全文获取类型
收费全文 | 5191篇 |
免费 | 983篇 |
国内免费 | 550篇 |
专业分类
化学 | 3596篇 |
晶体学 | 49篇 |
力学 | 199篇 |
综合类 | 72篇 |
数学 | 453篇 |
物理学 | 2355篇 |
出版年
2024年 | 14篇 |
2023年 | 118篇 |
2022年 | 155篇 |
2021年 | 170篇 |
2020年 | 197篇 |
2019年 | 191篇 |
2018年 | 177篇 |
2017年 | 143篇 |
2016年 | 249篇 |
2015年 | 252篇 |
2014年 | 255篇 |
2013年 | 339篇 |
2012年 | 495篇 |
2011年 | 559篇 |
2010年 | 336篇 |
2009年 | 340篇 |
2008年 | 360篇 |
2007年 | 304篇 |
2006年 | 270篇 |
2005年 | 215篇 |
2004年 | 184篇 |
2003年 | 123篇 |
2002年 | 151篇 |
2001年 | 112篇 |
2000年 | 118篇 |
1999年 | 109篇 |
1998年 | 94篇 |
1997年 | 112篇 |
1996年 | 86篇 |
1995年 | 79篇 |
1994年 | 63篇 |
1993年 | 73篇 |
1992年 | 43篇 |
1991年 | 64篇 |
1990年 | 42篇 |
1989年 | 35篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有6724条查询结果,搜索用时 15 毫秒
201.
This paper presents a new algorithm for the prediction of indoor suspension particle dispersion based on a v2-f model. In order to handle the near-wall turbulence anisotropy properly, which is significant in the dispersion of fine particles, the particle eddy diffusivity is calculated using different formulae among regions of the turbulent core and in the vicinity of walls. The new algorithm is validated by several cases performed in two ventilated rooms with various air distribution patterns. The simulation results reveal that v2-f nonlinear turbulence model combined with a particle convective equation gives satisfactory agreement with the experimental data. It is generally found that the dynamic equation combined with the v2-f model can properly handle low Reynolds number (LRN) flows which are usually encountered in indoor air flows and fine particle dispersion. 相似文献
202.
203.
204.
205.
206.
Optimizing Optoelectronic Properties of Pyrimidine‐Based TADF Emitters by Changing the Substituent for Organic Light‐Emitting Diodes with External Quantum Efficiency Close to 25 % and Slow Efficiency Roll‐Off
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kailong Wu Tao Zhang Lisi Zhan Dr. Cheng Zhong Prof. Shaolong Gong Prof. Nan Jiang Prof. Zheng‐Hong Lu Prof. Chuluo Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10860-10866
A series of green butterfly‐shaped thermally activated delayed fluorescence (TADF) emitters, namely PXZPM , PXZMePM , and PXZPhPM , are developed by integrating an electron‐donor (D) phenoxazine unit and electron‐acceptor (A) 2‐substituted pyrimidine moiety into one molecule via a phenyl‐bridge π linkage to form a D –π–A–π–D configuration. Changing the substituent at pyrimidine unit in these emitters can finely tune their emissive characteristics, thermal properties, and energy gaps between the singlet and triplet states while maintaining frontier molecular orbital levels, and thereby optimizing their optoelectronic properties. Employing these TADF emitters results in a green fluorescent organic light‐emitting diode (OLED) that exhibits a peak forward‐viewing external quantum efficiency (EQE) close to 25 % and a slow efficiency roll‐off characteristic at high luminance. 相似文献
207.
Yang?LiuEmail author Yanwei?Du Hong?Li Jinfeng?Wang 《Journal of Applied Mathematics and Computing》2015,47(1-2):103-117
In this article, an \(H^1\)-Galerkin mixed finite element (MFE) method for solving time fractional reaction–diffusion equation is presented. The optimal time convergence order \(O(\varDelta t^{2-\alpha })\) and the optimal spatial rate of convergence in \(H^1\) and \(L^2\)-norms for variable \(u\) and its gradient \(\sigma \) are derived. Moreover, some numerical results are shown to support our theoretical analysis. 相似文献
208.
209.
建立了硝酸提取,高效液相色谱一原子荧光联用技术测定方便面中不同砷形态的分析方法。样品经0.15mol/L盐酸溶液超声提取后离心过滤,上机测试。实验表明:砷的4种形态亚砷酸[As(Ⅲ)]、砷酸[As(V)]、一甲基胂酸(MMA)和二甲基胂酸(DMA)的线性范围为0-50μg/L,相关系数(r)均优于0.9990,检出限在2~8μg/L之间,砷各形态的测量重复性(以RSD表示)均小于5%,样品的加标回收率为78%-118%。同时用原子荧光光度计检测了样品中总砷,并将两种方法测定结果进行了对比,结果符合理论以及文献报道。该方法操作简单快速、结果准确可靠,适用于方便面中砷形态的分析测定。 相似文献
210.
Qing-Zhong Li Wen-Ming Liu Ran Li Wen-Zuo Li Jian-Bo Cheng Bao-An Gong 《Structural chemistry》2013,24(1):25-31
The H2O···XCCNgF and H3N···XCCNgF (X = Cl and Br; Ng = Ar, Kr, and Xe) complexes have been studied with quantum chemical calculations at the MP2/aug-cc-pVTZ level. The results show that the inserted noble gas atom has an enhancing effect on the strength of halogen bond, and this enhancement is weakened with the increase of noble gas atomic number. The methyl and Li substituents in the electron donor strengthen the halogen bond. The interaction energy increases from ?3.75 kcal/mol in H3N–BrCCF complex to ?9.66 kcal/mol in H2LiN–BrCCArF complex. These complexes have been analyzed with atoms in molecules, natural bond orbital, molecular electrostatic potentials, and energy decomposition calculations. 相似文献