全文获取类型
收费全文 | 4076篇 |
免费 | 133篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 80篇 |
综合类 | 7篇 |
化学工业 | 1014篇 |
金属工艺 | 64篇 |
机械仪表 | 63篇 |
建筑科学 | 312篇 |
矿业工程 | 17篇 |
能源动力 | 81篇 |
轻工业 | 670篇 |
水利工程 | 24篇 |
石油天然气 | 11篇 |
无线电 | 259篇 |
一般工业技术 | 550篇 |
冶金工业 | 488篇 |
原子能技术 | 27篇 |
自动化技术 | 546篇 |
出版年
2022年 | 41篇 |
2021年 | 49篇 |
2020年 | 40篇 |
2019年 | 54篇 |
2018年 | 53篇 |
2017年 | 43篇 |
2016年 | 89篇 |
2015年 | 76篇 |
2014年 | 138篇 |
2013年 | 192篇 |
2012年 | 175篇 |
2011年 | 158篇 |
2010年 | 147篇 |
2009年 | 167篇 |
2008年 | 169篇 |
2007年 | 159篇 |
2006年 | 173篇 |
2005年 | 137篇 |
2004年 | 120篇 |
2003年 | 108篇 |
2002年 | 63篇 |
2001年 | 52篇 |
2000年 | 65篇 |
1999年 | 49篇 |
1998年 | 67篇 |
1997年 | 53篇 |
1996年 | 43篇 |
1995年 | 35篇 |
1994年 | 51篇 |
1993年 | 44篇 |
1992年 | 38篇 |
1991年 | 40篇 |
1990年 | 43篇 |
1989年 | 48篇 |
1988年 | 39篇 |
1987年 | 52篇 |
1986年 | 34篇 |
1985年 | 55篇 |
1984年 | 58篇 |
1983年 | 43篇 |
1982年 | 38篇 |
1981年 | 47篇 |
1980年 | 52篇 |
1979年 | 45篇 |
1978年 | 42篇 |
1977年 | 51篇 |
1976年 | 53篇 |
1975年 | 35篇 |
1974年 | 41篇 |
1973年 | 35篇 |
排序方式: 共有4213条查询结果,搜索用时 9 毫秒
31.
32.
Web‐Like Interconnected Carbon Networks from NaCl‐Assisted Pyrolysis of ZIF‐8 for Highly Efficient Oxygen Reduction Catalysis 下载免费PDF全文
Yuhong Qian Tao An Karl Erik Birgersson Zhaolin Liu Dan Zhao 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(16)
The oxygen reduction reaction (ORR) is under intense research due to its significance in energy storage and conversion processes. Recent studies show that interconnected and hierarchically porous structures can further enhance ORR kinetics as well as catalyst durability, but their preparation can be quite time and/or chemical consuming. Here, a simple approach is reported to prepare such complex structures by pyrolyzing composites containing NaCl and ZIF‐8. The templating effect of molten NaCl connects ZIF‐8 particles into web‐like carbon networks. During ORR activity measurements, it achieves a 0.964 V onset potential and a 38 mV dec?1 Tafel slope, which are comparable to those of the benchmark Pt/C (0.979 V and 40 mV dec?1). Due to the metal‐free feature, this catalyst exhibits a 16 mV shift in half‐wave potential after a 10 000‐cycle durability test, which is only 60% of that of Pt/C. The catalyst is also tested in Zn–air batteries and the assemblies are able to work at above 1.2 V for 140 h, which triples the life held by those with Pt/C. This study demonstrates a facile strategy to prepare metal‐free ORR catalysts with interconnectivity and hierarchical porosity, and proves their great potentials in ORR catalysis and Zn–air batteries. 相似文献
33.
Integrating intelligent job-scheduling into a real-world production-scheduling system 总被引:1,自引:0,他引:1
The paper addresses the problem of scheduling production orders (jobs). First, an approach based on simulated annealing and Hopfield nets is described. Since performance was unsatisfactory for real-world applications, we changed the problem representation and tuned the scheduling method, dropping features of the Hopfield net and retaining simulated annealing. Both computing time and solution quality were significantly improved. The scheduling method was then integrated into a software system for short-term production planning and control (electronic leitstand). The paper describes how real-world requirements are met, and how the scheduling method interacts with the leitstand's database and graphical representation of schedules. 相似文献
34.
Mimicking human motion with a humanoid robot is essential for allowing humanoid robots to be used in service applications.
Simply creating motions without considerations for balance and stability or directly copying motion from a human using motion
capture and implementing it on a humanoid robot may not be successful because of the difference in physical properties between
the human and the humanoid robot, which may cause instability and make it fall. Using the Zero Moment Point as the stability
criteria, this work proposes a Constrained Analytical Trajectory Filter as part of an Analytical Motion Filter, which stabilizes
a reference motion that can come from human motion capture data, kinematic synthesis, or animation software. The resulting
solutions used in the Constrained Analytical Trajectory Filter provide insight into the complex interactions of motion and
stability. The solutions were verified in simulation and with hardware, showing that the analytical filter can be successfully
applied for stabilizing reference motions for humanoid robots which may be unstable otherwise. 相似文献
35.
The spectral properties of the incidence matrix of the communication graph are exploited to provide solutions to two multi-agent control problems. In particular, we consider the problem of state agreement with quantized communication and the problem of distance-based formation control. In both cases, stabilizing control laws are provided when the communication graph is a tree. It is shown how the relation between tree graphs and the null space of the corresponding incidence matrix encode fundamental properties for these two multi-agent control problems. 相似文献
36.
Fabien Tricoire Martin Romauch Karl F. Doerner Richard F. Hartl 《Computers & Operations Research》2010,37(2):351-367
We present the multi-period orienteering problem with multiple time windows (MuPOPTW), a new routing problem combining objective and constraints of the orienteering problem (OP) and team orienteering problem (TOP), constraints from standard vehicle routing problems, and original constraints from a real-world application. The problem itself comes from a real industrial case. Specific route duration constraints result in a route feasibility subproblem. We propose an exact algorithm for this subproblem, and we embed it in a variable neighborhood search method to solve the whole routing problem. We then provide experimental results for this method. We compare them to a commercial solver. We also adapt our method to standard benchmark OP and TOP instances, and provide comparative tables with state-of-the-art algorithms. 相似文献
37.
Sophie N. Parragh Karl F. Doerner Richard F. Hartl 《Computers & Operations Research》2010,37(6):1129-1138
In dial-a-ride problems passengers have to be transported between pre-specified pickup and delivery locations under user inconvenience considerations. The problem variant considered in this paper aims at minimizing total routing costs while respecting maximum route duration limits, time windows, and maximum user ride time limits. We propose a competitive variable neighborhood search-based heuristic, using three classes of neighborhoods. The first neighborhood class uses simple swap operations tailored to the dial-a-ride problem; the second neighborhood class is based on the ejection chain idea; and the third neighborhood class exploits the existence of arcs where the vehicle load is zero, giving rise to natural sequences of requests. We report new best results for 16 out of 20 benchmark instances. 相似文献
38.
In recent work, Kalai, Klivans, Mansour, and Servedio (2005) studied a variant of the “Low-Degree (Fourier) Algorithm” for learning under the uniform probability distribution on {0,1} n . They showed that the L 1 polynomial regression algorithm yields agnostic (tolerant to arbitrary noise) learning algorithms with respect to the class of threshold functions—under certain restricted instance distributions, including uniform on {0,1} n and Gaussian on ? n . In this work we show how all learning results based on the Low-Degree Algorithm can be generalized to give almost identical agnostic guarantees under arbitrary product distributions on instance spaces X 1×???×X n . We also extend these results to learning under mixtures of product distributions. The main technical innovation is the use of (Hoeffding) orthogonal decomposition and the extension of the “noise sensitivity method” to arbitrary product spaces. In particular, we give a very simple proof that threshold functions over arbitrary product spaces have δ-noise sensitivity $O(\sqrt{\delta})$ , resolving an open problem suggested by Peres (2004). 相似文献
39.
A turbulent environment characterized by unsteady economic cycles, customized products, a growing bandwidth of products, an exploding number of variants and shorter product life cycles force manufacturers to permanent adaptation of their factories. Flexible and changeable structures will be required to enable factories dealing with the technological challenges and economic pressure of the future competitively. In order to achieve changeability objectives in manufacturing, a detailed analysis of existing structures and its representative attributes is essential. It is the basis for systematic structure planning of factories. In this paper a method for analyzing the capacitive and technological structure of a factory embedded in a network of manufacturing and its network of suppliers is presented. The synchronization of product and production development under the influence of change is intended. Therefore, the structural views of product and production are specifically in focus of the method. Based on the results of the analysis models an approach of a tool for giving product and production structure dynamism is suggested to investigate the effects and dependencies of change drivers in manufacturing. 相似文献
40.