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951.
Lambropoulos JC Fang T Funkenbusch PD Jacobs SD Cumbo MJ Golini D 《Applied optics》1996,35(22):4448-4462
Deterministic microgrinding of precision optical components with rigid, computer-controlled machining centers and high-speed tool spindles is now possible on a commercial scale. Platforms such as the Opticam systems at the Center for Optics Manufacturing produce convex and concave spherical surfaces with radii from 5 mm to ∞, i.e., planar, and work diameters from 10 to 150 mm. Aspherical surfaces are also being manufactured. The resulting specular surfaces have a typical rms microroughness of 20 nm, 1 μm of subsurface damage, and a figure error of less than 1 wave peak to valley. Surface roughness under deterministic microgrinding conditions (fixed infeed rate) with bound abrasive diamond ring tools with various degrees of bond hardness is correlated to a material length scale, identified as a ductility index, involving the hardness and fracture toughness of glasses. This result is in contrast to loose abrasive grinding (fixed nominal pressure), in which surface microroughness is determined by the elastic stiffness and the hardness of the glass. We summarize measurements of fracture toughness and microhardness by microindentation for crown and flint optical glasses, and fused silica. The microindentation fracture toughness in nondensifying optical glasses is in good agreement with bulk fracture toughness measurement methods. 相似文献
952.
Yu-Tzu?Chen Wei-Feng?Fang Yen-Cheng?Liu Jing-Tang?YangEmail author 《Microfluidics and nanofluidics》2011,11(3):339-352
The mixing and reaction performance of a split-and-recombine (SAR) microreactor was enhanced on modification of the geometric
configuration. A rotation of fluid is induced on shrinking the structure of the splitting and reorientation region in alternate
directions, thus improving the pattern of multi-lamination and enhancing the chaos of the fluid. To design and to analyze
systematically the performance of the reactors, an effective method involving chaotic analysis and fluorescent resonant-energy
transfer (FRET) is proposed. The structural design of a passive microreactor to generate an effective contact between the
reagents is of great practical significance. SAR microreactors of four types with various microstructures were designed to
illustrate the effects of geometric patterns (i.e., arrangement and dimensions) on mixing and reaction. Through analysis of
the chaos, we revealed numerically the dynamic mixing governed by multi-lamination and chaotic mechanisms in the devices.
The results show that specific structural designs induce rotation and rearrangement of fluids, thus elongating their material
interface; the mixing of the fluids consequently improved. We investigated the hybridization of two complementarily labeled
oligonucleotides in the devices by means of FRET. How the devices affected the rate of hybridization was thereby assessed,
verifying that FRET is a technique capable of estimating the practical applicability of these devices. 相似文献
953.
Ensemble of surrogates with recursive arithmetic average 总被引:2,自引:0,他引:2
Xiao Jian Zhou Yi Zhong Ma Xu Fang Li 《Structural and Multidisciplinary Optimization》2011,44(5):651-671
Surrogate models are often used to replace expensive simulations of engineering problems. The common approach is to construct
a series of metamodels based on a training set, and then, from these surrogates, pick out the best one with the highest accuracy
as an approximation of the computationally intensive simulation. However, because the choice of approximate model depends
on design of experiments (DOEs), the traditional strategy thus increases the risk of adopting an inappropriate model. Furthermore,
in the design of complex product system, because of its feature of one-of-a-kind production, acquiring more samples is very
expensive and intensively time-consuming, and sometimes even impossible. Therefore, in order to save sampling cost, it is
a reasonable strategy to take full advantage of all the stand-alone surrogates and then combine them into an ensemble model.
Ensemble technique is an effective way to make up for the shortfalls of traditional strategy. Motivated by the previous research
on ensemble of surrogates, a new technique for constructing of a more accurate ensemble of surrogates is proposed in this
paper. The weights are obtained using a recursive process, in which the values of these weights are updated in each iteration
until the last ensemble achieves a desirable prediction accuracy. This technique has been evaluated using five benchmark problems
and one reality problem. The results show that the proposed ensemble of surrogates with recursive arithmetic average provides
more ideal prediction accuracy than the stand-alone surrogates and for most problems even exceeds the previously presented
ensemble techniques. Finally, we should point out that the advantages of combination over selection are still difficult to
illuminate. We are still using an “insurance policy” mode rather than offering significant improvements. 相似文献
954.
955.
太阳辐射监测仪实验自动监控软件设计 总被引:3,自引:2,他引:1
太阳辐射监测仪(SIM)是某卫星上的监测太阳总辐照度变化的高精度仪器,其测量精度是交付前重点考核的技术指标;测量精度标定实验中的测量数据需要手动控制1553B总线进行下传,手动分解提取1553B包内的数据,判断仪器的工作状态,人工处理的工作量大且易引入人为误差;另外,仪器对测量环境要求高,人为参与会影响环境的稳定,因此需要实现整个实验过程的自动监控和数据自动处理。通过分析1553B仿真卡的特点,利用VC++编写了线程监控程序,操作界面一键控制,实现了实验数据的1553B自动下传,自动接收和保存;实验表明,监控软件操作简单、运行可靠,太阳辐射监测仪重复性测量精度满足小于5‰的设计要求。 相似文献
956.
957.
方园 《计算机测量与控制》2011,19(3)
移动自组网中节点通信时路由开销较大,从而引起整个自组网的能耗过高;为了解决这一问题,针对移动自组网的现实组网特征进行了研究,提出了基于复杂网络理论的移动自组网路由算法;在该路由算法中,路由发现基于源节点到目的节点的梯度方向,源节点选取下一级跳数据转发对象时,在其邻域范围内以选取路径是否符合最速下降法作为判断依据;当源节点和目的节点之间存在的节点个数超过复杂网络理论中的达到条件时,源节点在路由方向上选取其邻域内最接近的节点进行转发后,按照最速下降法继续寻找最优路径;实验表明,该路由算法具有较少的跳级数,可以减轻整个自组网的数据存储压力,路由开销在节点疏密度不同时,介于OLSR协议和AODV协议之间. 相似文献
958.
软件无线电因为它的开放性强,兼容性高,在航空航天,多频段、多用户、多模兼容以及互联系统有着广泛的应用前景;文中简要介绍了软件无线电的背景,着重对其关键技术及研究难点提炼与归纳,最后对软件无线电在军事通信、个人移动通信的应用与发展趋势进行了分析及总结。 相似文献
959.
计算机网络课程实验教学改革的探索 总被引:5,自引:5,他引:0
实验教学是计算机网络课程的重要组成部分,本文通过分析当前计算机网络课程实验教学的现状,根据计算机网络课程的特点,探讨改进计算机网络课程实验教学的思路。 相似文献
960.