全文获取类型
收费全文 | 226488篇 |
免费 | 18498篇 |
国内免费 | 10832篇 |
专业分类
电工技术 | 12746篇 |
技术理论 | 4篇 |
综合类 | 15080篇 |
化学工业 | 36974篇 |
金属工艺 | 12590篇 |
机械仪表 | 15013篇 |
建筑科学 | 14286篇 |
矿业工程 | 4898篇 |
能源动力 | 7384篇 |
轻工业 | 17708篇 |
水利工程 | 4278篇 |
石油天然气 | 7525篇 |
武器工业 | 1814篇 |
无线电 | 29390篇 |
一般工业技术 | 29563篇 |
冶金工业 | 11535篇 |
原子能技术 | 3212篇 |
自动化技术 | 31818篇 |
出版年
2024年 | 696篇 |
2023年 | 2641篇 |
2022年 | 5050篇 |
2021年 | 7472篇 |
2020年 | 5641篇 |
2019年 | 5077篇 |
2018年 | 5729篇 |
2017年 | 6409篇 |
2016年 | 6573篇 |
2015年 | 8091篇 |
2014年 | 11033篇 |
2013年 | 13681篇 |
2012年 | 15720篇 |
2011年 | 17706篇 |
2010年 | 15794篇 |
2009年 | 15553篇 |
2008年 | 15319篇 |
2007年 | 14356篇 |
2006年 | 13517篇 |
2005年 | 11137篇 |
2004年 | 8920篇 |
2003年 | 7754篇 |
2002年 | 8004篇 |
2001年 | 6826篇 |
2000年 | 5249篇 |
1999年 | 4006篇 |
1998年 | 3647篇 |
1997年 | 2706篇 |
1996年 | 2275篇 |
1995年 | 1787篇 |
1994年 | 1394篇 |
1993年 | 1117篇 |
1992年 | 825篇 |
1991年 | 691篇 |
1990年 | 602篇 |
1989年 | 523篇 |
1988年 | 417篇 |
1987年 | 335篇 |
1986年 | 237篇 |
1985年 | 210篇 |
1984年 | 171篇 |
1983年 | 142篇 |
1982年 | 90篇 |
1981年 | 86篇 |
1980年 | 71篇 |
1979年 | 66篇 |
1978年 | 48篇 |
1977年 | 75篇 |
1976年 | 101篇 |
1975年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Successful operation of the Synchronous Overlap and Add (SOLA) algorithm for Time Scale Modification (TSM) of speech is closely tied to the proper choice of parameters. This paper investigates the quality of time scale modified speech under different values of primary parameters. Based on Mean Opinion Score (MOS) tests and Bark Spectral Distortion (BSD) measure, the proper choices of synthesis shift (Ss) and the duration of the shift search interval (K max?) are given experimentally. The conclusions can be helpful for operating the SOLA algorithm for time scale modification of speech. 相似文献
102.
Hong Wang Rong Zeng Xiuping Li 《Microwave Theory and Techniques》2005,53(2):564-570
In this paper, RF noise in 0.18-mum NMOSFETs concerning the contribution of carrier heating and hot carrier effect is characterized and analyzed in detail via a novel approach that modulates the channel carrier heating and number of hot carriers using body bias. We confirm qualitatively a negligible role of hot carrier effect on the channel noise in deep-submicrometer MOSFETs. For a device under reverse body bias (Vb), even though the increase in hot carrier population is clearly characterized by dc measurements, the device high-frequency noise is found to be irrelevant to the increase in the channel hot carriers. Experimental results show that the high-frequency noise is slightly reduced with the increase in |Vb|, and can be qualitatively explained by secondary effects such as the suppression of nonequilibrium channel noise and substrate induced noise. The reduction of NFmin and Rn with the increase in |Vb| may provide a possible methodology to finely adjust the device high-frequency noise performance for circuit design 相似文献
103.
104.
Gyeong-Ho Kim 《Computer Methods in Applied Mechanics and Engineering》2008,198(2):234-244
A continuum-based modeling of coupled electrostatics-structure interactions is presented for the frequency computations of MEMS devices. The present general formulation of electrostatics accounting for free space is validated first by specializing it to one-dimensional uniform motion of conducting surfaces and comparing the resulting electrostatics to conventional lumped models. The general coupled electrostatics-structure interactions are then applied for the prediction of resonant frequencies of MEMS devices due to bias-voltage changes and temperature variations. Comparisons of predicted resonant frequencies obtained by the present coupled electrostatics-structure interaction models with experimental results available in the literature demonstrate that the proposed continuum-based interaction modeling yields high-confidence predictions of resonant frequencies of MEMS devices. 相似文献
105.
本文详细探讨了使用无线网络分析器调试ZigBee协议系统的基本方法,从而便于更好地确保网络的可靠性. 相似文献
106.
Jun Chen Berger T. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(8):3385-3398
We consider a distributed source coding system in which several observations must be encoded separately and communicated to the decoder by using limited transmission rate. We introduce a robust distributed coding scheme which flexibly trades off between system robustness and compression efficiency. The optimality of this coding scheme is proved for various special cases. 相似文献
107.
A 0.9 V 92 dB Double-Sampled Switched-RC Delta-Sigma Audio ADC 总被引:1,自引:0,他引:1
Min Gyu Kim Gil-Cho Ahn Hanumolu P.K. Sang-Hyeon Lee Sang-Ho Kim Seung-Bin You Jae-Whui Kim Temes G.C. Un-Ku Moon 《Solid-State Circuits, IEEE Journal of》2008,43(5):1195-1206
A 0.9 V third-order double-sampled delta-sigma audio ADC is presented. A new method using a combination of a switched-RC technique and a floating switched-capacitor double-sampling configuration enabled low-voltage operation without clock boosting or bootstrapping. A three-level quantizer with simple dynamic element matching was used to improve linearity. The prototype IC implemented in a 0.13 CMOS process achieves 92 dB DR, 91 dB SNR and 89 dB SNDR in a 24 kHz audio signal bandwidth, while consuming 1.5 mW from a 0.9 V supply. The prototype operates from 0.65 V to 1.5 V supply with minimal performance degradation. 相似文献
108.
2007年国外有机硅进展 总被引:2,自引:0,他引:2
根据2007年公开发表的相关资料,综述了2007年国外有机硅行业的市场动向、行业动向及有机硅产品的研发进展. 相似文献
109.
Nanocomposites based on poly(butylene terephthalate) (PBT) and an organoclay (Cloisite 30B) were prepared by melt blending using a twin‐screw extruder. Two kinds of PBTs, ie PBT‐A and PBT‐B, with different inherent viscosities (ηinh), were used for this study (ηinh of PBT‐A and PBT‐B were 0.74 and 1.48, respectively). Dispersion of the clay layers in the PBT nanocomposites was characterized by using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Tensile and dynamic mechanical properties and non‐isothermal crystallization temperatures of the nanocomposites were also examined. Nanocomposites based on the higher‐viscosity PBT (PBT‐B) showed a higher degree of exfoliation of the clay and a higher reinforcing effect when compared to the composites based on the lower‐viscosity PBT (PBT‐A). The clay nanolayers dispersed in PBT matrices lead to increases in the non‐isothermal crystallization temperatures of the PBTs, with such increases being more significant for the PBT‐B nanocomposites than for the PBT‐A nanoocomposites. Copyright © 2004 Society of Chemical Industry 相似文献
110.
The miscibility and phase behavior of ternary blends containing dimethylpolycarbonate (DMPC), tetramethylpolycarbonate (TMPC) and poly[styrene‐co‐(methyl methacrylate)] copolymer (SMMA) have been explored. Ternary blends containing polystyrene (PS) instead of SMMA were also examined. Blends of DMPC with SMMA copolymers (or PS) did not form miscible blends regardless of methyl methacrylate (MMA) content in copolymers. However, DMPC blends with SMMA (or PS) blends become miscible by adding TMPC. The miscible region of ternary blends is compared with the previously determined miscibility region of binary blends having the same chemical components and compositions. The region where the ternary blends are miscible is much narrower than that of binary blends. Based on lattice fluid theory, the observed phase behavior of ternary blends was analyzed. Even though the term representing the Gibbs free energy change of mixing for certain ternary blends had a negative value, blends were immiscible. It was revealed that a negative value of the Gibbs free energy change of mixing was not a sufficient condition for miscible ternary blends because of the asymmetry in the binary interactions involved in ternary blends. Copyright © 2004 Society of Chemical Industry 相似文献