全文获取类型
收费全文 | 2004篇 |
免费 | 1349篇 |
国内免费 | 532篇 |
专业分类
化学 | 1040篇 |
晶体学 | 70篇 |
力学 | 248篇 |
综合类 | 52篇 |
数学 | 229篇 |
物理学 | 2246篇 |
出版年
2024年 | 50篇 |
2023年 | 112篇 |
2022年 | 187篇 |
2021年 | 183篇 |
2020年 | 98篇 |
2019年 | 113篇 |
2018年 | 78篇 |
2017年 | 112篇 |
2016年 | 110篇 |
2015年 | 103篇 |
2014年 | 174篇 |
2013年 | 152篇 |
2012年 | 153篇 |
2011年 | 150篇 |
2010年 | 138篇 |
2009年 | 164篇 |
2008年 | 167篇 |
2007年 | 148篇 |
2006年 | 148篇 |
2005年 | 138篇 |
2004年 | 132篇 |
2003年 | 94篇 |
2002年 | 92篇 |
2001年 | 88篇 |
2000年 | 74篇 |
1999年 | 73篇 |
1998年 | 58篇 |
1997年 | 63篇 |
1996年 | 52篇 |
1995年 | 52篇 |
1994年 | 40篇 |
1993年 | 51篇 |
1992年 | 59篇 |
1991年 | 45篇 |
1990年 | 38篇 |
1989年 | 37篇 |
1988年 | 30篇 |
1987年 | 35篇 |
1986年 | 20篇 |
1985年 | 17篇 |
1984年 | 10篇 |
1983年 | 22篇 |
1982年 | 25篇 |
排序方式: 共有3885条查询结果,搜索用时 15 毫秒
1.
ZHONG Hui WAN Mingxi JIANG Yifeng WANG Supin 《声学学报:英文版》2006,25(2):104-115
The present study was to investigate the differential imaging method for detecting HIFU (High Intensity Focused Ultrasound)-induced lesions and the estimation of variation of attenuation for lesion evaluation with log spectral difference algorithm. Experiment results of bovine muscle and liver in vitro were acquired. Several algorithms for lesion detection - Absolute Difference (AD), Sum Absolute Differences (SAD) and Sum Squared Differences (SSD) - were analyzed with several window sizes and threshold values. Then three attenuation parameters were compared to evaluate the degree of tissue damage. It was found that variation of the mean attenuation △α was an effective parameter to evaluate lesions. 相似文献
2.
李亚纯 《应用数学与计算数学学报》1994,8(1):47-54
本文采用整体迭代法证明了带小初值的一阶非线性耗散偏微分方程组的Cauchy问题的整体经典解的存在性及指数衰减性质。 相似文献
3.
PANYondong QIANMenglu XUWeijiang M.OURAK 《声学学报:英文版》2004,23(1):11-16
A residual-stress profile along the thickness of an aluminum alloy sheet is determined by laser-ultrasonic technique. Surface acoustic waves are generated by a Nd:YAG pulse laser and detected by a Heterodyne interferometer on a lateral free surface of the sheet. The distribution of residual stress is determined by measuring the relative variation of the wavevelocities at different location of the sample along its thickness. This technique is validated by three different residual stress profiles obtained experimentally. 相似文献
4.
5.
Based on the expression of the dispersion equation of Lame waves in an adhesive two-layered plate pressented in our proevious paper [Chin,Phys,Lett,18(2001)1483],the two lowest Lamb modes,the symmetric mode S0 and the antisymmetric mode A0 are successfully decomposed in the low-frequency regime,Relations between the rigidity of the bond and the velocity of the two Lamb modes are found,which lay a foundation for the estimation of the bond rigidity of the adhesive plate.The influence of the variations of the bond rigidity in terms of the stiffness constants KN and KT of the spring model on the velocity of the two Lamb modes in discussed and numerically evaluated.numerical results indicate that the deterioration of the bond rigidity causes the phase velocity decrease for Lamb modes of the two lowest order,thus having a possibility for the evaluation of the bonding state of the adhesive plate by using ultrasonic wave velocity measurement. 相似文献
6.
Decay Rate of Energy Eigenfunctions in Classically Energetically Inaccessible Regions in more than One-Dimensional Configuration Spaces 下载免费PDF全文
An approximate formula is proposed for the decay rate of energy eigenfunctions in classically energetically inaccessible regions in more than one-dimensional configuration spaces. This is achieved by generalizing an approach proposed recently for energy eigenfunctions in the one-dimensional configuration space. The formula is tested numerically in the Pullen-Edmonds model. 相似文献
7.
HL-2A tokamak, the first tokamak with divertor in China, has been constructed and put into operation in 2002. The main parameters are R=1.65 m, a=0.4 m, BT=2.8 T, Ip = 0. 48 MA. The divertor of HL-2A is unique, because it is characterized with a large closed divertor chamber. The device has double divertor chamber, but now it is operating with lower single null configuration to study the physics of divertor for the next step design of a divertor. Supersonic molecular beam injection (SMBI) system with LN2 cooling trap was first installed and demonstrated on the HL-2A tokamak in 2004. The first results of SMBI into HL-2A plasma are to demonstrate the function of the HL-2A divertor and to observe the cold pulse propagation during multi-pulse SMBI on HL-2A Tokamak. 相似文献
8.
9.
测得了315 ̄330nm超声射流冷却下SO2^1A2-^1A1激光诱导荧光(LIF)激发谱,获得了7个有明显K结构的C型跃迁的转动子带分辨谱,并将70个转动子带归属为(1,m,1)-(0,0,0)和(0,n,1)-(0,0,0)(4≤m≤7,8≤n≤10)的跃迁带系。光谱分析得到SO2^1A2-^1A1跃迁的带源v00、^1A2态弯曲振动频率v′2,非谐性常数X22′分别为(27950±5)、(2 相似文献
10.
本文对衰减全反射法(ATR)的光学测定原理、衰减全反射-紫外/可见光谱方法(ATR-UV)的特点以及它们在一些典型的工业过程溶液,如高浓度和含有大量固体颗粒和微乳液聚合等体系检测的应用进行了综述.ATR-UV光谱技术适宜实时地反馈工业过程溶液的组分改变和浓度变化,从而帮助我们了解该过程的进展.这些优良的特性能帮助我们开发在线的传感器,因此可用于监测许多典型的工业过程溶液.其方法简单、迅速,一般无需对试样进行预处理或稀释.ATR-UV作为光谱学测定的重要波段,其技术开发将在化工过程检测方面具有重要的意义. 相似文献