全文获取类型
收费全文 | 1575篇 |
免费 | 53篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 83篇 |
综合类 | 2篇 |
化学工业 | 612篇 |
金属工艺 | 50篇 |
机械仪表 | 44篇 |
建筑科学 | 32篇 |
能源动力 | 93篇 |
轻工业 | 112篇 |
石油天然气 | 5篇 |
无线电 | 97篇 |
一般工业技术 | 364篇 |
冶金工业 | 44篇 |
原子能技术 | 31篇 |
自动化技术 | 66篇 |
出版年
2021年 | 17篇 |
2019年 | 16篇 |
2018年 | 19篇 |
2017年 | 17篇 |
2016年 | 15篇 |
2015年 | 18篇 |
2014年 | 42篇 |
2013年 | 78篇 |
2012年 | 75篇 |
2011年 | 83篇 |
2010年 | 79篇 |
2009年 | 81篇 |
2008年 | 82篇 |
2007年 | 68篇 |
2006年 | 66篇 |
2005年 | 43篇 |
2004年 | 51篇 |
2003年 | 47篇 |
2002年 | 46篇 |
2001年 | 37篇 |
2000年 | 35篇 |
1999年 | 36篇 |
1998年 | 33篇 |
1997年 | 26篇 |
1996年 | 33篇 |
1995年 | 29篇 |
1994年 | 23篇 |
1993年 | 31篇 |
1992年 | 26篇 |
1991年 | 19篇 |
1990年 | 22篇 |
1989年 | 28篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 21篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 17篇 |
1982年 | 18篇 |
1981年 | 18篇 |
1980年 | 14篇 |
1979年 | 32篇 |
1978年 | 16篇 |
1977年 | 17篇 |
1976年 | 11篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 10篇 |
1972年 | 14篇 |
1970年 | 6篇 |
排序方式: 共有1635条查询结果,搜索用时 15 毫秒
101.
102.
Yoshio Ono 《Catalysis Reviews》2013,55(3):179-226
Much attention has been paid to the transformation of lower alkanes such as propane and butanes into aromatic hydrocarbons from both industrial and academic points of view. The aromatic hydrocarbons can be utilized as a booster for high octane number gasoline and are fundamental raw chemicals in petroleum chemistry. The activation of lower alkanes is an intriguing subject. In early work, Csicsery [1–5] described dehydrocyclodimerization of lower alkanes over bifunctional catalysts such as platinum on alumina and Cr2O3 on alumina. 相似文献
103.
Yoshio Ebisu 《Metallurgical and Materials Transactions B》2011,42(2):341-369
A numerical method for analyzing solidification phenomena of multicomponent alloys is presented. This method consists of macroscopic
transport governing equations expressed in terms of a nonlinear multicomponent alloy model, which is coupled with the microscopic
dendritic solidification model to estimate permeability. Numerical simulations were performed for channel segregation in a
steel ingot and for freckles in a Ni-base IN718 remelted ingot and in Ni-10 wt pct Al directionally solidified (DS) ingots.
The results show good agreement with experimental observations. The electromagnetic (EM) braking effect by static magnetic
field was incorporated into the numerical method, and the anisotropic behavior of magnetic field was investigated on the DS
Ni-10 wt pct Al ingots. Application of relatively low magnetic fields in the transverse to the growth direction (B
x
or B
y
) resulted in formation of distorted freckles as a result of the nonuniform liquid flow induced in the transverse direction.
It is shown that a considerably high magnetic field is required to suppress the distorted freckles and other freckles developed
in longitudinal direction. However, there is a risk of the breakdown of DS. On the other hand, when applying the magnetic
fields parallel to the growth direction (B
z
), the number of freckles inversely increased at low magnetic fields, but the freckles were eliminated by about the same level
of high magnetic field as that of B
x
or B
y
. Because the parallel magnetic field suppresses the liquid flow vector components uniformly within the transverse plane,
the nonuniform flow does not occur in the transverse directions. As a result, it suppresses the flow in the growth direction.
It is envisioned that the application of the parallel magnetic field is beneficial in the commercial production of DS castings. 相似文献
104.
The feasibility of a proposed system that combines a magnesium oxide/water chemical heat pump and a diesel engine as a cogeneration system is discussed based on experimental results. The combined system is intended to utilize the waste heat discharge from the engine by means of the chemical heat pump and to level the heat supply load of the engine, allowing enhanced energy utilization. The thermal performance of the chemical heat pump in the cogeneration system is estimated based on the results of a packed‐bed experiment. The estimation indicates that by storing the waste heat from the engine during low demand periods, the cogeneration system can produce more than several times the standard thermal output of the diesel engine during peak demand periods. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
105.
Masao Sugawara Masamitsu Kataoka Kazunori Odashima Yoshio Umezawa 《Thin solid films》1989,180(1-2):129-133
Biomimetic “ion-channel sensors” based on host-guest molecular recognition were constructed by incorporating several kinds of receptor molecules in Langmuir-Blodgett (LB) molecular assemblies deposited directly on glassy carbon electrodes. The receptors used were valinomycin, bis(crown ether)s, macrocyclic polyamine and cyclodextrin polyamine. The binding of charged stimulants (metal ions, inorganic and organic anions) to these receptors induced a marked increase (or decrease) in the ion permeability of the membranes, as detected by cyclic voltammetry using [Fe(CN)6]4- or [Ru(bpy)3]2+ as marker ion. Such a mode of response, corresponding to model “channel opening (or closing)”, can be explained on the basis of the charge-charge interaction involving the stimulant, marker ion and lipid. 相似文献
106.
Yoshio Nishi Koreyuki Tunashima 《Journal of Infrared, Millimeter and Terahertz Waves》1987,8(11):1453-1470
In FIR laser emissions optically by a CO2 laser, it has been reported that there are two different process namely “induced Raman scattering” and “population inversion transition”. In this paper, we show that the two different process have clearly different characteristics in emission frequensies and pulse waveforms in the case of a TEA-CO2 laser excitation. We used in this work an intra-cavity etalon for the study of the emission frequensies and also we used a MOM point contact diode for the detection of the wavaformes. Especially, we show that the FIR pulse waveformes are able to analyze numerically on the concept of rate equations. In conclusion, we indicate that molecules would be classified into two categories with regard to optically pumping by a TEA-CO2 laser. One of them produce mainly Raman scattered emissions, and other produce only the FIR emissions from population inversion transition in spite of high power intensity excitation. 相似文献
107.
Yoshio Nishi 《Journal of Infrared, Millimeter and Terahertz Waves》1987,8(9):1189-1210
The author reports that TEA-CO2 with an intra-cavity etalon is a useful pumping source which can deliver widely tunable beam (tunable range ~1 GHz) with accurate oscillation frequencies and with high power compared to a tunable wave guide laser. The source is applied to the excitations of CH3OH and the FIR emissions from it are well assigned for there absorption transitions and FIR emissions. This proves that the source display not only usefulness for development of new FIR emissions but also for molecular spectroscopy. 相似文献
108.
Hydrothermal Corrosion of Alumina Ceramics 总被引:1,自引:0,他引:1
The corrosion behavior and strength degradation of alumina ceramics with 99%, 99.9%, and 99.99% Al2 O3 were studied in water at 300°C and 8.6 MPa for 1 to 10 d. The weight loss in alumina ceramics was mainly attributed to the dissolution of SiO2 and Na2 O grain-boundary impurities. Intergranular corrosion proceeded in the alumina ceramics by preferential attack at the grain boundaries. The extent of the strength reduction for corroded alumina ceramics was related to the impurity level in the alumina ceramics. 相似文献
109.
110.
Tomoya Nagira Shugo Morita Hiroyoshi Yokota Hideyuki Yasuda Christopher M. Gourlay Masato Yoshiya Akira Sugiyama Kentaro Uesugi Akihisa Takeuchi Yoshio Suzuki 《Metallurgical and Materials Transactions A》2014,45(12):5613-5623
Synchrotron X-ray radiography at 125 frames per second was used to study deformation mechanisms in semi-solid Fe-C alloys at high solid fraction and shear strain rates of 10?1/s. An image correlation approach was also used to quantify the shear strain fields and study shear-induced dilation and the origin of shear cracking. It was shown that, at high solid fraction (90 to 93 pct solid), rearrangement including rotation and translation of solid particles became restricted and shear strain localized into narrow liquid-filled channels/fissures. Shear cracking was shown to originate from inadequate liquid flow into the expanding spaces between solid particles caused by shear-induced dilation. At lower solid fraction (~85 pct solid), solid particles rearranged with a significantly higher component of rotation leading to more shear-induced dilation and a wider shear band. 相似文献