全文获取类型
收费全文 | 86101篇 |
免费 | 11246篇 |
国内免费 | 6800篇 |
专业分类
电工技术 | 9090篇 |
技术理论 | 7篇 |
综合类 | 10737篇 |
化学工业 | 12587篇 |
金属工艺 | 2042篇 |
机械仪表 | 4603篇 |
建筑科学 | 5482篇 |
矿业工程 | 1297篇 |
能源动力 | 5944篇 |
轻工业 | 4031篇 |
水利工程 | 1999篇 |
石油天然气 | 2134篇 |
武器工业 | 827篇 |
无线电 | 9538篇 |
一般工业技术 | 8725篇 |
冶金工业 | 2215篇 |
原子能技术 | 1301篇 |
自动化技术 | 21588篇 |
出版年
2024年 | 463篇 |
2023年 | 1446篇 |
2022年 | 2375篇 |
2021年 | 2698篇 |
2020年 | 2871篇 |
2019年 | 2637篇 |
2018年 | 2475篇 |
2017年 | 2896篇 |
2016年 | 3142篇 |
2015年 | 3319篇 |
2014年 | 4901篇 |
2013年 | 5538篇 |
2012年 | 5845篇 |
2011年 | 6246篇 |
2010年 | 4891篇 |
2009年 | 5163篇 |
2008年 | 5209篇 |
2007年 | 6018篇 |
2006年 | 5322篇 |
2005年 | 4972篇 |
2004年 | 4121篇 |
2003年 | 3590篇 |
2002年 | 2970篇 |
2001年 | 2466篇 |
2000年 | 2090篇 |
1999年 | 1707篇 |
1998年 | 1462篇 |
1997年 | 1246篇 |
1996年 | 1104篇 |
1995年 | 976篇 |
1994年 | 777篇 |
1993年 | 593篇 |
1992年 | 542篇 |
1991年 | 403篇 |
1990年 | 359篇 |
1989年 | 308篇 |
1988年 | 220篇 |
1987年 | 145篇 |
1986年 | 114篇 |
1985年 | 92篇 |
1984年 | 95篇 |
1983年 | 78篇 |
1982年 | 52篇 |
1981年 | 30篇 |
1980年 | 32篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1976年 | 11篇 |
1959年 | 18篇 |
1951年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
54.
Optical measurements of thermal diffusivity of a material 总被引:2,自引:0,他引:2
The measurement of thermal diffusivity of a material (in particular, a thin film) is important for various reasons, e.g., to predict the heat transfer in the solid subjected to a thermal process, to monitor surface composition or morphology, or to detect invisible subsurface defects like delaminations. This measurement can be done in a noncontact manner using various photothermal methods. Such methods typically involve pulsed heating of the surface by small amounts using a laser source; the decay of the surface temperature after this pulsed photothermal heating is then probed to provide the thermal diffusivity. Various probing methods have been developed in the literature, including the probing of reflection, refraction, and diffraction from the pulsed heated area, infrared thermal radiometry, and surface deformation. This paper provides an overview of such techniques and some examples of their applications. 相似文献
55.
Keh-Shin Lii 《时间序列分析杂志》1985,6(3):153-169
Abstract. A distributed lag model with a rational transfer function is considered. We have demonstrated that the C -table can be used to determine the orders of the rational transfer function and the Padé table can be used to estimate the parameters of an identifiable transfer function. In case the model is not uniquely identified, the C -table reduces possible competing models to only a few for further examination. Padé approximant gives consistent initial values for possibly more efficient iterative procedures to estimate the coefficients of the identified model. Some asymptotic results on the estimation of the C -table and the Padé table are given. A few examples are presented to demonstrate the effectiveness of the method. 相似文献
56.
An approach to solving a linear interpolation problem in a fuzzy information space is proposed. Two different schemes of interpolation
are outlined: a heuristic one, based on the geometrical interpretation of operations, and an optimization one, based on the
expansion principle. The results obtained allow performing fuzzy linear prediction.
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 55–68, March–April 2006. 相似文献
57.
58.
MODELING LIQUID MASS TRANSFER IN HIGEE SEPARATION PROCESS 总被引:1,自引:0,他引:1
Correspondence concerning this paper should be addressed to Professor Richard S.H. Mah. Hsien-Hsin Tung is now affiliated with Department of Chemical Engineering, California Institute of Technology
Penetration theory is used to describe the liquid mass transfer in Higee separation process. Within a possible range of effective areas, it is shown that the predicted mass transfer coefficients are in reasonable agreement with the estimated mass transfer coefficients. The estimated coefficients were calculated from the experimental data and the possible effective areas. Hence it is concluded the penetration theory is generally applicable to describe liquid mass transfer in Higee separation process. The comparison also suggests that liquid mixing at the junctions of packing materials may be more complete in Higee process than in traditional process. 相似文献
Penetration theory is used to describe the liquid mass transfer in Higee separation process. Within a possible range of effective areas, it is shown that the predicted mass transfer coefficients are in reasonable agreement with the estimated mass transfer coefficients. The estimated coefficients were calculated from the experimental data and the possible effective areas. Hence it is concluded the penetration theory is generally applicable to describe liquid mass transfer in Higee separation process. The comparison also suggests that liquid mixing at the junctions of packing materials may be more complete in Higee process than in traditional process. 相似文献
59.
《Drying Technology》2007,25(7):1237-1242
Rewarming of fruits and vegetables after cooling is characterized by heat and mass transfer processes, which leads commonly to condensation of water on the produce surface at temperatures below the dew point. This effect may affect the produce quality due to microbial growth at unfavorable environmental conditions. The amount of condensed water is a function of the produce surface temperature and of the surrounding conditions as air temperature, air humidity, and air flow. Under practical conditions, both the warming and the condensation are strongly affected by the packaging system used. Depending on the flow conditions close to the produce surface, parameters of heat and mass transfer under laboratory conditions were measured. A mathematical model was developed for the determination of the amount of condensed water on fruit surfaces, its reevaporation, and its total dwell time dependent on the environment air conditions. The model describes the heat and mass transfer processes on single fruits. The process of diffusion of humidity in air and proceed of surface temperature is the basis for the model. 相似文献
60.
Optimizing of laminar viscous flow through a pipe by two dimensionless values is investigated analytically. Dimensionless entropy generation and pumping power to heat transfer rate ratio are used as basis for constant viscous and the temperature dependence on the viscosity. For this matter we calculate entropy generation and pumping power for a fully developed in a pipe subjected to constant wall temperature for either constant viscosity and the variable viscosity. The variation entropy generation increase along the pipe length for viscous fluid is drawn, either the variation summation dimensionless entropy generation and the pumping power to heat transfer rate ratio are varying the fluid inlet temperature for fixed pipe length and are varying pipe length for fixed fluid inlet temperature are drawn. For low heat transfer conditions the entropy generation due to viscosity friction becomes dominant and the dependence of viscosity with the temperature becomes essentially important to be considered. 相似文献