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81.
Performance of a noise barrier within an enclosed space 总被引:1,自引:0,他引:1
The present study involved experimental, theoretical, and numerical analyses of the insertion loss provided by rigid noise barriers in an enclosed space. The existing classical diffuse-field theory may be unable to predict the actual sound pressure level distribution and barrier insertion loss for indoor applications. Although predictions made by the ray tracing method at high frequencies are reasonably satisfactory, the method is computer-intensive and time-consuming. We propose a new formula that incorporates the effects of diffraction theory and the reflection of sound between room surfaces. Our results indicate that the present formula provides more realistic and practical predictions of the barrier insertion loss than existing approaches. 相似文献
82.
Iman Kohyarnejadfard Daniel Aloise Michel R. Dagenais Mahsa Shakeri 《Entropy (Basel, Switzerland)》2021,23(8)
Advances in technology and computing power have led to the emergence of complex and large-scale software architectures in recent years. However, they are prone to performance anomalies due to various reasons, including software bugs, hardware failures, and resource contentions. Performance metrics represent the average load on the system and do not help discover the cause of the problem if abnormal behavior occurs during software execution. Consequently, system experts have to examine a massive amount of low-level tracing data to determine the cause of a performance issue. In this work, we propose an anomaly detection framework that reduces troubleshooting time, besides guiding developers to discover performance problems by highlighting anomalous parts in trace data. Our framework works by collecting streams of system calls during the execution of a process using the Linux Trace Toolkit Next Generation(LTTng), sending them to a machine learning module that reveals anomalous subsequences of system calls based on their execution times and frequency. Extensive experiments on real datasets from two different applications (e.g., MySQL and Chrome), for varying scenarios in terms of available labeled data, demonstrate the effectiveness of our approach to distinguish normal sequences from abnormal ones. 相似文献
83.
在惯性约束聚变(ICF)终端光学聚焦系统中,采用取样光栅将透射的高功率三倍频光按约0.5%的效率进行聚焦采样,送入能量计中进行诊断。提出了用取样光栅对结构取代单取样光栅,通过合理选择系统参数,包括两块光栅的距离、光栅倾斜角度等,设计出的消像差取样光栅可同时进行能量诊断、光脉冲响应测量、以及远场光斑质量的检测。计算结果显示:光程差从8.3 cm降低到8.7 mm,像点的均方根半径为0.777 μm,达到衍射极限和使用要求。这为ICF系统中激光能量、波前畸变的诊断提供了一种可供选择的新诊断装置。 相似文献
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86.
气动光学头罩光传输数值仿真 总被引:1,自引:0,他引:1
气动热环境下光学头罩由于受气动热效应作用,其形状和光学性质都将发生改变,从而影响头罩内的光传输。建立气动光学头罩有限元分析模型,根据热光效应和弹光效应理论,对头罩的折射率场进行数值计算,采用四阶龙格-库塔法编制光线追迹程序对气动光学头罩内红外辐射光线传输进行了数值仿真,得到了头罩光学系统出射波面波像差和调制传递函数。研究结果表明:气动热环境下热光效应对光学头罩光传输的影响远比弹光效应大,且气动光学头罩成像质量受到气动热效应的影响严重下降,为了提高高速飞行器的制导精度,不能忽视气动热对头罩光传输的影响。 相似文献
87.
《中国化学快报》2020,31(10):2854-2858
In recent years, oil spills caused by human activities have occurred frequently, and the resultant oil pollution has received extensive attention worldwide. In this paper, a total of 50 water samples were collected from the northeastern part of the South China Sea, and total petroleum hydrocarbons (TPHs) and n-alkane content in the samples were analyzed by gas chromatography-flame ionization detector (GC-FID) technology. The petroleum hydrocarbon characteristic indices, such as carbon predominance index (CPI) and terrigenous/aquatic ratio (TAR), were calculated to trace the source of petroleum hydrocarbons. The measured value of TPHs ranged from 121.31–603.02 μg/L. For surface waters, the TPHs in the northern coastal waters and the central waters were higher than that in the far shore. For vertical waters, the TPHs sharply decreased at first, and then increased slowly and finally reached a steady state. The n-alkanes in the water samples were concentrated in C10-C38, and they were mainly from terrestrial higher plant. The waters in the near shore, mid-layer and deep sea showed a strong reducing terrestrial characteristic, while the surface waters in the open sea showed an obvious oxidizing endogenous characteristic. 相似文献
88.
The steady-state distribution of circulating power in coupled, unidirectional ring resonators containing a diode-pumped laser crystal and nonlinear optical elements is computed. The full set of transcendental nonlinear equations describing the interactions between the circulating power and the optical elements is solved by a numerical root find function of a commercial mathematics software. The method allows computation of the output of sequential nonlinear processes such as laser gain, second harmonic generation and optical parametric amplification as a function of the input diode pump power. It is also possible to optimize the nonlinear interaction by selecting the optimum interaction cross-section or crystal length. The circulating power may thereby be re-distributed to obtain the lowest possible passive loss. 相似文献
89.
提出一种基于几何光路追踪方法并可在流体模拟程序中实现在线计算的激光交叉束能量转移(CBET)耦合模型。借助由激光逆轫致吸收公式引入的泵浦激光功率密度在流体网格尺度上的计算公式,该模型可计算探针激光束中每根光线所携带的能量经过与泵浦激光场相互作用带来的损失(或增加),从而实现激光能量在束间的转移。反复迭代的计算方法解决了由于激光束间能量转移与光线历史相关并且束间强耦合带来的方程求解困难。模型很容易推广到多束激光束两两能量交换的情形,也可用于研究逆轫致吸收和激光等离子体相互作用等物理内容。 相似文献
90.