists of an array of fixed
finger electrodes and an array of moving finger electrodes. The actuator is able to generate an asymmetric electric field
surrounding the top and bottom surfaces of each moving finger electrode to push the moving finger up and away from the fixed
fingers. The macroscopic mechanism consists of a macro repulsive force actuator, a high voltage power supply, a z-stage, a
high precision balance and a LCR meter. The force and capacitance characteristic curves of the actuator are obtained using
the macro mechanism. The 3-stage force (repulsive, zero and attractive forces) of the actuator is verified, as well as the
effects of the moving finger width on the actuator’s performance. Experimental tests show that the macro repulsive-force actuator
can generate a repulsive force of 3,000 μN with a maximum gap of 9.5 mm for generating a repulsive force. 相似文献
948.
As mobile technology has developed, mobile banking has become accepted as part of daily life. Although many studies have been conducted to assess users’ satisfaction with mobile applications, none has focused on the ways in which the three quality factors associated with mobile banking – system quality, information quality and interface design quality – affect consumers’ trust and satisfaction. Our proposed research model, based on DeLone and McLean’s model, assesses how these three external quality factors can impact satisfaction and trust. We collected 276 valid questionnaires from mobile banking customers, then analyzed them using structural equation modeling. Our results show that system quality and information quality significantly influence customers’ trust and satisfaction, and that interface design quality does not. We present herein implications and suggestions for further research. 相似文献
949.
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
950.
This work studies a nonlinear optimization problem subject to fuzzy relational equations with max-t-norm composition. Since the feasible domain of fuzzy relational equations with more than one minimal solution is non-convex, traditional nonlinear programming methods usually cannot solve them efficiently. This work proposes a genetic algorithm to solve this problem. This algorithm first locates the feasible domain through the maximum solution and the minimal solutions of the fuzzy relational equations, to significantly reduce the search space. The algorithm then executes all genetic operations inside this feasible domain, and thus avoids the need to check the feasibility of each solution generated. Moreover, it uses a local search operation to fine-tune each mutated solution. Experimental results indicate that the proposed algorithm can accelerate the searching speed and find the optimal solution. 相似文献