全文获取类型
收费全文 | 11431篇 |
免费 | 1142篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 90篇 |
综合类 | 6篇 |
化学工业 | 2900篇 |
金属工艺 | 143篇 |
机械仪表 | 358篇 |
建筑科学 | 526篇 |
矿业工程 | 31篇 |
能源动力 | 260篇 |
轻工业 | 2281篇 |
水利工程 | 85篇 |
石油天然气 | 21篇 |
无线电 | 845篇 |
一般工业技术 | 2262篇 |
冶金工业 | 728篇 |
原子能技术 | 36篇 |
自动化技术 | 2015篇 |
出版年
2024年 | 32篇 |
2023年 | 166篇 |
2022年 | 149篇 |
2021年 | 395篇 |
2020年 | 329篇 |
2019年 | 320篇 |
2018年 | 460篇 |
2017年 | 473篇 |
2016年 | 583篇 |
2015年 | 505篇 |
2014年 | 633篇 |
2013年 | 1168篇 |
2012年 | 1018篇 |
2011年 | 819篇 |
2010年 | 600篇 |
2009年 | 575篇 |
2008年 | 627篇 |
2007年 | 538篇 |
2006年 | 475篇 |
2005年 | 319篇 |
2004年 | 285篇 |
2003年 | 263篇 |
2002年 | 256篇 |
2001年 | 153篇 |
2000年 | 126篇 |
1999年 | 116篇 |
1998年 | 161篇 |
1997年 | 132篇 |
1996年 | 96篇 |
1995年 | 94篇 |
1994年 | 84篇 |
1993年 | 75篇 |
1992年 | 49篇 |
1991年 | 35篇 |
1990年 | 25篇 |
1989年 | 27篇 |
1988年 | 31篇 |
1987年 | 23篇 |
1986年 | 27篇 |
1985年 | 37篇 |
1984年 | 31篇 |
1983年 | 21篇 |
1982年 | 28篇 |
1981年 | 21篇 |
1980年 | 20篇 |
1979年 | 23篇 |
1978年 | 12篇 |
1976年 | 17篇 |
1974年 | 12篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 459 毫秒
941.
Edgar Chávez José L. Marroquín Gonzalo Navarro 《Multimedia Tools and Applications》2001,14(2):113-135
Pivot-based algorithms are effective tools for proximity searching in metric spaces. They allow trading space overhead for number of distance evaluations performed at query time. With additional search structures (that pose extra space overhead) they can also reduce the amount of side computations. We introduce a new data structure, the Fixed Queries Array (FQA), whose novelties are (1) it permits sublinear extra CPU time without any extra data structure; (2) it permits trading number of pivots for their precision so as to make better use of the available memory. We show experimentally that the FQA is an efficient tool to search in metric spaces and that it compares favorably against other state of the art approaches. Its simplicity converts it into a simple yet effective tool for practitioners seeking for a black-box method to plug in their applications. 相似文献
942.
Esther Perales Francisco M. Martínez‐Verdú Valentín Viqueira Jesús Fernández‐Reche José A. Díaz Joan Uroz 《Color research and application》2009,34(4):330-336
In this work, we have studied the relationship among the colorimetric properties of different types of paper, having different finishing and grammage. Their color reproduction capability has also been analyzed by using the same printing technology (inkjet printing). On the one hand, we have plotted CIELAB data under the illuminant D50 into constant lightness and hue‐angle planes to be compared with MacAdam limits and with Pointer's real‐world surface color. On the other hand, we have calculated the volume gamut of the color solid associated to each color paper gamut. Analyzing the results, we have checked that there is not any clear relationship among the colorimetric properties of paper (for instance, CIE whiteness index, etc.) and the color gamut volume associated. However, the colorimetric parameters associated to the printed sample showed a quite good linear correlation between the minimum lightness (or the maximum blackness value) of the printed color chart and the color gamut volume. In particular, the greatest color gamut volume corresponds to the glossy papers taking into account this correlation for inkjet printing. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 330–336, 2009 相似文献
943.
José Herskovits Mario Tanaka Filho Anatoli Leontiev 《Optimization and Engineering》2013,14(3):381-394
This paper deals with bilevel programs with strictly convex lower level problems. We present the theoretical basis of a kind of necessary and sufficient optimality conditions that involve a single-level mathematical program satisfying the linear independence constraint qualification. These conditions are obtained by replacing the inner problem by their optimality conditions and relaxing their inequality constraints. An algorithm for the bilevel program, based on a well known technique for classical smooth constrained optimization, is also studied. The algorithm obtains a solution of this problem with an effort similar to that required by a classical well-behaved nonlinear constrained optimization problem. Several illustrative problems which include linear, quadratic and general nonlinear functions and constraints are solved, and very good results are obtained for all cases. 相似文献
944.
Multi-objective optimization of steam power plants for sustainable generation of electricity 总被引:1,自引:1,他引:0
César G. Gutiérrez-Arriaga Medardo Serna-González José María Ponce-Ortega Mahmoud M. El-Halwagi 《Clean Technologies and Environmental Policy》2013,15(4):551-566
A unified framework that combines process simulation and multi-objective optimization is presented to simultaneously maximize the annual profit, while minimizing environmental impact (i.e., greenhouse gas emissions) of steam power plants with fixed flowsheet structures. The proposed methodology includes the selection of suitable primary energy sources (i.e., fossil fuels, biomass, biofuels, and solar energy) for sustainable electricity generation. For solving the problem of optimal selection of energy sources, a linear model is developed and included within a highly nonlinear simulation model for the parameter optimization of steam power plants that is solved by using genetic algorithms. This approach is robust and avoids making discrete decisions. Life cycle assessment technique is used to quantify the greenhouse gas emissions resulting from different combinations of energy sources and operating conditions of the power plants. The thermodynamic properties for liquid water and steam are calculated rigorously using the IAPWS-IF 97 formulation. An example problem of an advanced regenerative-reheat steam power plant is presented to illustrate the proposed method, which provides the Pareto optimal solutions, the types and amounts of primary energy sources as well as the optimal values of the operating conditions of the plant that simultaneously maximize the profit while minimizing environmental impact. 相似文献
945.
René Y. Darmon 《OR Spectrum》2000,22(1):35-58
Past theoretical sales force compensation research has typically applied paradigms from economic theory in order to derive optimal decentralized control schemes. This research stream has generally neglected the important equity aspect of sales force compensation plans which is recognized in the professional literature. This paper shows how equity theory provides a valuable paradigm for analyzing this problem within a centralized sales force control framework. Its purposes are to provide guidelines to sales managers for determining short-term remuneration levels and sales objectives for a heterogeneous sales force through application of equity theory, and to propose a few normative implications for sales force equitable compensation. 相似文献
946.
947.
André Pohlmann Marc Leßmann Andreas Fritschi Thomas Finocchiaro Ulrich Steinseifer Kay Hameyer 《Mechatronics》2013,23(2):222-226
In industrialized countries cardiovascular diseases are the major cause of death. Beside heart transplants, which are a limited option due to the limited number of available human donor hearts, Total Artificial Hearts (TAHs) are the only therapy available for some patients with terminal heart diseases. For various reasons a total implantable artificial heart is desirable, but also sets restrictions in terms of weight and dimensions due to the limited space in the human thorax. Therefore a precise requirement profile is needed for the drive design to provide sufficient force for the blood pump and to avoid oversizing of the drive and to prevent blood damage by overheating. 相似文献
948.
Thulium and Ytterbium-Doped Titanium Oxide Thin Films Deposited by Ultrasonic Spray Pyrolysis 总被引:1,自引:0,他引:1
Sébastien Forissier Hervé Roussel Patrick Chaudouet Antonio Pereira Jean-Luc Deschanvres Bernard Moine 《Journal of Thermal Spray Technology》2012,21(6):1263-1268
Thin films of thulium and ytterbium-doped titanium oxide were grown by metal-organic spray pyrolysis deposition from titanium(IV)oxide bis(acetylacetonate), thulium(III) tris(2,2,6,6-tetramethyl-3,5-heptanedionate) and ytterbium(III) tris(acetylacetonate). Deposition temperatures have been investigated from 300 to 600 °C. Films have been studied regarding their crystallinity and doping quality. Structural and composition characterisations of TiO2:Tm,Yb were performed by electron microprobe, x-ray diffraction, and Fourier transform infrared spectroscopy. The deposition rate can reach 0.8 μm/h. The anatase phase of TiO2 was obtained after synthesis at 400 °C or higher. Organic contamination at low deposition temperature is eliminated by annealing treatments. 相似文献
949.
Matthias Augustin Alfonso Caiazzo André Fiebach Jürgen Fuhrmann Volker John Alexander Linke Rudolf Umla 《Computer Methods in Applied Mechanics and Engineering》2011,200(47-48):3395-3409
The performance of several numerical schemes for discretizing convection-dominated convection–diffusion equations will be investigated with respect to accuracy and efficiency. Accuracy is considered in measures which are of interest in applications. The study includes an exponentially fitted finite volume scheme, the Streamline-Upwind Petrov–Galerkin (SUPG) finite element method, a spurious oscillations at layers diminishing (SOLD) finite element method, a finite element method with continuous interior penalty (CIP) stabilization, a discontinuous Galerkin (DG) finite element method, and a total variation diminishing finite element method (FEMTVD). A detailed assessment of the schemes based on the Hemker example will be presented. 相似文献
950.