全文获取类型
收费全文 | 5864篇 |
免费 | 249篇 |
国内免费 | 29篇 |
专业分类
化学 | 3643篇 |
晶体学 | 105篇 |
力学 | 257篇 |
数学 | 693篇 |
物理学 | 1444篇 |
出版年
2023年 | 40篇 |
2022年 | 35篇 |
2021年 | 49篇 |
2020年 | 91篇 |
2019年 | 70篇 |
2018年 | 79篇 |
2017年 | 69篇 |
2016年 | 133篇 |
2015年 | 168篇 |
2014年 | 196篇 |
2013年 | 343篇 |
2012年 | 256篇 |
2011年 | 310篇 |
2010年 | 269篇 |
2009年 | 281篇 |
2008年 | 347篇 |
2007年 | 379篇 |
2006年 | 368篇 |
2005年 | 331篇 |
2004年 | 314篇 |
2003年 | 251篇 |
2002年 | 229篇 |
2001年 | 180篇 |
2000年 | 148篇 |
1999年 | 111篇 |
1998年 | 94篇 |
1997年 | 71篇 |
1996年 | 76篇 |
1995年 | 52篇 |
1994年 | 42篇 |
1993年 | 40篇 |
1992年 | 39篇 |
1991年 | 36篇 |
1990年 | 29篇 |
1989年 | 37篇 |
1988年 | 33篇 |
1987年 | 30篇 |
1986年 | 19篇 |
1985年 | 63篇 |
1984年 | 65篇 |
1983年 | 32篇 |
1982年 | 51篇 |
1981年 | 50篇 |
1980年 | 44篇 |
1979年 | 60篇 |
1978年 | 38篇 |
1977年 | 27篇 |
1976年 | 13篇 |
1975年 | 13篇 |
1974年 | 10篇 |
排序方式: 共有6142条查询结果,搜索用时 296 毫秒
11.
Synthesis and Self‐Assembly of Cyclic 2,7‐Anthrylene Ethynylene 1,3‐Phenylene Ethynylene Trimer with a Planar Conformation 下载免费PDF全文
Yuta Takaki Ryota Ozawa Dr. Takashi Kajitani Prof. Takanori Fukushima Prof. Masaaki Mitsui Prof. Kenji Kobayashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):16760-16764
Cyclic arylene ethynylene hexamer 1 , composed of alternating 2,7‐anthrylene ethynylene units and meta‐phenylene ethynylene units, was synthesized. It shows C3 symmetry and possesses a flat and rigid conformation with a large equilateral triangle‐like cavity. Macrocycle 1 self‐associates through π–π stacking interactions between the anthracene‐containing macrocyclic aromatic cores with indefinite‐association constant KE=6980 m ?1 in CDCl3 at 303 K. Macrocycle 1 also self‐assembles into π‐stacked nanofibers in the drop‐cast film. 相似文献
12.
Controllable Electronic Structures and Photoinduced Processes of Bay‐Linked Perylenediimide Dimers and a Ferrocene‐Linked Triad 下载免费PDF全文
Haruki Horinouchi Dr. Hayato Sakai Prof. Yasuyuki Araki Prof. Tomo Sakanoue Prof. Taishi Takenobu Prof. Takehiko Wada Prof. Nikolai V. Tkachenko Prof. Taku Hasobe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9631-9641
A series of perylene‐3,4,9,10‐bis(dicarboximide) (PDI) dimers linked through the bay regions was systematically synthesized to examine the electronic structures and photophysical properties in dependence on the distance and orientation between the two PDI units. The spectroscopic and electrochemical measurements suggested that the coupling value of a directly linked PDI dimer (PDI)2 is much larger than those of para‐ and meta‐phenylene‐bridged PDI dimers p‐(PDI)2 and m‐(PDI)2. The width of Davydov splitting was quantitatively evaluated to compare the coupling values between the two PDI units in these dimers by absorption spectroscopy in frozen 2‐methyl‐THF. Excimer formation of PDI dimers induced the strong fluorescence quenching and large red‐shifts. Femtosecond transient absorption revealed a broad absorption derived from an excimer in the range from about 600 nm to the near‐IR region. The rate constants of formation and decay of the excimer are strongly dependent on the coupling values. Time‐resolved measurements on ferrocene‐linked p‐(PDI)2 revealed a competition between the photoinduced processes of electron transfer and excimer formation in PhCN, which is in sharp contrast with the sole electron‐transfer process in toluene. 相似文献
13.
Control of chain ends of polyesters in polycondensation of AA and BB monomers by use of solid‐phase reagent 下载免费PDF全文
Toshihiko Sugiura Daisuke Yajima Kento Shoji Yoshihiro Ohta Tsutomu Yokozawa 《Journal of polymer science. Part A, Polymer chemistry》2015,53(11):1379-1386
For selective synthesis of linear polyester having a functional group at one end, polycondensation between 1,4‐butanediol ( 1a ) and sebacoyl chloride ( 2a ) and between 1,12‐dodecanediol ( 1b ) and isophthaloyl chloride ( 2b ) was conducted in the presence of oxime resin or oxime silica gel, followed by cleavage of the formed polyester from the solid‐phase support with aniline. Matrix‐assisted laser desorption ionization time‐of‐flight mass spectra and 1H NMR spectra of the cleaved polyester showed that the products contained not only polyester with anilide at one end ( poly 1 ), but also polyester with anilides at both ends ( poly 2 ). The product ratio of poly 1 to poly 2 ( poly 1 / poly 2 ) was dependent on monomers, monomer concentration, feed ratio of monomer to oxime moiety in the support, oxime content in the support, reaction solvent, and the nature of the support. Polyester with a high poly 1 / poly 2 ratio of 81/21 and moderate molecular weight (Mn = 1430 g/mol) was obtained by polycondensation of 1b and 2b in the presence of oxime silica gel in dichloromethane. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1379–1386 相似文献
14.
15.
16.
17.
Polycationic‐Shelled Capsular and Tubular Nanostructures and Their Anionic–Guest Binding Properties 下载免费PDF全文
Dr. Kohei Yazaki Dr. Yoshihisa Sei Prof. Dr. Munetaka Akita Dr. Michito Yoshizawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(49):17557-17561
For the development of novel nanospace with unique electrostatic character, we prepared new capsular and tubular nanostructures by the quantitative assembly of metal ions and bent bisacridinium ligands. The capsule and tube have closed spherical and open cylindrical cavities, respectively, with diameters of around 1 nm surrounded by cationic polyaromatic panels. Thanks to the facile synthetic protocol (three steps), another polycationic capsule with an elliptical nanocavity was also prepared by using an elongated ligand. In spite of the absence of pendant hydrophilic groups, the spherical polyaromatic capsule shows sufficient water solubility due to the polycationic shell. Moreover, the highly cationic cavity (12+) can selectively encapsulate anionic organic compounds in water. 相似文献
18.
19.
Direct Estimation of the Surface Location of Immobilized Functional Groups for Concerted Catalysis Using a Probe Molecule 下载免费PDF全文
Hiroto Noda Dr. Ken Motokura Prof. Dr. Yusuke Wakabayashi Kaori Sasaki Dr. Hiroo Tajiri Dr. Akimitsu Miyaji Dr. Sho Yamaguchi Prof. Dr. Toshihide Baba 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(15):5113-5117
The location of active sites during concerted catalysis by a metal complex and tertiary amine on a SiO2 surface is discussed based on the interaction between the functionalized SiO2 surface and a probe molecule, p‐formyl phenylboronic acid. The interactions of the probe molecule with the surface functionalities, diamine ligand, and tertiary amine, were analyzed by FT‐IR and solid‐state 13C and 11B MAS NMR. For the catalyst exhibiting high 1,4‐addition activity, the diamine ligand and tertiary amine base exist in closer proximity than in the catalyst with low activity. 相似文献
20.
Reassessment of the NH4NO3 thermal decomposition technique for calibration of the N2O isotopic composition 下载免费PDF全文