全文获取类型
收费全文 | 1199篇 |
免费 | 20篇 |
国内免费 | 3篇 |
专业分类
化学 | 925篇 |
晶体学 | 12篇 |
力学 | 10篇 |
数学 | 75篇 |
物理学 | 200篇 |
出版年
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 16篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 18篇 |
2015年 | 13篇 |
2014年 | 11篇 |
2013年 | 44篇 |
2012年 | 44篇 |
2011年 | 59篇 |
2010年 | 37篇 |
2009年 | 41篇 |
2008年 | 83篇 |
2007年 | 61篇 |
2006年 | 66篇 |
2005年 | 79篇 |
2004年 | 64篇 |
2003年 | 58篇 |
2002年 | 53篇 |
2001年 | 34篇 |
2000年 | 32篇 |
1999年 | 17篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 20篇 |
1984年 | 33篇 |
1983年 | 12篇 |
1982年 | 20篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 14篇 |
1977年 | 17篇 |
1976年 | 12篇 |
1975年 | 11篇 |
1974年 | 7篇 |
1973年 | 9篇 |
1969年 | 6篇 |
1968年 | 6篇 |
排序方式: 共有1222条查询结果,搜索用时 15 毫秒
1.
Ferroelectric Coordination Polymers Self‐Assembled from Mesogenic Zinc(II) Porphyrin and Dipolar Bridging Ligands 下载免费PDF全文
Dr. Joseph K.‐H. Hui Hiroyuki Kishida Keita Ishiba Kenta Takemasu Dr. Masa‐aki Morikawa Prof. Dr. Nobuo Kimizuka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14213-14218
A new class of ferroelectric coordination‐based polymers has been developed by the self‐assembly of lipophilic zinc porphyrin ( ZnP ) and ditopic bridging ligands. The ligands contain dipolar benzothiadiazole or fluorobenzene units, which are axially coordinated to ZnP with the dipole moments oriented perpendicular to the coordination axes. The coordination‐based polymers show ferroelectric characteristics in the liquid crystalline state, as revealed by distinctive hysteresis in the polarization–electric field (P–E) loops and inversion current peaks in current–voltage (I–V) loops. The observed ferroelectric properties are explainable by flip–flop rotation of the dipolar axle ligands induced by the applied electric field, as demonstrated by the positive‐up–negative‐down (PUND) measurements. The present system provides a new operating principle in supramolecular ferroelectrics. 相似文献
2.
3.
Ruthenium‐Immobilized Periodic Mesoporous Organosilica: Synthesis,Characterization, and Catalytic Application for Selective Oxidation of Alkanes 下载免费PDF全文
Nobuhiro Ishito Dr. Hirokazu Kobayashi Dr. Kiyotaka Nakajima Yoshifumi Maegawa Dr. Shinji Inagaki Dr. Kenji Hara Prof. Dr. Atsushi Fukuoka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15564-15569
Periodic mesoporous organosilica (PMO) is a unique material that has a crystal‐like wall structure with coordination sites for metal complexes. A Ru complex, [RuCl2(CO)3]2, is successfully immobilized onto 2,2’‐bipyridine (BPy) units of PMO to form a single‐site catalyst, which has been confirmed by various physicochemical analyses. Using NaClO as an oxidant, the Ru‐immobilized PMO oxidizes the tertiary C?H bonds of adamantane to the corresponding alcohols at 57 times faster than the secondary C?H bonds, thereby exhibiting remarkably high regioselectivity. Moreover, the catalyst converts cis‐decalin to cis‐9‐decalol in a 63 % yield with complete retention of the substrate stereochemistry. The Ru catalyst can be separated by simple filtration and reused without loss of the original activity and selectivity for the oxidation reactions. 相似文献
4.
Cellulose - Given that terahertz (THz) radiation responds to intermolecular forces such as hydrogen bonds, THz time-domain spectroscopy (THz-TDS) has expanded possibilities in cellulose research.... 相似文献
5.
6.
Three novel naphthoquinone-based heterocyclic pigments, 2-methyl-3-[(1-methyl-1H-imidazol-2-yl)thio-1,4-naphthalenedione, (4-methyl-4H-1,2,4-triazol-3-yl)thio-1,4-naphthalenedione, and (1-methyl-1H-tetrazol-5-yl)thio]-1,4-naphthalenedione, are synthesized, and their optical properties in both solution and solid states are investigated. Depending on the heteroarylthio ring in the pigment, variation in optical properties is observed, e.g. characteristic colours for each pigment in the solution and solid states. The achiral pigment containing the 1-methyl-1H-tetrazol-5-yl ring exhibits a chiral space group and a CD signal in the solid state. 相似文献
7.
Sho Inagaki Akari Sato Haruka Sato Satoru Tamura Tomikazu Kawano 《Tetrahedron letters》2017,58(52):4872-4875
A simple and efficient synthesis of 4,5-dihydro-4-oxo-3-furancarboxylates using an acylative intramolecular cyclization of sulfonium salts is described. The reaction involved the efficient formation of a mixed anhydride between a linear carboxylic acid and trifluoroacetic anhydride in the presence of N-methylimidazole, followed by the sequential conversion into a highly reactive acylammonium species in situ. This procedure is easily handled, uses readily available inexpensive reagents, and provides a variety of 2-substituted 4,5-dihydro-4-oxo-3-furancarboxylates. 相似文献
8.
9.