全文获取类型
收费全文 | 60260篇 |
免费 | 9195篇 |
国内免费 | 6142篇 |
专业分类
化学 | 41219篇 |
晶体学 | 617篇 |
力学 | 3992篇 |
综合类 | 425篇 |
数学 | 6766篇 |
物理学 | 22578篇 |
出版年
2024年 | 546篇 |
2023年 | 1301篇 |
2022年 | 2101篇 |
2021年 | 2507篇 |
2020年 | 2746篇 |
2019年 | 2550篇 |
2018年 | 1852篇 |
2017年 | 1677篇 |
2016年 | 2583篇 |
2015年 | 2579篇 |
2014年 | 3154篇 |
2013年 | 4046篇 |
2012年 | 5124篇 |
2011年 | 5133篇 |
2010年 | 3461篇 |
2009年 | 3243篇 |
2008年 | 3555篇 |
2007年 | 3127篇 |
2006年 | 3039篇 |
2005年 | 2541篇 |
2004年 | 2126篇 |
2003年 | 1652篇 |
2002年 | 1543篇 |
2001年 | 1291篇 |
2000年 | 1150篇 |
1999年 | 1343篇 |
1998年 | 1064篇 |
1997年 | 984篇 |
1996年 | 1088篇 |
1995年 | 930篇 |
1994年 | 853篇 |
1993年 | 705篇 |
1992年 | 654篇 |
1991年 | 548篇 |
1990年 | 481篇 |
1989年 | 368篇 |
1988年 | 324篇 |
1987年 | 279篇 |
1986年 | 220篇 |
1985年 | 225篇 |
1984年 | 185篇 |
1983年 | 158篇 |
1982年 | 105篇 |
1981年 | 89篇 |
1980年 | 60篇 |
1979年 | 35篇 |
1978年 | 27篇 |
1976年 | 27篇 |
1975年 | 32篇 |
1974年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
Wu Jinxiu Qi Yuanhao Liu Zhaogang Jia Huiling Hu Yanhong Feng Fushan 《Journal of solution chemistry》2022,51(1):14-30
Journal of Solution Chemistry - The interaction between Dy(Ш)/Rutin complexes and bovine serum albumin (BSA) was studied by fluorescence, ultraviolet (UV) absorption, three-dimensional... 相似文献
82.
Li Yang Fu Xuan Li Xu-Xin Zhang Fang Wu Qiang Wang Yun Yan Ze-Yi 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(2):877-888
Journal of Radioanalytical and Nuclear Chemistry - In this study, the imidazole-based poly(ionic liquid)s (PILs) synthesized by one step method has been applied for the enrichment and recovery of... 相似文献
83.
生物瓣膜应力的数值模拟 总被引:2,自引:0,他引:2
应用有限元方法分析了瓣架的材料特性、瓣叶的材料特性和瓣叶的钙化等因素对瓣叶的应力分布的影响。分析结果表明:采用全弹性材料的瓣架将改善瓣叶的应力分布,最大应力区域将远离接缝部位;将生物瓣瓣叶材料简化为拟线弹性材料时,对瓣叶最大主应力等值线的分布影响不大,计算结果在一定范围内存在差异;当瓣叶出现钙化时,钙化点及其周围产生应力集中,促进钙化的进一步加剧。 相似文献
84.
GPS误差模型参数估计的Hopfield神经网络方法 总被引:2,自引:2,他引:2
本文首先建立了GPS误差模型。然后,利用Hopfield神经网络(HNN)方法对误差模型参数进行了估计,并给出了其硬件实现方法。将估计结果与传统的最小二乘(LS)估计进行比较,证明了神经网络方法的有效性。 相似文献
85.
This paper reports a numerical study on buoyancy-aided steady convection heat transfer from a horizontal cylinder situated in a vertical adiabatic duct. Numerical results have been generated forH
1/D=2.5, 4, 8,H/D=8, 16, 24,S/D=2, 4, 6, 20Re60, andRi up to 4. The placing of a horizontal cylinder in a vertical duct of smaller width results in significantly enhanced pure forced convection due to the blockage effect, but degrades appreciably the extent of buoyancy-aided enhancement in the heat transfer rate. Nevertheless, the presence of a vertical duct leads to an overall enhancement of mixed convection heat transfer coefficient relative to that without the confining duct. Moreover, the average Nusselt number is rather insensitive to the variation of either the position of the cylinder in the duct or the duct height in the investigated ranges of these geometric parameters.Dieser Artikel beschreibt eine numerische Studie über auftriebsunterstützte konvektive Wärmeübertragung von einem horizontalen Zylinder der in einem vertikalen adiabaten Kanal positioniert ist. Die numerischen Ergebnisse sind fürH
1/D=2, 5, 4, 8,H/D=8, 16, 24,S/D=2, 4, 6 sowie 20Re60 undRi bis 4 berechnet worden. Die Anordnung des horizontalen Zylinders in einem schmaleren vertikalen Kanal führt auf Grund des Blockierungs-effektes zu einem deutlichen Anstieg der reinen Zwangskonvektion. Aber sie verschlechtert deutlich den Betrag der auftriebsbedingten Steigerung in der Wärmeübergangsrate. Trotzdem führt die Anwesenheit des vertikalen Kanals insgesamt zu einer Steigerung des Wärmeübergangskoeffizienten bei Mischkonvektion im Vergleich zur Abwesenheit des begrenzenden Kanals. Des weiteren ist die durchschnittliche Nusseltzahl von der Variation der Zylinderposition im Kanal oder der Kanalhöhe abhängig. 相似文献
86.
A crystallographic creep damage constitutive model is developed for nickel-base directionally solidified superalloys. The rates of material degradation and grain boundary void growth are considered. The governing parameters are determined from the creep test data of single crystals and directionally solidified superalloys with a crystallographic orientation. A finite element program is used to analyze the creep damage behavior of nickel-base directionally solidified superalloys for different crystallographic orientations. The results depend on the number of grains modelled and compare well with the experimental data. 相似文献
87.
88.
Theodore Yao-tsu Wu 《Acta Mechanica Sinica》1995,11(4):289-306
The bidirectional long-wave model introduced by Wu (1994)[1] and Yih & Wu (1995)[2] is applied to evaluate interactions between multiple solitary waves progressing in both directions in a uniform channel of
rectangular cross-section and undergoing collisions of two classes, one being head-on and the other overtaking collisions
between these solitons. For a binary head-on collision, the two interacting solitary waves are shown to merge during a phase-locking
period from which they reemerge separated, each asymptotically recovering its own initial identity while both being retarded
in phase from their original pathlines. For a binary overtaking collision between a soliton of height α1 overtaking a weaker one of height α1, the two solition peaks are shown to either pass through each other or remain separated throughout the encounter according
as α1/α2 or <3, respectively. With no phase locking during the overtaking, the two solitary waves re-emerge afterwards with their
initial forms recovered and with the stronger wave being advanced whereas the weaker one retarded in phase from their original
pathlines. By extension, the theory is generalized to apply to uniform channels of arbitrary cross-sectional shape.
The Inaugural Pei-Yuan Chou Memorial Lecture, presented at The Sixth Asian Congress of Fluid Mechanics. Singapore, 21–26 May
1995 相似文献
89.
This paper deals with non-linear oscillation of a conservative system having inertia and static non-linearities. By combining the linearization of the governing equation with the method of harmonic balance, we establish analytical approximate solutions for the non-linear oscillations of the system. Unlike the classical harmonic balance method, linearization is performed prior to proceeding with harmonic balancing, thus resulting in a set of linear algebraic equations instead of one of non-linear algebraic equations. Hence, we are able to establish analytical approximate formulas for the exact frequency and periodic solution. These analytical approximate formulas show excellent agreement with the exact solutions, and are valid for small as well as large amplitudes of oscillation. 相似文献
90.
In order to discuss the agreement of the ellipsoidal statistical BGK (ES-BGK) model with the Boltzmann equation, Burnett equations are computed by means of the second-order Chapman-Enskog expansion of the ES-BGK model. It is found that the Burnett equations for the ES-BGK model with the correct Prandtl number are identical to the Burnett equations for the Boltzmann equation for Maxwell molecules (fifth-order power potentials). However, for other types of particle interaction, the Boltzmann Burnett equations cannot be reproduced from the ES-BGK model.Furthermore, the linear stability of the ES-BGK Burnett equations is discussed. It is shown that the ES-BGK Burnett equations are linearly stable for Prandtl numbers of
and for
, while they are linearly unstable for
and
.Received: 29 April 2003, Accepted: 20 June 2003PACS:
510.10.-y, 47.45.-n
Correspondence to: Y. Zheng 相似文献