首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   11181篇
  免费   1661篇
  国内免费   1154篇
化学   6473篇
晶体学   92篇
力学   488篇
综合类   49篇
数学   1026篇
物理学   3289篇
无线电   2579篇
  2024年   41篇
  2023年   259篇
  2022年   345篇
  2021年   414篇
  2020年   406篇
  2019年   401篇
  2018年   345篇
  2017年   341篇
  2016年   462篇
  2015年   528篇
  2014年   606篇
  2013年   840篇
  2012年   954篇
  2011年   921篇
  2010年   689篇
  2009年   656篇
  2008年   724篇
  2007年   587篇
  2006年   605篇
  2005年   490篇
  2004年   413篇
  2003年   335篇
  2002年   334篇
  2001年   255篇
  2000年   187篇
  1999年   219篇
  1998年   196篇
  1997年   206篇
  1996年   191篇
  1995年   143篇
  1994年   152篇
  1993年   106篇
  1992年   80篇
  1991年   68篇
  1990年   66篇
  1989年   48篇
  1988年   38篇
  1987年   24篇
  1986年   34篇
  1985年   30篇
  1984年   24篇
  1983年   20篇
  1982年   11篇
  1981年   17篇
  1980年   17篇
  1979年   14篇
  1978年   22篇
  1977年   11篇
  1976年   14篇
  1974年   12篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
101.
The samples of Eu1–x Sr x FeO3–y (x=0.0–1.0) were prepared by the solid state reaction method. Their X-ray diffraction patterns and57Fe Mössbauer spectra at room temperature were measured. It is found that Sr ions incorporate in the lattice of EuFeO3, the change of crystal structure is related to the dopant.57Fe Mössbauer spectra consist of one magnetic, one doublet and one single paramagnetic components. The Fe ions in the cubic phase are in intermediate valence state between Fe(III) and Fe(IV) and may participate in electron hopping.  相似文献   
102.
Microscopic phonon theory of semiconductor nanocrystals (NCs) is reviewed in this paper. Phonon modes of Si and Ge NCs with various sizes of up to 7 nm are investigated by valence force field theory. Phonon modes in spherical SiGe alloy NCs approximately 3.6 nm (containing 1147 atoms) in size have been investigated as a function of the Si concentration. Phonon density-of-states, quantum confinement effects, as well as Raman intensities are discussed.   相似文献   
103.
Zhang  Hengkai  Zhang  Yaokang  Yang  Guang  Ren  Zhiwei  Yu  Wei  Shen  Dong  Lee  Chun-Shing  Zheng  Zijian  Li  Gang 《中国科学:化学(英文版)》2019,62(7):875-882
From a base material of conductive polymer(poly-(3,4-ethylenedioxythiophene):poly(styrenesulfonate),PEDOT:PSS),a flexible and high-conductivity(as low as 45Ω/sq)transparent electrode was fabricated on polydimethylsiloxane elastomer by an acid treatment and transfer process.Combined with the D-sorbitol-doped PEDOT:PSS electric glue,we successfully demonstrated a vacuum-free and ambient lamination fabrication process for semi-transparent perovskite solar cells using triple cation Cs_(0.05)(MA_(0.17)FA_(0.83))_(0.95)Pb(I_(0.83)Br_(0.17))_3perovskite.By this manufacturing-friendly lamination process,we fabricated semitransparent perovskite solar cell devices with power conversion efficiencies up to 16.4%and variable transparencies.  相似文献   
104.
105.
Noble-metal aerogels (NMAs) have drawn increasing attention because of their self-supported conductive networks, high surface areas, and numerous optically/catalytically active sites, enabling their impressive performance in diverse fields. However, the fabrication methods suffer from tedious procedures, long preparation times, unavoidable impurities, and uncontrolled multiscale structures, discouraging their developments. By utilizing the self-healing properties of noble-metal aggregates, the freezing-promoted salting-out behavior, and the ice-templating effect, a freeze–thaw method is crafted that is capable of preparing various hierarchically structured noble-metal gels within one day without extra additives. In light of their cleanliness, the multi-scale structures, and combined catalytic/optical properties, the electrocatalytic and photoelectrocatalytic performance of NMAs are demonstrated, which surpasses that of commercial noble-metal catalysts.  相似文献   
106.
Journal of Sol-Gel Science and Technology - In this paper, a double-layer coating with both redox and plasmonic electrochromic properties has been designed and deposited on fluorine doped tin oxide...  相似文献   
107.
In this paper, we study the thermal properties of the inner horizon of a Kerr-Newman black hole. By adopting Damour-Ruffini method and the thin film model which is developed on the base of brick wall model suggested by ’t Hooft, we calculate the temperature and the entropy of the inner horizon of a Kerr-Newman black hole. We conclude that the temperature of inner horizon is positive and the entropy of the inner horizon is proportional to the area of the inner horizon. The cut-off factor is same as it in calculation of the entropy of the outer horizon, 90β. In addition, we write the integral and differential Bekenstein-Smarr formula as the parameters of the inner horizon. Then, we discuss that if the contribution of the inner horizon is taken into account to the total entropy of the black hole, the Nernst theorem can be satisfied. At last, We calculate the tunneling rate of the outer horizon Γ+ and the inner horizon Γ. The total tunneling rate Γ should be the product of the rates of the outer and inner horizon, Γ=Γ+⋅Γ. We find that the total tunneling rate is in agreement with the Parikh’s standard result, Γ→exp (ΔS BH ), and there is no information loss.  相似文献   
108.
René Michel 《Extremes》2007,10(3):83-107
The investigation of multivariate generalized Pareto distributions (GPDs) has begun only recently. For further progress with these distributions simulation methods are an important part. We describe several methods of simulating GPDs, beginning with an efficient method for the logistic GPD. The algorithm is based on the Shi transformation, which was already used for the simulation of multivariate extreme value distributions (EVDs) of logistic type. In the sequel another algorithm is presented simulating a broader class of GPDs. Due to its numerical complexity it is only practicably applicable in low dimensions. A method is given to generate unconditional GPD random vectors from conditionally GPD distributed random vectors. A short application of the simulation methods in the analysis of a real hydrological data set concludes the article. The simulation algorithms are available on the author’s home page .   相似文献   
109.
We measured fluorescence lifetimes of L-Tryptophan dissolved in de-ionized water and in ethanol in the absence and the presence of high progesterone concentrations. The hormone absorbs between 220 and 280 with a peak around 250 nm, while its absorption is equal to zero beyond 280 nm. Tryptophan excitation spectrum recorded in presence of progesterone shows that the So1La transition is completely abolished while the So 1Lb transition is not affected. Emission of L-tryptophan in water occurs with two fluorescence lifetimes, 0.40 and 2.8 ns. In ethanol, three fluorescence lifetimes equal to around 0.2, 1.8 and 4.8 ns were observed. Addition of progesterone to the medium does not affect any of the fluorescence lifetimes indicating clearly that both transitions could induce tryptophan excitation and that recorded fluorescence lifetimes could be assigned to sub-structures generated in the excited state.  相似文献   
110.

Background  

Marlin-1 is a microtubule binding protein that associates specifically with the GABAB1 subunit in neurons and with members of the Janus kinase family in lymphoid cells. In addition, it binds the molecular motor kinesin-I and nucleic acids, preferentially single stranded RNA. Marlin-1 is expressed mainly in the central nervous system but little is known regarding its cellular and subcellular distribution in the brain.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号