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71.
Information systems research often treats computer workarounds tangentially and as temporary phenomena. This exploratory research embraces anomalous system use in general and computer workarounds in particular by suggesting why the latter can be institutionalized and how they may be manifested in practice. Anomalous use is defined as sociomaterial actions around an IT artifact not consistent with its design or related official rules that nevertheless constitute system enactment in practice. The persistence of computer workarounds might be explained by the tension between top-down pressures from the external environment and bottom-up constraints from day-to-day operational work. These insights are drawn from an up-close study of workarounds in two cases from the Mediterranean region. The workaround practices involve decoupling and loose coupling, effectively creating ‘equilibrium’ between the aforementioned top-down and bottom-up influences. This may be attributed to parity between the influence exercised by external regulatory/accrediting bodies and the constraints of day-to-day work within the focal organization (i.e., work ethos, material constraints, and discretion to decouple). Our results show why some computer workarounds exhibit institutionalized behavior and their antecedent conditions. We also suggest that constituent workaround practices may exist as twin but distinctive behavioral patterns – non-compliance (or partial compliance) with an official rule and partially (or fully) working around designed systems.  相似文献   
72.
This paper presents a new methodology to conduct modelling and analysis of soft tissue deformation from the physicochemical viewpoint of soft tissues for surgery simulation. The novelty of this methodology is that soft tissue deformation is converted into a reaction-diffusion process coupled with a mechanical load, and thus reaction-diffusion of mechanical load and non-rigid mechanics of motion are combined to govern the dynamics of soft tissue deformation. The mechanical load applied to a soft tissue to cause a deformation is incorporated into the reaction-diffusion system and consequently distributed among mass points of the soft tissue. An improved reaction-diffusion model is developed to describe the distribution of the mechanical load in the tissue. A generic finite difference scheme is presented for construction of the reaction-diffusion model on a 3D tissue surface. A gradient method is established for derivation of internal forces from the distribution of the mechanical load. Real-time interactive deformation of virtual human organs with haptic feedback has been achieved by the proposed methodology for surgery simulation. The proposed methodology not only accommodates isotropic, anisotropic and inhomogeneous materials by simply modifying diffusion coefficients, but also accepts local and large-range deformations simultaneously.  相似文献   
73.
Argon inhalation attenuates multiorgan failure (MOF) after experimental ischemic injury. We hypothesized that this protection could involve decreased High Mobility Group Box 1 (HMGB1) systemic release. We investigated this issue in an animal model of MOF induced by aortic cross-clamping. Anesthetized rabbits were submitted to supra-coeliac aortic cross-clamping for 30 min, followed by 300 min of reperfusion. They were randomly divided into three groups (n = 7/group). The Control group inhaled nitrogen (70%) and oxygen (30%). The Argon group was exposed to a mixture of argon (70%) and oxygen (30%). The last group inhaled nitrogen/oxygen (70/30%) with an administration of the HMGB1 inhibitor glycyrrhizin (4 mg/kg i.v.) 5 min before aortic unclamping. At the end of follow-up, cardiac output was significantly higher in Argon and Glycyrrhizin vs. Control (60 ± 4 and 49 ± 4 vs. 33 ± 8 mL/kg/min, respectively). Metabolic acidosis was attenuated in Argon and Glycyrrhizin vs. Control, along with reduced amount of norepinephrine to reverse arterial hypotension. This was associated with reduced interleukin-6 and HMGB1 plasma concentration in Argon and Glycyrrhizin vs. Control. End-organ damages were also attenuated in the liver and kidney in Argon and Glycyrrhizin vs. Control, respectively. Argon inhalation reduced HMGB1 blood level after experimental aortic cross-clamping and provided similar benefits to direct HMGB1 inhibition.  相似文献   
74.
Generally decision making for solving ill‐structured problems in DSS takes place in uncertain situations. The main drawbacks of existing traditional DSS are inefficiencies associated with dealing with complex models and large databases. Usually a fuzzy DSS has many input variables and, hence, its knowledge base, containing the totality of fuzzy rules, is very large. Large rule base leads to disadvantages in speed, reliability, and complexity of DSS. This paper introduces an alternative concept for designing fuzzy DSS based on multi‐agent distributed artificial intelligent technology and fuzzy decision making. The main idea of the proposed DSS is based on granulation of the overall system intelligence between cooperative autonomous intelligent agents capable of competing and cooperating with each other in order to propose a total solution to the problem and organization (combining individual solutions) of the proposed solution into the final solution. It is supposed that every agent in DSS is characterized by a set of fuzzy criteria of unequal importance and definition of a “winner” agent is based on multi‐criteria fuzzy decision making involving unequal objectives. © 2000 John Wiley & Sons, Inc.  相似文献   
75.
Composites have become common engineering materials in industries where the strength to weight performance of structures is a key design consideration. The major limiting factors are the high-manufacturing costs and low-production rates. Robotic fibre placement (RFP) is one alternative process to overcome the limiting factors and it is generally suitable for open-continuous components. A novel path planning algorithm for open-contoured structures, entitled the surface curve algorithm for robotic fibre placement (SCAR) is proposed. The algorithm aims to produce a uniform lay-up of composite lamina, without gap and overlap between subsequent tows. A numerical investigation into the characteristics of the algorithm is performed and presented. The algorithm is implemented on complex contoured surface and some of the results are presented in this paper.  相似文献   
76.
This paper reports on the prediction of the expected positioning errors of robot manipulators due to the errors in their geometric parameters. A Swarm Intelligence (SI) based algorithm, which is known as Particle Swarm Optimization (PSO), has been used to generate error estimation functions. The experimental system used is a Motoman SK120 manipulator. The error estimation functions are based on the robot position data provided by a high precision laser measurement system. The functions have been verified for three test trajectories, which contain various configurations of the manipulator. The experimental results demonstrate that the positioning errors of robot manipulators can be effectively predicted using some constant coefficient polynomials whose coefficients are determined by employing the PSO algorithm. It must be emphasized that once the estimation functions are obtained, there may be no need of any further experimental data in order to determine the expected positioning errors for a subsequent use in the error correction process.  相似文献   
77.
Fire events and the related toxicants such as CO are responsible for many fatalities in the current century. These hazardous events are much more dangerous when they occur in enclosed spaces. In the present study, a theoretical relation is developed for horizontal distribution of CO in a large tunnel fire. Then, the developed criterion is used to study the effect of some rudimentary parameters such as the heat release rate (HRR) of fire and tunnel’s aspect ratio (AR) on CO and temperature stratification. Theoretical results of various heat release rates and aspect ratios for horizontal distribution of CO are compared with numerical results using fire dynamics simulator (FDS5.5). It is found that big fires have higher rates of CO concentration decay in comparison to the smaller ones due to higher air entrainment into the travelling plume. It is indicated that the smoke travelling at higher values of tunnel AR, dilutes faster. Moreover, using FDS5.5, the relevant variations in temperature and CO concentration are discussed for tunnel angles ranging from ?20° to 20°.  相似文献   
78.
79.
In this paper, the optimization-simulation approach is proposed to investigate energy saving potential of an air-cooled direct expansion rooftop package air conditioning system by refining the model of the HVAC system components and deriving optimal configuration for evaporator coil subject to technical constraints. In this method the frontal area of the evaporator coil is maintained as constant and the variation of other geometrical parameters on the thermal and economical performance of the system is investigated. An actual air-cooled rooftop package of a real-world commercial building in hot and dry climate conditions is used for experimental data collection. Both inputs and outputs are measured from the field monitoring in two summer weeks. Based on the mathematical models and using collected data, modules incorporating the proposed optimal redesign procedure were embedded in a transient simulation tool. A mixed heuristic- deterministic optimization algorithm was implemented in the transient tool to determine the synthesis and design variables that influence the cost and energy efficiency of each configuration. Available experimental results were compared to predicted results to validate the model. Afterwards, the computer model was used to predict how changes in cooling coil geometry would affect the building thermal comfort, the cost and energy consumption of the system.  相似文献   
80.
In the current study, the effect of extracted cellulose nanofibers (CNFs) on rheological and mechanical properties and biodegradability of polyethylene/starch blend was investigated. The CNFs were extracted from wheat straws using a chemo‐mechanical method. Polyethylene/starch blend was reinforced by different amounts of CNF (6–14 wt%) using an internal mixer followed by a single screw extruder. The flow properties of nanocomposites were investigated by determining Melt Flow Index (MFI) and viscosity. Due to the weak interaction of cellulosic nanofibers and polymers, the flow behavior of nanocomposites was undesirable. Tensile tests were performed to evaluate the mechanical performance of nanocomposites. By increasing the CNF content, the tensile strength and elongation at break declined; whereas, the Young's modulus was improved. The biodegradation of cellulose nanocomposites was investigated by water absorption and degradability tests. Both experiments confirmed the progressive effect of cellulose nanofibers on the degradation of the composites. POLYM. COMPOS., 36:2309–2316, 2015. © 2014 Society of Plastics Engineers  相似文献   
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