全文获取类型
收费全文 | 9063篇 |
免费 | 1272篇 |
国内免费 | 926篇 |
专业分类
电工技术 | 703篇 |
技术理论 | 1篇 |
综合类 | 942篇 |
化学工业 | 358篇 |
金属工艺 | 169篇 |
机械仪表 | 505篇 |
建筑科学 | 471篇 |
矿业工程 | 231篇 |
能源动力 | 151篇 |
轻工业 | 152篇 |
水利工程 | 207篇 |
石油天然气 | 243篇 |
武器工业 | 326篇 |
无线电 | 2338篇 |
一般工业技术 | 646篇 |
冶金工业 | 237篇 |
原子能技术 | 391篇 |
自动化技术 | 3190篇 |
出版年
2024年 | 40篇 |
2023年 | 132篇 |
2022年 | 262篇 |
2021年 | 312篇 |
2020年 | 341篇 |
2019年 | 336篇 |
2018年 | 249篇 |
2017年 | 353篇 |
2016年 | 423篇 |
2015年 | 460篇 |
2014年 | 591篇 |
2013年 | 677篇 |
2012年 | 655篇 |
2011年 | 649篇 |
2010年 | 544篇 |
2009年 | 590篇 |
2008年 | 522篇 |
2007年 | 638篇 |
2006年 | 544篇 |
2005年 | 456篇 |
2004年 | 357篇 |
2003年 | 303篇 |
2002年 | 284篇 |
2001年 | 250篇 |
2000年 | 214篇 |
1999年 | 193篇 |
1998年 | 140篇 |
1997年 | 132篇 |
1996年 | 106篇 |
1995年 | 111篇 |
1994年 | 70篇 |
1993年 | 70篇 |
1992年 | 62篇 |
1991年 | 42篇 |
1990年 | 41篇 |
1989年 | 20篇 |
1988年 | 14篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1957年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
1.
2.
We introduce a new architecture for the design of a tool for modeling and simulation of continuous and hybrid systems. The environment includes a compiler based on Modelica, a modular and a causal standard specification language for physical systems modeling (the tool supports models composed using certain component classes defined in the Modelica Standard Library, and the instantiation, parameterization and connection of these MSL components are described using a subset of Modelica). Models are defined in Modelica and are translated into DEVS models. DEVS theory (originally defined for modeling and simulation of discrete event systems) was extended in order to permit defining these of models. The different steps in the compiling process are show, including how to model these dynamic systems under the discrete event abstraction, including examples of model simulation with their execution results. 相似文献
3.
Very high resolution inverse synthetic aperture radar (ISAR) imaging of fast rotating targets is a complicated task. There may be insufficient pulses or may introduce migration through range cells (MTRC) during the coherent processing interval (CPI) when we use the conventional range Doppler (RD) ISAR technique. With compressed sensing (CS) technique, we can achieve the high-resolution ISAR imaging of a target with limited number of pulses. Sparse representation based method can achieve the super resolution ISAR imaging of a target with a short CPI, during which the target rotates only a small angle and the range migration of the scatterers is small. However, traditional CS-based ISAR imaging method generally faced with the problem of basis mismatch, which may degrade the ISAR image. To achieve the high resolution ISAR imaging of fast rotating targets, this paper proposed a pattern-coupled sparse Bayesian learning method for multiple measurement vectors, i.e. the PC-MSBL algorithm. A multi-channel pattern-coupled hierarchical Gaussian prior is proposed to model the pattern dependencies among neighboring range cells and correct the MTRC problem. The expectation-maximization (EM) algorithm is used to infer the maximum a posterior (MAP) estimate of the hyperparameters. Simulation results validate the effectiveness and superiority of the proposed algorithm. 相似文献
4.
Madhab Chandra Tripathy Debasmita Mondal Karabi Biswas Siddhartha Sen 《International Journal of Circuit Theory and Applications》2015,43(6):776-792
The present work reports the realization of an analog fractional‐order phase‐locked loop (FPLL) using a fractional capacitor. The expressions for bandwidth, capture range, and lock range of the FPLL have been derived analytically and then compared with the experimental observations using LM565 IC. It has been observed that bandwidth and capture range can be extended by using FPLL. It has also been found that FPLL can provide faster response and lower phase error at the time of switching compared to its integer‐order counterpart. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
5.
Defects are often present in rolled products, such as wire rod. The market demand for wire rod without any defects has increased. In the final wire rod products, defects originating from steel making, casting, pre‐rolling of billets and during wire rod rolling can appear. In this work, artificial V‐shaped longitudinal surface cracks have been analysed experimentally and by means of FEM. The results indicate that the experiments and FEM calculations show the same tendency except in two cases, where instability due to fairly “round” false round bars disturbed the experiment. FE studies in combination with practical experiments are necessary in order to understand the behaviour of the material flows in the groove and to explain whether the crack will open up as a V‐shape or if it will be closed as an I‐shape. 相似文献
6.
四川盆地上三叠统划分对比研究 总被引:36,自引:6,他引:30
四川盆地上三叠统对比长期存在混乱,给盆地整体评价带来困难。通过岩石地层、地震地层、事件地层及高分辨率旋回地层等多种方法讨论了须家河组与香溪群各岩性段的对比关系,得出了全盆地上三叠统的对比关系;指出须四段底可近似看成等时界面;须家河组下部地层自西向东、向南逐层超覆在雷口坡组之上,上部地层在盆地西北部自东南向西北方向剥蚀层位渐次变老。文章建议四川盆地上三叠统废除“香溪群”,统一使用“须家河组”,以利于对全盆地上三叠统进行油气资源整体评价与深化研究。 相似文献
7.
网络安全事件的关联分析方法的比较研究 总被引:2,自引:0,他引:2
随着当前攻击手段和技术的日益复杂化,一次入侵事件往往需要多个步骤才能完成,这些步骤都是彼此相关的。但是传统的入侵检测集中于检测底层的入侵或异常,所检测到的结果也仅仅是一次完整入侵的一部分,所以不能将不同的报警结合起来以发现入侵的逻辑步骤或者入侵背后的攻击策略。关联分析技术将不同分析器上产生的报警进行融合与关联分析,极大地减少了报警的数量,降低了入侵检测的误报率,并且适当的减少了入侵检测的漏报率。文中在对网络安全事件关联分析方法的系统结构进行分析后,着重介绍了当前比较流行的几种网络安全事件关联分析方法,最后对各种方法进行了比较研究。 相似文献
8.
连续波半主动雷达制导空空导弹截获跟踪距离计算 总被引:1,自引:1,他引:0
分析了连续波半主动雷达制导导弹导引头工作电磁环境和对武器系统攻击区的影响,建立了热噪声和杂波干扰环境下导引头截获距离方程,分析推导了直波泄漏干扰,地杂波干扰的计算公式,并在此基础上给出了导弹允许攻击区计算公式。 相似文献
9.
10.