全文获取类型
收费全文 | 3043篇 |
免费 | 402篇 |
国内免费 | 215篇 |
专业分类
化学 | 368篇 |
晶体学 | 35篇 |
力学 | 412篇 |
综合类 | 43篇 |
数学 | 1768篇 |
物理学 | 1034篇 |
出版年
2024年 | 4篇 |
2023年 | 29篇 |
2022年 | 42篇 |
2021年 | 70篇 |
2020年 | 61篇 |
2019年 | 99篇 |
2018年 | 95篇 |
2017年 | 95篇 |
2016年 | 88篇 |
2015年 | 91篇 |
2014年 | 147篇 |
2013年 | 340篇 |
2012年 | 146篇 |
2011年 | 181篇 |
2010年 | 162篇 |
2009年 | 204篇 |
2008年 | 198篇 |
2007年 | 202篇 |
2006年 | 174篇 |
2005年 | 161篇 |
2004年 | 129篇 |
2003年 | 151篇 |
2002年 | 137篇 |
2001年 | 116篇 |
2000年 | 93篇 |
1999年 | 74篇 |
1998年 | 73篇 |
1997年 | 63篇 |
1996年 | 54篇 |
1995年 | 30篇 |
1994年 | 32篇 |
1993年 | 13篇 |
1992年 | 23篇 |
1991年 | 16篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1957年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有3660条查询结果,搜索用时 31 毫秒
201.
We prove some results concerning the decay of connectivities in the low-temperature phase of the two-dimensional Ising model. These provide the bounds necessary to establish, nonperturbatively, large-deviation properties for block magnetizations in these systems. We also obtain estimates on the rate at which the finite-volume, plus-boundary-condition expectation of the spin at the origin converges to the spontaneous magnetization.On leave from São Paulo University, Brazil. 相似文献
202.
This paper is concerned with a second-order numerical method for shape optimization problems. The first variation and the second variation of the objective functional are derived. These variations are discretized by introducing a set of boundary-value problems in order to derive the second-order numerical method. The boundary-value problems are solved by the conventional finite-element method.The authors would like to express their thanks to Mr. T. Masanao, who was an undergraduate student, for his cooperation and comments. They also thank Professor Y. Sakawa of Osaka University for his encouragement.A part of this paper was presented at the IFIP Conference on Control of Boundaries and Stabilization, Clermont-Ferrand, France, 1988. 相似文献
203.
本文提出了一种应用于光纤延时系统中实现光纤延时精密测量的新方法,用以提高光纤延时测量的精度和准确性.该方法以1064 nm激光调制信号作为光源,通过测量回波信号的幅值和相位信息得到被测通道的频率响应,采用快速傅里叶逆变换得到被测目标的延时信息,实现光纤延时测量.本文通过理论分析和延时测量实验对频域反射法与传统的时域测量方法进行对比,使用频域反射法在调制频率范围10—200 MHz,采样频率间隔0.5 MHz的实验条件下,实现了3.3 ps延时测量分辨率,并证明了该方法具有比时域方法更高的测量精度,测量结果的准确性更好. 相似文献
204.
The complex permittivity spectra of tripropylene glycol and water solutions have been obtained by time domain reflectometry (TDR) technique in the frequency range from 10 MHz to 30 GHz and the temperature range 20°C–05°C. The dielectric relaxation parameters such as static dielectric constant and relaxation time were obtained by using the non-linear least square fit method. The intermolecular hydrogen bonding of tripropylene glycol–water has been discussed using the Kirkwood correlation factor and thermodynamic parameters. The activation energy decreases with increase in water content in the mixture as expected in the Arrhenius behaviour. The dielectric constant for mixtures has been fitted to the Bruggeman mixture formula in the non-linear case. 相似文献
205.
海洋重力传感器伺服回路分析与设计 总被引:1,自引:0,他引:1
李宏生 《中国惯性技术学报》2002,10(5):45-49
海洋重力仪是改善舰船惯导系统精度的重要设备,其重力传感器的伺服回路决定着仪器的精度和动态性能。作在介绍零长弹簧海洋重力传感器结构原理的基础上,研究其伺服回路的结构组成和设计方法,分析了其主要环节参数对系统性能的影响,考察了其时域性能,对海洋重力仪的研制具有重要指导作用。 相似文献
206.
Lei Xiao Edmund J. F. Dickinson Gregory G. Wildgoose Richard G. Compton 《Electroanalysis》2010,22(3):269-276
We report the comparison of electron transfer kinetic parameters of the ferrocene redox couple in both acetonitrile and in room temperature ionic liquid (RTIL) 1‐butyl‐3‐methylimidiazonium hexafluorophosphate ([C4mim] [PF6]), using edge plane pyrolytic graphite (EPPG), basal plane pyrolytic graphite (BPPG) and glassy carbon (GC) electrodes. Each electrode surface was characterized using SEM and AFM and the surface morphology was analyzed in terms of surface heterogeneity including the distribution of edge plane defects. The experimental data were modeled using both one and two dimensional simulations to correlate the electron transfer parameters obtained with the different surface structure of each electrode. Furthermore, we show that the diffusion domain approximation (commonly used to accurately simulate electron transfer kinetics at graphitic surfaces) breaks down when a BPPG electrode is used in RTIL and demonstrate the near impossibility of assigning rate constant to the basal plane surface. 相似文献
207.
Sang Hee Han Sang Kyu Kim Kyoungsook Park So Yeon Yi Hong-Kun Lyu Bong Hyun Chung 《Analytica chimica acta》2010,665(1):79-348
We assessed the abilities of wild p53 and mutant p53 proteins to interact with the consensus DNA-binding sequence using a MOSFET biosensor. This is the first report in which mutant p53 has been detected on the basis of DNA-protein interaction using a FET-type biosensor. In an effort to evaluate the performance of this protocol, we constructed the core domain of wild p53 and mutant p53 (R248W), which is DNA-binding-defective. After the immobilization of the cognate DNA to the sensing layer, wild p53 and mutant p53 were applied to the DNA-coated gate surface, and subsequently analyzed using a semiconductor analyzer. As a consequence, a significant up-shift in drain current was noted in response to wild p53, but not mutant p53, thereby indicating that sequence-specific DNA-protein interactions could be successfully monitored using a field-effect-based biosensor. These data also corresponded to the results obtained using surface plasmon resonance (SPR) measurements. Taken together, our results show that a FET-type biosensor might be promising for the monitoring of mutant p53 on the basis of its DNA-binding activity, providing us with very valuable insights into the monitoring for diseases, particularly those associated with DNA-protein binding events. 相似文献
208.
209.
Andrew D. Burnett Dr. John Kendrick Dr. John E. Cunningham Dr. Michael D. Hargreaves Dr. Tasmin Munshi Dr. Howell G. M. Edwards Prof. Edmund H. Linfield Prof. A. Giles Davies Prof. 《Chemphyschem》2010,11(2):368-378
The terahertz frequency spectrum of pentaerythritol tetranitrate (PETN) is calculated using Discover 1 with the COMPASS 2 force field, CASTEP[3] and PWscf. 4 The calculations are compared to each other and to terahertz spectra (0.3–3 THz) of crystalline PETN recorded at 4 K. A number of analysis methods are used to characterise the calculated normal modes. 相似文献
210.
Data fusion in multivariate calibration transfer 总被引:1,自引:0,他引:1
We report the use of stacked partial least-squares regression and stacked dual-domain regression analysis with four commonly used techniques for calibration transfer to improve predictive performance from transferred multivariate calibration models. The predictive performance from three conventional calibration transfer methods, piecewise direct standardization (PDS), orthogonal signal correction (OSC) and model updating (MUP), requiring standards measured on both instruments, was significantly improved from data fusion either by stacking of wavelet scales or by stacking of spectral intervals, as demonstrated by transfer of calibrations developed on near-infrared spectra of synthetic gasoline. Stacking did not produce as significant an improvement for calibration transfer using a finite impulse response (FIR) filter, but application of SPLS regression to FIR-transferred spectra improves predictive performance of the transferred model. 相似文献