全文获取类型
收费全文 | 117篇 |
免费 | 1篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 12篇 |
机械仪表 | 2篇 |
建筑科学 | 1篇 |
矿业工程 | 5篇 |
能源动力 | 4篇 |
轻工业 | 2篇 |
水利工程 | 1篇 |
无线电 | 12篇 |
一般工业技术 | 13篇 |
冶金工业 | 58篇 |
原子能技术 | 1篇 |
自动化技术 | 5篇 |
出版年
2021年 | 1篇 |
2018年 | 1篇 |
2014年 | 1篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 3篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 5篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 3篇 |
1965年 | 2篇 |
1955年 | 1篇 |
1943年 | 1篇 |
1937年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有118条查询结果,搜索用时 15 毫秒
21.
Daniel A. del Cid Daniel Larranaga Matthew Leitao Robert L. Mosher Sara R. Berzenski Vipal Gandhi 《Ergonomics》2021,64(1):69-77
Abstract The widespread use of virtual reality head-mounted-displays (HMDs) calls for a re-examination of the impact of prolonged exposure to fixed visual displays at close ocular proximity. The purpose of this study is to validate the Virtual Reality Symptoms Questionnaire (VRSQ), created to understand symptoms of prolonged HMDs use, and Computer Use Survey (CUS), created to assess general physical and visual discomfort symptoms. Participants (N?=?100) recorded their general discomfort symptoms using the CUS, performed an interactive task using a HMD for thirty minutes, and then answered the CUS again along with the VRSQ. VRSQ, analysed using an exploratory factor analysis, indicated a clear two-factor solution, and demonstrated very good internal consistency (α?=?0.873). The CUS, also analysed using an exploratory factor analysis, indicated a four-factor solution, and demonstrated good internal consistency (α?=?0.838). Practitioner Summary: A quantitative-experimental study was conducted to explore the factor structure and validate both the Virtual Reality Symptoms Questionnaire (VRSQ), and the Computer Use Survey (CUS). Findings indicate the VRSQ and CUS are precise and accurate survey instruments for evaluating discomfort after VR-HMD use and the latter for computer use. Abbreviations: VRSQ: virtual reality symptom questionnaire; CUS: computer use survey; OLED: organic light-emitting diode; MSQ: pensacola motion symptom questionnaire; SSQ: simulator sickness questionnaire; 3?D: three-dimensional computer generated space; VR: virtual reality; VR-HMD: virtual reality head-mounted-display; HMDs: head-mounted-displays; EFA: exploratory factor analysis 相似文献
22.
A new method for source localization is described that is based on a modification of the well-known MUSIC algorithm. In classical MUSIC, the array manifold vector is projected onto an estimate of the signal subspace. Errors in the estimate of the signal subspace can make localization of multiple sources difficult. Recursively applied and projected (RAP) MUSIC uses each successively located source to form an intermediate array gain matrix and projects both the array manifold and the signal subspace estimate into its orthogonal complement. The MUSIC projection to find the next source is then performed in this reduced subspace. Special assumptions about the array manifold structure, such as Vandermonde or shift invariance, are not required. Using the metric of principal angles, we describe a general form of the RAP-MUSIC algorithm for the case of diversely polarized sources. Through a uniform linear array simulation with two highly correlated sources, we demonstrate the improved Monte Carlo error performance of RAP-MUSIC relative to MUSIC and two other sequential subspace methods: S and IES-MUSIC. We then demonstrate the more general utility of this algorithm for multidimensional array manifolds in a magnetoencephalography (MEG) source localization simulation 相似文献
23.
Rini Christine; Redd William H.; Austin Jane; Mosher Catherine E.; Meschian Yeraz Markarian; Isola Luis; Scigliano Eileen; Moskowitz Craig H.; Papadopoulos Esperanza; Labay Larissa E.; Rowley Scott; Burkhalter Jack E.; Schetter Christine Dunkel; DuHamel Katherine N. 《Canadian Metallurgical Quarterly》2011,79(1):64
Objective: Hematopoietic stem cell transplant (HSCT) survivors who are 1 to 3 years posttransplant are challenged by the need to resume valued social roles and activities—a task that may be complicated by enduring transplant-related psychological distress common in this patient population. The present study investigated whether transplant survivors who receive adequate social support from their spouse or intimate partner experience lower distress. Method: Effects of receiving a greater quantity of partner support (a common approach to studying enacted support) were compared with effects of receiving more effective partner support (i.e., support that more closely matches their needs in terms of its quantity and quality). Men and women (N = 230) who were 1 to 3 years posttransplant completed measures of partner support quantity (Manne & Schnoll, 2001), partner social support effectiveness (Rini & Dunkel Schetter, 2010), and psychological distress (Brief Symptom Inventory; Derogatis & Spencer, 1982). Potential medical and sociodemographic confounds were controlled in analyses. Results: As hypothesized, survivors reported less distress when they received more effective partner support (p 相似文献
24.
25.
MEG-based imaging of focal neuronal current sources 总被引:7,自引:0,他引:7
The authors describe a new approach to imaging neural current sources from measurements of the magnetoencephalogram (MEG) associated with sensory, motor, or cognitive brain activation. Many previous approaches to this problem have concentrated on the use of weighted minimum norm (WMN) inverse methods. While these methods ensure a unique solution, they do not introduce information specific to the MEG inverse problem, often producing overly smoothed solutions and exhibiting severe sensitivity to noise. The authors describe a Bayesian formulation of the inverse problem in which a Gibbs prior is constructed to reflect the sparse focal nature of neural current sources associated with evoked response data. The authors demonstrate the method with simulated and experimental phantom data, comparing its performance with several WMN methods 相似文献
26.
The United States plans to use a layered approach to protect its forces and allies against short-range ballistic missiles, which have ranges less than 3500 km. Area defenses such as the land-based Theater High Altitude Area Defense (Thaad) and the sea-based upper-tier defenses will cover broad areas. Patriot PAC-2 and PAC-3 and the sea-based lower-tier defenses will be a backup for targets missed by the upper tier and protect high-value targets such as airfields, ports, headquarters, and population centers. The Airborne Laser will aim to destroy missiles during the boost phase, when their rocket motors are burning and before they can deploy warheads, decoys, or submunitions. A theater battle management system will coordinate the system's many components 相似文献
27.
V Ozeri I Rosenshine DF Mosher R F?ssler E Hanski 《Canadian Metallurgical Quarterly》1998,30(3):625-637
Entry of group A streptococcus (GAS) into cells has been suggested as an important trait in GAS pathogenicity. Protein F1, a fibronectin (Fn) binding protein, mediates GAS adherence to cells and the extracellular matrix, and efficient cell internalization. We demonstrate that the cellular receptors responsible for protein F1-mediated internalization of GAS are integrins capable of Fn binding. In HeLa cells, bacterial entry is blocked by anti-beta1 integrin monoclonal antibody. In the mouse cell line GD25, a beta1 null mutant, the alphavbeta3 integrin promotes GAS entry. Internalization of these cells by GAS is blocked by a peptide that specifically binds to alphavbeta3 integrin. In both cell lines, entry of GAS requires the occupancy of protein F1 by Fn. Neither the 29 kDa nor the 70 kDa N-terminal fragments or the 120 kDa cell-binding fragment of Fn promote bacterial entry. Fn-coated beads are taken up efficiently by HeLa cells. Both the entry of GAS via protein F1 and the uptake of Fn-coated beads are blocked by anti-beta1 antibody but are unaffected by a large excess of soluble Fn. Internalization of HeLa cells by bacteria bearing increasing amounts of prebound Fn to protein F1 reveals a sigmoidal ultrasensitive curve. These suggest that the ability of particles to interact via Fn with multiple integrin sites plays a central role in their ability to enter cells. 相似文献
28.
Multiple dipole modeling and localization from spatio-temporal MEGdata 总被引:12,自引:0,他引:12
An array of biomagnetometers may be used to measure the spatio-temporal neuromagnetic field or magnetoencephalogram (MEG) produced by neural activity in the brain. A popular model for the neural activity produced in response to a given sensory stimulus is a set of current dipoles, where each dipole represents the primary current associated with the combined activation of a large number of neurons located in a small volume of the brain. An important problem in the interpretation of MEG data from evoked response experiments is the localization of these neural current dipoles. We present here a linear algebraic framework for three common spatio-temporal dipole models: i) unconstrained dipoles, ii) dipoles with a fixed location, and iii) dipoles with a fixed orientation and location. In all cases, we assume that the location, orientation, and magnitude of the dipoles are unknown. With a common model, we show how the parameter estimation problem may be decomposed into the estimation of the time invariant parameters using nonlinear least-squares minimization, followed by linear estimation of the associated time varying parameters. A subspace formulation is presented and used to derive a suboptimal least-squares subspace scanning method. The resulting algorithm is a special case of the well-known MUltiple SIgnal Classification (MUSIC) method, in which the solution (multiple dipole locations) is found by scanning potential locations using a simple one dipole model. Principal components analysis (PCA) dipole fitting has also been used to individually fit single dipoles in a multiple dipole problem. Analysis is presented here to show why PCA dipole fitting will fail in general, whereas the subspace method presented here will generally succeed. Numerically efficient means of calculating the cost functions are presented, and problems of model order selection and missing moments are discussed. Results from a simulation and a somatosensory experiment are presented. 相似文献
29.
Results of the application of Fourier transform infrared (FTIR) spectroscopy to determine the type and amount of surface functional groups in carbon black are reported.Surface functional groups in carbon black have been identified and analyzed using carbon black dispersions in KBr. At low dilutions less than 0.10% (wt/wt), Beer's law is followed. Absorbance at 1720 cm?1 can be assigned to carboxylic acid, while the assignment of the strong band at 1600 cm?1 is uncertain. Semi-quantitative analysis of band shapes indicates that there is a distribution of electronic environments in the carbon blacks. The magnitude of the absorbances (0.02–0.10) correspond to carboxylic or quinone groups in the amount of ~0.1–1.8 meq/g. Further developments of the technique could lead to a quantitative method for the determination of functional groups in carbon black. 相似文献
30.