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排序方式: 共有1017条查询结果,搜索用时 31 毫秒
71.
Detection of staphylococcal enterotoxin B in spiked food samples 总被引:9,自引:0,他引:9
Contamination of food with infectious agents, intentional or not, is a global concern with far-reaching economic and social impact. Staphylococcal enterotoxins are a major cause of food poisoning, but most methods for the identification of these agents in food require extensive pretreatment or concentration of the sample prior to analysis. The array biosensor was developed as a portable device for the simultaneous analysis of multiple complex samples for multiple targets with minimal sample preparation. In this study, we use an array biosensor to expand and improve on a staphylococcal enterotoxin B (SEB) assay with the ultimate intent of incorporating testing for SEB into a battery of sensitive and convenient assays for food safety validation. In addition to buffer studies, six different types of food samples, including beverages, homogenates of fruit and meat, and carcass washings, were spiked with SEB, incubated for at least 2 h to permit antigen sequestration, and assayed. For all samples, there were differences in fluorescence intensity, but 0.5 ng of SEB per ml could be detected in <20 min with little if any pretreatment and no sample preconcentration. 相似文献
72.
An overview is given of the models recommended by the International Commission on Radiological Protection (ICRP) for assessing intakes and doses, and summarises biokinetic data obtained after the deposition of different chemical compounds of thorium in the rat lung. The results emphasise the importance of using material-specific data rather than default reference values for absorption into blood. The limitations of external monitoring of the chest or urine analysis are discussed, and comments made on alternative strategies for radiological protection of the worker. 相似文献
73.
Yourtee D Emery J Smith RE Hodgson B 《Journal of molecular graphics & modelling》2000,18(1):26-8, 59-60
Stereolithography (STL) has been used to make plastic models of the solvent accessible surfaces of biopolymers. Models have been made of proteins and proteins bound to DNA and RNA. The STL process uses a laser to photopolymerize a liquid resin. Using the ACES (accurate, clear, epoxy, solid) building technique, parts are made with minimum postcure shrinkage. Protein Data Bank files are converted to STL files that represent the surface topology of the biopolymer as a series of triangles and an index that describes their orientation. The models are useful in teaching biomolecular structure and the principle of docking. They are especially useful to the visually impaired. 相似文献
74.
Let P be a realization of a homogeneous Poisson point process in ℝ
d
with density 1. We prove that there exists a constant k
d
, 1<k
d
<∞, such that the k-nearest neighborhood graph of P has an infinite connected component with probability 1 when k≥k
d
. In particular, we prove that k
2≤213. Our analysis establishes and exploits a close connection between the k-nearest neighborhood graphs of a Poisson point set and classical percolation theory. We give simulation results which suggest
k
2=3. We also obtain similar results for finite random point sets.
Part of the work was done while S.-H. Teng was at Xerox Palo Alto Research Center and MIT.
The work of F.F. Yao was supported in part by a grant from the Research Grants Council of the Hong Kong Special Administrative
Region, China [Project No. CityU 1165/04E]. 相似文献
75.
76.
Buddhika Abeyrathna Bernard Rolfe Peter Hodgson Matthias Weiss 《International Journal of Material Forming》2016,9(3):423-434
The roll forming process is increasingly used in the automotive industry for the manufacture of structural and crash components from Ultra High Strength Steel (UHSS). Due to the high strength of UHSS (<1GPa) even small and commonly observed material property variations from coil to coil can result in significant changes in material yield and through that affect the final shape of the roll formed component. This requires the re-adjustment of tooling to compensate for shape defects and maintain part geometry resulting in costly downtimes of equipment. This paper presents a first step towards an in-line shape compensation method that based on the monitoring of roll load and torque allows for the estimation of shape defects and the subsequent re-adjustment of tooling for compensation. For this the effect of material property variation on common shape defects observed in the roll forming process as well as measurable process parameters such as roll load and torque needs to be understood. The effect of yield strength and material hardening on roll load and torque as well as longitudinal bow is investigated via experimental trials and numerical analysis. A regression analysis combined with Analysis of Variance (ANOVA) techniques is employed to establish the relationships between the process and material parameters and to determine their percentage influence on longitudinal bow, roll load and torque. The study will show that the level of longitudinal bow, one of the major shape defects observed in roll forming, can be estimated by variations in roll load and torque. 相似文献
77.
Learning to use new technologies by older adults: Perceived difficulties,experimentation behaviour and usability 总被引:1,自引:0,他引:1
This paper examines the factors and theoretical frameworks for the adoption of technology for older adults, and proposes two models of technology acceptance and rejection, one from an ease of learning perspective, and one from a system and user perspective. Both models are supported from reports on two case studies of older adults using handheld touchscreen tablet devices; one in which the participants are supported during tasks primarily related to walking and navigation, and one in which participants are unsupported in communication related tasks. The first study shows the powerful role that facilitating conditions have for learning how to use digital technologies for this user group, whether supporting through step by step guidance, providing a friendly space to use trial and error methods, and/or provision of a manual. The second study shows the pitfalls of a lack of facilitating conditions during initial use, and highlights potential for appropriate design in helping to avoid some user errors during this phase. 相似文献
78.
Fredrik Hedenus Sten KarlssonChristian Azar Frances Sprei 《International Journal of Hydrogen Energy》2010
The aim of this study is to examine how the options for producing electricity, fuels, and heat in a carbon-constrained world affect the cost-effectiveness of a range of fuels and propulsion technologies in the transportation sector. GET 7.0, a global energy system model with five end-use sectors, is used for the analysis. We find that an energy system dominated either by solar or by nuclear tends to make biofuels in plug-in hybrids cost-effective. If coal with carbon capture and storage (CCS) dominates the energy system, hydrogen cars, rather than plug-in hybrids tend to become cost-effective. Performing a Monte Carlo simulation, we then show that the general features of our results hold for a wide range of assumptions for the costs of vehicle propulsion technologies (e.g., batteries and fuel cells). However, sufficiently large changes in say the battery costs may overturn the impact of changes in the energy supply system, so that plug-in hybrid vehicles become cost-effective even if coal with CCS dominate the energy supply. We conclude that analyses of future energy carriers and propulsion technologies need to consider developments in the energy supply system. 相似文献
79.
Weimin Gao Lingxue Kong John M. Long Peter D. Hodgson 《Journal of Materials Processing Technology》2009,209(1):497-505
The mass (e.g. carbon) transfer coefficient at a workpiece surface is an important kinetic factor to control the heat treatment process of the workpiece and to evaluate heat treatment equipment. The coefficient can be calculated from the carbon concentration at the surface of a sample carburized in a carburizing furnace for a given time. Two common measurement methods which use a thin plate and employ a component as samples respectively are evaluated and compared for sensitivity and uncertainty. The comparison shows that the use of a component produces higher measurement precision and also has the advantage in measuring the carbon transfer coefficients at different treated positions. This method is then extended and discussed methodologically. Also two equations are proposed to calculate the carbon transfer coefficient and its uncertainty, respectively. This method is also applied to measure the carbon transfer coefficient in a fluidized bed heat treatment furnace. 相似文献
80.
Abstract The sensitivity of the output power of stable resonators in multimode operation to mirror tilt was investigated both theoretically and experimentally. It is shown that the decrease of power is only caused by the decreasing mode volume inside the active medium. A simple geometrical model including the refractive power of the medium is used to derive expressions for the tilt angles at which the power has decreased by 10%. Experiments were performed with pulsed Nd : YAG lasers, the results showing good agreement with the theoretical predictions. 相似文献