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61.
62.
Models for the laminar-turbulent transition zone have in recent years become increasingly important, especially in technological
applications where the design is driven by peak heat-transfer rates or extensive regimes of laminar or transitional flow.
Models in current use can be classified into three types, namely linear-combination, algebraic and differential. The first
type based on the principle of combining mean laminar and turbulent velocities, in proportions determined by the intermittency,
is shown to be both successful and relatively easy to implement, especially if recent improvements in estimating turbulent
spot formation rates and ideas concerning the possibility of sub-transitions within the transition zone are incorporated.
Algebraic models, where the eddy viscosity is released by the intermittency, and differential models involving fairly elaborate
schemes for determining the kinetic energy of turbulent fluctuations and their length scale, are found to require further
development for handling flows with large pressure gradients.
The authors wish to express their appreciation to Prof. A Prabhu for support through the project ‘Transition and turbulence
in shear flows’ sponsored by the Department of Science and Technology. 相似文献
63.
Pluronic‐based dual‐stimuli sensitive polymers capable of thermal gelation and pH‐dependent degradation for in situ biomedical application 下载免费PDF全文
Chang‐Hee Whang Hyung Kyung Lee Santanu Kundu S. Narasimha Murthy Seongbong Jo 《应用聚合物科学杂志》2018,135(31)
Thermo‐sensitive hydrogels are considered ideal for applications in the biomedical fields for their biocompatibility, flexibility, tissue‐like water content, and reversible gelation property. By adjusting sufficient hydrophilic–hydrophobic balance in block copolymer structure, thermogel's critical gelation temperature (CGT) can be modified to be near the physiological temperature, which makes it an appealing candidate for in situ gel depot. In this study, we report successful syntheses of novel multiple block copolymer compounds, denoted as dual‐stimuli sensitive polymers (DSSPs), by copolymerizing Pluronic P104 (7100 Da) and 2,2‐bis(aminoethoxy)propane (BAP) using diisocyanate linkers, l ‐lysine ethyl ester diisocyanate (DSSP‐1), and 1,6‐hexamethylene diisocyanate (DSSP‐2). Through effective elongation of polymer chain lengths (DSSP‐1: 41,760 Da, DSSP‐2: 41,230 Da), Pluronic P104's reversible thermal gelation properties were enhanced, as demonstrated by lowered CGTs (DSSP‐1: 36 °C, DSSP‐2: 38.7 °C; 15 wt %) that is near the physiological temperature. Furthermore, integration of acid‐labile BAP allowed rapid pH‐dependent degradation of the polymer, which was displayed by gel permeation chromatography and release profiles of nile red and irinotecan from polymeric micelles and gels, respectively. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46552. 相似文献
64.
I. Narasimha Murthy 《Materials and Manufacturing Processes》2017,32(5):507-516
In the present investigation, efforts are made to use Ferro Chrome (Fe-Cr) slag as a mold material for the replacement of silica sand in the foundry industry. The sodium silicate-Fe–Si process is adopted for evaluating the same. The process parameters considered for this investigation are % of sodium silicate, % of Fe–Si powder as a binder, and mold setting time. A series of sand tests are carried out on sand, slag individually, and for various combinations of these two. Three types of molds are made with sand, slag individually, and combination of these two with 6% sodium silicate and 1.5% Fe–Si. Various ferrous and non-ferrous castings are performed on these newly developed slag molds. The results reveal that the Fe-Cr slag with mold permeability, compression, and shear strength is a suitable candidate for either partial or full replacement of silica sand. During casting neither fusing, dripping, nor collapse of the mold walls is observed in slag molds; this is true for both ferrous and non-ferrous castings. Castings with good surface finish and no surface defects are made by slag molds. Faster heat transfer in slag molds enable to obtain castings with enhanced metallurgical and mechanical properties. 相似文献
65.
K. Narasimha Rao 《Bulletin of Materials Science》2003,26(2):239-245
Deposition of durable thin film coatings by vacuum evaporation on acrylic substrates for optical applications is a challenging
job. Films crack upon deposition due to internal stresses and leads to performance degradation. In this investigation, we
report the preparation and characterization of single and multi-layer films of TiO2, CeO2, Substance2 (E Merck, Germany), Al2O3, SiO2 and MgF2 by electron beam evaporation on both glass and PMMA substrates. Optical micrographs taken on single layer films deposited
on PMMA substrates did not reveal any cracks. Cracks in films were observed on PMMA substrates when the substrate temperature
exceeded 80°C. Antireflection coatings of 3 and 4 layers have been deposited and characterized. Antireflection coatings made
on PMMA substrate using Substance2 (H2) and SiO2 combination showed very fine cracks when observed under microscope. Optical performance of the coatings has been explained
with the help of optical micrographs. 相似文献
66.
A knowledge-based system for improving the consistency between object models and use case narratives
Narasimha Bolloju Christoph Schneider Vijayan Sugumaran 《Expert systems with applications》2012,39(10):9398-9410
In today’s systems development environments, object models are playing an increasingly important role in contributing to the agility and flexibility expected of the information systems being built. While current computer-aided software engineering tools can aid in creating object models, they do not provide much support in ensuring that the object models created are consistent with the specifications in use case narratives. This paper presents a methodology and a knowledge-based system to facilitate the verification of consistency of a given object model against a set of use case narratives. The methodology is implemented as a prototype knowledge-based extension to an open source CASE tool. The prototype’s ability to reliably extract relevant information from use case narratives and its role in verifying the consistency of object models have been evaluated using a laboratory experiment. By analyzing use case narratives utilizing natural language processing techniques and applying collaboration patterns and heuristics, this methodology can determine missing and invalid model elements to guide the analyst in creating object models that are consistent with the requirements specified in a set of use case narratives. The results from this design science research indicate that the prototype system can be a useful tool to assist in this process. 相似文献
67.
An investigation was undertaken on the effect of urea in the preservation of meat. It was observed that there was always a lag period in the early stages of microbial spoilage of meats at different temperatures, due to the non-availability of required nutrients, and subsequent rapid growth of microorganisms was attributed to the utilisation of amino acids released due to autolytic changes. Dry urea salt was employed in the present study to denature or retard the activity of enzymes of the meat in order to extend the shelflife of meat by preventing spoilage. Parameters such as ERV, pH and TPC were studied during meat spoilage. It appears from the present studies that autolytic changes were responsible for the ultimate spoilage of meat. When urea was applied in the meat, the microbial lag phase and the shelflife of meat were extended. It seems that urea checked the autolytic changes in meat and thereby microbial growth was delayed due to the non-availability of nutrients from the autolytic changes. 相似文献
68.
Sravani Kantipudi Lakshmi Pethakamsetty Swetha Madhavi Kollana Jhansi Rani Sunkara Pratap Kollu Narasimha Reddy Parine Muralikrishna Rallabhandi Sri Venkata Narayana Pammi 《IET nanobiotechnology / IET》2018,12(2):133
The current research study focuses on biosynthesis of silver nanoparticles (Ag NPs) for the first time from silver acetate employing methanolic root extract of Diospyros assimilis. The UV–Vis absorption spectrum of biologically synthesised nanoparticles displayed a surface plasmon peak at 428 nm indicating the formation of Ag NPs. The influence of metal ion concentration, reaction time and amount of root extract in forming Ag NPs by microscopic and spectral analysis was thoroughly investigated. Structural analysis from transmission electron microscopy confirmed the nature of metallic silver as face‐centered cubic (FCC) crystalline with an average diameter of 17 nm, which correlates with an average crystallite size (19 nm) calculated from X‐ray diffraction analysis. Further, the work was extended for the preliminary examination of antimicrobial activity of biologically synthesised Ag NPs that displayed promising activity against all the tested pathogenic strains.Inspec keywords: antibacterial activity, nanoparticles, silver, particle size, nanofabrication, nanomedicine, biomedical materials, ultraviolet spectra, visible spectra, optical microscopy, surface plasmon resonance, transmission electron microscopy, crystallites, X‐ray diffraction, microorganismsOther keywords: Diospyros assimilis root extract assisted biosynthesised silver nanoparticles, antimicrobial activity, silver acetate, methanolic root extract, UV‐visible absorption spectrum, biologically synthesised nanoparticles, surface plasmon peak, Ag NPs formation, metal ion concentration, reaction time, microscopic analysis, spectral analysis, structural analysis, transmission electron microscopy, metallic silver, FCC crystalline phase, average crystallite size, X‐ray diffraction analysis, pathogenic strains, Ag 相似文献
69.
70.
R. Govindarajan N. S. S. Narasimha Rao E. R. Altman Guang R. Gao 《International journal of parallel programming》2000,28(1):1-46
Instruction scheduling methods which use the concepts developed by the classical pipeline theory have been proposed for architectures involving deeply pipelined function units. These methods rely on the construction of state diagrams (or automatons) to (i) efficiently represent the complex resource usage pattern; and (ii) analyze legal initiation sequences, i.e., those which do not cause a structural hazard. In this paper, we propose a state-diagram based approach for modulo scheduling or software pipelining, an instruction scheduling method for loops. Our approach adapts the classical pipeline theory for modulo scheduling, and, hence, the resulting theory is called Modulo-Scheduled pipeline (MS-pipeline) theory. The state diagram, called the Modulo-Scheduled (MS) state diagram is helpful in identifying legal initiation or latency sequences, that improve the number of instructions initiated in a pipeline. An efficient method, called Co-scheduling, which uses the legal initiation sequences as guidelines for constructing software pipelined schedules has been proposed in this paper. However, the complexity of the constructed MS-state diagram limits the usefulness of our Co-scheduling method. Further analysis of the MS-pipeline theory, reveals that the space complexity of the MS-state diagram can be significantly reduced by identifying primary paths. We develop the underlying theory to establish that the reduced MS-state diagram consisting only of primary paths is complete; i.e., it retains all the useful information represented by the original state diagram as far as scheduling of operations is concerned. Our experiments show that the number of paths in the reduced state diagram is significantly lower—by 1 to 3 orders of magnitude—compared to the number of paths in the original state diagram. The reduction in the state diagram facilitate the Co-scheduling method to consider multiple initiations sequences, and hence obtain more efficient schedules. We call the resulting method, enhanced Co-scheduling. The enhanced Co-scheduling method produced efficient schedules when tested on a set of 1153 benchmark loops. Further the schedules produced by this method are significantly better than those produced by Huff's Slack Scheduling method, a competitive software pipelining method, in terms of both the initiation interval of the schedules and the time taken to construct them. 相似文献