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111.
宽带IP城域网及其应用 总被引:1,自引:0,他引:1
文章结合南京电信公众宽带IP城域网的建设,对宽带IP城域网的网络结构、用户接入安全、网络管理和认证计费作了阐述,并简要介绍了应用于宽带IP城域网上的一些业务。 相似文献
112.
N. Marilleau C. Cambier A. Drogoul J.-L. Chotte E. Perrier E. Blanchart 《Simulation Modelling Practice and Theory》2008,16(7):736-745
Soils are important components of ecosystem and their functioning is of great importance for human well-being. Describing, understanding, foreseeing, and controlling biological activities and functions in soil in the context of global change are major objectives for scientists. Modelling soil bioturbation by soil engineers is of great importance although it is faced with the difficulty to describe the soil physical environment. Creating a model of a soil leads to complexity problems: a soil is a multi-scale heterogeneous, three-dimensional and dynamic environment that cannot be modelled and simulated without defining a suitable and optimized representation and taking assumptions about the studied system. An approach based on fractal theory (often used in soil sciences) was chosen to model such a real complex environment; it was integrated into a multi-agent system (MAS). MAS allows to simulate situated agents (earthworms) in an virtual world. The originality of this present MAS is that it is based on a dynamic environment which builds itself, on demand, according to an abstract canvas tree and agent movements. The aim of this paper is to present this approach and its originality, and to describe the model and the simulator. A theoretical view of the approach is given and applied to a case study: the impact of earthworms on soil structure and organic matter dynamics. 相似文献
113.
Hou Qing-Feng Lu Xian-Cai Liu Xian-Dong Hu Bai-Xing Cui Ju-Qing Shen Jian 《Surface & coatings technology》2005,190(2-3):394-399
In this paper, surface fractal analysis is carried out to study the surface of carbon nanotubes after the adsorption of poly(acrylic acid) (PAA) using the thermodynamic method. The fractal dimension (dSF ) of a fractal surface, BET surface area (SBET) and pore size distribution (PSD) are calculated from low-temperature nitrogen adsorption isotherms. The value of dSF declines as the adsorption amount of PAA increases, which means the adsorption may lower the surface roughness of the carbon nanotubes. The PSD pattern was modified obviously after the adsorption of PAA because of the pore-blocking effect. Additionally, an excellent linear decrease in the BET surface area of carbon nanotubes is found as the adsorption amount of PAA increases, which can be attributed to both the pore-blocking effect and the surface-screening effect. The results of the present work may facilitate our understanding of the interaction between polymer and the carbon nanotubes at the microscale occurring on irregular interfaces. 相似文献
114.
Alternating current (AC) voltammetry and electrochemical impedance spectroscopy are often the methods of choice for use in study of adsorption of organic molecules. The adsorption of organic molecules on interface may result in the formation of fractal structures, whose fractal dimension can be estimated using the method of scaling the hanging mercury drop electrode (HMDE). The aim of present study was to check whether the estimated fractal dimension, D (or for that matter the fractal ordering of the adsorbed layer) shows any correlation (dependence) with change of applied frequency, and second, to check the possibility to extend the method to broad frequency spectrum compatible with impedance spectroscopy. The investigation included two surfactants nonionic Triton-X-100 (T-X-100) and anionic sodium dodecyl sulfate (SDS) and alcohol tert-butanol. All measurements were performed on HMDE at thermodynamic equilibrium employing broad frequency spectrum. The validity of the approach was checked by measurements on pure electrolyte and by comparison with previously obtained results for fractal layers. The results of the investigations show that: (1) the method of scaling the HMDE to obtain the fractal dimension of adsorbed layer is compatible with impedance spectroscopy and the combination of these methods can be used as a powerful tool to investigate fractal aspect of adsorption of organic molecules; (2) fractal ordering of adsorbed layer and the value of fractal dimension is not influenced by the frequency of applied sinusoidal voltage perturbations. 相似文献
115.
Dongming Tang Alejandro G. Marangoni 《Journal of the American Oil Chemists' Society》2008,85(6):495-499
The microstructure of fat crystal networks is closely related to rheological properties of fat products, and thus is of particular
interest to food scientists. The fractal dimensions of fat crystal networks calculated by microscopy methods such as box-counting,
D
b, particle-counting, D
f, and mass fractal dimension, D
m, have been extensively employed to quantify the microstructure of fats. This work revealed the microstructural basis of D
b, D
f, and D
m in 3D space through both computer simulation and experiments on the high melting fraction of milk fat crystal networks. Similar
to our previous simulation study on the fractal dimensions of fat crystal networks in 2D space, D
b is sensitive to crystal size, area fraction, and not sensitive to distribution orderliness of crystals, which is the percentage
of evenly distributed fat crystals within the simulated fat crystal networks. D
f and D
m were not affected by any of the microstructural factors studied in the simulation. 相似文献
116.
This paper describes the use of fractal geometry in determining the characteristics of some geological media, such as clayey
and pumice soils. Attention is drawn to the determination of the specific surface of some clays of southern Italy and of pumice
of the Vesuvius eruption of 79 a.d. The analysis proposed gives the Minkowski dimension of soils expressed by the power law,
or the equation Mδ(F)≈Cδ–s; this is a dimensionless number. The values of Minkowski dimension obtained have been compared with the values obtained by
physical methods (mercury porosimetry and the bottle helium test). The analyses conducted prove that, for the range of magnification
adopted, the media examined behave as irregular or fractal sets.
Received: 10 July 1999 · Accepted: 8 October 1999 相似文献
117.
基于材性试验研究了粗骨料级配对橡胶混凝土构件强度及弹性模量的影响;通过三根不同级配粗骨料橡胶混凝土梁探讨了粗骨料级配对试验梁受弯承载力、挠度等方面的影响,并研究了三根橡胶混凝土梁在集中荷载下损伤演化过程的分形行为。用分形几何学研究橡胶混凝土梁的损伤演化过程,为橡胶混凝土结构的健康检测和安全性评估提供新的方法。 相似文献
118.
119.
120.
红旗泡水库冰面裂缝图像信息提取和初步分析 总被引:1,自引:0,他引:1
利用2008~2009年冬季在大庆红旗泡水库获取的138幅冰裂缝数码照片进行图像分析。比较了Image-Pro Plus方法和ACD See和Photoshop联合方法在冰裂缝分析中的优缺点。结果表明运用Image-Pro Plus方法可以自动化处理,但该方法在图片裂缝处理的结果很不精确,只能用于粗略估算。ACD See和Photoshop联合方法处理的结果相对于前一种方法精确,但其操作复杂,与前一种方法相比处理速度较慢。此外运用分形理论,对冰面裂缝进行分析处理,得到分形维数在1.2~1.7之间,冰裂缝分形维数和冰裂缝密度之间有很好的相关性;而冰裂缝角度无论是主要裂缝还是次要裂缝,都具有自相似性,表明冰面裂缝的产生机理相同。 相似文献