全文获取类型
收费全文 | 578篇 |
免费 | 35篇 |
国内免费 | 6篇 |
专业分类
化学 | 515篇 |
晶体学 | 5篇 |
力学 | 4篇 |
数学 | 29篇 |
物理学 | 66篇 |
出版年
2023年 | 5篇 |
2022年 | 3篇 |
2021年 | 10篇 |
2020年 | 8篇 |
2019年 | 19篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 18篇 |
2015年 | 11篇 |
2014年 | 19篇 |
2013年 | 30篇 |
2012年 | 33篇 |
2011年 | 37篇 |
2010年 | 15篇 |
2009年 | 15篇 |
2008年 | 34篇 |
2007年 | 39篇 |
2006年 | 36篇 |
2005年 | 34篇 |
2004年 | 28篇 |
2003年 | 30篇 |
2002年 | 18篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 7篇 |
1996年 | 13篇 |
1995年 | 3篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1989年 | 2篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有619条查询结果,搜索用时 906 毫秒
611.
Hiroki Tanaka Yohei Haketa Yuya Bando Ryohei Yamakado Nobuhiro Yasuda Hiromitsu Maeda 《化学:亚洲杂志》2020,15(4):494-498
Anion complexes of anion‐responsive π‐electronic molecules can behave as pseudo π‐electronic anions providing various ion pairs in combination with countercations. In this study, single crystals of ion‐pairing assemblies comprising porphyrin–AuIII complexes and Cl? complexes of dipyrrolyldiketone BF2 complexes were prepared from 1:1 mixtures of anion receptors and the Cl? salts of cationic porphyrins in solution. In the solid state, the ion pairs formed characteristic assemblies, depending on the substituents of the anion receptors and porphyrin–AuIII complexes. Theoretical calculations on the ion pairs revealed that the stacking structures are stabilized by compensating positive and negative charges as well as π–π interactions. 相似文献
612.
613.
Takashi Kamitanaka Tatsuyoshi Hikida Nobuhiro Kishida Tadao Harada 《Tetrahedron letters》2007,48(48):8460-8463
The reactions of the alkenes with supercritical organic compounds under non-catalytic conditions were investigated. The H and CR2OH, CH2COCH3 or CH2CN of supercritical alcohols (CHR2OH), acetone (CH3COCH3) or acetonitrile (CH3CN) added to the CC bonds of alkenes form C-C bonds between the α-carbons of the supercritical organic compounds and the sp2 carbons of the alkenes. 相似文献
614.
Yoshinori Maeda Frederico Pittella Takahiro Nomoto Hiroyasu Takemoto Nobuhiro Nishiyama Kanjiro Miyata Kazunori Kataoka 《Macromolecular rapid communications》2014,35(13):1211-1215
For efficient delivery of siRNA into the cytoplasm, a smart block copolymer of poly(ethylene glycol) and charge‐conversion polymer (PEG‐CCP) is developed by introducing 2‐propionic‐3‐methylmaleic (PMM) amide as an anionic protective group into side chains of an endosome‐disrupting cationic polyaspartamide derivative. The PMM amide moiety is highly susceptible to acid hydrolysis, generating the parent cationic polyaspartamide derivative at endosomal acidic pH 5.5 more rapidly than a previously synthesized cis‐aconitic (ACO) amide control. The PMM‐based polymer is successfully integrated into a calcium phosphate (CaP) nanoparticle with siRNA, constructing PEGylated hybrid micelles (PMM micelles) having a sub‐100 nm size at extracellular neutral pH 7.4. Ultimately, PMM micelles achieve the significantly higher gene silencing efficiency in cultured cancer cells, compared to ACO control micelles, probably due to the efficient endosomal escape of the PMM micelles. Thus, it is demonstrated that fine‐tuning of acid‐labile structures in CCP improves the delivery performance of siRNA‐loaded nanocarriers.
615.
Okuda M Ogawa N Takeguchi M Hashimoto A Tagaya M Chen S Hanagata N Ikoma T 《Microscopy and microanalysis》2011,17(5):788-798
The mineralized structure of aligned collagen fibrils in a tilapia fish scale was investigated using transmission electron microscopy (TEM) techniques after a thin sample was prepared using aqueous techniques. Electron diffraction and electron energy loss spectroscopy data indicated that a mineralized internal layer consisting of aligned collagen fibrils contains hydroxyapatite crystals. Bright-field imaging, dark-field imaging, and energy-filtered TEM showed that the hydroxyapatite was mainly distributed in the hole zones of the aligned collagen fibrils structure, while needle-like materials composed of calcium compounds including hydroxyapatite existed in the mineralized internal layer. Dark-field imaging and three-dimensional observation using electron tomography revealed that hydroxyapatite and needle-like materials were mainly found in the matrix between the collagen fibrils. It was observed that hydroxyapatite and needle-like materials were preferentially distributed on the surface of the hole zones in the aligned collagen fibrils structure and in the matrix between the collagen fibrils in the mineralized internal layer of the scale. 相似文献
616.
Hajime Kobori Atsushi Sekiya Nobuhiro Yasuda Keiichi Noguchi Tomohiro Suzuki Jae-Hoon Choi Hirofumi Hirai Hirokazu Kawagishi 《Tetrahedron letters》2013
Three novel compounds were isolated from the culture broth of Armillaria sp. Their structures were elucidated mainly by spectroscopic data analyses. All the compounds regulated hypocotyl and root growth of lettuce. 相似文献
617.
Norihiro Tokitoh Daisuke Shimizu Nobuhiro Takeda Takahiro Sasamori 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5-6):1241-1245
Abstract New types of o-phenylene-bridged polythioethers tethered with extremely bulky aryl groups at their terminal sulfur atoms, such as TbtS(o-Phen)S(o-Phen)S(o-Phen)STbt (1) and TbtS(o-Phen)S(o-Phen)SS(o-Phen)S(o-Phen)STbt (2) (Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, o-Phen = o-phenylene), were synthesized and subjected to the complexation with several kinds of late-transition metals. In the case of polythioether 1, the reaction with RhCl3·3H2O in benzene/EtOH resulted in the formation of a unique bimetallic complex, in which a part of ligand 1 is lost and the resulting sulfur atom is directly bound to the other Rh metal center. Interestingly, similar treatment of 1 with IrCl3·3H2O afforded ethyl-coordinated mononuclear Ir complex. Furthermore, 1 underwent complexation with Na2PdCl4 in EtOH to give the corresponding square planar dichloropalladium complex coordinated with two inner sulfur atoms of 1, while the S6-ligand 2 reacted with excess of Pd(PPh3)4 in benzene to afford a quite interesting trinuclear Pd complex multi-step metal insertion reactions. 相似文献
618.
Katsumata K Ohno Y Tomita K Sakai M Nakajima A Kakihana M Fujishima A Matsushita N Okada K 《Photochemistry and photobiology》2011,87(5):988-994
Titanium dioxide thin films were prepared by using four water-soluble titanium complexes of titanium-lactate, tartalate, malate and salicylate complex solutions. The crystalline phases detected in the films were anatase. The surface microstructures of the four film samples were different in their grain sizes. Photocatalytic decomposition activity of the four films was almost the same, but their photoinduced hydrophilicities were different. The film prepared using titanium-salicylate complex exhibited lower hydrophilic conversion rate than the other films. Grain size and stress yielded to the film are considered to be important factors on the photoinduced hydrophilicity. 相似文献
619.
Till J. B. Zähringer Julian A. Moghtader Maria-Sophie Bertrams Dr. Bibhisan Roy Masanori Uji Prof. Dr. Nobuhiro Yanai Prof. Dr. Christoph Kerzig 《Angewandte Chemie (International ed. in English)》2023,62(8):e202215340
Several energy-demanding photoreactions require harsh UV light from inefficient light sources. The conversion of low-energy visible light to high-energy singlet states via triplet-triplet annihilation upconversion (TTA-UC) could offer a solution for driving such reactions under mild conditions. We present the first annihilator with an emission maximum in the UVB region that, combined with an organic sensitizer, is suitable for blue-to-UVB upconversion. The annihilator singlet was successfully employed as an energy donor in subsequent FRET activations of aliphatic carbonyls. This hitherto unreported UC-FRET reaction sequence was directly monitored using laser spectroscopy and applied to mechanistic irradiation experiments demonstrating the feasibility of Norrish chemistry. Our results provide clear evidence for a novel blue light-driven substrate or solvent activation strategy, which is important in the context of developing more sustainable light-to-chemical energy conversion systems. 相似文献