全文获取类型
收费全文 | 1040篇 |
免费 | 342篇 |
国内免费 | 406篇 |
专业分类
化学 | 823篇 |
晶体学 | 24篇 |
力学 | 43篇 |
综合类 | 27篇 |
数学 | 224篇 |
物理学 | 647篇 |
出版年
2024年 | 6篇 |
2023年 | 10篇 |
2022年 | 48篇 |
2021年 | 29篇 |
2020年 | 41篇 |
2019年 | 34篇 |
2018年 | 34篇 |
2017年 | 50篇 |
2016年 | 34篇 |
2015年 | 33篇 |
2014年 | 62篇 |
2013年 | 96篇 |
2012年 | 93篇 |
2011年 | 109篇 |
2010年 | 97篇 |
2009年 | 110篇 |
2008年 | 103篇 |
2007年 | 97篇 |
2006年 | 103篇 |
2005年 | 78篇 |
2004年 | 72篇 |
2003年 | 64篇 |
2002年 | 56篇 |
2001年 | 51篇 |
2000年 | 53篇 |
1999年 | 35篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 23篇 |
1995年 | 30篇 |
1994年 | 15篇 |
1993年 | 18篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1788条查询结果,搜索用时 15 毫秒
121.
122.
123.
莫晓虎 张建勇 张清江 Achasov Mikhail 蔡啸 傅成栋 Harris Fred 刘倩 Muchnoi Nikolay 秦庆 屈化民 王贻芳 徐金强 张天保 《中国物理 C》2011,35(7):642-655
Understanding the radiation background at the north crossing point (NCP) in the tunnel of BEPCII is crucial for the performance safety of the High Purity Germanium (HPGe) detector, and in turn of great significance for long-term stable running of the energy measurement system. Therefore, as the first step, a NaI(Tl) detector is constructed to continuously measure the radiation level of photons as background for future experiments. Furthermore, gamma and neutron dosimeters are utilized to explore the radiation distribution in the vicinity of the NCP where the HPGe detector will be located. Synthesizing all obtained information, the shielding for neutron irradiation is studied based on model-dependent theoretical analysis. 相似文献
124.
The spatial structures of magnetic Co nanowire array embedded in anodic aluminium membranes were investigated by grazing incidence small angle X-ray scattering (GISAXS) and conventional small angle X-ray scattering (SAXS) techniques. Compared with SEM observation, the GISAXS and SAXS measurements can get more overall structural information in a large-area scale. In this study, the two-dimensional GISAXS pattern was well reconstructed by using the IsGISAXS program. The results demonstrate that the hexagonal lattice formed by the Co nanowires is distorted (a ≈ 105 nm, b ≈ 95 nm). These Co nanowires are isolated into many structure domains with different orientations with a size of about 2 μm. The SAXS results have also confirmed that the nanopore structures in the AAM can be retained after depositing Co nanowires although the Co nanowires can not completely but only just fill up the nanopores. These results are helpful for understanding the global structure of the Co nanowire array. 相似文献
125.
It has been conjectured that the relative phase between strong and electromagnetic amplitudes is universally -90° in charmonium decays. ψ′ decaying into a pseudoscalar pair provides a possibility to test this conjecture. However, the experimentally observed cross section for such a process is depicted by the two-fold integral, which takes into account the initial state radiative (ISR) correction and energy spread effect. Using the generalized linear regression approach, a complex energy-dependent factor is ... 相似文献
126.
127.
Guang-Hui Xu Jia-Qi Huang Qiang Zhang Meng-Qiang Zhao Fei Wei 《Applied Physics A: Materials Science & Processing》2011,103(2):403-411
Double-walled carbon nanotubes (DWCNTs) and two kinds of vertically aligned multi-walled carbon nanotubes were employed as
raw materials to fabricate transparent conductive films (TCFs). DWCNTs constructed the densest conductive network at the same
transmittance, and the corresponding TCFs showed the best performance (320 Ω/□ at 75.0% T). The ratio of dc conductivity to optical conductivity (σ
dc/σ
op) of the as-dispersed DWCNTs was 3.88. The as-obtained TCFs were dipped in HNO3 solution to improve their performances. Attributed to the removal of sodium dodecyl sulfate molecules, reduction of film
thickness, and doping with electron acceptors (such as oxygen), the surface resistance after HNO3 treatment decreased. The σ
dc/σ
op ratio of the DWCNTs was further increased to 5.24. 相似文献
128.
With the B3LYP calculation method of density functional theory(DFT)and the 6-31G* basis set,full optimization calculation was made for phenoxathiin10-oxide(PTO)and 135 polybromine phenoxathiin 10-oxides(PBPTOs)with the Gaussian 03 program and molar heat capacity in constant volume(CVθ)value of each molecule in the standard state was obtained.The relation between CVθ and the substitution position and number of bromine atom(NPBS)was studied,and the results indicated good correlation(R2 = 1.000)between CVθ and NPBS of PBPTO compounds.Based on the output file of Gaussian 03 program,molar heat capacity at constant pressure(Cp,m)of PBPTO compounds from 200 to 1,000 K was calculated with the statistical thermodynamics program,and the correlation equation between Cp,m and temperature(T,T-1 and T-2)was obtained with the least-squares method,and the correlation coefficient of the correlation equation(R2)was 1.000.In addition,based on the partition function of each molecule calculated by vibration analysis,the relative rate constant of formation of each molecule was calculated. 相似文献
129.
A New Capillary Electrophoresis Apparatus with Piezoelectric Ceramics High Voltage Source and Amperometric Detector 总被引:13,自引:0,他引:13
Zuan Guang CHENI Jin Yuan MO Xiao Yun YANG Li Shi WANG Xue Ting MEIZ Min Sheng ZHANGI 《中国化学快报》1999,(3)
IntroductionHighperformancecapiliar}'electrophoresis(HPCE)isanewanalyticaltechnology'rapidly'developedinrecentyears.Withtheadvantagesofsmallsample.highsensitivity,highresolution.rapidanalysisandverycheaprunning,ithasbeenappliedinchemistry'.lifescienc... 相似文献
130.
The symmetry orbital-symmetry orbital tensor method is applied to the evaluation of molecular integrals (one-electron and two-electron integrals) and the symmetry-orbital-tensor and self-consistent-field (SOT-SCF) calculations. A calculation scheme is proposed to simplify the evaluation of integrals and a key equation is derived to reduce the computation efforts in SCF iterations. According to the key equation, compared with the traditional SCF method, the computation efficiencies including CPU timing and external disk (or internal memory) requirement increase in the magnitude of the square of the order of a point group. The new SOT method is expected to be useful in the theoretical calculations of large molecular systems of high point group symmetries. 相似文献