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   240734篇
  免费   6903篇
  国内免费   3637篇
化学   137020篇
晶体学   2899篇
力学   10268篇
综合类   169篇
数学   27078篇
物理学   73840篇
  2021年   2145篇
  2020年   2736篇
  2019年   2853篇
  2018年   3250篇
  2017年   3219篇
  2016年   4783篇
  2015年   3502篇
  2014年   4799篇
  2013年   10569篇
  2012年   9926篇
  2011年   11687篇
  2010年   8136篇
  2009年   7880篇
  2008年   10318篇
  2007年   10312篇
  2006年   9653篇
  2005年   8805篇
  2004年   7666篇
  2003年   6654篇
  2002年   6189篇
  2001年   6863篇
  2000年   5162篇
  1999年   3860篇
  1998年   3192篇
  1997年   3213篇
  1996年   3212篇
  1995年   2908篇
  1994年   2954篇
  1993年   2748篇
  1992年   2983篇
  1991年   3036篇
  1990年   2798篇
  1989年   2682篇
  1988年   2608篇
  1987年   2556篇
  1986年   2551篇
  1985年   3333篇
  1984年   3356篇
  1983年   2803篇
  1982年   3040篇
  1981年   2783篇
  1980年   2586篇
  1979年   2759篇
  1978年   2976篇
  1977年   3012篇
  1976年   3035篇
  1975年   2786篇
  1974年   2889篇
  1973年   2941篇
  1972年   2305篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
Crystallography Reports - Fluoride crystals K2(Ta0.9I0.1)F7 (sp. gr. Р21/c) complementary to the K2TaF7 and K2NbF7 fluoride family have been obtained by hydrothermal synthesis. Their...  相似文献   
2.
The rational designability and chemical tunability of metal-organic frameworks(MOFs)are enabling tributes to efficaciously enhance their room temperature phosphorescence(RTP)performance.A family of stable anionic MOFs,[Zn2(4,5-ImDC)2]M2(NKU-132,M=(CH3)2NH2or(CH2CH3)2NH2),featuring significant RTP have been synthesized.By rational cation selection and in-situ replacement from dimethylammonium to diethylammonium,the phosphorescence lifetime is increased from 30.88 to126.3 ms,along with less sensitivity to air.This work provides an anti-quenching and lifetime tuning example for RTP-MOFmaterials via facile host-guest chemistry.  相似文献   
3.
Journal of Solid State Electrochemistry - The addition of nanocrystalline titanium dioxide (P90) to a cathode of Li/S cell enhances its voltammetric charge capacity by 19%, from which only a small...  相似文献   
4.
Russian Physics Journal - The results of a study of the dislocation structure evolution in polycrystals of homogeneous solid solutions in low-stability states in Cu-Mn-based alloys with FCC crystal...  相似文献   
5.
Russian Physics Journal - Aiming at problems of low probability of interception and poor anti-jamming performance of the multi-output radar, the numerical simulation based on a chaos optimization...  相似文献   
6.
Journal of Thermal Analysis and Calorimetry - Cellophane film production generates cellulosic residues from scraps, edges, and low-quality films. In this work, cellophane was used as a raw material...  相似文献   
7.
Science China Chemistry - Human health is always under global spotlight, but now it suffers from severe environmental issue and various diseases. Developing highly selective and effective...  相似文献   
8.
Artyukh  A. A.  Chernozatonskii  L. A. 《JETP Letters》2022,116(10):737-744
JETP Letters - The mechanical characteristics of diamond-like films, such as Dn21.8, Dn27.8, and Dn29.4 moiré diamanes, formed by the hydrogenation of graphene layers twisted at an angle of...  相似文献   
9.
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   
10.
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   
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