全文获取类型
收费全文 | 1027篇 |
免费 | 136篇 |
国内免费 | 260篇 |
专业分类
化学 | 456篇 |
晶体学 | 13篇 |
力学 | 47篇 |
综合类 | 2篇 |
数学 | 84篇 |
物理学 | 164篇 |
无线电 | 657篇 |
出版年
2024年 | 13篇 |
2023年 | 71篇 |
2022年 | 97篇 |
2021年 | 93篇 |
2020年 | 72篇 |
2019年 | 68篇 |
2018年 | 46篇 |
2017年 | 59篇 |
2016年 | 44篇 |
2015年 | 45篇 |
2014年 | 48篇 |
2013年 | 57篇 |
2012年 | 54篇 |
2011年 | 74篇 |
2010年 | 83篇 |
2009年 | 85篇 |
2008年 | 54篇 |
2007年 | 58篇 |
2006年 | 70篇 |
2005年 | 38篇 |
2004年 | 39篇 |
2003年 | 20篇 |
2002年 | 22篇 |
2001年 | 8篇 |
2000年 | 17篇 |
1999年 | 19篇 |
1998年 | 26篇 |
1997年 | 9篇 |
1996年 | 16篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1979年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1423条查询结果,搜索用时 625 毫秒
181.
介绍了一种VA模式反射电极偏压的常黑单盒厚半反半透LCD.在透射区,形成连续且均匀的贯穿液晶层的电场;而在反射区,电场则主要由电极表面形状控制.由此,可使透射区的位相延迟约是反射区的2倍.这样一种半反半透LCD不论透射区还是反射区都有很高的光透过率(>90%),同时二者灰阶特性重合度也很好. 相似文献
182.
介绍了一种VA模式反射电极偏压的常黑单盒厚半反半透LCD。在透射区,形成连续且均匀的贯穿液晶层的电场;而在反射区,电场则主要由电极表面形状控制。由此,可使透射区的位相延迟约是反射区的2倍。这样一种半反半透LCD不论透射区还是反射区都有很高的光透过率(>90%),同时二者灰阶特性重合度也很好。 相似文献
183.
Jianyou Mao Zhiting Wang Xinyu Xu Guoqing Liu Runsheng Jiang Haixing Guan Zhipeng Zheng Patrick J. Walsh 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(32):11149-11154
Indoles are essential heterocycles in medicinal chemistry, and therefore, novel and efficient approaches to their synthesis are in high demand. Among indoles, 2‐aryl indoles have been described as privileged scaffolds. Advanced herein is a straightforward, practical, and transition‐metal‐free assembly of 2‐aryl indoles. Simply combining readily available 2‐fluorotoluenes, nitriles, LiN(SiMe3)2, and CsF enables the generation of a diverse array of indoles (38 examples, 48–92 % yield). A range of substituents can be introduced into each position of the indole backbone (C4 to C7, and aryl groups at C2), providing handles for further elaboration. 相似文献
184.
Shaowei Shi Bingqing Qian Xinyu Wu Huilou Sun Haiqiao Wang Hao‐Bin Zhang Zhong‐Zhen Yu Thomas P. Russell 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(50):18339-18344
2D transition metal carbides and nitrides (MXenes), a class of emerging nanomaterials with intriguing properties, have attracted significant attention in recent years. However, owing to the highly hydrophilic nature of MXene nanosheets, assembly strategies of MXene at liquid–liquid interfaces have been very limited and challenging. Herein, through the cooperative assembly of MXene and amine‐functionalized polyhedral oligomeric silsesquioxane at the oil–water interface, we report the formation, assembly, and jamming of a new type MXene‐based Janus‐like nanoparticle surfactants, termed MXene‐surfactants (MXSs), which can significantly enhance the interfacial activity of MXene nanosheets. More importantly, this simple assembly strategy opens a new platform for the fabrication of functional MXene assemblies from mesoscale (e.g., structured liquids) to macroscale (e.g., aerogels), that can be used for a range of applications, including nanocomposites, electronic devices, and all‐liquid microfluidic devices. 相似文献
185.
186.
Tlie rational designs of particle size, morphology and surface states of the Au nanoparticles(AuNPs) are crucial for Au nanocatalyst. We herein report a method to synthesize the silica microspheres supported AuNPs(ca.1 nm) and their application in controlling the reaction conversion and selectivity in styrene epoxidation. Surfactant-ftee AuNPs deposited on silica microspheres were in situ fabricated with aid of the Ag nanoparticles (AgNPs) as sacrificial template by galvanic replacement reaction, leading to AuNPs/SiO2 catalyst directly without any post-treatment to expose crystal facets.A high conversion of 46.7% and selectivity of 91.7% to styrene oxide was achieved with H2O2 as oxidant in ethanol. The solid catalyst could be reused at least 10 reaction cycles without significant decrease in activity and selectivity. This study not only supplies an active, recoverable catalyst for styrene oxidation with green oxidant and solvent, but also demonstrates that the silica microspheres functionalized with thiol groups have a superior ability in stabilizing noble metal nanoparticles even without any surfactant. 相似文献
187.
A series of novel TiO2/poly(aryl ether sulfone) ultrafiltration membranes with anti-fouling and self-cleaning properties was designed and prepared. First, anti-photocatalytic degraded fluorine contained polv(aryl ether sulfone) matrix(PAES-F) was synthesized. Then the composite membranes were prepared via TiO2 nanopartides and PAES-F polymer matrix by solution blending and non-solvent induced phase inversion methods. Further, separation efficiency, fouling behavior and self-cleaning property of the composite ultrafiltration(UF) membranes were investigated by dead-end filtration experiments using a polyacn lamide solution. The composite UF membranes exhibited outstanding self-cleaning efficiency and anti-photocatalytic degraded property after exposure to simulated sunliglit irradiation.The water flux recovery ratios(FRR)of the optimal composite UF membranes could reach 74.24%, which was attributable to photocatalytic degradation of the organic contaminant by TiO2. And the retention rates of the composite UF membranes could maintain over 97%, which indicated the excellent photocatalytic degradation resistance of the fluorine contained PAES-F matrix. The novel high perfomiance composite UF membranes have a broad application prospect in water treatment. 相似文献
188.
Guoxing Yin Tingting Niu Ting Yu Yabing Gan Xinyu Sun Peng Yin Haimin Chen Youyu Zhang Haitao Li Shouzhuo Yao 《Angewandte Chemie (International ed. in English)》2019,58(14):4557-4561
Studying numerous biologically important species simultaneously is crucial to understanding cellular functions and the root causes of related diseases. Direct visualization of endogenous biothiols in biological systems is of great value to understanding their biological roles. Herein, a novel multi‐signal fluorescent probe was rationally designed and exploited for the simultaneous sensing of homocysteine (Hcy), cysteine (Cys), and glutathione (GSH) using different emission channels. This probe was successfully applied to the simultaneous discrimination between and visualization of endogenous Hcy, Cys, GSH, and their transformation in living cells. 相似文献
189.
Ranran Fang Duanming Zhang Zhihua Li Fengxia Yang Li Li Xinyu Tan Min Sun 《Solid State Communications》2008,145(11-12):556-560
An improved thermal model describing UV high-power nanosecond laser ablation of metal target is presented. The vaporization effect, the plasma shielding effect, as well as the absorption coefficient and absorptivity dependence of temperature are considered in this model. Take iron target as an example, the numerical solutions are obtained from the heat flow equations (before and after melting) using a finite difference method. The space and time dependence of temperature of the target, the time dependence of temperature at two different positions for a certain laser fluence, and the ablation rate as a function of laser fluence are also presented. The numerical results that agreed well with the experimental data are much better than the one without, which indicates that the above two effects and the temperature dependence of absorption coefficient and absorptivity in UV high-power laser ablation of metal target should not be neglected. We hope the present model will be useful for further experimental investigation of metal thin films prepared by pulsed laser deposition. 相似文献