全文获取类型
收费全文 | 6876篇 |
免费 | 503篇 |
国内免费 | 208篇 |
专业分类
电工技术 | 123篇 |
综合类 | 38篇 |
化学工业 | 1142篇 |
金属工艺 | 356篇 |
机械仪表 | 251篇 |
建筑科学 | 108篇 |
矿业工程 | 18篇 |
能源动力 | 186篇 |
轻工业 | 538篇 |
水利工程 | 10篇 |
石油天然气 | 330篇 |
武器工业 | 13篇 |
无线电 | 665篇 |
一般工业技术 | 964篇 |
冶金工业 | 2408篇 |
原子能技术 | 68篇 |
自动化技术 | 369篇 |
出版年
2023年 | 50篇 |
2022年 | 64篇 |
2021年 | 155篇 |
2020年 | 102篇 |
2019年 | 116篇 |
2018年 | 163篇 |
2017年 | 170篇 |
2016年 | 174篇 |
2015年 | 180篇 |
2014年 | 206篇 |
2013年 | 266篇 |
2012年 | 316篇 |
2011年 | 466篇 |
2010年 | 342篇 |
2009年 | 330篇 |
2008年 | 289篇 |
2007年 | 258篇 |
2006年 | 291篇 |
2005年 | 254篇 |
2004年 | 225篇 |
2003年 | 236篇 |
2002年 | 241篇 |
2001年 | 196篇 |
2000年 | 175篇 |
1999年 | 184篇 |
1998年 | 161篇 |
1997年 | 155篇 |
1996年 | 109篇 |
1995年 | 119篇 |
1994年 | 131篇 |
1993年 | 140篇 |
1992年 | 94篇 |
1991年 | 44篇 |
1990年 | 96篇 |
1989年 | 97篇 |
1988年 | 72篇 |
1987年 | 58篇 |
1986年 | 68篇 |
1985年 | 56篇 |
1984年 | 52篇 |
1983年 | 46篇 |
1981年 | 55篇 |
1979年 | 39篇 |
1978年 | 35篇 |
1977年 | 34篇 |
1975年 | 39篇 |
1974年 | 33篇 |
1971年 | 80篇 |
1970年 | 38篇 |
1968年 | 32篇 |
排序方式: 共有7587条查询结果,搜索用时 31 毫秒
1.
2.
Young Been Kim Sung Hyeon Jung Dong Su Kim Nishad G. Deshpande Hee Won Suh Hak Hyeon Lee Ji Hoon Choi Ho Seong Lee Hyung Koun Cho 《Advanced functional materials》2021,31(38):2102439
Antimony triselenide (Sb2Se3) nanoflake-based nitrogen dioxide (NO2) sensors exhibit a progressive bifunctional gas-sensing performance, with a rapid alarm for hazardous highly concentrated gases, and an advanced memory-type function for low-concentration (<1 ppm) monitoring repeated under potentially fatal exposure. Rectangular and cuboid shaped Sb2Se3 nanoflakes, comprising van der Waals planes with large surface areas and covalent bond planes with small areas, can rapidly detect a wide range of NO2 gas concentrations from 0.1 to 100 ppm. These Sb2Se3 nanoflakes are found to be suitable for physisorption-based gas sensing owing to their anisotropic quasi-2D crystal structure with extremely enlarged van der Waals planes, where they are humidity-insensitive and consequently exhibit an extremely stable baseline current. The Sb2Se3 nanoflake sensor exhibits a room-temperature/low-voltage operation, which is noticeable owing to its low energy consumption and rapid response even under a NO2 gas flow of only 1 ppm. As a result, the Sb2Se3 nanoflake sensor is suitable for the development of a rapid alarm system. Furthermore, the persistent gas-sensing conductivity of the sensor with a slow decaying current can enable the development of a progressive memory-type sensor that retains the previous signal under irregular gas injection at low concentrations. 相似文献
3.
Mani Balamurugan Hui‐Yun Jeong Venkata Surya Kumar Choutipalli Jung Sug Hong Hongmin Seo Natarajan Saravanan Jun Ho Jang Kang‐Gyu Lee Yoon Ho Lee Sang Won Im Venkatesan Subramanian Sun Hee Kim Ki Tae Nam 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(25)
The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions. 相似文献
4.
Seong‐Hee Kim 《Quality and Reliability Engineering International》2015,31(6):923-934
We present a distribution‐free tabular cumulative sum chart for monitoring the variability of an autocorrelated process. A quantity known as the asymptotic variance parameter is employed as a measure of the variability, and a distribution‐free tabular cumulative sum chart is applied to variance estimates calculated from batches of nonoverlapping samples. The proposed chart is applicable to a stationary process with a general marginal distribution and a general autocorrelation structure. It also determines control limits analytically without trial‐and‐error simulations. The performance of the proposed chart is tested on stationary processes with both normal and nonnormal marginals with various autocorrelation structures. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
5.
Spectral shape tunable band-rejection filter using a long-period fiber grating with divided coil heaters 总被引:2,自引:0,他引:2
Jun Kye Bae Sang Hyuck Kim Jun Hee Kim Jinho Bae Sang Bae Lee Je-Myung Jeong 《Photonics Technology Letters, IEEE》2003,15(3):407-409
We have developed a new type of tunable band rejection filter, which provides high spectral-shaping flexibility in a wide tuning range. The filter consists of a long-period fiber grating (LPFG) with divided coil heaters. Each of the divided coil heaters is controlled individually to adjust a temperature distribution along the LPFG and to modify the spectral shape of the LPFG filter. The tunable band rejection filter is demonstrated to function properly when applied as an erbium-doped fiber amplifier gain-flattening filter. 相似文献
6.
No authorship indicated 《Canadian Metallurgical Quarterly》2004,59(8):673
Provides the biography of Sheldon Cohen and announces that he has received the APA Award for Distinguished Scientific Contributions (2004) for his elegant research in psychoneuroimmunology. The award citation and a selected bibliography are also provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
量子密码技术被认为是绝对安全的加密技术。近年来,在美国、德国、日本和中国,相关研究都取得了明显进展。2004年6月,世界上第一个量子密码通信网络在美国马萨诸塞州剑桥城正式投入运行,标志着这一技术迈上了新台阶。据相关机构估算,量子保密通信系统一旦商用,将形成高达10亿美元的市场。 相似文献
8.
Maenghyo Cho Hee Yuel Roh 《International journal for numerical methods in engineering》2003,56(1):81-115
In the present study first‐order shear deformable shell finite elements based on general curvilinear co‐ordinates are proposed. For the development of the present shell elements, a partial mixed variational functional with independently assumed strains is provided in order to avoid the severe locking troubles known as transverse shear and membrane lockings. Bubble functions are included in the shape function of displacement to improve the performance of the developed element. The proposed assumed strain four‐ and nine‐node elements based on the general tensor shell theory provide an efficient linkage framework for shell surface modelling and finite element analysis. In the several benchmark problems, the present shell elements with exact geometric representations demonstrate their performance compared to previously reported results. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
9.
Boundary element analysis of thermal stress intensity factors for interface griffith and cusp cracks
Kang Yong Lee
Woon Cheon Baik
《Engineering Fracture Mechanics》1994,47(6):909-918The thermal stress intensity factors for interface cracks of Griffith and symmetric lip cusp types under vertical uniform heat flow in a finite body are calculated by the boundary element method. The boundary conditions on the crack surfaces are insulated or fixed to constant temperature. The relationship between the stress intensity factors and the displacements on the nodal point of a crack-tip element is derived. The numerical values of the thermal stress intensity factors for an interface Griffith crack in an infinite body are compared with the previous solutions. The thermal stress intensity factors for a symmetric lip cusp interface crack in a finite body are calculated with respect to various effective crack lengths, configuration parameters, material property ratios and the thermal boundary conditions on the crack surfaces. Under the same outer boundary conditions, there are no appreciable differences in the distribution of thermal stress intensity factors with respect to each material property. However, the effect of crack surface thermal boundary conditions on the thermal stress intensity factors is considerable. 相似文献
10.
No authorship indicated 《Canadian Metallurgical Quarterly》1997,52(8):912
Presents a list of American Psychological Foundation contributors for 1996. Individuals listed have donated through gifts of cash, securities, royalties, or through the Legacy Club (LC). LC donations are provided in wills, life insurance policies, trusts, and other gift arrangements. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献