全文获取类型
收费全文 | 6456篇 |
免费 | 206篇 |
国内免费 | 26篇 |
专业分类
化学 | 5001篇 |
晶体学 | 79篇 |
力学 | 114篇 |
数学 | 505篇 |
物理学 | 989篇 |
出版年
2022年 | 57篇 |
2021年 | 56篇 |
2020年 | 77篇 |
2019年 | 96篇 |
2018年 | 57篇 |
2017年 | 44篇 |
2016年 | 112篇 |
2015年 | 109篇 |
2014年 | 146篇 |
2013年 | 311篇 |
2012年 | 353篇 |
2011年 | 388篇 |
2010年 | 214篇 |
2009年 | 204篇 |
2008年 | 397篇 |
2007年 | 418篇 |
2006年 | 430篇 |
2005年 | 362篇 |
2004年 | 324篇 |
2003年 | 297篇 |
2002年 | 271篇 |
2001年 | 89篇 |
2000年 | 79篇 |
1999年 | 78篇 |
1998年 | 55篇 |
1997年 | 87篇 |
1996年 | 88篇 |
1995年 | 46篇 |
1994年 | 62篇 |
1993年 | 55篇 |
1992年 | 49篇 |
1991年 | 52篇 |
1990年 | 34篇 |
1989年 | 32篇 |
1988年 | 44篇 |
1987年 | 42篇 |
1986年 | 39篇 |
1985年 | 85篇 |
1984年 | 91篇 |
1983年 | 41篇 |
1982年 | 86篇 |
1981年 | 80篇 |
1980年 | 75篇 |
1979年 | 74篇 |
1978年 | 69篇 |
1977年 | 55篇 |
1976年 | 64篇 |
1975年 | 42篇 |
1974年 | 44篇 |
1973年 | 64篇 |
排序方式: 共有6688条查询结果,搜索用时 15 毫秒
981.
Dr. Shun Dekura Prof. Hirokazu Kobayashi Dr. Kohei Kusada Prof. Hiroshi Kitagawa 《Chemphyschem》2019,20(10):1158-1176
One of the key issues for an upcoming hydrogen energy-based society is to develop highly efficient hydrogen-storage materials. Among the many hydrogen-storage materials reported, transition-metal hydrides can reversibly absorb and desorb hydrogen, and have thus attracted much interest from fundamental science to applications. In particular, the Pd−H system is a simple and classical metal-hydrogen system, providing a platform suitable for a thorough understanding of ways of controlling the hydrogen-storage properties of materials. By contrast, metal nanoparticles have been recently studied for hydrogen storage because of their unique properties and the degrees of freedom which cannot be observed in bulk, i. e., the size, shape, alloying, and surface coating. In this review, we overview the effects of such degrees of freedom on the hydrogen-storage properties of Pd-related nanomaterials, based on the fundamental science of bulk Pd−H. We shall show that sufficiently understanding the nature of the interaction between hydrogen and host materials enables us to control the hydrogen-storage properties though the electronic-structure control of materials. 相似文献
982.
Dongshuang Wu Kohei Kusada Tomokazu Yamamoto Takaaki Toriyama Syo Matsumura Ibrahima Gueye Okkyun Seo Jaemyung Kim Satoshi Hiroi Osami Sakata Shogo Kawaguchi Yoshiki Kubota Hiroshi Kitagawa 《Chemical science》2020,11(47):12731
We report the synthesis of high-entropy-alloy (HEA) nanoparticles (NPs) consisting of five platinum group metals (Ru, Rh, Pd, Ir and Pt) through a facile one-pot polyol process. We investigated the electronic structure of HEA NPs using hard X-ray photoelectron spectroscopy, which is the first direct observation of the electronic structure of HEA NPs. Significantly, the HEA NPs possessed a broad valence band spectrum without any obvious peaks. This implies that the HEA NPs have random atomic configurations leading to a variety of local electronic structures. We examined the hydrogen evolution reaction (HER) and observed a remarkably high HER activity on HEA NPs. At an overpotential of 25 mV, the turnover frequencies of HEA NPs were 9.5 and 7.8 times higher than those of a commercial Pt catalyst in 0.05 M H2SO4 and 1.0 M KOH electrolytes, respectively. Moreover, the HEA NPs showed almost no loss during a cycling test and were much more stable than the commercial Pt catalyst. Our findings on HEA NPs may provide a new paradigm for the design of catalysts.RuRhPdIrPt high-entropy-alloy nanoparticles with a broad and featureless valence band spectrum show high hydrogen evolution reaction activity. 相似文献
983.
984.
Masaki Kato Dr. Norihito Fukui Prof. Dr. Hiroshi Shinokubo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(2):e202103647
We report the synthesis and properties of indeno[1,2,3,4-pqra]perylene, which was prepared by the fusion of one anthracene unit with one naphthalene unit via three carbon-carbon bonds. The synthetic route through two-fold C−H arylation enabled not only the synthesis of unsubstituted indenoperylene, but also rapid access to its arylated derivatives on the gram scale. Indenoperylene is a medium-sized aromatic hydrocarbon with the composition C24H12 that is isomeric to coronene. Nevertheless, its absorption covers the entire visible region owing to its small HOMO-LUMO gap. Furthermore, indenoperylene exhibits high stability despite the absence of peripheral substituents. We propose that the unique electronic structure of indenoperylene originates from the coexistence of an electron-withdrawing subunit (benzoaceanthrylene) and an electron-donating subunit (perylene). The electronic properties of indenoperylene were modulated via post-functionalization through regioselective bromination. The current research demonstrates that indenoperylene is a promising candidate as a main skeleton for near-infrared-responsive and redox-active materials. 相似文献
985.
The effects of drying temperature on the structural evolution of alkoxy-derived silica gel prepared using various catalysts have been investigated. The dependence of specific surface area, Sg, reflecting the structure, on the temperature of drying was remarkable for a non-catalyzed xerogel. The effect of drying temperature on the Sg of an ammonia-catalyzed xerogel was also found but was not very large. The Sg of xerogels obtained by drying at 60°C was always higher by 50% than the gels dried at 30°C without regard to the aging temperature. The Sg of xerogels from HCl-catalyzed solution was of the order of several m2/g, however, the Sg of the aerogel obtained by hypercritical drying of the wet gel from a similar solution was about 800 m2/g. These phenomena were understood on the basis of SAXS measurements on both wet gels and aerogels. 相似文献
986.
Ikuma Shiota Arihiro Iwasaki Shimpei Sumimoto Hiroshi Tomoda Kiyotake Suenaga 《Tetrahedron letters》2018,59(13):1261-1263
A new polyketide with a cis-fused decalin ring scaffold, caldorin, was isolated from the marine cyanobacterium Caldora penicillata. The gross structure and relative configuration were elucidated by spectroscopic analyses. We also clarified that caldorin is a weak SOAT inhibitor and moderate osteoblast differentiation inhibitor. On the other hand, caldorin did not exhibit cytotoxicity against either HeLa or HL60 cells. 相似文献
987.
Kazuma Shimoda Takahiro Mitsuoka Kenta Ueda Hiroshi Suemune Go Hirai Mariko Aso 《Tetrahedron letters》2018,59(51):4528-4531
A dendritic bisphosphonate carrying three bisphosphonate (BP) units in close proximity was designed as a ligand to conjugate large therapeutic molecules for their bone selective delivery. The Bu3P-catalyzed conjugate addition of nitromethane to vinylidene bisphosphonate was effective to construct a quaternary carbon center carrying BP units. Owing to multivalent interactions, the dendritic bisphosphonate showed considerable affinity for the bone mineral hydroxyapatite even in the presence of a competitor, demonstrating potential as a bone targeting ligand. 相似文献
988.
The Electronic State of Hydrogen in the α Phase of the Hydrogen‐Storage Material PdH(D)x: Does a Chemical Bond Between Palladium and Hydrogen Exist?
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Shun Dekura Prof. Hirokazu Kobayashi Prof. Ryuichi Ikeda Prof. Mitsuhiko Maesato Haruka Yoshino Prof. Masaaki Ohba Prof. Takayoshi Ishimoto Dr. Shogo Kawaguchi Prof. Yoshiki Kubota Dr. Satoru Yoshioka Prof. Syo Matsumura Prof. Takeharu Sugiyama Prof. Hiroshi Kitagawa 《Angewandte Chemie (International ed. in English)》2018,57(31):9823-9827
The palladium–hydrogen system is one of the most famous hydrogen‐storage systems. Although there has been much research on β‐phase PdH(D)x, we comprehensively investigated the nature of the interaction between Pd and H(D) in α‐phase PdH(D)x (x<0.03 at 303 K), and revealed the existence of Pd?H(D) chemical bond for the first time, by various in situ experimental techniques and first‐principles theoretical calculations. The lattice expansion, magnetic susceptibility, and electrical resistivity all provide evidence. In situ solid‐state 1H and 2H NMR spectroscopy and first‐principles theoretical calculations revealed that a Pd?H(D) chemical bond exists in the α phase, but the bonding character of the Pd?H(D) bond in the α phase is quite different from that in the β phase; the nature of the Pd?H(D) bond in the α phase is a localized covalent bond whereas that in the β phase is a metallic bond. 相似文献
989.
Lithium‐Ion Endohedral Fullerene (Li+@C60) Dopants in Stable Perovskite Solar Cells Induce Instant Doping and Anti‐Oxidation
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Il Jeon Dr. Hiroshi Ueno Seungju Seo Dr. Kerttu Aitola Ryosuke Nishikubo Prof. Akinori Saeki Dr. Hiroshi Okada Prof. Gerrit Boschloo Prof. Shigeo Maruyama Prof. Yutaka Matsuo 《Angewandte Chemie (International ed. in English)》2018,57(17):4607-4611
Herein, we report use of [Li+@C60]TFSI? as a dopant for spiro‐MeOTAD in lead halide perovskite solar cells. This approach gave an air stability nearly 10‐fold that of conventional devices using Li+TFSI?. Such high stability is attributed to the hydrophobic nature of [Li+@C60]TFSI? repelling moisture and absorbing intruding oxygen, thereby protecting the perovskite device from degradation. Furthermore, [Li+@C60]TFSI? could oxidize spiro‐MeOTAD without the need for oxygen. The encapsulated devices exhibited outstanding air stability for more than 1000 h while illuminated under ambient conditions. 相似文献
990.
Mikihiro Ichikawa Shinya Yamamoto Chisato Ishihara Shuhei Nonobe Yasunao Hattori Koji Umezawa Hiroshi Fujii Hidefumi Makabe 《Tetrahedron》2018,74(27):3534-3542
Syntheses of epigallocatechin trimer, (epigallocatechin)2-epicatechin and (epigallocatechin)2-catechin were achieved. The key condensation to form the proanthocyanidin trimer derivatives was accomplished in a one-pot procedure using a dimeric epigallocatechin electrophile, which was prepared in situ by self-condensation of an epigallocatechin derivative, and an epigallocatechin, epicatechin, or catechin derivative as the nucleophile in the presence of a Lewis acid. The epigallocatechin monomer to trimer compounds containing a pyrogallol group significantly suppressed cell proliferation in PC-3 prostate cancer cells. 相似文献