全文获取类型
收费全文 | 2221篇 |
免费 | 177篇 |
国内免费 | 105篇 |
专业分类
电工技术 | 127篇 |
技术理论 | 1篇 |
综合类 | 125篇 |
化学工业 | 301篇 |
金属工艺 | 106篇 |
机械仪表 | 143篇 |
建筑科学 | 203篇 |
矿业工程 | 71篇 |
能源动力 | 64篇 |
轻工业 | 166篇 |
水利工程 | 36篇 |
石油天然气 | 222篇 |
武器工业 | 14篇 |
无线电 | 245篇 |
一般工业技术 | 222篇 |
冶金工业 | 139篇 |
原子能技术 | 62篇 |
自动化技术 | 256篇 |
出版年
2024年 | 9篇 |
2023年 | 25篇 |
2022年 | 91篇 |
2021年 | 92篇 |
2020年 | 69篇 |
2019年 | 64篇 |
2018年 | 45篇 |
2017年 | 65篇 |
2016年 | 67篇 |
2015年 | 106篇 |
2014年 | 108篇 |
2013年 | 125篇 |
2012年 | 180篇 |
2011年 | 184篇 |
2010年 | 121篇 |
2009年 | 117篇 |
2008年 | 124篇 |
2007年 | 128篇 |
2006年 | 101篇 |
2005年 | 86篇 |
2004年 | 82篇 |
2003年 | 89篇 |
2002年 | 53篇 |
2001年 | 47篇 |
2000年 | 53篇 |
1999年 | 68篇 |
1998年 | 31篇 |
1997年 | 32篇 |
1996年 | 28篇 |
1995年 | 37篇 |
1994年 | 27篇 |
1993年 | 16篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有2503条查询结果,搜索用时 31 毫秒
1.
Zhao Jiandong Lei Wei Li Zijian Zhao Dongfeng Han Mingmin Hou Xiaoqing 《Multimedia Tools and Applications》2022,81(4):4753-4780
Multimedia Tools and Applications - The crowding in bus is an important factor affecting passenger satisfaction and bus dispatching level. However, how to use video images to detect crowding... 相似文献
2.
Because of its ability to change optical absorption dynamically by applied electric field, nickel oxide (NiO) is a promising anodic material in smart windows, which can improve energy conversion efficiency in construction buildings. Although many works have achieved high electrochromic performance with different method. The underlying mechanism is still not fully investigated. In this article, we prepared the NiO films with large specific surface area and high stability by electron beam evaporation. X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to figure out the surface morphology and composition of as-deposited films. Afterwards, the electrochemical properties and optical performance of the prepared NiO films were investigated. On this basis, the origin of surface charge was fully analyzed by cyclic voltammetry and diffusion coefficient test. These experimental and theoretical results firmly confirm that both the surface reaction and capacitive effect bring about the excellent EC performance in NiO films. These results not only provide clear evidence about electrochemical kinetics in NiO films, but also offer some useful guidelines for the design of EC materials with higher performance and longer stability. 相似文献
3.
4.
5.
A device that harnesses the mechanical energy of skeletal muscle contracting in a linear configuration has been implanted in goats. This energy convertor transforms muscle work to hydraulic energy that could drive a variety of cardiac assist devices. The device is mounted with a rib clamp and plate affixed to the sternum by cortical bone screws. A transcutaneous hydraulic line carries a silicon based working fluid to an external system that controls the muscle load. In 60 to 70 kg goats, the latissimus dorsi insertion was reattached to the energy convertor. A Telectronics myostimulator with intramuscular electrodes stimulated the latissimus dorsi. In acute implants, hydraulic pressures in excess of 150 psi were obtained. Chronic implantation of the device allowed system evaluation in the conscious unanesthetized animal. Two weeks after implant, hydraulic pressures in excess of 200 psi were obtained and energy transferred to the external loading system exceeded 1 J per contraction. Six weeks after implant, the device continued to cycle freely. These initial results are very promising and suggest an implantable energy convertor is feasible. Development of an energy convertor is an important step toward tether-free skeletal muscle powered cardiac assist devices. 相似文献
6.
GMPLS在自动交换光网络控制平面中的应用 总被引:2,自引:0,他引:2
自动交换光网络(ASON)由于引入了控制平面才成为智能的光网络,而控制平面的具体实现要依靠通用多协议标记交换(GMPLS)协议。首先讨论ASON中的控制平面,然后对GMPLS和MPLS进行比较;最后对GMPLS在ASON控制平面中的应用进行了具体分析。 相似文献
7.
DDS+PLL系统的频谱分析 总被引:4,自引:0,他引:4
简要介绍了 DDS+PLL频率合成的原理,分析了在 DDS没有相位截断误差时,DDS+PLL输出信号的杂散抑制度,并讨论了杂散抑制度与环路参数的关系。 相似文献
8.
Software plays an increasingly important role in modern safety-critical systems. Although, research has been done to integrate software into the classical probabilistic risk assessment (PRA) framework, current PRA practice overwhelmingly neglects the contribution of software to system risk. Dynamic probabilistic risk assessment (DPRA) is considered to be the next generation of PRA techniques. DPRA is a set of methods and techniques in which simulation models that represent the behavior of the elements of a system are exercised in order to identify risks and vulnerabilities of the system. The fact remains, however, that modeling software for use in the DPRA framework is also quite complex and very little has been done to address the question directly and comprehensively. This paper develops a methodology to integrate software contributions in the DPRA environment. The framework includes a software representation, and an approach to incorporate the software representation into the DPRA environment SimPRA. The software representation is based on multi-level objects and the paper also proposes a framework to simulate the multi-level objects in the simulation-based DPRA environment. This is a new methodology to address the state explosion problem in the DPRA environment. This study is the first systematic effort to integrate software risk contributions into DPRA environments. 相似文献
9.
薄层反射波非零炮检距的属性特征 总被引:1,自引:0,他引:1
本文从薄层顶、底界面反射波的走时入手,研究了薄层反射波在非零炮检距集上出现的干涉现象,导出了薄层反射波在出现干涉时的炮检距计算公式,说明薄层干涉出现的炮检距是多变量函数,即随着埋藏深度h、地层速度v、薄层厚度Δh以及地震波的主频f*的变化而改变。本文重点分析了地层厚度Δh和地震子波主频f*对反射波振幅特性和频率特性的影响。在充分分析薄层反射的振幅、频谱随炮检距变化关系的基础上,指出在应用叠前信息(如AVO分析)进行储层预测等方面的研究时,应充分考虑薄层反射波的干涉和调谐现象带来的振幅和频率特征的变化。 相似文献
10.