全文获取类型
收费全文 | 436362篇 |
免费 | 5561篇 |
国内免费 | 1230篇 |
专业分类
化学 | 233822篇 |
晶体学 | 6494篇 |
力学 | 18842篇 |
综合类 | 13篇 |
数学 | 50682篇 |
物理学 | 133300篇 |
出版年
2021年 | 3764篇 |
2020年 | 4210篇 |
2019年 | 4556篇 |
2018年 | 5891篇 |
2017年 | 5798篇 |
2016年 | 8907篇 |
2015年 | 5632篇 |
2014年 | 8633篇 |
2013年 | 20369篇 |
2012年 | 15724篇 |
2011年 | 19350篇 |
2010年 | 13585篇 |
2009年 | 13429篇 |
2008年 | 17741篇 |
2007年 | 17609篇 |
2006年 | 16312篇 |
2005年 | 14586篇 |
2004年 | 13563篇 |
2003年 | 11933篇 |
2002年 | 11766篇 |
2001年 | 13442篇 |
2000年 | 10097篇 |
1999年 | 7933篇 |
1998年 | 6581篇 |
1997年 | 6325篇 |
1996年 | 6088篇 |
1995年 | 5474篇 |
1994年 | 5401篇 |
1993年 | 5201篇 |
1992年 | 5835篇 |
1991年 | 5928篇 |
1990年 | 5668篇 |
1989年 | 5476篇 |
1988年 | 5499篇 |
1987年 | 5380篇 |
1986年 | 5092篇 |
1985年 | 6569篇 |
1984年 | 6700篇 |
1983年 | 5307篇 |
1982年 | 5395篇 |
1981年 | 5371篇 |
1980年 | 4960篇 |
1979年 | 5363篇 |
1978年 | 5498篇 |
1977年 | 5395篇 |
1976年 | 5339篇 |
1975年 | 4918篇 |
1974年 | 4897篇 |
1973年 | 4887篇 |
1972年 | 3461篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Physics of Atomic Nuclei - Emission of short electron bunches with high charge in RF guns is considered. The emission mechanism in the case of picosecond laser pulses and the presence of a strong... 相似文献
32.
Li Y. Shi W. H. Dong L. M. Xu S. X. Huang H. J. Yin J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,... 相似文献
33.
Chemical bonding in representative astrophysically relevant neutral,cation, and anion HCnH chains
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)
Ioan Baldea 《中国物理 B》2022,31(12):123101-123101
Most existing studies assign a polyynic and cumulenic character of chemical bonding in carbon-based chains relying on values of the bond lengths. Building on our recent work, in this paper we add further evidence on the limitations of such an analysis and demonstrate the significant insight gained via natural bond analysis. Presently reported results include atomic charges, natural bond order and valence indices obtained from ab initio computations for representative members of the astrophysically relevant neutral and charged HC2k/2k+1H chain family. They unravel a series of counter-intuitive aspects and/or help naive intuition in properly understanding microscopic processes, e.g., electron removal from or electron attachment to a neutral chain. Demonstrating that the Wiberg indices adequately quantify the chemical bonding structure of the HC2k/2k+1H chains—while the often heavily advertised Mayer indices do not—represents an important message conveyed by the present study. 相似文献
34.
Designs, Codes and Cryptography - Given an integer $$k\ge 3$$ and a group G of odd order, if there exists a 2-(v, k, 1)-design and if v is sufficiently large then there... 相似文献
35.
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
36.
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
37.
Vasile M. Loots H. Vercammen L. Bruggeman M. Verrezen F. 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(8):3349-3357
Journal of Radioanalytical and Nuclear Chemistry - In this paper a study for the selection of an NPE (nonylphenol ethoxylates)—free cocktail is discussed in order to be used for our routine... 相似文献
38.
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
39.
Bucataru Ioan Constantinescu Oana Creţu Georgeta 《Annals of Global Analysis and Geometry》2022,62(4):815-827
Annals of Global Analysis and Geometry - We prove that in a Finsler manifold with vanishing $$\chi $$ -curvature (in particular with constant flag curvature) some non-Riemannian geometric... 相似文献
40.
Russian Chemical Bulletin - The N-methylation of primary carboxamides is based on two consecutive reactions. The silylation of the corresponding carboxamides with chloro(chloromethyl)dimethylsilane... 相似文献