全文获取类型
收费全文 | 58124篇 |
免费 | 13481篇 |
国内免费 | 4894篇 |
专业分类
化学 | 57450篇 |
晶体学 | 581篇 |
力学 | 1864篇 |
综合类 | 277篇 |
数学 | 4999篇 |
物理学 | 11328篇 |
出版年
2024年 | 36篇 |
2023年 | 531篇 |
2022年 | 604篇 |
2021年 | 946篇 |
2020年 | 2217篇 |
2019年 | 3455篇 |
2018年 | 1795篇 |
2017年 | 1430篇 |
2016年 | 4391篇 |
2015年 | 4574篇 |
2014年 | 4680篇 |
2013年 | 5721篇 |
2012年 | 5061篇 |
2011年 | 4261篇 |
2010年 | 4386篇 |
2009年 | 4256篇 |
2008年 | 3867篇 |
2007年 | 3147篇 |
2006年 | 2747篇 |
2005年 | 2732篇 |
2004年 | 2407篇 |
2003年 | 2234篇 |
2002年 | 3031篇 |
2001年 | 2230篇 |
2000年 | 1861篇 |
1999年 | 903篇 |
1998年 | 427篇 |
1997年 | 400篇 |
1996年 | 360篇 |
1995年 | 272篇 |
1994年 | 238篇 |
1993年 | 198篇 |
1992年 | 173篇 |
1991年 | 171篇 |
1990年 | 155篇 |
1989年 | 90篇 |
1988年 | 71篇 |
1987年 | 54篇 |
1986年 | 68篇 |
1985年 | 53篇 |
1984年 | 40篇 |
1983年 | 32篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 17篇 |
1979年 | 12篇 |
1978年 | 22篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1974年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 843 毫秒
1.
2.
Hua Saixiang Zhu Huichao Wang Xiao Wu Mingyuan Wu Qingyun Liu Jiuyi Yang Jianjun Zhang Jianan 《Cellulose (London, England)》2022,29(13):7465-7475
Cellulose - Ultraviolet (UV) protective cotton fabric is a convenient and reliable way to protect human body from sunlight. Herein, a polymerizable UV-absorber,... 相似文献
3.
Wang Rong Li Xu Zhou Youshi Cao Shuxuan Xu Honghao Han Wenjuan Zhang Yuxia Liu Junhai 《Journal of Russian Laser Research》2022,43(4):476-481
Journal of Russian Laser Research - We demonstrate a passively-mode-locked Pr3+: LuLiF4 laser operated at the 604 nm orange wave-length, using monolayer graphene as a saturable absorber. The... 相似文献
4.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications. 相似文献
5.
Interactions of the vector breathers for the coupled Hirota system with $$4\times 4$$ 4 × 4 Lax pair
Nonlinear Dynamics - In this paper, we investigate the interactions of the vector breathers for the coupled Hirota system with $$4\times 4$$ Lax pair. Firstly, we give the first-order breather... 相似文献
6.
Ruirui Xu Kun Wang Haoying Liu Prof. Dr. Weijun Tang Dr. Huaming Sun Prof. Dr. Dong Xue Prof. Dr. Jianliang Xiao Prof. Dr. Chao Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22143-22148
A ruthenium-catalyzed formal anti-Markovnikov hydroamination of allylic alcohols for the synthesis of chiral γ-amino alcohols is presented. Proceeding via an asymmetric hydrogen-borrowing process, the catalysis allows racemic secondary allylic alcohols to react with various amines, affording enantiomerically enriched chiral γ-amino alcohols with broad substrate scope and excellent enantioselectivities (68 examples, up to >99 % ee). 相似文献
7.
8.
Chemical versus Electrochemical Synthesis of Carbon Nano‐onion/Polypyrrole Composites for Supercapacitor Electrodes 下载免费PDF全文
Olena Mykhailiv Monika Imierska Martyna Petelczyc Prof. Dr. Luis Echegoyen Dr. Marta E. Plonska‐Brzezinska 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5783-5793
The development of high‐surface‐area carbon electrodes with a defined pore size distribution and the incorporation of pseudo‐active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano‐onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission‐ and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g?1 for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g?1 for the CNOs/Ppy bilayer (electrochemical deposition). 相似文献
9.
Dr. Sabin Llona‐Minguez Dr. Matthieu Desroses Artin Ghassemian Dr. Sylvain A. Jacques Dr. Lars Eriksson Rebecka Isacksson Tobias Koolmeister Dr. Pål Stenmark Dr. Martin Scobie Prof. Thomas Helleday 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(20):7394-7398
A two‐step synthesis of structurally diverse pyrrole‐containing bicyclic systems is reported. ortho‐Nitro‐haloarenes coupled with vinylic N‐methyliminodiacetic acid (MIDA) boronates generate ortho‐vinyl‐nitroarenes, which undergo a “metal‐free” nitrene insertion, resulting in a new pyrrole ring. This novel synthetic approach has a wide substrate tolerance and it is applicable in the preparation of more complex “drug‐like” molecules. Interestingly, an ortho‐nitro‐allylarene derivative furnished a cyclic β‐aminophosphonate motif. 相似文献
10.
Interactions of Pt‐ttpy with G‐Quadruplexes Originating from Promoter Region of the c‐myc Gene Deciphered by NMR and Gel Electrophoresis Analysis 下载免费PDF全文