全文获取类型
收费全文 | 18817篇 |
免费 | 4363篇 |
国内免费 | 2091篇 |
专业分类
化学 | 5604篇 |
晶体学 | 202篇 |
力学 | 2333篇 |
综合类 | 264篇 |
数学 | 3440篇 |
物理学 | 13428篇 |
出版年
2024年 | 48篇 |
2023年 | 245篇 |
2022年 | 538篇 |
2021年 | 710篇 |
2020年 | 846篇 |
2019年 | 627篇 |
2018年 | 595篇 |
2017年 | 723篇 |
2016年 | 889篇 |
2015年 | 774篇 |
2014年 | 1139篇 |
2013年 | 1453篇 |
2012年 | 1185篇 |
2011年 | 1288篇 |
2010年 | 1125篇 |
2009年 | 1203篇 |
2008年 | 1251篇 |
2007年 | 1171篇 |
2006年 | 1142篇 |
2005年 | 1002篇 |
2004年 | 1001篇 |
2003年 | 870篇 |
2002年 | 780篇 |
2001年 | 638篇 |
2000年 | 610篇 |
1999年 | 543篇 |
1998年 | 443篇 |
1997年 | 370篇 |
1996年 | 333篇 |
1995年 | 253篇 |
1994年 | 210篇 |
1993年 | 167篇 |
1992年 | 145篇 |
1991年 | 132篇 |
1990年 | 110篇 |
1989年 | 118篇 |
1988年 | 79篇 |
1987年 | 71篇 |
1986年 | 73篇 |
1985年 | 77篇 |
1984年 | 57篇 |
1983年 | 31篇 |
1982年 | 47篇 |
1981年 | 35篇 |
1980年 | 30篇 |
1979年 | 27篇 |
1978年 | 17篇 |
1977年 | 15篇 |
1976年 | 8篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 30 毫秒
1.
2.
4.
5.
Dr. Yong-Sheng Wei Dr. Liming Sun Miao Wang Dr. Jinhua Hong Dr. Lianli Zou Hongwen Liu Dr. Yu Wang Dr. Mei Zhang Dr. Zheng Liu Prof. Yinwei Li Prof. Satoshi Horike Prof. Kazu Suenaga Prof. Qiang Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16147-16156
Understanding the thermal aggregation behavior of metal atoms is important for the synthesis of supported metal clusters. Here, derived from a metal–organic framework encapsulating a trinuclear FeIII2FeII complex (denoted as Fe3) within the channels, a well-defined nitrogen-doped carbon layer is fabricated as an ideal support for stabilizing the generated iron nanoclusters. Atomic replacement of FeII by other metal(II) ions (e.g., ZnII/CoII) via synthesizing isostructural trinuclear-complex precursors (Fe2Zn/Fe2Co), namely the “heteroatom modulator approach”, is inhibiting the aggregation of Fe atoms toward nanoclusters with formation of a stable iron dimer in an optimal metal–nitrogen moiety, clearly identified by direct transmission electron microscopy and X-ray absorption fine structure analysis. The supported iron dimer, serving as cooperative metal–metal site, acts as efficient oxygen evolution catalyst. Our findings offer an atomic insight to guide the future design of ultrasmall metal clusters bearing outstanding catalytic capabilities. 相似文献
6.
G. Peruginelli 《代数通讯》2018,46(11):4724-4738
We classify the maximal subrings of the ring of n×n matrices over a finite field, and show that these subrings may be divided into three types. We also describe all of the maximal subrings of a finite semisimple ring, and categorize them into two classes. As an application of these results, we calculate the covering number of a finite semisimple ring. 相似文献
7.
Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have been deemed as clean and sustainable strategies to solve the energy crisis and environmental problems. Various catalysts have been developed to promote the process of HER and OER. Among them, two-dimensional covalent organic frameworks (2D COFs) have received great attention due to their diverse and designable structure. In this minireview, we mainly summarize the diverse linkages of 2D COFs and strategies for enhancing the catalytic performance of 2D COFs for HER and OER, such as introducing active building blocks, metal ions and tailored linkages. Furthermore, a brief outlook for the development directions of COFs in the field of HER and OER is provided, expecting to stimulate new opportunities in future research. 相似文献
8.
In 1976 S. Hawking claimed that “Because part of the information about the state of the system is lost down the hole, the final situation is represented by a density matrix rather than a pure quantum state”. 1 This was the starting point of the popular “black hole (BH) information paradox”. 相似文献
9.
Knowledge of the vibrational properties of nanoparticles is of fundamental interest since it is a signature of their morphology, and it can be utilized to characterize their physical properties. In addition, the vibration characteristics of the nanoparticles coupled with surrounding media and subjected to magnetic field are of recent interest. This paper develops an analytical approach to study the radial breathing-mode frequency of elastically confined spherical nanoparticles subjected to magnetic field. Based on Maxwell's equations, the nonlocal differential equation of radial motion is derived in terms of radial displacement and Lorentz's force. Bessel functions are used to obtain a frequency equation. The model is justified by a good agreement between the results given by the present model and available experimental and atomic simulation data. Furthermore, the model is used to elucidate the effect of nanoparticle size, the magnetic field and the stiffness of the elastic medium on the radial breathing-mode frequencies of several nanoparticles. Our results reveal that the effects of the magnetic field and the elastic medium are significant for nanoparticle with small size. 相似文献
10.
就标准厚度卡片在霍尔传感器的定标方面的应用作了有益的探讨。在纵向测量微小长度时,霍尔片处于磁场边缘位置,其对磁场的梯度更大,即灵敏度更高,且靠中心位置的线性更好。 相似文献