全文获取类型
收费全文 | 4809篇 |
免费 | 826篇 |
国内免费 | 315篇 |
专业分类
化学 | 1022篇 |
晶体学 | 19篇 |
力学 | 978篇 |
综合类 | 117篇 |
数学 | 2250篇 |
物理学 | 1564篇 |
出版年
2024年 | 5篇 |
2023年 | 36篇 |
2022年 | 75篇 |
2021年 | 95篇 |
2020年 | 138篇 |
2019年 | 152篇 |
2018年 | 157篇 |
2017年 | 189篇 |
2016年 | 221篇 |
2015年 | 214篇 |
2014年 | 245篇 |
2013年 | 341篇 |
2012年 | 268篇 |
2011年 | 312篇 |
2010年 | 233篇 |
2009年 | 240篇 |
2008年 | 261篇 |
2007年 | 263篇 |
2006年 | 263篇 |
2005年 | 287篇 |
2004年 | 224篇 |
2003年 | 221篇 |
2002年 | 251篇 |
2001年 | 183篇 |
2000年 | 179篇 |
1999年 | 160篇 |
1998年 | 129篇 |
1997年 | 101篇 |
1996年 | 90篇 |
1995年 | 75篇 |
1994年 | 56篇 |
1993年 | 33篇 |
1992年 | 40篇 |
1991年 | 26篇 |
1990年 | 23篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 15篇 |
1986年 | 18篇 |
1985年 | 15篇 |
1984年 | 16篇 |
1983年 | 5篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1959年 | 3篇 |
排序方式: 共有5950条查询结果,搜索用时 15 毫秒
141.
Thomas Waldmann Jens Klein Prof. Dr. Harry E. Hoster Prof. Dr. R. Jürgen Behm 《Chemphyschem》2013,14(1):162-169
Investigating the dynamics in an adlayer of the oligopyridine derivative 2‐phenyl‐4,6‐bis(6‐(pyridine‐2‐yl)‐4‐(pyridine‐4‐yl)pyridine‐2‐yl)pyrimidine (2,4′‐BTP) on Ag(111) by fast scanning tunneling microscopy (video‐STM), we found that rotating 2,4′‐BTP adsorbates coexist in a two‐dimensional (2D) liquid phase (β‐phase) in a dynamic equilibrium with static adsorbate molecules. Furthermore, exchange between an ordered phase (α‐phase) and β‐phase leads to fluctuations of the domain boundary on a time scale of seconds. Quantitative evaluation of the temperature‐dependent equilibrium between rotating and static adsorbates, evaluated from a large number of STM images, gains insight into energetic and entropic stabilization and underlines that the rotating adsorbate molecules are stabilized by an entropy contribution, which is compatible with that derived by using statistical mechanics. The general validity of the concept of entropic stabilization of rotating admolecules, favoring rotation already at room temperature, is tested for other typical small, mid‐size and large adsorbates. 相似文献
142.
Dr. Adrien Bourdolle Dr. Mustapha Allali Dr. Anthony D'Aléo Dr. Patrice L. Baldeck Dr. Kenji Kamada Prof. J. A. Gareth Williams Dr. Hubert Le Bozec Dr. Chantal Andraud Dr. Olivier Maury 《Chemphyschem》2013,14(14):3361-3367
The synthesis of tris(2‐thenoyltrifluoroacetonate)lanthanide(III) complexes featuring a diethylaminostyryl‐2,2′‐bipyridine coligand was achieved for lanthanum; the near‐infrared (NIR) emitters neodymium, erbium, and ytterbium; and the transition‐metal yttrium. The photophysical properties were thoroughly studied, and it was demonstrated that the conjugated bipyridine ligand acts as a good antenna for the sensitization of the NIR emitters. The two‐photon absorption (TPA) properties of all five complexes were investigated by using both two‐photon excited fluorescence and the Z‐scan method. We demonstrate that the nature of the rare earth ion has almost no influence on the TPA properties centered on the conjugated bipyridyl ligand. Finally, we show that YbIII is sensitized by a two‐photon antenna effect, and that NdIII is mostly sensitized by a one‐photon process involving direct excitation of forbidden f–f transitions. 相似文献
143.
《Journal of Dispersion Science and Technology》2013,34(6):655-658
Microstructure and phase behavior of decyltriethylammonium bromide (C10NE)/sodium decylsulfonate (C10SO3)/poly(ethylene oxide) (PEO)/water quaternary systems were studied by freeze‐fracture transmission electron microscopy, small angle X‐ray diffraction, and dynamic light scattering methods. Aqueous two‐phase systems (ATPS) could be prepared by properly mixing the aqueous solution of PEO and equimolar mixed C10NE and C10SO3. It was shown that the top phase of the ATPS was surfactant‐enriched and mainly composed of multi‐lamellar structure, while the bottom phase of the ATPS was polymer‐enriched in which some vesicles were observed. 相似文献
144.
利用微型流化床动力学分析仪研究了两相流条件下无烟煤粉的燃烧反应机理和动力学特征,并与热重法所得结果进行比较分析。结果表明,当温度大于850℃时,煤粉燃烧机理发生了变化,燃烧气态产物的生成比例也随之改变;当气速大于0.10 m/s时,气体扩散限制基本被消除,煤粉燃烧反应速率主要受界面化学反应控制;煤粉燃烧反应速率随着氧气分压的增大呈幂函数形式增长,且氧气分压对煤粉静置燃烧的影响更加显著。煤氧两相流燃烧的表观活化能与静置燃烧相比降低了49 kJ/mol,相同温度条件下两相流燃烧的界面化学反应阻力也明显小于热重法测试结果。 相似文献
145.
The liquid crystalline behaviour of methyl-6-O-(n-dodecanoyl)-α-D-glucopyranoside, 1, has been characterised using X-ray diffraction and variable temperature Fourier transform infrared (FTIR spectroscopy). 1 exhibits a monotropic interdigitated smectic A phase consisting of bilayers in which the alkyl chains are overlapped. The crystal–isotropic transition is accompanied by a pronounced decrease in the strength of the hydrogen bonding network involving the sugar groups resulting in a marked change in the environment of the alkyl chains. The isotropic phase consists of disordered smectic-like domains stabilised via hydrogen bonding between the sugar groups. At the transition to the smectic A phase, a subtle change in hydrogen bonding is observed which is manifested by a change in the temperature dependence of the OH stretching peak position in the FTIR spectrum. On crystallisation, the strong hydrogen bonding network is re-established accompanied by a change in the conformational distribution of the alkyl chains. A model is proposed in which a combination of hydrogen bonding (enthalpic effects) and conformational arrangements (entropic effects) promotes initially the formation of smectic-like domains in the isotropic phase and subsequently stabilises the smectic A phase by inhibiting the microphase separation leading to the crystal phase. 相似文献
146.
147.
148.
考虑了带二元连续变利息力的Sparre Andersen风险模型.研究了积累值盈余过程的表达式与性质;在利率递增环境下,利用推广后的调节系数方程组与递归技术推导了最终破产概率的上界,结论表明得到的破产概率上界是更为一般的Lundberg指数上界. 相似文献
149.
150.
Peggy Cénac Brigitte Chauvin Frédéric Paccaut Nicolas Pouyanne 《Random Structures and Algorithms》2015,46(1):117-141
Common assumptions on the source producing the words inserted in a suffix trie with n leaves lead to a height and saturation level. We provide an example of a suffix trie whose height increases faster than a power of n and another one whose saturation level is negligible with respect to . Both are built from VLMC (Variable Length Markov Chain) probabilistic sources and are easily extended to families of tries having the same properties. The first example corresponds to a “logarithmic infinite comb” and enjoys a non uniform polynomial mixing. The second one corresponds to a “factorial infinite comb” for which mixing is uniform and exponential. © 2013 Wiley Periodicals, Inc. Random Struct. Alg., 46, 117–141, 2015 相似文献