全文获取类型
收费全文 | 17960篇 |
免费 | 1980篇 |
国内免费 | 1681篇 |
专业分类
化学 | 3680篇 |
晶体学 | 215篇 |
力学 | 2170篇 |
综合类 | 308篇 |
数学 | 12077篇 |
物理学 | 3171篇 |
出版年
2024年 | 26篇 |
2023年 | 170篇 |
2022年 | 179篇 |
2021年 | 302篇 |
2020年 | 463篇 |
2019年 | 428篇 |
2018年 | 432篇 |
2017年 | 541篇 |
2016年 | 562篇 |
2015年 | 420篇 |
2014年 | 722篇 |
2013年 | 1340篇 |
2012年 | 914篇 |
2011年 | 1067篇 |
2010年 | 992篇 |
2009年 | 1093篇 |
2008年 | 1192篇 |
2007年 | 1288篇 |
2006年 | 1110篇 |
2005年 | 1000篇 |
2004年 | 900篇 |
2003年 | 936篇 |
2002年 | 791篇 |
2001年 | 655篇 |
2000年 | 555篇 |
1999年 | 507篇 |
1998年 | 448篇 |
1997年 | 375篇 |
1996年 | 312篇 |
1995年 | 299篇 |
1994年 | 249篇 |
1993年 | 179篇 |
1992年 | 172篇 |
1991年 | 140篇 |
1990年 | 120篇 |
1989年 | 83篇 |
1988年 | 80篇 |
1987年 | 63篇 |
1986年 | 69篇 |
1985年 | 71篇 |
1984年 | 60篇 |
1983年 | 30篇 |
1982年 | 66篇 |
1981年 | 49篇 |
1980年 | 45篇 |
1979年 | 35篇 |
1978年 | 22篇 |
1977年 | 16篇 |
1976年 | 14篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
We establish the global well-posedness of a strong solution to the 3D tropical climate model with damping. We prove that there exists the global and unique solution for α, β, γ satisfying one of the following three conditions: (1) ; (2) ; (3) . 相似文献
22.
Shilin Jiang Dr. Yalan Liu Dr. Lin Wang Prof. Zhifang Chai Prof. Wei-Qun Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201145
The coordination chemistry of f-block elements (lanthanide and actinide) in molten salts has become a resounding topic in view of its great importance to the research and development (R&D) of molten salt reactors and pyroprocessing. In this Review article, a general overview of the coordination chemistry of f-block elements in molten salts is provided including past achievements and recent advances. Particular emphases are placed on the oxidation state, speciation, and solution structure of f-block metal ions in molten salts, as well as their relationships with the salt composition. Furthermore, this review briefly discusses the spectroscopic and theoretical methods that complement each other in revealing the coordination properties. 相似文献
23.
《Mendeleev Communications》2022,32(6):742-744
A solution of a histone-like protein from Spiroplasma melliferum (HUSpm) was examined by small-angle X-ray scattering (SAXS). The experimental SAXS curve was compared with those calculated for the HUSpm structures from the PDB databank obtained by both X-ray diffraction analysis and nuclear magnetic resonance spectroscopy. The model of the HUSpm structure in solution, which best agrees with the experimental SAXS data, has a shorter distance between the centers of mass of the HUSpm monomers compared to the crystal structure, indicating that the HUSpm monomers can be located closer to each other in solution than in the crystalline state. 相似文献
24.
25.
26.
Tomoyuki Nakatsuka 《Mathematische Nachrichten》2021,294(1):98-117
We study the existence of a time‐periodic solution with pointwise decay properties to the Navier–Stokes equation in the whole space. We show that if the time‐periodic external force is sufficiently small in an appropriate sense, then there exists a time‐periodic solution of the Navier–Stokes equation such that and uniformly in as . Our solution decays faster than the time‐periodic Stokes fundamental solution and the faster decay of its spatial derivatives of higher order is also described. 相似文献
27.
Effect of external electric field on the terahertz transmission characteristics of electrolyte solutions 下载免费PDF全文
Jia-Hui Wang 《中国物理 B》2021,30(11):110204-110204
We fabricated a microfluidic chip with simple structure and good sealing performance, and studied the influence of the electric field on THz absorption intensity of liquid samples treated at different times by using THz time domain spectroscopy system. The tested liquids were deionised water and CuSO4, CuCl2, NaHCO3, Na2CO3 and NaCl solutions. The transmission intensity of the THz wave increases as the standing time of the electrolyte solution in the electric field increases. The applied electric field alters the dipole moment of water molecules in the electrolyte solution, which affects the vibration and rotation of the whole water molecules, breaks the hydrogen bonds in the water, increases the number of single water molecules and leads to the enhancement of the THz transmission spectrum. 相似文献
28.
This paper is our attempt, on the basis of physical theory, to bring more clarification on the question “What is life?” formulated in the well-known book of Schrödinger in 1944. According to Schrödinger, the main distinguishing feature of a biosystem’s functioning is the ability to preserve its order structure or, in mathematical terms, to prevent increasing of entropy. However, Schrödinger’s analysis shows that the classical theory is not able to adequately describe the order-stability in a biosystem. Schrödinger also appealed to the ambiguous notion of negative entropy. We apply quantum theory. As is well-known, behaviour of the quantum von Neumann entropy crucially differs from behaviour of classical entropy. We consider a complex biosystem S composed of many subsystems, say proteins, cells, or neural networks in the brain, that is, We study the following problem: whether the compound system S can maintain “global order” in the situation of an increase of local disorder and if S can preserve the low entropy while other increase their entropies (may be essentially). We show that the entropy of a system as a whole can be constant, while the entropies of its parts rising. For classical systems, this is impossible, because the entropy of S cannot be less than the entropy of its subsystem . And if a subsystems’s entropy increases, then a system’s entropy should also increase, by at least the same amount. However, within the quantum information theory, the answer is positive. The significant role is played by the entanglement of a subsystems’ states. In the absence of entanglement, the increasing of local disorder implies an increasing disorder in the compound system S (as in the classical regime). In this note, we proceed within a quantum-like approach to mathematical modeling of information processing by biosystems—respecting the quantum laws need not be based on genuine quantum physical processes in biosystems. Recently, such modeling found numerous applications in molecular biology, genetics, evolution theory, cognition, psychology and decision making. The quantum-like model of order stability can be applied not only in biology, but also in social science and artificial intelligence. 相似文献
29.
《Mathematical Methods in the Applied Sciences》2018,41(9):3294-3306
In this article, we consider the asymptotic behavior of the classical solution to the 3‐dimensional Vlasov‐Poisson plasma interacting repulsively with N point charges. The large time behavior in terms of diameters of its velocity‐spatial supports is improved to O(t2/3+ϵ) for any ϵ>0. 相似文献
30.
The flow behavior in non-parallel walls is an important factor of any physical model including cavity flow and canals, which is applicable for diverging/converging channel. The present communication explains that the flow of the hybrid nanomaterial subjected to the convergent/divergent channel has non-parallel walls. It is assumed that the hybrid nanomaterial movement is in the porous region. A Darcy-Forchheimer medium of porosity is considered to interpret the porosity features. A useful similarity function is adopted to get the strong ordinary coupled equations. Numerical solutions are achieved through the Runge-Kutta-Fehlberg(RKF) fourth-fifth order method, and they are validated with the existing results. Physical nature of the involving constraints is reported with the help of plots. It is explored that the velocity of divergent channel decreases, and convergent channel enhances for the higher solid volume faction. Further, the presence of inertia coefficient and porosity parameter amplifies the velocity at the wall. 相似文献