全文获取类型
收费全文 | 273357篇 |
免费 | 2921篇 |
国内免费 | 979篇 |
专业分类
化学 | 145903篇 |
晶体学 | 4215篇 |
力学 | 12211篇 |
综合类 | 49篇 |
数学 | 30289篇 |
物理学 | 84590篇 |
出版年
2020年 | 2318篇 |
2019年 | 2495篇 |
2018年 | 3281篇 |
2017年 | 3269篇 |
2016年 | 4736篇 |
2015年 | 2927篇 |
2014年 | 4540篇 |
2013年 | 11097篇 |
2012年 | 8493篇 |
2011年 | 10378篇 |
2010年 | 7395篇 |
2009年 | 7169篇 |
2008年 | 9671篇 |
2007年 | 9849篇 |
2006年 | 9171篇 |
2005年 | 8332篇 |
2004年 | 7639篇 |
2003年 | 6906篇 |
2002年 | 6810篇 |
2001年 | 7438篇 |
2000年 | 5736篇 |
1999年 | 4441篇 |
1998年 | 3912篇 |
1997年 | 3893篇 |
1996年 | 3641篇 |
1995年 | 3374篇 |
1994年 | 3541篇 |
1993年 | 3232篇 |
1992年 | 3706篇 |
1991年 | 3698篇 |
1990年 | 3635篇 |
1989年 | 3481篇 |
1988年 | 3584篇 |
1987年 | 3483篇 |
1986年 | 3298篇 |
1985年 | 4389篇 |
1984年 | 4657篇 |
1983年 | 3884篇 |
1982年 | 4027篇 |
1981年 | 3943篇 |
1980年 | 3918篇 |
1979年 | 3905篇 |
1978年 | 4211篇 |
1977年 | 4121篇 |
1976年 | 4187篇 |
1975年 | 3858篇 |
1974年 | 3905篇 |
1973年 | 4056篇 |
1972年 | 2859篇 |
1971年 | 2380篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Kuz’mina L. G. Navasardyan M. A. Kalle P. Bezzubov S. I. 《Crystallography Reports》2021,66(3):420-423
Crystallography Reports - The crystal and molecular structures of Cl–C6H4–O–C16H33 (I) have been studied, and its differential scanning calorimetry (DSC) study is performed.... 相似文献
22.
We investigate the possibility of phantom crossing in the dark energy sector and the solution for the Hubble tension between early and late universe observations. We use robust combinations of different cosmological observations, namely the Cosmic Microwave Background (CMB), local measurement of Hubble constant (), Baryon Acoustic Oscillation (BAO) and SnIa for this purpose. For a combination of CMB+BAO data that is related to early universe physics, phantom crossing in the dark energy sector was confirmed at a 95% confidence level and we obtained the constraint km/s/Mpc at a 68% confidence level, which is in perfect agreement with the local measurement by Riess et al. We show that constraints from different combinations of data are consistent with each other and all of them are consistent with phantom crossing in the dark energy sector. For the combination of all data considered, we obtained the constraint km/s/Mpc at a 68% confidence level and the phantom crossing happening at the scale factor at a 68% confidence level. 相似文献
23.
24.
25.
Dr. Ruijuan Yao Prof. Di Liu Dr. Huihui Wan Dr. Yongqiang Mei Jiahui Wang Dr. Rui Cai Dr. Huimin Zhang Dr. Yuzhen Zhao Dr. Zemin He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(71):e202202269
By linking the carbazole unit to the nitrogen atom of acridone through phenyl or pyridyl, two compounds, named 10-(4-(9H-carbazol-9-yl)phenyl)acridin-9(10H)-one (AC-Ph-Cz) and 10-(5-(9H-carbazol-9-yl)pyridin-2-yl)acridin-9(10H)-one (AC-Py-Cz) were designed and synthesized. These two materials, characterized with highly twisted and rigid structure, good thermal stability, and balanced carrier-transporting properties, were employed as host materials for green phosphorescent and thermally activated delayed fluorescent organic light-emitting diodes (OLEDs). The carbazole group, despite its small contribution to the highest occupied molecular orbitals (HOMOs) of these two materials, plays an essential role as an intramolecular host in energy delivering and improving the hole transporting ability of these two hosts. The incorporation of the electron-deficient pyridyl group as a linking group slightly improves the electron transporting capability of AC-Py-Cz. The green phosphorescent OLED (PhOLED) based on AC-Py-Cz exhibited excellent device performance with a turn-on voltage of 2.5 V, a maximum power efficiency and an external quantum efficiency (ηext) of 89.8 lm W−1 and 25.2 %, respectively, benefitting from the better charge-balancing ability of AC-Py-Cz host due to the presence of the pyridyl bridge. More importantly, all the devices based on these two hosts showed low efficiency roll-off at high brightness due to the suppressed non-radiative transition in the emitting layer. In particular, the AC-Py-Cz-hosted green PhOLED exhibited an efficiency roll-off of 1.6 % from the maximum next at a high brightness of 1000 cd m−2 and a roll-off of 15.9 % at an extremely high brightness of 10000 cd m−2. This study manifests that acridone-based host materials have great potential in fabricating OLEDs with low efficiency roll-off. 相似文献
26.
27.
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
28.
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
29.
Dzhun I. O. Babaitsev G. V. Kozin M. G. Romashkina I. L. Shanova E. I. Chechenin N. G. 《Physics of the Solid State》2021,63(6):825-831
Physics of the Solid State - The external factors which influence the ferromagnetic resonance (FMR) line width in bilayer (ferromagnet/antiferromagnet) exchange-biased systems are studied. The... 相似文献
30.
Chueshova A. G. Pavlova L. A. Peshcherova S. M. Nepomnyashchikh A. I. 《Crystallography Reports》2021,66(7):1206-1215
Crystallography Reports - The orientation of grains and the special boundaries formed by them in multicrystalline silicon has been studied by electron backscattered diffraction. It is found that... 相似文献