全文获取类型
收费全文 | 2508篇 |
免费 | 489篇 |
国内免费 | 288篇 |
专业分类
化学 | 554篇 |
晶体学 | 108篇 |
力学 | 32篇 |
综合类 | 27篇 |
数学 | 311篇 |
物理学 | 962篇 |
无线电 | 1291篇 |
出版年
2024年 | 3篇 |
2023年 | 19篇 |
2022年 | 40篇 |
2021年 | 63篇 |
2020年 | 41篇 |
2019年 | 56篇 |
2018年 | 62篇 |
2017年 | 103篇 |
2016年 | 121篇 |
2015年 | 106篇 |
2014年 | 146篇 |
2013年 | 237篇 |
2012年 | 153篇 |
2011年 | 200篇 |
2010年 | 137篇 |
2009年 | 164篇 |
2008年 | 179篇 |
2007年 | 180篇 |
2006年 | 164篇 |
2005年 | 139篇 |
2004年 | 113篇 |
2003年 | 126篇 |
2002年 | 123篇 |
2001年 | 85篇 |
2000年 | 76篇 |
1999年 | 52篇 |
1998年 | 55篇 |
1997年 | 41篇 |
1996年 | 35篇 |
1995年 | 30篇 |
1994年 | 39篇 |
1993年 | 29篇 |
1992年 | 30篇 |
1991年 | 18篇 |
1990年 | 29篇 |
1989年 | 17篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有3285条查询结果,搜索用时 15 毫秒
81.
Thermal stability of ester linkage in the presence of 1,2,3‐Triazole moiety generated by click reaction
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kyu Seong Lee So Yeong Park Hong Chul Moon Jin Kon Kim 《Journal of polymer science. Part A, Polymer chemistry》2017,55(3):427-436
The copper(I)‐catalyzed alkyne‐azide cycloaddition (CuAAC), so‐called “click” reaction, is one of most useful synthetic strategies to connect two polymer chains. 1,2,3‐Triazole ring (TA) produced by the click reaction has good thermal and chemical stability. However, we observed that block copolymers synthesized by the click reaction showed thermal degradation to give homopolymers when they are thermally annealed at high temperature, which is required for obtaining equilibrium microdomain structure. To investigate the origin of thermal instability of block copolymers, we synthesized model polystyrenes (PSs) using systematically designed bi‐functional atom transfer radical polymerization (ATRP) initiators containing TA. PS including both ester and TA groups showed thermal decomposition at relatively low temperature (e.g., 140 °C). MALDI‐TOF analysis clearly demonstrated that the cleavage site is the ester group adjacent to TA. We also found that the bromine group located at the polymer chain end plays an important role in pyrolysis of ester groups at low temperature. The pyrolysis occurs by syn‐elimination of the ester group. This result implies that the phase behavior of block copolymer synthesized by click reaction should be carefully investigated when high temperature thermal annealing is required. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 427–436 相似文献
82.
The flux and fluence dependence of disorder produced in silicon during the implantation of 11B has been investigated at room temperature, -50°C. and -120°C. Implantations were carried out with 200 keV 11B ions using current densities in the range from 0.06μA/cm2 to 15μA/cm2, and the disorder monitored by measuring the energy spectra of backscattered protons which were incident on the sample at 450 keV parallel to a (110) axis. Significant differences in the dependence of the disorder on 11B flux and fluence were observed between the implantations performed at room temperature and those carried out at the two lower temperatures. 相似文献
83.
Ion implantation followed by pulsed laser melting is an extensively-studied method for hyperdoping Si with impurity concentrations that exceed the equilibrium solubility limit by orders of magnitude. In the last decade, hyperdoped Si has attracted renewed interest for its potential as an intermediate band material. In this review, we first examine the important experimental results on both solid and liquid phase crystal regrowth from early laser annealing studies. The highly non-equilibrium regrowth kinetics following pulsed laser melting and its implications for dopant incorporation processes are discussed. We then review recent work in hyperdoped Si for enhanced sub-band gap photoresponse and give a brief discussion on photodetector device performance. 相似文献
84.
85.
86.
针对锗硅在形成金属锗硅化物时存在部分应力释放、界面形貌特性变差的问题,提出了在Si0.72Ge0.28上分别外延薄硅(Si)覆盖层和锗硅(Si072Ge0.28)缓冲层的工艺方案.实验结果表明,通过两步快速热退火,两个方案的工艺条件都能形成低阻的NiuPt1-uSitGe1-v和改善NivPt1-uSitGe./Si0.72Ge0.28的界面形貌.但相比较而言,在Si0.72Ge0.28上外延10 nm Si覆盖层的方案能够形成更好的NiuPt1-uSivGe1-t/Si0.72Ge0.28界面形貌.与没有改进的方案相比,该方案形成的肖特基接触更具有更低的肖特基接触势垒高度,更易形成欧姆接触. 相似文献
87.
88.
89.
Widely Tunable Morphologies in Block Copolymer Thin Films Through Solvent Vapor Annealing Using Mixtures of Selective Solvents
下载免费PDF全文
![点击此处可从《Advanced functional materials》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Michelle A. Chavis Detlef‐M. Smilgies Ulrich B. Wiesner Christopher K. Ober 《Advanced functional materials》2015,25(20):3057-3065
Thin films of block copolymers are extremely attractive for nanofabrication because of their ability to form uniform and periodic nanoscale structures by microphase separation. One shortcoming of this approach is that to date the design of a desired equilibrium structure requires synthesis of a block copolymer de novo within the corresponding volume ratio of the blocks. In this work, solvent vapor annealing in supported thin films of poly(2‐hydroxyethyl methacrylate)‐block‐poly(methyl methacrylate) [PHEMA‐b‐PMMA] by means of grazing incidence small angle X‐ray scattering (GISAXS) is investigated. A spin‐coated thin film of a lamellar block copolymer is solvent vapor annealed to induce microphase separation and improve the long‐range order of the self‐assembled pattern. Annealing in a mixture of solvent vapors using a controlled volume ratio of solvents, which are chosen to be preferential for each block, enables selective formation of ordered lamellae, gyroid, hexagonal, or spherical morphologies from a single‐block copolymer with a fixed volume fraction. The selected microstructure is then kinetically trapped in the dry film by rapid drying. This paper describes what is thought to be the first reported case where in situ methods are used to study the transition of block copolymer films from one initial disordered morphology to four different ordered morphologies, covering much of the theoretical diblock copolymer phase diagram. 相似文献
90.
采用水热法在FTO上制备(001)高活性晶面主导的TiO2纳米片薄膜,利用循环伏安法在TiO2纳米片薄膜上沉积CdSe颗粒,制备了TiO2/CdSe纳米片异质结薄膜。分别在150、250、350、450 ℃,氩气保护气氛中对样品进行退火。利用X射线衍射仪(XRD)、场发射扫描电镜(FESEM)、X射线光电子能谱分析仪(XPS)、紫外-可见(UV-Vis)分光光度计以及电化学工作站对不同温度退火后的TiO2/CdSe纳米片异质结薄膜的微观形貌、晶体结构、光电化学性能进行表征和测试。结果表明:六方相CdSe纳米颗粒均匀包覆在TiO2纳米片表面,直径30 nm左右;随着退火温度的升高CdSe纳米颗粒长大,形成光滑的CdSe薄膜,且晶化程度提高;TiO2纳米片表面的Se元素与Cd元素发生氧化;TiO2/CdSe纳米片异质结薄膜对可见光的吸收光谱发生红移,禁带宽度逐渐减小。光电化学性能测试表明随着退火温度的升高,TiO2/CdSe纳米片异质结薄膜的光电流密度显著提高,开路电压减小,但由于SeO2和CdO的出现,导致填充因子减小,影响光电转换效率的提高。在本实验条件下,TiO2/CdSe纳米片异质结薄膜的最佳退火温度为150 ℃,填充因子为0.77,光电转换效率达到3.12%。 相似文献