全文获取类型
收费全文 | 245篇 |
免费 | 69篇 |
国内免费 | 43篇 |
专业分类
化学 | 89篇 |
晶体学 | 10篇 |
力学 | 35篇 |
综合类 | 5篇 |
数学 | 33篇 |
物理学 | 185篇 |
出版年
2024年 | 5篇 |
2023年 | 13篇 |
2022年 | 20篇 |
2021年 | 17篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 30篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 14篇 |
2014年 | 24篇 |
2013年 | 24篇 |
2012年 | 19篇 |
2011年 | 17篇 |
2010年 | 26篇 |
2009年 | 13篇 |
2008年 | 15篇 |
2007年 | 8篇 |
2006年 | 11篇 |
2005年 | 12篇 |
2004年 | 8篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
排序方式: 共有357条查询结果,搜索用时 15 毫秒
81.
82.
83.
为寻求单一源前驱体,采用密度泛函理论DFT-B3LYP方法系统研究新的第ⅢA主族叠氮簇合物的结构与性质关系.结果表明,簇合物(I2InN3)n(n=2~4)的优化构型均为由不同子体系的叠氮基α-N和In原子相连形成的环状结构,叠氮基以直线型存在.研究了几何参数随聚合度的变化趋势,并对计算获得的IR谱进行归属.能量和聚合焓均揭示簇合物的稳定性次序为3A>3B和4B>4C>4A>4D.簇合物(I2InN3)n(n=1~4)的热力学函数随温度升高和聚合度n增大而增加.热力学分析表明聚合反应在温度高达500 K均可自发进行. 相似文献
84.
A new heuristics model based on the Voronoi diagram is presented to simulate pedestrian dynamics with the noncrowded state, in which these mechanisms of preference demand evading and surpassing, microscopic anti-deadlock, and site-fine-tuning are considered. The preference demand describes the willingness determination of detouring or following other pedestrians. In the evading and surpassing mechanisms, in order to achieve a balance between avoiding conflicts and minimizing detour distances, a new pair of concepts: "allow-areas and denial-areas" are introduced to divide the feasible region for pedestrians detour behaviors, in which the direction and magnitude of detour velocity are determined.A microscopic anti-deadlock mechanism is inserted to avoid deadlock problem of the counter-directional pedestrian. A site-fine-tuning mechanism is introduced to describe the behavior of avoiding getting too close to the neighbors in pedestrian movement. The presented model is verified through multiple scenarios, including the uni-or bi-direction pedestrian flow in the corridor without obstacles, the uni-direction pedestrian flow in the corridor with obstacles, and the pedestrian evacuation from a room with single-exit. The simulation results show that the velocity–density relationship is consistent with empirical data. Some self-organizing phenomena, such as lanes formation and arching are observed in the simulation.When pedestrians detour an obstacle, the avoiding area before the obstacle and the unoccupied area after the obstacle can be observed. When pedestrians evacuate through a bottleneck without panic, the fan-shaped crowd can be found, which is consistent with the actual observation. It is also found that the behavior of following others in an orderly manner is more conducive to the improvement of the overall movement efficiency when the crowd moves in a limited space. 相似文献
85.
86.
Human blood coagulation factor XI (FXI) is a key enzyme in the amplification phase of blood coagulation cascade,and is recognized as an important target for anti-coagulant deve-lopment in recent years.We designed a new mutant form of FXIa catalytic domain rhFXI 370~607 (N73Q-N113Q-C123S),and report here the facile preparation,protein crystallization,and crystal structure of this protein.We highlight a few unique structural features of FXIa after comparison with the trypsin family serine proteases at sequence and structural levels.This work provides a foundation to develop new small molecular FXIa inhibitors with increased potency and specificity. 相似文献
87.
为了抑制平面带通滤波器的二次谐波,实现高温超导滤波器的小型化,本文提出了两种新型的准分形结构谐振器,并分别将其应用到微带滤波器的设计与仿真之中.第一种谐振器由希尔伯特分形结构改变而来,由于其相对紧凑度更高,并且保留希尔伯特分形结构的基本性质,因此仿真结果不仅具有更好的二次谐波抑制效果还有更小的体积优势.第二种谐振器由Minkowski分形结构改变而来,基于此谐振器设计了一款八阶带通滤波器,仿真及测试结果表明:基于此谐振器所设计滤波器与传统的微带滤波器相比,二次谐波被推迟了1.5GHz左右,并且体积减小约三分之一.结果证明两种滤波器均具有良好的二次谐波抑制效果和小型化的优势. 相似文献
88.
89.
90.
Formation of epitaxial Tl_2Ba_2Ca_2Cu_3O_(10) superconducting films by dc-magnetron sputtering and triple post-annealing method
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
For obtaining pure phase T12Ba2Ca2Cu3O10 (T1-2223) films with good superconducting properties, the growth technique is improved by dc magnetron sputtering and a triple post-annealing process. The triple post-annealing process comprises annealing twice in argon and once in oxygen at different temperatures. In the first low-temperature annealing phase in argon, T12Ba2CaCu2O8 (T1-2212) is obtained to effectively minimize evaporation in the next step. With the increase of temperature in the second annealing stage in argon, the previously prepared T1-2212 inter-phase is converted into T1-2223 phase. An additional annealing in oxygen is also adopted to improve the properties of T1-2223 films, each containing an optimal oxygen content value. The results of X-ray diffraction (XRD) θ-2θ scans, 09 scans and rotational φ scans show that each of the T1-2223 films has a high phase purity and an epitaxial structure. Smooth films are observed by scanning electron microscopy (SEM). The critical temperatures Tc of the films are measured to be about 120 K and the critical current densities Jc can reach 4.0 MA/cm2 at 77 K at self field. 相似文献