全文获取类型
收费全文 | 3682篇 |
免费 | 220篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 40篇 |
化学工业 | 862篇 |
金属工艺 | 44篇 |
机械仪表 | 85篇 |
建筑科学 | 141篇 |
矿业工程 | 5篇 |
能源动力 | 126篇 |
轻工业 | 579篇 |
水利工程 | 27篇 |
石油天然气 | 18篇 |
无线电 | 259篇 |
一般工业技术 | 536篇 |
冶金工业 | 562篇 |
原子能技术 | 23篇 |
自动化技术 | 600篇 |
出版年
2023年 | 19篇 |
2022年 | 22篇 |
2021年 | 152篇 |
2020年 | 72篇 |
2019年 | 82篇 |
2018年 | 106篇 |
2017年 | 103篇 |
2016年 | 128篇 |
2015年 | 114篇 |
2014年 | 155篇 |
2013年 | 218篇 |
2012年 | 178篇 |
2011年 | 273篇 |
2010年 | 151篇 |
2009年 | 186篇 |
2008年 | 169篇 |
2007年 | 155篇 |
2006年 | 138篇 |
2005年 | 94篇 |
2004年 | 104篇 |
2003年 | 113篇 |
2002年 | 93篇 |
2001年 | 57篇 |
2000年 | 69篇 |
1999年 | 70篇 |
1998年 | 202篇 |
1997年 | 130篇 |
1996年 | 97篇 |
1995年 | 72篇 |
1994年 | 54篇 |
1993年 | 45篇 |
1992年 | 22篇 |
1991年 | 23篇 |
1990年 | 16篇 |
1989年 | 19篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 17篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 15篇 |
1976年 | 17篇 |
1973年 | 4篇 |
1965年 | 4篇 |
排序方式: 共有3907条查询结果,搜索用时 15 毫秒
91.
We present a categorical logic formulation of induction and coinduction principles for reasoning about inductively and coinductively defined types. Our main results provide sufficient criteria for the validity of such principles: in the presence of comprehension, the induction principle for initial algebras is admissible, and dually, in the presence of quotient types, the coinduction principle for terminal coalgebras is admissible. After giving an alternative formulation of induction in terms of binary relations, we combine both principles and obtain a mixed induction/coinduction principle which allows us to reason about minimal solutionsX≅σ(X) whereXmay occur both positively and negatively in the type constructor σ. We further strengthen these logical principles to deal with contexts and prove that such strengthening is valid when the (abstract) logic we consider is contextually/functionally complete. All the main results follow from a basic result about adjunctions between “categories of algebras” (inserters). 相似文献
92.
Noninvasive pacing is a valuable therapy in emergency cardiac care. The more experience clinicians have with the noninvasive pacing procedure, the greater their confidence and the easier the job becomes. Effective troubleshooting during pacing becomes less problematic with increased experience with the therapy. Noninvasive pacing allows rapid initiation of emergency pacing and "buys time" to stabilize the patient and plan further care. 相似文献
93.
RF Del Maestro 《Canadian Metallurgical Quarterly》1998,89(5):874-887
The human race has always contemplated the question of the anatomical location of the soul. During the Renaissance the controversy crystallized into those individuals who supported the heart ("cardiocentric soul") and others who supported the brain ("cephalocentric soul") as the abode for this elusive entity. Leonardo da Vinci (1452-1519) joined a long list of other explorers in the "search for the soul." The method he used to resolve this anatomical problem involved the accumulation of information from ancient and contemporary sources, careful notetaking, discussions with acknowledged experts, and his own personal search for the truth. Leonardo used a myriad of innovative methods acquired from his knowledge of painting, sculpture, and architecture to define more clearly the site of the "senso comune"--the soul. In this review the author examines the sources of this ancient question, the knowledge base tapped by Leonardo for his personal search for the soul, and the views of key individuals who followed him. 相似文献
94.
Effects of heating in air and chlorine atmosphere on the crystalline structure of pure Ta2O5 or mixed with carbon 总被引:1,自引:0,他引:1
J. GonzÁLEZ M. Del C. Ruiz J. B. Rivarola D. Pasquevich 《Journal of Materials Science》1998,33(16):4173-4180
Structure changes undergone by pure amorphous hydrated tantalum oxide mixed with different types of carbon when heated in air or chlorine atmospheres were monitored by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). Heating in air of pure Ta2O5 causes the appearance of the hexagonal structure -Ta2O5 at 973 K and the ortho-rhombic structure -Ta2O5 at 1173 K. Heating in chlorine atmosphere markedly lowers the temperature at which transformation to the orthorhombic phase occurs. This effect is attributed to recrystallization of tantalum oxide from tantalum chloride and oxygen, both in gaseous phase, formed in a previous chlorination step of the amorphous oxide. When the thermal treatment is performed in chlorine atmosphere the presence of carbon permits the detection of the hexagonal form at 753 K; this temperature varies with the type of carbon and the oxide : carbon ration. © 1998 Kluwer Academic Publishers 相似文献
95.
Human activity recognition is a challenging problem for context-aware systems and applications. Research in this field has
mainly adopted techniques based on supervised learning algorithms, but these systems suffer from scalability issues with respect
to the number of considered activities and contextual data. In this paper, we propose a solution based on the use of ontologies
and ontological reasoning combined with statistical inferencing. Structured symbolic knowledge about the environment surrounding
the user allows the recognition system to infer which activities among the candidates identified by statistical methods are
more likely to be the actual activity that the user is performing. Ontological reasoning is also integrated with statistical
methods to recognize complex activities that cannot be derived by statistical methods alone. The effectiveness of the proposed
technique is supported by experiments with a complete implementation of the system using commercially available sensors and
an Android-based handheld device as the host for the main activity recognition module. 相似文献
96.
Privacy in geo-social networks: proximity notification with untrusted service providers and curious buddies 总被引:2,自引:0,他引:2
Sergio Mascetti Dario Freni Claudio Bettini X. Sean Wang Sushil Jajodia 《The VLDB Journal The International Journal on Very Large Data Bases》2011,20(4):541-566
A major feature of the emerging geo-social networks is the ability to notify a user when any of his friends (also called buddies)
happens to be geographically in proximity. This proximity service is usually offered by the network itself or by a third party service provider (SP) using location data acquired from the
users. This paper provides a rigorous theoretical and experimental analysis of the existing solutions for the location privacy
problem in proximity services. This is a serious problem for users who do not trust the SP to handle their location data and
would only like to release their location information in a generalized form to participating buddies. The paper presents two
new protocols providing complete privacy with respect to the SP and controllable privacy with respect to the buddies. The
analytical and experimental analysis of the protocols takes into account privacy, service precision, and computation and communication
costs, showing the superiority of the new protocols compared to those appeared in the literature to date. The proposed protocols
have also been tested in a full system implementation of the proximity service. 相似文献
97.
98.
The metric reconstruction of a non-rigid object viewed by a generic camera poses new challenges since current approaches for Structure from Motion assume the rigidity constraint of a shape as an essential condition. In this work, we focus on the estimation of the 3-D Euclidean shape and motion of a non-rigid shape observed by a perspective camera. In such case deformation and perspective effects are difficult to decouple – the parametrization of the 3-D non-rigid body may mistakenly account for the perspective distortion. Our method relies on the fact that it is often a reasonable assumption that some of the points on the object’s surface are deforming throughout the sequence while others remain rigid. Thus, relying on the rigidity constraints of a subset of rigid points, we estimate the perspective to metric upgrade transformation. First, we use an automatic segmentation algorithm to identify the set of rigid points. These are then used to estimate the internal camera calibration parameters and the overall rigid motion. Finally, we formulate the problem of non-rigid shape and motion estimation as a non-linear optimization where the objective function to be minimized is the image reprojection error. The prior information that some of the points in the object are rigid can also be added as a constraint to the non-linear minimization scheme in order to avoid ambiguous configurations. We perform experiments on different synthetic and real data sets which show that even when using a minimal set of rigid points and when varying the intrinsic camera parameters it is possible to obtain reliable metric information. 相似文献
99.
Carmelo Del Valle Antonio Márquez Irene Barba 《Journal of Intelligent Manufacturing》2010,21(1):165-174
This work presents a constraint satisfaction problem (CSP) model for the planning and scheduling of disassembly and assembly
tasks when repairing or substituting faulty parts. The problem involves not only the ordering of assembly and disassembly
tasks, but also the selection of them from a set of alternatives. The goal of the plan is the minimization of the total repairing
time, and the model considers, apart from the durations and resources used for the assembly and disassembly tasks, the necessary
delays due to the change of configuration in the machines, and to the transportation of intermediate subassemblies between
different machines. The problem considers that sub-assemblies that do not contain the faulty part are nor further disassembled,
but allows non-reversible and parallel repair plans. The set of all feasible repair plans are represented by an extended And/Or graph. This extended representation embodies all of the constraints of the problem, such as temporal and resource constraints
and those related to the selection of tasks for obtaining a correct plan. 相似文献
100.
Claudio Brunelli Fabio Garzia Davide Rossi Jari Nurmi 《Journal of Systems Architecture》2010,56(1):38-47
Signal processors exploiting ASIC acceleration suffer from sky-rocketing manufacturing costs and long design cycles. FPGA-based systems provide a programmable alternative for exploiting computation parallelism, but the flexibility they provide is not as high as in processor-oriented architectures: HDL or C-to-HDL flows still require specific expertise and a hardware knowledge background. On the other hand, the large size of the configuration bitstream and the inherent complexity of FPGA devices make their dynamic reconfiguration not a very viable approach. Coarse-grained reconfigurable architectures (CGRAs) are an appealing solution but they pose implementation problems and tend to be application specific. This paper presents a scalable CGRA which eases the implementation of algorithms on field programmable gate array (FPGA) platforms. This design option is based on two levels of programmability: it takes advantage of performance and reliability provided by state-of-the-art FPGA technology, and at the same time it provides the user with flexibility, performance and ease of reconfiguration typical of standard CGRAs. The basic cell template provides advanced features such as sub-word SIMD integer and floating-point computation capabilities, as well as saturating arithmetic. Multiple reconfiguration contexts and partial run-time reconfiguration capabilities are provided, tackling this way the problem of high reconfiguration overhead typical of FPGAs. Selected instances of the proposed architecture have been implemented on an Altera Stratix II EP2S180 FPGA. On this system, we mapped some common DSP, image processing, 3D graphics and audio compression algorithms in order to validate our approach and to demonstrate its effectiveness by benchmarking the benefits achieved. 相似文献