全文获取类型
收费全文 | 1260篇 |
免费 | 40篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 36篇 |
化学工业 | 214篇 |
金属工艺 | 35篇 |
机械仪表 | 18篇 |
建筑科学 | 34篇 |
能源动力 | 95篇 |
轻工业 | 72篇 |
水利工程 | 1篇 |
无线电 | 180篇 |
一般工业技术 | 263篇 |
冶金工业 | 182篇 |
原子能技术 | 10篇 |
自动化技术 | 167篇 |
出版年
2023年 | 14篇 |
2022年 | 20篇 |
2021年 | 39篇 |
2020年 | 31篇 |
2019年 | 28篇 |
2018年 | 41篇 |
2017年 | 43篇 |
2016年 | 39篇 |
2015年 | 24篇 |
2014年 | 45篇 |
2013年 | 83篇 |
2012年 | 69篇 |
2011年 | 64篇 |
2010年 | 54篇 |
2009年 | 64篇 |
2008年 | 51篇 |
2007年 | 54篇 |
2006年 | 42篇 |
2005年 | 35篇 |
2004年 | 29篇 |
2003年 | 16篇 |
2002年 | 19篇 |
2001年 | 19篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 34篇 |
1997年 | 20篇 |
1996年 | 30篇 |
1995年 | 19篇 |
1994年 | 24篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1991年 | 10篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 6篇 |
1987年 | 17篇 |
1986年 | 6篇 |
1985年 | 16篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 17篇 |
1981年 | 24篇 |
1980年 | 15篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 4篇 |
排序方式: 共有1307条查询结果,搜索用时 15 毫秒
1.
2.
Sintering and grain growth of nano-crystalline undoped ZnO has been studied in detail over a wide range of temperature and holding time. Below 800 °C, sintering of over 70% theoretical density is not observed, irrespective of particle size. At 900 °C for 6 h, the nano-crystalline sample sinters to 99% of theoretical density whereas the density for as received sample is 93% of theoretical density. However, at 1300 °C or higher, the densification is found to be much faster and after a few hours becomes independent of holding time. Grain growth studies reveal a similar feature of attaining saturation over holding time. The average saturated grain size is found to be ∼1.5 and ∼2.2 μm at 800 and 900 °C, respectively, while at 1300 °C or higher, it is in between 12 and 13 μm. 相似文献
3.
McIntyre H. Wendell D. Lin K.J. Kaushik P. Seshadri S. Wang A. Sundararaman V. Ping Wang Song Kim Hsu W.-J. Hee-Choul Park Levinsky G. Jiejun Lu Chirania M. Heald R. Lazar P. Dharmasena S. 《Solid-State Circuits, IEEE Journal of》2005,40(1):52-59
A 4-MB L2 data cache was implemented for a 64-bit 1.6-GHz SPARC(r) RISC microprocessor. Static sense amplifiers were used in the SRAM arrays and for global data repeaters, resulting in robust and flexible timing operation. Elimination of the global clock grid over the SRAM array saves power, enabled by combining the clock information with array select signals. Redundancy was implemented flexibly, with shift circuits outside the main data array for area efficiency. The chip integrates 315 million transistors and uses an 8-metal-layer 90-nm CMOS process. 相似文献
4.
Kaushik A. Iyer 《International Journal of Fracture》2007,146(1-2):1-18
Internal fracture patterns developed in silicon carbide cylindrical targets as a result of dynamic indentation (63–500 m/s)
by tungsten carbide spheres are defined. Microscopy of recovered and sectioned targets delineate into three regions, each
associated with distinct cracking modes, i.e., shallow cone macrocracking at and near the impact surface, steep interior cone
macrocracks that radiate into the target from the impact region and local grain-scale microcracking directly underneath the
impact region. The observed fracture patterns are found to maintain a noticeable degree of self-similarity upto the impact
velocity of 500 m/s. Linear elastic analysis of the full (surface and interior) stress field developed under static (Hertz)
contact loading delineate the target into four regions, based on the number of principal stresses that are tensile (none,
1, 2 or all 3). A strong correlation is found between the principal stress conditions within each region and the forms of
cracking, their locations and orientations present therein. This correlation has a number of implications, including non-interaction
of crack systems, which are discussed. Illustrative linear elastic fracture mechanics analyses are performed for three regions,
and calculated and observed macrocrack lengths are found to be in reasonable agreement. 相似文献
5.
This paper presents an evaluation of various solid desiccant cycles for air conditioning in hot and humid climates. Psychometric evaluation of potential cycles for 16 typical Indian cities has been carried out with the objective of achieving standard comfort conditions in the room. Computer simulation is based on constant effectiveness of heat exchangers and evaporative coolers and actual performance data of a commercially available desiccant wheel dehumidifier. The influence of various outdoor conditions, the effectiveness of heat exchangers/evaporative coolers on the cooling coefficient of performance and volumetric air flowrate per unit cooling capacity have been investigated. It is found that amongst ventilation, recirculation and Dunkle cycles, the Dunkle cycle is better for a wide range of outdoor conditions. However, cycles using wet surface heat exchangers give even higher performance. 相似文献
6.
Animesh Chakrabarti Man Mohan Sharma 《Journal of the American Oil Chemists' Society》1992,69(12):1251-1253
Anhydrous esterification of myristic acid with propylene was carried out in the temperature range of 110–145°C and pressure
from 190–195 psig in the presence of Amberlyst-15 (cation exchange resin) and Filtrol-24 (acid-treated clay) as catalysts.
The product ester, isopropyl myristate finds use in cosmetic and topical medicinal preparations where good absorption through
the skin is desired. Filtrol-24 is the catalyst of choice, and the recommended operating temperature is 130°C with a pressure
of 190 psig. 相似文献
7.
8.
Debasmita Das Purabi Rani Samaddar Pratik Kumar Sen Kaushik Das 《Journal of Applied Electrochemistry》2008,38(6):743-749
Galvanostatic steady state current potential measurements were carried out for oxidation of a series of aliphatic alcohols
having varying number of hydroxyl groups. The anodically deposited layer of MnO2 on platinum was used as the electrode material. The deposit was characterised by scanning electron microscopy (SEM), energy
dispersive X-ray analysis (EDAX) and electrode potential measurements. The catalytic role of MnO2 in the electro-oxidation of alcohols was indicated by the chronopotentiograms and the cyclic voltammograms. An analysis of
the electrochemical data indicated a catalytic EC mechanism in which Mn (V) is generated electrochemically and consumed chemically
in succession. Based on this and the hydrogen bonding interaction between alcoholic hydroxyl groups and MnO2 layer, a mechanism was proposed which accounts for the variation in the observed electrochemical reaction orders. Tafel behaviour
was found to be followed only approximately. Current efficiency of the electrochemical oxidation of polyols was studied. Replacement
of platinum by carbon as current collector was found to leave the electrocatalytic activity of the MnO2 deposit practically unaltered. 相似文献
9.
A terahertz sensor that measures vibrations behind optically opaque barriers (cardboard, plastic, wool, cotton) is described and demonstrated. Using interferometric techniques, submicrometer displacements can be resolved. Measured spectral response agrees with commercial vibrometer 相似文献
10.