全文获取类型
收费全文 | 53728篇 |
免费 | 6782篇 |
国内免费 | 4098篇 |
专业分类
电工技术 | 5899篇 |
技术理论 | 3篇 |
综合类 | 5187篇 |
化学工业 | 9181篇 |
金属工艺 | 2237篇 |
机械仪表 | 4274篇 |
建筑科学 | 3002篇 |
矿业工程 | 1681篇 |
能源动力 | 5297篇 |
轻工业 | 1187篇 |
水利工程 | 5484篇 |
石油天然气 | 3998篇 |
武器工业 | 631篇 |
无线电 | 2222篇 |
一般工业技术 | 4499篇 |
冶金工业 | 2813篇 |
原子能技术 | 1509篇 |
自动化技术 | 5504篇 |
出版年
2024年 | 235篇 |
2023年 | 829篇 |
2022年 | 1606篇 |
2021年 | 1858篇 |
2020年 | 1906篇 |
2019年 | 1661篇 |
2018年 | 1545篇 |
2017年 | 1955篇 |
2016年 | 2177篇 |
2015年 | 2223篇 |
2014年 | 3087篇 |
2013年 | 3651篇 |
2012年 | 3647篇 |
2011年 | 4213篇 |
2010年 | 2898篇 |
2009年 | 3147篇 |
2008年 | 2926篇 |
2007年 | 3474篇 |
2006年 | 3240篇 |
2005年 | 2913篇 |
2004年 | 2400篇 |
2003年 | 2144篇 |
2002年 | 1733篇 |
2001年 | 1476篇 |
2000年 | 1268篇 |
1999年 | 1076篇 |
1998年 | 878篇 |
1997年 | 748篇 |
1996年 | 706篇 |
1995年 | 625篇 |
1994年 | 519篇 |
1993年 | 407篇 |
1992年 | 345篇 |
1991年 | 214篇 |
1990年 | 219篇 |
1989年 | 162篇 |
1988年 | 122篇 |
1987年 | 86篇 |
1986年 | 67篇 |
1985年 | 30篇 |
1984年 | 46篇 |
1983年 | 33篇 |
1982年 | 20篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 18篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1959年 | 21篇 |
1951年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
961.
This paper presents a new power system planning strategy which combines firefly algorithm (FFA) with pattern search algorithm (PS). The purpose is minimizing total fuel cost, total power loss and reducing total voltage deviation, with the objective of enhancing the loading margin stability and consequently the power system security. A new interactive and simple mechanism, inspired in brainstorming process, is proposed that allows FFA and PS algorithms to explore new regions of the search space. In this study the Static VAR compensator (SVC) is modeled and integrated in an efficient location which is chosen considering the voltage stability index. The proposed algorithm is interactive and tries to optimize a set of control variables at the same time, namely, active power generations, voltage of generators, tap transformers, and the reactive power of shunt compensators to optimize three objective functions such as: fuel cost, total power loss and total voltage deviation. These variables are optimized using a flexible interactive and competitive search mechanism. The proposed planning strategy has been examined and applied to two practical test systems IEEE 14-Bus and IEEE 30-Bus. Simulation results confirm the effectiveness of this hybrid strategy for solving the security optimal power flow. 相似文献
962.
963.
邢立峰 《计算机测量与控制》2015,23(1):304-306, 316
针对现有的云计算工作流调度方法侧重于节能和可靠性等方面进行研究,忽略了安全性约束的要求,设计了一种基于协同禁忌算法的具有安全型约束的能实现云计算工作流高效调度的方法;首先,定义了云计算工作流调度的DAG图,对安全性约束进行了形式化描述,并建立了云计算工作流调度的数学模型;然后,在经典的协同禁忌算法的基础上,通过设计解的编码方式、适应度函数、变邻域结构和双禁忌表,实现对经典的协同禁忌算法进行改进;最后,定义了基于改协同禁忌算法实现对云计算工作流调度的具体算法;在云计算的仿真环境Cloud-Sim下进行实验,实验结果证明了文中方法不仅具有较快的收敛速度,而且能寻求到比其它方法更优的调度方案,能满足安全性约束要求,是一种可行实用的调度方法. 相似文献
964.
李洪洋 《网络安全技术与应用》2013,(10):63-64
伴随着互联网技术与网络业务的快速发展,网络规模逐渐扩大,网络运用开始逐步朝多元化、多样化以及复杂化的方向发展.现今,网络流量监测已经逐渐发展为计算机网络运用当中一个必不可少的内容与环节.文章将对网络异常流量加以说明,并对网络异常流量检测技术研究与实现进行分析与研究. 相似文献
965.
X. Chen H. He G. Zou X. Zhang X. Gu J. Hua 《Computer Vision and Image Understanding》2013,117(9):1107-1118
This paper presents an improved Euclidean Ricci flow method for spherical parameterization. We subsequently invent a scale space processing built upon Ricci energy to extract robust surface features for accurate surface registration. Since our method is based on the proposed Euclidean Ricci flow, it inherits the properties of Ricci flow such as conformality, robustness and intrinsicalness, facilitating efficient and effective surface mapping. Compared with other surface registration methods using curvature or sulci pattern, our method demonstrates a significant improvement for surface registration. In addition, Ricci energy can capture local differences for surface analysis as shown in the experiments and applications. 相似文献
966.
967.
968.
Jonathan A. Czuba James L. Best Kevin A. Oberg Daniel R. Parsons P. Ryan Jackson Marcelo H. Garcia Peter Ashmore 《Journal of Great Lakes research》2011,37(3):480-493
An integrated multibeam echo sounder and acoustic Doppler current profiler field survey was conducted in July 2008 to investigate the morphodynamics of the St. Clair River at the outlet of Lake Huron. The principal morphological features of the upper St. Clair River included flow-transverse bedforms that appear weakly mobile, erosive bedforms in cohesive muds, thin non-cohesive veneers of weakly mobile sediment that cover an underlying cohesive (till or glacio-lacustrine) surface, and vegetation that covers the bed. The flow was characterized by acceleration as the banks constrict from Lake Huron into the St. Clair River, an approximately 1500-m long region of flow separation downstream from the Blue Water Bridge, and secondary flow connected to: i) channel curvature; ii) forcing of the flow by local bed topography, and iii) flow wakes in the lee side of ship wrecks. Nearshore, sand-sized, sediment from Lake Huron was capable of being transported into, and principally along, the banks of the upper St. Clair River by the measured flow. A comparison of bathymetric surveys conducted in 2007 and 2008 identifies that the gravel bed does undergo slow downstream movement, but that this movement does not appear to be generated by the mean flow, and could possibly be caused by ship-propeller-induced turbulence. The study results suggest that the measured mean flow and dredging within the channel have not produced major scour of the upper St. Clair River and that the recent fall in the level of Lake Huron is unlikely to have been caused by these mechanisms. 相似文献
969.
970.