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   48949篇
  免费   8563篇
  国内免费   6567篇
化学   34436篇
晶体学   751篇
力学   3181篇
综合类   496篇
数学   6024篇
物理学   19191篇
  2024年   40篇
  2023年   902篇
  2022年   1075篇
  2021年   1413篇
  2020年   1862篇
  2019年   1832篇
  2018年   1636篇
  2017年   1593篇
  2016年   2298篇
  2015年   2305篇
  2014年   2802篇
  2013年   3559篇
  2012年   4328篇
  2011年   4541篇
  2010年   3157篇
  2009年   3216篇
  2008年   3471篇
  2007年   3143篇
  2006年   3024篇
  2005年   2319篇
  2004年   1959篇
  2003年   1618篇
  2002年   1591篇
  2001年   1365篇
  2000年   1178篇
  1999年   1073篇
  1998年   887篇
  1997年   778篇
  1996年   780篇
  1995年   701篇
  1994年   611篇
  1993年   505篇
  1992年   471篇
  1991年   363篇
  1990年   339篇
  1989年   272篇
  1988年   221篇
  1987年   189篇
  1986年   169篇
  1985年   167篇
  1984年   108篇
  1983年   73篇
  1982年   62篇
  1981年   39篇
  1980年   18篇
  1979年   12篇
  1977年   2篇
  1959年   1篇
  1957年   3篇
  1936年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Yin  Qingqing  Xu  Fen  Sun  Lixian  Li  Yaying  Liao  Lumin  Wang  Tao  Guan  Yanxun  Xia  Yongpeng  Zhang  Chenchen  Wei  Sheng  Zhang  Huanzhi  Li  Bin 《Journal of Thermal Analysis and Calorimetry》2022,147(12):6583-6592
Journal of Thermal Analysis and Calorimetry - Polyethylene glycol (PEG) is widely used as phase change materials (PCMs). However, the leakage and low thermal conductivity issues restrict its...  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.
4.
Journal of Algebraic Combinatorics - Highly nonlinear functions (bent functions, perfect nonlinear functions, etc.) on finite fields and finite (abelian or nonabelian) groups have been studied in...  相似文献   
5.
Acta Mathematicae Applicatae Sinica, English Series - In this paper, we investigate a delayed HIV infection model that considers the homeostatic proliferation of CD4+ T cells. The existence and...  相似文献   
6.
Three nonfused ring electron acceptors (NFREAs) TTC6,TT-C8T and TT-TC8 were purposefully designed and synthesized.The molecular geometry can be adjusted by the steric hindrance of lateral substituents.According to the DFT calculations,from TTC6 to TT-C8T and TT-TC8,planarity of the molecular backbone is gradually improved,accompanying with the enhancing of intramolecular charge transfer effect.As for TT-TC8,the two phenyl substituents are almost perpendicular to the molecular backbone,which endues the acceptor with good solubility and suppresses it to form over-aggregation.Multidirectional regular molecular orientation and closer molecular stacking are formed in TT-TC8 film.As a result,TT-TC8 based devices afford the highest PCE of 13.13%,which is much higher than that of TTC6 (4.41%) and TT-C8T (10.42%) and among the highest PCE values based on NFREAs.  相似文献   
7.
Xu  Yifan  Zhang  Hehe  Ding  Tangjing  Tian  Ruiqi  Sun  Dongmei  Wang  Ming-Sheng  Zhou  Xiaosi 《中国科学:化学(英文版)》2022,65(9):1807-1816
Science China Chemistry - Due to their enormous potential for large-scale energy storage, rechargeable potassium-ion batteries have been widely researched and developed. However, the drastic volume...  相似文献   
8.
9.
Czechoslovak Mathematical Journal - Let G = (VG,EG) be a graph and let NG[υ] denote the closed neighbourhood of a vertex υ in G. A function f: VG ? {?1,0,1} is said to be a...  相似文献   
10.
Wu  Penghui  Zhao  Yan  Xu  Xianghong 《应用数学和力学(英文版)》2021,42(12):1743-1758
Applied Mathematics and Mechanics - A consequence of nonlinearities is a multi-harmonic response via a mono-harmonic excitation. A similar phenomenon also exists in random vibration. The power...  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