全文获取类型
收费全文 | 82879篇 |
免费 | 7455篇 |
国内免费 | 4399篇 |
专业分类
电工技术 | 5541篇 |
技术理论 | 3篇 |
综合类 | 5959篇 |
化学工业 | 13241篇 |
金属工艺 | 5006篇 |
机械仪表 | 5515篇 |
建筑科学 | 6579篇 |
矿业工程 | 2553篇 |
能源动力 | 2391篇 |
轻工业 | 6031篇 |
水利工程 | 1614篇 |
石油天然气 | 5075篇 |
武器工业 | 864篇 |
无线电 | 9443篇 |
一般工业技术 | 9466篇 |
冶金工业 | 3450篇 |
原子能技术 | 929篇 |
自动化技术 | 11073篇 |
出版年
2024年 | 317篇 |
2023年 | 1436篇 |
2022年 | 2574篇 |
2021年 | 3660篇 |
2020年 | 2829篇 |
2019年 | 2250篇 |
2018年 | 2487篇 |
2017年 | 2720篇 |
2016年 | 2395篇 |
2015年 | 3410篇 |
2014年 | 4361篇 |
2013年 | 4859篇 |
2012年 | 5656篇 |
2011年 | 6136篇 |
2010年 | 5456篇 |
2009年 | 5122篇 |
2008年 | 4939篇 |
2007年 | 4691篇 |
2006年 | 4606篇 |
2005年 | 3817篇 |
2004年 | 2726篇 |
2003年 | 2286篇 |
2002年 | 2242篇 |
2001年 | 1919篇 |
2000年 | 1811篇 |
1999年 | 1934篇 |
1998年 | 1513篇 |
1997年 | 1357篇 |
1996年 | 1171篇 |
1995年 | 963篇 |
1994年 | 779篇 |
1993年 | 556篇 |
1992年 | 476篇 |
1991年 | 298篇 |
1990年 | 253篇 |
1989年 | 202篇 |
1988年 | 140篇 |
1987年 | 91篇 |
1986年 | 71篇 |
1985年 | 48篇 |
1984年 | 39篇 |
1983年 | 28篇 |
1982年 | 33篇 |
1981年 | 21篇 |
1980年 | 18篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1959年 | 9篇 |
1951年 | 2篇 |
1940年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
茯砖茶发酵、干燥过程中,烘房内温湿度稳定性和能源系统低能耗是保证茯砖茶品质与成本的重要因素。本文采用TRNSYS仿真与实验研究相结合的方法,对咸阳某茯砖茶厂实际使用的空气源热泵系统进行建模,通过研究各季节典型代表月烘房温湿度的波动情况,确定该空气源热泵系统在全年的运行状态是否满足工艺要求,在此基础上,对比了该系统在全年可运行季节代表月与该生产厂房早期使用的燃气锅炉系统的能耗仿真结果,对空气源热泵系统的节能与环保特性进行研究。结果表明:由于夏季送风质量流量过大且室外空气含湿量较高,7月烘房温湿度不满足工艺要求。热泵系统在1、4、10月的总标煤消耗量的平均值是锅炉系统的44.42%,平均CO2、SO2、NOx排放量分别为锅炉系统的34.13%、44.1%、40.60%。在茯砖茶发酵、干燥的过程中,相比于燃气锅炉系统,空气源热泵系统具有更好的节能与环保特性。 相似文献
12.
Yan He Kangren Kong Zhengxi Guo Weifeng Fang Zaiqiang Ma Haihua Pan Ruikang Tang Zhaoming Liu 《Advanced functional materials》2021,31(26):2101291
Sensitivity and multi-directional motivation are major two factors for developing optimized humidity-response materials, which are promising for sensing, energy production, etc. Organic functional groups are commonly used as the water sensitive units through hydrogen bond interactions with water molecules in actuators. The multi-coordination ability of inorganic ions implies that the inorganic ionic compounds are potentially superior water sensitive units. However, the particle forms of inorganic ionic compounds produced by classical nucleation limit the number of exposed ions to interact with water. Recent progress on the inorganic ionic oligomers has broken through the limitation of classical nucleation, and realized the molecular-scaled incorporation of inorganic ionic compounds into an organic matrix. Here, the incorporation of hydrophilic calcium carbonate ionic oligomers into hydrophobic poly(vinylidene fluoride) (PVDF) is demonstrated. The ultra-small calcium carbonate oligomers within a PVDF film endow it with an ultra-sensitive, reversible, and bidirectional response. The motivation ability is superior to other bidirectional humidity-actuators at present, which realizes self-motivation on an ice surface, converting the chemical potential energy of the humidity gradient from ice to kinetic energy. 相似文献
13.
Wireless Networks - In such mobile platforms as ships and aircraft, the detection and reconnaissance devices are near to the communication facilities. When working at the same time, they will... 相似文献
14.
Juan Ding Yong He Shenhe Fu Xiangsheng Xie Haowen Liang Jianying Zhou 《Journal of the Society for Information Display》2022,30(2):159-167
Illumination is essential for modern life as colorful world is perceived by human visionary system. Display technology has been developing rapidly in recent decades, and the basic principle is related to the way that the image is illuminated and light is emanated. Traditional illumination is provided by different types of light sources, and the display image is visible in large viewing space until the emanating light decays to zero. This work proposes and demonstrates a novel illumination scheme for a display in which the displaying images are visible only in specific spatial regions. The directional backlight ensures the image propagating to specific direction while imaging visibility can be controlled to terminate abruptly at certain distance from the display screen while exerting no influence to nearby regions. The working principle for such an illumination scheme is the use of the modulated coherent directional backlight through an axicon lens. It is shown that the illumination scheme can robustly deliver carried image information to the designated viewing region. This new illumination scheme has many advantages over conventional illumination, including its usage for personal display, very lower energy consumption, as well as minimizing light hazard pollution. 相似文献
15.
16.
17.
Xian Suo Xili Cui Lifeng Yang Nan Xu Yuqi Huang Yi He Sheng Dai Huabin Xing 《Advanced materials (Deerfield Beach, Fla.)》2020,32(29):1907601
The design of highly stable and efficient porous materials is essential for developing breakthrough hydrocarbon separation methods based on physisorption to replace currently used energy-intensive distillation/absorption technologies. Efforts to develop advanced porous materials such as zeolites, coordination frameworks, and organic polymers have met with limited success. Here, a new class of ionic ultramicroporous polymers (IUPs) with high-density inorganic anions and narrowly distributed ultramicroporosity is reported, which are synthesized by a facile free-radical polymerization using branched and amphiphilic ionic compounds as reactive monomers. A covalent and ionic dual-crosslinking strategy is proposed to manipulate the pore structure of amorphous polymers at the ultramicroporous scale. The IUPs exhibit exceptional selectivity (286.1–474.4) for separating acetylene from ethylene along with high thermal and water stability, collaboratively demonstrated by gas adsorption isotherms and experimental breakthrough curves. Modeling studies unveil the specific binding sites for acetylene capture as well as the interconnected ultramicroporosity for size sieving. The porosity-engineering protocol used in this work can also be extended to the design of other ultramicroporous materials for the challenging separation of other key gas constituents. 相似文献
18.
19.
20.
Jie-Long He An-Te Chen Jyong-Huei Lee Shih-Kang Fan 《International journal of molecular sciences》2015,16(9):22319-22332
The basic structural and functional unit of a living organism is a single cell. To understand the variability and to improve the biomedical requirement of a single cell, its analysis has become a key technique in biological and biomedical research. With a physical boundary of microchannels and microstructures, single cells are efficiently captured and analyzed, whereas electric forces sort and position single cells. Various microfluidic techniques have been exploited to manipulate single cells through hydrodynamic and electric forces. Digital microfluidics (DMF), the manipulation of individual droplets holding minute reagents and cells of interest by electric forces, has received more attention recently. Because of ease of fabrication, compactness and prospective automation, DMF has become a powerful approach for biological application. We review recent developments of various microfluidic chips for analysis of a single cell and for efficient genetic screening. In addition, perspectives to develop analysis of single cells based on DMF and emerging functionality with high throughput are discussed. 相似文献