全文获取类型
收费全文 | 56855篇 |
免费 | 3571篇 |
国内免费 | 1045篇 |
专业分类
电工技术 | 1782篇 |
技术理论 | 4篇 |
综合类 | 1579篇 |
化学工业 | 11001篇 |
金属工艺 | 2425篇 |
机械仪表 | 2985篇 |
建筑科学 | 2121篇 |
矿业工程 | 773篇 |
能源动力 | 2067篇 |
轻工业 | 4043篇 |
水利工程 | 536篇 |
石油天然气 | 1025篇 |
武器工业 | 146篇 |
无线电 | 9060篇 |
一般工业技术 | 9664篇 |
冶金工业 | 4259篇 |
原子能技术 | 666篇 |
自动化技术 | 7335篇 |
出版年
2024年 | 128篇 |
2023年 | 724篇 |
2022年 | 1247篇 |
2021年 | 1871篇 |
2020年 | 1397篇 |
2019年 | 1288篇 |
2018年 | 1594篇 |
2017年 | 1588篇 |
2016年 | 1638篇 |
2015年 | 1679篇 |
2014年 | 2353篇 |
2013年 | 3506篇 |
2012年 | 3446篇 |
2011年 | 4106篇 |
2010年 | 3145篇 |
2009年 | 3218篇 |
2008年 | 3126篇 |
2007年 | 2680篇 |
2006年 | 2352篇 |
2005年 | 1942篇 |
2004年 | 1750篇 |
2003年 | 1769篇 |
2002年 | 1984篇 |
2001年 | 1691篇 |
2000年 | 1255篇 |
1999年 | 1133篇 |
1998年 | 1669篇 |
1997年 | 1106篇 |
1996年 | 976篇 |
1995年 | 738篇 |
1994年 | 561篇 |
1993年 | 481篇 |
1992年 | 363篇 |
1991年 | 328篇 |
1990年 | 299篇 |
1989年 | 288篇 |
1988年 | 248篇 |
1987年 | 217篇 |
1986年 | 184篇 |
1985年 | 172篇 |
1984年 | 146篇 |
1983年 | 103篇 |
1982年 | 101篇 |
1981年 | 85篇 |
1980年 | 111篇 |
1979年 | 63篇 |
1978年 | 65篇 |
1977年 | 80篇 |
1976年 | 110篇 |
1975年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
RM Bionta G Blewitt CB Bratton D Casper A Ciocio R Claus M Crouch ST Dye S Errede GW Foster W Gajewski KS Ganezer M Goldhaber TJ Haines TW Jones D Kielczewska WR Kropp JG Learned JM LoSecco J Matthews HS Park LR Price F Reines J Schulz S Seidel E Shumard D Sinclair HW Sobel JL Stone L Sulak R Svoboda G Thornton van der Velde JC C Wuest 《Canadian Metallurgical Quarterly》1987,36(1):30-36
82.
QRS feature extraction using linear prediction 总被引:10,自引:0,他引:10
This communication proposes a method called linear prediction (a high performant technique in digital speech processing) for analyzing digital ECG signals. There are several significant properties indicating that ECG signals have an important feature in the residual error signal obtained after processing by Durbin's linear prediction algorithm. This communication also indicates that the prediction order need not be more than two for fast arrhythmia detection. The ECG signal classification puts an emphasis on the residual error signal. For each ECG's QRS complex, the feature for recognition is obtained from a nonlinear transformation which transforms every residual error signal to a set of three states pulse-code train relative to the original ECG signal. The pulse-code train has the advantage of easy implementation in digital hardware circuits to achieve automated ECG diagnosis. The algorithm performs very well in feature extraction in arrhythmia detection. Using this method, our studies indicate that the PVC (premature ventricular contraction) detection has at least a 92 percent sensitivity for MIT/BIH arrhythmia database. 相似文献
83.
Characterisation of a BioFET for detection of albumin in a mixture of human urine is presented. To avoid electrolyte effect of the urine, it was measured in PBS (phosphate buffer saline) at a fixed pH after albumin binding. The drain current was modulated by the albumin bound to the anti-albumin immobilised on the gate surface of the BioFET. The current variation ratio was likely to be proportional to the concentration of the albumin in the range 50-250 mg/1. The results show the feasibility of the BioFET as a urinary albumin sensor. 相似文献
84.
85.
Sang C. Park 《The Visual computer》2003,19(1):38-49
A sweeping operation called polygonal extrusion is defined to improve the modeling power of CSG-based modeling. It is assumed that a 2D cross-sectional polygon (sweeping
polygon) moves in space while its containing plane is kept orthogonal to the tangent direction of the trajectory curve, a planar
polygonal chain having no self-intersections. The objective of the paper is to compute the boundary of the swept volume of
the sweeping polygon as a set of polygons (or triangles). The most significant challenge to accomplishing this objective is
the problem of trimming the swept volume. To solve the trimming problem, 2D-curve offsetting methods are employed. Two algorithms
are presented for polygonal extrusion that are based on different offsetting methods, the Voronoi diagram and PWID offset.
The proposed algorithms have been implemented and tested with various examples.
Published online: 28 January 2003 相似文献
86.
Joon C. Park Author Vitae Author Vitae 《Computer aided design》2003,35(9):807-812
Presented in this paper is a topology reconstruction algorithm from a set of unorganized trimmed surfaces. Error-prone small geometric elements are handled to give proper topological information. It gives complete topology to topologically complete models, and it is also tolerant to incomplete models. The proposed algorithm is vertex-based in that clues for topological information are searched from the set of vertices first, not from that of edges. 相似文献
87.
Effects of austenitizing treatment temperatures on aqueous corrosion properties of martensitic stainless steels were investigated by electrochemical tests (potentiodynamic test, potentiostatic test and electrochemical impedance spectroscopy), and surface analyses (optical microscopy and XRD). The results of potentiodynamic test revealed that the breakdown potential increased with the increased austenitizing temperature, indicating increased relative resistance to initiation of localized corrosion. EIS measurements showed that MSS3 (1030 °C) exhibits larger polarization resistance value than MSS1 (970 °C) and MSS2 (1000 °C) at passive and breakdown states. This was caused by decreasing the amount of Cr-rich M23C6 carbide which acts as preferential sites for pitting corrosion. 相似文献
88.
Wei-Jun Liu Wei-Dong He Xue-Wu Ge Hua-Rong Liu Mo-Zheng Wang Zheng-Qi Chang 《Materials Letters》2007,61(13):2818-2821
Interfacial-initiated polymerization of styrene (St) was carried out in inversed emulsion with cumene hydroperoxide (CHPO) and ferrous sulfate (FeSO4)/disodium ethylenediaminetetraacetate (NaEDTA)/sodium formaldehyde sulfoxylate (SFS) as the redox initiation system. The water-soluble Fe2+-NaEDTA-SFS acted as the reducing component and the oil-soluble CHPO as the oxidant component of the redox initiation system. Therefore, the primary radicals were produced mainly at the oil/water interface to initiate the polymerization of St. Thus, sub-micrometer hollow polystyrene (PSt) spheres were obtained by one-stage polymerization, which was supported by the techniques of transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). 相似文献
89.
Sanghyun Ju Jianye Li Pimparkar N. Alam M.A. Chang R.P.H. Janes D.B. 《Nanotechnology, IEEE Transactions on》2007,6(3):390-395
Nanorod field-effect transistors (FETs) that use multiple Mg-doped ZnO nanorods and a SiO2 gate insulator were fabricated and characterized. The use of multiple nanorods provides higher on-currents without significant degradation in threshold voltage shift and subthreshold slopes. It has been observed that the on-currents of the multiple ZnO nanorod FETs increase approximately linearly with the number of nanorods, with on-currents of ~1 muA per nanorod and little change in off-current (~4times10-12). The subthreshold slopes and on-off ratios typically improve as the number of nanorods within the device channel is increased, reflecting good uniformity of properties from nanorod to nanorod. It is expected that Mg dopants contribute to high n-type semiconductor characteristics during ZnO nanorod growth. For comparison, nonintentionally doped ZnO nanorod FETs are fabricated, and show low conductivity to compare with Mg-doped ZnO nanorods. In addition, temperature-dependent current-voltage characteristics of single ZnO nanorod FETs indicate that the activation energy of the drain current is very low (0.05-0.16 eV) at gate voltages both above and below threshold 相似文献
90.
This paper presents an application of digital signal processing to data acquired by the radio imaging method (RIM) that was adopted to measure moisture distribution inside the human body. RIM was originally developed for the mining industry; we are applying the method to a biomedical measurement because of its simplicity, economy, and safety. When a two‐dimensional image was constructed from the measured data, the method provided insufficient resolution because the wavelength of the measurement medium, a weak electromagnetic wave in a VHF band, was longer than human tissues. We built and measured a phantom, a model simulating the human body, consisting of two water tanks representing large internal organs. A digital equalizer was applied to the measured values as a weight function, and images were reconstructed that corresponded to the original shape of the two water tanks. As a result, a two‐dimensional image containing two individual peaks corresponding to the original two small water tanks was constructed. The result suggests the method was applicable to biomedical measurement by the assistance of digital signal processing. This technique may be applicable to home‐based medical care and other situations in which safety, simplicity, and economy are important. 相似文献