全文获取类型
收费全文 | 6340篇 |
免费 | 564篇 |
国内免费 | 677篇 |
专业分类
化学 | 2543篇 |
晶体学 | 157篇 |
力学 | 744篇 |
综合类 | 60篇 |
数学 | 966篇 |
物理学 | 3111篇 |
出版年
2024年 | 16篇 |
2023年 | 79篇 |
2022年 | 84篇 |
2021年 | 100篇 |
2020年 | 135篇 |
2019年 | 108篇 |
2018年 | 107篇 |
2017年 | 154篇 |
2016年 | 203篇 |
2015年 | 171篇 |
2014年 | 318篇 |
2013年 | 439篇 |
2012年 | 341篇 |
2011年 | 397篇 |
2010年 | 335篇 |
2009年 | 445篇 |
2008年 | 416篇 |
2007年 | 459篇 |
2006年 | 354篇 |
2005年 | 394篇 |
2004年 | 351篇 |
2003年 | 255篇 |
2002年 | 241篇 |
2001年 | 192篇 |
2000年 | 173篇 |
1999年 | 173篇 |
1998年 | 156篇 |
1997年 | 153篇 |
1996年 | 94篇 |
1995年 | 110篇 |
1994年 | 83篇 |
1993年 | 78篇 |
1992年 | 86篇 |
1991年 | 47篇 |
1990年 | 40篇 |
1989年 | 40篇 |
1988年 | 38篇 |
1987年 | 35篇 |
1986年 | 30篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1982年 | 16篇 |
1981年 | 24篇 |
1980年 | 8篇 |
1979年 | 21篇 |
1978年 | 13篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1973年 | 2篇 |
排序方式: 共有7581条查询结果,搜索用时 15 毫秒
31.
In this paper, we have developed an analytical model to study the temperature distributions in IR optical materials heated by laser pulses. Our model takes into account the two-photon absorption (TPA). The calculations are based on a three-dimensional model of heat diffusion in solids using the integral transform method. We find out the rigorous analytical expression of the thermal field when one considers both one- and two-photon absorption. The model is valid for any laser–solid system whose interaction can be described by the generalized Beer–Lambert law. Specific results are presented for an application of the model to ZnSe sample. We find out that TPA can produce detectable temperature variation. 相似文献
32.
33.
A.D. Bykov V.N. Saveliev C. Camy-Peyret A. Valentin 《Journal of Molecular Spectroscopy》2004,224(2):164-175
Forty-seven N2 broadened water vapor line-widths have been measured in the 1845-2140 cm−1 spectral range with a Fourier Transform spectrometer in the 258-330 K temperature range at a spectral resolution of 0.005 cm−1 for the lines with upper state rotational quantum number up to 16. The measured exponents of the temperature dependence of the width exhibit a large range of values from 1.60 to −0.86. Theoretical calculations were made using a semi-empirical technique based on the Anderson theory. The calculated broadening coefficients as well as the temperature exponents for the half-width agree satisfactory with measured values. 相似文献
34.
This paper considers a new approach to a priori sparsification of the sparsity pattern of the factorized approximate inverses (FSAI) preconditioner using the so‐called vector aggregation technique. The suggested approach consists in construction of the FSAI preconditioner to the aggregated matrix with a prescribed sparsity pattern. Then small entries of the computed ‘aggregated’ FSAI preconditioning matrix are dropped, and the resulting pointwise sparsity pattern is used to construct the low‐density block sparsity pattern of the FSAI preconditioning matrix to the original matrix. This approach allows to minimize (sometimes significantly) the construction costs of low‐density high‐quality FSAI preconditioners. Numerical results with sample matrices from structural mechanics and thin shell problems are presented. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
35.
36.
Werner WinterGünther W.H Höhne 《Thermochimica Acta》2003,403(1):43-53
A method for measuring heat capacities of small samples using a chip-calorimeter and a heat pulse technique is described. The theoretical background to calculate the heat transport properties and the heat capacity of the sample from the pulse response function is given. Problems and potentials of the method are discussed. An example is given. 相似文献
37.
在电流及温度分布满足“不变性”原理的基础上,本文分析了等离子体中心热区的能量平衡,求出了电子热传导系数,根据实验数据拟合出HL-1装置电子热传导系数的定标关系为X_e=6.8(n_(eq1))~(-1.2)。此关系与其他托卡马克装置的结果类似。 相似文献
38.
39.
停流—荧光动力学分析法测定痕量钛的研究 总被引:3,自引:1,他引:2
利用自行组装的停流-荧光动力学分析仪,采用停流法汇合流体动力注入技术,研究了钛与3.5-二溴水杨基荧光酮的荧光增强动力学反应性质,讨论了流速、进样时间对方法灵敏度和精密度的影响,提出了一个快速、简便、精确测定钛的分析方法,并用于稀土样品及合成样品中痕量钛的测定.方法检测限为8×10~(-3)ppm,大多数元素的干扰均可用动力学方法消除. 相似文献
40.
The occurrence of charge on recoil56Mn produced by the (n,γ) reaction in polycrystalline potassium permanganate has been examined using the ‘charge plate technique’.
From considerations of capture gamma ray decay schemes and internal conversion it appears that, in a condensed medium, the
recoil atom develops charge after losing much of its initial kinetic energy which allows collection on charged electrodes.
Preliminary findings were presented at the International Symposium on Radiochemistry and Radiation Chemistry, RC-41 BARC,
Bombay, Feb. 4–6 (1991). 相似文献