全文获取类型
收费全文 | 9728篇 |
免费 | 1981篇 |
国内免费 | 1208篇 |
专业分类
化学 | 7069篇 |
晶体学 | 201篇 |
力学 | 673篇 |
综合类 | 119篇 |
数学 | 936篇 |
物理学 | 3919篇 |
出版年
2024年 | 29篇 |
2023年 | 235篇 |
2022年 | 324篇 |
2021年 | 416篇 |
2020年 | 559篇 |
2019年 | 495篇 |
2018年 | 421篇 |
2017年 | 396篇 |
2016年 | 610篇 |
2015年 | 617篇 |
2014年 | 674篇 |
2013年 | 855篇 |
2012年 | 1000篇 |
2011年 | 1018篇 |
2010年 | 688篇 |
2009年 | 560篇 |
2008年 | 586篇 |
2007年 | 545篇 |
2006年 | 442篇 |
2005年 | 390篇 |
2004年 | 304篇 |
2003年 | 263篇 |
2002年 | 242篇 |
2001年 | 187篇 |
2000年 | 123篇 |
1999年 | 110篇 |
1998年 | 96篇 |
1997年 | 86篇 |
1996年 | 74篇 |
1995年 | 40篇 |
1994年 | 49篇 |
1993年 | 54篇 |
1992年 | 54篇 |
1991年 | 41篇 |
1990年 | 44篇 |
1989年 | 28篇 |
1988年 | 29篇 |
1987年 | 17篇 |
1986年 | 29篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 25篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1974年 | 9篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
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
12.
Nonlinear Dynamics - This paper seeks to address the problem of finite-time stabilization for a class of uncertain Hamiltonian systems via sliding mode control approach. A novel sliding function in... 相似文献
13.
14.
Cuixia Cui Yong Gao Dr. Jun Li Chao Yang Meng Liu Prof. Dr. Huile Jin Prof. Dr. Zhenhai Xia Prof. Dr. Liming Dai Prof. Dr. Yong Lei Prof. Dr. Jichang Wang Prof. Dr. Shun Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(20):8002-8007
Although tremendous efforts have been devoted to understanding the origin of boosted charge storage on heteroatom-doped carbons, none of the present studies has shown a whole landscape. Herein, by both experimental evidence and theoretical simulation, it is demonstrated that heteroatom doping not only results in a broadened operating voltage, but also successfully promotes the specific capacitance in aqueous supercapacitors. In particular, the electrolyte cations adsorbed on heteroatom-doped carbon can effectively inhibit hydrogen evolution reaction, a key step of water decomposition during the charging process, which broadens the voltage window of aqueous electrolytes even beyond the thermodynamic limit of water (1.23 V). Furthermore, the reduced adsorption energy of heteroatom-doped carbon consequently leads to more stored cations on the heteroatom-doped carbon surface, thus yielding a boosted charge storage performance. 相似文献
15.
It is believed that there are more fundamental gauge symmetries beyond those described by the Standard Model of particle physics. The scales of these new gauge symmetries are usually too high to be reachable by particle colliders. Considering that the phase transition (PT) relating to the spontaneous breaking of new gauge symmetries to the electroweak symmetry might be strongly first order, we propose considering the stochastic gravitational waves (GW) arising from this phase transition as an indirect way of detecting these new fundamental gauge symmetries. As an illustration, we explore the possibility of detecting the stochastic GW generated from the PT of \begin{document}$ {\bf{B}}-{\bf{L}}$\end{document} ![]()
![]()
in the space-based interferometer detectors. Our study demonstrates that the GW energy spectrum is reachable by the LISA, Tianqin, Taiji, BBO, and DECIGO experiments only for the case where the spontaneous breaking of \begin{document}$ {\bf{B}}-{\bf{L}}$\end{document} ![]()
![]()
is triggered by at least two electroweak singlet scalars. 相似文献
16.
Studies on metabolism of total glucosides of paeony from Paeoniae Radix Alba in rats by UPLC‐Q‐TOF‐MS/MS 下载免费PDF全文
Wenli Cao Xinguo Wang Haojie Li Xuliang Shi Wencheng Fan Shaohua Zhao Minyan Liu Liying Niu 《Biomedical chromatography : BMC》2015,29(11):1769-1779
Total glucosides of paeony are the active constituents of Paeoniae Radix Alba. In this study, a novel strategy was proposed to find more metabolites and the differences between paeoniflorin, albiflorin and total glucosides of paeony (TGP). This strategy was characterized as follows: firstly, the animals were divided into three groups (paeoniflorin, albiflorin and TGP) to identify the source of TGP metabolites from paeoniflorin or albiflorin; secondly, a generic information‐dependent acquisition scan for the low‐level metabolites was triggered by the multiple mass defect filter and dynamic background subtraction; thirdly, the metabolites were identified with a combination of data‐processing methods including mass defect filtering, neutral loss filtering and product ion filtering; finally, a comparative study was used in the metabolism of paeoniflorin, albiflorin and TGP. Based on the strategy, 18 metabolites of TGP, 10 metabolites of paeoniflorin and 13 metabolites of albiflorin were identified respectively. The results indicated that the hydrolysis, conjugation reaction and oxidization were the major metabolic pathways, and the metabolic sites were the glycosidic linkage, the ester bond and the benzene ring. This study is first to explore the metabolism of TGP, and these findings enhance our understanding of the metabolism and the interactions of paeoniflrin and albiflorin in TGP. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
17.
Nonlinear Dynamics - Nonlinear vibration isolation provides with an effective way for vibration reduction with broad band and high efficiency. This investigation focuses on the dynamic effects of a... 相似文献
18.
本文证明了Heisenberg群上Laplace算子的Dirichlet特征值的存在性,给出了特征值的估计 相似文献
19.
以CF4和C6H6的混合气体作为气源,在微波电子回旋共振化学气相沉积(ECRCVD)装置中制备了氟化非晶碳薄膜(aC:F),并在N2气氛中作了退火处理以考察其热稳定性.通过傅里叶变换红外吸收谱和紫外可见光谱获得了薄膜中CC双键的相对含量和光学带隙,发现膜中CC键含量与光学带隙之间存在着密切的关联,在高微波功率下沉积的氟化非晶碳膜具有低的光学带隙和较好的热稳定性.
关键词:
氟化非晶碳膜
光学带隙
退火温度
热稳定性 相似文献
20.