全文获取类型
收费全文 | 148392篇 |
免费 | 33331篇 |
国内免费 | 24485篇 |
专业分类
化学 | 99611篇 |
晶体学 | 1877篇 |
力学 | 9456篇 |
综合类 | 662篇 |
数学 | 18393篇 |
物理学 | 76209篇 |
出版年
2024年 | 457篇 |
2023年 | 2164篇 |
2022年 | 2485篇 |
2021年 | 3245篇 |
2020年 | 4055篇 |
2019年 | 4385篇 |
2018年 | 3828篇 |
2017年 | 4302篇 |
2016年 | 5638篇 |
2015年 | 5746篇 |
2014年 | 6346篇 |
2013年 | 9278篇 |
2012年 | 10851篇 |
2011年 | 12324篇 |
2010年 | 13564篇 |
2009年 | 13546篇 |
2008年 | 7905篇 |
2007年 | 6985篇 |
2006年 | 6339篇 |
2005年 | 6065篇 |
2004年 | 6159篇 |
2003年 | 4961篇 |
2002年 | 4640篇 |
2001年 | 4647篇 |
2000年 | 3657篇 |
1999年 | 4101篇 |
1998年 | 3413篇 |
1997年 | 3085篇 |
1996年 | 3387篇 |
1995年 | 3706篇 |
1994年 | 3644篇 |
1993年 | 3543篇 |
1992年 | 3057篇 |
1991年 | 2637篇 |
1990年 | 2269篇 |
1989年 | 2200篇 |
1988年 | 2090篇 |
1987年 | 1364篇 |
1986年 | 1425篇 |
1985年 | 1042篇 |
1984年 | 1089篇 |
1983年 | 486篇 |
1982年 | 969篇 |
1981年 | 786篇 |
1980年 | 805篇 |
1979年 | 547篇 |
1978年 | 537篇 |
1977年 | 651篇 |
1976年 | 1062篇 |
1972年 | 549篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results. 相似文献
12.
This study is to numerically test the interfacial instability of ferrofluid flow under the presence of a vacuum magnetic field. The ferrofluid parabolized stability equations(PSEs) are derived from the ferrofluid stability equations and the Rosensweig equations, and the characteristic values of the ferrofluid PSEs are given to describe the ellipticity of ferrofluid flow. Three numerical models representing specific cases considering with/without a vacuum magnetic field or viscosity are created to mathematically examine the interfacial instability by the computation of characteristic values. Numerical investigation shows strong dependence of the basic characteristic of ferrofluid Rayleigh-Taylor instability(RTI) on viscosity of ferrofluid and independence of the vacuum magnetic field.For the shock wave striking helium bubble, the magnetic field is not able to trigger the symmetry breaking of bubble but change the speed of the bubble movement. In the process of droplet formation from a submerged orifice, the collision between the droplet and the liquid surface causes symmetry breaking. Both the viscosity and the magnetic field exacerbate symmetry breaking. The computational results agree with the published experimental results. 相似文献
13.
Journal of Optimization Theory and Applications - We distinguish two kinds of piecewise linear functions and provide an interesting representation for a piecewise linear function between two normed... 相似文献
14.
Yi-Tong Xu Tian-Yang Zhang Zheng Li Xiang-Nan Liu Yuan-Cheng Zhu Wei-Wei Zhao Hong-Yuan Chen Jing-Juan Xu 《Electroanalysis》2022,34(6):947-955
Photoelectrochemical (PEC) cytosensors, a combination of the PEC process and the living-cell assay, have emerged as a powerful tool in the analytical and biological science. This mini review provides a brief introduction of this arena and summaries the key steps about the development of PEC cytosensors with representative examples, followed by future prospects based on our own opinions. 相似文献
15.
Nonlinear Dynamics - This paper proposes an optimal parameter design of control scheme for mechanical systems by adopting the Stackelberg game theory. The goal of the control is to drive the... 相似文献
16.
Xu Mengtao Li Changyou Sun Yang Yang Tianzhi Zhang Hongzhuang Liu Zhendong Liu Haiyang Li Zhenyuan Zhang Yimin 《Nonlinear dynamics》2021,105(4):3061-3092
Nonlinear Dynamics - Investigation of the dynamic characteristics of linear guideway is essential for enhancing structural performance of machine tools. However, few mechanical models are... 相似文献
17.
Journal of Visualization - The increasing availability of spatiotemporal data provides unprecedented opportunities for understanding the structure of an urban area in terms of people’s... 相似文献
18.
Mathematical Programming - In the general equilibrium with incomplete asset markets (GEI) model, the excess demand functions are typically not continuous at the prices for which the assets have... 相似文献
19.
International Journal of Theoretical Physics - The Majorana representation, which provides an intuitive way to represent the quantum state by stars on the Bloch sphere, has drawn considerable... 相似文献
20.
低维硅锗材料是制备纳米电子器件的重要候选材料,是研发高效率、低能耗和超高速新一代纳米电子器件的基础材料之一,有着潜在的应用价值。采用密度泛函紧束缚方法分别对厚度相同、宽度在0.272 nm~0.554 nm之间的硅纳米线和宽度在0.283 nm~0.567 nm之间的锗纳米线的原子排布和电荷分布进行了计算研究。硅、锗纳米线宽度的改变使原子排布,纳米线的原子间键长和键角发生明显改变。纳米线表层结构的改变对各层内的电荷分布产生重要影响。纳米线中各原子的电荷转移量与该原子在表层内的位置相关。纳米线的尺寸和表层内原子排列结构对体系的稳定性产生重要影响。 相似文献