全文获取类型
收费全文 | 25660篇 |
免费 | 3050篇 |
国内免费 | 1827篇 |
专业分类
电工技术 | 1807篇 |
综合类 | 3126篇 |
化学工业 | 3678篇 |
金属工艺 | 1400篇 |
机械仪表 | 1952篇 |
建筑科学 | 3877篇 |
矿业工程 | 1047篇 |
能源动力 | 1422篇 |
轻工业 | 825篇 |
水利工程 | 1639篇 |
石油天然气 | 1175篇 |
武器工业 | 314篇 |
无线电 | 2169篇 |
一般工业技术 | 2784篇 |
冶金工业 | 823篇 |
原子能技术 | 614篇 |
自动化技术 | 1885篇 |
出版年
2024年 | 110篇 |
2023年 | 338篇 |
2022年 | 683篇 |
2021年 | 753篇 |
2020年 | 899篇 |
2019年 | 749篇 |
2018年 | 730篇 |
2017年 | 1003篇 |
2016年 | 985篇 |
2015年 | 1068篇 |
2014年 | 1435篇 |
2013年 | 1715篇 |
2012年 | 1911篇 |
2011年 | 1952篇 |
2010年 | 1479篇 |
2009年 | 1533篇 |
2008年 | 1491篇 |
2007年 | 1746篇 |
2006年 | 1518篇 |
2005年 | 1279篇 |
2004年 | 1072篇 |
2003年 | 891篇 |
2002年 | 778篇 |
2001年 | 662篇 |
2000年 | 596篇 |
1999年 | 488篇 |
1998年 | 407篇 |
1997年 | 384篇 |
1996年 | 333篇 |
1995年 | 292篇 |
1994年 | 256篇 |
1993年 | 174篇 |
1992年 | 162篇 |
1991年 | 141篇 |
1990年 | 140篇 |
1989年 | 101篇 |
1988年 | 78篇 |
1987年 | 49篇 |
1986年 | 39篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 6篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 14篇 |
1979年 | 3篇 |
1973年 | 2篇 |
1965年 | 2篇 |
1959年 | 3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.
122.
DCS在采暖锅炉房中的应用 总被引:2,自引:1,他引:1
介绍了Jx—300X DCS系统的组成、功能、特点以及热水锅炉主要控制方案及其在锅炉测控方面的应用。 相似文献
123.
E. Gomez 《Chemical engineering science》2006,61(14):4595-4604
The influence of oxygen transport rate on Rhodococcus erythropolis cultures has been studied in a stirred tank bioreactor under different transport and uptake conditions. Oxygen uptake rate has been measured by applying a modified dynamic method and a kinetic model is proposed, obtaining the kinetic parameter values: specific maintenance and yield coefficients. The volumetric mass transfer coefficients under inert conditions, kLa, and during the bioprocess, KLa, have been determined. The values obtained are different and a biological enhancement factor E, has been considered. These parameters have been predicted by the theoretical model and good agreement with experimental data under the conditions studied has been found. The oxygen limitation has been expressed by a modified dimensionless Damköhler number, Da, the relationship between transport and biological reaction rates. This number decreases with increasing stirrer speed; that is, when mass transport resistance decreases. The efficiency of oxygen utilization can be determined by a film effectiveness factor, η. The effectiveness factor was found to be a strong function of Damköhler number and decrease with increasing Da. Furthermore, oxygen concentration into culture depends on the mass transfer and consumption rates. The theoretical model proposed is able to reasonably predict the evolution of dissolved oxygen concentration with time of cultivation. 相似文献
124.
二硫代磷酸硫化氧钼与硫,磷添加剂的复配特性研究 总被引:1,自引:0,他引:1
研究了二烷基二硫代磷酸硫化氧钼(MoDTP)摩擦改进剂及其与硫、磷、硫-磷型添加剂复合的抗磨减摩性能。试验表明,经过适当复配后,这类合活性元素的添加剂对MoDTP的抗磨减摩性能均有增效作用,同一类型添加剂的活性愈高,增效作用愈显著。同时利用扫描电镜和X-射线能谱仪进行摩擦副表面膜的形貌照相及元素分析,对复合作用的机理进行了初步探讨。 相似文献
125.
Qin Datong Sun DongyeState Key Laboratory ofMechanical Transmission Chongqing University Chongqing China 《机械工程学报(英文版)》2003,16(4):391-395
The rmomechnical phenomena occurring between friction pairs greatly change the distributions oflining pressure and friction surface temperature of a multiple disc wet brake. It has become one of the maincauses of brake failure. In order to understand these thermomechanical phenomena, several design and mate-rial factors tha have great influence on thermomechanical phenomena, such as heat transfer coefficient, fric-tion factor, sliding velocity initial lining pressure and so on, are analyzed. An isothermal design method isproposed for designing a multiple disc wet brake. 相似文献
126.
克拉2气田储层岩石的应力敏感性及其对生产动态的影响 总被引:9,自引:2,他引:7
克拉2气田是一个异常高压气藏,压力系数在2.0以上。在衰竭式开采条件下,其地层压力降幅可为普通气藏地层压力降幅的3倍以上,因此研究储层岩石应力敏感性及其对生产动态的影响意义重大。研究得出,岩石的应力敏感性特征主要有:岩石物性对应力的敏感性总体上不大,其中以孔隙度最小,渗透率次之,压缩系数最大;岩石物性随地层压力的下降而下降;在同一地层压降下.岩石物性下降幅度不是渗透率的连续函数,而是与渗透率分布范围有关,高渗透率范围,岩石物性下降幅度小,低渗透率范围,岩石物性下降幅度大。研究得出,克拉2气田岩石的应力敏感性对其生产动态的影响较小。 相似文献
127.
Thermal Radiative Properties of Xonotlite Insulation Material 总被引:1,自引:0,他引:1
X inxin ZHANG Gaosheng WEI Fan YU Department of Thermal Engineering University of Science & Technology Beijing Beijing China Professor 《热科学学报(英文版)》2005,14(3):281-283,253
Introduction Xonotlite-type calcium silicate (6CaO?6SiO2?H2O) is synthesized porous insulation material by hydrothermal processing with quartz powder and limestone as the raw material (with CaO/ SiO2≈1:1). Compared with fire- retardant fibre, xonotlite has more excellent insulating performance, such as low thermal conductivity, environment friendly, high intension, and wide applying temperature range, which has been emphasized in recent years by many scholars and widely used in many indu… 相似文献
128.
Abstract. A pth‐order random coefficient integer‐valued autoregressive [RCINAR(p)] model is proposed for count data. Stationarity and ergodicity properties are established. Maximum likelihood, conditional least squares, modified quasi‐likelihood and generalized method of moments are used to estimate the model parameters. Asymptotic properties of the estimators are derived. Simulation results on the comparison of the estimators are reported. The models are applied to two real data sets. 相似文献
129.
Solubility of dimethyl-2,6-naphthalene dicarboxylate in acetic acid, N,N-dimethylfonnamide, N,N-dimethyl acetamide, dimethyl sulphoxide, and N-methyl-2-ketopyrrolidine were determined using a dynamic method. The measured systems were correlated by UNIFAC group contribution method. A new main group (aromatic ester, ACCOO) was defined to express the activity coefficients of the aromatic ester. New interaction parameters of the ACCOO group were expressed as the first-order function of temperature and were determined from the experimental data. The calculated results for the new interaction parameters were satisfactory. The measured systems were also correlated with the Wilson and 2-h models, and the results were compared with those of the UNIFAC model. 相似文献
130.
The electrochemical behavior of ferrocene (Fc) and ferricenium (Fc+) was investigated by cyclic voltammetry with convolutional and semi-differential electroanalyses in the temperature range 298-373 K in the hydrophobic room temperature ionic liquid systems consisting of bis(trifluoromethanesulfone)imide anion with quaternary ammonium cation. The experimental results indicated that the redox reaction of Fc/Fc+ was reversible in this ionic liquid and the charge-transfer rate constant (k0) has been obtained. Mass transport towards the electrode is a simple diffusion process and the diffusion coefficient (D) for Fc/Fc+ has been also calculated. These results indicated that the k0 and D increased with increasing temperature in ionic liquids. The validity of the Arrhenius law was verified by investigating the temperature dependences of k0 and D. 相似文献