全文获取类型
收费全文 | 284篇 |
免费 | 2篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 33篇 |
金属工艺 | 5篇 |
机械仪表 | 5篇 |
建筑科学 | 21篇 |
能源动力 | 2篇 |
轻工业 | 5篇 |
无线电 | 42篇 |
一般工业技术 | 59篇 |
冶金工业 | 47篇 |
原子能技术 | 5篇 |
自动化技术 | 61篇 |
出版年
2021年 | 2篇 |
2020年 | 3篇 |
2017年 | 2篇 |
2013年 | 3篇 |
2012年 | 4篇 |
2011年 | 7篇 |
2010年 | 8篇 |
2009年 | 8篇 |
2008年 | 5篇 |
2007年 | 13篇 |
2006年 | 7篇 |
2005年 | 9篇 |
2004年 | 11篇 |
2003年 | 8篇 |
2002年 | 10篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1994年 | 4篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有286条查询结果,搜索用时 15 毫秒
11.
X. Liang F. L. C. Ong P. Pillai P. M. L. Chan V. Mancuso G. Koltsidas F. N. Pavlidou L. Caviglione E. Ferro A. Gotta H. Cruickshank S. Iyengar G. Fairhurst 《International Journal of Satellite Communications and Networking》2007,25(4):409-440
This is the second part of the tutorial paper following the previous tutorial paper describing enabling technologies in digital video broadcasting (DVB) system. The paper presents the current and future operational scenarios for DVB via satellite (DVB‐S) system. Review of the current state‐of‐the‐art technologies consisting of integration of broadband Internet and mobile communications and integration of broadband Internet and DVB are given. The future operational scenarios emphasize the fusion of DVB systems with other technologies in terms of network fusion and terminal fusion. For satellite service scenarios, it also takes into consideration mobility management and standard quality‐of‐service mechanism issues, such as integrated services and differentiated services. Several research directions for providing seamless services regardless of network, access technology and terminal in the fusion network are also highlighted in this paper. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
12.
This article discusses about the developing paradigms of data for sensor-actuator networks that perform engineering tasks. We provide a new foundation for data fusion based on two concepts: a conceptual framework and the goal-seeking paradigm. The conceptual framework emphasizes the dominant structures in the system. The goal-seeking paradigm is a mechanism for representing system evolution that explicitly manages uncertainty. The goal-seeking formulation for data fusion helps to distinguish between subjective decisions that can be executed by computers. These notions are useful for critical tasks, such as security management in large-scale distributed systems. Investigations in this area, and further refinement of the goal-seeking formulation for instrumentation and measurement applications, are likely to future systems that facilitate holistic user decision making. 相似文献
13.
Compositional data occur as natural realizations of multivariate observations comprising element proportions of some whole
quantity. Such observations predominate in disciplines like geology, biology, ecology, economics and chemistry. Due to unit
sum constraint on compositional data, specialized statistical methods are required for analyzing these data. Dirichlet distributions
were originally used to study compositional data even though this family of distribution is not appropriate (see Aitchison,
1986) because of their extreme independence properties. Aitchison (1982) endeavored to provide a viable alternative to existing
methods by employing Logistic Normal distribution to analyze such constrained data. However this family does not include the
Dirichlet class and is therefore unable to address the issue of extreme independence. In this paper generalized Liouville
family is investigated to model compositional data which includes covariates. This class permits distributions that admit
negative or mixed correlation and also contains non-Dirichlet distributions with non-positive correlation and overcomes deficits
in the Dirichlet class. Semiparametric Bayesian methods are proposed to estimate the probability density. Predictive distributions
are used to assess performance of the model. The methods are illustrated on a real data set. 相似文献
14.
Summary The thermal post buckling behavior of simply-supported, antisymmetric cross-ply plates with immovable edges is investigated in this paper. For this purpose, a one term approximation for the inplane and transverse displacements is assumed and Rayleigh-Ritz method is used to obtain the equations of equilibrium. The question, whether the true thermal buckling (bifurcation buckling under thermal loads) exists for such plates is also addressed to. The conditions under which the thermal buckling in the classical sense occurs are derived. It is shown that nonlinear bending stiffness for such plates is direction dependent, because of an extra quadratic nonlinear term in addition to the usual cubic nonlinear term in the governing equilibrium equation. Results are presented for various plate configurations. 相似文献
15.
Kovacs Maria; Iyengar Satish; Goldston David; Obrosky D. Scott; Stewart James; Marsh Judith 《Canadian Metallurgical Quarterly》1990,58(2):189
Mothers of children with newly diagnosed insulin-dependent diabetes mellitus (IDDM) were assessed repeatedly over a period of 6 years in order to determine the psychological correlates of managing this chronic illness. Both maternal depression and overall emotional distress after the 1st year of the IDDM increased slightly with illness duration and were also influenced by other factors. Mothers' adjustment shortly after their children were diagnosed with IDDM was a strong predictor of their long-term emotional symptomatology. However, mothers' symptoms over time were not related to medical aspects of IDDM (i.e., the extent of the children's metabolic control, number of rehospitalizations, or their compliance with the medical regimen) and were also unrelated to the levels of depression or anxiety reported by their children. Mothers generally found it easier to cope with the IDDM the longer their children had the illness. However, the degree to which mothers perceived the IDDM to be bothersome or difficult to manage at any given point in time was associated with their overall levels of emotional distress. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
16.
Nutritional chemistry of chromium 总被引:1,自引:0,他引:1
G V Iyengar 《The Science of the total environment》1989,86(1-2):69-74
There has been considerable progress in understanding the role of chromium in human nutrition. However, the lack of data on the forms of chromium-absorption from foods by the gastro-intestinal tract, and our concomitant inability to obtain an accurate assessment of the daily mobile pool of metabolically active chromium in the human body continues to be an impediment in assessing the overall impact of chromium nutrition. Based on recent chromium data on human tissues and body fluids available in the literature, an assessment of chromium content in different body compartments as well as in the total body is presented. However, on the analytical side, a few problems still persist and, therefore, a reliable analysis for chromium is restricted to a few selected laboratories. 相似文献
17.
Systematic studies have been made of the grain growth and density of sintered ZnO-based systems containing one or more additive oxides of the type Nb2O5, Bi2O3, Sb2O3, CoO, Cr2O3, MnO2, NiO and Al2O3. These samples were characterized using such techniques as scanning electron microscopy, X-ray diffraction and electron probe microanalysis. The influence of the nature and amount of additive oxides and sintering temperature is discussed in relation to microstructure, density and the phases present. 相似文献
18.
Experimental investigations have been carried out to study the dynamic damage growth in glass/polyester composites. Detonation of two PETN explosive charges on a modified single edge notch (MSEN) specimen provides the dynamic load in the form of a planar tensile wave. High speed photography is used to record the dynamic damage events. The results show that damage grows perpendicular to the loading direction, similar to the static growth; the damage zone splits analogous to the crack branching in unreinforced polyester. The damage propagation velocity in a composite is higher than the crack propagation velocity in polyester resin. The damage area grows at an average rate of 4.3 m2/sec. Static experiments show that about 4 percent of the total energy is spent on the fiber-matrix interface debonding. The damage zone under dynamic loads is much higher than under static loads. 相似文献
19.
20.
Current psychological theory and research affirm the positive affective and motivational consequences of having personal choice. These findings have led to the popular notion that the more choice, the better—that the human ability to manage, and the human desire for, choice is unlimited. Findings from 3 experimental studies starkly challenge this implicit assumption that having more choices is necessarily more intrinsically motivating than having fewer. These experiments, which were conducted in both field and laboratory settings, show that people are more likely to purchase gourmet jams or chocolates or to undertake optional class essay assignments when offered a limited array of 6 choices rather than a more extensive array of 24 or 30 choices. Moreover, participants actually reported greater subsequent satisfaction with their selections and wrote better essays when their original set of options had been limited. Implications for future research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献