全文获取类型
收费全文 | 145500篇 |
免费 | 23829篇 |
国内免费 | 16143篇 |
专业分类
化学 | 100010篇 |
晶体学 | 1680篇 |
力学 | 9571篇 |
综合类 | 1038篇 |
数学 | 17943篇 |
物理学 | 55230篇 |
出版年
2024年 | 130篇 |
2023年 | 2738篇 |
2022年 | 2963篇 |
2021年 | 4479篇 |
2020年 | 5645篇 |
2019年 | 5468篇 |
2018年 | 4662篇 |
2017年 | 4447篇 |
2016年 | 6797篇 |
2015年 | 6470篇 |
2014年 | 8074篇 |
2013年 | 10716篇 |
2012年 | 13011篇 |
2011年 | 13673篇 |
2010年 | 9287篇 |
2009年 | 8871篇 |
2008年 | 9553篇 |
2007年 | 8692篇 |
2006年 | 8023篇 |
2005年 | 6752篇 |
2004年 | 5264篇 |
2003年 | 4165篇 |
2002年 | 3898篇 |
2001年 | 3169篇 |
2000年 | 2707篇 |
1999年 | 3027篇 |
1998年 | 2641篇 |
1997年 | 2418篇 |
1996年 | 2616篇 |
1995年 | 2205篇 |
1994年 | 2101篇 |
1993年 | 1688篇 |
1992年 | 1548篇 |
1991年 | 1392篇 |
1990年 | 1153篇 |
1989年 | 817篇 |
1988年 | 704篇 |
1987年 | 579篇 |
1986年 | 533篇 |
1985年 | 493篇 |
1984年 | 384篇 |
1983年 | 288篇 |
1982年 | 225篇 |
1981年 | 174篇 |
1980年 | 128篇 |
1979年 | 79篇 |
1978年 | 59篇 |
1976年 | 65篇 |
1975年 | 66篇 |
1974年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Hao Lu Xiaodong Wang Hang Wang Andong Zhang Xinming Zheng Na Yu Zheng Tang Xinjun Xu Yahui Liu Ya-Nan Chen Zhishan Bo 《中国科学:化学(英文版)》2022,65(3):594-601
Three nonfused ring electron acceptors (NFREAs) TTC6,TT-C8T and TT-TC8 were purposefully designed and synthesized.The molecular geometry can be adjusted by the steric hindrance of lateral substituents.According to the DFT calculations,from TTC6 to TT-C8T and TT-TC8,planarity of the molecular backbone is gradually improved,accompanying with the enhancing of intramolecular charge transfer effect.As for TT-TC8,the two phenyl substituents are almost perpendicular to the molecular backbone,which endues the acceptor with good solubility and suppresses it to form over-aggregation.Multidirectional regular molecular orientation and closer molecular stacking are formed in TT-TC8 film.As a result,TT-TC8 based devices afford the highest PCE of 13.13%,which is much higher than that of TTC6 (4.41%) and TT-C8T (10.42%) and among the highest PCE values based on NFREAs. 相似文献
22.
Xu Yifan Zhang Hehe Ding Tangjing Tian Ruiqi Sun Dongmei Wang Ming-Sheng Zhou Xiaosi 《中国科学:化学(英文版)》2022,65(9):1807-1816
Science China Chemistry - Due to their enormous potential for large-scale energy storage, rechargeable potassium-ion batteries have been widely researched and developed. However, the drastic volume... 相似文献
23.
Theoretical and Mathematical Physics - We theoretically calculate general higher-order soliton solutions of the space-shifted parity–time-symmetric nonlocal multicomponent nonlinear... 相似文献
24.
Designs, Codes and Cryptography - The discrete logarithm problem arises from various areas, including counting the number of points of certain curves and diverse cryptographic schemes. The... 相似文献
25.
Science China Mathematics - In this paper, we obtain a necessary and sufficient condition for a U(n)-invariant complex Finsler metric F on domains in ?n to be strongly convex, which also... 相似文献
26.
In this paper,we investigate the non-autonomous Hamilton-Jacobi equation ■ where H is 1-periodic with respect to t and M is a compact Riemannian manifold without boundary.We obtain the viscosity solution denoted by T_(t_0)~tφ(x) and show T_(t_0)~tφ(x) converges uniformly to a time-periodic viscosity solution u~*(x,t) of ?_tu+H(t,x,?_xu,u)=0. 相似文献
27.
Fluid Dynamics - To predict the boundary layer transition on swept wings, experimental and numerical researches were conducted to obtained the accurate boundary layer transition front and to... 相似文献
28.
Applied Mathematics and Mechanics - A consequence of nonlinearities is a multi-harmonic response via a mono-harmonic excitation. A similar phenomenon also exists in random vibration. The power... 相似文献
29.
Luo Laizhen Wang Jiamei Zhang Lin Jing Yangping 《International Journal of Theoretical Physics》2021,60(7):2642-2652
International Journal of Theoretical Physics - In this paper, we will consider the exact calculation of differential entropy of induced random state ensemble by partial tracing a subsystem over... 相似文献
30.
First-principles study of the co-effect of carbon doping and oxygen vacancies in ZnO photocatalyst 下载免费PDF全文
Although tuning band structure of optoelectronic semiconductor-based materials by means of doping single defect is an important approach for potential photocatalysis application,C-doping or oxygen vacancy(Vo)as a single defect in ZnO still has limitations for photocatalytic activity.Meanwhile,the influence of co-existence of various defects in ZnO still lacks sufficient studies.Therefore,we investigate the photocatalytic properties of ZnOx C0.0625(x=0.9375,0.875,0.8125),confirming that the co-effect of various defects has a greater enhancement for photocatalytic activity driven by visible-light than the single defect in ZnO.To clarify the underlying mechanism of co-existence of various defects in ZnO,we perform systematically the electronic properties calculations using density functional theory.It is found that the coeffect of C-doping and Vo in ZnO can achieve a more controllable band gap than doping solely in ZnO.Moreover,the impact of the effective masses of ZnOxC0.0625(x=0.9375,0.875,0.8125)is also taken into account.In comparison with heavy Vo concentrations,the light Vo concentration(x=0.875)as the optimal component together with C-doping in ZnO,can significantly improve the visible-light absorption and benefit photocatalytic activity. 相似文献