全文获取类型
收费全文 | 100350篇 |
免费 | 9547篇 |
国内免费 | 9216篇 |
专业分类
化学 | 32217篇 |
晶体学 | 393篇 |
力学 | 9434篇 |
综合类 | 1594篇 |
数学 | 42891篇 |
物理学 | 32584篇 |
出版年
2023年 | 857篇 |
2022年 | 1389篇 |
2021年 | 1739篇 |
2020年 | 2267篇 |
2019年 | 2435篇 |
2018年 | 2108篇 |
2017年 | 2354篇 |
2016年 | 2660篇 |
2015年 | 2458篇 |
2014年 | 3803篇 |
2013年 | 7064篇 |
2012年 | 4237篇 |
2011年 | 5050篇 |
2010年 | 4534篇 |
2009年 | 5847篇 |
2008年 | 6437篇 |
2007年 | 6564篇 |
2006年 | 5968篇 |
2005年 | 5381篇 |
2004年 | 4736篇 |
2003年 | 4712篇 |
2002年 | 4303篇 |
2001年 | 3514篇 |
2000年 | 3414篇 |
1999年 | 3123篇 |
1998年 | 2879篇 |
1997年 | 2369篇 |
1996年 | 2048篇 |
1995年 | 1817篇 |
1994年 | 1663篇 |
1993年 | 1340篇 |
1992年 | 1318篇 |
1991年 | 1055篇 |
1990年 | 867篇 |
1989年 | 715篇 |
1988年 | 656篇 |
1987年 | 536篇 |
1986年 | 478篇 |
1985年 | 545篇 |
1984年 | 530篇 |
1983年 | 259篇 |
1982年 | 438篇 |
1981年 | 481篇 |
1980年 | 380篇 |
1979年 | 379篇 |
1978年 | 281篇 |
1977年 | 253篇 |
1976年 | 200篇 |
1974年 | 132篇 |
1973年 | 147篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
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
3.
Despite significant advances in first-principles calculation methods, there is no single exchange-correlation functional which predicts the ground state of materials without an error yet. We investigated how accurately ground states of binary semiconductors are described using 16 exchange-correlation functionals (with or without van der Waals corrections). LDA, PBEsol, SCAN (with or without rVV10 correction), and PBE with D3 van der Waals correction (zero or Becke-Johnson damping) show good predicting power. The lattice constants of stable phases were slightly better described by SCAN, PBEsol, PBE+D3 (Becke-Johnson damping), and MS2. We also propose a set of functionals to double-check the stability of new materials based on the majority vote. 相似文献
4.
This paper is concerned with the Cauchy problem on the Boltzmann equation without angular cutoff assumption for hard potential in the whole space. When the initial data is a small perturbation of a global Maxwellian, the global existence of solution to this problem is proved in unweighted Sobolev spaces with . But if we want to obtain the optimal temporal decay estimates, we need to add the velocity weight function, in this case the global existence and the optimal temporal decay estimate of the Boltzmann equation are all established. Meanwhile, we further gain a more accurate energy estimate, which can guarantee the validity of the assumption in Chen et al. (0000). 相似文献
5.
6.
《Operations Research Letters》2022,50(2):137-144
In mine planning problems, cutoff grade optimization defines a threshold at every time period such that material above this value is processed, and the rest is considered waste. In orebodies with multiple minerals, which occur in practice, the natural extension is to consider a cutoff surface. We show that in two dimensions the optimal solution is a line, and in n dimensions it is a hyperplane. 相似文献
7.
8.
This paper infers from a generalized Picone identity the uniqueness of the stable positive solution for a class of semilinear equations of superlinear indefinite type, as well as the uniqueness and global attractivity of the coexistence state in two generalized diffusive prototypes of the symbiotic and competing species models of Lotka–Volterra. The optimality of these uniqueness theorems reveals the tremendous strength of the Picone identity. 相似文献
9.
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
10.
《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2021,38(5):1337-1371
In this paper we consider minimizers of the functional where is a bounded open set and where are the first k eigenvalues on Ω of an operator in divergence form with Dirichlet boundary condition and with Hölder continuous coefficients. We prove that the optimal sets have finite perimeter and that their free boundary is composed of a regular part, which is locally the graph of a -regular function, and a singular part, which is empty if , discrete if and of Hausdorff dimension at most if , for some . 相似文献