全文获取类型
收费全文 | 30711篇 |
免费 | 3253篇 |
国内免费 | 1458篇 |
专业分类
电工技术 | 424篇 |
综合类 | 1595篇 |
化学工业 | 11548篇 |
金属工艺 | 1276篇 |
机械仪表 | 1456篇 |
建筑科学 | 653篇 |
矿业工程 | 461篇 |
能源动力 | 934篇 |
轻工业 | 6328篇 |
水利工程 | 173篇 |
石油天然气 | 1794篇 |
武器工业 | 220篇 |
无线电 | 2213篇 |
一般工业技术 | 3862篇 |
冶金工业 | 1026篇 |
原子能技术 | 640篇 |
自动化技术 | 819篇 |
出版年
2024年 | 156篇 |
2023年 | 603篇 |
2022年 | 770篇 |
2021年 | 1201篇 |
2020年 | 1222篇 |
2019年 | 1253篇 |
2018年 | 1153篇 |
2017年 | 1250篇 |
2016年 | 1368篇 |
2015年 | 1255篇 |
2014年 | 1782篇 |
2013年 | 2155篇 |
2012年 | 2150篇 |
2011年 | 2102篇 |
2010年 | 1459篇 |
2009年 | 1520篇 |
2008年 | 1289篇 |
2007年 | 1718篇 |
2006年 | 1554篇 |
2005年 | 1347篇 |
2004年 | 1136篇 |
2003年 | 1017篇 |
2002年 | 893篇 |
2001年 | 797篇 |
2000年 | 718篇 |
1999年 | 613篇 |
1998年 | 521篇 |
1997年 | 467篇 |
1996年 | 343篇 |
1995年 | 313篇 |
1994年 | 225篇 |
1993年 | 226篇 |
1992年 | 184篇 |
1991年 | 110篇 |
1990年 | 90篇 |
1989年 | 72篇 |
1988年 | 63篇 |
1987年 | 43篇 |
1986年 | 32篇 |
1985年 | 58篇 |
1984年 | 51篇 |
1983年 | 33篇 |
1982年 | 29篇 |
1981年 | 21篇 |
1980年 | 21篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Gas/liquid mass transfer has been investigated using a stirred vessel gas/liquid contactor using non‐Newtonian media and carbon dioxide as absorbent and gas phase, respectively. The volumetric mass transfer coefficients at different operational variables have been determined. Non‐Newtonian media (liquid phase) were prepared as aqueous solutions of sodium carboxymethyl cellulose salt. The influence of the rheological properties, polymer concentration, stirring rate, and gas flow rate on mass transfer was studied for these liquid phases. Kinematic viscosity and density experimental data were used to calculate the average molecular weight corresponding to the polymer employed. The Ostwald model has been used to fit the rheological behavior of aqueous solutions of the polymer employed as absorbent phase. Reasonably good agreement was found between the predictions of the proposed models and the experimental data of mass transfer coefficients. 相似文献
32.
Su Yu liangDepartment of Energy power Engineering Xi'an Jiaotong University Xi'an ChinaDepartment of petroleum Engineering Petroleum University Dongying ChinaZhang Ming yuan Yang Jian Zhang Chao jieDepartment of Energy power Engineering Xi'an Jiaotong University Xi'an ChinaLi Dong xia Department of petroleum Engineering Petroleum University Dongying China 《水动力学研究与进展(B辑)》2003,15(2)
NOMENCLATUREd———embeddingdimension ,dimensionlessCd(r)———correlationsum ,dimensionlessN———numberofpairsofpointsontherecon structedattractor,dimensionlessr———scalingdistance ,dimensionlessDc ———correlationdimension ,dimensionlessK———Kolmogoroventropy ,bits/sR… 相似文献
33.
This review article is devoted to the materials containing niobium, which have been discovered or developed in the past few years and exhibit the potential application in heterogeneous catalysis. Niobium oxides and mixed oxides as well as sulfides, nitrides (oxynitrides), carbides (oxycarbides), and phosphates are considered. Among the catalytic processes in which Nb-containing materials were tested, liquid and gas phase oxidation is described in details, and the role of niobium in the prevention of the catalyst from SO2 poisoning is mentioned. 相似文献
34.
磷酸酯类离子液体在燃油深度脱硫中的应用 总被引:16,自引:6,他引:10
研究了3种磷酸酯类离子液体,即1,3-二甲基咪唑磷酸二甲酯盐([MM im]DM P)、1-乙基-3-甲基咪唑磷酸二乙酯盐([EM im]DEP)和1-丁基-3-甲基咪唑磷酸二丁酯盐([BM im]DBP)的制备过程,考察了这3种磷酸酯类离子液体对模型油中3-甲基噻吩、苯并噻吩和二苯并噻吩的脱除效果及磷酸酯类离子液体的电化学再生方法。实验结果表明,这3种磷酸酯类离子液体的脱硫能力强弱顺序为:[EM im]DEP>[BM im]DBP[MM im]DM P;且对二苯并噻吩的脱除效果最好,对苯并噻吩的脱除效果次之,对3-甲基噻吩的脱除效果较差。以[EM im]DEP为萃取剂,油剂质量比为1∶1时,经5次萃取后,二苯并噻吩的脱除率可达到99.5%。利用电解法对[EM im]DEP进行了再生,在5~10V电压下电解10h,[EM im]DEP的脱硫率可以达到新鲜[EM im]DEP的90%以上。 相似文献
35.
36.
I. Budić-Leto T. Lovrić J. Gajdoš Kljusurić I. Pezo U. Vrhovšek 《European Food Research and Technology》2006,222(3-4):397-402
Identification of anthocyanins in the wine made of the Croatian autochthonous grape variety of Babić (Vitis vinifera L.) was carried out and their profile was determined by means of high-performance liquid chromatography with diode array
and mass spectrometric detection. Dependence of anthocyanins content and profile on maceration treatment conditions was investigated.
Statistically significant differences of anthocyanins concentration in wines Babić produced by various maceration treatments
were confirmed by the use of multivariate analysis of variances. The investigation results indicated that the maceration temperature
exerts higher influence on anthocyanins concentration than the duration of maceration. In addition, on the basis of anthocyanin
composition and using different multivariate statistical analyses, differentiation of wines Babić according to maceration
treatments was procured. 相似文献
37.
38.
Thermodynamic and Transport Properties of Liquid HFC-227ea 总被引:1,自引:0,他引:1
The thermal conductivity and heat capacity of liquid 1,1,1,2,3,3,3-hepta-fluoropropane (HFC-227ea) have been studied by a high-frequency thermal-wave method over the temperature range of 294 to 345 K at pressures up to 2.8 MPa. The purity of the samples used throughout the measurements is 99.99 mol%. The experimental uncertainties of the thermal conductivity and heat capacity measurements were estimated to be within ±1.5 and ±2%, respectively. The thermal conductivity of HFC-227ea in the liquid phase decreases as temperature increases, while the pressure has an opposite effect. 相似文献
39.
Dynamics of liquid-filled spacecraft 总被引:1,自引:0,他引:1
A method is presented for simulating coupled liquid-solid dynamics. An important example of a coupled liquid-solid system is a satellite carrying fuel. The dynamics of the satellite and the onboard fuel influence each other, which may lead to satellite motion that is uncontrollable. For better understanding of the complex dynamics of coupled systems, a numerical model is developed. The model consists of two parts. The first part that solves the liquid motion is only briefly discussed here. The focus in this paper is on the way in which the dynamics of the liquid and the solid body are coupled. For this, the governing equations are presented in which terms appear that represent the force and torque on the solid body due to the sloshing liquid. The governing equations are rewritten such that the discrete approximation of these equations can be integrated in a stable manner for arbitrary liquid/solid mass ratios. Results are presented demonstrating the stability of the present model. A grid-refinement study and a time-step analysis are performed. Finally, the flat-spin motion of a satellite, partially filled with liquid, that flew in 1992 as part of the Wet Satellite Model experiment is studied. Results from the simulation are compared with the actual flight data. 相似文献
40.
A series of novel thermoplastic elastomers, based on poly(dimethylsiloxane) (PDMS) as the soft segment and poly(butylene terephthalate) (PBT) as the hard segment, were synthesized by catalyzed two‐step, melt transesterification reactions of dimethyl terephthalate and methyl esters of carboxypropyl‐terminated poly(dimethylsiloxane)s (M?n = 550–2170 g mol?1) with 1,4‐butanediol. The lengths of both the hard and soft segments were varied while the weight ratio of the hard to soft segments in the reaction mixture was maintained constant (57/43). The molecular structure, composition and molecular weights of the poly(ester–siloxane)s were examined by 1H NMR spectroscopy. The effectiveness of the incorporation of the methyl‐ester‐terminated poly(dimethylsiloxane)s into the copolymer chains was verified by chloroform extraction. The effect of the segment length on the transition temperatures (Tm and Tg) and the thermal and thermo‐oxidative degradation stability, as well as the degree of crystallinity and hardness properties of the synthesized TPESs, were studied. Copyright © 2003 Society of Chemical Industry 相似文献