全文获取类型
收费全文 | 10092篇 |
免费 | 1335篇 |
国内免费 | 491篇 |
专业分类
电工技术 | 353篇 |
综合类 | 821篇 |
化学工业 | 2486篇 |
金属工艺 | 468篇 |
机械仪表 | 394篇 |
建筑科学 | 510篇 |
矿业工程 | 149篇 |
能源动力 | 323篇 |
轻工业 | 2011篇 |
水利工程 | 285篇 |
石油天然气 | 304篇 |
武器工业 | 82篇 |
无线电 | 816篇 |
一般工业技术 | 1568篇 |
冶金工业 | 429篇 |
原子能技术 | 115篇 |
自动化技术 | 804篇 |
出版年
2024年 | 44篇 |
2023年 | 123篇 |
2022年 | 195篇 |
2021年 | 286篇 |
2020年 | 349篇 |
2019年 | 415篇 |
2018年 | 373篇 |
2017年 | 448篇 |
2016年 | 419篇 |
2015年 | 447篇 |
2014年 | 534篇 |
2013年 | 665篇 |
2012年 | 657篇 |
2011年 | 689篇 |
2010年 | 522篇 |
2009年 | 523篇 |
2008年 | 456篇 |
2007年 | 603篇 |
2006年 | 586篇 |
2005年 | 458篇 |
2004年 | 357篇 |
2003年 | 355篇 |
2002年 | 388篇 |
2001年 | 350篇 |
2000年 | 270篇 |
1999年 | 260篇 |
1998年 | 179篇 |
1997年 | 152篇 |
1996年 | 147篇 |
1995年 | 106篇 |
1994年 | 118篇 |
1993年 | 73篇 |
1992年 | 68篇 |
1991年 | 53篇 |
1990年 | 48篇 |
1989年 | 39篇 |
1988年 | 36篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 15篇 |
1980年 | 3篇 |
1966年 | 5篇 |
1961年 | 4篇 |
1959年 | 3篇 |
1957年 | 2篇 |
1956年 | 2篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
11.
Seong‐Hee Kim 《Quality and Reliability Engineering International》2015,31(6):923-934
We present a distribution‐free tabular cumulative sum chart for monitoring the variability of an autocorrelated process. A quantity known as the asymptotic variance parameter is employed as a measure of the variability, and a distribution‐free tabular cumulative sum chart is applied to variance estimates calculated from batches of nonoverlapping samples. The proposed chart is applicable to a stationary process with a general marginal distribution and a general autocorrelation structure. It also determines control limits analytically without trial‐and‐error simulations. The performance of the proposed chart is tested on stationary processes with both normal and nonnormal marginals with various autocorrelation structures. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
12.
无皂型乳液聚合的研究进展 总被引:4,自引:0,他引:4
综述了无皂型乳液聚合反应机理及影响乳液稳定性的因素。对无皂型乳液聚合制备方法进行了论述,并介绍了无皂型乳液聚合的研究动态、应用和发展前景。 相似文献
13.
CHEN Yong-ping LI Chi-wai ZHANG Chang-kuang 《水动力学研究与进展(B辑)》2006,18(2):148-155
1. INTRODUCTION When wastewater is discharged into rivers, lakes or oceans, it usually leads to the formulation of turbulent jet with a free surface. If the ambient water depth is shallow, the jet will impinge on the water surface and the confinement of f… 相似文献
14.
碳黑对苯乙烯自由基聚合反应影响的研究 总被引:1,自引:0,他引:1
研究了碳黑对苯乙烯单体聚合物反应的影响,结果表明,用过氧化苯甲酰作引发剂,普通碳黑子对苯乙烯的聚合有强烈的阻聚作用,而用偶氮二异丁腈引发聚合物时,普通碳黑的阻聚性很小,当时碳黑进行接枝处理后,接枝碳黑对苯乙烯自由基聚合的影响程度与接枝方法有关,其中过氧化苯甲酰 自由基枝枝碳黑的聚性变化较大。 相似文献
15.
研制出了具有保护储层效果的无固相压井液,其基液配方为0.5%LG-1-1+0.4%LG-2+1%小阳离子+0.1%其它。此外还研究开发出了无机盐增溶剂LG-3,加入LG-3可加宽低成本无机盐的使用范围,很大程度地降低压井液配液成本和单井综合成本。该压井液密度在1.0-2.5g/cm^3之间可调,具有无固相、滤失量低、抑制性强等特点,抗温能力在120℃左右。室内性能评价结果表明,无固相压井液对高渗储层岩心的渗透率损害率平均为4.0%,对低渗储层岩心的渗透率损害率平均为2.9%,说明该体系对储层具有很好的保护效果。 相似文献
16.
17.
Gibbs energies of formation of CoF2 and MnF2 have been measured in the temperature range from 700 to 1100 K using Al2O3-dispersed CaF2 solid electrolyte and Ni+NiF2 as the reference electrode. The dispersed solid electrolyte has higher conductivity than pure CaF2 thus permitting accurate measurements at lower temperatures. However, to prevent reaction between Al2O3 in the solid electrolyte and NiF2 (or CoF2) at the electrode, the dispersed solid electrolyte was coated with pure CaF2, thus creating a composite structure. The free energies of formation of CoF2 and MnF2 are (± 1700) J mol−1; {fx37-1} The third law analysis gives the enthalpy of formation of solid CoF2 as ΔH° (298·15 K) = −672·69 (± 0·1) kJ mol−1, which compares with a value of −671·5 (± 4) kJ mol−1 given in Janaf tables. For solid MnF2, ΔH°(298·15 K) = − 854·97 (± 0·13) kJ mol−1, which is significantly different from a value of −803·3 kJ mol−1 given in the compilation by Barinet al. 相似文献
18.
Yu‐Qing Cao Zhan Zhang Yan‐Xin Guo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(10):1441-1444
A new efficient method for synthesising nitriles, important organic reagents, is reported in this paper. In an environmentally benign solvent‐free system, aryl carboxylic acids were converted into the corresponding nitriles via one‐pot reactions, by amidation with ethyl carbamate followed by dehydration with thionyl chloride, in excellent yields. The results showed that the method has the advantages of lower cost, higher yield, less pollution and greater ease of work‐up. Copyright © 2008 Society of Chemical Industry 相似文献
19.
The miscibility and phase behavior of ternary blends containing dimethylpolycarbonate (DMPC), tetramethylpolycarbonate (TMPC) and poly[styrene‐co‐(methyl methacrylate)] copolymer (SMMA) have been explored. Ternary blends containing polystyrene (PS) instead of SMMA were also examined. Blends of DMPC with SMMA copolymers (or PS) did not form miscible blends regardless of methyl methacrylate (MMA) content in copolymers. However, DMPC blends with SMMA (or PS) blends become miscible by adding TMPC. The miscible region of ternary blends is compared with the previously determined miscibility region of binary blends having the same chemical components and compositions. The region where the ternary blends are miscible is much narrower than that of binary blends. Based on lattice fluid theory, the observed phase behavior of ternary blends was analyzed. Even though the term representing the Gibbs free energy change of mixing for certain ternary blends had a negative value, blends were immiscible. It was revealed that a negative value of the Gibbs free energy change of mixing was not a sufficient condition for miscible ternary blends because of the asymmetry in the binary interactions involved in ternary blends. Copyright © 2004 Society of Chemical Industry 相似文献
20.
Renjith Devasia CP Reghunadhan Nair P Sivadasan KN Ninan 《Polymer International》2005,54(8):1110-1118
Polyacrylonitrile terpolymers of various compositions consisting of acrylonitrile (AN), itaconic acid (IA) and methyl acrylate (MA) were synthesized by solution polymerization in dimethylsulfoxide. Increase in concentration of either IA or MA retarded the overall polymerization rate and the polymer molecular weight. The system consisting of AN + MA and varying IA concentration was more prone to retardation in comparison with the system composed of AN + IA with variable MA concentration. The retardation factors were quantified. Minor quantities of MA boost the reactivity of IA in the terpolymer system. The terpolymer was richer in MA vis‐à‐vis the feed. The thermal characteristics of the terpolymer were examined as a function of its composition. In contrast to the copolymer of AN and IA requiring 1–1.5 mol% IA, the terpolymer required an IA content of approximately 2.5 mol% for optimum thermal stability. The polymer with 90 mol% AN, 2.5 mol% IA and 7.5 mol% MA exhibited reasonably good char‐forming characteristics and thermal stability. The overall crystallinity and crystallite size of the polymers were found to decrease on incorporation of the comonomers. The ‘aromatization index’ of the copolymer increased with the temperature of pyrolysis through re‐organization of the tetrahydropyridine ladder structure. Copyright © 2005 Society of Chemical Industry 相似文献