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   113049篇
  免费   7923篇
  国内免费   6353篇
化学   66503篇
晶体学   1379篇
力学   6643篇
综合类   451篇
数学   13801篇
物理学   38548篇
  2023年   987篇
  2022年   1501篇
  2021年   2347篇
  2020年   2830篇
  2019年   3039篇
  2018年   3299篇
  2017年   3248篇
  2016年   4111篇
  2015年   2996篇
  2014年   4256篇
  2013年   5916篇
  2012年   6384篇
  2011年   6751篇
  2010年   5199篇
  2009年   5100篇
  2008年   5451篇
  2007年   5088篇
  2006年   4720篇
  2005年   4121篇
  2004年   3579篇
  2003年   3215篇
  2002年   3325篇
  2001年   2983篇
  2000年   2313篇
  1999年   1946篇
  1998年   1808篇
  1997年   1579篇
  1996年   1519篇
  1995年   1289篇
  1994年   1336篇
  1993年   1236篇
  1992年   1209篇
  1991年   1281篇
  1990年   1227篇
  1989年   1140篇
  1988年   981篇
  1987年   977篇
  1986年   945篇
  1985年   967篇
  1984年   958篇
  1983年   856篇
  1982年   826篇
  1979年   815篇
  1978年   833篇
  1977年   830篇
  1976年   940篇
  1975年   829篇
  1974年   859篇
  1973年   869篇
  1972年   763篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
21.
Siberian Mathematical Journal - We give a simple proof of one assertion used in solving Waring’s problem.  相似文献   
22.
Crystallography Reports - The three-dimensional structure of recombinant thermophilic ribokinase from Thermus speсies 2.9 was determined at 2.4 Å resolution using crystals, which were...  相似文献   
23.
Journal of Radioanalytical and Nuclear Chemistry - The simplified 8-oxide system (SiO2-B2O3-Na2O-Al2O3-CaO-TiO2-MoO3-La2O3) has been prepared under two types of cooling methods, and analyzed with...  相似文献   
24.
In this paper,we first construct compact embeddedλ-hypersurfaces with the topology of torus which are calledλ-torus in Euclidean spaces?n^+1.Then,we give many compact immersedλ-hypersurfaces in Euclidean spaces?n^+1.  相似文献   
25.
26.
Journal of Fourier Analysis and Applications - We develop a theory of Sobolev orthogonal polynomials on the Sierpiński gasket ( $$SG$$ ), which is a fractal set that can be viewed as a limit...  相似文献   
27.
Journal of Applied and Industrial Mathematics - We study the problem of optimal location of the ambulance fleet at the base stations. The objective is to minimize the average waiting time for...  相似文献   
28.
Yu  Yangyang  Li  Jiajia  Yuan  Zhixuan  Fan  Yongchen  Wu  Ying 《Nonlinear dynamics》2022,109(4):3113-3132
Nonlinear Dynamics - Epilepsy is the second largest neurological disease which seriously threatens human life and health. The one important reason of inducing epileptic seizures is ischemic stroke...  相似文献   
29.
Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag2S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag2S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag2S had more opportunities to react with surrounding O2, which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag2S and PDA-Ag2S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag2S showed distinctly better therapeutic effects than Ag2S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag2S quantum dots, which extended and enhanced the regulatory effect originating from PDA.  相似文献   
30.
A novel plasmonic polarization filter based on the diamond-shape photonic crystal fiber(PCF) is proposed. The resonant coupling characteristics of the PCF polarization filter are investigated by the full-vector finite-element method. By optimizing the geometric parameters of the PCF, when the fiber length is 5 mm, the polarization filter has a bandwidth of 990 nm and an extinction ratio(ER) of lower than -20 dB. Moreover, a single wavelength polarization filter can also be achieved, along with an ER of -279.78 dB at wavelength 1.55 μm. It is believed that the proposed PCF polarization filter will be very useful in laser and optical communication systems.  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