首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1443篇
  免费   64篇
  国内免费   19篇
电工技术   15篇
综合类   4篇
化学工业   409篇
金属工艺   24篇
机械仪表   41篇
建筑科学   64篇
矿业工程   2篇
能源动力   105篇
轻工业   91篇
水利工程   26篇
石油天然气   10篇
无线电   151篇
一般工业技术   272篇
冶金工业   130篇
原子能技术   10篇
自动化技术   172篇
  2024年   10篇
  2023年   16篇
  2022年   56篇
  2021年   87篇
  2020年   65篇
  2019年   73篇
  2018年   91篇
  2017年   95篇
  2016年   65篇
  2015年   39篇
  2014年   58篇
  2013年   140篇
  2012年   95篇
  2011年   101篇
  2010年   50篇
  2009年   65篇
  2008年   53篇
  2007年   28篇
  2006年   27篇
  2005年   32篇
  2004年   31篇
  2003年   30篇
  2002年   8篇
  2001年   5篇
  2000年   2篇
  1999年   4篇
  1998年   38篇
  1997年   22篇
  1996年   14篇
  1995年   8篇
  1994年   13篇
  1993年   13篇
  1992年   11篇
  1991年   6篇
  1990年   8篇
  1989年   6篇
  1988年   4篇
  1987年   7篇
  1986年   5篇
  1985年   6篇
  1984年   7篇
  1983年   2篇
  1980年   5篇
  1978年   3篇
  1977年   3篇
  1976年   8篇
  1972年   1篇
  1970年   4篇
  1969年   1篇
  1968年   1篇
排序方式: 共有1526条查询结果,搜索用时 15 毫秒
1.
2.
One specific class of non-linear evolution equations, known as the Tzitzéica-type equations, has received great attention from a group of researchers involved in non-linear science. In this article, new exact solutions of the Tzitzéica-type equations arising in non-linear optics, including the Tzitzéica, Dodd–Bullough–Mikhailov and Tzitzéica–Dodd–Bullough equations, are obtained using the expa function method. The integration technique actually suggests a useful and reliable method to extract new exact solutions of a wide range of non-linear evolution equations.  相似文献   
3.

Considering the internet of things (IoT), end nodes such as wireless sensor network, RFID and embedded systems are used in many applications. These end nodes are known as resource-constrained devices in the IoT network. These devices have limitations such as computing and communication power, memory capacity and power. Key pre-distribution schemes (KPSs) have been introduced as a lightweight solution to key distribution in these devices. Key pre-distribution is a special type of key agreement that aims to select keys called session keys in order to establish secure communication between devices. One of these design types is the using of combinatorial designs in key pre-distribution, which is a deterministic scheme in key pre-distribution and has been considered in recent years. In this paper, by introducing a key pre-distribution scheme of this type, we stated that the model introduced in the two benchmarks of KPSs comparability had full connectivity and scalability among the designs introduced in recent years. Also, in recent years, among the combinatorial design-based key pre-distribution schemes, in order to increase resiliency as another criterion for comparing KPSs, attempts were made to include changes in combinatorial designs or they combine them with random key pre-distribution schemes and hybrid schemes were introduced that would significantly reduce the design connectivity. In this paper, using theoretical analysis and maintaining full connectivity, we showed that the strength of the proposed design was better than the similar designs while maintaining higher scalability.

  相似文献   
4.
Microsystem Technologies - The purpose of the present enquiry is to analyse the mechanics of an incompressible fluid, with water as base fluid, through a radially symmetric plumb duct with...  相似文献   
5.
In this paper, cenosphere particles embedded in AA2014 aluminium matrix are used to fabricate syntactic foam by stir casting method. The particle size is about 100?µm and foam density is about 1990?kg?m?3. Compression tests at strain rate 0.001/s are performed on foam samples to characterise their mechanical properties which are then used in numerical analysis on commercial finite element analysis software ABAQUS/CAE with isotropic elastic-plastic material model. Experimental and numerical results show good conformity in deformation behaviour with elastic and plateau zones showing average deviations less than 5% and 20%, respectively. Foams showed high yield stress and energy absorption capabilities that can be useful in making blast and impact resistant structures.  相似文献   
6.
Nanofluids have been known as practical materials to ameliorate heat transfer within diverse industrial systems. The current work presents an empirical study on forced convection effects of Al2O3–water nanofluid within an annulus tube. A laminar flow regime has been considered to perform the experiment in high Reynolds number range using several concentrations of nanofluid. Also, the boundary conditions include a constant uniform heat flux applied on the outer shell and an adiabatic condition to the inner tube. Nanofluid particle is visualized with transmission electron microscopy to figure out the nanofluid particles. Additionally, the pressure drop is obtained by measuring the inlet and outlet pressure with respect to the ambient condition. The experimental results showed that adding nanoparticles to the base fluid will increase the heat transfer coefficient (HTC) and average Nusselt number. In addition, by increasing viscosity effects at maximum Reynolds number of 1140 and increasing nanofluid concentration from 1% to 4% (maximum performance at 4%), HTC increases by 18%.  相似文献   
7.
In this letter, we introduce and investigate a new problem referred to as the All Hops Shortest Paths (AHSP) problem. The AHSP problem involves selecting, for all hop counts, the shortest paths from a given source to any other node in a network. We derive a tight lower bound on the worst-case computational complexities of the optimal comparison-based solutions to AHSP.  相似文献   
8.
Bias-temperature instabilities (BTI) of HfO/sub 2/ metal oxide semiconductor field effect transistors (MOSFETs) have been systematically studied for the first time. NMOS positive BTI (PBTI) exhibited a more significant V/sub t/ instability than that of PMOS negative BTI (NBTI), and limited the lifetime of HfO/sub 2/ MOSFETs. Although high-temperature forming gas annealing (HT-FGA) improved the interface quality by passivating the interfacial states with hydrogen, BTI behaviors were not strongly affected by the technique. Charge pumping measurements were extensively used to investigate the nature of the BTI degradation, and it was found that V/sub t/ degradation of NMOS PBTI was primarily caused by charge trapping in bulk HfO/sub 2/ rather than interfacial degradation. Deuterium (D/sub 2/) annealing was found to be an excellent technique to improve BTI immunity as well as to enhance the mobility of HfO/sub 2/ MOSFETs.  相似文献   
9.
10.
The path probability method (PPM) of irreversible statistical mechanics has been successfully applied to various diffusion problems. The major advantage of this atomistic treatment over the phenomenological approach of irreversible thermodynamics is that all Onsager matrix coefficients can be derived analytically so that relations among measurable quantities can be clearly understood in terms of microscopic parameters. This review article attempts to present the PPM in the simplest possible form. The importance of the PPM as an atomistic technique is illustrated using a simple example. The applicability and limitations of the technique are also emphasized.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号