全文获取类型
收费全文 | 124392篇 |
免费 | 29779篇 |
国内免费 | 22211篇 |
专业分类
化学 | 82938篇 |
晶体学 | 1526篇 |
力学 | 7809篇 |
综合类 | 405篇 |
数学 | 15588篇 |
物理学 | 68116篇 |
出版年
2024年 | 520篇 |
2023年 | 1616篇 |
2022年 | 2012篇 |
2021年 | 2232篇 |
2020年 | 2663篇 |
2019年 | 3150篇 |
2018年 | 2929篇 |
2017年 | 3385篇 |
2016年 | 4304篇 |
2015年 | 4469篇 |
2014年 | 4744篇 |
2013年 | 7385篇 |
2012年 | 8415篇 |
2011年 | 10046篇 |
2010年 | 12119篇 |
2009年 | 12219篇 |
2008年 | 6490篇 |
2007年 | 5731篇 |
2006年 | 5160篇 |
2005年 | 5192篇 |
2004年 | 5428篇 |
2003年 | 4382篇 |
2002年 | 4157篇 |
2001年 | 4221篇 |
2000年 | 3325篇 |
1999年 | 3610篇 |
1998年 | 3026篇 |
1997年 | 2770篇 |
1996年 | 3106篇 |
1995年 | 3389篇 |
1994年 | 3386篇 |
1993年 | 3343篇 |
1992年 | 2907篇 |
1991年 | 2484篇 |
1990年 | 2135篇 |
1989年 | 2151篇 |
1988年 | 2072篇 |
1987年 | 1313篇 |
1986年 | 1395篇 |
1985年 | 1080篇 |
1984年 | 1102篇 |
1982年 | 987篇 |
1981年 | 802篇 |
1980年 | 833篇 |
1979年 | 587篇 |
1978年 | 570篇 |
1977年 | 669篇 |
1976年 | 1080篇 |
1973年 | 481篇 |
1972年 | 551篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
35.
A self-propelled object coupled with an enzyme reaction between urease and urea was investigated at the air/aqueous interface. A plastic object that was fixed to a urease-immobilized filter paper was used as a self-propelled object, termed a urease motor, placed on an aqueous urea solution. The driving force of the urease motor is the difference in the surface tension around the object. Oscillatory motion or no motion was triggered depending on the initial pH of the urea solution. Both the frequency and maximum speed of the oscillatory motion varied depending on the initial pH of the water phase. The mechanisms underlying the oscillatory motion and no motion were discussed in relation to the bell-shaped enzyme activity of urease in the enzyme reaction and the surface tension around the urease motor. 相似文献
36.
Hui Li Jian Liu Juan Zhao Huiting He Dr. Dabo Jiang Prof. Steven Robert Kirk Prof. Qiong Xu Dr. Xianxiang Liu Prof. Dulin Yin 《ChemistryOpen》2021,10(4):477-485
A series of tetraimidazolium salts with different anions was prepared and applied in the isomerization of β-pinene oxide. After examining the activity of different catalysts, a remarkable enhancement of the selectivity of perillyl alcohol (47 %) was obtained over [PEimi][HNO3]4 under mild reaction conditions and using DMSO as the solvent. Furthermore, noncovalent interactions between solvent molecules and the catalyst were found by FT-IR spectroscopy and confirmed by computational chemistry. The homogeneous catalyst showed excellent stability and was reused up to six times without significant loss. 相似文献
37.
Zhang Jia-Rui Zhang Jia-Qi Zheng Zhao-Lin Lin Da Shen Yu-Jia 《Nonlinear dynamics》2022,108(2):1005-1026
Nonlinear Dynamics - Parametrically excited oscillators are used in several domains, in particular to improve the dynamical behaviour of systems like in the case of the parametric amplification or... 相似文献
38.
39.
Dr. Wan‐Ling Liu Ni‐Shin Yang Ya‐Ting Chen Stephen Lirio Cheng‐You Wu Prof. Chia‐Her Lin Prof. Hsi‐Ya Huang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):115-119
A green and sustainable strategy synthesizes clinical medicine warfarin anticoagulant by using lipase‐supported metal–organic framework (MOF) bioreactors (see scheme). These findings may be beneficial for future studies in the industrial production of chemical, pharmaceutical, and agrochemical precursors. 相似文献
40.
Chao Liu Liying Wang Lin Yang Famei Wang Chunhong Xu Jingwei Lv Guanglai Fu Xianli Li Qiang Liu Haiwei Mu Tao Sun Paul K. Chu 《Physics letters. A》2019,383(25):3200-3206
A single-polarization filter comprising a gold-coated photonic crystal fiber based on surface plasmon resonance is designed and investigated. The pattern matching and coupled polarization characteristics analyzed by the full-vector finite element method (FEM) and losses at 1,540 nm are achieved to 1,016.01739 dB/cm (x-pol core mode) and 33.81917 dB/cm (y-pol core mode). The crosstalk (CT) value of the 1,540 nm band is ?853.12653 dB for fiber length and the bandwidth is 850 nm. The working wavelength of the filter ranges from 1,280 nm to 1,540 nm by varying the diameter of outer air holes (), the diameter of inner air holes (), the metal film thickness (t), as well as the liquid refractive index (n). 相似文献