全文获取类型
收费全文 | 21731篇 |
免费 | 3920篇 |
国内免费 | 3367篇 |
专业分类
化学 | 16517篇 |
晶体学 | 484篇 |
力学 | 1131篇 |
综合类 | 297篇 |
数学 | 2227篇 |
物理学 | 8362篇 |
出版年
2024年 | 50篇 |
2023年 | 319篇 |
2022年 | 544篇 |
2021年 | 644篇 |
2020年 | 745篇 |
2019年 | 876篇 |
2018年 | 685篇 |
2017年 | 693篇 |
2016年 | 949篇 |
2015年 | 1054篇 |
2014年 | 1182篇 |
2013年 | 1579篇 |
2012年 | 2014篇 |
2011年 | 1943篇 |
2010年 | 1577篇 |
2009年 | 1531篇 |
2008年 | 1732篇 |
2007年 | 1468篇 |
2006年 | 1464篇 |
2005年 | 1335篇 |
2004年 | 1074篇 |
2003年 | 847篇 |
2002年 | 886篇 |
2001年 | 701篇 |
2000年 | 578篇 |
1999年 | 441篇 |
1998年 | 274篇 |
1997年 | 212篇 |
1996年 | 192篇 |
1995年 | 172篇 |
1994年 | 179篇 |
1993年 | 139篇 |
1992年 | 93篇 |
1991年 | 109篇 |
1990年 | 74篇 |
1989年 | 74篇 |
1988年 | 70篇 |
1987年 | 34篇 |
1986年 | 46篇 |
1985年 | 69篇 |
1984年 | 36篇 |
1983年 | 26篇 |
1982年 | 31篇 |
1981年 | 40篇 |
1980年 | 27篇 |
1979年 | 33篇 |
1978年 | 21篇 |
1977年 | 28篇 |
1976年 | 28篇 |
1975年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
131.
35Cl NQR as well as heat capacity measurements of [(PyO)H][AuCl4] and its deuterated analog [(PyO)D][AuCl4] revealed successive phase transitions at 70.5 and 62.5 K, and at 71 and 63 K, respectively. The NQR frequency varied continuously through the upper transition point while discontinuously through the lower transition point. In the intermediate-temperature phase a remarkable decrease in the signal intensity was observed. These NQR observations as well as the feature of the heat capacity anomaly in which a broad peak is succeeded by a sharp peak with decreasing temperature suggest a possibility of normal-incommensurate-commensurate phase sequence. 相似文献
132.
本文利用武汉电离层观象台的加密频高图和三站Doppler图记录及新近提出的短波扰动反演方法,分析了1985年全球大气重力波联测(WAGS)期间10月18日这天白天的重力波扰动,发现在该日扰动中有两列不同形态的波列分别属于中尺度的内重力波和大尺度的导制重力波。本文还进一步估算了这两列重力波的水平传播参量,深入分析了它们的频谱结构的高度变化特征,发现了重力波功率谱谱峰的分裂和偏移等重要现象。本文结果表明,新的反演方法使电离层无线电汉诊断的简易短波实验系统,也能成为探测和研究重力波一类大尺度电离层动力过程的有效手段。 相似文献
133.
Yu Jun ZHU Jin Lian ZHANG Lian Fa HE 《数学学报(英文版)》2006,22(5):1321-1328
In this paper, we consider the shadowing and the inverse shadowing properties for C^1 endomorphisms. We show that near a hyperbolic set a C^1 endomorphism has the shadowing property, and a hyperbolic endomorphism has the inverse shadowing property with respect to a class of continuous methods. Moreover, each of these shadowing properties is also "uniform" with respect to C^1 perturbation. 相似文献
134.
Let ? be a primitive substitution on a two-letter alphabet {a,b} having two fixed points ξa and ξb. We show that the substitution ? is invertible if and only if one has ξa=abξ and ξb=baξ. To cite this article: Z.-X. Wen et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 727–731. 相似文献
135.
Hollow particles with interconnected cavities have been prepared by a simple modified suspension polymerization of acrylate monomers in the incorporation of a phase inversion process and polymerizable emulsifier. The morphology of particles has been characterized by scanning electron micrographs (SEMs). Based on observations made using an optical microscope equipped with a digital camera and SEM images of particles obtained under different conditions, the formation mechanisms for multiporous hollow particles are discussed. 相似文献
136.
Jun Hua YU Xue Song WANG Bao Wen ZHANG* Yi CAO Technical Institute of Physics Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2002,13(10)
Porphyrin derivatives attract much more interest in photodynamic therapy (PDT). Their importance as therapeutic drugs and targeting agents has been widely recognized1, and many of the efforts have been put towards crafting new porphyrin-based molecular entities to achieve enhanced tumor localization, better tissue penetration and increased singlet oxygen quantum yield2. The states of porphyrins in tissue models such as micelles, lipid bilayers are extensively investigated focusing more or l… 相似文献
137.
使用参数Dioid模块网络法,把含大量摄动参数的在普通极大代数意义下非线性状态空间模型在参数Dioid意义下线性化,在此基础上研究一类过程摄动系统的无阻塞鲁棒性.给出了有限缓冲串行生产系统在没有缓冲器下无阻塞的充要条件和充分条件. 相似文献
138.
139.
Recent experiments revealed that the dielectric dispersion spectrum of fission yeast cells in a suspension was mainly composed of two sub-dispersions. The low-frequency sub-dispersion depended on the cell length, while the high-frequency one was independent of it. The cell shape effect was simulated by an ellipsoidal cell model but the comparison between theory and experiment was far from being satisfactory. Prompted by the discrepancy, we proposed the use of spectral representation to analyze more realistic cell models. We adopted a shell-spheroidal model to analyze the effects of the cell membrane. It is found that the dielectric property of the cell membrane has only a minor effect on the dispersion magnitude ratio and the characteristic frequency ratio. We further included the effect of rotation of dipole induced by an external electric field, and solved the dipole-rotation spheroidal model in the spectral representation.Good agreement between theory and experiment has been obtained. 相似文献
140.
枸橼酸莫沙必利的合成 总被引:1,自引:0,他引:1
分别以邻羟基对氨基苯甲醇钠,对氟苯甲醛,邻苯二甲酰亚胺为起始原料,制得3个中间体,用其中2个中间体经偶合,环化后与第3个中间体反应,再经成盐制得产品,其摩尔总收率为31.5%。 相似文献