全文获取类型
收费全文 | 309677篇 |
免费 | 3528篇 |
国内免费 | 640篇 |
专业分类
化学 | 169123篇 |
晶体学 | 4364篇 |
力学 | 13254篇 |
综合类 | 9篇 |
数学 | 36372篇 |
物理学 | 90723篇 |
出版年
2020年 | 2662篇 |
2019年 | 2871篇 |
2018年 | 4028篇 |
2017年 | 3835篇 |
2016年 | 5849篇 |
2015年 | 3896篇 |
2014年 | 5512篇 |
2013年 | 13219篇 |
2012年 | 11023篇 |
2011年 | 12965篇 |
2010年 | 8883篇 |
2009年 | 8325篇 |
2008年 | 11892篇 |
2007年 | 12085篇 |
2006年 | 11152篇 |
2005年 | 10266篇 |
2004年 | 9303篇 |
2003年 | 8244篇 |
2002年 | 7970篇 |
2001年 | 8025篇 |
2000年 | 6257篇 |
1999年 | 4795篇 |
1998年 | 4185篇 |
1997年 | 4145篇 |
1996年 | 3987篇 |
1995年 | 3585篇 |
1994年 | 3768篇 |
1993年 | 3497篇 |
1992年 | 3980篇 |
1991年 | 3929篇 |
1990年 | 3855篇 |
1989年 | 3695篇 |
1988年 | 3760篇 |
1987年 | 3647篇 |
1986年 | 3441篇 |
1985年 | 4650篇 |
1984年 | 4893篇 |
1983年 | 4047篇 |
1982年 | 4252篇 |
1981年 | 4163篇 |
1980年 | 4108篇 |
1979年 | 4084篇 |
1978年 | 4372篇 |
1977年 | 4269篇 |
1976年 | 4364篇 |
1975年 | 4030篇 |
1974年 | 4081篇 |
1973年 | 4235篇 |
1972年 | 2930篇 |
1971年 | 2441篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
Robert G. W. Anderson 《Ambix》2015,62(4):333-344
Following colonisation of South America by the Spanish, many new naturally occurring substances were sent to Europe. One of these was the silvery, unreactive metal, platinum, discovered in New Grenada in the mid-eighteenth century. It was often found in granular form, associated with gold, and the challenge to chemists was to refine it, produce it as wire or sheet, and determine its chemical properties. This interested the professor of chemistry at the University of Edinburgh, Joseph Black, who was able to obtain samples from London-based Spanish contacts, particularly Ignacio Luzuriaga. This paper examines how Black transmitted his knowledge of the metal to large numbers of students attending his annual course. 相似文献
24.
25.
26.
Manjumol K. A. Jayasankar M. Vidya K. Mohamed A. Peer Nair Balagopal N. Warrier K. G. K. 《Journal of Sol-Gel Science and Technology》2015,74(1):161-167
Journal of Sol-Gel Science and Technology - High temperature stable brookite rich titanium dioxide of average crystallite size 20&;nbsp;nm has been prepared by a novel aqueous sol–gel... 相似文献
27.
Synthesis of partially fluorinated poly(arylene ether sulfone) multiblock copolymers bearing perfluorosulfonic functions 下载免费PDF全文
Luca Assumma Cristina Iojoiu Régis Mercier Sandrine Lyonnard Huu Dat Nguyen Emilie Planes 《Journal of polymer science. Part A, Polymer chemistry》2015,53(16):1941-1956
Partially fluorinated poly(arylene ether sulfone) multiblock copolymers bearing perfluorosulfonic functions (ps‐PES‐FPES), with ionic exchange capacity (IEC) ranging between 0.9 and 1.5 meq H+/g, are synthesized by regioselective bromination of partially fluorinated poly(arylene ether sulfone) multiblock copolymers (PES‐FPES), followed by Ullman coupling reaction with lithium 1,1,2,2‐tetrafluoro‐2‐(1,1,2,2‐tetrafluoro‐2‐iodoethoxy)ethanesulfonate. The PES‐FPES are prepared by aromatic nucleophilic substitution reaction by an original approach, that is, “one pot two reactions synthesis.” The chemical structures of polymers are analyzed by 1H and 19F NMR spectroscopy. The resulted ionomers present two distinct glass transitions and α relaxations revealing phase separation between the hydrophilic and the hydrophobic domains. The phase separation is observed at much lower block lengths of ps‐PES‐FPES as compared with the literature. AFM and SANS observations supported the phase separation, the hydrophilic domains are well dispersed but the connectivity to each other depends on the ps‐PES block lengths. The thermomechanical behavior, the water up‐take, and the conductivity of the ps‐PES‐FPES membranes are compared with those of Nafion 117® and randomly functionalized polysulfone (ps‐PES). Conductivities close or higher to those of Nafion 117® are obtained. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1941–1956 相似文献
28.
Saleh Z. M. Nasser H. Özkol E. Günöven M. Abak K. Canli S. Bek A. Turan R. 《Journal of nanoparticle research》2015,17(10):1-12
Journal of Nanoparticle Research - Plasmonic interfaces consisting of silver nanoparticles of different sizes (50–100&;nbsp;nm) have been processed by the self-assembled dewetting... 相似文献
29.
E. V. Shadrina O. N. Malinkina T. G. Khonina A. B. Shipovskaya V. I. Fomina E. Yu. Larchenko N. A. Popova I. G. Zyryanova L. P. Larionov 《Russian Chemical Bulletin》2015,64(7):1633-1639
The biomimetic sol—gel synthesis of silicon—chitosan-containing glycerohydrogels was carried out using silicon tetraglycerolate as a precursor. It was found that chitosan accelerates gel formation in weakly acidic media. In more acidic media, the kinetics of the process changes according to the curve with a maximum, which can be attributed to different mechanisms of silanol condensation before and after the isoelectric point. The investigated silicon—chitosan-containing glycerohydrogels exhibit antibacterial, anti-inflammatory, and wound healing activity. The synthesized hybrid glycerohydrogels are promising materials for biomedical applications. 相似文献
30.