全文获取类型
收费全文 | 75628篇 |
免费 | 6839篇 |
国内免费 | 4191篇 |
专业分类
电工技术 | 3281篇 |
技术理论 | 1篇 |
综合类 | 5985篇 |
化学工业 | 17090篇 |
金属工艺 | 7582篇 |
机械仪表 | 3986篇 |
建筑科学 | 9924篇 |
矿业工程 | 2696篇 |
能源动力 | 2404篇 |
轻工业 | 4202篇 |
水利工程 | 1273篇 |
石油天然气 | 2095篇 |
武器工业 | 1251篇 |
无线电 | 3350篇 |
一般工业技术 | 15146篇 |
冶金工业 | 3986篇 |
原子能技术 | 531篇 |
自动化技术 | 1875篇 |
出版年
2024年 | 377篇 |
2023年 | 985篇 |
2022年 | 1970篇 |
2021年 | 2419篇 |
2020年 | 2469篇 |
2019年 | 2027篇 |
2018年 | 1942篇 |
2017年 | 2617篇 |
2016年 | 2658篇 |
2015年 | 2545篇 |
2014年 | 3869篇 |
2013年 | 3890篇 |
2012年 | 4926篇 |
2011年 | 5277篇 |
2010年 | 4193篇 |
2009年 | 4584篇 |
2008年 | 3739篇 |
2007年 | 5442篇 |
2006年 | 4962篇 |
2005年 | 4313篇 |
2004年 | 3482篇 |
2003年 | 3241篇 |
2002年 | 2685篇 |
2001年 | 2322篇 |
2000年 | 2023篇 |
1999年 | 1625篇 |
1998年 | 1243篇 |
1997年 | 1059篇 |
1996年 | 891篇 |
1995年 | 716篇 |
1994年 | 616篇 |
1993年 | 471篇 |
1992年 | 293篇 |
1991年 | 222篇 |
1990年 | 147篇 |
1989年 | 117篇 |
1988年 | 90篇 |
1987年 | 46篇 |
1986年 | 17篇 |
1985年 | 27篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 4篇 |
1980年 | 19篇 |
1979年 | 11篇 |
1959年 | 4篇 |
1956年 | 4篇 |
1955年 | 4篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Strain rate is not only an important measure to characterize the deformation property, but also an important parameter to analyze the dynamic mechanical properties of rock materials. In this paper, by using the SHPB test system improved with high temperature device, the dynamic compressive tests of sandstone at seven temperatures in the range of room temperature to 1000 °C and five impact velocities in the range of 11.0–15.0 m/s were conducted. Investigations were carried out on the influences of strain rate on dynamic compressive mechanical behaviors of sandstone. The results of the study indicate that the enhancement effects of strain rates on dynamic compressive strength, peak strain, energy absorption ratio of sandstone under high temperatures still exist. However, the increase ratios of dynamic compressive strength, peak strain, and energy absorption ratio of rock under high temperature compared to room temperature have no obvious strain rate effects. The temperatures at which the strain rates affect dynamic compressive strength and peak strain most, are 800, and 1000 °C, respectively. The temperatures at which the strain rates affect dynamic compressive strength and peak strain weakest, are 1000 °C, and room temperature, respectively. At 200 and 800 °C, the strain rate effect on energy absorption ratio are most significant, while at 1000 °C, it is weakest. There are no obvious strain rate effects on elastic modulus and increase ratio of elastic modulus under high temperatures. According to test results, the relationship formula of strain rate with high temperature and impact load was derived by internalizing fitting parameters. Compared with the strain rate effect at room temperature condition, essential differences have occurred in the strain rate effect of rock material under the influence of high temperature. 相似文献
3.
Monomers and their polymers containing 3-arylcarbazolyl electrophores have been synthesized by the multi-step synthetic route. The materials were characterized by thermo-gravimetric analysis, differential scanning calorimetry and electron photoemission technique. The polymers represent materials of high thermal stability having initial thermal degradation temperatures in the range of 331–411 °C. The glass transition temperatures of the amorphous polymeric materials were in the rage of 148–175 °C. The electron photoemission spectra of thin layers of monomers showed ionization potentials in the range of 5.6–5.65 eV. Hole-transporting properties of the polymers were tested in the structures of organic light emitting diodes with Alq3 as the green emitter. The device containing hole-transporting layers of polyether with 3-naphthylcarbazolyl groups exhibited the best overall performance with a maximum current efficiency of 3.3 cd/A and maximum brightness of about 1000 cd/m2. 相似文献
4.
介绍机械制造厂燃煤锅炉的烟尘特点,分析滤料失效的原因,提出一套针对该工况的滤料解决方案。介绍针对复杂工况条件所选用的纤维种类以及复合面层原料成分配比的确定,最终选用针刺工艺加工并对该新产品的基本性能进行了测试分析。 相似文献
5.
6.
Enhanced gravity, or centrifugal, separators have revolutionised gold processing over the past decades, significantly increasing the recovery of fine (−100 μm) free gold. One of the main drawbacks of centrifugal gravity concentrators is the large volume of water required (even if it is all recycled). With water becoming an ever increasingly important “commodity”, reducing this is of importance both from an environmental and a monetary point of view. This work investigated operating a laboratory scale Knelson Concentrator with a dry feed and using air as the fluidising medium. The feed used was a synthetic mixture of tungsten and quartz, used to mimic a gold ore. The response surface method and central composite design techniques were used to design the experiments and to model the results, with the experimental variables being the bowl speed (G-Level), air fluidising pressure and the feed rate. The models corresponded well to the experimental results, indicating that for this experimental setup, the optimal conditions were a bowl G-Level of 40 G, a feed rate of 220 g/min and an air fluidising pressure of 8 psi. 相似文献
7.
8.
垦71井区三维VSP资料波场分离方法应用研究 总被引:8,自引:5,他引:3
三维VSP资料是多偏移距VSP资料,资料中多种类型的波叠合在一起形成复杂波场。从复杂波场中分离出单一的保幅反射波波场是三维VSP波场分离的重要工作。常规二维VSP波场处理方法单一,难以适用于复杂的三维波场处理。针对三维VSP资料的波场特点,以分离上行反射P波为例,将单一波场分离方法加以适当组合,对垦71井区三维VSP实际资料进行了应用研究。结果表明,波场分离处理中叠加消去法和中值滤波相结合以及F—K滤波和中值滤波相结合的方法克服了单一方法的缺陷,波场处理后获得了波组特征明显、波场清晰单一的上行反射P波保幅波场,取得了较好的波场分离效果。 相似文献
9.
The basic methods of verifying continuous automatic belt weighers are described. A comparative analysis of these methods on the basis of experimental studies is made and ways of implementing the results in industry are recommended. 相似文献
10.
Ludmil Drenchev Jerzy Sobczak Rajiv Asthana Savko Malinov 《Journal of Computer-Aided Materials Design》2003,10(1):35-54
Ordered porosity metal materials belong to a relatively new class of porous materials named gasars. This paper presents a mathematical model of the complex physical phenomena in the production of gasars. Analyses for heat transfer, solidification kinetics and gas diffusion were coupled to describe the formation of unique gasar structure. Several criterial functions were introduced to provide significant quantitative information about the relationship between the operating technological parameters and the final structure. The computational outcomes of the numerical simulation were compared with the characteristics of real gasar ingots. The model was applied to determine the boundary conditions that would provide approximately constant physical conditions on the solidification front. The structure sensitiveness of gasars with respect to the different technological parameters is discussed. 相似文献