全文获取类型
收费全文 | 35237篇 |
免费 | 5404篇 |
国内免费 | 3770篇 |
专业分类
化学 | 24647篇 |
晶体学 | 364篇 |
力学 | 2246篇 |
综合类 | 363篇 |
数学 | 4145篇 |
物理学 | 12646篇 |
出版年
2024年 | 42篇 |
2023年 | 696篇 |
2022年 | 704篇 |
2021年 | 1030篇 |
2020年 | 1385篇 |
2019年 | 1340篇 |
2018年 | 1144篇 |
2017年 | 1032篇 |
2016年 | 1540篇 |
2015年 | 1537篇 |
2014年 | 1881篇 |
2013年 | 2465篇 |
2012年 | 3182篇 |
2011年 | 3348篇 |
2010年 | 2155篇 |
2009年 | 2029篇 |
2008年 | 2239篇 |
2007年 | 2100篇 |
2006年 | 1865篇 |
2005年 | 1558篇 |
2004年 | 1205篇 |
2003年 | 1027篇 |
2002年 | 1017篇 |
2001年 | 777篇 |
2000年 | 652篇 |
1999年 | 738篇 |
1998年 | 639篇 |
1997年 | 603篇 |
1996年 | 682篇 |
1995年 | 570篇 |
1994年 | 510篇 |
1993年 | 418篇 |
1992年 | 400篇 |
1991年 | 347篇 |
1990年 | 285篇 |
1989年 | 222篇 |
1988年 | 167篇 |
1987年 | 145篇 |
1986年 | 130篇 |
1985年 | 132篇 |
1984年 | 94篇 |
1983年 | 66篇 |
1982年 | 43篇 |
1981年 | 39篇 |
1979年 | 17篇 |
1978年 | 19篇 |
1977年 | 23篇 |
1976年 | 20篇 |
1975年 | 28篇 |
1974年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Zhong Weizhou Zhang Zexiong Chen Xiaowei Wei Qiang Chen Gang Huang Xicheng 《Acta Mechanica Sinica》2021,37(7):1136-1151
Acta Mechanica Sinica - Multi-scale finite element method is adopted to simulate wood compression behavior under axial and transverse loading. Representative volume elements (RVE) of wood... 相似文献
2.
3.
Pu Lin Peifu Luo Yating Guo Honglong Qiu Min Wang Guoming Huang 《Particle & Particle Systems Characterization》2021,38(10):2100113
In this study, the synthesis of TaN nanosheets and their application in theranostic agents is reported. After coating polyethylene glycol (PEG) on the TaN nanosheets, the as-synthesized PEG-modified TaN nanosheets (TaN-PEG) show good stability and biocompatibility. Because of their high absorbance in the near-IR region, TaN-PEG can be utilized as photoacoustic imaging contrast agents for tumor imaging. Moreover, TaN-PEG has significant photothermal conversion performance, exhibiting effective laser-induced tumor ablation capability. The TaN-PEG possessing excellent photoacoustic contrast effect and photothermal properties thus have great promise in theranostic applications, especially imaging-guided cancer treatment. 相似文献
4.
Journal of Visualization - Forecast calibration methods based on historical similar atmospheric state are effective means weather forecast accuracy. Conventional approaches search similar forecasts... 相似文献
5.
The row iterative method is popular in solving the large‐scale ill‐posed problems due to its simplicity and efficiency. In this work we consider the randomized row iterative (RRI) method to tackle this issue. First, we present the semiconvergence analysis of RRI method for the overdetermined and inconsistent system, and derive upper bounds for the noise error propagation in the iteration vectors. To achieve a least squares solution, we then propose an extended version of the RRI (ERRI) method, which in fact can converge in expectation to the solution of the overdetermined or underdetermined, consistent or inconsistent systems. Finally, some numerical examples are given to demonstrate the convergence behaviors of the RRI and ERRI methods for these types of linear system. 相似文献
6.
International Journal of Theoretical Physics - The thermal entanglement in the two-qubit Ising spin chain in the presence of the Dzyaloshinski-Moriya(DM) anisotropic antisymmetric interaction in a... 相似文献
7.
Nonlinear Dynamics - The modal truncation is usually used in the dynamic response analysis of flexible multibody systems, in which, appropriate selection of modal shapes is very critical to achieve... 相似文献
8.
单匝线圈在辐向磁场中的受力情况,很多教师都用纯数学方法(微元法)推导出其有效长度为线圈周长.文章用音频电流通过方形线圈,依次增加磁铁的个数让学生感觉音量的变化,并进一步合理外推出同样的结论.不仅能让学生体会基于实验合理外推这一科学的研究方法,还能让学生对扬声器的工作原理有清晰的认识. 相似文献
9.
Rational Design of Two-Dimensional Magnetic Chromium Borides Based on First-Principles Calculation 下载免费PDF全文
Two-dimensional(2D) magnetic materials have been experimentally recognized recently,however,the Curie temperatures(TC) of known 2D systems are quite low.Generally,magnetic systems can be seen as constituent magnetic elements providing spins and the non-magnetic elements providing frameworks to host the magnetic elements.Short bond lengths between the magnetic and non-magnetic elements would be beneficial for strong magnetic interactions and thus high TC.Based on this,we propose to combine the magnetic element Cr and the non-magnetic element boron to design novel 2D magnetic systems.Using our self-developed software package IM2 ODE,we design a series of chromium-boride based 2D magnetic materials.Nine stable magnetic systems are identified.Among them,we find that CrB4-Ⅰ,CrB4-Ⅱ and CrBs-Ⅰ with common structural units [CrB8] are ferromagnetic metals with estimated TC of 270 K,120 K and 110 K,respectively.On the other hand,five CrB3 phases with structural units [Cr2B12] are antiferromagnetic metals.Additionally,we also find one antiferromagnetic semiconductor CrB2-Ⅰ.Our work may open new directions for identifying 2D magnetic systems with high TC. 相似文献
10.