全文获取类型
收费全文 | 21392篇 |
免费 | 565篇 |
国内免费 | 146篇 |
专业分类
化学 | 14944篇 |
晶体学 | 113篇 |
力学 | 545篇 |
数学 | 3695篇 |
物理学 | 2806篇 |
出版年
2022年 | 111篇 |
2021年 | 213篇 |
2020年 | 227篇 |
2019年 | 239篇 |
2018年 | 191篇 |
2017年 | 188篇 |
2016年 | 405篇 |
2015年 | 417篇 |
2014年 | 452篇 |
2013年 | 967篇 |
2012年 | 1047篇 |
2011年 | 1325篇 |
2010年 | 670篇 |
2009年 | 629篇 |
2008年 | 1132篇 |
2007年 | 1160篇 |
2006年 | 1197篇 |
2005年 | 1248篇 |
2004年 | 1086篇 |
2003年 | 931篇 |
2002年 | 830篇 |
2001年 | 272篇 |
2000年 | 273篇 |
1999年 | 218篇 |
1998年 | 228篇 |
1997年 | 280篇 |
1996年 | 332篇 |
1995年 | 223篇 |
1994年 | 228篇 |
1993年 | 197篇 |
1992年 | 193篇 |
1991年 | 178篇 |
1990年 | 172篇 |
1989年 | 151篇 |
1988年 | 164篇 |
1987年 | 171篇 |
1986年 | 132篇 |
1985年 | 293篇 |
1984年 | 258篇 |
1983年 | 195篇 |
1982年 | 268篇 |
1981年 | 220篇 |
1980年 | 282篇 |
1979年 | 253篇 |
1978年 | 251篇 |
1977年 | 255篇 |
1976年 | 220篇 |
1975年 | 177篇 |
1974年 | 169篇 |
1973年 | 160篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Molecular and morphological characterization of midblock‐sulfonated styrenic triblock copolymers
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kenneth P. Mineart Justin J. Ryan Byeongdu Lee Steven D. Smith Richard J. Spontak 《Journal of Polymer Science.Polymer Physics》2017,55(6):490-497
Midblock‐sulfonated triblock copolymers afford a desirable opportunity to generate network‐forming amphiphilic materials that are suitable for use in a wide range of emerging technologies as fuel‐cell, water‐desalination, ion‐exchange, photovoltaic, or electroactive membranes. Employing a previously reported synthetic strategy wherein poly(p‐tert‐butylstyrene) remains unreactive, we have selectively sulfonated the styrenic midblock of a poly(p‐tert‐butylstyrene‐b‐styrene‐b‐p‐tert‐butylstyrene) (TST) triblock copolymer to different extents. Comparison of the resulting sulfonated copolymers with results from our prior study provides favorable quantitative agreement and suggests that a shortened reaction time is advantageous. An ongoing challenge regarding the morphological development of charged block copolymers is the competition between microphase separation of the incompatible blocks and physical cross‐linking of ionic clusters, with the latter often hindering the former. Here, we expose the sulfonated TST copolymers to solvent‐vapor annealing to promote nanostructural refinement. The effect of such annealing on morphological characteristics, as well as on molecular free volume, is explored. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 490–497 相似文献
972.
973.
Taratra André Fenoradosoa Céline Laroche Cedric Delattre Virginie Dulong Didier Le Cerf Luc Picton Philippe Michaud 《Applied biochemistry and biotechnology》2012,167(5):1303-1313
The rheological behavior of a sulfated galactan extracted from Halymenia durvillei, a red seaweed collected in the coastal waters of a small island of Madagascar (Nosy-be in Indian Ocean), was investigated in dilute and semi-dilute solutions. In dilute solution with NaCl at 0.3?M, the polysaccharide adopted a coil conformation whereas, at higher concentrations, the polymer had the behavior of shear-thinning fluid, typical of polymer with high molar mass or semi-rigid conformation. Degradations of this lambda carrageenan-like, using radical depolymerization, and high-pressure homogenization led to several samples of various and controlled molar masses. The measure of their intrinsic viscosities permitted the determination of the relationship of Mark?CHouwink?CSakurada. 相似文献
974.
Mohammed I. Jeraal Nicholas Holmes Geoffrey R. Akien Richard A. Bourne 《Tetrahedron》2018,74(25):3158-3164
Reaction optimisation and understanding is fundamental for process development and is achieved using a variety of techniques. This paper explores the use of self-optimisation and experimental design as a tandem approach to reaction optimisation. A Claisen-Schmidt condensation was optimised using a branch and fit minimising algorithm, with the resulting data being used to fit a response surface model. The model was then applied to find new responses for different metrics, highlighting the most important for process development purposes. 相似文献
975.
976.
We prove the almost sure existence of absolutely continuous spectrum at low disorder for the Anderson model on the simplest example of a product of a regular tree with a finite graph. This graph contains loops of unbounded size. 相似文献
977.
978.
979.
Complex new materials from simple chemistry: Combining an amino‐substituted polysiloxane and carboxylic acids
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)
Yong He Hui Zhao Miao Yao Richard G. Weiss 《Journal of polymer science. Part A, Polymer chemistry》2017,55(23):3851-3861
Changes in rheological, adhesive, and swelling properties of quaternary salts, made by adding one of eight mono‐ or six α,ω‐alkanedioic acids (the latter with two to six or nine carbon atoms) to 6‐7PSil (a polysiloxane with 6%–7% of the monomer units contain a 3‐aminopropyl group) have been correlated with the salt structures. The simple acid‐base chemistry initiates drastic changes in the bulk properties of the materials that depend on the amount and type of the added acid. Thus, the quaternized forms of the 6‐7PSil have significantly enhanced viscoelastic and adhesive properties compared to those of the initial polysiloxane, and they can swell selectively liquids based on their polarity. Also, interpenetrating networks have been made in situ by photopolymerization of salts with vinylic carboxylic acids. DFT calculations on model systems consisting of dimethylammonium α,ω‐alkanedioate salts with two to six carbon atoms provide insights into the interactions responsible for the unexpected dependence of the properties of the 6‐7PSil salts on the chain lengths of the diacids. The potential for applying the methodologies described here to systems with other amino‐substituted polymers and other acid types is noted. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3851–3861 相似文献
980.
Ricardo Abreu-Blaya Juan Bory-Reyes Richard Delanghe Frank Sommen 《Complex Analysis and Operator Theory》2012,6(2):341-357
In this paper, using the ring structure of the space of circulant (2 × 2)-matrix, we characterize the dual of the (Fréchet)
space of germs of left Hermitean monogenic matrix functions in a compact set
_boxclose_boxclose_boxclose_boxclose_boxclose_boxclose_boxclose_boxclose R^2n{{\bf E}\subset\mathbb R^{2n}}. As an application we describe the dual space of the so-called h-monogenic functions satisfying simultaneously two Dirac type equations. 相似文献