全文获取类型
收费全文 | 85911篇 |
免费 | 6832篇 |
国内免费 | 3603篇 |
专业分类
电工技术 | 4261篇 |
技术理论 | 11篇 |
综合类 | 4940篇 |
化学工业 | 14700篇 |
金属工艺 | 4734篇 |
机械仪表 | 5105篇 |
建筑科学 | 6985篇 |
矿业工程 | 2292篇 |
能源动力 | 2543篇 |
轻工业 | 5854篇 |
水利工程 | 1437篇 |
石油天然气 | 4899篇 |
武器工业 | 640篇 |
无线电 | 9853篇 |
一般工业技术 | 11049篇 |
冶金工业 | 5431篇 |
原子能技术 | 948篇 |
自动化技术 | 10664篇 |
出版年
2024年 | 349篇 |
2023年 | 1420篇 |
2022年 | 2572篇 |
2021年 | 3416篇 |
2020年 | 2622篇 |
2019年 | 2220篇 |
2018年 | 2430篇 |
2017年 | 2828篇 |
2016年 | 2524篇 |
2015年 | 3320篇 |
2014年 | 4143篇 |
2013年 | 4903篇 |
2012年 | 5380篇 |
2011年 | 5705篇 |
2010年 | 4912篇 |
2009年 | 4660篇 |
2008年 | 4518篇 |
2007年 | 4421篇 |
2006年 | 4545篇 |
2005年 | 3902篇 |
2004年 | 2693篇 |
2003年 | 2343篇 |
2002年 | 2255篇 |
2001年 | 2053篇 |
2000年 | 1992篇 |
1999年 | 2268篇 |
1998年 | 2306篇 |
1997年 | 1859篇 |
1996年 | 1674篇 |
1995年 | 1244篇 |
1994年 | 1165篇 |
1993年 | 841篇 |
1992年 | 605篇 |
1991年 | 479篇 |
1990年 | 382篇 |
1989年 | 301篇 |
1988年 | 268篇 |
1987年 | 182篇 |
1986年 | 127篇 |
1985年 | 108篇 |
1984年 | 62篇 |
1983年 | 55篇 |
1982年 | 58篇 |
1981年 | 62篇 |
1980年 | 34篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1977年 | 28篇 |
1976年 | 33篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
介绍一种新型光纤燃煤炉火焰检测器,阐述其系统组成及特点,并提出了基于模糊推理的多信号融合处理方法。 相似文献
92.
93.
变长线扫描选择性激光烧结快速成型工艺的质量和效率优势分析 总被引:1,自引:0,他引:1
本文分析变长线扫描选择性激光烧结快速成型工艺对点扫描工艺的质量和效率优势.对二者光学系统结构作分析对比,对焦斑和线束上的功率密度作计算对比.变长线扫描系统采用的扫描方式和聚焦元件使线束宽度小且恒定,线束功率密度与点扫描焦斑的相当.变长线扫描选择性激光烧结快速成型工艺的质量优势是明显的,效率比点扫描工艺提高一倍左右. 相似文献
94.
Oleg A. Mezentsev Rixin Zhu Richard E. DeVor Shiv G. Kapoor William A. Kline 《International Journal of Machine Tools and Manufacture》2002,42(4)
A model-based method for fault detection in tapping based on torque and radial forces is proposed. The method allows the identification of faults typical of a tapping operation including axial misalignment, tap runout, tooth breakage both singly and together. The validation experiments have been run on aluminum 356 workpieces for different combinations of process faults. Results have shown that the model predictions are in good agreement with the experimental radial force and torque signals under various fault conditions. 相似文献
95.
纳米技术与“纳米涂料”之我见 总被引:11,自引:0,他引:11
概述了纳米技术、纳米材料、“纳米涂料”的现状 ,重点讨论了纳米技术在涂料中应用遇到的问题和建议措施 ,对纳米技术的科研方向及其在涂料中应用的发展提出了看法。 相似文献
96.
97.
A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry 相似文献
98.
An approximate model of coupled Markov chains is proposed and analyzed for a slotted ALOHA system with a finite number of buffered nodes. This model differs from earlier ones in that it attempts to capture the interdependence between the nodes. The analytical results lead to a set of equations that, when solved numerically, yield the average packet delay. Comparison between computational and simulation results for a small number of nodes show excellent agreement for most throughput values, except for values near saturation. Numerical comparisons for a two-node system show that a nonsymmetric loading of the system provides better delay-throughput performance than a symmetric one. 相似文献
99.
Zhibin Xiong Haitao Liu Chunxiang Zhu Sin J.K.O. 《Electron Devices, IEEE Transactions on》2005,52(12):2629-2633
In this paper, a new polysilicon CMOS self-aligned double-gate thin-film transistor (SA-DG TFT) technology is proposed and experimentally demonstrated. The self-alignment between the top- and bottom-gate is realized by a backlight exposure technique. The structure has an ultrathin channel region (300 /spl Aring/) and a thick source/drain region. Experimental results show that this technology provides excellent current saturation due to a combination of the effective reduction in the drain field and the full depletion of the ultrathin channel. Moreover, for n-channel devices, the SA-DG TFT has a 4.2 times higher on-current (V/sub gs/=20V) as compared to the conventional single-gate TFT. Whereas for the p-channel devices, the SADG TFT has a 3.6 times higher on-current (V/sub gs/=-20V) compared to the conventional single-gate device. 相似文献
100.
A subspace detection method of analog space-time codes for multiantenna ultra-wideband transmissions
Xiantao Cheng Weile Zhu 《Communications Letters, IEEE》2005,9(6):493-495
In this letter, we propose a subspace based detection method for space-time block codes (STBC) wedded with ultra-wideband (UWB) transmissions. Without the need of channel information, the proposed algorithm yields the estimation of transmitted symbols by minimizing some quadratic form built on the orthogonality between signal and noise subspaces. Simulations in flat-faded application scenarios show that the subspace method can achieve the same diversity and a loss of about 2 dB at the 10/sup -3/ level with more than four successive space-time codes being decoded jointly, compared to the coherent decoding algorithm. 相似文献