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991.
External Electric Field Effect on Hydrogenic Donor Impurity in Zinc-Blende InGaN Quantum Dot 下载免费PDF全文
The binding energy of a hydrogenic donor impurity in zinc-blende (ZB) InGaN quantum dot (QD) is calculated in the framework of effective-mass envelope-function theory using the plane wave basis. It is shown that the donor binding energy is highly dependent on the impurity position, QD size and the external electric field. The symmetry of the electron probability distribution is broken and the maximum of the donor binding energy is shifted from the centre of QD in the presence of the external electric field. The degenerating energy levels for symmetrical positions with respect to the centre of QD are split. The splitting increases with the increase of QD height while the splitting increases up to a maximum value and then decreases with the increase of QD radius. 相似文献
992.
Simulation of Phase-Change Random Access Memory with Ring-Type Contactor for Low Reset Current by Finite Element Modelling 下载免费PDF全文
A three-dimensional finite element models for phase change random access memory (PCRAM) is established to simulate thermal and electrical behaviours during RESET operation. The RESET behaviours of the conventional structure (CS) and the ring-type contact in bottom electrode (RIB) are compared with each other. The simulation results indicate that the RIB cell has advantages of high heat efficiency for melting phase change material in cell, reduction of contact area and lower RESET current with maintaining good resistance contrast. The RESET current decreases from 1.26mA to 1.2mA and the heat consumption in CST material during programming increases from 12% to 37% in RIB structure. Thus the RIB structure PCRAM cell is suitable for future device with high heat efficiency and smaller RESET current. 相似文献
993.
We study the relationship between thermal conditions on the earth bottom boundary and the formation of Somali jet based on the Biot-Savart law and the data from National Centres for Environmental Prediction (NCEP). As the radiation from the Sun gradually moves from the southern meridian, the temperature on the surface of Somali Peninsular and Arabic Peninsular gradually increases. During the same period the surface temperature of the Northern Indian Ocean increases much slower. It is shown that this increase of the temperature difference between the land and sea is inductive to the formation and development of Rayleigh-Benard convection and leads to the increasing relative vorticity strength between positive and negative vertical vortices over the land and sea. According to the Biot-Savart law, increase of vorticity strength will correspondingly induce the horizontal velocity. A pair of positive and negative vorticity fields over the two Peninsulars and the sea surface is effective in forming and maintaining this current. This mechanism is referred to as the 'Somali suction pump'. It draws air continually from the Southern hemisphere and releases it at the coastal area of Somali. 相似文献
994.
Realization of Ultraviolet Electroluminescence from ZnO Homojunction Fabricated on Silicon Substrate with p-Type ZnO:N Layer Formed by Radical N2O Doping 下载免费PDF全文
ZnO homojunction light-emitting diodes are fabricated on Si(100) substrates by plasma assisted metal organic chemical vapour deposition. A p-type layer of nitrogen-doped ZnO film is formed using radical N2O as the acceptor precursor. The n-type ZnO layer is composed of un-doped ZnO film. The device exhibits desirable rectifying behaviour with a turn-on voltage of 3.3 V and a reverse breakdown voltage higher than 6 V. Distinct electrolumineseence emissions centred at 395nm and 490nm are detected from this device at forward current higher than 20mA at room temperature. 相似文献
995.
高分子熔体或浓溶液中链段扩散和链的弛豫模式满足普适的物理定律,这些定律代表了高分子链动力学的普遍特征.核磁共振(NMR)则为我们直接验证这些物理定律或揭示高分子运动的基本规律提供了强有力的实验手段.本文介绍三个基本的高分子动力学模型(即Rouse模型,蛇行/管道模型和重整化Rouse模型)和以这三个理论模型为基础的NMR实验原理和技术.最后对相关的NMR实验结果进行了综述,并着重与理论模型所期待的结果进行了比较. 相似文献
996.
提出了一种在多片Si-PIN探测器中间用2mm厚的聚乙烯作为灵敏度增强介质,采用加法电路模式进行信号输出的组合式新型DT聚变中子(14MeV)探测技术原理. 这种组合的主要特点有: 1)大幅度提高了Si-PIN探测器的中子灵敏度和测量统计性; 2)提高了探测器的n/γ分辨本领; 3)在实现多个探测器信号相加的同时,组合探测器相对于单片探测器时间响应没有明显改变. 从实验及理论上对组合探测器的14MeV中子及1.25MeV γ灵敏度、n/γ分辨,时间特性和测量统计性进行了研究.
关键词:
Si-PIN半导体探测器
灵敏度
n/γ分辨
时间响应 相似文献
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为了实现激光雕刻切割机的灵活控制,提出了一种基于PMAC运动控制器的激光雕刻控制系统方案。PMAC运动控制器通过Pcomm32通信驱动程序接收工控机的指令数据,并将控制量传递给伺服驱动器,控制两个交流伺服电机的运转,同时伺服驱动器接收伺服电机的位置反馈信号,进行位置补偿,从而达到电机位置的精确控制。对运动控制模块进行了设计,并给出运动了程序基本结构。该方案结构简单,可靠性好,控制方式灵活,加工效率得到了大幅度的提高。 相似文献