全文获取类型
收费全文 | 1753篇 |
免费 | 93篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 24篇 |
综合类 | 1篇 |
化学工业 | 366篇 |
金属工艺 | 40篇 |
机械仪表 | 50篇 |
建筑科学 | 46篇 |
矿业工程 | 8篇 |
能源动力 | 40篇 |
轻工业 | 180篇 |
水利工程 | 5篇 |
石油天然气 | 4篇 |
无线电 | 80篇 |
一般工业技术 | 344篇 |
冶金工业 | 426篇 |
原子能技术 | 6篇 |
自动化技术 | 228篇 |
出版年
2023年 | 19篇 |
2022年 | 12篇 |
2021年 | 34篇 |
2020年 | 20篇 |
2019年 | 33篇 |
2018年 | 61篇 |
2017年 | 53篇 |
2016年 | 68篇 |
2015年 | 63篇 |
2014年 | 66篇 |
2013年 | 104篇 |
2012年 | 92篇 |
2011年 | 100篇 |
2010年 | 60篇 |
2009年 | 70篇 |
2008年 | 52篇 |
2007年 | 59篇 |
2006年 | 42篇 |
2005年 | 44篇 |
2004年 | 24篇 |
2003年 | 26篇 |
2002年 | 32篇 |
2001年 | 15篇 |
2000年 | 21篇 |
1999年 | 22篇 |
1998年 | 123篇 |
1997年 | 78篇 |
1996年 | 64篇 |
1995年 | 31篇 |
1994年 | 25篇 |
1993年 | 28篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 12篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 17篇 |
1980年 | 16篇 |
1979年 | 11篇 |
1977年 | 13篇 |
1976年 | 30篇 |
1973年 | 10篇 |
1940年 | 10篇 |
1939年 | 6篇 |
1938年 | 6篇 |
排序方式: 共有1848条查询结果,搜索用时 312 毫秒
51.
In the first part of this article, we analyze the relation between local image structures (i.e., homogeneous, edge-like, corner-like or texture-like structures) and the underlying local 3D structure (represented in terms of continuous surfaces and different kinds of 3D discontinuities) using range data with real-world color images. We find that homogeneous image structures correspond to continuous surfaces, and discontinuities are mainly formed by edge-like or corner-like structures, which we discuss regarding potential computer vision applications and existing assumptions about the 3D world. In the second part, we utilize the measurements developed in the first part to investigate how the depth at homogeneous image structures is related to the depth of neighbor edges. For this, we first extract the local 3D structure of regularly sampled points, and then, analyze the coplanarity relation between these local 3D structures. We show that the likelihood to find a certain depth at a homogeneous image patch depends on the distance between the image patch and a neighbor edge. We find that this dependence is higher when there is a second neighbor edge which is coplanar with the first neighbor edge. These results allow deriving statistically based prediction models for depth interpolation on homogeneous image structures. 相似文献
52.
Sparse nonlinear classification and regression models in reproducing kernel Hilbert spaces (RKHSs) are considered. The use of Mercer kernels and the square loss function gives rise to an overdetermined linear least-squares problem in the corresponding RKHS. When we apply a greedy forward selection scheme, the least-squares problem may be solved by an order-recursive update of the pseudoinverse in each iteration step. The computational time is linear with respect to the number of the selected training samples. 相似文献
53.
Free binary decision diagrams (FBDDs) are graph-based data structures representing Boolean functions with the constraint (additional
to binary decision diagram) that each variable is tested at most once during the computation. The function EARn is the following Boolean function defined for n × n Boolean matrices: EARn(M) = 1 iff the matrix M contains two equal adjacent rows. We prove that each FBDD computing EARn has size at least
and we present a construction of such diagrams of size approximately
. 相似文献
54.
General equations for the dynamic behavior of dirty superconductors in the Ginzburg-Landau regime T
c-T T
care derived from microscopic theory. In the immediate vicinity of T
ca local equilibrium approximation leads to a simple generalized time-dependent Ginzburg-Landau equation. The oscillatory phase-slip solutions presented previously are discussed in greater detail.Supported by the Science Research Council (England) under grant GR/A65218, and by the Deutsche Forschungsgemeinschaft. 相似文献
55.
Krüger A McAlpine P Borrani F Edelmann-Nusser J 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2012,226(2):170-175
In the biomechanical literature only a few studies are available focusing on the determination of joint loading within the lower extremities in snowboarding. These studies are limited to analysis in a restricted capture volume due to the use of optical video-based systems. To overcome this restriction the aim of the present study was to develop a method to determine net joint moments within the lower extremities in snowboarding for complete measurement runs. An experienced snowboarder performed several runs equipped with two custom-made force plates as well as a full-body inertial measurement system. A rigid, multi-segment model was developed to describe the motion and loads within the lower extremities. This model is based on an existing lower-body model and designed to be run by the OpenSim software package. Measured kinetic and kinematic data were imported into the OpenSim program and inverse dynamic calculations were performed. The results illustrate the potential of the developed method for the determination of joint loadings within the lower extremities for complete measurement runs in a real snowboarding environment. The calculated net joint moments of force are reasonable in comparison to the data presented in the literature. A good reliability of the method seems to be indicated by the low data variation between different turns. Due to the unknown accuracy of this method the application for inter-individual studies as well as studies of injury mechanisms may be limited. For intra-individual studies comparing different snowboarding techniques as well as different snowboard equipment the method seems to be beneficial. The validity of the method needs to be studied further. 相似文献
56.
Reinhard Miller Dmitri Grigoriev Jürgen Krägel Alexander V. Makievski Valentin B. Fainerman Volodymyr I. Kovalchuk Libero Liggieri Francesca Ravera Michele Ferrari Eva Santini Giuseppe Loglio Victoria Dutschk Thodoris Karapantsios 《Microgravity science and technology》2006,18(3-4):104-107
The utilisation of particle-surfactants nanostructures as stabilising agents represents today the technologic and scientific frontier in the stabilisation of liquid films in emulsion and foams. This topic will be addressed by the proposal STEFAN (STabilisation of Emulsions and FoAms by Nanoparticles), proposed by European groups in the framework of the ESA AO-2004 for Life and Physical Sciences and Applied Research projects Similarly to what can be observed for surfactant-stabilised emulsions and foams, microgravity provides ideal conditions for the investigation of the hierarchy of involved objects: interfacial layer, liquid film, dispersed systems foam or emulsion. Microgravity experiments are planned by refurbishing the Experimental Container FASES for the ISS Fluid Science Laboratory and the facility FASTER for the European Drawer Rack, already under development in existing research programmes. Here the scientific guidelines of the project are presented together with examples and preliminary results on the effect of nano-particle-surfactant structures adsorbed at liquid interfaces. First experimental results have been achieved for particle monolayers at the water/air interface and a thermodynamic model was derived to describe the obtained surface pressure-area isotherms. 相似文献
57.
Ekkehard Krüger 《Journal of Superconductivity and Novel Magnetism》2005,18(4):433-454
The symmetry of the Bloch functions in the conduction band of tetragonal and orthorhombic La2CuO4 is examined for the existence of symmetry-adapted and optimally localizable (usual or spin-dependent) Wannier functions.
It turns out that such Wannier functions do not exist in the tetragonal phase. In the orthorhombic phase, on the other hand,
the Bloch functions can be unitarily transformed in three different ways into optimally localizable Wannier functions: they
can be chosen to be adapted to each of the three phases observed in the pure or doped material, that is, to the antiferromagnetic
phase, to the superconducting phase or to the phase evincing neither magnetism nor superconductivity. This group-theoretical
result is proposed to be interpreted within a nonadiabatic extension of the Heisenberg model. Within this model, atomic-like
states represented by these Wannier functions are responsible for the stability of each of the three phases. However, all
the three atomic-like states cannot exist in the tetragonal phase, but are stabilized by the orthorhombic distortion of the
crystal. A simple model is proposed which may explain the physical properties of La2−x
Sr
x
CuO4 as a function of the Sr concentrationx. 相似文献
58.
G. Loglio P. Pandolfini R. Miller A. Makievski J. Krägel F. Ravera L. Liggieri 《Microgravity science and technology》2005,16(1-4):205-209
The experiments are aimed at the study of the interfacial dilational properties, under microgravity conditions. The examined systems are aqueous solutions of the surfactant n-dodecyl-dimethylphosphine oxide, at different concentrations and temperatures. Low frequency harmonic disturbances are imposed to the interfacial area of an air bubble. Also square pulse disturbances are imposed to each studied system. The experimental results grant information about the dynamics of air-liquid single interfaces. 相似文献
59.
Alexander V. Makievski Volodymyr I. Kovalchuk Jürgen Krägel Madine Simoncini Libero Liggieri M. Ferrari Piero Pandolfini Giuseppe Loglio Reinhard Miller 《Microgravity science and technology》2005,16(1-4):215-218
The present work shows the first experimental and theoretical results for investigations on the rheology of liquid films. The experiments are planned to be performed under microgravity conditions. This environment will allow forming films of different thickness, which is impossible under ground conditions due to drainage. Then the films are forced to harmonic oscillations of the film area so that the film elasticity can be measured as a function of frequency. The presented theoretical model demonstrates the main relationships to be solved under corresponding boundary conditions 相似文献
60.
A database model for object dynamics 总被引:1,自引:0,他引:1
M.P. Papazoglou B.J. Krämer 《The VLDB Journal The International Journal on Very Large Data Bases》1997,6(2):73-96
To effectively model complex applications in which constantly changing situations can be represented, a database system must
be able to support the runtime specification of structural and behavioral nuances for objects on an individual or group basis.
This paper introduces the role mechanism as an extension of object-oriented databases to support unanticipated behavioral
oscillations for objects that may attain many types and share a single object identity. A role refers to the ability to represent
object dynamics by seamlessly integrating idiosyncratic behavior, possibly in response to external events, with pre-existing
object behavior specified at instance creation time. In this manner, the same object can simultaneously be an instance of
different classes which symbolize the different roles that this object assumes. The role concept and its underlying linguistic
scheme simplify the design requirements of complex applications that need to create and manipulate dynamic objects.
Edited by D. McLeod / Received March 1994 / Accepted January 1996 相似文献