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991.
A microstrip lowpass filter with enhanced performance is developed. The studied filter is based on a novel patch resonator that features strong slow-wave effects, and can also implement either an improved roll-off or an enhanced stop-band. A demonstrator filter with 3 dB cutoff frequency fc ? 2.4 GHz is optimally designed, fabricated and measured. Results indicate that a roll-off of 92.5 dB/GHz together with a relative stop-band bandwidth of 135.5% (referred to a 30 dB suppression) is obtained while achieving a highest figure-of-merit of 10106. Both simulations and measurements are presented and compared. 相似文献
992.
Hui Liu Zili Shao Meng Wang Junzhao Du Chun Jason Xue Zhiping Jia 《Journal of Signal Processing Systems》2009,57(2):249-262
In this paper, we combine coarse-grained software pipelining with DVS (Dynamic Voltage/Frequency Scaling) for optimizing energy
consumption of stream-based multimedia applications on multi-core embedded systems. By exploiting the potential of multi-core
architecture and the characteristic of streaming applications, we propose a two-phase approach to solve the energy minimization
problem for periodic dependent tasks on multi-core processors with discrete voltage levels. With our approach, in the first
phase, we propose a coarse-grained task-level software pipelining algorithm called RDAG to transform the periodic dependent
tasks into a set of independent tasks based on the retiming technique (Leiserson and Saxe, Algorithmica 6:5–35, 1991). In the second phase, we propose two DVS scheduling algorithms for energy minimization. For single-core processors, we propose
a pseudo-polynomial algorithm based on dynamic programming that can achieve optimal solution. For multi-core processors, we
propose a novel scheduling algorithm called SpringS which works like a spring and can effectively reduce energy consumption
by iteratively adjusting task scheduling and voltage selection. We conduct experiments with a set of benchmarks from E3S (Dick
2008) and TGFF () based on the power model of the AMD Mobile Athlon4 DVS processor. The experimental results show that our technique can achieve
12.7% energy saving compared with the algorithms in Zhang et al. (2002) on average.
相似文献
Zhiping JiaEmail: |
993.
Vijay K. Juneja Harry Marks Harshavardhan H. Thippareddi 《Innovative Food Science and Emerging Technologies》2010,11(1):146-154
A predictive dynamic model for Clostridium perfringens spore germination and outgrowth in cooked pork products during cooling is presented. Cooked, ground pork was inoculated with C. perfringens spores and vacuum packaged. For the isothermal experiments, all samples were incubated in a water bath stabilized at selected temperatures between 10 and 51 °C and sampled periodically. For dynamic experiments, the samples were cooled from 54.4 to 27 °C and subsequently from 27 to 4 °C for different time periods, designated as x and y hours, respectively. The growth models used were based on a model developed by Baranyi and Roberts (1994), which incorporates a constant, referred to as the physiological state constant, q0. The value of this constant captures the cells' history before the cooling begins. To estimate specific growth rates, data from isothermal experiments were used, from which a secondary model was developed, based on a particular form of Ratkowsky's 4-parameter equation. Using the data from dynamic experiments and the Ratkowsky model, an optimal value of q0 (=0.01375) was derived minimizing the mean square error of predictions. However, using this estimate, the model had a tendency to over-predict relative growth when there was observed small amounts of relative growth, and under-predict relative growth when there was observed large relative growth. To provide more fail-safe estimates, rather than using the derived value of q0, a value of 0.04 is recommended. The predictive model with this value of q0 would provide more fail-safe estimates of relative growth and could aid producers and regulatory agencies with determining disposition of products that were subjected to cooling deviations.Industrial relevanceSafe time/temperature for cooling of cooked pork is very important to guard against the pathogen in cooked products. Predictive model will assist industry to determine compliance with regulatory performance standards and to ensure microbiological safety of cooked products. 相似文献
994.
The molecular dynamics method is used to investigate the effect of amine grafts on the elastic properties of armchair (5,5) (10,10) and zigzag (9,0) (18,0) single-walled carbon nanotubes (SWCNTs). The results show that Young’s moduli of armchair (5,5) (10,10) and zigzag (9,0) (18,0) SWCNTs with no grafts are 948 GPa, 901 GPa and 804 GPa, 860 GPa, respectively. When the SWCNTs are grafted with 2-8-amine functional groups, Young’s moduli of the zigzag SWCNTs decrease slightly. An increase in the graft number does not cause any further reduction in the moduli, which remain at about 95% of those without grafts. The armchair SWCNTs behave somewhat differently. When they are initially grafted with amine functional groups, their Young’s moduli drop quickly; but decrease slowly as the number of grafts increases. When the number of grafts exceeds 6, the moduli remain at about 72% of those without grafts. The results indicate that the effects of grafted amine on the elastic properties of SWCNTs are related to their chiral angle. This phenomenon is analyzed according to the law of the isoline structure of deformation electron density, C-C bond-length, and the system deformation potential energy of carbon nanotubes with different graft numbers. 相似文献
995.
James K.H. Fang 《The Science of the total environment》2009,407(14):4327-4332
Muscle concentrations of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were determined in rabbitfish Siganus oramin collected from Victoria Harbour and its vicinity, Hong Kong from 2004 to 2007. Spatially, relatively higher levels of ∑PAH (1.05-4.26 μg g− 1) and ∑PCB (45.1-76.9 ng g− 1) were determined in the central and western sites inside the harbour. Temporally, upward trend of ∑PAH, accompanied with a proportion shift from high molecular weight to low molecular weight PAHs, was detected during the three-year study period, suggesting a heavier marine traffic in Victoria Harbour and its western region. However, human health risk assessment based on five individual PAHs indicated that PAHs in fish muscles posed minimal health risk through consumption. In contrast, a downward trend of ∑PCB was registered as the open use of PCBs has been banned. Despite this, the level of ∑PCB in fish muscles still posed a health risk on the local people who have a high fish consumption rate. While seasonal influences on ∑PAH/∑PCB accumulation in S. oramin seemed to be negligible, our findings in S. oramin were in line with the established PAH and PCB levels in sediments and/or mussels from the harbour, suggesting S. oramin can be used as a model fish species for monitoring PAHs and PCBs in the region. 相似文献
996.
This paper presents a study on the mechanical behaviours of a special joint between a rigid suspension cable and a truss girder in a rigid suspension stiffened steel truss bridge. Both a model test and a numerical finite element analysis (FEA) have been conducted, and relevant information about the models used, loading procedure and test scheme is presented. The model test shows that the maximum stress in the joint is less than the material allowable stress and the maximal stress induced from the secondary moment accounts for about 30% of the total stress. A three-dimensional finite element model is used in the numerical analysis and the results are in very good agreement with those of the model test. This study shows that the design of the special joint is reasonable and the structure safe. It is also expected that the results presented in this paper would be useful as references for future research and design of rigid suspension stiffened steel truss bridges and joints. 相似文献
997.
An integrated real options evaluating model for information technology projects under multiple risks
Tao Chen Jinlong Zhang Kin-Keung Lai 《International Journal of Project Management》2009,27(8):776-786
Information technology (IT) investments are exposed to multiple sources of risks. Past information systems research on real options evaluation could not deal with a mix of public and private risks sufficiently in the valuation procedures. Moreover, the relationship between IT investment value and risk factors has rarely been fully explored and remains debatable. In this light, we present an approach based on real options to evaluate IT investments subject to multiple risks. By modeling public risks and private risks in different ways, this approach produces some new results that are different from prior researches. It is found that public risk has an upward effect on the expected payoffs, while private risk influences the options value in a contrary way. The suggested method could help IT managers produce a well-structured valuation process in IT investment decision-making, and understand the interactions between IT risks and options value in a clear way. We also illustrate how the proposed procedure is applied to an ERP project in a construction company. 相似文献
998.
The indoor environmental quality (IEQ) in residential buildings is examined from the prospect of an occupant's acceptance in four aspects: thermal comfort, indoor air quality, noise level and illumination level. Based on the evaluations by 125 occupants living in 32 typical residential apartments in Hong Kong, this study proposes empirical expressions to approximate the overall IEQ acceptance with respect to four contributors, namely operative temperature, carbon dioxide concentration, equivalent noise level and illumination level, via a multivariate logistic regression model. A range of IEQ acceptances for regular residential conditions is determined and the dependence of the predicted overall IEQ acceptance on the variations of the contributors is discussed. The proposed overall IEQ acceptance can be used as a quantitative assessment criterion for similar residential environments where an occupant's evaluation is expected. 相似文献
999.
Since 1996, refuge floors have been an indispensable passive building element of the fire protection plan for Hong Kong high-rise buildings. These floors must be designed to comply with the relevant requirements of the Building Codes of Hong Kong. Hence, 50% of the floor area must be deployed for refuge purposes. And they must have at least two fully open building side walls so that a desired wind effect is assumed so that any smoke that enters will be purged from the safe area. Therefore wind-induced natural cross-ventilation is of prime importance for the protection of the refuge floor in fire safety. If this wind effect is not achieved, entering smoke will accumulate and cause the safety system to fail. Therefore fundamental studies of this flow phenomenon are very important and needed. This paper studies the wind-induced flow behaviour of Hong Kong's refuge floors. Different building wall layout designs are addressed. By way of this study, the author suggests that a refuge floor shall be designed to have two opposite building side walls open instead of the present Building Codes that require at least any two of them. 相似文献
1000.
Pär-Erik Back Rolf Christiansson 《International Journal of Rock Mechanics and Mining Sciences》2009,46(5):896-904
An important feature of underground projects is the early site investigations, performed as a means to identify and quantify hazards. A methodology is presented for identifying the most cost-effective investigation program among a set of alternatives. Methodologies are presented for both investigation of thermal conductivity in hard rock and collection of rock mechanic data for stress induced spalling problems. The cost-effectiveness of an investigation program is estimated by means of value of information analysis (VOIA). Each investigation program of thermal conductivity is associated with uncertainty due to natural variability and lack of knowledge. These uncertainties are taken into account in a simulation model with the aim to estimate the distribution of thermal conductivity values at different scales. The output is a set of thermal conductivity values from which a design parameter can be estimated. The simplest measure of the value of a site investigation is the expected reduction of uncertainty of the design parameter.The methodology is demonstrated with a case study for the prototype nuclear waste repository at Äspö Hard Rock Laboratory, Sweden. A set of four investigation programs for thermal conductivity were evaluated, and the most effective one identified. The application illustrates that an investigation program may supply very different value to a project, depending on how the objective of the investigation is defined. This is demonstrated by using two different objectives and comparing the results. Practical applications of the methodology on both thermal properties and rock mechanics are discussed, with emphasis on site investigations performed by the Swedish Nuclear Fuel and Waste Management (SKB). 相似文献