全文获取类型
收费全文 | 491732篇 |
免费 | 36906篇 |
国内免费 | 19612篇 |
专业分类
电工技术 | 27496篇 |
技术理论 | 41篇 |
综合类 | 29708篇 |
化学工业 | 81624篇 |
金属工艺 | 28827篇 |
机械仪表 | 30855篇 |
建筑科学 | 35962篇 |
矿业工程 | 14681篇 |
能源动力 | 12564篇 |
轻工业 | 29797篇 |
水利工程 | 8960篇 |
石油天然气 | 31062篇 |
武器工业 | 3865篇 |
无线电 | 52837篇 |
一般工业技术 | 63760篇 |
冶金工业 | 27477篇 |
原子能技术 | 8208篇 |
自动化技术 | 60526篇 |
出版年
2024年 | 2135篇 |
2023年 | 7423篇 |
2022年 | 13943篇 |
2021年 | 19538篇 |
2020年 | 14504篇 |
2019年 | 12050篇 |
2018年 | 14196篇 |
2017年 | 15923篇 |
2016年 | 14126篇 |
2015年 | 18468篇 |
2014年 | 23148篇 |
2013年 | 27667篇 |
2012年 | 29856篇 |
2011年 | 32501篇 |
2010年 | 28119篇 |
2009年 | 26928篇 |
2008年 | 26346篇 |
2007年 | 25152篇 |
2006年 | 25240篇 |
2005年 | 22004篇 |
2004年 | 14978篇 |
2003年 | 13634篇 |
2002年 | 13114篇 |
2001年 | 11783篇 |
2000年 | 11523篇 |
1999年 | 12323篇 |
1998年 | 9812篇 |
1997年 | 8389篇 |
1996年 | 7716篇 |
1995年 | 6500篇 |
1994年 | 5396篇 |
1993年 | 4032篇 |
1992年 | 3494篇 |
1991年 | 2772篇 |
1990年 | 2336篇 |
1989年 | 2024篇 |
1988年 | 1710篇 |
1987年 | 1393篇 |
1986年 | 1172篇 |
1985年 | 1007篇 |
1984年 | 897篇 |
1983年 | 785篇 |
1982年 | 810篇 |
1981年 | 761篇 |
1980年 | 723篇 |
1979年 | 770篇 |
1978年 | 785篇 |
1977年 | 746篇 |
1976年 | 758篇 |
1973年 | 725篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
A model of contact thermolysis was constructed based on a combined set of equations for heat transfer from a magmatic intrusion to a coal bed and the kinetics of thermal coal conversion. This model was illustrated by the generation of petroleum hydrocarbons deep in the earth by the thermolysis of the sapropelic matter of boghead. 相似文献
82.
V. M. Vorotyntsev G. M. Mochalov M. A. Kolotilova S. S. Suvorov A. V. Koroleva A. Yu. Sharov 《Theoretical Foundations of Chemical Engineering》2008,42(2):197-202
The results of theoretical and experimental studies for the kinetics of separating dichlorosilane from a mixture of volatile chlorosilanes and ultrapurifying the dichlorosilane concentrate by batch distillation are reported. A mathematical model of the process is proposed. It is shown that the model and computational algorithm adequately describe both processes. The obtained experimental and theoretical data made it possible to design a concentration and ultrapurification process with a maximal productivity at a specified product purity. 相似文献
83.
Yu. V. Pokonova 《Solid Fuel Chemistry》2008,42(6):369-372
Impregnants prepared from shale phenols for cellular materials had a cohesive strength of 2.4–18.5 J/m2 and a specific elongation of 160–170%. The adhesive strength toward a metal was 3.5–6.0 J/m2; in the case of concrete, it was greater than the concrete strength. 相似文献
84.
I. I. Nemets Yu. N. Trepalina E. A. Doroganov 《Refractories and Industrial Ceramics》2008,49(3):205-208
Physicotechnical properties are provided for concretes based on mechanically-activated phosphate suspensions previously modified
with magnesium and aluminum hydroxides and silicic acid. The results obtained demonstrate the efficiency of using modifying
additions in order to increase the strength and heat resistance of corundum concretes.
Translated from Novye Ogneupory, No. 5, pp. 32–35, May 2008. 相似文献
85.
对八钢彩涂机组生产中单环氧背面漆的应用进行了分析,介绍了实际生产中使用单环氧背面漆存在的问题,并制定出相应解决措施及方案,确保彩涂单环氧背面漆的表面质量及机械性能的要求. 相似文献
86.
Local residence time,residence revolution,and residence volume distributions in twin‐screw extruders
Xian‐Ming Zhang Lian‐Fang Feng Sandrine Hoppe Guo‐Hua Hu 《Polymer Engineering and Science》2008,48(1):19-28
This work was aimed at studying the overall, partial, and local residence time distributions (RTD); overall, partial and local residence revolution distributions (RRD) and overall, partial and local residence volume distributions (RVD) in a co‐rotating twin screw extruder, on the one hand; and establishing the relationships among them, on the other hand. Emphasis was placed on the effects of the type and geometry of mixing elements (a gear block and various types of kneading elements differing in staggering angle) and process parameters on the RTD, RRD and RVD. The overall and partial RTD were directly measured in‐line during the extrusion process and the local ones were calculated by deconvolution based on a statistical theory. The local RTD allowed comparing the mixing performance of mixing elements. Also it was confirmed both experimentally and theoretically that specific throughput, defined as a ratio of throughput (Q) over screw speed (N), controlled all the above three types of residence distributions, be they local, partial or overall. The RRD and RVD do not provide more information on an extrusion process than the corresponding RTD. Rather they are different ways of representing the same phenomena. POLYM. ENG. SCI., 48:19–28, 2008. © 2007 Society of Plastics Engineers 相似文献
87.
Yu. A. Guloyan 《Glass and Ceramics》2008,65(5-6):177-186
Research on the properties and characteristics of glass that determine the serviceability of the most massive glass objects and glassware is reviewed. The theoretical assumptions, general questions concerning the strength, chemical resistance (corrosion), and spectral characteristics of glass are noted. The properties and characteristics indicated are examined for sheet glass, glass fiber, and glassware. 相似文献
88.
Junwei Fu Zhengbiao Zhang Zhenping Cheng Jian Zhu Wei Zhang Xiulin Zhu 《Polymer Bulletin》2008,61(3):287-297
A novel reversible addition-fragmentation chain transfer (RAFT) reagent bearing triphenylamine (TPA)
group, 4-diphenylamino-dithiobenzoic acid benzyl ester (DDABE), was designed and synthesized. It was used
in the RAFT polymerizations of styrene (St) and methyl acrylate (MA) to prepare end-functionalized polymers.
The results of the polymerization showed that the RAFT polymerizations could be well controlled using DDABE
as the RAFT agent. Number-average molecular weight (Mn,GPC) increased linearly
with monomer conversion, and molecular weight distributions were relatively narrow (PDI<
1.50). The results of chain-extension reaction, 1H NMR spectra and UV/Vis
spectra confirmed that most of the polymers chains were end-capped by the functional triphenylamine
(TPA) groups. The effect of feed molar ratios of St/DDABE/AIBN on polymerization was investigated. 相似文献
89.
Yu.V. Butenko P.R. Coxon M. Yeganeh A.C. Brieva K. Liddell V.R. Dhanak L. iller 《Diamond and Related Materials》2008,17(6):962-966
It is generally accepted that diamond is resistant to a wide spectrum of electromagnetic radiation from the ultraviolet through to the soft X-ray range, which makes it very attractive for the fabrication of diamond-based photodetectors. However the effect of photon radiation on the diamond structure has not yet been examined. In the work presented here, photoelectron spectroscopy has been used to study the graphitization of nanodiamond crystallites exposed to extreme ultraviolet radiation. Under such irradiation, the surface hydrogen groups and graphite species are found to prevent graphitization. The mechanism of radiation-induced nanodiamond graphitization is discussed. 相似文献
90.
We present a numerical study of the packing of uniform spheres under three-dimensional vibration using the discrete element method (DEM), focusing on the effects of vibration condition (amplitude and frequency) and inter-particle frictions (sliding and rolling frictions). The results are analysed in terms of packing density, coordination number (CN), radial distribution function (RDF) and pore structure. It is shown that increasing either the vibration amplitude or frequency causes packing density to increase initially to a maximum and then decrease. Both vibration frequency and amplitude should be considered to characterize the effect of vibration process on packing structure. The sliding and rolling frictions between particles can decrease packing density since they dissipate energy, although the effect of rolling friction is less significant. In line with the change of packing density, microstructural properties such as CN, RDF and pore distribution also change: a looser packing often corresponds to smaller CN, less peaked RDF and larger but more widely distributed pores. 相似文献