全文获取类型
收费全文 | 287989篇 |
免费 | 5097篇 |
国内免费 | 2559篇 |
专业分类
化学 | 138058篇 |
晶体学 | 4141篇 |
力学 | 15621篇 |
综合类 | 71篇 |
数学 | 43790篇 |
物理学 | 93964篇 |
出版年
2021年 | 1526篇 |
2020年 | 1729篇 |
2019年 | 1704篇 |
2018年 | 10951篇 |
2017年 | 11867篇 |
2016年 | 7344篇 |
2015年 | 3564篇 |
2014年 | 3516篇 |
2013年 | 8933篇 |
2012年 | 12167篇 |
2011年 | 22200篇 |
2010年 | 13364篇 |
2009年 | 13450篇 |
2008年 | 19272篇 |
2007年 | 22771篇 |
2006年 | 8025篇 |
2005年 | 14609篇 |
2004年 | 10057篇 |
2003年 | 8983篇 |
2002年 | 6801篇 |
2001年 | 6503篇 |
2000年 | 5156篇 |
1999年 | 3831篇 |
1998年 | 2928篇 |
1997年 | 2863篇 |
1996年 | 3005篇 |
1995年 | 2634篇 |
1994年 | 2429篇 |
1993年 | 2245篇 |
1992年 | 2553篇 |
1991年 | 2519篇 |
1990年 | 2212篇 |
1989年 | 2176篇 |
1988年 | 2190篇 |
1987年 | 2106篇 |
1986年 | 1994篇 |
1985年 | 2900篇 |
1984年 | 2879篇 |
1983年 | 2321篇 |
1982年 | 2485篇 |
1981年 | 2371篇 |
1980年 | 2321篇 |
1979年 | 2277篇 |
1978年 | 2357篇 |
1977年 | 2228篇 |
1976年 | 2194篇 |
1975年 | 2168篇 |
1974年 | 2068篇 |
1973年 | 2190篇 |
1972年 | 1233篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
81.
82.
83.
84.
π-Extended molecules are key components for the development of materials science. In fact, polyaromatic structures are fundamental for the scientific and technological progress of fields such as organic electronics and bio-applications. Beneficial properties of π-extended structures are absorption in the visible region, often luminescence, high electron mobilities and stability. Common approaches to adjust the properties of polyaromatic structures to functional setups involve changes in shape and size at the molecular level. Recently, incorporating hetero-elements emerged as successful approach. In this regard, organophosphorus conjugated molecules are new materials holding great promise for potential applications. In this review, we comprehensively discuss the design/development of polyaromatic phosphorus materials and their applicability. We establish structure/property/applicability relationships to provide key guidelines for the engineering of newer, future applications. This article thus provides a source of information for the further development of this rapidly evolving field of research. 相似文献
85.
Cuixia Cui Yong Gao Dr. Jun Li Chao Yang Meng Liu Prof. Dr. Huile Jin Prof. Dr. Zhenhai Xia Prof. Dr. Liming Dai Prof. Dr. Yong Lei Prof. Dr. Jichang Wang Prof. Dr. Shun Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(20):8002-8007
Although tremendous efforts have been devoted to understanding the origin of boosted charge storage on heteroatom-doped carbons, none of the present studies has shown a whole landscape. Herein, by both experimental evidence and theoretical simulation, it is demonstrated that heteroatom doping not only results in a broadened operating voltage, but also successfully promotes the specific capacitance in aqueous supercapacitors. In particular, the electrolyte cations adsorbed on heteroatom-doped carbon can effectively inhibit hydrogen evolution reaction, a key step of water decomposition during the charging process, which broadens the voltage window of aqueous electrolytes even beyond the thermodynamic limit of water (1.23 V). Furthermore, the reduced adsorption energy of heteroatom-doped carbon consequently leads to more stored cations on the heteroatom-doped carbon surface, thus yielding a boosted charge storage performance. 相似文献
86.
87.
88.
89.
Experimental Mechanics - There have been relatively few studies on mechanical properties of nanomaterials under high strain rates, mainly due to the lack of capable nanomechanical testing devices.... 相似文献
90.
Immobilized Catalysts for Iridium‐Catalyzed Allylic Amination: Rate Enhancement by Immobilization
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Chandi C. Malakar Prof. Dr. Günter Helmchen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):7127-7134
The first immobilized catalyst for Ir‐catalyzed asymmetric allylic aminations is described. The catalyst is a cationic (π‐allyl)Ir complex bound by cation exchange to an anionic silica gel support. Preparation of the catalyst is facile, and the supported catalyst displayed considerably enhanced activity compared with the parent homogeneous catalyst. Up to 43 consecutive amination runs were possible in recycling experiments. 相似文献