全文获取类型
收费全文 | 2700篇 |
免费 | 132篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 28篇 |
化学工业 | 816篇 |
金属工艺 | 56篇 |
机械仪表 | 80篇 |
建筑科学 | 91篇 |
矿业工程 | 21篇 |
能源动力 | 88篇 |
轻工业 | 194篇 |
水利工程 | 18篇 |
石油天然气 | 9篇 |
武器工业 | 1篇 |
无线电 | 222篇 |
一般工业技术 | 534篇 |
冶金工业 | 159篇 |
原子能技术 | 33篇 |
自动化技术 | 494篇 |
出版年
2023年 | 31篇 |
2022年 | 121篇 |
2021年 | 116篇 |
2020年 | 87篇 |
2019年 | 66篇 |
2018年 | 97篇 |
2017年 | 101篇 |
2016年 | 97篇 |
2015年 | 92篇 |
2014年 | 129篇 |
2013年 | 208篇 |
2012年 | 154篇 |
2011年 | 180篇 |
2010年 | 134篇 |
2009年 | 125篇 |
2008年 | 137篇 |
2007年 | 105篇 |
2006年 | 90篇 |
2005年 | 82篇 |
2004年 | 60篇 |
2003年 | 57篇 |
2002年 | 49篇 |
2001年 | 32篇 |
2000年 | 28篇 |
1999年 | 28篇 |
1998年 | 40篇 |
1997年 | 23篇 |
1996年 | 18篇 |
1995年 | 26篇 |
1994年 | 24篇 |
1993年 | 22篇 |
1992年 | 16篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 25篇 |
1986年 | 16篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1973年 | 13篇 |
1972年 | 8篇 |
排序方式: 共有2844条查询结果,搜索用时 15 毫秒
1.
2.
Ivan Fortelný Monika Lapčíková František Lednický Zdeněk Starý Zdeněk Kruliš 《Polymer Engineering and Science》2008,48(3):564-571
This article is focused on the phase structure development in immiscible polymer blends during melt mixing. Nonuniformity of the phase structure, i.e., the coexistence of areas containing particles with markedly different size distribution, was detected in quenched and compression molded samples of a number of various blends prepared by long and intensive mixing in the chamber of a Plasticorder. The same effect was found also for polystyrene/polyamide blends prepared in a twin‐screw extruder. It was shown that neglecting nonuniformity of the phase structure can lead to considerable error in evaluation of the effect of system parameters on the blend morphology. The reasons for the effect were discussed and it was found that inhomogeneous flow field in mixers is a plausible explanation of the nonuniform phase structure. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
3.
Iv?n Arce of Core Security Technologies looks at the current state of malware and introduces the articles he selected for this special issue. 相似文献
4.
Ivan Hrivňák 《International Journal of Pressure Vessels and Piping》1985,20(3):223-237
This paper deals with the metallurgical changes which occur during heat treatment of welded joints. Stress relieving heat treatment in the temperature range below A1, the normalizing heat treatment and the heat treatment in the intercritical range A1–A3, are all considered. The thermal regime of welding is described. The practice of intercover of the weldment before applying PWHT to ambient temperature is described. It is stressed that the aim of stress-relieving heat treatment is not only to relax internal stresses but also to improve the microstructure and impact properties of HAZ and weld metal, to improve dimensional stability and increase resistance against stress corrosion. Examples are given of the effect of annealing in the intercritical range A1–A3 on the improvement in toughness of electroslag welded joints. Changes in dislocation distribution and density, precipitation processes and grain sizes during PWHT are described. 相似文献
5.
Ivan Cimrák 《Archives of Computational Methods in Engineering》2007,15(3):277-309
The Landau-Lifshitz (LL)equation of micromagnetism governs rich variety of the evolution of magnetization patterns in ferromagnetic
media. This is due to the complexity of physical quantities appearing in the LL equation. This complexity causes also an interesting
mathematical properties of the LL equation: nonlocal character for some quantities,nonconvex side-constraints, strongly nonlinear
terms. These effects influence also the numerical approximations. In this work, recent developments on the approximation of
weak solutions, together with the overview of well-known methods for strong solutions,are addressed.
Author is supported by the Fund for Scientific Research - Flanders FWO (Belgium). 相似文献
6.
Fish oils containing different levels of polymers of triacylglycerols formed during autoxidation were incubated with pancreatic
lipase to establish whether these polymers are substrates for lipase hydrolysis. With oils containing low amounts (less than
4%) of triacylglycerol polymers as substrates, both triacylglycerols and polymers of triacylglycerols were almost completely
hydrolyzed, and fatty acid monomers and monoacylglycerols were the major lipid products. Under the same incubation conditions,
some triacylglycerols remained intact when highly oxidized oils containing 20 or 30% triacylglycerol polymers were the substrate.
The fatty acid composition of these residual triacylglycerols was almost identical to that of triacylglycerols present at
the start of the assay. When fish oil containing 30% triacylglycerol polymers was incubated with the lipase, the component
triacylglycerols and polymers of triacylglycerols were hydrolyzed at similar rates, and fatty acid dimers were detected as
a product. It is concluded that the high molecular weight polymers of triacylglycerols present in oxidized fish oils can be
hydrolyzed by pancreatic lipasein vitro. 相似文献
7.
With the help of DTA, DTG elementary analysis of carbonized residues and ESR spectroscopy the influence of anionic form on thermooxidation of trimethylammoniumhydroxyprophyl (TMAHP)–cellulose was studied. At 300°C the percentage of carbon in carbonized residue thermolyzed in oxidative atmosphere is higher than for the sample degraded in inert atmosphere. The percentage of hydrogen decreases simultaneously. The concentration of free radicals in thermolyzed residue also increases due to the presence of oxygen. We propose that oxygen is abstracting the hydrogen atoms from polysaccharide and unpaired electrons on carbon atoms are produced. At 400°C the percentage of carbon in residues prepared at inert atmosphere is higher than for residue formed at oxidative atmosphere. Also the concentration of free radicals in thermolyzed residues obtained in inert atmosphere is greater than for those from oxidative ones. That is why suppose that at this temperature oxygen is bonded to polysaccharide residue and free radicals are terminated. From the semiquantitative DTA we can make the following sequence of samples according to their increasing thermooxidative effect: unmodified cellulose < A–HSO < A–Br? < A–I? < A–NO < A–H2PO < A–CH3COO? < A–HCO < A–F? < A–Cl?1 < A–OHp?. 相似文献
8.
Summary The synthesis is reported of copolymers of styrene with methacrylic acid and of methyl methacrylate with methacrylic acid by radical copolymerization, of copolymers of methyl methacrylate with methacrylic acid by partial alkaline hydrolysis of poly(methyl methacrylate), and of block copolymers of styrene with methacrylic acid. Modified titration curves of all these copolymers were recorded in water and water-ethanol solutions. In a solution containing 50 mass.% ethanol, only small differences could be observed between the potentiometric behaviour of the individual copolymers and polymethacrylic acid. Also, there were no essential differences in any of the solvents used between the potentiometric behaviour of block copolymers of styrene with methacrylic acid, on the one hand, and polymethacrylic acid, on the other. On the contrary, maxima and minima were always observed on the modified titration curves of statistical copolymers with a higher content of the hydrophobic comonomer in solutions with a high water content. Thus, using the modified titration curves, it is possible to decide whether a given copolymer is of the block or statistical type. 相似文献
9.
The flow structure of a continuous‐flow reactor stirred by a Rushton turbine was investigated by laser Doppler velocimetry for two different mean residence time‐mixing time ratios. Velocity measurements were obtained for two inlet locations, corresponding to the incoming liquid stream being fed co‐currently or counter‐currently to the flow discharged by the turbine. In all investigated configurations and for all operating conditions, it was found that the flow disruption caused by the incoming liquid stream was observable mainly in the first vessel quarter, which followed the feed‐tube plane. From comparison of the velocities encountered in the various planes in the continuous‐flow reactor to the velocities of the batch reactor, it was also concluded that it may be possible to intensify the usage of the turbine‐stirred vessel by decreasing the characteristic times ratio, without considerable flow by‐pass and/or short‐circuiting problems. 相似文献
10.
Sonia M. Rogacheva Margarita J. Kuntcheva Ivan N. Panchev Tzvetan D. Obretenov 《European Food Research and Technology》1995,200(1):52-58
The influence of the water content, molar ratio, time and temperature on the formation of nondialysable melanoidins produced by the interaction ofl-ascorbic acid and glycine has been studied. The isolated polymers have been characterized by spectrum analysis and fractionated using gel chromatography. The rate constants of the reaction for temperatures of 90°C, 100°C and 110°C have been calculated and are (0.84±0.29) x 10?5 x s?1, (1.33±0.14) x 10?5 x s?1 and (5.30±0.37) x 10?5 x s?1 respectively. The activation energy of the reaction has been determined to be 106.07±32.47 kJ/mol. 相似文献