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971.
An underwater object moving at a near-critical speed in a shallow-water domain had been observed to generate a sequence of upstream propagating solitary waves with an elongated depression of water surface and a train of dispersive waves followed in the downstream. This study presents the development of a two-dimensional stream function–vorticity based viscous fluid model with satisfied nonlinear free-surface conditions to study the generation of solitary waves and the induced vortex motion under the forcing of a moving object. A combined finite analytic and finite difference method is adopted to solve the flow field equations and free-surface boundary conditions in a transient curvilinear coordinate system. The model is shown to produce free-surface elevations in fairly good agreements with published results for a test case of a moving smooth bump. Other tests for the generation of recirculation zone behind a body of square shape in a confined fluid domain are also conducted to further verify the model performance. The results showing the generation of upstream advancing solitary waves and downstream vortex pattern by a blunt rectangular body moving at a critical speed along the bottom in a domain with free surface are presented. Comparisons of results from potential flow and viscous flow conditions are made to demonstrate the importance of viscosity to the wave generation. Different from the relatively regular vortex pattern occurred under the case of Re = 3500, the transition of the vortex motion for a larger Reynolds number (e.g. Re = 35,000) evolves without a regular pattern throughout the generation process of the advancing solitons. The effects of the size and bluntness of a moving object on the generated flow field and free-surface elevations are also analyzed and discussed. 相似文献
972.
Water property monitoring and assessment for China's inland Lake Taihu from MODIS-Aqua measurements 总被引:4,自引:0,他引:4
We provide results of quantitative measurements and characterization for inland freshwater Lake Taihu from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the satellite Aqua. China's Lake Taihu, which is located in the Yangtze River delta in one of the world's most urbanized and heavily populated areas, contains consistently highly turbid waters in addition to frequent large seasonal algae blooms in various lake regions. Thus, satellite data processing requires use of the shortwave infrared (SWIR) atmospheric correction algorithm. Specifically for Lake Taihu, an iterative SWIR-based atmospheric correction algorithm has been developed and proven to provide reasonably accurate water-leaving radiance spectra data. Using MODIS-Aqua measurements, the blue-green algae bloom in Lake Taihu in 2007 has been studied in detail, demonstrating the importance and usefulness of satellite water color remote sensing for effectively monitoring and managing a bloom event.Seasonal and interannual variability, as well as spatial distributions, of lake water properties were studied and assessed using the MODIS-Aqua measurements from 2002 to 2008. Results show that overall waters in Lake Taihu are consistently highly turbid all year round, with the winter and summer as the most and least turbid seasons in the lake, respectively. Extremely turbid waters in the winter are primarily attributed to strong winter winds that lead to significant amounts of total suspended sediment (TSS) in the water column. In addition, MODIS-Aqua-measured water-leaving radiance at the blue band is consistently low in various bay regions in Lake Taihu, indicating high algae concentration in these regions. Climatological water property maps, including normalized water-leaving radiance spectra nLw(λ), chlorophyll-a concentration, and water diffuse attenuation coefficient at the wavelength of 490 nm (Kd(490)), are derived from all MODIS-Aqua data from 2002 to 2008 for Lake Taihu, showing overall spatial distribution features for the lake water property. 相似文献
973.
Tang L Garvin MK Lee K Alward WL Kwon YH Abràmoff MD 《IEEE transactions on pattern analysis and machine intelligence》2011,33(11):2245-2258
A robust multiscale stereo matching algorithm is proposed to find reliable correspondences between low contrast and weakly textured retinal image pairs with radiometric differences. Existing algorithms designed to deal with piecewise planar surfaces with distinct features and Lambertian reflectance do not apply in applications such as 3D reconstruction of medical images including stereo retinal images. In this paper, robust pixel feature vectors are formulated to extract discriminative features in the presence of noise in scale space, through which the response of low-frequency mechanisms alter and interact with the response of high-frequency mechanisms. The deep structures of the scene are represented with the evolution of disparity estimates in scale space, which distributes the matching ambiguity along the scale dimension to obtain globally coherent reconstructions. The performance is verified both qualitatively by face validity and quantitatively on our collection of stereo fundus image sets with ground truth, which have been made publicly available as an extension of standard test images for performance evaluation. 相似文献
974.
Maw-Kae Hor Cheng-Yuan Tang Yi-Leh Wu Kai-Hsuan Chan Jeng-Jiun Tsai 《Pattern recognition letters》2011,32(8):1210-1221
This paper proposes robust refinement methods to improve the popular patch multi-view 3D reconstruction algorithm by Furukawa and Ponce (2008). Specifically, a new method is proposed to improve the robustness by removing outliers based on a filtering approach. In addition, this work also proposes a method to divide the 3D points in to several buckets for applying the sparse bundle adjustment algorithm (SBA) individually, removing the outliers and finally merging them. The residuals are used to filter potential outliers to reduce the re-projection error used as the performance evaluation of refinement. In our experiments, the original mean re-projection error is about 47.6. After applying the proposed methods, the mean error is reduced to 2.13. 相似文献
975.
Exploring the wild birds’ migration data for the disease spread study of H5N1: a clustering and association approach 总被引:1,自引:0,他引:1
Mingjie Tang Yuanchun Zhou Jinyan Li Weihang Wang Peng Cui Yuanseng Hou Ze Luo Jianhui Li Fuming Lei Baoping Yan 《Knowledge and Information Systems》2011,27(2):227-251
Knowledge about the wetland use of migratory bird species during the annual life circle is very interesting to biologists,
as it is critically important in many decision-making processes such as for conservation site construction and avian influenza
control. The raw data of the habitat areas and the migration routes are usually in large scale and with high complexity when
they are determined by high-tech GPS satellite telemetry. In this paper, we convert these biological problems into computational
studies and introduce efficient algorithms for the data analysis. Our key idea is the concept of hierarchical clustering for
migration habitat localizations, and the notion of association rules for the discovery of migration routes from the scattered
location points in the GIS. One of our clustering results is a tree structure, specially called spatial-tree, which is an
illusive map depicting the breeding and wintering home range of bar-headed geese. A related result to this observation is
an association pattern that reveals a high possibility that bar-headed geese’s potential autumn migration routes are likely
between the breeding sites in the Qinghai Lake, China and the wintering sites in Tibet river valley. Given the susceptibility
of geese to spread H5N1, and on the basis of the chronology and the rates of the bar-headed geese migration movements, we
can conjecture that bar-headed geese play an important role in the spread of the H5N1 virus at a regional scale in Qinghai-Tibetan
Plateau. 相似文献
976.
977.
介绍通过在PWM调光驱动电路中引入电感,达到平均电流的作用。从模拟和实验角度得出了驱动电路中电感大小的确定方法,并深入分析了此驱动电路中LED上电流值和PWM波占空比之间的函数依赖关系,可由计算机通过RS-485对LED亮暗程度实现实时、细致的多档位控制。 相似文献
978.
本文应用量子化学密度泛函理论(DFT)研究了2-(4-甲氧基苯基)亚肼基乙酸与乙醛酸的反应机理及动力学行为,并研究了不同取代基对反应的影响.在RB3LYP/6-31G*水平上,优化了各反应通道的反应物、中间体、过渡态及产物的几何构型,计算了各驻点的振动频率、零点能和电荷分布.计算结果表明,该反应有2条反应通道,分别生成(2Z)和(2E)-3(4-甲氧基苯基二氮烯基)丙烯酸.产物发生了键长的平均化和电荷的重新分布.两反应通道具有相同的反应入口,Z式产物为主要产物,2-(4-甲氧基苯基)亚肼基乙酸中苯环对位被给电子基团取代,有利于反应进行. 相似文献
979.
采用AntarisⅡ傅立叶变换红外光谱分析仪器(Thermo Nicolet)测定了9种杜仲的光谱数据,运用偏最小二乘法(PLS)和主成分分析回归(PCR)分别建立了杜仲中松脂醇二葡萄糖苷(PDG)含量与吸光度变量的近红外光谱定标模型,并对所建模型进行验证.结果表明,2种方法建立的模型精度都较高,其中模型的预测能力强弱指标SSE=2.8333,PRESS=7.2392,可见在近红外光谱下,PCR和PDG都适合对杜仲进行检测研究,这是本文的一个重要结果,为以后杜仲的指标检验研究提供了理论和实验依据:但是,PCR建立的(PDG)定标模型预测精度稍高于偏最小二乘法(PLS)建立的模型,所以文中只对PCR进行模型的建立,PLS方法对杜仲检测分析这个问题有待于以后的进一步讨论和研究. 相似文献
980.
在局域网中通过Excel共享工作簿和属性设置,用宏与VBA在Excel中开发大赛评分管理系统,提高工作效率。 相似文献