全文获取类型
收费全文 | 1751篇 |
免费 | 113篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 22篇 |
综合类 | 4篇 |
化学工业 | 411篇 |
金属工艺 | 21篇 |
机械仪表 | 19篇 |
建筑科学 | 101篇 |
矿业工程 | 3篇 |
能源动力 | 78篇 |
轻工业 | 177篇 |
水利工程 | 11篇 |
石油天然气 | 3篇 |
无线电 | 185篇 |
一般工业技术 | 349篇 |
冶金工业 | 86篇 |
原子能技术 | 13篇 |
自动化技术 | 385篇 |
出版年
2024年 | 4篇 |
2023年 | 22篇 |
2022年 | 39篇 |
2021年 | 53篇 |
2020年 | 30篇 |
2019年 | 47篇 |
2018年 | 46篇 |
2017年 | 43篇 |
2016年 | 43篇 |
2015年 | 59篇 |
2014年 | 81篇 |
2013年 | 112篇 |
2012年 | 92篇 |
2011年 | 143篇 |
2010年 | 133篇 |
2009年 | 101篇 |
2008年 | 113篇 |
2007年 | 98篇 |
2006年 | 85篇 |
2005年 | 76篇 |
2004年 | 51篇 |
2003年 | 64篇 |
2002年 | 61篇 |
2001年 | 26篇 |
2000年 | 27篇 |
1999年 | 34篇 |
1998年 | 17篇 |
1997年 | 7篇 |
1996年 | 19篇 |
1995年 | 14篇 |
1994年 | 21篇 |
1993年 | 19篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1967年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有1868条查询结果,搜索用时 15 毫秒
121.
The so-called General Adaptive Neighborhood Image Processing (GANIP) approach is presented in a two parts paper dealing respectively
with its theoretical and practical aspects. The General Adaptive Neighborhood (GAN) paradigm, theoretically introduced in
Part I [20], allows the building of new image processing transformations using context-dependent analysis. With the help of
a specified analyzing criterion, such transformations perform a more significant spatial analysis, taking intrinsically into account the local radiometric,
morphological or geometrical characteristics of the image. Moreover they are consistent with the physical and/or physiological
settings of the image to be processed, using general linear image processing frameworks.
In this paper, the GANIP approach is more particularly studied in the context of Mathematical Morphology (MM). The structuring
elements, required for MM, are substituted by GAN-based structuring elements, fitting to the local contextual details of the
studied image. The resulting morphological operators perform a really spatially-adaptive image processing and notably, in
several important and practical cases, are connected, which is a great advantage compared to the usual ones that fail to this
property. 相似文献
122.
系统封装(System In Packaging)是电子封装工艺的前沿技术。为了研究这种高密度电子封装器件的热特性,寻求提高散热速率的途径,开发了一个SIP典型器件的传热模型,模拟了器件的热传递过程和温度分布状况,探讨了各种设计参数和物性参数对温度场的影响,为进一步改善器件的热性能提供了理论依据。 相似文献
123.
Active centers, catalytic behavior, symbiosis and redox properties of MoV(Nb,Ta)TeO ammoxidation catalysts 总被引:1,自引:0,他引:1
Robert K. Grasselli Douglas J. Buttrey James D. Burrington Arne Andersson Johan Holmberg Wataru Ueda Jun Kubo Claus G. Lugmair Anthony F. Volpe Jr 《Topics in Catalysis》2006,38(1-3):7-16
Selective as well as waste forming active centers were defined for MoVNbTeO and MoVTaTeO catalysts in the ammoxidation of
propane to acrylonitrile and all catalytic functionalities were assigned to specific elements at the respective active centers.
Symbiosis between M1 and M2 phases of these catalysts was observed, with phase cooperation being more extensive in the Nb than Ta containing compositions.
The difference in catalytic effectiveness arises most likely because contact and surface area exposure of the two respective,
cooperating phase pairs are not equal. The M1 phase of the catalysts is reducible by propane and ammonia in the absence of dioxygen and is regenerable to its original,
fully oxidized state by dioxygen (air). No structural collapse is observed even after 120 C3H8 + NH3 reduction pulses. The so induced reduction of the catalyst extends up to 70 layers deep. The product distribution over the
first few pulses is very similar to that under catalytic conditions, supporting the concept that lattice oxygen is involved
in the catalytic ammoxidation process. Therefore, the ammoxidation of paraffins is a redox process, as is of course the well-known
olefin ammoxidation process. 相似文献
124.
Low-ash vitrinite concentrates of representative South African coals have been prepared and analysed. Various properties when plotted against carbon content show inflections at to 2% lower carbon content than normal British coals. These differences are ascribed to the heating effects of dolerite intrusions. 相似文献
125.
126.
The ideas of parallel imaging techniques, designed to shorten the acquisition time by the simultaneous use of multiple receive coils, can be adapted for parallel transmission of a spatially selective multidimensional RF pulse. In analogy to data acquisition, a multidimensional RF pulse follows a certain trajectory in k-space. Shortening this trajectory shortens the pulse duration. The use of multiple transmit coils, each with its own time-dependent waveform and spatial sensitivity, compensates for the missing parts of k-space. This results in a maintained spatial definition of the pulse profile while its duration is reduced. This paper describes the basic equations of parallel transmission with arbitrarily shaped transmit coils ("Transmit SENSE") focusing on two-dimensional RF pulses. Results of numerical studies are presented demonstrating the theoretical feasibility of the approach. 相似文献
127.
Johan Bos 《Journal of Logic, Language and Information》2004,13(2):139-157
In this paper I introduce a formalism for natural language understandingbased on a computational implementation of Discourse RepresentationTheory. The formalism covers a wide variety of semantic phenomena(including scope and lexical ambiguities, anaphora and presupposition),is computationally attractive, and has a genuine inference component. Itcombines a well-established linguistic formalism (DRT) with advancedtechniques to deal with ambiguity (underspecification), and isinnovative in the use of first-order theorem proving techniques.The architecture of the formalism for natural language understandingthat I advocate consists of three levels of processing:underspecification, resolution, andinference. Each of these levels has a distinct function andtherefore employs a different kind of semantic representation. Themappings between these different representations define the interfacesbetween the levels.I show how underspecified semantic representations can be built in acompositional way (for a fragment of English Grammar) using standardtechniques borrowed from the -calculus, how inferences can becarried out on discourse representations using a translation tofirst-order logic, and how existing research prototypes (discourseprocessing and spoken-dialogue systems) implement the formalism. 相似文献
128.
The retention of five proteins was compared on a set of three strong cation exchange adsorbents that differed in spacer arm chemical structure and length. The adsorbents included a commercial product, Amersham Biosciences SP Sepharose Fast Flow, containing a six-carbon spacer between the agarose matrix and the anionic ligand, and two custom-prepared materials. One of the custom adsorbents contained a spacer of about half the length of the SP Sepharose Fast Flow, and the other contained no spacer arm. The adsorbent with no spacer arm was found to be significantly more retentive for all of the test proteins examined, in both isocratic and gradient elution tests. Reducing the spacer arm length by half resulted in increased retention for four of the five proteins, but this increase was less than what was observed when the spacer arm was eliminated. Retention increases were obtained without increasing the density of the anionic charge groups and appear to result from an enhancement of electrostatic or secondary nonelectrostatic interactions, or both. The results indicate that spacer arm length may be a useful variable in manipulating stationary-phase retention properties. 相似文献
129.
The practical difficulties encountered in analyzing the kinetics of new reactions are considered from the viewpoint of the capabilities of state-of-the-art high-throughput systems. There are three problems. The first problem is that of model selection, i.e., choosing the correct reaction rate law. The second problem is how to obtain good estimates of the reaction parameters using only a small number of samples once a kinetic model is selected. The third problem is how to perform both functions using just one small set of measurements. To solve the first problem, we present an optimal sampling protocol to choose the correct kinetic model for a given reaction, based on T-optimal design. This protocol is then tested for the case of second-order and pseudo-first-order reactions using both experiments and computer simulations. To solve the second problem, we derive the information function for second-order reactions and use this function to find the optimal sampling points for estimating the kinetic constants. The third problem is further complicated by the fact that the optimal measurement times for determining the correct kinetic model differ from those needed to obtain good estimates of the kinetic constants. To solve this problem, we propose a Pareto optimal approach that can be tuned to give the set of best possible solutions for the two criteria. One important advantage of this approach is that it enables the integration of a priori knowledge into the workflow. 相似文献
130.
Reasoning About Space: The Modal Way 总被引:6,自引:0,他引:6
Aiello Marco; van Benthem Johan; Bezhanishvili Guram 《Journal of Logic and Computation》2003,13(6):889-920