全文获取类型
收费全文 | 4930篇 |
免费 | 152篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 61篇 |
综合类 | 6篇 |
化学工业 | 715篇 |
金属工艺 | 112篇 |
机械仪表 | 109篇 |
建筑科学 | 270篇 |
矿业工程 | 8篇 |
能源动力 | 178篇 |
轻工业 | 357篇 |
水利工程 | 21篇 |
石油天然气 | 10篇 |
武器工业 | 1篇 |
无线电 | 423篇 |
一般工业技术 | 838篇 |
冶金工业 | 1261篇 |
原子能技术 | 69篇 |
自动化技术 | 648篇 |
出版年
2023年 | 26篇 |
2022年 | 49篇 |
2021年 | 94篇 |
2020年 | 63篇 |
2019年 | 76篇 |
2018年 | 78篇 |
2017年 | 72篇 |
2016年 | 96篇 |
2015年 | 82篇 |
2014年 | 120篇 |
2013年 | 191篇 |
2012年 | 187篇 |
2011年 | 231篇 |
2010年 | 177篇 |
2009年 | 173篇 |
2008年 | 175篇 |
2007年 | 188篇 |
2006年 | 135篇 |
2005年 | 131篇 |
2004年 | 131篇 |
2003年 | 108篇 |
2002年 | 109篇 |
2001年 | 103篇 |
2000年 | 77篇 |
1999年 | 114篇 |
1998年 | 338篇 |
1997年 | 249篇 |
1996年 | 173篇 |
1995年 | 121篇 |
1994年 | 100篇 |
1993年 | 107篇 |
1992年 | 65篇 |
1991年 | 53篇 |
1990年 | 61篇 |
1989年 | 42篇 |
1988年 | 63篇 |
1987年 | 46篇 |
1986年 | 40篇 |
1985年 | 62篇 |
1984年 | 37篇 |
1983年 | 44篇 |
1982年 | 32篇 |
1981年 | 35篇 |
1980年 | 35篇 |
1979年 | 32篇 |
1978年 | 34篇 |
1977年 | 50篇 |
1976年 | 90篇 |
1974年 | 27篇 |
1973年 | 29篇 |
排序方式: 共有5087条查询结果,搜索用时 15 毫秒
81.
Higher‐order finite element methods have emerged as an important discretization scheme for simulation. They are increasingly used in contemporary numerical solvers, generating a new class of data that must be analyzed by scientists and engineers. Currently available visualization tools for this type of data are either batch oriented or limited to certain cell types and polynomial degrees. Other approaches approximate higher‐order data by resampling resulting in trade‐offs in interactivity and quality. To overcome these limitations, we have developed a distributed visualization system which allows for interactive exploration of non‐conforming unstructured grids, resulting from space‐time discontinuous Galerkin simulations, in which each cell has its own higher‐order polynomial solution. Our system employs GPU‐based raycasting for direct volume rendering of complex grids which feature non‐convex, curvilinear cells with varying polynomial degree. Frequency‐based adaptive sampling accounts for the high variations along rays. For distribution across a GPU cluster, the initial object‐space partitioning is determined by cell characteristics like the polynomial degree and is adapted at runtime by a load balancing mechanism. The performance and utility of our system is evaluated for different aeroacoustic simulations involving the propagation of shock fronts. 相似文献
82.
It is an open problem in the area of effective (algorithmic) randomness whether Kolmogorov-Loveland randomness coincides with Martin-Löf randomness. Joe Miller and André Nies suggested some variations of Kolmogorov-Loveland randomness to approach this problem and to provide a partial solution. We show that their proposed notion of injective randomness is still weaker than Martin-Löf randomness. Since in this proof some of the ideas we use are clearer, we also show the weaker theorem that permutation randomness is weaker than Martin-Löf randomness. 相似文献
83.
Can an electronic portfolio that is both a multimedia container for student work and a tool to support key learning processes have a positive impact on the literacy practices and self-regulated learning skills of students? This article presents the findings of a yearlong study conducted in three Canadian provinces during the 2007–2008 school year initially involving 32 teachers and 388 students. Due to varying levels of implementation our final data set included 14 teachers and 296 students. Using a non-equivalent pre-test/post-test design, we found that grade 4–6 students who were in classrooms where the teacher provided regular and appropriate use of the electronic portfolio tool ePEARL (i.e., medium–high implementation condition, n = 7 classrooms and 121 students), compared to control students (n = 7 classrooms and 175 students) who did not use ePEARL, showed significant improvements (p < .05) in their writing skills on a standardized literacy measure (i.e., the constructed response subtest of the Canadian Achievement Test-4th ed.) and certain metacognitive skills measured via student self-report. The results of this study indicate that teaching with ePEARL has positive impacts on students’ literacy and self-regulated learning skills when the tool is used regularly and integrated into classroom instruction. 相似文献
84.
Ahmed Fadl Zongqin Zhang Sebastian Geller Jonas Tölke Manfred Krafczyk Donna Meyer 《Microsystem Technologies》2009,15(9):1379-1387
The efficiency of the valve-less rectification micropump depends primarily on the microfluidic diodicity (the ratio of the
backward pressure drop to the forward pressure drop). In this study, different rectifying structures, including the conventional
structures (nozzle/diffuser and Tesla structures), were investigated at very low Reynolds numbers (between 0.2 and 60). The
rectifying structures were characterized with respect to their design, and a numerical approach was illustrated to calculate
the diodicity for the rectifying structures. In this study, the microfluidic diodicity was evaluated numerically for different
rectifying structures including half circle, semicircle, heart, triangle, bifurcation, nozzle/diffuser, and Tesla structures.
The Lattice Boltzmann Method (LBM) was utilized as a numerical method to simulate the fluid flow in the microscale. The results
suggest that at very low Reynolds number flow, rectification and multifunction micropumping may be achievable by using a number
of the presented structures. The results for the conventional structures agree with the reported results. 相似文献
85.
Model checking is a formal technique used to verify communication protocols against given properties. In this paper, we propose a new model checking algorithm aims at verifying systems designed as a set of autonomous interacting agents. These software agents are equipped with knowledge and beliefs and interact with each other according to protocols governed by a set of logical rules. We present a tableauased version of this algorithm and provide the soundness, completeness, termination and complexity results. A case study about an agent-based negotiation protocol and its implementation are also described. 相似文献
86.
The field of cyber security is faced with ever‐expanding amounts of data and a constant barrage of cyber attacks. Within this space, we have designed BubbleNet as a cyber security dashboard to help network analysts identify and summarize patterns within the data. This design study faced a range of interesting constraints from limited time with various expert users and working with users beyond the network analyst, such as network managers. To overcome these constraints, the design study employed a user‐centered design process and a variety of methods to incorporate user feedback throughout the design of BubbleNet. This approach resulted in a successfully evaluated dashboard with users and further deployments of these ideas in both research and operational environments. By explaining these methods and the process, it can benefit future visualization designers to help overcome similar challenges in cyber security or alternative domains. 相似文献
87.
Edward Farhi Jeffrey Goldstone David Gosset Harvey B. Meyer 《Computer Physics Communications》2011,(8):1663-1673
In this paper we explore ways to study the zero temperature limit of quantum statistical mechanics using Quantum Monte Carlo simulations. We develop a Quantum Monte Carlo method in which one fixes the ground state energy as a parameter. The Hamiltonians we consider are of the form H=H0+λV with ground state energy E. For fixed H0 and V, one can view E as a function of λ whereas we view λ as a function of E. We fix E and define a path integral Quantum Monte Carlo method in which a path makes no reference to the times (discrete or continuous) at which transitions occur between states. For fixed E we can determine λ(E) and other ground state properties of H. 相似文献
88.
In recent years methods have been developed to extract the seaward landfast ice edge from series of remote sensing images, with most of them relying on incoherent change detection in optical, infrared, or radar amplitude imagery. While such approaches provide valuable results, some still lack the required level of robustness and all lack the ability to fully automate the detection and mapping of landfast ice over large areas and long time spans. This paper introduces an alternative approach to mapping landfast ice extent that is based on coherent processing of interferometric L-band Synthetic Aperture Radar (SAR) data. The approach is based on a combined interpretation of interferometric phase pattern and interferometric coherence images to extract the extent and stability of landfast ice. Due to the low complexity of the base imagery used for landfast ice extraction, significant improvements in automation and reduction of required manual interactions by operators can be achieved. A performance analysis shows that L-band interferometric SAR (InSAR) data enable the mapping of landfast ice with high robustness and accuracy for a wide range of environmental conditions. 相似文献
89.
90.
The usefulness of statistical clustering algorithms developed for automatic segmentation of lesions and organs in magnetic resonance imaging (MRI) intensity data sets suffers from spatial nonstationarities introduced into the data sets by the acquisition instrumentation. The major intensity inhomogeneity in MRI is caused by variations in the B1-field of the radio frequency (RF) coil. A three-step method was developed to model and then reduce the effect. Using a least squares formulation, the inhomogeneity is modeled as a maximum variation order two polynomial. In the log domain the polynomial model is subtracted from the actual patient data set resulting in a compensated data set. The compensated data set is exponentiated and rescaled. Statistical comparisons indicate volumes of significant corruption undergo a large reduction in the inhomogeneity, whereas volumes of minimal corruption are not significantly changed. Acting as a preprocessor, the proposed technique can enhance the role of statistical segmentation algorithms in body MRI data sets. 相似文献