全文获取类型
收费全文 | 1186篇 |
免费 | 31篇 |
国内免费 | 2篇 |
专业分类
化学 | 868篇 |
晶体学 | 19篇 |
力学 | 4篇 |
数学 | 64篇 |
物理学 | 205篇 |
无线电 | 59篇 |
出版年
2023年 | 4篇 |
2022年 | 15篇 |
2021年 | 25篇 |
2020年 | 10篇 |
2019年 | 20篇 |
2018年 | 22篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 21篇 |
2014年 | 36篇 |
2013年 | 58篇 |
2012年 | 74篇 |
2011年 | 91篇 |
2010年 | 47篇 |
2009年 | 43篇 |
2008年 | 63篇 |
2007年 | 76篇 |
2006年 | 62篇 |
2005年 | 73篇 |
2004年 | 71篇 |
2003年 | 72篇 |
2002年 | 57篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1997年 | 15篇 |
1996年 | 11篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 10篇 |
1986年 | 4篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1969年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有1219条查询结果,搜索用时 15 毫秒
71.
Tanguy Jousselin-Oba Masashi Mamada Karen Wright Jrome Marrot Chihaya Adachi Abderrahim Yassar Michel Frigoli 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2022,134(1):e202112794
We report the synthesis and optoelectronic properties of TIPS-peri-pentacenopentacene ( TIPS-PPP ), a vertical extension of TIPS-pentacene ( TIPS-PEN ) and a low-band-gap material with remarkable stability. We found the synthetic conditions to avoid the competition between 1,2- and 1,4-addition of lithium acetylide on the large aromatic dione. The high stability of TIPS-PPP is due to the peri-fusion which increases the aromaticity by generating two localized aromatic sextets that are flanked with 2 diene fragments, similar to two fused-anthracenes. Like TIPS-PEN , TIPS-PPP shows the archetypal 2D brickwall motif in crystals with a larger transfer integral and smaller reorganization energy. The high mobility of up to 1 cm2 V?1 s?1 was obtained in an organic field-effect transistor fabricated by a wet process. Also, TIPS-PPP was used as a near-infrared (NIR) emitter for NIR organic-light-emitting-diode devices resulting in a high external quantum efficiency at 800 nm. 相似文献
72.
Takashi Nagase Masashi Yoshikawa Saori Yamazaki Takashi Kobayashi Yoshiki Michiwaki Seiji Watase Mitsuru Watanabe Kimihiro Matsukawa Hiroyoshi Naito 《Journal of Polymer Science.Polymer Physics》2016,54(4):509-516
The effects of the addition of silica nanoparticles (SNPs) on wettability of regioregular poly(3‐hexylthiophene) (P3HT) organic semiconductor solutions on hydrophobic substrates and the carrier mobility in organic field‐effect transistors (OFETs) made of these films are investigated. The dewetting of films made from P3HT solutions on hydrophobic substrates modified with octadecyltrichlorosilane (ODTS) is markedly suppressed after the addition of SNPs with phenyl surfactants. This enables us to fabricate continuous P3HT/SNPs films with high crystallinity by the conventional spin‐coating technique, leading to higher mobility compared with P3HT FETs fabricated on non‐modified substrates. Moreover, the addition of SNPs with larger diameters compensates for the degradation of mobility associated with the increase in the concentration of SNPs. Solution‐processed P3HT/SNPs FETs on ODTS‐modified substrates exhibit a field‐effect mobility of 1.3 × 10?2 cm2 V?1 s?1, which is almost comparable to that of P3HT FETs without SNPs (2.1 × 10?2 cm2 V?1 s?1). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 509–516 相似文献
73.
Cooke MW Hanan GS Loiseau F Campagna S Watanabe M Tanaka Y 《Journal of the American Chemical Society》2007,129(34):10479-10488
Ru(II) polypyridine species have been assembled about dirhodium(II, II) tetracarboxylate cores. The complexes prepared have general formulas [{(terpy)Ru(La)}n{Rh2(CH3COO)4-n(CH3CN)2}]2n+ (a-type compounds: terpy = 2,2':6',2' '-terpyridine; La = 4'-(p-carboxyphenyl)-2,2':6',2' '-terpyridine; n = 1, 1a; n = 2, cis-2a and trans-2a-cis and trans refer to the arrangement of the Ru(II) species around the dirhodium core; n = 3, 3a), [{(Lb)Ru(La)}n{Rh2(CH3COO)4-n(CH3CN)2}]2n+ (b-type compounds: Lb = 6-phenyl-2,4-di(2-pyridyl)-s-triazine; n = 1, 1b; n = 2, an inseparable mixture of cis-2b and trans-2b; n = 3, 3b; n = 4, 4b), and [{(terpy)Ru(Lc)}{Rh2(CH3COO)3(CH3CN)2}]2+ (1c; Lc = 6-(p-carboxyphenyl)-2,4-di(2-pyridyl)-s-triazine). As model species, also the mononuclear [(terpy)Ru(La)]2+ (5a), [(La)Ru(Lb)]2+ (5b), and [(terpy)Ru(Lc)]2+ (5c) have been prepared. All of the complexes have been characterized by several techniques, including NMR and mass spectra, and the stability of the various species is discussed. The absorption spectra of all of the compounds are dominated by the Ru(II) polypyridine moieties, showing intense ligand-centered (LC) bands in the UV region and intense metal-to-ligand charge-transfer (MLCT) bands in the visible. The compounds exhibit several metal-centered oxidation and ligand-centered reduction processes, which have been assigned to specific subunits. Both absorption and redox data indicate a supramolecular nature of the assembled systems. Efficient energy transfer from the MLCT triplet state of the Ru-based components to the lowest-energy excited state of the dirhodium core takes place for the a-type compounds at 298 K in acetonitrile solution, whereas such a process is inefficient for the b-type and c-type species, which exhibit the typical MLCT emission. At 77 K in butyronitrile matrix, Ru-to-Rh2 energy transfer is partly efficient for both the a-type and the b-type compounds and is inefficient for 1c. The reasons for such behavior are discussed by taking into account arguments concerning the driving force and reorganization energy of the complexes. 相似文献
74.
75.
Masashi Nakagawa Tatsuo Iwasa Satoshi Kikkawa Toshifumi Takao Yasutsugu Shimonishi Motoyuki Tsuda 《Photochemistry and photobiology》1997,65(1):187-191
Abstract— We determined the structure and site of fatty acid incorporated in octopus rhodopsin using a combination of fluorescence label and enzymatic cleavage methods in conjunction with fast-atom bombardment (FAB) mass spectrometry. A single peptide containing two adjacent cysteines, Cys337 and Cys338, was successfully isolated using the fluorescence from a dye conjugated to Cys345. The FAB mass spectrometric analysis of the peptide (323phe-340 phe) revealed that two palmitoyl groups are linked to Cys337 and Cys338 via thioester bonds in octopus rhodopsin as in bovine rhodopsin. 相似文献
76.
Munehisa Yasuniwa Shinsuke Tsubakihara Masashi Yamaguchi 《Journal of Polymer Science.Polymer Physics》1997,35(4):535-543
Single crystal mat (SCM) samples of polyethylene (PE) were prepared from dilute solution of p-xylen, then they were annealed at pressures of 200 and 500 MPa. Lamellar thickness of the original and annealed SCM samples was measured by small-angle X-ray scattering method. Orientation of the molecular chain in those SCM samples was investigated by wide-angle X-ray diffraction pattern. From these X-ray measurements, annealing temperature dependence of the lamellar thickness, i.e., lamellar thickening, under high pressure was obtained. Melting process of the SCM samples was also investigated at 200 and 500 MPa by high pressure differential thermal analysis. Then correspondence between the lamellar thickening and the melting process was studied. The lamellar thickness increases markedly with approaching to the melting temperature of the orthorhombic crystal even in the high pressure region where the high pressure phase (hexagonal phase) appears. The annealing temperature dependence curve of the lamellar thickness at 200 MPa can be superimposed on the curve at 500 MPa by shifting the curve along the temperature scale by 47 K. Large scale lamellar thickening occurs in the orthorhombic crystal phase in the high pressure region. The formation process of extended-chain crystal is discussed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 535–543, 1997 相似文献
77.
Michael Andreas Tandiary Masashi Asano Taiki Hattori Satoshi Takehira Yoichi Masui Makoto Onaka 《Tetrahedron letters》2017,58(20):1925-1928
The solid acid, tin hydroxide-embedded montmorillonite, catalyzes the unprecedented alkylation of various silicon enolates with primary, secondary and tertiary benzylic alcohols as well as secondary allylic alcohols. The acid catalysis of Sn-Mont was not only higher than that of the other ion-exchanged montmorillonites (M-Mont; M = H, Ti, Fe and Al), but also higher than that of the typical homogeneous acid catalysts such as BF3·OEt2, TMSOTf and TfOH. 相似文献
78.
Yan Binggong Kang Lei Kotobuki Masashi He Linchun Liu Bin Jiang Kaiyong 《Journal of Solid State Electrochemistry》2021,25(2):527-534
Journal of Solid State Electrochemistry - We report effectiveness of dopants selected from group 13, such as B, Ga, and In, on the conductivity of Li1.5Al0.5Ge1.5(PO4)3 (LAGP) that is recognized as... 相似文献
79.
Wei Lu Panchao Yin Masashi Osa Weiyu Wang Nam‐Goo Kang Kunlun Hong Jimmy W. Mays 《Journal of Polymer Science.Polymer Physics》2017,55(20):1526-1531
Poly(1‐adamantyl acrylate) (PAdA) exhibits much higher glass transition and degradation temperatures than other polyacrylates. However, the quantitative evaluation of the stiffness of this polymer chain has not been reported previously. In this study, the dilute solution properties and conformational characteristics of PAdA were evaluated using viscometry and scattering techniques. The unperturbed dimensions of this polymer were evaluated using the Burchard–Stockmayer–Fixman extrapolation and the touched‐bead wormlike chain model. The PAdA chain has a comparable persistence length, diameter per bead and characteristic ratio to poly(methyl methacrylate) and polystyrene. All these results indicate that PAdA is less flexible than common polyacrylates. In addition, the second virial coefficients (A2) of PAdA in different solvents obtained by static light scattering were compared. Among the solvents investigated, tetrahydrofuran is a moderate solvent. Radius of gyration of a polymer sample in the various solvents ranged from 16.8 to 30.3 nm. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1526–1531 相似文献
80.