全文获取类型
收费全文 | 195681篇 |
免费 | 4364篇 |
国内免费 | 3154篇 |
专业分类
化学 | 99794篇 |
晶体学 | 2580篇 |
力学 | 8233篇 |
综合类 | 156篇 |
数学 | 19013篇 |
物理学 | 57793篇 |
综合类 | 15630篇 |
出版年
2022年 | 1408篇 |
2021年 | 1614篇 |
2020年 | 1728篇 |
2019年 | 1686篇 |
2018年 | 1654篇 |
2017年 | 1731篇 |
2016年 | 3032篇 |
2015年 | 2746篇 |
2014年 | 3423篇 |
2013年 | 8889篇 |
2012年 | 7566篇 |
2011年 | 9392篇 |
2010年 | 5880篇 |
2009年 | 5986篇 |
2008年 | 8570篇 |
2007年 | 8406篇 |
2006年 | 8092篇 |
2005年 | 7574篇 |
2004年 | 6759篇 |
2003年 | 5791篇 |
2002年 | 5882篇 |
2001年 | 7077篇 |
2000年 | 5438篇 |
1999年 | 4170篇 |
1998年 | 2965篇 |
1997年 | 2923篇 |
1996年 | 2859篇 |
1995年 | 2505篇 |
1994年 | 2422篇 |
1993年 | 2209篇 |
1992年 | 2707篇 |
1991年 | 2659篇 |
1990年 | 2351篇 |
1989年 | 2277篇 |
1988年 | 2266篇 |
1987年 | 2223篇 |
1986年 | 2095篇 |
1985年 | 2988篇 |
1984年 | 2900篇 |
1983年 | 2326篇 |
1982年 | 2463篇 |
1981年 | 2341篇 |
1980年 | 2304篇 |
1979年 | 2336篇 |
1978年 | 2376篇 |
1977年 | 2316篇 |
1976年 | 2237篇 |
1975年 | 2247篇 |
1974年 | 2215篇 |
1973年 | 2203篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Dr. Feifan Wang Jie Tian Dr. Mengzhu Li Dr. Weizhen Li Dr. Lifang Chen Xiaozhi Liu Dr. Jian Li Aidaer Muhetaer Prof. Dr. Qi Li Prof. Dr. Yuan Wang Prof. Dr. Lin Gu Prof. Dr. Ding Ma Prof. Dr. Dongsheng Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(21):8280-8286
Fully utilizing solar energy for catalysis requires the integration of conversion mechanisms and therefore delicate design of catalyst structures and active species. Herein, a MOF crystal engineering method was developed to controllably synthesize a copper–ceria catalyst with well-dispersed photoactive Cu-[O]-Ce species. Using the preferential oxidation of CO as a model reaction, the catalyst showed remarkably efficient and stable photoactivated catalysis, which found practical application in feed gas treatment for fuel cell gas supply. The coexistence of photochemistry and thermochemistry effects contributes to the high efficiency. Our results demonstrate a catalyst design approach with atomic or molecular precision and a combinatorial photoactivation strategy for solar energy conversion. 相似文献
63.
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
64.
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
65.
66.
Chunhong Wang Qi Cui Zhixin Zhang Prof. Zhu-Jun Yao Dr. Shaozhong Wang Prof. Zhi-Xiang Yu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9821-9826
1,3-Azaprotio transfer of propargylic α-ketocarboxylate oximes, a new type of alkynyl oximes featuring an ester tether, has been explored by taking advantage of gold catalysis. The incorporation of an oxygen atom to the chain of alkynyl oximes led to the formation of two different oxa-cyclic nitrones. It was found that internal alkynyl oximes with an E-configuration deliver five-membered nitrones, whereas terminal alkynyl oximes with an E-configuration afford six-membered nitrones. DFT calculations on four possible pathways supported a stepwise formation of C−N and C−H bonds, in which a 1,3-acyloxy-migration competes with the 1,3-azaprotio-transfer, especially in the case of internal alkynyl oximes. The relative nucleophilic properties of oxygen in the carbonyl group and the nitrogen in the oxime, the electronic effects of alkynes, and the influence of the ring system have been investigated computationally. 相似文献
67.
68.
L. Resse L.G.S. Oliveira C.I.L. de Araujo A.R. Pereira R.L. Silva 《Physics letters. A》2019,383(14):1655-1659
In this work, we have used the MuMax3 software to simulate devices consisting of a ferromagnetic thin film placed over a heavy metal thin film. The devices are two interconnected partial-disks where a Néel domain wall is formed in the disks junction. In our simulations we investigate devices with disk radius nm and different distance d between the disks centers (from nm to nm). By applying strong sinusoidal external magnetic fields, we find a mechanism able to create, annihilate and even manipulate a skyrmion in each side of the device. This mechanism is discussed in terms of interactions between skyrmion and domain wall. The Néel domain wall formed in the center of the device interacts with the Néel skyrmion, leading to a process of transporting a skyrmion from one disk to the other periodically. Our results have relevance for potential applications in spintronics such as logical devices. 相似文献
69.
70.
Dong Liangwei Qi Wei Peng Ping Wang Linxue Zhou Hui Huang Changming 《Nonlinear dynamics》2020,102(1):303-310
Nonlinear Dynamics - We address the nonlinear dynamics of binary Bose-Einstein condensates with mutually symmetric spinor components trapped in an optical lattice. The interaction between the... 相似文献