全文获取类型
收费全文 | 1516篇 |
免费 | 30篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 254篇 |
金属工艺 | 90篇 |
机械仪表 | 59篇 |
建筑科学 | 27篇 |
矿业工程 | 35篇 |
能源动力 | 19篇 |
轻工业 | 122篇 |
水利工程 | 90篇 |
石油天然气 | 230篇 |
无线电 | 60篇 |
一般工业技术 | 298篇 |
冶金工业 | 89篇 |
原子能技术 | 33篇 |
自动化技术 | 128篇 |
出版年
2018年 | 14篇 |
2017年 | 21篇 |
2016年 | 28篇 |
2013年 | 146篇 |
2012年 | 41篇 |
2011年 | 49篇 |
2010年 | 30篇 |
2009年 | 14篇 |
2008年 | 22篇 |
2007年 | 14篇 |
2006年 | 15篇 |
2003年 | 13篇 |
2002年 | 13篇 |
2001年 | 19篇 |
2000年 | 19篇 |
1999年 | 19篇 |
1998年 | 26篇 |
1997年 | 21篇 |
1994年 | 16篇 |
1993年 | 22篇 |
1992年 | 17篇 |
1991年 | 33篇 |
1990年 | 28篇 |
1989年 | 28篇 |
1988年 | 29篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 27篇 |
1984年 | 38篇 |
1983年 | 13篇 |
1982年 | 20篇 |
1981年 | 28篇 |
1980年 | 35篇 |
1979年 | 36篇 |
1978年 | 44篇 |
1977年 | 41篇 |
1976年 | 35篇 |
1975年 | 47篇 |
1974年 | 50篇 |
1973年 | 38篇 |
1972年 | 28篇 |
1971年 | 28篇 |
1970年 | 34篇 |
1969年 | 29篇 |
1968年 | 23篇 |
1967年 | 20篇 |
1966年 | 17篇 |
1965年 | 19篇 |
1964年 | 14篇 |
1963年 | 12篇 |
排序方式: 共有1547条查询结果,搜索用时 31 毫秒
21.
Françoise Détienne Béatrice Cahour Marie-Christine Legout Bernard Gourvennec Marc Relieu Gilles Coppin 《Cognition, Technology & Work》2013,15(4):445-455
Based on the analysis of “real” Second Life meetings data, in educational and professional settings, our objective is to understand the actual uses of this kind of Virtual World and more particularly, the interactive frames constructed in SL meetings and their interrelation with uses of communication media. The originality of our analytical framework stems from the combination of two perspectives: a third view perspective based on analyses of observational data and a first view perspective based on users’ reports on their experience in SL. Our results highlight: boundaries between serious and recreational registers; avatar’s expression and attribution of feelings to the person “behind”; spatial positioning as indicators and constructors of roles and engagement; management of communication fluidity and joint focus; narrowing of communication media used for task focus content; emerging mediation role for management of fractured exchanges. 相似文献
22.
In this paper, we present a method for binary image comparison. For binary images, intensity information is poor and shape extraction is often difficult. Therefore binary images have to be compared without using feature extraction. Due to the fact that different scene patterns can be present in the images, we propose a modified Hausdorff distance (HD) locally measured in an adaptive way. The resulting set of measures is richer than a single global measure. The local HD measures result in a local-dissimilarity map (LDMap) including the dissimilarity spatial layout. A classification of the images in function of their similarity is carried out on the LDMaps using a support vector machine. The proposed method is tested on a medieval illustration database and compared with other methods to show its efficiency. 相似文献
23.
Patrice Le Boudec François Sanchez Pierre-Luc FranÇois Jean-François Bayon Guy Michel StÉphan 《电信纪事》1994,49(3-4):178-192
The dynamics of the erbium doped fiber laser is analysed both experimentally and theoretically. This laser operates spontaneously in self-pulsing, in sinusoidal or in CW regime. Experiments have allowed to determine the control parameters : the cavity losses, the pumping rate and the ion pairs concentration. An antiphase dynamics is observed when the laser operates simultaneously at 1.55 µn and 1.536 µm. The self-pulsing behavior is attributed to a fast energy transfer which occurs between two neighboring ions (pair induced quenching). A simple model considering the active medium as a mixture of isolated ions and ions pairs is developped and leads to a good qualitative agreement with the experimental results. 相似文献
24.
Étude O'Neel‐Judy Dylan Nicholls John Castañeda John G. Gibbs 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(32)
Using a dynamic fabrication process, hybrid, photoactivated microswimmers made from two different semiconductors, titanium dioxide (TiO2) and cuprous oxide (Cu2O) are developed, where each material occupies a distinct portion of the multiconstituent particles. Structured light‐activated microswimmers made from only TiO2 or Cu2O are observed to be driven in hydrogen peroxide and water most vigorously under UV or blue light, respectively, whereas hybrid structures made from both of these materials exhibit wavelength‐dependent modes of motion due to the disparate responses of each photocatalyst. It is also found that the hybrid particles are activated in water alone, a behavior which is not observed in those made from a single semiconductor, and thus, the system may open up a new class of fuel‐free photoactive colloids that take advantage of semiconductor heterojunctions. The TiO2/Cu2O hybrid microswimmer presented here is but an example of a broader method for inducing different modes of motion in a single light‐activated particle, which is not limited to the specific geometries and materials presented in this study. 相似文献
25.
Kalashnyk Nataliya Ledieu Julian Gaudry Émilie Cui Can Tsai An-Pang Fournée Vincent 《Nano Research》2018,11(4):2129-2138
Nano Research - The formation of long-range ordered aperiodic molecular films on quasicrystalline substrates is a new challenge that provides an opportunity for further surface functionalization.... 相似文献
26.
Éric Lunaud Ngoupé Clément Parisot Sylvan Stoesel Petko Valtchev Roger Villemaire Omar Cherkaoui Pierre Boucher Sylvain Hallé 《Journal of Network and Systems Management》2017,25(1):180-209
Configuration Logic (CL) is a formal language that allows a network engineer to express constraints in terms of the actual parameters found in the configuration of network devices. We present an efficient algorithm that can automatically check a pool of devices for conformance to a set of CL constraints; moreover, this algorithm can point to the part of the configuration responsible for the error when a constraint is violated. Contrary to other validation approaches that require dumping the configuration of the whole network to a central location in order to be verified, we also present an algorithm that analyzes the correct formulas and greatly helps reduce the amount of data that need to be transferred to that central location, pushing as much of the evaluation of the formula locally on each device. The procedure is also backwards-compatible, in such a way that a device that does not (or only partially) supports a local evaluation may simply return a subset or all of its configuration. These capabilities have been integrated into a network management tool called ValidMaker. 相似文献
27.
V. B. Érenberg V. N. Pokrovskii 《Journal of Engineering Physics and Thermophysics》1981,41(3):966-971
Solutions of a system of equations of nonlinear viscoelastic fluid motion describing inhomogeneous shear flows of linear polymers are indicated.Notation ij
stress tensor
- p
pressure
- Fi
mass force vector
- ij
Kronecker delta
-
coefficient of shear viscosity
-
relaxation time
- ij
inner parameter
- ij=vi/xj
velocity gradient tensor
- 0
initial value of the shear viscosity coefficient
- 0
initial value of the relaxation time
- D
dimensionless first invariant of the additional stress tensor
- A, B, C
constants of integration
- f(D)
universal function characterizing the material
- r, , z
cylindrical coordinates
- u=vz
axial component of the velocity vector
- v=v
circumferential component of the velocity vector
- 1, 2
first and second differences of the normal stress
- Q
volume mass flow rate
- R
radius of a circular tube
- R1, R2
radii of the inner and outer cylinders, respectively
- M
moment per unit length
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 3, pp. 449–456, September, 1981. 相似文献
28.
L. V. Kuksa B. I. Koval'chuk A. A. Lebedev V. I. Él'manovich 《Strength of Materials》1976,8(6):678-682
1. | The use of the method developed for determining the main deformations of microvolumes makes it possible to investigate peculiarities of metal deformation in microareas and the actual level of micrononuniform deformation, taking into consideration the form of stressed condition |
2. | A definite character of distribution of the main deformations across microareas, reflecting not only the influence of the form of stressed condition of the macrovolume of a sample, but also the peculiarities of interaction of individual microvolumes which are found in stress deformed conditions differing from the stress deformed condition of the individual body, corresponds to each form of stressed condition. For complex loading a change in the form of distributions of deformations in changing from one form of loading to another is characteristic. |
3. | In the plane stressed condition under conditions of simple and complex loading there is intense slip formation accompanied by activation of a larger number of slip systems than in uniaxial loading, which is an indication of the more complex deformation conditions of individual microvolumes. |
4. | Differences in the distribution of main deformations across microareas, nonuniformity of the stress deformed conditions of microvolumes, and peculiarities of the character of slip formation undoubtedly play a major role in the formation of mechanical properties in the given forms of stressed condition and methods of complex loading. |
29.
tienne Fortin Jean-Franois Chatelain Louis Rivest 《Computers & Industrial Engineering》2004,46(4):655-667
Over the years, machine tool evolution has allowed faster equipment, using new configurations, to manufacture parts that were almost impossible to machine in the past. Despite this tremendous evolution in machine and control technologies, the metalworking industry is still using the old ISO 6983 G-Codes programming interface to control the motion of these machines. This programming interface is not the most flexible or most appropriate for use by new open-architecture machine controllers and object-oriented high-level machining interfaces such as ISO 14649 (STEP-NC). This work proposes an innovative language, the ‘Base Numerical Control Language (BNCL),’ which is based on a low-level simple instruction set-like approach. The architecture is designed around two concepts: the BNCL virtual machine, which acts as a virtual microprocessor, and the BNCL virtual hardware, which is an abstraction of the machine tool. The language is characterised by its simplicity and flexibility, two qualities that are critical in a market in which the capabilities and performance of machines are constantly improving. The proposed architectural concepts are validated through various computer simulation and physical tests, including performance throughput, trajectory driving, and CNC controller extension capabilities. 相似文献
30.
Diguer Louis; Pelletier Sylvie; Hébert étienne; Desc?teaux Jean; Rousseau Jean-Pierre; Daoust Jean-Philippe 《Canadian Metallurgical Quarterly》2004,21(2):259
This study examined the hypothesis that psychotic, borderline, and neurotic personality organizations (POs) present a progressive differentiation between self and object representations and an increasing integration of their bad and good aspects. Fifty patients participated in the study. Measures included scales of self and object representations (S. J. Blatt, S. A. Bers, & C. E. Schaffer, 1993; S. J. Blatt, H. Wiseman, E. Prince-Gibson, & C. Gatt, 1991), as well as the Personality Organization Diagnostic Form (L. Diguer & L. Normandin, 1997) and estimations of psychiatric severity. Results showed that PO groups differed in terms of the integration of the object and its valence. It was also observed that although object and self representations were closely intertwined, the latter showed more discrimination between POs than the former. Psychiatric severity was shown to correlate more with object representations than self representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献