全文获取类型
收费全文 | 12642篇 |
免费 | 1778篇 |
国内免费 | 1233篇 |
专业分类
电工技术 | 2495篇 |
综合类 | 1654篇 |
化学工业 | 1144篇 |
金属工艺 | 282篇 |
机械仪表 | 890篇 |
建筑科学 | 609篇 |
矿业工程 | 253篇 |
能源动力 | 400篇 |
轻工业 | 802篇 |
水利工程 | 290篇 |
石油天然气 | 392篇 |
武器工业 | 156篇 |
无线电 | 1418篇 |
一般工业技术 | 1044篇 |
冶金工业 | 234篇 |
原子能技术 | 106篇 |
自动化技术 | 3484篇 |
出版年
2024年 | 40篇 |
2023年 | 173篇 |
2022年 | 306篇 |
2021年 | 393篇 |
2020年 | 432篇 |
2019年 | 417篇 |
2018年 | 346篇 |
2017年 | 514篇 |
2016年 | 591篇 |
2015年 | 630篇 |
2014年 | 863篇 |
2013年 | 886篇 |
2012年 | 1116篇 |
2011年 | 1066篇 |
2010年 | 809篇 |
2009年 | 870篇 |
2008年 | 771篇 |
2007年 | 902篇 |
2006年 | 719篇 |
2005年 | 602篇 |
2004年 | 506篇 |
2003年 | 384篇 |
2002年 | 349篇 |
2001年 | 310篇 |
2000年 | 232篇 |
1999年 | 225篇 |
1998年 | 160篇 |
1997年 | 144篇 |
1996年 | 125篇 |
1995年 | 147篇 |
1994年 | 116篇 |
1993年 | 101篇 |
1992年 | 70篇 |
1991年 | 58篇 |
1990年 | 60篇 |
1989年 | 40篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 26篇 |
1985年 | 15篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1965年 | 2篇 |
1960年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Dr. Ying Wang Prof. Dr. Andrew Ewing 《Chembiochem : a European journal of chemical biology》2021,22(5):807-813
Exocytosis plays an essential role in the communication between cells in the nervous system. Understanding the regulation of neurotransmitter release during exocytosis and the amount of neurotransmitter content that is stored in vesicles is of importance, as it provides fundamental insights to understand how the brain works and how neurons elicit a certain behavior. In this minireview, we summarize recent progress in amperometric measurements for monitoring exocytosis in single cells and electrochemical cytometry measurements of vesicular neurotransmitter content in individual vesicles. Important steps have increased our understanding of the different mechanisms of exocytosis. Increasing evidence is firmly establishing that partial release is the primary mechanism of release in multiple cell types. 相似文献
2.
3.
4.
Polarity Effect and Electromagnetic Radiation of Partial Discharge Accompanying Growth of Electrical Tree
下载免费PDF全文
![点击此处可从《Electrical Engineering in Japan》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Tatsuya Mutakamihigashi Yoshito Kuroishi Hideki Ueno 《Electrical Engineering in Japan》2015,192(3):19-26
We have investigated the characteristics of radiated electromagnetic (EM) waves from positive and negative partial discharges (PD) in epoxy resin and cross‐linked polyethylene. We found that there is a correlation among the EM level from PD, the positive PD current, and electrical trees. Therefore, the growth of an electrical tree produces a lot of positive PD. We have also investigated the characteristics of the frequency region of EM waves from PD in air, insulating oil, and liquid epoxy in addition to the above insulators. EM waves were detected in the frequency region of 40 MHz to 300 MHz from positive and negative PD in epoxy resin and cross‐linked polyethylene. EM waves were also detected in the frequency region of 40 MHz to 150 MHz from positive and negative PD in air. In the case of insulating oil and liquid epoxy, EM waves were detected in the frequency regions of 40 MHz to 150 MHz from positive PD, and 40 MHz to 250 MHz from negative PD. The frequency region differed depending on the material and the discharge polarity. Our investigation indicates that the cause is differences in electric field strength at the time of PD occurrence. 相似文献
5.
Fresh and frozen-thawed (F-T) pork meats were classified by Vis–NIR hyperspectral imaging. Eight optimal wavelengths (624, 673, 460, 588, 583, 448, 552 and 609 nm) were selected by successive projections algorithm (SPA). The first three principal components (PCs) obtained by principal component analysis (PCA) accounted for over 99.98% of variance. Gray-level-gradient co-occurrence matrix (GLGCM) was applied to extract 45 textural features from the PC images. The correct classification rate (CCR) was employed to evaluate the performance of the partial least squares-discriminate analysis (PLS-DA) models, by using (A) the reflected spectra at full wavelengths and (B) those at the optimal wavelengths, (C) the extracted textures based on the PC images, and (D) the fused variables combining spectra at the optimal wavelengths and textures. The results showed that the best CCR of 97.73% was achieved by applying (D), confirming the high potential of textures for fresh and F-T meat discrimination. 相似文献
6.
Namyong Kim 《ETRI Journal》2006,28(2):155-161
In this paper, we introduce an escalator (ESC) algorithm based on the least squares (LS) criterion. The proposed algorithm is relatively insensitive to the eigenvalue spread ratio (ESR) of an input signal and has a faster convergence speed than the conventional ESC algorithms. This algorithm exploits the fast adaptation ability of least squares methods and the orthogonalization property of the ESC structure. From the simulation results, the proposed algorithm shows superior convergence performance. 相似文献
7.
针对车用柴油酸度等性质测定过程繁琐,采用衰减全反射样品池测定车用柴油的红外光谱,用偏最小二乘法(PLS)建立红外光谱测定车用柴油酸度、密度、闪点和凝点的4个校正模型,验证标准误差分别为0.46 mg/(100 mL),0.77kg/m3,2.60 ℃,2.77 ℃,该方法符合标准方法再现性要求。与标准方法相比,该方法具有无需预处理、操作简单、测量快速、重复性好等优点。 相似文献
8.
基于PC机群的大地电磁Occam反演并行计算研究 总被引:4,自引:0,他引:4
Occam反演以其稳定收敛和不依赖于初始模型的特性被广泛应用于大地电磁数据的处理,但偏导数矩阵的计算和拉格朗日乘子的求取导致大量的模型正演,使得反演速度较低。为此,研究了用基于PC机群的并行计算来解决这一问题的方法。首先对Occam反演方法进行了阐述;然后,分析了反演方法中各计算耗费的时间,提出对约占计算量90%的偏导数和拉格朗日乘子进行并行计算的思想,即偏导数计算采用频点计算一级的大粒度并行,拉格朗日乘子扫描和一维搜索分别采用弘值计算一级的大粒度并行和频点计算一级的小粒度并行;给出了并行计算的实现方法,即在PC机群上,利用主一从编程模式实现Occam反演的整体并行计算。在计算中,采用任务组合方式,减少了通信量,较好地实现了负载均衡。在4节点PC机群上,对应于拉格朗日乘子的扫描和一维搜索方式,整体加速比分别达到3.36和2.83。 相似文献
9.
Least squares is perhaps the most widely used technique for model fitting. In this article, we illustrate the poor performance of least squares when there are spurious values, or outliers, in a sequence of measurements. A brief overview of three well-known classes of robust alternatives to the least-squares mean is presented. For robust regression, a recent proposal called least median squares (LMS) is decribed. LMS regression is compared to least-squares regression in an example involving the estimation of optical fiber geometry. References are provided for software that is available for robust estimation techniques surveyed in this article. 相似文献
10.
心电地图仪中工频干扰的一种滤除方法 总被引:1,自引:0,他引:1
在心电地图仪中记录到的体表心电信号往往由于电磁的影响而引进工频干扰.基于体表心电信号中工频干扰的特点,作者提出了一种滤除工频干扰的方法,即就单独—胸导联信号通过提高频谱的分辨率来估计工频干扰的频率;基于最小均方误差准则来估计各导联信号中工频干扰的幅度和相位。文中还给出了该算法的流程图和滤波性能分析。模拟结果表明了该算法的有效性。应用该算法对心电地图仪中的工频干扰进行对消,取得了满意的结果。 相似文献