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61.
转板是光电雷达稳定平台的关键元件之一。为了更好地设计和分析某光电雷达稳定平台的转板,运用Pro E软件对其进行三维实体建模,合理简化后,进入Ansys软件界面建立有限元模型。应用有限元理论和Ansys软件对其进行动态特性分析,得到了转板前八阶模态的固有频率和振型,以及要求范围内的谐响应。对比了不同方法划分网格的网格质量,采取不同材料得到了不同模态。分析结果表明:设计的转板在关心的频段0~50 Hz,2 000 Hz~8 000 Hz内不发生共振,符合设计要求。 相似文献
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Aminated-CoFe2O4/SiO2 magnetic nanoparticles (NPs) were prepared from primary silica particles using modified StÖber method. By optimizing the preparation conditions, monodisperse CoFe2O4/SiO2 NPs with high amino groups’ density were obtained, which is necessary for enzyme immobilization. TEM confirm that the sample is a core/shell structure. These aminated-CoFe2O4/SiO2 NPs have narrow size distributions with a mean size of about 60 nm. Moreover, the aminated-CoFe2O4/SiO2 NPs can be easily dispersed in aqueous medium. The experimental results also show that the NPs have superparamagnetism, indicating that the aminated-CoFe2O4/SiO2 NPs can be used as an effective carrier for the enzyme immobilization. 相似文献
64.
L.B. Drissi A. Benyoussef E.H. Saidi M. Bousmina 《Journal of magnetism and magnetic materials》2011,323(23):3001-3006
The magnetic properties of Mn-doped ZnO semiconductor have been investigated using the Monte Carlo method within the Ising model. The temperature dependences of the spontaneous magnetization, specific heat and magnetic susceptibility have been constructed for different concentrations of magnetic dopant Mn and different carrier concentrations. The exact values of Mn concentration and carrier concentration at which high temperature transition occurs are determined. An alternative for the explanation of some controversies concerning the existence and the nature of magnetism in Mn diluted in ZnO systems is given. Other features are also studied. 相似文献
65.
导电环是平台式惯导系统惯性平台的重要组成部分,主要承担惯性平台台体内各种信号与系统的传输和交联,导电环发生故障直接会导致惯导系统失效。针对导电环三种故障模式:接触电阻变大、绝缘强度降低以及烧坏,本文采用微动磨损和电接触理论,结合作者的实际工作经验,对故障机理进行了分析,提出了相应的改进措施。这些措施均在生产中得到落实。落实措施后的故障统计表明,采取的改进措施有效,导电环的故障率与原来相比降低了38%。 相似文献
66.
José Bento Borba da Silva Maria Bert?lia Oss Giacomelli Ivan Gonçalves de Souza Adilson José Curtius 《Microchemical Journal》1998,60(3):249-257
Performance of graphite platforms coated with Ir, Rh, and a mixture of both, as permanent modifiers for Ag, As, Bi, Cd, and Sb, was evaluated. The coating process is very simple: a solution containing Ir, Rh, or a mixture of both is pipetted on the platform inserted in a graphite tube, and this is submitted to a temperature program. High pyrolysis temperatures are allowed, especially for As and Bi, 1400°C, in the Ir + Rh-coated platform. The sensitivity remains about the same for all analytes with different coatings, except for As in the Ir-coated platform, for which a remarkable gain was obtained in comparison to the other coatings. The lifetimes of the treated tubes were in the range 50 to more than 1000 cycles, being especially long for Sb and Ag in the Rh-coated platform, more than 600 and 1000 cycles, respectively. The Rh coating could not be used for Bi and Cd. Analysis of a certified reference water and of acid oyster tissue digests showed the absence of interference and good precision. Advantages of the permanent coatings are the possibility of low blanks byin situcleaning of the modifier and shorter analysis time. 相似文献
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One of the key differences of a semiconductor optical amplifier (SOA) with internal lasing oscillation (ILO) from a SOA with external light injection (ELI) lies in a carrier-sharing mechanism. Since the internal lasing mode shares the same pool of carriers with the signals, the carriers (or photons) withdrawn from the circulating laser mode speed up the gain recovery. On the other hand, the external light injected into the SOA shortens the carrier recovery time through optical pumping without any carrier sharing involved. To find out a better scheme, we have made a comparative investigation on the effects of the ILO and ELI on the SOA performance. It turns out by way of simulation that the ELI scheme provides faster gain recovery, shorter carrier lifetime, and higher saturation power when the external injection power is higher than the internal lasing power. The performance enhancement is not so pronounced with the carrier-sharing mechanism, as the internal lasing mode itself gives rise to severe longitudinal spatial hole burning (LSHB). Nevertheless, the ILO scheme is preferable for linear-amplification applications. We also examine the use of the ELI for low-crosstalk optical amplifiers. It is found that the ELI scheme does not bring in a very strong resonance peak in the crosstalk, which appears in a SOA with ILO due to relaxation oscillations of the lasing mode. In comparison to the ILO in SOAs, the ELI into SOAs is likely to leave more optical gain for multi-channel amplification without any sacrifice on the crosstalk. 相似文献
69.
基于Web Services的移动通信综合网管系统 总被引:1,自引:1,他引:0
基于Web Services分布式原理,提出了一种新的移动通信综合网管系统的方案.该系统与目前国内传统的TMN网管系统相比,在匹配性、移植性、扩展性、安全性以及重用性等方面都具有明显的优越性.通过对Web Services体系结构分析研究,给出了Web Services到TMN网管系统的映射.并在试验环境中,实现和验证了这种基于Web Services分布式综合网管系统.最后对如何用,ETWeb服务来实现综合的网管的关键技术进行了阐述和分析。 相似文献
70.
Maia Martcheva Gloria Crispino-O'Connell 《Journal of Mathematical Analysis and Applications》2003,283(1):251-275
The most common type of bacterial meningitis in the developed countries is caused by Neisseria meningitidis bacteria, which cause meningococcal meningitis. Case fatality rate can be between 3% and 10% in developed countries and as high as 20% in African countries. During epidemics in sub-Saharan countries, the so-called meningitis belt, the case fatality rate can peak to 70% or higher. Some people who have bacterial meningitis experience some form of after effects: epilepsy, damaged eyesight, hearing loss, brain damage. There is no immunity after infection. Approximately on average 10% of the population at any time carry the germs for days, weeks, or months. Carriers can infect other individuals by close contacts, even though they do not become ill themselves. An age-structured mathematical model is formulated that enables the understanding of the dynamics of the infection transmission. The model is used to study the conditions for the stability of the disease-free steady state (which imply extinction of the disease) and the existence of an endemic state (which leads to persistence of the disease in the population). The results of the model are applied to identify the contribution of the carriers to the transmission of the disease. Final epidemiological conclusions are given. 相似文献