全文获取类型
收费全文 | 21258篇 |
免费 | 680篇 |
国内免费 | 46篇 |
专业分类
电工技术 | 297篇 |
综合类 | 55篇 |
化学工业 | 4055篇 |
金属工艺 | 490篇 |
机械仪表 | 489篇 |
建筑科学 | 1059篇 |
矿业工程 | 43篇 |
能源动力 | 513篇 |
轻工业 | 2374篇 |
水利工程 | 191篇 |
石油天然气 | 70篇 |
武器工业 | 1篇 |
无线电 | 1985篇 |
一般工业技术 | 3227篇 |
冶金工业 | 3631篇 |
原子能技术 | 223篇 |
自动化技术 | 3281篇 |
出版年
2023年 | 122篇 |
2022年 | 306篇 |
2021年 | 515篇 |
2020年 | 293篇 |
2019年 | 357篇 |
2018年 | 462篇 |
2017年 | 421篇 |
2016年 | 546篇 |
2015年 | 358篇 |
2014年 | 590篇 |
2013年 | 1193篇 |
2012年 | 899篇 |
2011年 | 1151篇 |
2010年 | 855篇 |
2009年 | 911篇 |
2008年 | 925篇 |
2007年 | 875篇 |
2006年 | 733篇 |
2005年 | 680篇 |
2004年 | 575篇 |
2003年 | 558篇 |
2002年 | 458篇 |
2001年 | 424篇 |
2000年 | 409篇 |
1999年 | 428篇 |
1998年 | 1127篇 |
1997年 | 738篇 |
1996年 | 559篇 |
1995年 | 421篇 |
1994年 | 353篇 |
1993年 | 371篇 |
1992年 | 216篇 |
1991年 | 200篇 |
1990年 | 207篇 |
1989年 | 211篇 |
1988年 | 185篇 |
1987年 | 151篇 |
1986年 | 164篇 |
1985年 | 205篇 |
1984年 | 163篇 |
1983年 | 138篇 |
1982年 | 110篇 |
1981年 | 133篇 |
1980年 | 129篇 |
1979年 | 122篇 |
1978年 | 81篇 |
1977年 | 144篇 |
1976年 | 197篇 |
1975年 | 91篇 |
1973年 | 94篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
11.
12.
Quality of Crude Fish Oil Extracted from Herring Byproducts of Varying States of Freshness 总被引:1,自引:0,他引:1
ABSTRACT: Herring byproducts were stored at 2 and 15 °C for up to 72 h. Over time, significant increases of total volatile bases (TVB), histamine, putrescine, cadaverine, and tyramine were detected. However, only tyramine and TVB levels were temperature-dependent. The level of total polyunsaturated fatty acids (PUFAs) was constant. Longer byproducts storage gave rise to an oil with higher levels of free fatty acids, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and total PUFAs, while fluorescent compounds were lower. A higher storage temperature led to oil higher in α-tocopherol and EPA levels and lower in anisidine value. Surprisingly, the oil with the highest content of PUFAs was not produced from the freshest byproducts, and oil with low oxidation products can be extracted from stored byproducts. 相似文献
13.
An extended model and calculus, called RasterCalc, is presented for operations on discrete graphics rasters, including their colour functions. The operations are separated into two main categories: operations on domains, and operations on colour functions. The operations are further classified as local and remote, depending on the correspondence between destination and source pixels. The new raster element or pixel can be a function of a single element from one or more rasters, a function of a small area from other rasters, or a function of entire rasters. Local operations have their main applications in computer graphics, while remote operations are more oriented towards image processing. A mathematically oriented notation is used to define and represent the operations included. RasterCalc has been implemented as a procedure package in Pascal, to be used on a powerful, yet expensive display. Recently a C version has been completed for a personal colour computer with a special chip for raster operations. The work reported in this paper is partially supplied by the Dutch Technical Sciences Foundation, under project number LWI 14.0130: “Facilities for raster graphics in programming languages” 相似文献
14.
Static light scattering was used to investigate dilute dispersions of fine gamma -Fe/sub 2/O/sub 3/ magnetic particles. The particles were acicular and on average 0.39 mu m long and 0.056 mu m in diameter. They were dispersed in organic solvents at concentrations of approximately 10/sup -4/ vol%, corresponding to an average interparticle separation of 9 mu m. Computer programs using a coupled dipole algorithm to predict the scattering from the particles were written. Experimental results do not agree with computer calculations of the light scattering from single particles, but are consistent with scattering from thick ropelike agglomerates of particles. The size of these agglomerates was estimated after 10 s to be less than 100 particles, while the thickness of the ropes is at least 5 particles.<> 相似文献
15.
Christian P. Romero Jonathan I. Avila Edgardo Cisternas Guerau B. Cabrera Alejandro L. Cabrera Kristiaan Temst Margriet J. Van Bael 《Journal of Materials Science》2007,42(18):7667-7672
Hydrogen desorption curves were obtained from a sample composed of a square arrangement of Co dots with average diameter of
4.4 μm, separated by a distance of 11.6 μm. A macroscopic sample of Co dots grown on a 2.5 × 2.5 cm Si substrate was made
by standard lithographic techniques and used in these experiments. Thermal programmed desorption (TPD) was performed under
ultra-high vacuum conditions. Hydrogen TPD curves were obtained from a 1 × 1 cm Co dots samples displaying a maximum of intensity
at 425 K. Hydrogen TPD curve was also obtained from 1 cm× 1 cm samples of Co films and Co foils for comparison. The hydrogen
TPD curves have decreasing intensity from the Co foils to the Co dots and finally to the Co films. This indicates that there
are more sites for hydrogen adsorption on the Co dots than in the Co films. This is a surprising result because there is approximately
8.7 times less Co atoms exposed in the Co dots that in the Co film sample. A desorption energy of 27 kcal/mol was obtained
for the Co dots suggesting that hydrogen is adsorbed on an hcp hollow site of the Co dot crystalline structure. 相似文献
16.
D. M. Van Wie D. G. Drewry Jr. D. E. King C. M. Hudson 《Journal of Materials Science》2004,39(19):5915-5924
Hypersonic flight powered by airbreathing engines offers the potential for faster response time at long ranges, and reduced cost for access-to-space. In the present paper the operating environment of typical hypersonic vehicles are discussed, including results for the radiation equilibrium wall temperature of external vehicle surfaces and the flow properties through three sample engines spanning the range of hydrocarbon-fueled Mach 4-8 flight and hydrogen-fueled flight at speeds up to Mach 17. Flow conditions at several locations through the sample engines were calculated to provide indications of the required operating flow environment. Additional system consideration such a seals, joints, vehicle integration and in-service engineering are addressed. 相似文献
17.
B.J.W. Waarsing M. Nuttin H. Van Brussel B. Corteville 《IEEE transactions on systems, man and cybernetics. Part C, Applications and reviews》2005,35(1):53-65
This paper presents our approach to extend the niche of behavior-based robotics toward manipulation. We use results from neuroscience to derive some qualitative design rules for the mechanics of the manipulator, resulting in a next-generation manipulator, the "soft arm". By defining the basic behaviors of the manipulator as trajectory-producing behaviors (which is also biologically plausible), we have designed a first test case: writing on a board with a mobile manipulator. The soft arm has not yet been developed; therefore, we have emulated such a soft robot arm on an industrial robot. 相似文献
18.
19.
20.
Farzaneh Fayazpour Bart Lucas Roosmarijn E. Vandenbroucke Stefaan Derveaux Jan Tavernier Sam Lievens Joseph Demeester Stefaan C. De Smedt 《Advanced functional materials》2008,18(18):2716-2723
To obtain more biologically relevant data there is a growing interest in the use of living cells for assaying the biological activity of unknown chemical compounds. Density ‘multiplex’ cell‐based assays, where different cell types are mixed in one well and simultaneously investigated upon exposure to a certain compound are beginning to emerge. To be able to identify the cells they should be attached to microscopic carriers that are encoded. This paper investigates how digitally encoded microparticles can be loaded with cells while keeping the digital code in the microcarriers readable. It turns out that coating the surface of the encoded microcarriers with polyelectrolytes using the layer‐by‐layer (LbL) approach provides the microcarriers with a ‘highly functional’ surface. The polyelectrolyte layer allows the growth of the cells, allows the orientation of the cell loaded microcarriers in a magnetic field, and does not hamper the reading of the code. It has further been shown that the cells growing on the polyelectrolyte layer can become transduced by adenoviral particles hosted by the polyelectrolyte layer. It is concluded that the digitally encoded microparticles are promising materials for use in biomedical and pharmaceutical in‐vitro research where cells are used as tools. 相似文献