全文获取类型
收费全文 | 102787篇 |
免费 | 12666篇 |
国内免费 | 5717篇 |
专业分类
电工技术 | 14004篇 |
技术理论 | 18篇 |
综合类 | 7816篇 |
化学工业 | 18224篇 |
金属工艺 | 3636篇 |
机械仪表 | 4371篇 |
建筑科学 | 12194篇 |
矿业工程 | 2370篇 |
能源动力 | 17033篇 |
轻工业 | 3174篇 |
水利工程 | 2035篇 |
石油天然气 | 3087篇 |
武器工业 | 820篇 |
无线电 | 7214篇 |
一般工业技术 | 11242篇 |
冶金工业 | 4536篇 |
原子能技术 | 1995篇 |
自动化技术 | 7401篇 |
出版年
2024年 | 596篇 |
2023年 | 2208篇 |
2022年 | 3571篇 |
2021年 | 3965篇 |
2020年 | 4136篇 |
2019年 | 3791篇 |
2018年 | 3264篇 |
2017年 | 3788篇 |
2016年 | 4199篇 |
2015年 | 4189篇 |
2014年 | 6753篇 |
2013年 | 6930篇 |
2012年 | 7196篇 |
2011年 | 8169篇 |
2010年 | 6206篇 |
2009年 | 6306篇 |
2008年 | 5800篇 |
2007年 | 6424篇 |
2006年 | 5341篇 |
2005年 | 4482篇 |
2004年 | 3672篇 |
2003年 | 3268篇 |
2002年 | 2818篇 |
2001年 | 2345篇 |
2000年 | 2036篇 |
1999年 | 1595篇 |
1998年 | 1379篇 |
1997年 | 1115篇 |
1996年 | 985篇 |
1995年 | 785篇 |
1994年 | 654篇 |
1993年 | 549篇 |
1992年 | 474篇 |
1991年 | 371篇 |
1990年 | 329篇 |
1989年 | 271篇 |
1988年 | 214篇 |
1987年 | 159篇 |
1986年 | 127篇 |
1985年 | 141篇 |
1984年 | 143篇 |
1983年 | 89篇 |
1982年 | 92篇 |
1981年 | 43篇 |
1980年 | 49篇 |
1979年 | 28篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1959年 | 20篇 |
1951年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
991.
分析广州石油化工总厂化肥厂1986~1996年的生产数据,得出能耗与合成氨和尿素装置的运转率及生产负荷率有显著或极显著的负相关性,建立了几种直线回归方程。分析表明负荷对能耗的影响远大于运转率的影响,能耗与装置停车的次数相关性不显著。 相似文献
992.
高效节能换热器在氮肥工业中的应用 总被引:1,自引:0,他引:1
描述了新型折流杆换热器的强化传热和降低壳层压力降的原理 ,它与传统折流板换热器相比 ,传热效率高 ,材料及能耗小。介绍了这种新型换热器在合成氨变换工段和尿素装置中的应用情况及所起的节能降耗作用 ,指出该高效节能换热器在设计和生产中的关键技术。 相似文献
993.
G.?BiresawEmail author A.?Adhvaryu S.?Z.?Erhan C.?J.?Carriere 《Journal of the American Oil Chemists' Society》2002,79(1):53-58
The steel/steel boundary friction properties of soybean oil (SBO) and high-oleic soybean oil (HOSBO) are compared. HOSBO is
significantly more saturated than SBO and more oxidatively stable. Changes in degree of unsaturation affect lateral interactions
of adsorbate molecules, which in turn affects their adsorption and, hence, their boundary lubrication properties. To investigate
this possibility, the free energies of adsorption (ΔG
ads) of SBO, HOSBO, and methyl laurate (ML) were determined from the analysis of friction-derived adsorption isotherms using
the Langmuir and Temkin adsorption models. The results showed a stronger adsorption for the vegetable oils than for ML, an
indication of multiple interactions between the ester groups of the triglycerides and the steel surface. The result also showed
no difference in the ΔG
ads values of SBO and HOSBO obtained using either the Langmuir or Temkin models. This was interpreted as an indication of the
lack of appreciable net lateral interaction between triglyceride adsorbates. 相似文献
994.
用接触角法测量聚合物共混体系的表面性能 总被引:11,自引:0,他引:11
利用接触角的方法研究了聚合物HDPF、PET及其共混物HDPE/PET的表面自由能、极化度以及与不同液体一水和甘油间界面张力的大小。 相似文献
995.
This paper shows the wide application range (such as electrical self‐heating and electromagnetic shielding effectiveness) of composites consisting of conductive carbon black/aluminum flakes (CBA) filler and epoxy insulative matrix. The effect of CBA content on the network structure of epoxy matrix was investigated in detail. Static electrical conductivity increases linearly with the increase of filler concentration at the interface in epoxy composites. The large decrease of the conductivity as a function of the temperature is analyzed in terms of the negative temperature coefficient of conductivity (NTCC) effect. The influence of viscosity, surface energy and barrier highest energy on the NTCC behaviour in the composite is also considered. Based on these results, a new interpretation is proposed to explain the NTCC phenomena by computing the swelling force among conductive phases. The correlations of conductivity during the temperature cycling and activation energy were analyzed. The effects of dynamic ageing at various temperatures on the resistivity are reported. Current–voltage–temperature characteristics for epoxy with different contents of CBA were examined in detail. A model based on the law of energy conservation is proposed to calculate the specific heat and amount of heat dissipation. The static charge of the epoxy–CBA composites was estimated. The correlation between electromagnetic wave‐shielding effectiveness (EMS), conductivity and frequency of epoxy composites with different filler contents is also discussed. Furthermore, the effect of annealing on EMS of epoxy composites was examined. © 2002 Society of Chemical Industry 相似文献
996.
997.
间歇窑窑墙温度场图形仿真研究 总被引:2,自引:0,他引:2
本文利用有限差分法求解间歇窑窑墙中的温度分布,并用C语言设计了窑墙温度场图形仿真软件。输入窑墙厚度和材料的物性参数等,系统可进行窑墙温度场分布的实时仿真及窑炉结构与操作的优化 相似文献
998.
Nonisothermal crystallization of poly(N‐methyldodecano‐12‐lactam) (MPA) was investigated using DSC method at cooling rates of 2–40 K/min. With increasing cooling rate, crystallization exotherms decreased in magnitude and shifted toward lower temperatures. Subsequent heating runs (10 K/min) showed an exotherm just above Tg, which increased in magnitude with the rate of preceding cooling run, corresponding to the continuation of primary crystallization interrupted as the system crossed Tg on cooling. Kinetic evaluation by the Avrami method gave values of exponent n close to 2.0, suggesting two‐dimensional crystal growth combined with heterogeneous nucleation. The Tobin method, covering the intermediate range of relative crystallinities, provided n ? 2.20, suggesting possible partial involvement of homogeneous nucleation at later stages of nonisothermal crystallization. The crystallization rate parameter k1/n showed a linear dependency on cooling rate for both methods, the Tobin values being slightly higher. The Ozawa approach failed to provide reasonable values of the kinetic exponent m of MPA. The Augis–Bennet method was used to determine the effective activation energy of the entire nonisothermal crystallization process of MPA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 564–572, 2005 相似文献
999.
1000.