全文获取类型
收费全文 | 75913篇 |
免费 | 6855篇 |
国内免费 | 4027篇 |
专业分类
电工技术 | 4266篇 |
技术理论 | 1篇 |
综合类 | 6894篇 |
化学工业 | 12476篇 |
金属工艺 | 4071篇 |
机械仪表 | 4800篇 |
建筑科学 | 4979篇 |
矿业工程 | 1624篇 |
能源动力 | 2178篇 |
轻工业 | 6764篇 |
水利工程 | 1464篇 |
石油天然气 | 2788篇 |
武器工业 | 545篇 |
无线电 | 9531篇 |
一般工业技术 | 8767篇 |
冶金工业 | 3199篇 |
原子能技术 | 1077篇 |
自动化技术 | 11371篇 |
出版年
2024年 | 221篇 |
2023年 | 825篇 |
2022年 | 1549篇 |
2021年 | 2229篇 |
2020年 | 1761篇 |
2019年 | 1634篇 |
2018年 | 1757篇 |
2017年 | 2035篇 |
2016年 | 2023篇 |
2015年 | 2692篇 |
2014年 | 3645篇 |
2013年 | 4434篇 |
2012年 | 5224篇 |
2011年 | 5719篇 |
2010年 | 5204篇 |
2009年 | 5184篇 |
2008年 | 5088篇 |
2007年 | 4846篇 |
2006年 | 4740篇 |
2005年 | 3968篇 |
2004年 | 3286篇 |
2003年 | 3002篇 |
2002年 | 3525篇 |
2001年 | 3080篇 |
2000年 | 2105篇 |
1999年 | 1531篇 |
1998年 | 1023篇 |
1997年 | 839篇 |
1996年 | 754篇 |
1995年 | 657篇 |
1994年 | 481篇 |
1993年 | 352篇 |
1992年 | 289篇 |
1991年 | 221篇 |
1990年 | 188篇 |
1989年 | 127篇 |
1988年 | 118篇 |
1987年 | 88篇 |
1986年 | 47篇 |
1985年 | 62篇 |
1984年 | 50篇 |
1983年 | 32篇 |
1982年 | 19篇 |
1981年 | 21篇 |
1980年 | 21篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 15篇 |
1976年 | 17篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Min Jeong Noh Tae Gyun Kim In Kwon Hong Ki-Pung Yoo 《Korean Journal of Chemical Engineering》1995,12(1):48-55
A new transparent microscale circulation-type high pressure equilibrium cell with on-line sampling was devised. With this
apparatus, experimental solubility of molecularly complex species such as steroids (cholesterol, stigmasterol and ergosterol)
and fatty acids (palmitic acid and stearic acid) in supercritical carbon dioxide(sc-C02) were measured. Also, to find an appropriate substance for enhancing both the polarity and the solubility power of the SC-CO2 solvent, we arbitrarily selected three polar substances such as acetone, methanol and water and the effect of these cosolvents
on the solubility of solutes in SC-CO2 are examined. The supercritical phase equilibrium data of solute-cosolvent-sc-CO2 systems were quantitatively correlated using a new equation of state based on the lattice fluid theory incorporated with
the concept of multibody interaction. We found that the addition of tracer amount of acetone or methanol to SC-CO2 enhances the solubility of all solutes about thirty to sixty times when compared with the case of pure sc-CO2 However, for the case of cosolvent water, no further enhancement of the solubility of solutes was realized. Also, the versatile
fittability of the equation of state proposed in this work was demonstrated with the newly measured ternary supercritical
equilibrium data. 相似文献
92.
93.
Certain new sulfide-smelting processes and coal-gasification processes generate high-strength sulfur dioxide streams, for
which a new process for converting sulfur dioxide to elemental sulfur needs to be developed because no process exists that
is generally and economically applicable to the treatment of such streams. A thermodynamic and experimental investigation
to develop a new process for converting sulfur dioxide to elemental sulfur by a cyclic process involving calcium sulfide and
calcium sulfate without generating secondary pollutants was carried out. In this process, the starting raw material, calcium
sulfate, is reduced by a suitable reducing agent, such as hydrogen, to produce calcium sulfide, which is used to reduce sulfur
dioxide to elemental sulfur vapor and calcium sulfate. The latter is, in turn, reduced to regenerate calcium sulfide. In this
Part I, detailed experimental results are presented on the kinetics of the reaction between sulfur dioxide and calcium-sulfide
pellets, which produces elemental sulfur and calcium sulfate. The experiments were carried out at temperatures between 1023
and 1088 K and sulfur-dioxide partial pressures between 9 and 60 kPa by the use of a thermogravimetric analysis (TGA) technique.
The rate of this reaction was demonstrated by the conversion of 40 pct calcium-sulfide pellets obtained from the hydrogen
reduction of fresh calcium sulfate in 10 minutes at 1073 K under a sulfur-dioxide partial pressure of 43 kPa. The reactivity
decreased somewhat during the first three cycles but remained largely unchanged thereafter up to the tenth cycle. This characteristic
of the pellets is important because the solids must be reusable for repeated cycles to avoid generating secondary pollutants.
A pore-blocking model was found to fit the reaction rate. The reaction is first order with respect to sulfur-dioxide partial
pressure and has an activation energy of 101 to 134 kJ/mol (24 to 32 kcal/mol) for calcium-sulfide pellets reacted and regenerated
several different times. Sulfur dioxide-containing streams from certain sources, such as the regenerator off-gas from an integrated-gasification,
combined-cycle, desulfurization unit and new sulfide-smelting plants, contain much higher partial pressures of SO2. In these cases, the rate of the first reaction is expected to be proportionally higher than in the test conditions reported
in this article. The reduction kinetics of calcium-sulfate pellets with hydrogen gas is reported in the accompanying Part
II. 相似文献
94.
95.
Won Tae KimCheolho Bai Young I. Cho 《International Journal of Heat and Mass Transfer》2002,45(3):597-607
The present study introduces a new experimental method to visualize the fouling process of CaCO3. A mini-channel heat exchanger system with a microscopic imaging technique was developed for real-time visualization of the fouling process. The present study discussed how scale started initially, how scale formed thick layers, and how a small crystal grew into a large one, touching the adjacent one. Detail microscopic images of scale crystals and corresponding fouling resistances were obtained over the entire fouling process. The microscopic observation indicated that the fouling process could be divided into three stages: an induction period, a period of uniform generation of nuclei, and a period of uniform growth of scale. Sudden appearance of numerous small nuclei indicated the end of the induction period, a key event before the rapid increase in the fouling resistance. The present experimental method using microscopic images of the wet fouling process provides a valuable insight on the fouling mechanism. 相似文献
96.
97.
当成千上万的农民远离穷困的村落,视而不见地掠过小城镇,径奔大城市寻梦或淘金,一个显见的事实是,大城市里有更多的就业机会,有更多的钱赚——从生存的角度看,只要条件具备,没有谁不愿意趋利避害。 站在政府的角度,秩序则是重要的。任何政府都担心刑事案件随着它的城市人口的暴涨而剧增,而且,这还不是惟一的,因为与“月黑风高夜,杀人放火天”的刑事案件相伴的至少还有贫民窟。杀人、放火、贫民窟等等一系列大城市综合症,恰恰是西方国家城市化道路的“遗产”,是发展中国家快速城市化的特产。 相似文献
99.
Liang Y.C. Wenjiang Zeng Pick Hong Ong Zhaoxia Gao Jun Cai Balasubramanian N. 《Electron Device Letters, IEEE》2002,23(12):700-703
In this letter, a concise process technology is proposed for the first time to enable the fabrication of good quality three-dimensional (3-D) suspended radio frequency (RF) micro-inductors on bulk silicon, without utilizing the lithography process on sidewall and trench-bottom patterning. Samples were fabricated to demonstrate the applicability of the proposed process technology. 相似文献
100.