全文获取类型
收费全文 | 1127篇 |
免费 | 43篇 |
国内免费 | 6篇 |
专业分类
化学 | 848篇 |
晶体学 | 11篇 |
力学 | 16篇 |
数学 | 88篇 |
物理学 | 213篇 |
出版年
2023年 | 10篇 |
2022年 | 9篇 |
2021年 | 15篇 |
2020年 | 11篇 |
2019年 | 20篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 23篇 |
2015年 | 35篇 |
2014年 | 32篇 |
2013年 | 56篇 |
2012年 | 95篇 |
2011年 | 105篇 |
2010年 | 42篇 |
2009年 | 40篇 |
2008年 | 83篇 |
2007年 | 63篇 |
2006年 | 64篇 |
2005年 | 70篇 |
2004年 | 58篇 |
2003年 | 47篇 |
2002年 | 57篇 |
2001年 | 10篇 |
2000年 | 14篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 14篇 |
1996年 | 16篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 9篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1968年 | 2篇 |
1961年 | 2篇 |
1960年 | 2篇 |
排序方式: 共有1176条查询结果,搜索用时 15 毫秒
121.
Zhang N Ouyang S Li P Zhang Y Xi G Kako T Ye J 《Chemical communications (Cambridge, England)》2011,47(7):2041-2043
Micro/mesoporous Zn(2)GeO(4) with crystalline pore-walls was successfully synthesized via a simple ion exchange method at room temperature. This structure showed enhanced activity in photoreduction of CO(2) in comparison with Zn(2)GeO(4) prepared by a solid state reaction. 相似文献
122.
Makoto Masuda Satoru Takamatu Noriyuki Nishimura Saburo Komatsubara Tetsuya Tosa 《Applied biochemistry and biotechnology》1993,43(3):189-197
Serratia marcescens SP511 was previously reported to be anl-proline-producing strain that harbors a recombinant plasmid carrying the mutant type of the proline operon. This strain produced 65 g/L ofl-proline in a medium containing 22% sucrose and urea after 5 d of incubation under the conventional culture conditions. We searched for more suitable culture conditions for more abundantl-proline production by SP511. To improve the supply of a nitrogen source to cells, ammonium was used instead of urea and fed to a culture under control of the pH of the medium. The concentrations of MgSO4 and K2HPO4 were increased, and in addition, sucrose was continuously added to the culture at a final concentration of 32%. Under these conditions, the cell amount was increased twofold over that under the previous conditions andl-proline production reached a maximum of more than 100 g/L after 4 d of incubation. 相似文献
123.
Tetsuya Shimizu Yasuka Komatsu Hidenobu Kamihata Young Hoon Lee Akira Fuyuhiro Seiichiro Iijima Shinya Hayami 《Journal of inclusion phenomena and macrocyclic chemistry》2011,71(3-4):363-369
Iron(III) spin-crossover compounds, [Fe(qnal)2]CF3SO3·MeOH (1·MeOH) and [Fe(qnal)2]CF3SO3·acetone (1·acetone) were prepared and their spin transition properties were characterized by magnetic susceptibility measurement, Mössbauer spectroscopy and single crystal analysis. Two iron(III) compounds exhibited abrupt spin transition with thermal hysteresis loop (T 1/2?? = 115 K and T 1/2?? = 104 K for 1·MeOH, and T 1/2?? = 133 K and T 1/2?? = 130 K for 1·acetone). Single crystal analysis revealed both of the structures in high-spin (HS) and low-spin (LS) states for 1·acetone. The difference of bond length between the HS and LS states for 1·acetone was ~0.10 Å, which was corresponding to that of typical iron(III) SCO compounds. Specially, it showed strong intermolecular interactions by ???C?? stacking formed between the neighbor complexes leading to 2-D sheet. Both 1·MeOH and 1·acetone exhibited LIESST effect when it was illuminated at 1000 nm. We also confirmed that the introduction of strong intermolecular interactions, such as ???C?? stacking, can play an important role in LIESST effect. 相似文献
124.
Tetsuya Yamamoto 《Colloid and polymer science》2013,291(11):2741-2744
Methacrylic monomer was used in soap-free emulsion polymerization in order to obtain a stable dispersion containing particles of the polymerized monomer. 2,2′-Azobis(2-methylpropionitrile) (AIBN) or 1,1′-azobis(1-acetoxy-1-phenylethane) (OTAZO-15) were used as the radical initiator. Although particles with a size of about 1.0 μm were obtained when using methyl methacrylate as the monomer and AIBN as the initiator, the particles did not exhibit good dispersion stability. When OTAZO-15, which has phenyl rings, was used as the initiator, the monomer phase solidified instead of forming particles in the aqueous phase. Benzyl methacrylate (BMA) monomer, which contains a phenyl ring, was polymerized using AIBN. Negatively charged particles with a size of 0.90 μm were formed. These particles exhibited good dispersion stability probably because of the pi electrons of the phenyl ring in the BMA monomer. The method in this study allows the synthesis of nearly micron-sized particles without surfactant, organic solvent, and electrolyte. 相似文献
125.
In many polymers under corrosive liquids, degradation followed after permeation of environmental solution for a long period. The permeation rate of environmental solution, in many cases, is very low in corrosion-resistant polymeric materials. Therefore, the observation of the permeation of environmental solution and degradation of polymeric materials are very difficult in practical application. A simulation of permeation of solution is required in order to understand the permeation behavior of environmental solution and polymer degradation. A detailed analysis of the permeation behavior of solution accompanied by chemical reaction is important to study for improving the lifetime of polymers. Polyamide 66 (PA66) and sulfuric acid solution were used to investigate the quantitative study of permeation of environmental solution and its relation to degradation of polymeric materials. Correlation between diffusion process and degradation of PA66 related to the decrease of weight average molecular weight was defined. The diffusion rate of sulfuric acid solution was found to increase by decreasing weight average molecular weight of PA66 due to the established chain scission by hydrolysis reaction. The permeation of sulfuric acid solution that affected the decomposition reaction was modeled and quantitative evaluation of permeation of sulfuric acid was established. 相似文献
126.
127.
Itsuki Shindachi Hiroshi Hanaki Ryo Sasai Tetsuya Shichi Tatsuto Yui Katsuhiko Takagi 《Research on Chemical Intermediates》2007,33(1-2):143-153
Diarylethene derivatives (DE) covalently bonded to silanol oxygens of layered silicate surfaces, i.e., magadiite (Mag), were synthesized and investigated for their photochromic behavior. The DE-Mag layered hybrids were found to undergo reversible color change by alternating UV and visible light irradiation. A more highly efficient, reproducible photochromic behavior was realized with DE-Mag than with a corresponding DE-Si possessing silyl substituents on DE in place of the Mag surface. Moreover, the present covalently bonded DE exhibited an improvement over DE hybrids incorporated in layered double hydroxide (LDH) clays, in which the repetitive photochromic behavior decreased during alternating irradiation, due to the accumulation of the photochemically inert parallel isomers of DE. 相似文献
128.
Shinsuke Takagi Miharu Eguchi Tetsuya Shimada Satoshi Hamatani Haruo Inoue 《Research on Chemical Intermediates》2007,33(1-2):177-189
Photochemical energy transfer of non-aggregated cationic porphyrins on an anionic-type clay (Smecton SA) surface was investigated. The efficiency of energy transfer and excited-state quenching in the absence of energy transfer were evaluated at various loading levels of porphyrin on the clay surface and were found to be significantly affected by the loading level. As the latter increased, both energy transfer efficiency and excited-state quenching increased. Judging from the dependency of energy-transfer efficiency on the porphyrin loading level, a partially clustered structure, but without aggregation, of porphyrins on the clay surface is proposed. 相似文献
129.
Oxidative Annulation of Arenecarboxylic and Acrylic Acids with Alkynes under Ambient Conditions Catalyzed by an Electron‐Deficient Rhodium(III) Complex 下载免费PDF全文
Eiji Kudo Dr. Yu Shibata Mutsumi Yamazaki Koji Masutomi Dr. Yuta Miyauchi Miho Fukui Haruki Sugiyama Prof. Dr. Hidehiro Uekusa Prof. Dr. Tetsuya Satoh Prof. Dr. Masahiro Miura Prof. Dr. Ken Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14190-14194
It has been established that an electron‐deficient CpE rhodium(III) complex catalyzes the oxidative [4+2] annulation of substituted arenecarboxylic and acrylic acids with alkynes under ambient conditions (at RT–40 °C, under air) without using excess amounts of substrates to produce the corresponding substituted isocoumarins and α‐pyrones in high yields. Minor modification of reaction conditions depending on the coordination ability of alkynes realized the high efficiency. 相似文献
130.
A novel oxidative cyclization of quinone-arenols 5 leading to products 6 with a dibenzofuran-1,4-dione structure, which forms the core of several natural products, has been developed and applied to the synthesis of violet-quinone (4). 相似文献