首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   285篇
  免费   2篇
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   43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
  2021年   2篇
  2020年   3篇
  2018年   2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
  1967年   1篇
  1966年   1篇
排序方式: 共有287条查询结果,搜索用时 0 毫秒
11.
The region encoded by amino acids 956-982 of adenylyl cyclase 2 is important for Gbetagamma stimulation. Interactions of a peptide encoding the 956-982 region of adenylyl cyclase 2 (QEHAQEPERQYMHIGTMVEFAYALVGK (QEHA peptide)) with Gbetagamma subunits were studied. QEHA peptide was covalently attached to beta subunit of free Gbetagamma by the cross-linker N-succinimidyl(4-iodoacetyl)aminobenzoate. Cross-linking was proportional to the amount of QEHA peptide added; other control peptides cross-linked minimally. When Go was used, very little cross-linking was observed with GDP and EDTA, but upon activation by guanosine 5'-3-O-(thio)triphosphate and Mg2+, specific cross-linking of the QEHA peptide to Gbeta was observed. We conclude that beta subunits of G proteins contain effector interaction domains that are occluded by Galpha subunits in the heterotrimer. Molecular modeling studies used to dock the QEHA peptide on to Gbeta indicate that amino acids 75-165 of Gbeta may be involved in effector interactions.  相似文献   
12.
Identification and analysis of wax esters by mass spectrometry   总被引:2,自引:0,他引:2  
Several ions in the mass spectra of wax esters were related to the molecular structures. Assigned structures of ions were confirmed by deuterium labeling. A simple, direct method for quantititive analyses of mixtures was developed. The method involved a comparison of sets of three ions, RCO2H+, RCO2H2 + and [R′−1]+ from all compounds in the mixture. The method was found applicable for mixtures of unsaturated wax esters after reduction with tetradeuterio hydrazine. Presented in part before the ISF-AOCS World Congress, Chicago, September 1970. Part III of a series of mass spectrometry of lipids. For VI see Lipids.  相似文献   
13.
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   
14.
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   
15.
Malini Iyengar  Dipak K. Dey 《TEST》2002,11(2):303-315
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   
16.
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   
17.
A new palladium (Pd) based catalyst was developed using poly(diphenylamine-co-3-aminobenzonitrile) (P(DPA-co-3ABN)) as the new catalyst support. The sizes, distribution and stability of Pd nanoparticles (Pd NPs) are strongly influenced by the cyano group (–CN) present in P(DPA-co-3ABN). Field emission scanning electron microscopy image and energy dispersive x-ray analysis revealed good dispersion of Pd NP onto P(DPA-co-3ABN) matrix. The electrocatalytic activity of P(DPA-co-3ABN)/Pd catalyst electrode (CE) was investigated in terms of formic acid (FA) electro oxidation. The onset potential and catalytic current for the electro oxidation of FA are higher at P(DPA-co-3ABN)/Pd-CE as compared to PdNPs loaded pristine PDPA catalyst electrode (PDPA/Pd-CE). P(DPA-co-3ABN)/Pd-CE exhibited 18 time higher electrocatalytic current than PDPA/Pd-CE for oxidation of FA.  相似文献   
18.
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   
19.
Nutritional chemistry of chromium   总被引:1,自引:0,他引:1  
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   
20.
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   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号