全文获取类型
收费全文 | 360篇 |
免费 | 10篇 |
国内免费 | 2篇 |
专业分类
化学 | 223篇 |
晶体学 | 4篇 |
力学 | 16篇 |
数学 | 62篇 |
物理学 | 67篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 13篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 9篇 |
2016年 | 13篇 |
2015年 | 6篇 |
2014年 | 14篇 |
2013年 | 34篇 |
2012年 | 20篇 |
2011年 | 19篇 |
2010年 | 14篇 |
2009年 | 22篇 |
2008年 | 22篇 |
2007年 | 14篇 |
2006年 | 20篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 6篇 |
2002年 | 12篇 |
2001年 | 2篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1967年 | 2篇 |
1963年 | 1篇 |
1939年 | 2篇 |
1936年 | 2篇 |
1925年 | 1篇 |
1900年 | 1篇 |
排序方式: 共有372条查询结果,搜索用时 15 毫秒
71.
The aim of this paper is to investigate the fundamental problems of retardation and radiation caused by non-uniformly moving point sources using the theories of electrodynamics and elastodynamics. This paper investigates and compares the retarded electromagnetic fields and the retarded elastodynamic fields. For the non-uniform motion of a general point source, the Liénard–Wiechert type potentials and the radiation and nonradiation fields are derived for a point charge and for a point force. 相似文献
72.
Iulia M. Lazar Milton L. Lee 《Journal of the American Society for Mass Spectrometry》1999,10(3):261-264
The effect of the electrospray ionization (ESI) needle voltage on the electroosmotic flow (EOF) in capillary electrophoresis (CE)-mass spectrometry (MS) was investigated. The radial electric field that penetrates across the CE capillary wall imposed by the ESI needle voltage modifies the typical EOF. This effect was investigated for buffers commonly used in CE-MS. Variations as high as ±30% were observed. 相似文献
73.
Channeling of fast ions through the bent carbon nanotubes:The extended two-fluid hydrodynamic model
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We investigate the interactions of charged particles with straight and bent single-walled carbon nanotubes(SWNTs)under channeling conditions in the presence of dynamic polarization of the valence electrons in carbon. This polarization is described by a cylindrical, two-fluid hydrodynamic model with the parameters taken from the recent modelling of several independent experiments on electron energy loss spectroscopy of carbon nano-structures. We use the hydrodynamic model to calculate the image potential for protons moving through four types of SWNTs at a speed of 3 atomic units. The image potential is then combined with the Doyle–Turner atomic potential to obtain the total potential in the bent carbon nanotubes.Using that potential, we also compute the spatial and angular distributions of protons channeled through the bent carbon nanotubes, and compare the results with the distributions obtained without taking into account the image potential. 相似文献
74.
Dong-Sheng Guo Vanya D. Uzunova Khaleel I. Assaf Alexandra I. Lazar Yu Liu 《Supramolecular chemistry》2016,28(5-6):384-395
AbstractThe driving forces of association between three different families of macrocycles as hosts, namely cyclodextrins (α-, β-, and γ-), p-sulfonatocalix[n]arenes (n = 4–6) as well as cucurbit[n]urils (n = 6–8), and three different bicyclic azoalkane homologues as guests, namely 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH), 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) as well as 2,3-diazabicyclo[2.2.3]non-2-ene (DBN), were examined by means of calorimetric titrations, NMR spectroscopy and molecular dynamics simulation, all in aqueous solution. The small, spherical and uncharged guests preferably bind inside the cavities of the medium sized hosts. The inclusion complexation by β-cyclodextrin and p-sulfonatocalix[4]arene shows medium binding affinities (millimolar), while cucurbit[7]uril macrocycle shows very strong binding (micromolar). For all types of macrocycles, the complex formation is enthalpically driven (ΔH° < 0), accompanied by slightly unfavourable entropy changes (ΔS° < 0). The results are discussed in terms of the flexibility of the hosts, the hydrophobic character of their cavities and the release of high-energy water upon binding, and generalised by including two additional guests, the ketones cyclopentanone and (+)-camphor. 相似文献
75.
Yunierkis Pérez-Castillo Maykel Cruz-Monteagudo Cosmin Lazar Jonatan Taminau Mathy Froeyen Miguel Ángel Cabrera-Pérez Ann Nowé 《Molecular diversity》2014,18(3):637-654
Antibiotic resistance has increased over the past two decades. New approaches for the discovery of novel antibacterials are required and innovative strategies will be necessary to identify novel and effective candidates. Related to this problem, the exploration of bacterial targets that remain unexploited by the current antibiotics in clinical use is required. One of such targets is the \(\beta \) -ketoacyl-acyl carrier protein synthase III (FabH). Here, we report a ligand-based modeling methodology for the virtual-screening of large collections of chemical compounds in the search of potential FabH inhibitors. QSAR models are developed for a diverse dataset of 296 FabH inhibitors using an in-house modeling framework. All models showed high fitting, robustness, and generalization capabilities. We further investigated the performance of the developed models in a virtual screening scenario. To carry out this investigation, we implemented a desirability-based algorithm for decoys selection that was shown effective in the selection of high quality decoys sets. Once the QSAR models were validated in the context of a virtual screening experiment their limitations arise. For this reason, we explored the potential of ensemble modeling to overcome the limitations associated to the use of single classifiers. Through a detailed evaluation of the virtual screening performance of ensemble models it was evidenced, for the first time to our knowledge, the benefits of this approach in a virtual screening scenario. From all the obtained results, we could arrive to a significant main conclusion: at least for FabH inhibitors, virtual screening performance is not guaranteed by predictive QSAR models. 相似文献
76.
Using gradient elasticity, we give in this Letter the non-singular fields produced by arbitrary dislocation loops in isotropic media. We present the ‘modified’ Mura, Peach–Koehler and Burgers formulae in the framework of gradient elasticity theory. 相似文献
77.
M. El Haddad M. Soukri S. Lazar A. Bennamara G. Guillaumet M. Akssira 《Journal of heterocyclic chemistry》2000,37(5):1247-1252
Pyrazolo‐[3,4‐d]pyrimidine‐4,6‐diones 5 and pyrazolo[4,3‐d]pyrimidine‐5,7‐diones 7 were synthesized by Curtius rearrangement of pyrazolic mono‐esters 2 and 3 followed by hetero‐cyclization via the ureas derivatives 4 and 6 under alkaline conditions. 相似文献
78.
79.
80.
M. Lazar H. Vang P. Brosselard C. Raynaud P. Cremillieu J.-L. Leclercq A. Descamps S. Scharnholz D. Planson 《Superlattices and Microstructures》2006,40(4-6):388
SiC is currently an important topic in power devices. This new technology leads to lower power losses, faster switching, and higher working temperature. The design of SiC power devices requires the integration of edge termination techniques to obtain a high blocking voltage. The mesa structure approach is one well-established method. It could be used alone or in combination with a Junction Termination Extension (JTE). The mesa consists of a structure that removes material around the pn-junction. Due to the strong Si–C bonds, conventional chemical–wet etching solutions are inefficient on SiC, so plasma methods are required to etch SiC.The presented work is based on the use of an RIE reactor with an SF6/ O2 plasma. Its geometry structure and parameters were optimized. An etch rate of 0.35 μm/min was obtained without any trenching phenomenon. Trenches deeper than 10 μm deep were realized with a nickel etching mask that shows a high selectivity. AFM analysis revealed an etched surface as smooth as the initial one. 相似文献