全文获取类型
收费全文 | 890276篇 |
免费 | 8472篇 |
国内免费 | 2733篇 |
专业分类
化学 | 385054篇 |
晶体学 | 11294篇 |
力学 | 42215篇 |
综合类 | 20篇 |
数学 | 125479篇 |
物理学 | 235990篇 |
无线电 | 101429篇 |
出版年
2021年 | 7176篇 |
2020年 | 7813篇 |
2019年 | 8812篇 |
2018年 | 22212篇 |
2017年 | 21923篇 |
2016年 | 22613篇 |
2015年 | 9814篇 |
2014年 | 15628篇 |
2013年 | 35502篇 |
2012年 | 30451篇 |
2011年 | 42260篇 |
2010年 | 30376篇 |
2009年 | 31482篇 |
2008年 | 38206篇 |
2007年 | 40856篇 |
2006年 | 30070篇 |
2005年 | 28324篇 |
2004年 | 26692篇 |
2003年 | 24728篇 |
2002年 | 23456篇 |
2001年 | 24609篇 |
2000年 | 19712篇 |
1999年 | 15716篇 |
1998年 | 13848篇 |
1997年 | 13440篇 |
1996年 | 12560篇 |
1995年 | 11316篇 |
1994年 | 11266篇 |
1993年 | 10887篇 |
1992年 | 11378篇 |
1991年 | 11832篇 |
1990年 | 11223篇 |
1989年 | 10864篇 |
1988年 | 10282篇 |
1987年 | 9585篇 |
1986年 | 9082篇 |
1985年 | 11399篇 |
1984年 | 11757篇 |
1983年 | 9874篇 |
1982年 | 9997篇 |
1981年 | 9429篇 |
1980年 | 9062篇 |
1979年 | 9601篇 |
1978年 | 9804篇 |
1977年 | 9611篇 |
1976年 | 9484篇 |
1975年 | 9115篇 |
1974年 | 8928篇 |
1973年 | 9243篇 |
1972年 | 6624篇 |
排序方式: 共有10000条查询结果,搜索用时 475 毫秒
91.
Smirnova T. D. Zhelobitskaya E. A. Danilina T. G. 《Journal of Analytical Chemistry》2022,77(8):1000-1004
Journal of Analytical Chemistry - Silver nanoparticles modified with Eu3+ ions increase the intensity of the fluorescence signal by a factor of 125 in an analytical system containing doxycycline as... 相似文献
92.
Computational Optimization and Applications - We consider a continuous-time optimization method based on a dynamical system, where a massive particle starting at rest moves in the conservative... 相似文献
93.
The health monitoring has been studied to ensure integrity of design of engine structure by detection, quantification, and prediction of damages. Early detection of faults may allow the downtime of maintenance to be rescheduled, thus preventing sudden shutdown of machines. In cylinder pressure developed, vibrations and noise emissions data provide a rich source of information about condition of engines. Monitoring of vibrations and noise emissions are novel non-intrusive methodologies for which positioning of various transducers are important issue. The presented work shows applicability of these diagnosis methodologies adopted in case of diesel engines. The effects of changing various fuel injection parameters was analyzed. Scope of using non-intrusive technique has been analyzed by changing locations of microphone. Novelty of this worklies in exploring signal processing methods for various locations around the engine test set up. Various frequency ranges of contributing noise and vibration sources were identified. Time-Frequency analysis showed the onset of various cyclic. Based on the identification of various frequency bands, it is possible to device suitable filters in order to extract more information. 相似文献
94.
Daulbaev O. Isaenko L. I. Bogdzel’ A. A. Lobanov S. I. Krinitsyn P. G. Milkov V. M. Belushkin A. V. 《Crystallography Reports》2022,67(3):464-469
Crystallography Reports - Two LiInSe2 single crystals, grown under different conditions, have been studied. Characteristics of these crystals for neutron detection have been compared using... 相似文献
95.
Liangtao Yang Liang-Yin Kuo Juan Miguel López del Amo Prasant Kumar Nayak Katherine A. Mazzio Sebastian Maletti Daria Mikhailova Lars Giebeler Payam Kaghazchi Teófilo Rojo Philipp Adelhelm 《Advanced functional materials》2021,31(38):2102939
A known strategy for improving the properties of layered oxide electrodes in sodium-ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2-Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid-state NMR, operando XRD, and density functional theory (DFT). For the as-synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid-solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g-1 after 100 cycles. In contrast, the Li-free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair-case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2-/O2-δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded. 相似文献
96.
Ibotov Sh. Kh. Yuldasheva N. K. Mukarramov N. I. Zakirova R. P. Gusakova S. D. 《Chemistry of Natural Compounds》2022,58(4):728-731
Chemistry of Natural Compounds - 相似文献
97.
Svetlakova A. V. Mendez M. Sanchez Tuchin E. S. Khodan A. N. Traore M. Azouani R. Kanaev A. Tuchin V. V. 《Optics and Spectroscopy》2021,129(8):846-850
Optics and Spectroscopy - We study the photocatalytic activity of nanocomposites based on θ-phase alumina (Al2O3) with different TiO2 concentrations for heterogeneous photocatalysis and... 相似文献
98.
Revin A. A. Mikhaylova A. M. Konakov A. A. Tsyplenkov V. V. Shastin V. N. 《Semiconductors》2021,55(12):879-884
Semiconductors - The wave functions of electrons localized at P, As, and Sb shallow donors in Ge are calculated in the envelope function approximation taking into account valley–orbit... 相似文献
99.
Kolesnikov A. O. Shatokhin A. N. Vishnyakov E. A. Ragozin E. N. 《Journal of Russian Laser Research》2022,43(4):467-475
Journal of Russian Laser Research - We analyze the way of advancing to tender X-rays the short-wavelength bound of the operating range of flat-field grating spectrographs. We design two VLS grating... 相似文献
100.
Journal of Structural Chemistry - Structural parameters and relative Gibbs free energies are calculated by density functional theory methods for four tetrafluoro derivatives of zinc(II)... 相似文献