全文获取类型
收费全文 | 1000篇 |
免费 | 88篇 |
国内免费 | 46篇 |
专业分类
化学 | 70篇 |
晶体学 | 6篇 |
力学 | 492篇 |
综合类 | 14篇 |
数学 | 140篇 |
物理学 | 412篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 22篇 |
2021年 | 30篇 |
2020年 | 42篇 |
2019年 | 13篇 |
2018年 | 22篇 |
2017年 | 31篇 |
2016年 | 36篇 |
2015年 | 39篇 |
2014年 | 25篇 |
2013年 | 50篇 |
2012年 | 53篇 |
2011年 | 81篇 |
2010年 | 58篇 |
2009年 | 56篇 |
2008年 | 50篇 |
2007年 | 39篇 |
2006年 | 48篇 |
2005年 | 35篇 |
2004年 | 52篇 |
2003年 | 42篇 |
2002年 | 38篇 |
2001年 | 30篇 |
2000年 | 33篇 |
1999年 | 24篇 |
1998年 | 21篇 |
1997年 | 22篇 |
1996年 | 15篇 |
1995年 | 25篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1134条查询结果,搜索用时 15 毫秒
41.
根据高性能计算机全天候温控的需要,提出了综合应用蒸气压缩和动力型分离式热管制冷技术的复合冷源方案。在冬季及春、秋过渡的低温季节,运行热管循环不仅大幅降低环控装置的能耗,而且可以避免在低温环境运行压缩式制冷易发生的冷启动、回油润滑等问题。提出了蒸气压缩制冷、蒸气压缩/热管复合制冷和热管制冷的分区工作模式,引入复合制冷模式有效拓宽了热管运行温区,大幅提高了制冷系统的综合COP。模拟分析了在北京地区应用热管复合制冷技术的节能性能,相比常规的压缩制冷节能率高达40%。研究表明:热管复合制冷系统具有显著的节能减排优势,特别适用于全天候工作的机房、基站等高热密度电子集成系统的温控。 相似文献
42.
43.
The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper. 相似文献
44.
Masahiro Ishii 《Optical Review》2009,16(4):449-451
The slant from horizontal size disparity is geometrically predictable. The apparent slant, however, is usually not equivalent
to the prediction as numerous visual factors affect it. The aim of this study is to examine whether the vertical angular subtense
of a stimulus with horizontal size disparity alters the magnitude of perceived slant for a given horizontal angular subtense.
The results indicate that a smaller angular subtense of display produces a smaller magnitude of slant perception. 相似文献
45.
根据高炉冲渣水的余热特点,提出了一个采用分离式热管换热器的余热回收的方案。文中对余热回收方案中换热设备的结构特点进行了描述。 相似文献
46.
Poisson's ratio in viscoelastic materials is a function of time. However, recently developed waterhammer models of viscoelastic pipes consider it constant. This simplifying assumption avoids cumbersome calculations of double convolution integrals which appear if Poisson's ratio is time-dependent. The present research develops a mathematical model taking the time dependency of Poisson's ratio into account for linear viscoelastic pipes. Poisson's ratio is written in terms of relaxation function and bulk modulus which is assumed to be constant. The relaxation function is obtained from creep function given as the viscoelastic property data of pipe material. The results obtained from the present waterhammer model are compared with the experimental data for two different flow rates. The comparison reveals that with the application of the time-dependent Poisson's ratio and unsteady friction, the viscoelastic data of mechanical tests can directly be used for waterhammer analysis with less need for the calibration of the flow configuration. It was also shown that the creep curve calibrated based on the present model is closer to the actual creep curve than that calibrated based on previous models. 相似文献
47.
Superconducting deflecting cavities can be used in synchrotron light source to generate subpicosecond X-ray pulses while the impedance of the lower order modes (LOM) and higher order modes (HOM) in the cavity should be kept below an accepted level to avoid beam instability. These modes can be damped by adding waveguide on beam pipe. Detailed simulation of Q in CST Microwave Studio is introduced and experiment results on an aluminum model cavity with damping waveguide are reported to make a comparison. 相似文献
48.
分析了校园MIS及数据资源的特征,针对校园信息资源范围广、关联复杂的状况,提出了数据资源统一访问策略——分层访问.数据访问分为七层,各层完成数据访问独立性的特定功能,使不同的访问软件能透明访问全部数据资源.为保证传统应用能基于网络计算访问统一数据资源,又提出了“数据访问管道”和数据库访问服务器的技术.文章分析了以应用服务器为基础的N-Tiers计算的弊端,设计了“虚拟应用服务器”WUV-APPS,将数据访问对象构造成数据对象组件. 相似文献
49.
50.
We suggest a new set of equations to employ smoothed particle hydrodynamics (SPH) in a curvilinear space, and we refer to it as curvSPH. In classical SPH, the horizontal and vertical resolution of discretization is supposed to be equal for fluid particles. However, curvSPH makes the horizontal and vertical resolutions independent from each other. This is performed by transformation of physical space into an appropriate computational space with a different scale in horizontal and vertical directions. Solving a problem using SPH in a curvilinear space also provides capability to model curved boundaries as straight lines. In classical SPH, special care is needed to reach a uniform mass distribution along curved boundaries; however, producing uniform mass distribution along a line using curvSPH is straight forward. Different simulations, including simulation of a flip bucket are performed to demonstrate the applicability of the proposed method. Good agreement of results with experimental data and classical SPH confirms the capabilities of curvSPH. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献