全文获取类型
| 收费全文 | 47217篇 |
| 免费 | 9105篇 |
| 国内免费 | 4669篇 |
专业分类
| 电工技术 | 1875篇 |
| 综合类 | 5496篇 |
| 化学工业 | 922篇 |
| 金属工艺 | 797篇 |
| 机械仪表 | 3947篇 |
| 建筑科学 | 1175篇 |
| 矿业工程 | 585篇 |
| 能源动力 | 304篇 |
| 轻工业 | 1139篇 |
| 水利工程 | 325篇 |
| 石油天然气 | 444篇 |
| 武器工业 | 540篇 |
| 无线电 | 12158篇 |
| 一般工业技术 | 3906篇 |
| 冶金工业 | 658篇 |
| 原子能技术 | 236篇 |
| 自动化技术 | 26484篇 |
出版年
| 2025年 | 556篇 |
| 2024年 | 1413篇 |
| 2023年 | 1512篇 |
| 2022年 | 1744篇 |
| 2021年 | 2087篇 |
| 2020年 | 2010篇 |
| 2019年 | 1685篇 |
| 2018年 | 1492篇 |
| 2017年 | 1781篇 |
| 2016年 | 1950篇 |
| 2015年 | 2338篇 |
| 2014年 | 3030篇 |
| 2013年 | 2906篇 |
| 2012年 | 3671篇 |
| 2011年 | 3735篇 |
| 2010年 | 3259篇 |
| 2009年 | 3231篇 |
| 2008年 | 3449篇 |
| 2007年 | 3527篇 |
| 2006年 | 2875篇 |
| 2005年 | 2557篇 |
| 2004年 | 2055篇 |
| 2003年 | 1629篇 |
| 2002年 | 1260篇 |
| 2001年 | 1021篇 |
| 2000年 | 782篇 |
| 1999年 | 603篇 |
| 1998年 | 479篇 |
| 1997年 | 438篇 |
| 1996年 | 339篇 |
| 1995年 | 262篇 |
| 1994年 | 226篇 |
| 1993年 | 190篇 |
| 1992年 | 154篇 |
| 1991年 | 117篇 |
| 1990年 | 118篇 |
| 1989年 | 79篇 |
| 1988年 | 69篇 |
| 1987年 | 48篇 |
| 1986年 | 52篇 |
| 1985年 | 50篇 |
| 1984年 | 38篇 |
| 1983年 | 41篇 |
| 1982年 | 28篇 |
| 1981年 | 19篇 |
| 1980年 | 9篇 |
| 1979年 | 12篇 |
| 1976年 | 8篇 |
| 1975年 | 8篇 |
| 1959年 | 6篇 |
排序方式： 共有10000条查询结果，搜索用时 0 毫秒
951.
Seok Choi Yong Kim Tien Van Nguyen Won Hee Jeong Kyeong-Sik Min Byung Joon Choi 《Advanced Electronic Materials》2021,7(6):2100050
Frequent data transfers between Internet-of-Things (IoT) sensors and cloud servers consume energy and lead to latency—a bottleneck for ubiquitous computing. To reduce the need for such enormous data transfers, the combined function of IoT sensors and near-sensor artificial neural networks can process data properly before they are transferred to cloud servers. Herein, energy-efficient memristor crossbar arrays are demonstrated for image recognition tasks that are potentially adopted for IoT sensors. The adoption of the selector-free memristor device with a self-rectifying function allows for simple stacking of metal–dielectric–metal layer, thus significantly simplifying the fabrication process while achieving low-current operation (<10 µA in microdevice). Area-dependent resistive switching characteristics and the incorporation of interface effects reveal the role of the switching and rectifying phenomena in such devices. Finally, the Modified National Institute of Standards and Technology pattern recognition task is demonstrated with 32 × 32 memristor crossbar arrays combining a SPICE simulation. Therefore, it is expected that self-rectifying memristor arrays can pave the way for the development of more intelligent IoT sensors. 相似文献
952.
The image‐based inertial impact (IBII) test has shown promise for measuring properties of composites at strain rates where existing test methods become unreliable due to inertial effects (> 102 s?1 ). Typically, the IBII tests are performed with a single camera, and therefore, to use surface measurements for material property identification, it is necessary to assume that the test is two‐dimensional. In this work, synchronised ultra‐high‐speed cameras are used to quantify the relevance of this assumption when nonuniform, through‐the‐thickness loading is applied to interlaminar samples. Initial experiments revealed that an angular misalignment of approximately 1° between the impact faces of the waveguide and projectile created a bending wave that propagated along the sample behind the axial pulse. Even under these conditions, consistent measurements of stiffness were made by assuming a linear distribution of the behaviour through‐the‐thickness. When the misalignment was reduced to 0.2°, the effects on single‐sided measurements were significantly reduced. The two alignment cases were compared to show that three‐dimensional loading had a small effect on stiffness identification (approximately 5% bias) relative to failure stress (approximately 30% bias). This study highlights the importance of impact alignment for reliable characterisation of the interlaminar failure stress and was used to establish guidelines for diagnosing loading issues from single‐sided measurements. 相似文献
953.
Rukiye Nur Kamaz Bülent Y&#x;lmaz Zafer Ayd&#x;n 《International journal of imaging systems and technology》2021,31(1):327-335
Reflections of LED light cause unwanted noise effects called specular reflection (SR) on colonoscopic images. The aim of this study was to seek answers to the following two questions. (a) How are the texture features used in automatic detection of polyps affected by the interpolation on specular reflections? (b) If they are affected does it really affect the classification performance? In order to answer these questions, we used 610 colonoscopy images, and divided each image into tiles whose sizes were 32‐by‐32 pixels. From these tiles, we selected the ones without any specular reflection. We added different shape and size specular reflections cropped from real images onto the reflection‐free tiles. We then used the nearest neighbors, bilinear and bicubic interpolation techniques on the tiles on which SRs were added. On these tiles we extracted 116 texture features using 3 second‐order approaches, and 4 first‐order statistics. First, we used paired sample t test. Second, we performed automatic classification of polyps and background using random forest and k nearest neighbors (k‐NN) approaches using the texture features for different combinations of specular reflections added on the tiles from the polyp or background. The results showed that depending on the size of specular reflection, interpolation can cause a significant difference between the texture features that were coming from reflection‐free tiles and the same tiles on which interpolation was performed. In addition, we note that bicubic interpolation may be preferred to eliminate specular reflection when texture features are used for background and polyp discrimination. 相似文献
954.
基于小波分析的车型识别 总被引：4，自引：0，他引：4
靳敏 《电子测量与仪器学报》2003,17(2):31-34,60
本文论述了用小波分析提取车辆图像边缘信号的方法,得到了连续、光滑的边缘图像,并将其应用于公路车辆车型的检测与识别系统中,实验表明识别过程准确、速度快,具有较好的应用前景。 相似文献
955.
计算图像中目标简缩比的快速算法及其应用 总被引：1，自引：0，他引：1
提出了一种图像中目标轮廓线的提取技术和目标面积、周长、简缩比的算法,具有速度快,精度高的优点。它们作为目标的总体判别标准,可用于目标的判别,其判别速度要比常规的判别方法要快。 相似文献
956.
用镜像法计算大型电力变压器漏磁场的研究 总被引：2，自引：1，他引：2
大型电力变压器漏电抗及电磁力的计算实际上就是变压器漏磁场的计算,采用镜像电流法对变压器铁心窗中的漏磁场进行了计算,给出了场点处磁感应强度与最高镜像电流次数奇偶性的关系,用最高镜像次数相邻的镜像电流及实际电流算得的场点处磁感应强度的平均值近似场点处磁场感应强度的实际值。用此方法计算变压器的漏磁场,在编程及计算工作量相对较小的情况下,可获得具有很高精度的磁感应强度。 相似文献
957.
图像测量技术及其应用 总被引：12，自引：0，他引：12
图像测量是近年来发展起来的测量技术，它利用获取的物体图像，经过计算机处理实现对物体的几何尺寸、形状的测量，广泛应用于工业监测、航空遥感等领域中。本文对该技术的现状作以简述，并介绍一个CCD(Charge Coupled Device——电荷耦合器件)图像测量系统。 相似文献
958.
We report on the development of an algorithm to improve the registration of serial 3D MR breast images using combined global
translation and rotation with locally varying parameters as geometric transformations. Several phantom and volunteer data
sets were acquired and registered using mutual information as a similarity measure of the matching process. After applying
a global translation by using a rigid matcher, optimum horizontal and vertical rotation angles were determined. In case of
the phantom measurements, angle optimization was performed for each slice of the 3D data set of the phantom, which was deliberately
shifted and rotated around different axes. In case of registration of volunteer data, optimum rotation parameters were calculated
for preselected equidistant slices of the data set to speed up the calculation time. For slices located between and outside
these support slices, the rotation angles were calculated by linear interpolation and extrapolation of the slope of the regression
determined by the optimized angles of the support slices. The algorithm improves the registration of serial 3D MR data sets
and represents a compromise between a rigid and an elastic 3D matching procedure. 相似文献
959.
基于小波基向量的改进FRIT去噪方法 总被引：4，自引：0，他引：4
计算小波变换的Mallat算法需要逐级分解和重构,而本文通过矩阵变换方法,给出不需逐级计算的小波分解和重构矩阵的构造方法,并给出9/7小波的分解和重构矩阵的基向量及波形图.另外,本文改进了一种新型的图像方向性表示方法--有限域Ridgelet变换(FRIT),通过折叠分块和增加零行的方法克服了原FRIT需要构造素数长度的小波基的缺点,使小波变换的基向量可直接应用于FRIT中,计算方法和计算量都得到简化.实验表明,在对具有直线特征的图像去噪方面其性能优于FRIT. 相似文献
960.
Structural bonding and bonded repairs of composite materials become more and more important. Understanding the strain within the bondline leads to suitable bonding design. For new design approaches the strain distribution within the bondline has to be analyzed. Thus, often finite element analysis (FE) are used. However, a huge challenge is the availability of reliable material properties for the adhesives and their validation. Previous work has shown that it is possible to measure the small displacements resulting within thin epoxy film adhesives using high resolution digital image correlation (DIC). In this work a 2D DIC setup with a high resolution consumer camera is used to visualize the strain distribution within the bondline over the length of the joint as well as over the adhesive thickness. Therefore, single lap joints with thick aluminum adherends according to ASTM D 5656 are manufactured and tested. Local 2D DIC strain measurements are performed and analyzed. Two different camera setups are used and compared. The evaluation provides reliable material data and enables a look insight the bondline. The results of the full field strain data measured with DIC are compared with numerical simulations. Thus, material models as well as chosen parameters for the adhesive are validated. Compared to extensometers, giving only point-wise information for fixed measuring points, the DIC allows a virtual point-wise inspection along the complete bondline. Furthermore, it allows measuring close to the bondline to reduce the influence of adherend deformation. 相似文献