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111.
Andreas Opitz Bernhard Ecker Julia Wagner Alexander Hinderhofer Frank Schreiber Jochen Manara Jens Pflaum Wolfgang Brütting 《Organic Electronics》2009,10(7):1259-1267
Blends of organic electron and hole conductive materials are widely used for ambipolar charge carrier transport and photovoltaic cells. An obvious choice for donor–acceptor blends are organic semiconducting materials in their hydrogenated and fluorinated form, since they combine potentially suitable electronic properties with structural compatibility of the two constituents. This study focuses on the structural, optical, and electrical properties of blends using hydrogenated copper-phthalocyanine (H16CuPc) in combination with its per-fluorinated version (F16CuPc). Using X-ray scattering, scanning force microscopy and optical absorption measurements we show that mixed crystalline films are obtained by co-evaporation of the two materials. Electrical transport measurements reveal a profound reduction of the current for bipolar charge injection in mixed films. We discuss the formation of self-trapped charge transfer excitons as possible explanation for this unexpected behaviour, which impedes the usability of this system in photovoltaic cells. 相似文献
112.
Bredthauer Jurgen Wachta Bernhard Appleton Steve 《Industry Applications, IEEE Transactions on》1987,(3):451-463
An important role is played by the compressor in the petrochemical industry. Typical high-speed compressor drivers are turbines and induction and synchronous motors. The cylindrical-rotor synchronous motor and its application as a high-speed compressor driver is discussed. Important tasks within the production processes of the petrochemical industry include gas liquefaction, compression, refrigeration, and heat recovery. Compressor drive systems constitute important components in plants for such processes. In the past, large high-speed radial and axial compressors were driven mainly by turbines, but in recent years electric motors have been used increasingly. In addition to lower plant costs, the advantages Include high operating efficiency, low pollution, and simpler handling and maintenance. The majority of drives are operating at constant speed, using a four-or six-pole motor with stepup gear. For large ratings, synchronous motors are preferred. For these a number of specific characteristics, such as electrically excited oscillating torques during asynchronous acceleration and special cooling conditions, must be considered. The urge for optimum operating characteristics has led to the development of the synchronous motor with laminated cylindrical rotor, derived from the two-pole turbine-driven generator. The design structure, the steady-state and dynamic operating characteristics, and the starting performance during asynchronous acceleration of such synchronous drive systems are the topics covered here. The theoretical background has been excluded from the normal text and is summarized in the Appendices. 相似文献
113.
Sorantin E Halmai C Erdöhelyi B Palágyi K Nyúl LG Ollé K Geiger B Lindbichler F Friedrich G Kiesler K 《IEEE transactions on medical imaging》2002,21(3):263-273
PURPOSE: Demonstration of a technique for three-dimensional (3-D) assessment of tracheal-stenoses, regarding site, length and degree, based on spiral computed tomography (S-CT). PATIENTS AND METHODS: S-CT scanning and automated segmentation of the laryngo-tracheal tract (LTT) was followed by the extraction of the LTT medial axis using a skeletonization algorithm. Orthogonal to the medial axis the LTT 3-D cross-sectional profile was computed and presented as line charts, where degree and length was obtained. Values for both parameters were compared between 36 patients and 18 normal controls separately. Accuracy and precision was derived from 17 phantom studies. RESULTS: Average degree and length of tracheal stenoses was found to be 60.5% and 4.32 cm in patients compared with minor caliber changes of 8.8% and 2.31 cm in normal controls (p < 0.0001). For the phantoms an excellent correlation between the true and computed 3-D cross-sectional profile was found (p < 0.005) and an accuracy for length and degree measurements of 2.14 mm and 2.53% respectively could be determined. The corresponding figures for the precision were found to be 0.92 mm and 2.56%. CONCLUSION: LTT 3-D cross-sectional profiles permit objective, accurate and precise assessment of LTT caliber changes. Minor LTT caliber changes can be observed even in normals and, in case of an otherwise normal S-CT study, can be regarded as artifacts. 相似文献
114.
Application of the Tauc-Lorentz formulation to the interband absorption of optical coating materials
Recent progress in ellipsometry instrumentation permits precise measurement and characterization of optical coating materials in the deep-UV wavelength range. Dielectric coating materials exhibit their first electronic interband transition in this spectral range. The Tauc-Lorentz model is a powerful tool with which to parameterize interband absorption above the band edge. The application of this model for the parameterization of the optical absorption of TiO2, Ta2O5, HfO2, Al2O3, and LaF3 thin-film materials is described. 相似文献
115.
116.
Modal Kleene algebras are Kleene algebras enriched by forward and backward box and diamond operators. We formalise the symmetries of these operators as Galois connections, complementarities and dualities. We study their properties in the associated operator algebras and show that the axioms of relation algebra are theorems at the operator level. Modal Kleene algebras provide a unifying semantics for various program calculi and enhance efficient cross-theory reasoning in this class, often in a very concise pointfree style. This claim is supported by novel algebraic soundness and completeness proofs for Hoare logic and by connecting this formalism with an algebraic decision procedure. 相似文献
117.
Domain specific modeling 总被引:1,自引:0,他引:1
118.
Assume a partially ordered set (S, ≤) and a relation R on S. We consider various sets of conditions in order to determine whether they ensure the existence of a least reflexive point, that is, a least x such that xRx. This is a generalization of the problem of determining the least fixed point of a function and the conditions under which it exists. To motivate the investigation we first present a theorem by Cai and Paige giving conditions under which iterating R from the bottom element necessarily leads to a minimal reflexive point; the proof is by a concise relation-algebraic calculation. Then, we assume a complete lattice and exhibit sufficient conditions, depending on whether R is partial or not, for the existence of a least reflexive point. Further results concern the structure of the set of all reflexive points; among other results we give a sufficient condition that these form a complete lattice, thus generalizing Tarski’s classical result to the nondeterministic case.This research is supported by a grant from NSERC (Natural Sciences and Engineering Research Council of Canada). 相似文献
119.
Christian Feddern Joachim Weickert Bernhard Burgeth Martin Welk 《International Journal of Computer Vision》2006,69(1):93-107
Matrix-valued data sets arise in a number of applications including diffusion tensor magnetic resonance imaging (DT-MRI) and
physical measurements of anisotropic behaviour. Consequently, there arises the need to filter and segment such tensor fields.
In order to detect edge-like structures in tensor fields, we first generalise Di Zenzo’s concept of a structure tensor for
vector-valued images to tensor-valued data. This structure tensor allows us to extend scalar-valued mean curvature motion
and self-snakes to the tensor setting. We present both two-dimensional and three-dimensional formulations, and we prove that
these filters maintain positive semidefiniteness if the initial matrix data are positive semidefinite. We give an interpretation
of tensorial mean curvature motion as a process for which the corresponding curve evolution of each generalised level line
is the gradient descent of its total length. Moreover, we propose a geodesic active contour model for segmenting tensor fields
and interpret it as a minimiser of a suitable energy functional with a metric induced by the tensor image. Since tensorial
active contours incorporate information from all channels, they give a contour representation that is highly robust under
noise. Experiments on three-dimensional DT-MRI data and an indefinite tensor field from fluid dynamics show that the proposed
methods inherit the essential properties of their scalar-valued counterparts. 相似文献
120.
Jürgen Mäurer Herman Requardt Bernhard Sander Friedrich D. Knollmann Arne-jörn Lemke Thomas J. Vogl Roland Felix 《Magma (New York, N.Y.)》1996,4(1):27-33
To investigate the application of a mini-coil surface system for high-resolution MRI, 60 volunteers were examined in a 1.5-T whole-body scanner. Two replaceable probe heads were available: a circular 2.5-cm coil and a quadratic 5-cm coil, both of which were placed directly on the skin. The skin layers, Achilles tendon and finger joints were examined with the 2.5-cm coil and a FOV of 25 × 25 mm2. A matrix of 256 × 256 pixels resulted in a pixel size of 0.098 × 0.098 mm2. For imaging of the carpal tunnel, the 5-cm coil was used in transverse orientation. The FOV was 50 × 50 mm2 so that a matrix of 256 × 256 pixels led to a pixel size of 0.195 × 0.195 mm2. The resulting spatial resolution permitted visualization of the epidermis, dermis and subcutis, resulting in clear definition of anatomical detail of the musculoskeletal system. MRI measurement of skin-layer thickness did not correlate with histometric data (p<0.05). This discrepancy was due in part to shrinkage of the tumor specimen on histologic preparation. Other causes include the motion artifacts and the limited accuracy of determining thickness on the MRI display unit. 相似文献