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   9867篇
  免费   214篇
  国内免费   20篇
化学   5827篇
晶体学   162篇
力学   267篇
数学   735篇
物理学   3110篇
  2023年   94篇
  2022年   211篇
  2021年   162篇
  2020年   177篇
  2019年   240篇
  2018年   207篇
  2017年   232篇
  2016年   318篇
  2015年   212篇
  2014年   400篇
  2013年   781篇
  2012年   548篇
  2011年   655篇
  2010年   417篇
  2009年   405篇
  2008年   460篇
  2007年   440篇
  2006年   335篇
  2005年   281篇
  2004年   229篇
  2003年   163篇
  2002年   184篇
  2001年   117篇
  2000年   125篇
  1999年   86篇
  1998年   56篇
  1997年   56篇
  1996年   92篇
  1995年   104篇
  1994年   98篇
  1993年   92篇
  1992年   120篇
  1991年   86篇
  1990年   79篇
  1989年   92篇
  1988年   87篇
  1987年   90篇
  1986年   74篇
  1985年   104篇
  1984年   119篇
  1983年   82篇
  1982年   98篇
  1981年   97篇
  1980年   102篇
  1979年   90篇
  1978年   102篇
  1977年   84篇
  1976年   56篇
  1975年   61篇
  1974年   74篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
The transmitted photon spectra of133Ba,22Na,137Cs,54Mn and60Co point sources are measured through different thicknesses of water, concrete and sand. The multiple-scatter peaks observed in these materials at 60, 90 and 100 keV energies respectively are found to be independent of incident photon energy and thickness of the medium.  相似文献   
83.
84.
The occurance of the urinary stones varies according to the geographical regions. The presence of stones in the urinary system causes pain and discomfort. These generate colics and hence are sometimes life threatening. In the present study, infrared measurements have been made on several stone samples. It has been found that calcium oxalate, calcium phosphate, magnesiunm ammonium phosphate, calcium carbonate, uric acid, -cystine and xanthin are present, as expected. Also, silicon dioxide is found to be present in some of the stones but in small quantity, in addition to the above constituents. This constituent is responsible to exhibit piezoelectricity in the urinary calculi.  相似文献   
85.
Narendra Singh 《Pramana》2003,60(1):53-58
Assuming a relation between the quark mass matrices of the two sectors a unique solution can be obtained for the CKM flavor mixing matrix. A numerical example is worked out which is in excellent agreement with experimental data.  相似文献   
86.
High spin states in 120Xe, populated via107Ag(16O, p2n) and108Pd(16O, 4n)reactions have been studied using γ-ray spectroscopic techniques. 21 new transitions have been added to extend the level scheme. Two S-bands are extended upto 26+ and 22+;these bands are found to cross the g. s band at hΩ=0. 39 and 0. 47 MeV. The band structures have been discussed within the framework of CSM.  相似文献   
87.
The effect of volume corrections on the equations of state for the hadron gas by treating nucleons and antinucleons as hard-core particles or bags is studied. Its consequences on the critical values of temperatureT and chemical potential μ B of the phase transition from a gas of finite sized hadrons to an interacting quark matter are explored.  相似文献   
88.
Glancing angle deposition (GLAD) has been employed to fabricate the Si/Si–O nanowires (NWs). The perpendicular NW on silicon substrate shows the amorphous nature. The visible light emission from the NWs was observed from the Si/Si–O nanoparticles. High light absorption inside the Si/Si–O NW structure was recorded.  相似文献   
89.
Y2O3 nanoparticles and nanorods have been firstly synthesized in bulk Ti-Y films prepared by magnetron sputtering on Si (100) substrates at different temperatures. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS) are used to characterize the structure, morphology, and composition of the as-synthesized nanoparticles and nanorods. The mechanical properties of the sputtered films are investigated using nanoindentation techniques. The results indicate that both the nanoparticles and nanorods have a pure cubic Y2O3 structure resulting from the reaction of Y atoms with the residual O2 in the vacuum chamber, and are free from defects and dislocations with uniform diameters of about 30 nm. The Y2O3 nanoparticles mainly distribute at the grain boundaries of the Ti matrix and the nanorods have lengths ranging from 250 nm to more than 1 μm with the growth direction parallel to the (002) plane. As the growth temperature elevates, the nanoparticles turn to be coarsening while more and longer nanorods are inclined to form. Compared with the Ti film, the TiY films have a remarkable increase in hardness, but do not exhibit expected increase in elastic modulus. Finally, the growth mechanism is also briefly discussed.  相似文献   
90.
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