全文获取类型
收费全文 | 2789篇 |
免费 | 45篇 |
国内免费 | 33篇 |
专业分类
化学 | 1538篇 |
晶体学 | 56篇 |
力学 | 67篇 |
数学 | 630篇 |
物理学 | 576篇 |
出版年
2022年 | 10篇 |
2021年 | 39篇 |
2020年 | 30篇 |
2019年 | 35篇 |
2018年 | 38篇 |
2017年 | 56篇 |
2016年 | 77篇 |
2015年 | 71篇 |
2014年 | 83篇 |
2013年 | 206篇 |
2012年 | 129篇 |
2011年 | 171篇 |
2010年 | 109篇 |
2009年 | 114篇 |
2008年 | 162篇 |
2007年 | 152篇 |
2006年 | 145篇 |
2005年 | 118篇 |
2004年 | 133篇 |
2003年 | 92篇 |
2002年 | 94篇 |
2001年 | 41篇 |
2000年 | 28篇 |
1999年 | 36篇 |
1998年 | 29篇 |
1997年 | 36篇 |
1996年 | 46篇 |
1995年 | 22篇 |
1994年 | 28篇 |
1993年 | 36篇 |
1992年 | 25篇 |
1991年 | 25篇 |
1990年 | 31篇 |
1989年 | 30篇 |
1988年 | 19篇 |
1987年 | 25篇 |
1986年 | 18篇 |
1985年 | 29篇 |
1984年 | 40篇 |
1983年 | 23篇 |
1982年 | 23篇 |
1981年 | 28篇 |
1980年 | 21篇 |
1979年 | 21篇 |
1978年 | 20篇 |
1977年 | 29篇 |
1976年 | 12篇 |
1975年 | 12篇 |
1974年 | 10篇 |
1972年 | 11篇 |
排序方式: 共有2867条查询结果,搜索用时 15 毫秒
1.
Mnich Konrad Lazarek Mateusz Stefanski Andrzej Perlikowski Przemyslaw 《Meccanica》2022,57(8):1955-1973
Meccanica - This paper presents the experimental identification of the friction force in the inerter with constant and variable inertance. The change of intertance is possible due to the... 相似文献
2.
Gürbüzbalaban Mert Ruszczyński Andrzej Zhu Landi 《Journal of Optimization Theory and Applications》2022,194(3):1014-1041
Journal of Optimization Theory and Applications - We consider a distributionally robust formulation of stochastic optimization problems arising in statistical learning, where robustness is with... 相似文献
3.
Warminski Jerzy Kloda Lukasz Latalski Jaroslaw Mitura Andrzej Kowalczuk Marcin 《Nonlinear dynamics》2021,105(4):3255-3270
Nonlinear Dynamics - This paper investigates the time-varying formation tracking (TVFT) problem of multiple heterogeneous Euler–Lagrange agents (MHELAs) with predefined-time convergence... 相似文献
4.
Dr. Olaf Morawski Dr. Paweł Gawryś Dr. Jarosław Sadło Prof. Andrzej L. Sobolewski 《Chemphyschem》2022,23(11):e202200077
When irradiated with violet light, hexaazatrinaphthylene (HATN) extracts a hydrogen atom from an alcohol forming a long-living hydrogenated species. The apparent kinetic isotope effect for fluorescence decay time in deuterated methanol (1.56) indicates that the lowest singlet excited state of the molecule is a precursor for intermolecular hydrogen transfer. The photochemical hydrogenation occurs in several alcohols (methanol, ethanol, isopropanol) but not in water. Hydrogenated HATN can be detected optically by an absorption band at 1.78 eV as well as with EPR (electron paramagnetic resonance) and NMR techniques. Mass spectrometry of photoproducts reveal di-hydrogenated HATN structures along with methoxylated and methylated HATN molecules which are generated through the reaction with methoxy radicals (remnants from alcohol splitting). Experimental findings are consistent with the theoretical results which predicted that for the excited state of the HATN-solvent molecular complex, there exists a barrierless hydrogen transfer from methanol but a small barrier for the similar oxidation of water. 相似文献
5.
Alina T. Dubis Piotr Stasiewicz Katarzyna Pogorzelec‐Glaser Andrzej Łapiński 《Journal of Physical Organic Chemistry》2015,28(10):652-662
The formation of intramolecular hydrogen bonding by certain N‐substituted 2‐acylpyrroles has been demonstrated by B3LYP/aug‐cc‐pVDZ calculations, the quantum theory of atoms in molecules, and the natural bond orbital method. Total electron energy densities HBCP at the bond critical point of the H?O bond were applied to analyze the strength of these interactions. The relations between quantum theory of atoms in molecules, carbonyl stretching vibrational modes νC = O, and natural bond orbital parameters associated with the formation of the C–H?O interaction have been established. The short contacts were found experimentally in the crystal structure of a new 2‐acylpyrrole derivative 5‐chloro‐2‐oxopentyl‐1‐(5‐chloro‐2‐oxopentyl)pyrrolo‐2‐carboxylate. The influence of 2‐ and N‐substitution of 2‐acylpyrroles on C‐H?O interaction energy is discussed. It was found that the methylene group may act as a proton donor leading to a red‐shift or blue‐shift phenomenon of the νC–H stretching mode. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
6.
7.
8.
9.
In situ X‐ray data collection and structure phasing of protein crystals at Structural Biology Center 19‐ID 下载免费PDF全文
Karolina Michalska Kemin Tan Changsoo Chang Hui Li Catherine Hatzos‐Skintges Michael Molitsky Randy Alkire Andrzej Joachimiak 《Journal of synchrotron radiation》2015,22(6):1386-1395
A prototype of a 96‐well plate scanner for in situ data collection has been developed at the Structural Biology Center (SBC) beamline 19‐ID, located at the Advanced Photon Source, USA. The applicability of this instrument for protein crystal diffraction screening and data collection at ambient temperature has been demonstrated. Several different protein crystals, including selenium‐labeled, were used for data collection and successful SAD phasing. Without the common procedure of crystal handling and subsequent cryo‐cooling for data collection at T = 100 K, crystals in a crystallization buffer show remarkably low mosaicity (<0.1°) until deterioration by radiation damage occurs. Data presented here show that cryo‐cooling can cause some unexpected structural changes. Based on the results of this study, the integration of the plate scanner into the 19‐ID end‐station with automated controls is being prepared. With improvement of hardware and software, in situ data collection will become available for the SBC user program including remote access. 相似文献
10.
Dr. Luca Fornasari Dr. Anna Olejniczak Dr. Federica Rossi Dr. Simone d'Agostino Prof. Michele R. Chierotti Prof. Roberto Gobetto Prof. Andrzej Katrusiak Prof. Dario Braga 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(22):5061-5069
The structures and solid-state dynamics of the supramolecular salts of the general formula [(12-crown-4)2 ⋅ DABCOH2](X)2 (where DABCO=1,4-diazabicyclo[2.2.2]octane, X=BF4, ClO4) have been investigated as a function of temperature (from 100 to 360 K) and pressure (up to 3.4 GPa), through the combination of variable-temperature and variable-pressure XRD techniques and variable-temperature solid-state NMR spectroscopy. The two salts are isomorphous and crystallize in the enantiomeric space groups P3221 and P3121. All building blocks composing the supramolecular complex display dynamic processes at ambient temperature and pressure. It has been demonstrated that the motion of the crown ethers is maintained on lowering the temperature (down to 100 K) or on increasing the pressure (up to 1.5 GPa) thanks to the correlation between neighboring molecules, which mesh and rotate in a concerted manner similar to spiral gears. Above 1.55 GPa, a collapse-type transition to a lower-symmetry ordered structure, not attainable at a temperature of 100 K, takes place, proving, thus, that the pressure acts as the means to couple and decouple the gears. The relationship between temperature and pressure effects on molecular motion in the solid state has also been discussed. 相似文献