全文获取类型
收费全文 | 767篇 |
免费 | 8篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 39篇 |
综合类 | 2篇 |
化学工业 | 257篇 |
金属工艺 | 22篇 |
机械仪表 | 32篇 |
建筑科学 | 9篇 |
能源动力 | 27篇 |
轻工业 | 60篇 |
水利工程 | 11篇 |
无线电 | 49篇 |
一般工业技术 | 151篇 |
冶金工业 | 19篇 |
原子能技术 | 14篇 |
自动化技术 | 87篇 |
出版年
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2018年 | 8篇 |
2017年 | 3篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 29篇 |
2012年 | 34篇 |
2011年 | 46篇 |
2010年 | 34篇 |
2009年 | 34篇 |
2008年 | 44篇 |
2007年 | 41篇 |
2006年 | 31篇 |
2005年 | 27篇 |
2004年 | 27篇 |
2003年 | 31篇 |
2002年 | 33篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 17篇 |
1997年 | 12篇 |
1996年 | 24篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 16篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 14篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 15篇 |
1985年 | 14篇 |
1984年 | 20篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 4篇 |
排序方式: 共有779条查询结果,搜索用时 15 毫秒
81.
Summary Copolymerization of ethylene with -olefins, i.e. propylene, butene-1, 4-methyl-pentene-1(4-MP-1), was carried out by a MgCl2 supported TiCl4 catalyst in combination with Et3Al at a temperature as high as 170 °C at which the polymerization system was homogeneous. This catalytic system showed very a high activity and produced copolymers having a density of 0.91–0.94 g/ml. Of these three kinds of comonomers, propylene showed the highest reactivity and caused most frequently the termination of a polymer growing by chain transfer reaction and produced copolymers having the broadest MWD. 相似文献
82.
Summary Propylene polymerization was performed with a highly active MgCl supported TiCl4 in conjunction with Et3Al and ethyl benzoate (EB). The obtained polypropylene sample was separated into four fractions by successive extraction with pentane, heptane and trichloroethylene (trichlene). Yield, Mn, Tm and microtacticity of each fraction were determined, and the effects of the concentration of EB on these items of results were investigated. It has been found that EB enhances yield, Mn and stereospecificity of trichlene insoluble (the most stereospecific) fraction, and in contrast, it decreases rapidly yields of other three fractions without changing the character of the polymers. From these findings, the functions of EB to the active centers were discussed. 相似文献
83.
Polarisation mode dispersion measurements based on optical heterodyne detection are demonstrated. Using the detection technique, length dependence of group delay difference between two orthogonally polarised HE11 modes in an elliptical-core fibre was measured at a wavelength of 1.3 ?m. The modal dispersion was found to depend linearly on length in the range of 0?500 m for a fibre with modal birefringence of 1.5×10?5. 相似文献
84.
Enzyme sensors for glucose and uric acid have been developed based on a solid-electrolyte cell using NASICON (Na3Zr2Si2PO12). These potentiometric devices respond reversibly to glucose and uric acid over a concentration range of two orders of magnitude with sensitivities of −54 and −52 mV/decade, respectively. The sensors can be used for a batch-type as well as a flow-through-type measuring system. Primarily the sensors respond to the H2O2 that is produced by the enzymatic reactions. The role of the three-phase region, electrolyte solution, sensing electrode metal and NASICON has been investigated. The liquid electrolyte/sensing electrode metal interface is found to work as a potential-determining as well as a rate-determining interface for the enzyme sensor. 相似文献
85.
A fractional dissolution on the oxymethylene copolymer obtained by the iodine-initiated, solid-state copolymerization of the tetraoxane–1,3-dioxolane-methylal system has been carried out using a mixed solvent which consists of tetrachloroethane, phenol, and cyclohexanol. On the fractional dissolution, the oxymethylene copolymer was divided mainly into two parts: one was the copolymer containing a larger amount of ethylene oxide unit in its main chain and having lower molecular weight; the other was copolymer containing a smaller amount of ethylene oxide unit and having a higher molecular weight. It was reasonably concluded that in this copolymerization system, the reaction proceeds from the surface to the center of the tetraoxane crystal to give a divided copolymer due to the heterogeneous properties such as copolymer composition and molecular weight. 相似文献
86.
Sotoo Asakura Hiroko Ueda Norio Ohnishi 《Drug development and industrial pharmacy》1993,19(13):1629-1636
The in vitro dissolution rates of ceftizoxime suppository were compared using a rotating dialysis cell method, a dialysis membrane method and the JP XI rotating basket method. Only small variations in the dissolution rates were found with the rotating dialysis cell method and the rotating basket method, while the dialysis membrane method indicated rather large variation than other methods. In the rotating basket method, it was observed that a part of suppository bases came out through the wire mesh of the basket and spread over the surface of the dissolution medium. In the case of dialysis membrane method, it seemed that the large variations in dissolution rate was depending on a skill of the apparatus used.
As to obtain a good results, a selection of the rotating dialysis cell method was important. In vitro dissolutions of Ceftizoxime(CZX) suppository by using the rotating dialysis cell method were very rapid and also consistent with the absorption characteristics reported previously by Motohiro after rectal dose in pediatric subjects. 相似文献
As to obtain a good results, a selection of the rotating dialysis cell method was important. In vitro dissolutions of Ceftizoxime(CZX) suppository by using the rotating dialysis cell method were very rapid and also consistent with the absorption characteristics reported previously by Motohiro after rectal dose in pediatric subjects. 相似文献
87.
88.
Shusaku Hiraki Norio Watanabe Yoshiaki Ishihara Yuan-Ming Su 《Computers & Industrial Engineering》1994,27(1-4):205-208
This paper aims to design a production planning and control system to realize high productivity and low inventory in the international cooperative global complementary production system for mutual country's development. 相似文献
89.
Mechanism of high energy absorption by foamed materials-foamed rigid polyurethane and foamed glass 总被引:1,自引:0,他引:1
Toshio Kurauchi Norio Sato Osami Kamigaito Noboru Komatsu 《Journal of Materials Science》1984,19(3):871-880
Energy absorbability of foamed rigid materials, polyurethane and glass, was studied under a compressive load. The brittle materials were proved to absorb much energy in a manner similar to ductile materials. A mechanism for such high energy absorption was proposed, based on a fracture model in which crushing of cells initiates at the weakest cell followed by propagation to cells lying in the layer containing the weakest one and lying in a direction perpendicular to the compressive force; then the crushing propagates to another layer under the compressive force after the completion of the first layer crushing. In the period of one layer crushing, the strain energy stored in the period of compression prior to the crushing is temporarily released, and it is stored again in the period of compression after the crushing. The store and release of strain energy is assumed to be repeated until all cell layers are crushed. This mechanism of layer-by-layer crushing allows the cells to absorb strain energy repeatedly, and causes high energy absorption in the brittle foamed material. The calculated energy based on the mechanism agrees well with the observed one. 相似文献
90.
A nondestructive method is proposed for evaluating power coupling coefficients of directional couplers contained in an optical integrated circuit. This technique, which is based on optical heterodyne interferometry, makes it possible to obtain individual coupler element information without removing the element from the optical circuit. General N -channel waveguide coupling characteristics are analyzed, and they are experimentally evaluated for two- and four-channel waveguides that have been practically designed as frequency multi/demultiplexers operating in the 1.55-μm-wavelength region 相似文献