全文获取类型
收费全文 | 6371篇 |
免费 | 169篇 |
国内免费 | 27篇 |
专业分类
化学 | 3342篇 |
晶体学 | 148篇 |
力学 | 258篇 |
数学 | 1033篇 |
物理学 | 1786篇 |
出版年
2022年 | 98篇 |
2021年 | 113篇 |
2020年 | 108篇 |
2019年 | 129篇 |
2018年 | 106篇 |
2017年 | 134篇 |
2016年 | 181篇 |
2015年 | 143篇 |
2014年 | 220篇 |
2013年 | 482篇 |
2012年 | 343篇 |
2011年 | 353篇 |
2010年 | 247篇 |
2009年 | 219篇 |
2008年 | 294篇 |
2007年 | 291篇 |
2006年 | 242篇 |
2005年 | 221篇 |
2004年 | 194篇 |
2003年 | 142篇 |
2002年 | 131篇 |
2001年 | 83篇 |
2000年 | 70篇 |
1999年 | 68篇 |
1998年 | 57篇 |
1997年 | 36篇 |
1996年 | 60篇 |
1995年 | 57篇 |
1994年 | 64篇 |
1993年 | 80篇 |
1992年 | 73篇 |
1991年 | 55篇 |
1990年 | 63篇 |
1989年 | 63篇 |
1988年 | 70篇 |
1987年 | 58篇 |
1985年 | 78篇 |
1984年 | 101篇 |
1983年 | 62篇 |
1982年 | 78篇 |
1981年 | 71篇 |
1980年 | 78篇 |
1979年 | 76篇 |
1978年 | 71篇 |
1977年 | 62篇 |
1976年 | 58篇 |
1975年 | 44篇 |
1974年 | 47篇 |
1973年 | 56篇 |
1972年 | 35篇 |
排序方式: 共有6567条查询结果,搜索用时 0 毫秒
11.
Alvaro Carrillo Ravi S. Kane 《Journal of polymer science. Part A, Polymer chemistry》2004,42(13):3352-3359
This article describes the formation and characterization of self‐assembled nanoparticles of controlled sizes based on amphiphilic block copolymers synthesized by ring‐opening metathesis polymerization. We synthesized a novel hydrophobic derivative of norbornene; this monomer could be polymerized using Grubbs' catalyst [Cl2Ru(CHPh)(PCy3)2] forming polymers of controlled molecular weight. We synthesized amphiphilic block copolymers of controlled composition and showed that they assemble into nanoparticles of controlled size. The nanoparticles were characterized using dynamic light scattering and transmission electron microscopy. Tuning the composition of the block copolymer enables the tuning of the diameters of the nanoparticles in the 30‐ to 80‐nm range. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3352–3359, 2004 相似文献
12.
13.
Europium (Eu+) ions were confined in a Paul trap and detected by non-destructive method. Storage time of Eu+ ions achieved in vacuum was improved by orders of magnitude employing buffer gas cooling. The experimentally detected signal
was fitted to the ion response signal and the total number of ions trapped was estimated. It is found that the peak signal
amplitude as well as the product of FWHM and the peak signal amplitude is proportional to the total number of trapped ions.
The trapped ion secular frequency was swept at different rates and its effect on the absorption line profile was studied both
experimentally and theoretically. 相似文献
14.
15.
A Monte Carlo simulation method is used to study thermal desorption of gas molecules from mixed adlayers containing two species. The effects of lateral interactions among adatoms and initial surface coverage on the desorption spectra are examined. It is shown that attractive lateral interactions lead to sharper peaks and that desorption occurs at high temperatures, whereas repulsive interactions lead to multiple peak spectra. It is found that interactions between unlike molecules affect the spectra for species with lower desorption energy only, and that the two species desorb together only in certain cases. Lateral interactions also affect the desorption kinetics significantly and very different behavior for the two species may be obtained. 相似文献
16.
Leong‐Huat Gan Palaniswamy Ravi Bao Wei Mao Kam‐Chiu Tam 《Journal of polymer science. Part A, Polymer chemistry》2003,41(17):2688-2695
Polymerization of 2‐(diethylamino)ethyl methacrylate (DEAEMA) via homogeneous atom transfer radical polymerization under various reaction conditions is described. The effects of the initiators and solvents were examined. With 1,1,4,7,10,10‐hexamethyl triethylenetetramine/copper(I) chloride/p‐toluenesulfonyl chloride as the ligand/catalyst/initiator system in methanol, poly(DEAEMA) with a polydispersity index as low as 1.07 was synthesized. Kinetic studies demonstrated the polymerization was very well controlled and exhibited the living characteristic of the process. Well‐defined block copolymers of DEAEMA and tert‐butyl methacrylate (tBMA) were successfully synthesized. The copolymers could be synthesized with equally good results by starting with either p(DEAEMA) or p(tBMA) as the macroinitiators. However, only the macroinitiators terminated with chlorine should be used. The corresponding macroinitiators with bromine as a transferable group did not yield well‐defined copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2688–2695, 2003 相似文献
17.
18.
We have given design of a very small residual dispersion fiber system consisting of a small dispersion fiber(SDF) with flat modal field and a corresponding dual core coaxial dispersion compensating fiber (DCF). 相似文献
19.
S K Samanta U C Gupta R K Sharma 《The Journal of the Operational Research Society》2007,58(3):368-377
This paper investigates a discrete-time single-server finite-buffer queueing system with multiple vacations in which arrivals occur according to a discrete-time renewal process. Service and vacation times are mutually independent and geometrically distributed. We obtain steady-state system length distributions at prearrival, arbitrary and outside observer's observation epochs under the late arrival system with delayed access and early arrival system. The analysis of actual waiting-time for both the systems has also been carried out. The model has potential application in high-speed computer network, digital communication systems and other related areas. 相似文献
20.
M.K. Gupta Vijay Gupta Manoj Kumar 《Journal of Mathematical Analysis and Applications》2007,330(2):799-816
In the present paper we introduce a new family of linear positive operators and study some direct and inverse results in simultaneous approximation. 相似文献