全文获取类型
收费全文 | 7082篇 |
免费 | 1011篇 |
国内免费 | 267篇 |
专业分类
化学 | 4085篇 |
晶体学 | 47篇 |
力学 | 512篇 |
综合类 | 32篇 |
数学 | 370篇 |
物理学 | 3314篇 |
出版年
2024年 | 8篇 |
2023年 | 58篇 |
2022年 | 103篇 |
2021年 | 159篇 |
2020年 | 185篇 |
2019年 | 218篇 |
2018年 | 169篇 |
2017年 | 165篇 |
2016年 | 306篇 |
2015年 | 263篇 |
2014年 | 321篇 |
2013年 | 667篇 |
2012年 | 372篇 |
2011年 | 385篇 |
2010年 | 304篇 |
2009年 | 396篇 |
2008年 | 417篇 |
2007年 | 477篇 |
2006年 | 427篇 |
2005年 | 290篇 |
2004年 | 317篇 |
2003年 | 313篇 |
2002年 | 234篇 |
2001年 | 216篇 |
2000年 | 217篇 |
1999年 | 170篇 |
1998年 | 212篇 |
1997年 | 105篇 |
1996年 | 101篇 |
1995年 | 81篇 |
1994年 | 94篇 |
1993年 | 75篇 |
1992年 | 64篇 |
1991年 | 57篇 |
1990年 | 34篇 |
1989年 | 58篇 |
1988年 | 44篇 |
1987年 | 31篇 |
1986年 | 23篇 |
1985年 | 22篇 |
1984年 | 39篇 |
1983年 | 16篇 |
1982年 | 25篇 |
1981年 | 20篇 |
1980年 | 16篇 |
1979年 | 20篇 |
1978年 | 16篇 |
1977年 | 8篇 |
1976年 | 13篇 |
1973年 | 11篇 |
排序方式: 共有8360条查询结果,搜索用时 15 毫秒
61.
此文报道了H+、H+2和H+3离子通过碳膜后,在其中产生的各种微量产物的测量结果.讨论了离子与碳膜作用中的电荷交换过程.分析了这些微量产物的形成机理.实验证明在产物的形成中电荷交换过程起关键作用.研究了离子与碳膜作用中的团簇效应和尾流效应. 相似文献
62.
对原子氢在Be(1010)薄膜表面的吸附性质做了第一性原理计算研究.根据原子面间距的不同,可把Be(1010)表面分为两种.计算结果表明,原子氢在这两种表面上的吸附性质显著不同.为阐明和分析这些不同,系统计算和分析了Be(1010)薄膜的表面电子结构、电子功函数、平均静电势和局域电荷密度.这些物理量都自洽地表明,吸附过程中原子氢和表面铍原子间的电荷转移过程对于两种表面是完全不同的.对于L型表面来说,电荷由吸附原子氢向表面Be原子层转移,而对于S型表面而言,电荷转移过程恰恰相反.
关键词:
表面能
功函数
量子尺度效应 相似文献
63.
Nobuaki Kanamaru 《Journal of luminescence》2002,96(1):5-35
Time-resolved fluorescence spectra of a title molecule (with benzene and aliphatic amine parts) in various media, after excitation by several lasers were observed to complement the previous work by conventional spectroscopy [N. Kanamaru, J. Tanaka, J. Phys. Chem. 95 (1991) 6441]. Though complex with many new features, the results were roughly consistent with the previous ones. The significant conclusions are as follows: (1) The emission to be ascribed to the amine (N) part, with more than one component (of nN and aN types) is observed not only for the acetonitrile solution (as previously reported) but also for all the other media. (2) Contrary to the case of a nonpolar hexane solution, both of N fluorescences in the other media reveal unusually long-lived decay components. This can be interpreted by assuming the so-called charge-transfer-to-solvent (CTTS) state that is nonfluorescent and lies just below the fluorescent state. (3) This observation in the protic media can also be taken as another evidence of the peculiar hydrogen bonding between this amine and the protic solvent molecules [N. Kanamaru, J. Tanaka, J. Phys. Chem. 95 (1991) 6441]. (4) Thus, the unexpectedly large quantum yields of N fluorescences in the polar media are now interpreted as arising due to the slow S1N→(CTTS)→S0 internal conversions. 相似文献
64.
荧光光谱法研究蛋白质构象的电磁-温度协同效应 总被引:1,自引:1,他引:0
长期以来电磁生物效应受到人们普遍关注,近年来从各个角度进行了相关研究。电磁-温度协同效应是当前的热点。本研究通过电磁场及温度协同对蛋白质影响的研究,发现蛋白质在电磁场作用下的不可逆变性,而且这种变性也遵循Arrhenius规律,并进一步得出电磁-温度协同作用的蛋白质变性模型。本文从分子反应动力学的角度解释了电磁-温度协同效应,并对非热效应作了一定的探讨。 相似文献
65.
M. A. Macrì C. Del Gratta L. Di Donato S. Di Luzio G. L. Romani S. Della Penna A. Pasquarelli 《Il Nuovo Cimento D》1994,16(5):425-432
Summary A preliminary study is here reported on a new potential marker for biomagnetic measurements. The marker consists of superparamagnetic
polymer microspheres which were detected in the presence of external steady magnetic fields by means of an r.f.-SQUID magnetometer.
The particles were prepared in samples differing in the concentration value and immersed in a homogeneous magnetic field of
variable intensity. A simple model was taken into account for the distribution of the microspheres in the samples, so that
the theoretical values were compared to the marker field values measured by the biomagnetic sensor. The overall sensitivity
of the experimental apparatus and the minimum concentration value of the marker were then estimated. 相似文献
66.
I. Ortalli G. Pedrazzi K. Jiang X. Zhang C. Carlo-Stella V. Rizzoli 《Il Nuovo Cimento D》1992,14(4):351-358
Summary A new approach to cancer treatment using low-energy gamma-rays is discussed. Cultures of bone marrow mononuclear cells collected
from normal donors and patients with chronic myelogenous leukaemia have been studied after the addition of hematin, at different
concentrations, and irradiation by a M?ssbauer gamma-ray source. Growth stimulation has been observed when hematin is added
to normal bone marrow cultures, while growth inhibition is observed when hematin is added to leukaemic cultures. The effect
becomes then more pronounced when hematin is used in combination with M?ssbauer gamma-rays. 相似文献
67.
The features of interaction of a spherical metallic particle with a rarefied thermal plasma flow due to the presence o charges-electrons and ions in the gaseous phase-are considered. Analytical expressions describing charge, momentum, and energy exchange between the plasma and the particle für the cases of strong and weak Debye screening are obtained. It is illustrated that the efficiency of particle heating in the plasma considerably grows as compared with a hot molecular gas due to participation of electrons and ions in file transfer processes. 相似文献
68.
69.
R_FN(O )R_F和R_FNO的F113溶液在室温下与一系列的对位取代苯甲醛反应,得到稳定的对位取代苯甲酰基全氟烷基氮氧自由基。由△a_N和△a_F~β的σ单参数相关以及△a_N与σ和σ 双参数相关表明:极性效应是影响氟烷基酰基氮氧自由基中氮原子自旋密度变化的主要因素,而自旋离域效应的影响是很小的。 相似文献
70.