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   253425篇
  免费   30363篇
  国内免费   20810篇
化学   158270篇
晶体学   2945篇
力学   16453篇
综合类   1580篇
数学   32709篇
物理学   92641篇
  2023年   3489篇
  2022年   5258篇
  2021年   6830篇
  2020年   8077篇
  2019年   7816篇
  2018年   7710篇
  2017年   7354篇
  2016年   10433篇
  2015年   9038篇
  2014年   11736篇
  2013年   15968篇
  2012年   18638篇
  2011年   19571篇
  2010年   13792篇
  2009年   13615篇
  2008年   14550篇
  2007年   13186篇
  2006年   12243篇
  2005年   10338篇
  2004年   8437篇
  2003年   6976篇
  2002年   6816篇
  2001年   5873篇
  2000年   5119篇
  1999年   5101篇
  1998年   4521篇
  1997年   4291篇
  1996年   4332篇
  1995年   3658篇
  1994年   3466篇
  1993年   3075篇
  1992年   2822篇
  1991年   2663篇
  1990年   2423篇
  1989年   2070篇
  1988年   1737篇
  1987年   1581篇
  1986年   1488篇
  1985年   1495篇
  1984年   1317篇
  1983年   1134篇
  1982年   1049篇
  1981年   866篇
  1979年   877篇
  1978年   878篇
  1977年   856篇
  1976年   974篇
  1975年   876篇
  1974年   902篇
  1973年   882篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
3,4-Difluorobenzyl(1-ethyl-5-(4-((4-hydroxypiperidin-1-yl)-methyl)thiazol-2-yl)-1H-indol-3-yl)carbamate (NAI59), a small molecule with outstanding therapeutic effectiveness to anti-pulmonary fibrosis, was developed as an autotaxin inhibitor candidate compound. To evaluate the pharmacokinetics and plasma protein binding of NAI59, a UPLC–MS/MS method was developed to quantify NAI59 in plasma and phosphate-buffered saline. The calibration curve linearity ranged from 9.95 to 1990.00 ng/mL in plasma. The accuracy was −6.8 to 5.9%, and the intra- and inter-day precision was within 15%. The matrix effect and recovery, as well as dilution integrity, were within the criteria. The chromatographic and mass spectrometric conditions were also feasible to determine phosphate-buffered saline samples, and it has been proved that this method exhibits good precision and accuracy in the range of 9.95–497.50 ng/mL in phosphate-buffered saline. This study is the first to determine the pharmacokinetics, absolute bioavailability, and plasma protein binding of NAI59 in rats using this established method. Therefore, the pharmacokinetic profiles of NAI59 showed a dose-dependent relationship after oral administration, and the absolute bioavailability in rats was 6.3%. In addition, the results of protein binding showed that the combining capacity of NAI59 with plasma protein attained 90% and increased with the increase in drug concentration.  相似文献   
52.
Hu  Duo-Duo  Gao  Qian  Dai  Jing-Cheng  Cui  Ru  Li  Yuan-Bo  Li  Yuan-Ming  Zhou  Xiao-Guo  Bian  Kang-Jie  Wu  Bing-Bing  Zhang  Kai-Fan  Wang  Xi-Sheng  Li  Yan 《中国科学:化学(英文版)》2022,65(4):753-761
Science China Chemistry - A light-induced, nickel-catalyzed three-component arylsulfonation of 1,3-enynes in the absence of photocatalyst is reported. This methodology exhibited mild conditions,...  相似文献   
53.
Xu  Mengtao  Li  Changyou  Sun  Yang  Yang  Tianzhi  Zhang  Hongzhuang  Liu  Zhendong  Liu  Haiyang  Li  Zhenyuan  Zhang  Yimin 《Nonlinear dynamics》2021,105(4):3061-3092
Nonlinear Dynamics - Investigation of the dynamic characteristics of linear guideway is essential for enhancing structural performance of machine tools. However, few mechanical models are...  相似文献   
54.
Jin  Zhuochen  Cao  Nan  Shi  Yang  Wu  Wenchao  Wu  Yingcai 《显形杂志》2021,24(2):349-364
Journal of Visualization - The increasing availability of spatiotemporal data provides unprecedented opportunities for understanding the structure of an urban area in terms of people’s...  相似文献   
55.
56.
International Journal of Theoretical Physics - The Majorana representation, which provides an intuitive way to represent the quantum state by stars on the Bloch sphere, has drawn considerable...  相似文献   
57.
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   
58.

We study the Bell nonlocality of high dimensional quantum systems based on quantum entanglement. A quantitative relationship between the maximal expectation value B of Bell operators and the quantum entanglement concurrence C is obtained for even dimension pure states, with the upper and lower bounds of B governed by C.

  相似文献   
59.
Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device.  相似文献   
60.
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