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排序方式: 共有374条查询结果,搜索用时 15 毫秒
31.
动态电能质量波形辨识的暂态分析方法(Ⅱ) 总被引:2,自引:1,他引:2
利用先进的数学分析工具,提出全新的动态电能质量扰动波形的辨识方法。利用小波与分形的内在联系,从小波变换后的系数中,提取扰动的全局分形指数和局部分形指数作为动态电能质量扰动的特征,建立了识别扰动类型的分形指数小波分析方法。利用多刻度数学形态学由粗到细地对信号进行分层处理的特点,从动态电能质量扰动的波形出发,建立一种全新的多层次描述和多层次处理的扰动辨识方法。对由PSCAD/EMTDC软件仿真得到的12种典型动态电能质量扰动波形的识别,证明了其正确性。该方法为动态电能质量扰动的检测、识别与分类提供了新的思路。 相似文献
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Recent studies of Escherichia coli thymidylate synthase (ecTSase) showed that a highly conserved residue, Y209, that is located 8 Å away from the reaction site, plays a key role in the protein’s dynamics. Those crystallographic studies indicated that Y209W mutant is a structurally identical but dynamically altered relative to the wild type (WT) enzyme, and that its turnover catalytic rate governed by a slow hydride-transfer has been affected. The most challenging test of an examination of a fast chemical conversion that precedes the rate-limiting step has been achieved here. The physical nature of both fast and slow C-H bond activations have been compared between the WT and mutant by means of observed and intrinsic kinetic isotope effects (KIEs) and their temperature dependence. The findings indicate that the proton abstraction step has not been altered as much as the hydride transfer step. Additionally, the comparison indicated that other kinetic steps in the TSase catalyzed reaction were substantially affected, including the order of the substrate binding. Enigmatically, although Y209 is H-bonded to 3''-OH of 2''-deoxyuridine-5''-monophosphate (dUMP), its altered dynamics is more pronounced on the binding of the remote cofactor, (6R)-N5,N10-methylene-5,6,7,8-tetrahydrofolate (CH2H4folate), revealing the importance of long-range dynamics of the enzymatic complex and its catalytic function. 相似文献
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传动系统是双馈风电机组的重要组成部分,其模型对电力系统同步稳定及频率稳定分析具有重要影响,准确的传动系统模型参数是分析新能源电力系统动态特性的前提。为解决因大扰动量测信息不充裕导致模型参数难以辨识的困难,提出利用机组正常运行状态时随机小扰动激励下丰富的历史响应数据,根据响应数据与模型参数的对应关系构建神经网络模型,并根据当前响应数据进行驱动系统模型参数预测。首先讨论了基于BP神经网络进行数据建模的基本流程;针对含双馈风电机组的无穷大系统仿真算例,提取随机风速扰动下响应信号受扰轨迹的功率谱特征;定义功率谱灵敏度指标,提出选取功率谱灵敏度较大的参数作为重点参数;最后基于BP神经网络构建响应信号功率谱与模型参数之间的非线性映射,基于训练得到的BP网络辨识新响应下的模型参数。通过分析BP神经网络动态模型的误差,验证数据驱动建模方法的可行性。
相似文献35.
Wind power has emerged as the most promising option for providing sustainable eco-friendly power supply to the modern world. Due to its unpredictable nature, integration of wind power into the conventional power grid is a very challenging task having dynamic characteristics. Due to the inherent uncertainty associated with wind availability, additional spinning reserve needs to be scheduled in order to maintain security and supply reliability. Multi-period multi-objective optimal dispatch (MPMOOD) is presented for wind integrated power system with reserve constraints. The complex relationship between wind power availability, spinning reserve allocation and their impact on economic/environmental cost are analysed using an elaborate model.A new multi-objective Series PSO-DE (SPSO-DE) hybrid algorithm is proposed where the two paradigms, differential evolution (DE) and particle swarm optimization (PSO) share domain information and maintain a synergistic cooperation to overcome their individual weaknesses. For multi-objective (MO) problems, the selection operation in SPSO-DE is replaced by a 5-class time-varying fuzzy selection mechanism (TVFSM) to avoid saturation and to increase Pareto diversity. To promote convergence towards the central part of the Pareto front and to quickly isolate the boundary solutions, Guassian membership function is employed. Elitism is applied to preserve good solutions and momentum operation is used to stop premature convergence. The proposed method expedites the search for the best solution, i.e. the solution which satisfies all the objectives of the MO problems. To test the performance and computational efficiency, the proposed method is applied on two standard test power systems. 相似文献
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In an effort to evaluate the selective control of the exotic weed Eurasian water milfoil (Myriophyllum spicatum L.) and to assess the recovery and restoration of the native submersed plant community, a 6-ha river and 4-ha cove plot were treated with the herbicide triclopyr at application rates of 2·5 and 1·75 mg/l, respectively, in the Pend Oreille River, WA, in August 1991. Water exchange half-lives within the plots were measured using rhodamine WT dye (river, t1/2=20 h; cove, t1/2=52 h), and triclopyr dissipation rates were also calculated (river, t1/2=19 h); cove, t1/2=53 h). Triclopyr concentrations were below the proposed potable water tolerance level (0·5 mg/l) within the river treatment plot by 3 days after treatment (<0·01 to 0·41 mg/l), and 675 m downstream of that plot by 1 day after treatment (<0·01 to 0·47 mg/l). Following the cove treatment, triclopyr residues ranged from 0·12 to 0·29 mg/l by 7 days after treatment, and from<0·01 to 0·06 mg/l as close as 150 m downstream from the plot. Eurasian water milfoil biomass was reduced by 99% in the treated plots at 4 weeks post-treatment, remained low one year later (river treatment, 28% of pretreat levels; cove treatment 1% of pre-treat levels) and was still at acceptable levels of control at two years post-treatment (river treatment, 47% of pre-treat levels; cove treatment, 24% of pre-treat levels). The four-week post-treatment efficacy results verified triclopyr concentration/exposure time relationships for controlling Eurasian water milfoil developed under laboratory conditions. Non-target native plant biomass increased 500–1000% by one year post-treatment, and remained significantly higher in the cove plot at two years after treatment. Native species diversity doubled following herbicide treatment, and the restoration of this robust community delayed the re-establishment and dominance of Eurasian water milfoil for three growing seasons. ©1997 John Wiley & Sons, Ltd. 相似文献
37.
Cheng Yinglei Zhao Rongchun Hu Fuyuan Li Ying 《电子科学学刊(英文版)》2006,23(2):314-317
In order to enhance the image information from multi-sensor and to improve the abilities of the information analysis and the feature extraction, this letter proposed a new fusion approach in pixel level by means of the Wavelet Packet Transform (WPT). The WPT is able to decompose an image into low frequency band and high frequency band in higher scale. It offers a more precise method for image analysis than Wavelet Transform (WT). Firstly, the proposed approach employs HIS (Hue, Intensity, Saturation) transform to obtain the intensity component of CBERS (China-Brazil Earth Resource Satellite) multi-spectral image. Then WPT transform is employed to decompose the intensity component and SPOT (Systeme Pour I'Observation de la Therre ) image into low frequency band and high frequency band in three levels. Next, two high frequency coefficients and low frequency coefficients of the images are combined by linear weighting strategies. Finally, the fused image is obtained with inverse WPT and inverse HIS. The results show the new approach can fuse details of input image successfully, and thereby can obtain a more satisfactory result than that of HM (Histogram Matched)-based fusion algorithm and WT-based fusion approach. 相似文献
38.
原油气相色谱指纹可配比性实验研究 总被引:11,自引:2,他引:9
气相色谱分离技术能有效地对混合物中不同痕量的化合物进行分离并对不同组分进行定量.根据油(气)井生产过程建立混采油井化学模型,采用GC和GC/MS实验分析技术,选择大港油田某断块原油进行气相色谱指纹化合物可配比性实验和化学模拟.结果表明:并非所有色谱指纹化合物都具有可配比性,指纹化合物的可配比性不但取决于生成原油的地质背景,而且还与原油组分的性质、浓度以及色谱分析的分离度和定量方法等因素有关.应用具有可配比性的原油色谱指纹,可以定量模拟混采井生产过程中不同单层的贡献率,并对油藏进行动态监测管理.实验研究结果还可以进一步推广到多油源区不同烃源岩对油藏储量贡献率的模拟计算,寻找有效烃源岩及主要运移路径,确定最佳勘探目标区;同时该技术还有望用来解决环境污染动态监测的技术问题. 相似文献
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