全文获取类型
收费全文 | 18060篇 |
免费 | 1731篇 |
国内免费 | 992篇 |
专业分类
电工技术 | 654篇 |
综合类 | 1121篇 |
化学工业 | 5745篇 |
金属工艺 | 1328篇 |
机械仪表 | 787篇 |
建筑科学 | 613篇 |
矿业工程 | 471篇 |
能源动力 | 1071篇 |
轻工业 | 2237篇 |
水利工程 | 120篇 |
石油天然气 | 924篇 |
武器工业 | 568篇 |
无线电 | 968篇 |
一般工业技术 | 2317篇 |
冶金工业 | 980篇 |
原子能技术 | 217篇 |
自动化技术 | 662篇 |
出版年
2024年 | 88篇 |
2023年 | 388篇 |
2022年 | 477篇 |
2021年 | 642篇 |
2020年 | 638篇 |
2019年 | 622篇 |
2018年 | 567篇 |
2017年 | 686篇 |
2016年 | 708篇 |
2015年 | 622篇 |
2014年 | 943篇 |
2013年 | 1011篇 |
2012年 | 1119篇 |
2011年 | 1161篇 |
2010年 | 921篇 |
2009年 | 905篇 |
2008年 | 788篇 |
2007年 | 1065篇 |
2006年 | 1101篇 |
2005年 | 975篇 |
2004年 | 897篇 |
2003年 | 765篇 |
2002年 | 703篇 |
2001年 | 568篇 |
2000年 | 498篇 |
1999年 | 375篇 |
1998年 | 283篇 |
1997年 | 248篇 |
1996年 | 181篇 |
1995年 | 158篇 |
1994年 | 155篇 |
1993年 | 102篇 |
1992年 | 105篇 |
1991年 | 76篇 |
1990年 | 55篇 |
1989年 | 38篇 |
1988年 | 31篇 |
1987年 | 24篇 |
1986年 | 12篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 14篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
碳,氮对氧化锆相结构稳定性的作用 总被引:3,自引:0,他引:3
利用热处理研究了碳、氮对氧化锆相结构和相变的影响。实验结果表明:碳、氢原子在高温下可以渗入到氧化锆中去,阻止了氧化锆高温相(四方相和立方相)在冷却过程中向低温相(单斜相)的转变。 相似文献
122.
研究了三相鼓泡床中的临界固含率,以空气作气相,水、乙醇-水、丙酮-水、萜松醇-二甲苯作液相,石英砂、煤、雷奈镍作为固相。分析了鼓泡柱的高径比、气体速度、固体粒子的大小和比重、液体的粘度对临界固含率的影响,提出了含有这些参数的无因次数群的关联式,讨论了本文提出的关联式和文献报导的差别。 相似文献
123.
对现行设计规范中未提到的带中心管兼作法兰的管板的计算进行探讨,介绍了一种以弹性应力分析理论为依据,将管板管化为受均匀载荷的实心圆平板的计算方法。 相似文献
124.
气固下行流化床反应器Ⅱ气固两相的流动规律 总被引:1,自引:1,他引:1
气固下行流化床反应器气固两相流动过程是比较复杂的,沿轴向气固两相运动可分为第一加速、第二加速和恒速3个运动段,沿径向局部气体速度、颗粒速度和颗粒浓度都具有不同程度的不均匀性。而这种不均匀性是由气固两相顺重力场湍动运动所决定的。和循环床提升管相比,下行管反应器气固两相沿径向分布的不均匀性得到有效地改善,气固可以实现超短接触操作,因而是一种新型高效气固超短接触反应器 相似文献
125.
Daizo Kunii 《Chemical engineering science》1980,35(9):1887-1911
A general procedure is proposed for innovative research and development of gas-solid reactor systems, with a brief explanation of the significance of each step in the procedureBased upon the contacting mode between gas and solid phases, as well as the ways of supplying thermal energy to the reacting regions, various types of gas-solid reactor systems are classified by using tables of so called “matrix” form, for thermal cracking and gasification of heavy oils, gasification of coal, gasification of solid waste, calcination of limestone, clinkering of cement and reduction of iron ore.The importance of fundamental concepts is emphasized for successful research and development by presenting several examples; namely, calcination of limestone, thermal cracking of heavy oils and gasification of solid waste materials.In connection with the direction in which fundamental research should be oriented, four primary ways of thinking are proposed, which can be applied to obtain innovative ideas for further research and development in this field.One example of the author's practical experience was selected to show the role of the fundamental research in the course of large scale development. Finally the author outlines the role of chemical reaction engineering to innovate the novel gas-solid reactor systems which may be inevitable for simultaneous solution of the three big E's; namely, Energy, Environment and Economy. 相似文献
126.
Sabine Braipson-Danthine Claude Deroanne 《Journal of the American Oil Chemists' Society》2006,83(7):571-581
Several oils and fats often used for the industrial preparation of European shortenings were blended in binary systems. The
equilibrium (after 48 h at 15°C) solid fat contents (SFC; determined by pulsed NMR spectroscopy) were measured and plotted
against blend composition. SFC of the blends resulted from the SFC of each fat for the considered temperature as well as the
type of interaction existing between those fats (namely, ideal behavior, monotectic interaction, eutectic interaction, and
so on). The type of relationship fitted was dependent on the kind of interaction: Linear relationships were found for total
compatibility between fats, and polynomial-type (order 2) relationships were found for fats exhibiting incompatibility. Some
corresponding ternary oils and fats blends were also prepared and analyzed. Selected relationships (regression equations of
the fitted curves) obtained for binary blends were combined in order to calculate the SFC of the corresponding ternary blends.
Experimental values were generally close to predicted ones. The representation of SFC as a function of composition is interesting
as it allows one to determine rapidly and easily the type of molecular interaction between two fats and also to determine
equations that can be combined to calculate easily the SFC of corresponding ternary blends crystallized in the same way with
a good accuracy. The texture (hardness) of several binary and ternary blends was also measured. The combination of the results
obtained for SFC with the results obtained for the hardness of binary blends allows the prediction of the hardness of a corresponding
ternary blend under the same conditions. 相似文献
127.
用于测定钢液低氧含量的双层固体电解质研究 总被引:1,自引:0,他引:1
采用“毛坯浆料法”在ZrO2(9%摩尔含量MgO)管状固体电解质基体表面制备了厚度为1-4μm的ZrO2(10%摩尔含量Y2O3)固体电解质涂层,并分别对此在本实验室和美国LeedsandNorthrup公司进行了钢液低氧含量测试,结果表明:涂层没有破坏基体的抗热震性:氧浓差电池电动势的重现性偏差由原来的±2mV;电动势的绝对值提高10mV左右;而比日本Toray公司的同类产品提高35mV,这说明 相似文献
128.
129.
Matthias Berger Kurt Laumen Manfred P. Schneider 《Journal of the American Oil Chemists' Society》1992,69(10):955-960
Regioisomerically pure 1,3-sn-diacylglycerols are conveniently prepared in high yields (>80%) and in large quantities by enzymatic esterification of glycerol
in the presence of various 1,3-selective lipases(Chromobacterium viscosum, Rhizopus delemar, Rhizomucor miehei) and a variety of different acyl donors like free fatty acids, fatty acid alkyl esters and vinyl esters. All reactions are
carried out in aprotic organic solvents of low water content, namelyn-hexane, diethyl ether or tBuOMe. The creation of an artificial interphase between the solvent-immiscible hydrophilic glycerol
and the hydrophobic reaction media by the adsorption of glycerol onto a solid support prior to use was essential for the success
of these transformations. The effects of reaction conditions and the regioselectivities of the lipases on the product yields
are described in detail. 相似文献
130.
对超细及市售CaCO3在低含量(≤1%)的情况下对丁羟推进剂燃烧性能的影响进行了研究,结果发现CaCO3低含量时可提高推进剂的燃速且超细CaCO3比市售CaCO3的催化效率高。进一步研究了超细CaCO3与金属氧化物M2O3组合对推进剂燃烧的催化作用,结果表明两者有协同效应,其组合的燃烧催化效果较各自单独使用的催化效果要好。 相似文献