全文获取类型
收费全文 | 12464篇 |
免费 | 3298篇 |
国内免费 | 1913篇 |
专业分类
化学 | 4738篇 |
晶体学 | 71篇 |
力学 | 1295篇 |
综合类 | 442篇 |
数学 | 1896篇 |
物理学 | 9233篇 |
出版年
2024年 | 171篇 |
2023年 | 530篇 |
2022年 | 606篇 |
2021年 | 723篇 |
2020年 | 443篇 |
2019年 | 551篇 |
2018年 | 302篇 |
2017年 | 544篇 |
2016年 | 538篇 |
2015年 | 641篇 |
2014年 | 1116篇 |
2013年 | 787篇 |
2012年 | 782篇 |
2011年 | 837篇 |
2010年 | 820篇 |
2009年 | 774篇 |
2008年 | 984篇 |
2007年 | 734篇 |
2006年 | 736篇 |
2005年 | 655篇 |
2004年 | 670篇 |
2003年 | 638篇 |
2002年 | 441篇 |
2001年 | 394篇 |
2000年 | 335篇 |
1999年 | 260篇 |
1998年 | 221篇 |
1997年 | 233篇 |
1996年 | 193篇 |
1995年 | 186篇 |
1994年 | 141篇 |
1993年 | 141篇 |
1992年 | 128篇 |
1991年 | 103篇 |
1990年 | 107篇 |
1989年 | 88篇 |
1988年 | 35篇 |
1987年 | 26篇 |
1986年 | 18篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1980年 | 3篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
Energy spectrum of multi-radiation of X-rays in a low energy Mather-type plasma focus device
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)
The multi-radiation of X-rays was investigated with special attention to their energy spectrum in a Mather-type plasma focus device (operated with argon gas). The analysis is based on the effect of anomalous resistances. To study the energy spectrum, a four-channel diode X-ray spectrometer was used along with a special set of filters. The filters were suitable for detection of medium range X-rays as well as hard X-rays with energy exceeding 30 keV. The results indicate that the anomalous resistivity effect during the post pinch phase may cause multi-radiation of X-rays with a total duration of 300 ± 50 ns. The significant contribution of Cu-Kα was due to the medium range X-rays, nonetheless, hard X-rays with energies greater than 15 keV also participate in the process. The total emitted X-ray energy in the forms of Cu-K and Cu-K/3 was around 0.14 ± 0.02 (J/Sr) and 0.04 ±0.01 (J/Sr), respectively. The total energy of the emitted hard X-ray (〉 15 keV) was around 0.12± 0.02 (J/Sr). 相似文献
912.
913.
914.
An investigation of the optical properties of a hydrogenic donor in spherical parabolic quantum dots has been performed by using the matrix diagonalization method. The optical absorption coefficient between the ground (L = 0) and the first excited state (L = 1) have been examined based on the computed energies and wave functions. The results are presented as a function of the incident photon energy for the different values of the confinement strength. These results show the effects of the quantum size and the impurity on the optical absorption coefficient of a donor impurity quantum dot. 相似文献
915.
The photoproduction of K+ mesons from the nucleon provides important constraints on the nucleon excitation spectrum and at threshold energies challenges effective field theories based on chiral perturbation in the strange quark sector. Preliminary cross-section measurements for γ(P, K+)A are presented at an unprecedented beam energy resolution. The data was collected at the MAMI-C facility in Mainz using the Crystal Ball Detector. A new method of K+ detection was used in which the K+ is tagged from its weak decay products in the detector crystals. This technique has application with other calorimeters at present and future hadron facilities. 相似文献
916.
对ITER中子通量监测器(NFM)建立了简化模型并进行了计算分析。利用MCNP程序模拟计算了具有不同慢化剂材料,类型的NFM的探测效率能量响应和时间响应,通过对结果的分析确定了不同NFM上所使用的慢化剂种类及其用量,同时给出了对ITER NFM的初步物理认识。 相似文献
917.
918.
对含数值的判断题,先根据物理规律列出方程,然后把具体数值代入方程,用计算的结果可以做出精确的判断.一般情况下,对于含数值的判断题用计算的方法是行之有效的.但在有的情况下,所给的数值之间具有倍数关系,是巧合,还是隐藏"天机"?笔者发现,若能根据数值之间的倍数关系,采用定性 相似文献
919.
分析此题是2008年杭州市第一次教学质量检测卷的最后一道填空题,同学们答题正确率很低.考后问大家是如何思考这个问题的,绝大多数同学不理解题目的要求与已有的知识之间的联系,没有充分挖掘向量a。 相似文献
920.
Power dissipation characteristics of great power and super high speed semiconductor switch
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)
The power dissipation characteristics of pulsed power switch reversely switched dynistors (RSDs) are investigated in this paper. According to the expressions of voltage on RSD, derived from the plasma bipolar drift model and the RLC circuit equations of RSD main loop, the simulation waveforms of current and voltage on RSD are acquired through iterative calculation by using the fourth order Runge-Kutta method, then the curve of transient power on RSD versus time is obtained. The result shows that the total dissipation on RSD is trivial compared with the pulse discharge energy and the commutation dissipation can be nearly ignored compared with the quasi-static dissipation. These characteristics can make the repetitive frequency of RSD increase largely. The experimental results prove the validity of simulation calculations. The influence factors on power dissipation are discussed. The power dissipation increases with the increase of the peak current and the n-base width and with the decrease of n-base doping concentration. In order to keep a low power dissipation, it is suggested that the n-base width should be smaller than 320μm when doping concentration is 1.0×10^14cm^-3 while the doping concentration should be higher than 5.8×10^13cm^-3 when n-base width is 270μm. 相似文献