全文获取类型
收费全文 | 365篇 |
免费 | 17篇 |
专业分类
化学 | 283篇 |
晶体学 | 7篇 |
力学 | 1篇 |
数学 | 12篇 |
物理学 | 79篇 |
出版年
2023年 | 2篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 13篇 |
2012年 | 13篇 |
2011年 | 27篇 |
2010年 | 14篇 |
2009年 | 12篇 |
2008年 | 13篇 |
2007年 | 17篇 |
2006年 | 11篇 |
2005年 | 16篇 |
2004年 | 17篇 |
2003年 | 29篇 |
2002年 | 20篇 |
2001年 | 13篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 5篇 |
1971年 | 2篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有382条查询结果,搜索用时 62 毫秒
1.
Effects of polyethylene spacer length in polymeric electrolytes on gelation of ionic liquids and ionogel properties 下载免费PDF全文
Jun'ichi Nagasawa Sonoko Wakahara Hajime Matsumoto Hideyuki Kihara Masaru Yoshida 《Journal of polymer science. Part A, Polymer chemistry》2015,53(2):249-255
Polymer electrolytes containing N,N′-(trans-cyclohexane-1,4-diyl)dibenzamide linkages, polyethylene ((CH2)m, m = 2, 4, 10) spacers, and bis(trifluoromethanesulfonyl)amide (TFSA) or bis(fluorosulfonyl)amide (FSA) counteranions (polymer abbreviation: CDBAm•X; m = 2, 4, 10; X = TFSA, FSA) have been synthesized, adding to our previous report (m = 6). In addition, their ability to effect the gelation of six ionic liquids and the properties of the resulting ionogels have been examined. The polymers, except for CDBA10•TFSA, effect the gelation for all ionic liquids used in this study at fairly low concentrations (0.9–50 g/L). Ionogel ionic conductivity is not dependent on the spacer length, but does decrease slightly as increasing amounts of the gelatinizer are introduced. In contrast to ionic conductivity, the temperatures at which these ionogels transition into isotropic fluids is dependent on the spacer length; the gel composed of [EMI][FSA] and 100 g/L of CDBA6•FSA transforms at 120 °C, while the gel composed of [EMI][FSA] and 5 g/L of CDBA2•FSA does not transform into a sol even when temperatures become 155 °C. In brief, ionogel heat resistance can be improved by changing the spacer length of the polyelectrolyte. Finally, it has been determined using cyclic voltammetry that the potential window of the polyelectrolytes is particularly wide, ranging from −1.6 to 2.5 V. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 249–255 相似文献
2.
Kanna Adachi Tomoshi Yamada Hayate Ishizuka Mana Oki Shunsuke Tsunogae Noriko Shimada Osamu Chiba Tatsuya Orihara Prof. Dr. Masafumi Hidaka Prof. Dr. Takatsugu Hirokawa Dr. Minami Odagi Prof. Dr. Keiichi Konoki Prof. Dr. Mari Yotsu-Yamashita Prof. Dr. Kazuo Nagasawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(9):2025-2033
A novel series of C12-keto-type saxitoxin (STX) derivatives bearing an unusual nonhydrated form of the ketone at C12 has been synthesized, and their NaV-inhibitory activity has been evaluated in a cell-based assay as well as whole-cell patch-clamp recording. Among these compounds, 11-benzylidene STX ( 3 a ) showed potent inhibitory activity against neuroblastoma Neuro 2A in both cell-based and electrophysiological analyses, with EC50 and IC50 values of 8.5 and 30.7 nm , respectively. Interestingly, the compound showed potent inhibitory activity against tetrodotoxin-resistant subtype of NaV1.5, with an IC50 value of 94.1 nm . Derivatives 3 a – d and 3 f showed low recovery rates from NaV1.2 subtype (ca 45–79 %) compared to natural dcSTX ( 2 ), strongly suggesting an irreversible mode of interaction. We propose an interaction model for the C12-keto derivatives with NaV in which the enone moiety in the STX derivatives 3 works as Michael acceptor for the carboxylate of Asp1717. 相似文献
3.
Frontispiece: Entropy‐Driven 1,2‐Type Friedel–Crafts Reaction of Phenols with N‐tert‐Butoxycarbonyl Aldimines 下载免费PDF全文
4.
Total Synthesis of the 7,10‐Epimer of the Proposed Structure of Amphidinolide N,Part II: Synthesis of C17–C29 Subunit and Completion of the Synthesis 下载免费PDF全文
Dr. Koji Ochiai Dr. Sankar Kuppusamy Yusuke Yasui Kenji Harada Dr. Nishant R. Gupta Dr. Yohei Takahashi Prof. Dr. Takaaki Kubota Prof. Dr. Jun'ichi Kobayashi Prof. Dr. Yujiro Hayashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3287-3291
The total synthesis of 7,10‐epimer of the proposed structure of amphidinolide N was accomplished. The requisite chiral C17–C29 subunit was assembled stereoselectively via Keck allylation, Shi epoxidation, diastereoselective 1,3‐reduction, and a later oxidative synthesis of the THF framework. The C1–C13 and C17–C29 subunits were successfully coupled using a Enders RAMP “linchpin” as the C14–C16 three carbon unit, thereby controlling the chirality at C14 and C16. The labile allyl epoxy moiety was successfully constructed by Grieco–Nishizawa olefination at a final stage of the synthesis. 相似文献
5.
Dr. Yoshihiro Sohtome Bongki Shin Natsuko Horitsugi Prof. Dr. Keiichi Noguchi Prof. Dr. Kazuo Nagasawa 《化学:亚洲杂志》2011,6(9):2463-2470
Herein, we present details of our conformationally flexible, 1,3‐diamine‐tethered guanidine/bisthiourea organocatalysts for chemo‐, regio‐, and enantioselective 1,4‐type Friedel–Crafts reactions of phenols. These organocatalysts show a unique stereo‐discrimination governed by the differential activation entropy (ΔΔS≠), rather than by the differential activation enthalpy (ΔΔH≠). Extensive kinetic analyses using Eyring plots for a series of guanidine/bisthiourea organocatalysts revealed the key structural motif in the catalysts associated with a large magnitude of differential activation entropy (ΔΔS≠). A plausible guanidine–thiourea cooperative mechanism for the enantioselective Friedel–Crafts reaction is proposed. 相似文献
6.
Yusuke Sasano Shota Nagasawa Mai Yamazaki Dr. Masatoshi Shibuya Prof. Dr. Jaiwook Park Prof. Dr. Yoshiharu Iwabuchi 《Angewandte Chemie (International ed. in English)》2014,53(12):3236-3240
The direct oxidation of unprotected amino alcohols to their corresponding amino carbonyl compounds has often posed serious challenges in organic synthesis and has constrained chemists to adopting an indirect route, such as a protection/deprotection strategy, to attain their goal. Described herein is a highly chemoselective aerobic oxidation of unprotected amino alcohols to their amino carbonyl compounds in which 2‐azaadamantane N‐oxyl (AZADO)/copper catalysis is used. The catalytic system developed leads to the alcohol‐selective oxidation of various unprotected amino alcohols, carrying a primary, secondary, or tertiary amino group, in good to high yield at ambient temperature with exposure to air, thus offering flexibility in the synthesis of nitrogen‐containing compounds. 相似文献
7.
Mapping Platinum Species in Polymer Electrolyte Fuel Cells by Spatially Resolved XAFS Techniques 下载免费PDF全文
Dr. Shinobu Takao Dr. Oki Sekizawa Dr. Shin‐ichi Nagamatsu Dr. Takuma Kaneko Dr. Takashi Yamamoto Dr. Gabor Samjeské Dr. Kotaro Higashi Dr. Kensaku Nagasawa Dr. Takuya Tsuji Dr. Motohiro Suzuki Dr. Naomi Kawamura Dr. Masaichiro Mizumaki Prof. Dr. Tomoya Uruga Prof. Dr. Yasuhiro Iwasawa 《Angewandte Chemie (International ed. in English)》2014,53(51):14110-14114
There is limited information on the mechanism for platinum oxidation and dissolution in Pt/C cathode catalyst layers of polymer electrolyte fuel cells (PEFCs) under the operating conditions though these issues should be uncovered for the development of next‐generation PEFCs. Pt species in Pt/C cathode catalyst layers are mapped by a XAFS (X‐ray absorption fine structure) method and by a quick‐XAFS(QXAFS) method. Information on the site‐preferential oxidation and leaching of Pt cathode nanoparticles around the cathode boundary and the micro‐crack in degraded PEFCs is provided, which is relevant to the origin and mechanism of PEFC degradation. 相似文献
8.
Y. Tsuchiya Y. Nakajima T. Tamegai S. Nagasawa M. Hidaka 《Physica C: Superconductivity and its Applications》2011,471(21-22):808-811
We have observed flux penetrations into square superconducting networks of Nb with various thicknesses and hole-shapes by using magneto-optical imaging method. The penetrated pattern does not depend on the thickness and extends along diagonal direction when the samples have smaller area in the intersection of networks. We have also observed similar superconducting networks with and without small holes at the intersection. The small holes at the intersection do not work as a promoter for the diagonal flux penetration though the parallel flux penetration becomes weak. We discuss possible origins of these anomalous anisotropic flux penetrations. 相似文献
9.
Naonobu Tanaka Rei Momose Azusa Takahashi-Nakaguchi Tohru Gonoi Jane Fromont Jun'ichi Kobayashi 《Tetrahedron》2014
Six new indole alkaloids, hyrtimomines F–K (1–6), were isolated from Okinawan marine sponges Hyrtios spp. The structures of 1–6 were elucidated on the basis of spectroscopic analysis. Hyrtimomine F (1) is a structurally unique bisindole alkaloid possessing an α-keto-?-caprolactam ring, while hyrtimomine G (2) is a symmetrical bisindole alkaloid. Hyrtimomines H–K (3–6) are indole alkaloids possessing β-carboline skeleton with an imidazolium unit. Antimicrobial activities of hyrtimomines F–K (1–6) were evaluated. 相似文献