全文获取类型
收费全文 | 12674篇 |
免费 | 2089篇 |
国内免费 | 1761篇 |
专业分类
化学 | 9248篇 |
晶体学 | 164篇 |
力学 | 761篇 |
综合类 | 127篇 |
数学 | 1608篇 |
物理学 | 4616篇 |
出版年
2024年 | 45篇 |
2023年 | 179篇 |
2022年 | 392篇 |
2021年 | 421篇 |
2020年 | 439篇 |
2019年 | 448篇 |
2018年 | 406篇 |
2017年 | 389篇 |
2016年 | 556篇 |
2015年 | 584篇 |
2014年 | 741篇 |
2013年 | 924篇 |
2012年 | 1075篇 |
2011年 | 1213篇 |
2010年 | 874篇 |
2009年 | 893篇 |
2008年 | 1009篇 |
2007年 | 868篇 |
2006年 | 793篇 |
2005年 | 605篇 |
2004年 | 456篇 |
2003年 | 370篇 |
2002年 | 411篇 |
2001年 | 346篇 |
2000年 | 314篇 |
1999年 | 267篇 |
1998年 | 199篇 |
1997年 | 172篇 |
1996年 | 204篇 |
1995年 | 172篇 |
1994年 | 107篇 |
1993年 | 105篇 |
1992年 | 87篇 |
1991年 | 85篇 |
1990年 | 67篇 |
1989年 | 66篇 |
1988年 | 39篇 |
1987年 | 40篇 |
1986年 | 36篇 |
1985年 | 25篇 |
1984年 | 19篇 |
1983年 | 22篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1974年 | 4篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
利用球磨法制备石墨-六角氮化硼微晶混合物,并在6.1 GPa、800~1 500 ℃条件下与水进行高压反应,以便研究用水作触媒合成B-C-N三元化合物的可能性。通过对反应产物的XRD、XPS谱分析发现:高压下随着温度的升高,反应产物中出现再结晶石墨,其晶化程度逐渐提高;但没有出现再结晶六角氮化硼,也未出现立方氮化硼。在球磨不充分条件下,石墨-六角氮化硼混合物的XRD谱没有完全弥散,它们与水高压反应时,能观察到石墨与立方氮化硼分别结晶的现象,但都没有形成B-C-N晶化结构。 相似文献
52.
Jiangen Huang Guiqin Zhang Yuanhe Huang Decai Fang Deqing Zhang 《Journal of magnetism and magnetic materials》2006
A one-dimensional (1D) silver (I) complex of nitronyl nitroxide with fairly strong antiferromagnetic interaction, in which the metal ions are diamagnetic, is investigated by means of the ab initio crystal orbital method based on the density functional theory. The calculated values of the magnetic coupling constant (J) are close to the experimental measured J value in the periodic system. The magneto-structural correlation reveals that the existence of an antiferromagnetic coupling pathway along nitronyl nitroxide units via silver (I) ion in this system. The spin population distribution also shows the existence of spin delocalization along the ONCNO–Ag–ONCNO, which affords a rational interpretation for the antiferromagnetic interaction mechanism. 相似文献
53.
54.
Xi Nian FANG Jian Hua WANG 《数学学报(英文版)》2006,22(6):1819-1824
In this paper, we study the extension of isometries between the unit spheres of normed space E and C(Ω). We obtain that any surjective isometry between the unit spheres of normed space E and C(Ω) can be extended to be a linear isometry on the whole space E and give an affirmative answer to the corresponding Tingley's problem (where Ω be a compact metric space). 相似文献
55.
In this paper, we study a micro‐macro model for polymeric fluid. The system involves coupling between the macroscopic momentum equation and a microscopic evolution equation describing the combined effects of the microscopic potential and thermofluctuation. We employ an energetic variation procedure to explore the relation between the macroscopic transport of the particles and the induced elastic stress due to the microscopic structure. For the initial data not far from the equilibrium, we prove the global existence and uniqueness of classical solutions to the system. © 2006 Wiley Periodicals, Inc. 相似文献
56.
Gold in ores was determined by flame atomic absorption spectrometry following on-line preconcentration by sorbent extraction in a flow-injection system. The medium polarity adsorption resin Amberlite XAD-8 packed in a 220-μl micro-column was used to collect gold(III) from hydrochloric acid sample solutions for 40 s at 7.6 ml/min. Ethanol was used to elute the adsorbed analytes into the nebulizer. Optimization studies were made on sample loading rate, elution rate and sample acidity. Some possible interferences on the determination are discussed. A 35-fold enrichment was achieved at a sampling frequency of 60 h?1 and with an RSD of 1.4%. The detection limit (3σ) and 2 μg l?1. Results for gold in ore samples showed good agreement with those obtained using activated carbon adsorption preconcentration. The recoveries were 97–108%. 相似文献
57.
本文介绍了利用喷油脉宽大小的变化来分析电控发动机电控系统、燃油供给等系统故障的一种方法,在汽车故障检测与诊断中有着广泛的应用。 相似文献
58.
Features of the total disintegration events of heavyemulsion targets caused by 4.5A GeV/c16O
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Total disintegration events produced by 4.5\,A GeV/c $^{16}$O--AgBr interactions are
analysed to investigate the characteristics of secondary charged particles produced
in such collisions. The multiplicity distributions of grey, black, and relativistic
charged particles can be well represented by Gaussian distribution. The average
multiplicity of grey particles is found to increase with the mass of projectile
increasing, while that of black particles is found to decrease with the mass of
projectile increasing. This result is in good agreement with the prediction of
fireball model. Finally, the linear dependence between grey and black particles is
observed, but there is no distinct dependence between the production of relativistic
charged particles and the target excitation. 相似文献
59.
60.