全文获取类型
收费全文 | 2514篇 |
免费 | 196篇 |
国内免费 | 77篇 |
专业分类
电工技术 | 32篇 |
综合类 | 152篇 |
化学工业 | 778篇 |
金属工艺 | 69篇 |
机械仪表 | 385篇 |
建筑科学 | 47篇 |
矿业工程 | 39篇 |
能源动力 | 134篇 |
轻工业 | 55篇 |
水利工程 | 15篇 |
石油天然气 | 391篇 |
武器工业 | 21篇 |
无线电 | 33篇 |
一般工业技术 | 531篇 |
冶金工业 | 23篇 |
原子能技术 | 17篇 |
自动化技术 | 65篇 |
出版年
2024年 | 9篇 |
2023年 | 38篇 |
2022年 | 49篇 |
2021年 | 67篇 |
2020年 | 54篇 |
2019年 | 59篇 |
2018年 | 81篇 |
2017年 | 52篇 |
2016年 | 61篇 |
2015年 | 85篇 |
2014年 | 111篇 |
2013年 | 158篇 |
2012年 | 122篇 |
2011年 | 162篇 |
2010年 | 114篇 |
2009年 | 125篇 |
2008年 | 110篇 |
2007年 | 181篇 |
2006年 | 189篇 |
2005年 | 148篇 |
2004年 | 143篇 |
2003年 | 104篇 |
2002年 | 84篇 |
2001年 | 88篇 |
2000年 | 45篇 |
1999年 | 53篇 |
1998年 | 55篇 |
1997年 | 40篇 |
1996年 | 32篇 |
1995年 | 26篇 |
1994年 | 21篇 |
1993年 | 20篇 |
1992年 | 18篇 |
1991年 | 14篇 |
1990年 | 11篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有2787条查询结果,搜索用时 15 毫秒
281.
一种新型电流变体材料——酮醛树脂盐类电流变体 总被引:1,自引:0,他引:1
决定电流变体材料性能的主要因素是其分散相的选择。文中首次提出了以酮醛树脂盐类作为电流变体的分散相,研究了反应温度、反应时间及催化剂用量等各种因素对其分子量的影响,测试了以酮醛树脂盐与硅油组成的电流变体材料的稳定特性、温度特性、流变特性、介电特性,结果表明该流体具有良好的抗高剪切速率的特性。 相似文献
282.
粘弹性胶束压裂液的形成与流变性质 总被引:14,自引:3,他引:11
由C16、C18烷基三甲基季铵盐和助剂配制了压裂用表面活性剂VES 60。考察了VES 60/水及其他体系形成胶束凝胶的能力。得到了一种蠕虫状胶束和一种片状胶束的环境扫描电镜照片。测定了体积分数(下同)为5%的CTAC与NaSal、NaSal+KNO3水溶液形成的胶束凝胶的粘度(70℃)随剪切速率的变化,讨论了两种盐之间的协同作用。在不同温度(10~40℃)和10s-1下,4%VES 60水溶液形成胶束的动力学包括三个阶段:链分散,低粘度;链缔合,粘度快速增大;链动态平衡,粘度基本稳定。在170s-1下4%VES 60的胶束溶液的粘度随温度升高而下降,在50~80℃区间下降幅度很小,粘度约在60mPa·s上下,在80℃以上急剧降低。20℃时4%VES 60胶束溶液的流变性符合H B模型,k′=8.664Pa·sn′,n′=0.2678,τy=5.4Pa。随表面活性剂体积分数增大(2.0%~5.0%),30℃时VES 60胶束溶液的粘弹性参数G′,G″和η 增大,tanδ减小,即弹性增强而粘性相对减弱。图5表2参6。 相似文献
283.
Mixing rules for an extended Lee-Kesler (ELK) corresponding-states method for prediction of thermodynamic properties are presented. The mixing rules, which do not contain adjustable parameters, permit calculation of vapor-liquid equilibria in mixtures containing one or more polar components. While a single heat-of-mixing datum may be included for strongly associating components, generally only pure component properties are used in the calculations. A comparison of calculated bubble-point pressures and equilibrium vaporization ratios to experimental values is made for 26 ternary mixtures (791 points) and 5 quaternary mixtures (175 points). Bubble-point pressures are predicted quite well with ELK (9.1 % AAD for ternaries and 7.9% for quaternaries). Composition predictions are difficult to compare in multicomponent systems, but ELK predictions appear to be acceptable on both a system-by-system and an overall AAD basis.Paper presented at the Tenth Symposium on Thermophysical properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A. 相似文献
284.
A. A. Vasserman S. V. Bodyul E. S. Bodyul 《International Journal of Thermophysics》2004,25(2):371-377
An automated system for calculating thermophysical properties of gases and liquids over a wide range of parameters has been developed. On the basis of values of the properties, the processes of isothermal compression, adiabatic throttling, polytropic expansion, heat exchange in two- and multi-stream heat exchangers, separation of vapor-liquid mixtures in the liquid vessel, and rectification in an air separation plant can be analyzed. For a specified structure scheme of a cryogenic plant, optimization of a corresponding thermodynamic cycle can be fulfilled. 相似文献
285.
苏里格气田储层具有多层、薄层的特点,分压改造是有效开发气田的主体技术之一。针对分层压裂使用的压裂液进行了室内优化及测试研究,在优选压裂液添加剂基础上,优选出了分层压裂使用的压裂液配方,并针对分压中出现的高剪切及压裂液滞留等问题,开展了试验研究。该压裂液配方能较好地降低储层喉道毛细管的界面张力,有利于压裂后残液的返排。优化的压裂液配方能降低对储层造成的伤害,其性能指标满足了储层及分压工艺的要求。 相似文献
286.
New functional forms have been developed for multiparameter equations of state for non- and weakly polar fluids and for polar fluids. The resulting functional forms, which were established with an optimization algorithm which considers data sets for different fluids simultaneously, are suitable as a basis for equations of state for a broad variety of fluids. The functional forms were designed to fulfill typical demands of advanced technical applications with regard to the achieved accuracy. They are numerically very stable and their substance-specific coefficients can easily be fitted to restricted data sets. In this way, a fast extension of the group of fluids for which accurate empirical equations of state are available becomes possible. This article deals with the results found for the non- and weakly polar fluids methane, ethane, propane, isobutane, n-butane, n-pentane, n-hexane, n-heptane, n-octane, argon, oxygen, nitrogen, ethylene, cyclohexane, and sulfur hexafluoride. The substance-specific parameters of the new equations of state are given as well as statistical and graphical comparisons with experimental data. General features of the new class of equations of state such as their extrapolation behavior and their numerical stability have been discussed in a preceding article. Results for typical polar fluids will be discussed in a subsequent article. 相似文献
287.
288.
In previous work, several significant improvements in the measurement of distillation curves for complex fluids were introduced. The modifications to the classical measurement provide for (1) temperature and volume measurement(s) of low uncertainty, and most important, (2) a composition-explicit data channel in addition to the usual temperature–volume relationship. This latter modification is achieved with a new sampling approach that allows precise qualitative as well as quantitative analyses of each fraction, on the fly. In the new approach, the distillation temperature is measured in two locations. The temperature is measured in the usual location, at the bottom of the take-off in the distillation head, but it is also measured directly in the fluid. We have further modified our developmental instrument to incorporate a model predictive temperature controller. In response to either an equation-of-state calculation or a previous distillation curve, the programmable temperature controller increases the fluid temperature to achieve a constant mass flow rate of vapor through the distillation head. This approach eliminates the aberrations that one typically encounters in the data due to fluctuations in distillation rate, often referred to as hesitation. Thus, we can collect data from two temperature channels: one a true state point measurement (measured directly in the fluid) and the other comparable to previous data (measured in the head). 相似文献
289.
George W. Mushrush Heather D. Willauer Jean L. Bailey John B. Hoover Frederick W. Williams 《Petroleum Science and Technology》2006,24(12):1441-1446
Hydraulic fluids for the most part are considered to be much less flammable than middle distillate fuels. Petroleum-based hydraulic fluids have high flash points, while water-based hydraulic fluids (because of their high water content) are definitely nonflammable. The major problem with water-based hydraulic fluids is corrosion. Petroleum-based fluids are much less corrosive and thus equipment lifetime is considerably increased. However, some petroleum-based hydraulic fluids have been observed to be a fire safety hazard in situations where high-pressure leaks can result in aerosol formation. These fire hazards cannot be adequately explained based solely on flash point considerations of the hydraulic fluids alone. 相似文献
290.
AM/AA/DMDAAC三元共聚物的合成及性能 总被引:1,自引:1,他引:0
采用氧化-还原引发体系合成了丙烯酰胺(AM)/丙烯酸(AA)/二甲基二烯丙基氯化铵(DMDAAC)三元共聚物,并对此三元共聚物的泥浆性能进行了初步评价。结果表明,AM/AA/DMDAAC三元共聚物具有较强的降滤失、抑制页岩水化膨胀能力。 相似文献