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   12299篇
  免费   2060篇
  国内免费   1974篇
化学   9564篇
晶体学   141篇
力学   647篇
综合类   159篇
数学   1509篇
物理学   4313篇
  2024年   15篇
  2023年   196篇
  2022年   226篇
  2021年   315篇
  2020年   411篇
  2019年   524篇
  2018年   387篇
  2017年   382篇
  2016年   559篇
  2015年   603篇
  2014年   654篇
  2013年   855篇
  2012年   1033篇
  2011年   1072篇
  2010年   836篇
  2009年   692篇
  2008年   869篇
  2007年   766篇
  2006年   750篇
  2005年   652篇
  2004年   551篇
  2003年   557篇
  2002年   641篇
  2001年   584篇
  2000年   410篇
  1999年   333篇
  1998年   241篇
  1997年   173篇
  1996年   164篇
  1995年   148篇
  1994年   132篇
  1993年   86篇
  1992年   97篇
  1991年   118篇
  1990年   71篇
  1989年   43篇
  1988年   46篇
  1987年   35篇
  1986年   25篇
  1985年   26篇
  1984年   16篇
  1983年   23篇
  1982年   6篇
  1981年   3篇
  1980年   2篇
  1977年   1篇
  1975年   1篇
  1971年   1篇
  1936年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Acta Mathematica Sinica, English Series - We are interested in the existence and asymptotic behavior for the least energy solutions of the following fractional eigenvalue problem $$\left({\rm{P}}...  相似文献   
2.
Juglandis Mandshuricae Cortex is the bark of Juglans mandshurica Maxim., which has been used as a folk medicine plant in China and India. In this study, an ultra-high performance liquid chromatography–quadrupole/orbitrap high-resolution mass spectrometry method was developed to clarify and quantify the chemical profiling of Juglandis Mandshuricae Cortex rapidly. A total of 113 compounds were characterized. Among them, seven flavonoids were simultaneously quantified in 15 min, including myricetin, myricetrin, taxifolin, kaempferol, quercetin, quercitrin, and naringenin. The method was validated for accuracy, precision, and the limits of detection and quantification. All calibration curves showed a good linear relationship (r > 0.9990) within test ranges. The intra- and inter-day relative standard deviations were less than 2.16%. Accuracy validation showed that the recovery was between 95.6 and 101.3% with relative standard deviation values below 2.85%. The validated method was successfully applied to determine the contents of seven flavones in Juglandis Mandshuricae Cortex from seven sources and the contents of these places were calculated respectively. This method provides a theoretical basis for further developing the medicinal value of Juglandis Mandshuricae Cortex.  相似文献   
3.
Czechoslovak Mathematical Journal - We propose a lower bound sequence for the minimum eigenvalue of Hadamard product of an M-matrix and its inverse, in terms of an S-type eigenvalues inclusion set...  相似文献   
4.
Zhao  Tianqi  Luo  Tianzi  Fang  Bo  Shi  Lijiang  Jin  Yongxing  Zhou  Pengwei  Yao  Dong  Li  Chenxia  Jing  Xufeng  Hong  Zhi 《Journal of Russian Laser Research》2021,42(5):586-597
Journal of Russian Laser Research - The zero-refractive-index metamaterials have excellent electromagnetic properties, which provide new ideas and methods to realize the control of electromagnetic...  相似文献   
5.
Sun  Cui-Fang  Cheng  Zhi 《Mathematical Notes》2022,111(5-6):925-931
Mathematical Notes - Let $$\mathbb N$$ denote the set of all nonnegative integers, and let $$A\subseteq\mathbb N$$ . Let $$h,n\in\mathbb N$$ , $$h\ge 2$$ and $$r_h(A,n)=\#\{(a_1,\dots,a_h)\in...  相似文献   
6.
Journal of Optimization Theory and Applications - In this paper, we introduce and investigate a new kind of coupled systems, called coupled variational inequalities, which consist of two elliptic...  相似文献   
7.
Ding  Q.  Yao  M.  Wu  Sh.  Zeng  M.  Xue  N.  Wu  D.  Xu  J. 《Journal of Applied Spectroscopy》2022,89(4):712-718
Journal of Applied Spectroscopy - Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the...  相似文献   
8.
Compound I from cytochrome P450 119 prepared by the photooxidation method involving peroxynitrite oxidation of the resting enzyme to Compound II followed by photooxidation to Compound I was compared to Compound I generated by m-chloroperoxybenzoic acid (MCPBA) oxidation of the resting enzyme. The two methods gave the same UV/Visible spectra, the same products from oxidations of lauric acid and palmitic acid and their (ω-2,ω-2,ω-3,ω-3)-tetradeuterated analogues, and the same kinetics for oxidations of lauric acid and caprylic acid. The experimental identities between the transients produced by the two methods leave no doubt that the same Compound I species is formed by the two methods.  相似文献   
9.
An in situ generated oxidation species of nickel quinolinylpropioamide intermediate was produced. Characterization by X-ray absorption near edge structure (XANES) and EPR provides complementary insights into this oxidized nickel species. With aliphatic amides and isocyanides as substrates, a nickel-catalyzed facile synthesis of structurally diverse five-membered lactams could be achieved.  相似文献   
10.
Journal of Thermal Analysis and Calorimetry - The fire behavior of one flame-retardant PVC cable used as building wire is investigated in this work. Bench scale tests were performed using a cone...  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