全文获取类型
收费全文 | 1208篇 |
免费 | 55篇 |
国内免费 | 6篇 |
专业分类
化学 | 1049篇 |
晶体学 | 5篇 |
力学 | 11篇 |
数学 | 72篇 |
物理学 | 132篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 26篇 |
2021年 | 51篇 |
2020年 | 53篇 |
2019年 | 37篇 |
2018年 | 45篇 |
2017年 | 24篇 |
2016年 | 53篇 |
2015年 | 52篇 |
2014年 | 43篇 |
2013年 | 86篇 |
2012年 | 89篇 |
2011年 | 135篇 |
2010年 | 60篇 |
2009年 | 67篇 |
2008年 | 68篇 |
2007年 | 71篇 |
2006年 | 68篇 |
2005年 | 53篇 |
2004年 | 43篇 |
2003年 | 26篇 |
2002年 | 21篇 |
2001年 | 13篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有1269条查询结果,搜索用时 15 毫秒
71.
Prof. Dr. Evgeny V. Tretyakov Dr. Svetlana I. Zhivetyeva Dr. Pavel V. Petunin Dmitry E. Gorbunov Prof. Dr. Nina P. Gritsan Prof. Dr. Irina Yu. Bagryanskaya Dr. Artem S. Bogomyakov Dr. Pavel S. Postnikov Dr. Maxim S. Kazantsev Prof. Dr. Marina E. Trusova Dr. Inna K. Shundrina Dr. Elena V. Zaytseva Dr. Dmitriy A. Parkhomenko Prof. Dr. Elena G. Bagryanskaya Prof. Dr. Victor I. Ovcharenko 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20885-20891
Thermally stable organic diradicals with a triplet ground state along with large singlet-triplet energy gap have significant potential for advanced technological applications. A series of phenylene-bridged diradicals with oxoverdazyl and nitronyl nitroxide units were synthesized via a palladium-catalyzed cross-coupling reaction of iodoverdazyls with a nitronyl nitroxide-2-ide gold(I) complex with high yields. The diradicals exhibit high stability and do not decompose in an inert atmosphere up to 180 °C. For the diradicals, both substantial AF (ΔEST≈−64 cm−1) and FM (ΔEST≥25 and 100 cm−1) intramolecular exchange interactions were observed. The sign of the exchange interaction is determined both by the bridging moiety (para- or meta-phenylene) and by the type of oxoverdazyl block (C-linked or N-linked). Upon crystallization, diradicals with the triplet ground state form unique one-dimensional exchange-coupled chains with strong intra- and weak inter-diradical ferromagnetic coupling. 相似文献
72.
Pharmaceuticals require careful and precise determination of their impurities that might harm the user upon consumption. Although today, the most common technique for impurities identification is liquid chromatography‐mass spectrometry (LC‐MS/MS), it has several downsides due to the nature of the ionization method. Also, the analyses in many cases are targeted thus despite being present, some of the compounds will not be revealed. In this paper, we propose and show a new method for untargeted analysis and identification of impurities in active pharmaceutical ingredients (APIs). The instrument used for these analyses is a novel electron ionization (EI) LC‐MS with supersonic molecular beams (SMB). The EI‐LC‐MS‐SMB was implemented for analyses of several drug samples spiked with an impurity. The instrument provides EI mass spectra with enhanced molecular ions, named Cold EI, which increases the identification probabilities when the compound is identified with the aid of an EI library like National Institute of Standards and Technology (NIST). We analyzed ibuprofen and its impurities, and both the API and the expected impurity were identified with names and structures by the NIST library. Moreover, other unexpected impurities were found and identified proving the ability of the EI‐LC‐MS‐SMB system for truly untargeted analysis. The results show a broad dynamic range of four orders of magnitude at the same run with a signal‐to‐noise ratio of over 10 000 for the API and almost uniform response. 相似文献
73.
Rostislav A. Andrievski Svetlana V. Klyuchareva 《Journal of nanoparticle research》2011,13(12):6221-6230
The nanotechnology development is accompanied by an intensive growth of information flow which is specially noticeable as
applied to journal information flow. Now over the world there are the 69 nano-titled journals with the impact factor and/or
a settled periodicity as well as the 70 those which lack stability periodicity and are in an organization stage. Only 49 nano-titled
have the impact factor with the comparatively high mean value of about 3.44. The domestic nano-titled journals published in
Russia, India, China, and other countries are also considered. The attention is taken that in the 2006–2010 period the 95
new nano-titled journals were organized and in 2011 this process is continuing and seems to be the most impressive. Many nano-related
journals (including classical physical, chemical and materials science ones) are also described and discussed. 相似文献
74.
Konstantin Pankrashkin Svetlana Roganova Nader Yeganefar 《Integral Equations and Operator Theory》2011,71(2):199-223
We study Laplace-type operators on hybrid manifolds, i.e., on configurations consisting of closed two-dimensional manifolds
and one-dimensional segments. Such an operator can be constructed by using the Laplace–Beltrami operators on each component
with some boundary conditions at the points of gluing. The large spectral parameter expansion of the trace of the second power
of the resolvent is obtained. Some questions of the inverse spectral theory are addressed. 相似文献
75.
76.
Yury Yu. Rusakov Leonid B. Krivdin Maxim V. Penzik Vladimir A. Potapov Svetlana V. Amosova 《Magnetic resonance in chemistry : MRC》2012,50(10):653-658
Stereochemical structure of nine Z‐2‐(vinylsulfanyl)ethenylselanyl organyl sulfides has been investigated by means of experimental measurements and second‐order polarization propagator approach calculations of their 1H–1H, 13C–1H, and 77Se–1H spin–spin coupling constants together with a theoretical conformational analysis performed at the MP2/6‐311G** level. All nine compounds were shown to adopt the preferable skewed s‐cis conformation of their terminal vinylsulfanyl group, whereas the favorable rotational conformations with respect to the internal rotations around the C–S and C–Se bonds of the internal ethenyl group are both skewed s‐trans. Stereochemical trends of 77Se–1H spin–spin coupling constants originating in the geometry of their coupling pathways and the selenium lone pair effect were rationalized in terms of the natural J‐coupling analysis within the framework of the natural bond orbital approach. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
77.
Bennink RS Wong V Marino AM Aronstein DL Boyd RW Stroud CR Lukishova S Gauthier DJ 《Physical review letters》2002,88(11):113901
We have observed transverse pattern formation leading to highly regular structures in both the near and far fields when a near-resonant laser beam propagates without feedback through an atomic sodium vapor. One example is a regular far-field honeycomb pattern, which results from the transformation of the laser beam within the vapor into a stable three-lobed structure with a uniform phase distribution and highly correlated power fluctuations. The predictions of a theoretical model of the filamentation process are in good agreement with these observations. 相似文献
78.
Solid-Phase Luminescence Determination of Ciprofloxacin and Norfloxacin in Biological Fluids 总被引:1,自引:0,他引:1
Svetlana Beltyukova Olga Teslyuk Alla Egorova Elena Tselik 《Journal of fluorescence》2002,12(2):269-272
A simple, rapid, and sensitive luminescence test method for the determination of ciprofloxacin (CIP) and norfloxacin (NOR) has been described. The method is based on the intramolecular energy transfer from organic acid to terbium (Tb3+) ion. Luminescence of terbium (III) complex with CIP (NOR), sorbed on the zeolite has been studied. Under optimized conditions the detection limit is 1 g/mL in urine and human plasma. 相似文献
79.
Narcis Ghisovan Abdellatif Nemri Svetlana Shumikhina Stephane Molotchnikoff 《BMC neuroscience》2008,9(1):60
Background
Visual neurons respond essentially to luminance variations occurring within their receptive fields. In primary visual cortex, each neuron is a filter for stimulus features such as orientation, motion direction and velocity, with the appropriate combination of features eliciting maximal firing rate. Temporal correlation of spike trains was proposed as a potential code for linking the neuronal responses evoked by various features of a same object. In the present study, synchrony strength was measured between cells following an adaptation protocol (prolonged exposure to a non-preferred stimulus) which induce plasticity of neurons' orientation preference. 相似文献80.
We derive for Hecke-Maass cusp forms on the full modular group a relation between the sum of the form at Heegner points (and
integrals over Heegner cycles) and the product of two Fourier coefficients of a corresponding form of half-integral weight.
Specializing to certain cycles we obtain the nonnegativity of theL-function of such a form at the center of the critical strip. These results generalize similar formulae known for holomorphic
forms.
Partially supported by NSF grant # DMS-9096262.
Partially supported by NSF grant # DMS-9102082. 相似文献