全文获取类型
收费全文 | 15473篇 |
免费 | 592篇 |
国内免费 | 578篇 |
专业分类
电工技术 | 594篇 |
综合类 | 614篇 |
化学工业 | 1251篇 |
金属工艺 | 991篇 |
机械仪表 | 2089篇 |
建筑科学 | 822篇 |
矿业工程 | 317篇 |
能源动力 | 671篇 |
轻工业 | 260篇 |
水利工程 | 69篇 |
石油天然气 | 202篇 |
武器工业 | 148篇 |
无线电 | 986篇 |
一般工业技术 | 1541篇 |
冶金工业 | 418篇 |
原子能技术 | 129篇 |
自动化技术 | 5541篇 |
出版年
2024年 | 16篇 |
2023年 | 162篇 |
2022年 | 243篇 |
2021年 | 303篇 |
2020年 | 296篇 |
2019年 | 286篇 |
2018年 | 285篇 |
2017年 | 369篇 |
2016年 | 391篇 |
2015年 | 544篇 |
2014年 | 761篇 |
2013年 | 848篇 |
2012年 | 795篇 |
2011年 | 1147篇 |
2010年 | 759篇 |
2009年 | 935篇 |
2008年 | 963篇 |
2007年 | 1015篇 |
2006年 | 918篇 |
2005年 | 924篇 |
2004年 | 742篇 |
2003年 | 673篇 |
2002年 | 538篇 |
2001年 | 379篇 |
2000年 | 371篇 |
1999年 | 325篇 |
1998年 | 311篇 |
1997年 | 246篇 |
1996年 | 203篇 |
1995年 | 151篇 |
1994年 | 145篇 |
1993年 | 146篇 |
1992年 | 91篇 |
1991年 | 65篇 |
1990年 | 53篇 |
1989年 | 49篇 |
1988年 | 49篇 |
1987年 | 23篇 |
1986年 | 21篇 |
1985年 | 12篇 |
1984年 | 20篇 |
1983年 | 17篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
101.
The molten iron allocation problem (MIAP) is to allocate molten iron from blast furnaces to steel-making furnaces. The allocation needs to observe the release times of the molten iron defined by the draining plan of the blast furnaces and the transport time between the iron-making and steel-making stages. Time window constraints for processing the molten iron must be satisfied to avoid freezing. The objective is to find a schedule with minimum total weighted completion time. This objective reflects the practical consideration of improving steel-making efficiency and reducing operation cost caused by the need for reheating. Such a problem can be viewed as a parallel machine scheduling problem with time windows which is known to be NP-hard. In this paper, we first formulate the molten iron allocation problem as an integer programming model and then reformulate it as a set partitioning model by applying the Dantzig–Wolfe decomposition. We solve the problem using a column generation-based branch-and-price algorithm. Since the subproblem of column generation is still NP-hard, we propose a state-space relaxation-based dynamic programming algorithm for the subproblem. Computational experiments demonstrate that the proposed algorithm is capable of solving problems with up to 100 jobs to optimality within a reasonable computation time. 相似文献
102.
The paper presents a derivation of the dynamic impedance of a PV module. At each bias voltage, the general form of the impedance describes a semicircular locus in the complex impedance plane. Intercepts of each impedance locus yield series, shunt and dynamic resistance of a module. Determinations of the dynamic impedance of a x-Si PV module in the dark with five reverse bias voltages and over a frequency range of 1 Hz to 60 kHz are made. The experimental results validate the derived general form of dynamic impedance. 相似文献
103.
Modeling the effect of pigment morphology on the dynamic compression of coating layers using DEM 总被引:2,自引:1,他引:1
In the present paper, discrete element method (DEM) was employed to investigate the effect of pigment morphology on packing dynamics and compressive behavior of paper coating layers in calendering process. Spherical, platy, and needle-like particles, representing GCC, delaminated clay, and aragonite PCC pigments, were considered in this study. For each particle shape, the compression of coating structures formed by mono-sized and poly-dispersed pigments were modeled. Stress–strain behavior of the coating layers and in-plane and out-of-plane movements of the pigment particles during the compression were computed under the same maximum compressive stress. Simulation results revealed that the in-plane movements of the pigment particles during compression in the calender nip were small in magnitude (<0.35 μm). These findings help to better understand the smoothening phenomena of coating structures during the calendering process. 相似文献
104.
Sun-Yuan Hsieh 《The Journal of supercomputing》2007,39(1):39-57
A graph is distance-hereditary if the distance stays the same between any of two vertices in every connected induced subgraph containing both. Two well-known
classes of graphs, trees and cographs, both belong to distance-hereditary graphs. In this paper, we first show that the perfect
domination problem can be solved in sequential linear-time on distance-hereditary graphs. By sketching some regular property
of the problem, we also show that it can be easily parallelized on distance-hereditary graphs. 相似文献
105.
Xiangqing Tian Xiaoqiong Qi Qiongfang Ma Xiaoping Zhang 《Photonic Network Communications》2006,11(3):271-276
A new design scheme for a distributed algorithm for routing and wavelength assignment (RWA) is developed in this paper, and
the communication rules between the nodes to exchange signaling packets are discussed. The Adaptive-Alternate-Routing-Least-Load
(AARLL) algorithm is implemented in the distributed scheme for the first time. Under dynamic traffic circumstances, the influence
of the race condition, which does not exist in centralized scheme, on the network performance is analyzed and the analyzed
results show that the race condition has a major impact on network performance only under light traffic load, while under
medium and heavy traffic load the impact is very small. To analyze the performance loss caused by adopting the distributed
algorithm for RWA, the capacity loss factor (CLF) is introduced and the calculated results show that CLF does not exceed 6%
under medium traffic load. 相似文献
106.
Java语言及其虚拟机技术探讨 总被引:1,自引:0,他引:1
随着Internet的迅猛发展,Internet编程语言Java愈来愈成为计算机行业的焦点。本文在简述了Java的主要特点后,重点对Java最关键的技术──虚拟机进行了深入的探讨。 相似文献
107.
漳泽水库最优兴利调度研究 总被引:2,自引:0,他引:2
漳泽水库供水能力下降。优化调度方式是提高水库效益的最有效途径。通过采用随机动态规划方法与模拟模型交互运算得到现行控制水位的水库优化调度图。采用同样方法对不同控制水位的水库运行方式进行优化调度,选出的规划水库最优控制水位为汛限水位904 .5 m ,正常高水位905 .5 m 。优化的控制水位方案在保障水库防洪安全的前提下可供给城市生活和工业用水6 300 万m3 ,较现行控制水位下的供水量提高1 255 万m3 。但农业用水仍然不足,应采取一定措施给予解决,如对灌区工程进行改造,因地制宜采取不同节水措施和污水回用等。 相似文献
108.
传统的干燥控制系统思维方式是把干燥流程看成是一个大的惯性场,以惯性的形态看待与过程相关的数据,对输入参数的过程实时性很少研究,这样的结果就是控制准确性、精确度与实际过程的吻合程度较差。拟从干燥系统输入体系的结构入手,采用时序分析的手法对入粮到干燥的传输时序进行解析,推理出动态实时数据模型。 相似文献
109.
110.
地质超前预报和动态施工在隧洞施工中的应用 总被引:2,自引:0,他引:2
通过在直峰架洞施工过程中,地质超首预报与隧洞动态施工的结合,将国际岩体质量分级到生产实践中,针对不同级别的岩级,应用相应的施工方案,以达到为隧洞篱工总结经验的目的。 相似文献