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991.
隔震技术能有效减小核电厂上部结构的加速度响应,但强地震作用下隔震层位移过大会导致管道断裂。本文基于曲面运动原理及预压弹簧伸缩特性提出了一种负刚度阻尼系统,通过球铰在拱球面曲线运动实现负刚度特性,并在弹簧压缩方向提供黏滞阻尼性能。提出了负刚度系统的理论恢复力模型并进行了力学特性分析,设计了负刚度装置并完成了静力试验,结果显示理论恢复力模型与试验结果的一致性较理想。将核电厂负刚度阻尼隔震结构与核电厂隔震结构进行了地震响应对比分析,比较了不同地震波输入下的地震响应。结果表明负刚度阻尼系统可有效同时减小核电厂上部加速度响应和隔震层位移响应。 相似文献
992.
The present study concentrates on design, commissioning and calibration of a uniaxial laminar soil box suitable for use on a low base-shear capacity shake table available at IIT Kanpur, India. The box is designed to simulate the behavior of soil deposits subjected to earthquake motions, with minimal boundary effects due to reflection of waves at the boundary. The 1.1 m × 1.6 m × 0.765 m box is comprised of a series of individual lamina supported independently on multiple roller bearings guided through a guide channel. The outer frame connected to the guide rods is designed in such as way that it can transfer the self weight of each lamina out of the shake table. A series of free-field tests are carried out on dry Ganga sand sample to calibrate the box. Dynamic response parameters, such as acceleration, displacement, stress-strain behavior, strain-dependant modulus and damping ratio of the sand at various depth are investigated. Large strain and subsequent increased inelasticity is observed towards the top of the sand bed. The experimental results are further compared with equivalent-linear SHAKE analysis and nonlinear finite element ground response analysis of the free-field soil using OpenSees for assessing the performance of the laminar box. 相似文献
993.
Present paper reports the synthesis of CuO–SnO2 nanocomposite via sol–gel route as a sensing material for a liquefied petroleum gas (LPG). X-ray diffraction analysis confirmed the formation of CuO–SnO2 nanocomposite. Crystallite size was found 5 nm. The optical band gap of the nanocomposite was found 4.1 eV. The thin/thick films were fabricated using spin coating and screen printing technology respectively and investigated with the exposition of LPG at room temperature (25 °C). Surface morphology of the thin film exhibits that it has a number of gas adsorption sites. The sensitivities of the thick and thin film sensors were found 4.1 and 42 respectively. The response and recovery times of the fabricated film sensor were 180 and 200 s respectively. Maximum sensor response of thin film sensor was found 4100. Better sensitivity and percentage sensor response, small response and recovery times, and good reproducibility and stability recognize the fabricated thin film of CuO–SnO2 as a challenging material for the detection of LPG. 相似文献
994.
Chi‐Wu Mao 《中国工程学刊》2013,36(3):179-185
Abstract A special method has been found and used for the rapid finding of the contours in a natural image. A reference contour image was thus formed by a subjective test. The reference contour image can be further adopted as an objective criterion for other contour‐finding algorithms. 相似文献
995.
Measuring the dynamics of a machine tool is important for improving its processing or design. In general, the dynamics of the machine tool structure is identified by the experimental modal analysis approaches that require the measurement of both the input loadings and the corresponding structural responses. However, the primary limitation for this method is that the input loadings are difficult or impossible to be measured when the machine tool is under operational conditions. In this paper, a method that is based on random decrement technology was used to identify the operational modal parameters of a machine tool without the knowledge of any of the inputs. To estimate the frequency response functions, FRFs, a structural change method was proposed. The approach is based on the sensitivity of the eigenproperties to structural modifications caused by the drive positions. The proposed method was verified experimentally by traditional hammer tests. Because no elaborate excitation equipment is used, the dynamics of the machine tool structure with arbitrarily feed rate or working position can be easily identified using the proposed active excitation modal analysis method. 相似文献
996.
Diagnosis Criterion of Abnormality of Transformer Winding by Frequency Response Analysis (FRA) 下载免费PDF全文
SATORU MIYAZAKI YOSHINOBU MIZUTANI AKIRA TAGUCHI JUNICHI MURAKAMI NAOKAZU TSUJI MASAHIRO TAKASHIMA OSAMU KATO 《Electrical Engineering in Japan》2017,201(3):25-34
Frequency response analysis (FRA) is a powerful technique to detect internal abnormalities within power transformers. However, diagnosis criteria of power transformers by FRA have not been fully established yet. In this paper, a new evaluation method of degree of identification between two transfer functions is proposed. In the proposed method, a frequency window is employed and cross‐correlation factor is calculated with moving the window. Furthermore, the proposed method is applied to transfer functions of real transformers with or without some abnormalities. Based on this discussion, objective criteria for diagnosis of abnormalities of transformer windings by FRA are proposed. The proposed criteria are based on a few data of transformers with some abnormalities. Therefore, the proposed criteria are tentative and they would be improved by accumulation of further data. 相似文献
997.
Umar-Faruq Cajee Rodney Hull Monde Ntwasa 《International journal of molecular sciences》2012,13(9):11804-11831
Ubiquitin-like proteins (Ubls) confer diverse functions on their target proteins. The modified proteins are involved in various biological processes, including DNA replication, signal transduction, cell cycle control, embryogenesis, cytoskeletal regulation, metabolism, stress response, homeostasis and mRNA processing. Modifiers such as SUMO, ATG12, ISG15, FAT10, URM1, and UFM have been shown to modify proteins thus conferring functions related to programmed cell death, autophagy and regulation of the immune system. Putative modifiers such as Domain With No Name (DWNN) have been identified in recent times but not fully characterized. In this review, we focus on cellular processes involving human Ubls and their targets. We review current progress in targeting these modifiers for drug design strategies. 相似文献
998.
The role of the interface on the deformation response in scratch tests of epoxy-polyester films deposited by electrostatic spraying is investigated. A comparative study of the scratch deformation behaviour of films deposited on micro- and macro-corrugated rigid substrates and on ‘soft’ silicon sub-layers is made. Scratch deformation parameters were evaluated by contact gauge inductive profilometry, whilst morphological examinations of the residual scratch patterns were performed by electron microscopy. 相似文献
999.
Kim G Clarke Musaida M Manyuchi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(11):1615-1618
Accurate quantification of the overall volumetric oxygen transfer coefficient (KLa) is essential for the success of aerobic bioprocesses. In hydrocarbon‐based bioprocesses where KLa is depressed at higher viscosities, this is particularly critical. In this study an accessible methodology for KLa determination has been developed and validated for alkane‐based systems under a wide range of process conditions. Critical to measurement accuracy in around 90% of the KLa values was the incorporation of the response lag. Neglect of the response lag resulted in errors greater than 5% above KLa = 0.3Kp to KLa = 0.6Kp (where Kp is the inverse response lag or probe constant), at least 1.5‐fold to 3‐fold lower than the analogous KLa in water. Further, Kp varied significantly with both alkane concentration and chain length. A sensitivity analysis confirmed ? 25% to 90% error in KLa with 30% over‐ and under‐estimation of Kp respectively. When incorporating Kp values specific to the process conditions, accurate KLa values were confirmed in 0 to 20% (v/v) C10–13 and C14–20 aqueous dispersions over 600 to 1200 rpm agitation. Copyright © 2012 Society of Chemical Industry 相似文献
1000.
《技术计量学》2013,55(4):520-521
A simple heuristic is proposed for constructing robust experimental designs for multivariate generalized linear models. The method is based on clustering a set of local optimal designs. A method for finding local D-optimal designs using available resources is also introduced. Clustering, with its simplicity and minimal computation needs, is demonstrated to outperform more complex and sophisticated methods. 相似文献