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101.
Multicast is a fundamental communication service in Wireless Local Area Networks (WLANs). Unfortunately, multicast packets are transmitted at the base rate needlessly, which prevents rich multimedia contents from being delivered to users. To this end, a number of prior studies have proposed to increase multicast capacity whereby an Access Point (AP) transmits at the highest data rate that can be decoded by all subscribers. Another approach is by controlling subscriber-AP associations such that a given objective, e.g., AP load, is met. Moreover, they have also proposed using relays to help boost stations with weak channel condition. In this paper, we propose an approach that exploits association control, high number of APs and relays simultaneously to improve the performance of multicast in WLANs. We show that the problem is NP-hard by reducing it from the Maximum Coverage with Group Budget (MCG) problem. We then propose a number of heuristics that consider two types of relays: non-subscribers and subscribers. The former are stations that are not part of any multicast groups whereas the latter comprise of stations that are actively receiving multicast packets. Our extensive simulation studies with varying APs, station numbers, and multicast transmission rates show the efficacy of our heuristics in reducing the average and maximum AP load, and are able to support a higher number of users at high multicast rates. Specifically, they result in up to 83% reduction in AP load, and support up to 17% and 53% more users in low and high rate multicast scenarios respectively. 相似文献
102.
103.
Abstract In this study the hydraulic characteristics and the start‐up of anaerobic rotating biological contactor (AnRBC) were investigated experimentally and theoretically. Results of tracer study showed that the AnRBC reactor is a well‐mixed reactor in the first and second stages. Start‐up of the AnRBC reactor was successfully carried out using high strength synthetic wastewaters at hydraulic retention time of 21.6 hours, organic surface loading of 111.4 g‐COD/m2?d, organic volumetric loading of 13.33 Kg‐COD/m3?d, disk rotational speed of 12 rpm and 100% disk submergence. In the steady‐state operating condition, the removal efficiencies of soluble COD and BOD could be up to 71% and 76% for the inlet COD and BOD concentrations of 12,000 and 7,267 mgL‐1, respectively. The microscopic observations after start‐up of the AnRBC reactor showed that the acetogenic bacteria are significant in the first two stages while the methanogenic bacteria predominate in the last two stages. 相似文献
104.
Abstract Two optic fiber sensing systems for temperature and voltage have been developed which utilize the mode‐mode interference of the two orthogonally polarized modes, HEx II and HEy II, in two commencal polarization‐maintaining fibers (bow‐tie and elliptical core fibers). A package of controlled programs in a Macintosh computer, which can record and process all related data automatically, is established for temperature sensing. The signal drifting problem in voltage sensings has been investigated, and the elimination of signal drifting is obtained by the phase tracking with direct current technology The agreement between the sensing results for temperature and dynamic voltage and those predicted by experimental principles is satisfactory, which confirms the validity of the developed sensing systems. 相似文献
105.
Hoi Sim Wong Tat-Jun Chin Jin Yu David Suter 《Computer Vision and Image Understanding》2013,117(12):1755-1769
In many robust model fitting methods, obtaining promising hypotheses is critical to the fitting process. However the sampling process unavoidably generates many irrelevant hypotheses, which can be an obstacle for accurate model fitting. In particular, the mode seeking based fitting methods are very sensitive to the proportion of good/bad hypotheses for fitting multi-structure data. To improve hypothesis generation for the mode seeking based fitting methods, we propose a novel sample-and-filter strategy to (1) identify and filter out bad hypotheses on-the-fly, and (2) use the remaining good hypotheses to guide the sampling to further expand the set of good hypotheses. The outcome is a small set of hypotheses with a high concentration of good hypotheses. Compared to other sampling methods, our method yields a significantly large proportion of good hypotheses, which greatly improves the accuracy of the mode seeking-based fitting methods. 相似文献
106.
Chin‐San Wu 《Polymer International》2012,61(10):1556-1563
Poly(butylene adipate‐co‐terephthalate) (PBAT) composites containing polyaniline (PANI) were prepared using a melt blending process. Acrylic‐acid‐grafted PBAT (PBAT‐g‐AA) and PANI were used to improve the compatibility and dispersibility of PANI within the PBAT matrix. The composites were characterised morphologically using scanning electron microscopy, chemically using Fourier transform IR spectrometry and 13C solid‐state nuclear magnetic resonance, and optically using UV‐visible spectroscopy. The electrical conductivity of the composites was also evaluated with a resistance tester and a cyclic voltameter. Escherichia coli (BCRC 10239) was chosen as the standard bacterium for determining the antibacterial properties of the composite materials. The anti‐static properties of the composites were also evaluated. The PBAT‐g‐AA/PANI composite showed markedly enhanced antibacterial and anti‐static properties due to the formation of amide bonds by the condensation of the carboxylic acid groups of PBAT‐g‐AA with the amino groups of PANI. The optimal level of PANI was 9 wt%, as excess PANI led to separation of the two organic phases, lowering their compatibility. Copyright © 2012 Society of Chemical Industry 相似文献
107.
ABSTRACTValue in collaborative design research and practice can be understood fundamentally as relationships, materials, processes, contexts, and outcomes that are subjects of and for negotiation. We argue for conceptions of value that move beyond traditional ‘outcomes’ based measurements to reimagine and rearticulate value itself as co-created, emerging from negotiation, relationality and immersion in specific contexts. These understandings of value, we argue, are not rooted in or always knowable through designers’ experiences, even as designers participate in creating them. Using case studies from our research we suggest that value in design collaboration emerges as a question: value to whom, and to what end? We propose that addressing these questions ethically through co-design requires actively engaged, grounded work with collaborators based in three principles: being present for the work, participant making, and co-creating capacity for collaborators to ‘go off and do their thing’. 相似文献
108.
Chin‐Jung Chao Gavriel Salvendy 《International journal of human-computer interaction》2013,29(3):221-233
Knowledge elidtation is an expensive and vital part in the construction of knowledge‐based systems. This paper indicates that the acquisition of procedural knowledge can significantly be improved, depending on the tasks (interpretation, debugging, or diagnosis) for which the knowledge is elicited; the method of knowledge elicitation (protocol, interview, induction, or repertory grid), and the number of experts (from one to six) from whom knowledge is elicited. On average, for all conditions the percentage of acquired procedural knowledge increased by two‐fold from using one to six experts. The optimal cost‐benefit utility may be achieved by using three experts for knowledge elicitation. 相似文献
109.
Assessing all pertinent environmental variables to categorize a skill level to safely navigate the water environment can be difficult for inexperienced kayakers, especially at a remote site where internet access is limited. A real-time kayaker safety assessment of water environmental conditions at the Mainland Sea Caves of the Apostle Islands National Lakeshore, Lake Superior is achieved. We present a new cyberinfrastructure that provides kayakers with real-time data access and a Safety Index (SI) with consideration of multiple environmental factors to characterize the degree of navigational difficulty for classifying kayaker skill levels. Specifically, radar reflectivity is added to improve forecasts of dangerous conditions caused by convective storms using state-of-the-art weather and wave modeling. Spectral characteristics of surface waves are employed to correlate the occurrences of extreme and freak waves. In addition, unexpectedly dangerous conditions like coastal upwelling and freak wave occurrence due to changing wind directions are considered. A contingency plan is implemented to handle the issue of possibly missing required environmental data. Display of the SI and visualization of other real-time environmental data are communicated by a power-efficient kiosk. Web analytics demonstrates a public interest in real-time water conditions and the need for the on-site kiosk to provide the latest information before kayakers enter the water. The new real-time water environment cyberinfrastructure for kayaker safety in the Apostle Islands, Lake Superior has been successfully operated since 2014. 相似文献
110.
Mengjiao Li Feng-Shou Yang Hung-Chang Hsu Wan-Hsin Chen Chia Nung Kuo Jiann-Yeu Chen Shao-Heng Yang Ting-Hsun Yang Che-Yi Lin Yi Chou Mu-Pai Lee Yuan-Ming Chang Yung-Cheng Yang Ko-Chun Lee Yi-Chia Chou Chen-Hsin Lien Chun-Liang Lin Ya-Ping Chiu Chin Shan Lue Shu-Ping Lin Yen-Fu Lin 《Advanced functional materials》2021,31(5):2007587
Defect engineering represents a significant approach for atomically thick 2D semiconductor material development to explore the unique material properties and functions. Doping-induced conversion of conductive polarity is particularly beneficial for optimizing the integration of layered electronics. Here, controllable doping behavior in palladium diselenide (PdSe2) transistor is demonstrated by manipulating its adatom-vacancy groups. The underlying mechanisms, which originate from reversible adsorption/desorption of oxygen clusters near selenide vacancy defects, are investigated systematically via their dynamic charge transfer characteristics and scanning tunneling microscope analysis. The modulated doping effect allows the PdSe2 transistor to emulate the essential characteristics of photo nociceptor on a device level, including firing signal threshold and sensitization. Interestingly, electrostatic gating, acting as a neuromodulator, can regulate the adaptive modes in nociceptor to improve its adaptability and perceptibility to handle different danger levels. An integrated artificial nociceptor array is also designed to execute unique image processing functions, which suggests a new perspective for extension of the promise of defect engineered 2D electronics in simplified sensory systems toward use in advanced humanoid robots and artificial visual sensors. 相似文献