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排序方式: 共有2084条查询结果,搜索用时 218 毫秒
61.
K. Ramesh W. G. Lewis S. C. Veldhuis A. Yui 《Materials and Manufacturing Processes》2005,20(6):895-903
Ongoing developments in broadband digital networks and optical devices require mechanical components having nano-metric surface finishes and ultra precision shapes. Such components are processed using the technology of diamond micro-machining in which diamond tools are extensively used. However, these tools are susceptible to chemical attack at high temperatures and induce severe wear, especially when cutting ferrous materials. As a result, these diamond tools need to be redefined (i.e., resharpened) on a regular basis in order to facilitate micro-cutting and to generate nano-metric surface finishes. This paper describes a new way of diamond tool edge re-sharpening and its conditions to achieve both increased accuracy and material removal rate. 相似文献
62.
Laser composite surfacing of AISI 304 stainless steel with titanium boride for improved wear resistance 总被引:2,自引:0,他引:2
The present study concerns development of a hard in situ boride-dispersed composite layer on the surface of AISI 304 stainless steel substrate to improve the wear resistance property. Laser processing was carried out by melting the surface of sand-blasted AISI 304 stainless steel substrate using a continuous wave CO2 laser and simultaneous deposition of a mixture of K2TiF6 (potassium titanium hexafluoride) and KBF6 (potassium hexafloroborate) (in the weight ratio of 2:1) using Ar as shrouding environment. Powder feed rate was maintained constant at 4 g/min. Irradiation results in dissociation of a pre-deposited mixture along with a part of the stainless steel substrate, intermixing and rapid solidification to form the composite layer on the surface. The micro-structure of composite layer consists of dispersion of titanium boride particles in AISI 304 stainless steel matrix. Volume fraction of particles is found to be uniform throughout the composite layer, though varied with laser parameters. The micro-hardness of the surface was improved 250–350 VHN as compared to 220 VHN of the AISI 304 stainless steel substrate with a significant improvement in wear resistance property. The mechanism of wear was found to be a combination of adhesive and abrasive in as-received stainless steel. However, it was predominantly abrasive for laser composite surfaced stainless steel. 相似文献
63.
Hildrun Kretschmer Ramesh Kundra Donald deB. Beaver Theo Kretschmer 《Scientometrics》2012,93(1):135-150
The causes of gender bias favoring men in scientific and scholarly systems are complex and related to overall gender relationships in most of the countries of the world. An as yet unanswered question is whether in research publication gender bias is equally distributed over scientific disciplines and fields or if that bias reflects a closer relation to the subject matter. We expected less gender bias with respect to subject matter, and so analysed 14 journals of gender studies using several methods and indicators. The results confirm our expectation: the very high position of women in co-operation is striking; female scientists are relatively overrepresented as first authors in articles. Collaboration behaviour in gender studies differs from that of authors in PNAS. The pattern of gender studies reflects associations between authors of different productivity, or ??masters?? and ??apprentices?? but the PNAS pattern reflects associations between authors of roughly the same productivity, or ??peers??. It would be interesting to extend the analysis of these three-dimensional collaboration patterns further, to see whether a similar characterization holds, what it might imply about the patterns of authorship in different areas, what those patterns might imply about the role of collaboration, and whether there are differences between females and males in collaboration patterns. 相似文献
64.
65.
Ramesh M. Gohil 《应用聚合物科学杂志》2012,126(1):260-272
We have studied the efficiencies of commercially available barrier resins used for food packaging and beverage bottle applications and compared them with resins made using copolymer and blending approaches. The effects of various copolymer related parameters that influence oxygen barrier performance and the underlying mechanisms for these effects in PET‐based copolymers and blends were investigated. Using these approaches, it is possible to make highly effective PET‐based copolymers for gas barrier applications. Blending of PET with phenolic and other organic materials shows equivalent barrier performance in PET copolymers having comonomer levels of <8‐mole %. Reduction in oxygen permeation rates results from the reduction or elimination of short range molecular motion of polyethylene terephthalate molecules. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
66.
Achuta Kadambi Vage Taamazyan Boxin Shi Ramesh Raskar 《International Journal of Computer Vision》2017,125(1-3):34-51
Analyzing the polarimetric properties of reflected light is a potential source of shape information. However, it is well-known that polarimetric information contains fundamental shape ambiguities, leading to an underconstrained problem of recovering 3D geometry. To address this problem, we use additional geometric information, from coarse depth maps, to constrain the shape information from polarization cues. Our main contribution is a framework that combines surface normals from polarization (hereafter polarization normals) with an aligned depth map. The additional geometric constraints are used to mitigate physics-based artifacts, such as azimuthal ambiguity, refractive distortion and fronto-parallel signal degradation. We believe our work may have practical implications for optical engineering, demonstrating a new option for state-of-the-art 3D reconstruction. 相似文献
67.
68.
Ashoka Bali Il-Ho Kim Peter Rogl Ramesh Chandra Mallik 《Journal of Electronic Materials》2014,43(6):1630-1638
The thermoelectric figure of merit (zT) can be increased by introduction of additional interfaces in the bulk to reduce the thermal conductivity. In this work, PbTe with a dispersed indium (In) phase was synthesized by a matrix encapsulation technique for different In concentrations. x-Ray diffraction analysis showed single-phase PbTe with In secondary phase. Rietveld analysis did not show In substitution at either the Pb or Te site, and this was further confirmed by room-temperature Raman data. Low-magnification (~1500×) scanning electron microscopy images showed micrometer-sized In dispersed throughout the PbTe matrix, while at high magnification (150,000×) an agglomeration of PbTe particles in the hot-pressed samples could be seen. The electrical resistivity (ρ) and Seebeck coefficient (S) were measured from 300 K to 723 K. Negative Seebeck values showed all the samples to be n-type. A systematic increase in resistivity and higher Seebeck coefficient values with increasing In content indicated the role of PbTe-In interfaces in the scattering of electrons. This was further confirmed by the thermal conductivity (κ), measured from 423 K to 723 K, where a greater reduction in the electronic as compared with the lattice contribution was found for In-added samples. It was found that, despite the high lattice mismatch at the PbTe-In interface, phonons were not scattered as effectively as electrons. The highest zT obtained was 0.78 at 723 K for the sample with the lowest In content. 相似文献
69.
Dan Raviv Eduardo Bayro-Corrochano Ramesh Raskar 《International Journal of Computer Vision》2017,124(2):132-144
We present a novel algorithm for generating the mean structure of non-rigid stretchable shapes. Following an alignment process, which supports local affine deformations, we translate the search of the mean shape into a diagonalization problem where the structure is hidden within the kernel of a matrix. This is the first step required in many practical applications, where one needs to model bendable and stretchable shapes from multiple observations. 相似文献
70.
The design of a complex embedded control system involves integration of large number of components. These components need to interact in a timely fashion to achieve the system level end-to-end requirements. In practice, the component level timing specification consists of design attributes like component task mapping, task period and schedule definition but often lack details on their real-time (functional) requirements. As we observe, there is no systematic methodology in place for decomposing the feature level timing requirements into component level timing requirements. This paper proposes an early stage time-budgeting methodology to bridge the above gap. A salient proposal of this methodology is to consider parameterized component timing-requirements. A key step in the methodology involves computing a set of constraints by relating component requirements with feature requirements. This enables the separation of timing constraints from functionality decomposition, and facilitates early optimization of the component time-budget for a complex component based embedded system. This paper formalizes the proposed methodology by using Parametric Temporal Logic. A case study involving two advanced features from the automotive domain, namely Adaptive Cruise Control and Collision Mitigation is given to demonstrate the methodology. 相似文献