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   551344篇
  免费   4086篇
  国内免费   1390篇
化学   257956篇
晶体学   6900篇
力学   31345篇
综合类   23篇
数学   95490篇
物理学   165106篇
  2020年   3709篇
  2019年   4363篇
  2018年   20092篇
  2017年   20312篇
  2016年   15962篇
  2015年   5820篇
  2014年   8121篇
  2013年   18162篇
  2012年   19356篇
  2011年   32700篇
  2010年   21401篇
  2009年   21900篇
  2008年   27676篇
  2007年   31752篇
  2006年   14415篇
  2005年   17910篇
  2004年   15178篇
  2003年   14771篇
  2002年   12456篇
  2001年   11961篇
  2000年   9421篇
  1999年   7025篇
  1998年   6161篇
  1997年   6186篇
  1996年   5863篇
  1995年   5272篇
  1994年   5451篇
  1993年   5132篇
  1992年   5792篇
  1991年   5688篇
  1990年   5541篇
  1989年   5465篇
  1988年   5497篇
  1987年   5406篇
  1986年   5128篇
  1985年   6732篇
  1984年   7101篇
  1983年   5918篇
  1982年   5974篇
  1981年   5896篇
  1980年   5674篇
  1979年   5989篇
  1978年   6293篇
  1977年   6285篇
  1976年   6318篇
  1975年   5863篇
  1974年   5879篇
  1973年   6155篇
  1972年   4432篇
  1971年   3848篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
Far-red emitting fluorescent labels are highly desirable for spectral multiplexing and deep tissue imaging. Here, we describe the generation of frFAST (far-red Fluorescence Activating and absorption Shifting Tag), a 14-kDa monomeric protein that forms a bright far-red fluorescent assembly with (4-hydroxy-3-methoxy-phenyl)allylidene rhodanine (HPAR-3OM). As HPAR-3OM is essentially non-fluorescent in solution and in cells, frFAST can be imaged with high contrast in presence of free HPAR-3OM, which allowed the rapid and efficient imaging of frFAST fusions in live cells, zebrafish embryo/larvae, and chicken embryos. Beyond enabling the genetic encoding of far-red fluorescence, frFAST allowed the design of a far-red chemogenetic reporter of protein–protein interactions, demonstrating its great potential for the design of innovative far-red emitting biosensors.  相似文献   
62.
Russian Physics Journal - A relationship between the structural-morphological and physical-mechanical properties of macro-porous calcium phosphate (CaP) coatings on the surface of titanium implants...  相似文献   
63.
64.
65.
The design of new solid-state proton-conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF ( IPCE-1Ni ), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55×10−3 S cm−1 at 75 °C and 80 % relative humidity).  相似文献   
66.
Russian Journal of Physical Chemistry A - Rapidly quenched alloys of aluminum with cobalt and zirconium are investigated using a combination of means of physicochemical analysis to study the...  相似文献   
67.
International Applied Mechanics - The theorems (statements) on the existence of attractor are proved. A generalized Shilnikov theorem is formulated. In the expression for the saddle of a homoclinic...  相似文献   
68.
69.
The change in the free-electron density in ultrathin (5 nm) superconducting NbN films in the initial state and after irradiation by O+ ions to doses of (0.1–0.9) × 1017 cm–2 has been studied by electron energy-loss spectroscopy (EELS). The analysis has been performed on cross section samples prepared by the focused ion beam method, using plasmon oscillations with energies up to 50 eV. The radiation-induced replacement of nitrogen atoms with oxygen atoms in niobium nitride is found to change the electrical properties of the material, which leads to a decrease in the free-electron density with an increase in the irradiation dose.  相似文献   
70.

A complex study of a spearhead dated back to IV mill. BC from burial mound no. 1 near Novosvobodnaya village (collection of the State Historical Museum) and, in particular, the material of spearhead superficial crust has been performed. The elemental and phase composition of the metal of spearhead and the superficial crust on its surface have been determined by scanning electron microscopy, jointly with energydispersive X-ray microanalysis and X-ray phase analysis. A comparative analysis of the results of studying the spearhead superficial crust and similar crusts on other artifacts from the mounds near Novosvobodnaya village suggest natural origin of the crust on copper?arsenic artifacts.

  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