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排序方式: 共有1780条查询结果,搜索用时 31 毫秒
51.
Panagiotis Patrinos Pantelis Sopasakis Haralambos SarimveisAuthor vitae 《Automatica》2011,(9):2016-2022
In this paper, the strictly convex quadratic program (QP) arising in model predictive control (MPC) for constrained linear systems is reformulated as a system of piecewise affine equations. A regularized piecewise smooth Newton method with exact line search on a convex, differentiable, piecewise-quadratic merit function is proposed for the solution of the reformulated problem. The algorithm has considerable merits when applied to MPC over standard active set or interior point algorithms. Its performance is tested and compared against state-of-the-art QP solvers on a series of benchmark problems. The proposed algorithm is orders of magnitudes faster, especially for large-scale problems and long horizons. For example, for the challenging crude distillation unit model of Pannocchia, Rawlings, and Wright (2007) with 252 states, 32 inputs, and 90 outputs, the average running time of the proposed approach is 1.57 ms. 相似文献
52.
Distributed uplink scheduling in OFDMA systems is considered. In the proposed model, mobile terminals have the responsibility of making their own transmission decisions. The proposed scheme is based on two dimensional reservation in time and frequency. Terminals use channel state information in order to favor transmissions over certain subchannels, and transmission is done in a probabilistic manner. The proposed approach provides more autonomy to mobile devices in making transmission decisions. Furthermore, it allows avoiding collisions during transmission since it leads to collision detection during the resource reservation phase. The proposed approach is compared to other random access methods and shown to be superior in terms of increasing sum-rate, reducing the number of users in outage, and reducing the collision probability in the reservation phase. 相似文献
53.
54.
Elias Salameh 《国际水》2013,38(3):469-473
Abstract The Water Poverty Index (WPI) of arid and semiarid climatic zones is redefined by introducing the contribution of rainfed agriculture into WPI calculations and by making the WPI equation account for diversities in climatic conditions within arid and semiarid zones and for recycled household water used in irrigation. 相似文献
55.
Panagiotis Papadakos Nikos Armenatzoglou Stella Kopidaki Yannis Tzitzikas 《Knowledge and Information Systems》2012,30(3):493-525
Most Web Search Engines (WSEs) are appropriate for focalized search, i.e., they make the assumption that users can accurately
describe their information need using a small sequence of terms. However, as several user studies have shown, a high percentage
of search tasks are exploratory, and focalized search very commonly leads to inadequate interactions and poor results. This
paper proposes exploiting static and dynamically mined metadata for enriching web searching with exploration services. Online results clustering, which is a mining task of dynamic nature since it is based on query-dependent snippets, is useful for providing users with
overviews of the top results and thus allowing them to restrict their focus to the desired parts. On the other hand, the various
static metadata that are available to a search engine (e.g., domain, language, date, and filetype) are commonly exploited only through the
advanced (form-based) search facilities that some WSEs offer (and users rarely use). We propose an approach that combines
both kinds of metadata by adopting the interaction paradigm of dynamic taxonomies and faceted exploration, which allows the users
to restrict their focus gradually using both static and dynamically derived metadata. Special focus is given on the design
and analysis of incremental algorithms for speeding up the exploration process. The experimental evaluation over a real WSE
shows that this combination results to an effective, flexible, and efficient exploration experience. Finally, we report the
results of a user study indicating that this direction is promising in terms of user preference, satisfaction, and effort. 相似文献
56.
57.
Scientific
activity has been increasing in Puerto Rico in recent years, a development
mirrored not only by the amount of papers published, but by the international
links established for scientific co-operation. The purpose of the present study
is to identify and discuss the patterns of such co-operation, along with the
trends in scientific research conducted in that context at Puerto Rican
institutions. The methodology includes an analysis of the main areas of
research addressed, defined as the area of specialization of the journals
publishing papers indexed in the Science Citation Index (CD-ROM version) from
1980 to 1999. A total of 7271 studies, appearing in 1240 scientific journals,
were selected to study the co-operation established between Puerto Rican institutions
and organizations in other countries. The findings showed a high rate of
international co-operation: 46.07% of the papers published were co-authored by
researchers from other countries. The country accounting for the highest
percentage of joint research was the USA, followed by Germany, United Kingdom,
Canada and Italy. The close relationship between the Puerto Rican and US
scientific systems is not unusual, inasmuch as the economic and socio-political
bonds between them play an essential role in Puerto Rican scientific activity.
The results also revealed substantial differences between the nineteen eighties
and the nineties in terms of the nature of the links established, as well as
growing internationalization of scientific research conducted on the island
over the twenty-year period studied. 相似文献
58.
59.
We consider selfish routing over a network consisting of m parallel
links through which $n$ selfish users route their traffic trying to
minimize their own expected latency. We study the class of mixed
strategies in which the expected latency through each link is at most
a constant multiple of the optimum maximum latency had global
regulation been available. For the case of uniform links it is known
that all Nash equilibria belong to this class of strategies. We are
interested in bounding the coordination ratio (or price of anarchy) of
these strategies defined as the worst-case ratio of the maximum (over
all links) expected latency over the optimum maximum latency. The load
balancing aspect of the problem immediately implies a lower bound
Ω(ln m ln ln m) of the coordination
ratio. We give a tight (up to a multiplicative constant) upper bound.
To show the upper bound, we analyze a variant of the classical balls
and bins problem, in which balls with arbitrary weights are placed
into bins according to arbitrary probability distributions. At the
heart of our approach is a new probabilistic tool that we call ball
fusion; this tool is used to reduce the variant of the problem where
balls bear weights to the classical version (with no weights). Ball
fusion applies to more general settings such as links with arbitrary
capacities and other latency functions. 相似文献
60.
Pantelis N Botsaris Panagiotis D SparisAuthor vitae 《Microprocessors and Microsystems》1997,20(10):182-593
The present paper describes a new design for a microcontrolled three-way catalyst efficiency monitoring system. The system is based on the Motorola 68HC11e2 microprocessor and utilizes the differential signal from a pair of thermocouples installed at the catalyst outlet and inlet sections. This signal is processed in real time using an appropriate statistical algorithm and the corresponding results are compared to experimentally determined limiting values to assess the current state of the catalyst efficiency during driving conditions. The result of this comparison is presented on an LCD display as an A, B, C, or FAIL catalyst condition signal. The system can be readily installed and can operate on new and used cars provided that the type of catalyst used has been experimentally tested to provide the necessary limiting values that characterize its relative levels of efficiency. It can also be reprogrammed and calibrated via a RS232C serial interface. 相似文献