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   17953篇
  免费   483篇
  国内免费   259篇
化学   7416篇
晶体学   386篇
力学   1077篇
综合类   15篇
数学   1656篇
物理学   8145篇
  2023年   100篇
  2022年   223篇
  2021年   210篇
  2020年   163篇
  2019年   198篇
  2018年   265篇
  2017年   217篇
  2016年   372篇
  2015年   280篇
  2014年   446篇
  2013年   841篇
  2012年   1046篇
  2011年   1334篇
  2010年   942篇
  2009年   905篇
  2008年   1045篇
  2007年   1040篇
  2006年   1047篇
  2005年   858篇
  2004年   725篇
  2003年   564篇
  2002年   561篇
  2001年   950篇
  2000年   641篇
  1999年   533篇
  1998年   358篇
  1997年   370篇
  1996年   294篇
  1995年   246篇
  1994年   230篇
  1993年   180篇
  1992年   207篇
  1991年   168篇
  1990年   166篇
  1989年   138篇
  1988年   112篇
  1987年   102篇
  1986年   79篇
  1985年   90篇
  1984年   70篇
  1983年   46篇
  1982年   34篇
  1981年   35篇
  1980年   21篇
  1979年   21篇
  1978年   21篇
  1976年   28篇
  1975年   30篇
  1974年   22篇
  1973年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Li  Y.  Shi  W. H.  Dong  L. M.  Xu  S. X.  Huang  H. J.  Yin  J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,...  相似文献   
3.
4.
Cinnamaldehyde (CA), an active ingredient isolated from the traditional Chinese medicine Cortex Cinnamomi, has a wide range of bioactivities. To clarify the distribution characteristics of CA, a selective and sensitive method utilizing gas chromatography–mass spetrometry was initially developed for simultaneously determining the concentration of CA and its metabolite cinnamyl alcohol in rat tissues. Selected ion masses of m/z 131, 105 and 92 were chosen, and separation of the analytes was performed on a DB‐5 ms (30 m × 0.25 mm, 0.25 µm, thickness) capillary column by gas chromatography–mass spectrometry. The calibration curves demonstrated good linearity and reproducibility over the range of 20–2000 and 20–4000 ng/mL for various tissue samples. Recoveries ranged from 86.8 to 107.5%, while intra‐ and interday relative standard deviations were all <11.3%. The analysis method was successfully applied in tissue distribution studies for CA and cinnamyl alcohol. As CA and cinnamyl alcohol may inter‐convert to one another, simultaneous determination of both analytes provides a comparative and accurate data for tissue study. The concentrations of CA and cinnamyl alcohol remaining in spleen were the highest among the main organs, including heart, liver, spleen, lung, kidney and brain. In addition, there was no long‐term accumulation of CA in rat tissues. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
5.
Su  X. F.  Zhang  Y. L.  Maximov  A. L.  Zhang  K.  Xin  Q.  Feng  C. Q.  Bai  X. F.  Wu  W. 《Russian Journal of Applied Chemistry》2020,93(1):127-136
Russian Journal of Applied Chemistry - Nanoscale ZSM-5 (AlZ5-D) and Ga-substituted ZSM-5 zeolites ((Al,Ga)Z5-D and GaZ5-D) were synthesized by a green dry-gel conversion strategy. For comparison,...  相似文献   
6.
Journal of Thermal Analysis and Calorimetry - In the present work, pyrolysis kinetic mechanism was studied for regenerated cellulosic fiber (RCF) and composite RCF containing silicon/nitrogen flame...  相似文献   
7.
8.
Shi  D.  Feng  J.  Wang  J.  Zhao  W.  Li  X. 《Kinetics and Catalysis》2020,61(5):750-757
Kinetics and Catalysis - A series of Cu-SSZ-13@CeO2 catalysts with surface modification with CeO2 was prepared by the modified self-resemble method based on the one-pot synthesized Cu-SSZ-13...  相似文献   
9.
In this paper, the authors studied certain properties of the estimate of Liang and Krishnaiah (1985, J. Multivariate Anal. 16, 162–172) for multivariate binary density. An alternative shrinkage estimate is also obtained. The above results are generalized to general orthonormal systems.  相似文献   
10.
Let V be a hypersurface with an isolated singularity at the origin in ? n+1. It is a natural question to ask when V is defined by weighted homogeneous polynomial or homogeneous polynomial up to biholomorphic change of coordinates. In 1971, a beautiful theorem of Saito gives a necessary and sufficient condition for V to be defined by a weighted homogeneous polynomial. For a two-dimensional isolated hypersurface signularity V, Xu and Yau found a coordinate free characterization for V to be defined by a homogeneous polynomial. Recently Lin and Yau gave necessary and sufficient conditions for a 3-dimensional isolated hypersurface singularity with geometric genus bigger than zero to be defined by a homogeneous polynomial. The purpose of this paper is to prove that Lin-Yau’s theorem remains true for singularities with geometric genus equal to zero.  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