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   625544篇
  免费   5781篇
  国内免费   1620篇
化学   317051篇
晶体学   7891篇
力学   32019篇
综合类   27篇
数学   83008篇
物理学   192949篇
  2021年   5798篇
  2020年   6293篇
  2019年   7177篇
  2018年   9689篇
  2017年   9813篇
  2016年   13576篇
  2015年   7285篇
  2014年   12344篇
  2013年   27957篇
  2012年   21651篇
  2011年   25763篇
  2010年   19427篇
  2009年   19379篇
  2008年   24378篇
  2007年   24136篇
  2006年   21908篇
  2005年   19568篇
  2004年   18339篇
  2003年   16518篇
  2002年   16339篇
  2001年   17518篇
  2000年   13470篇
  1999年   10445篇
  1998年   8980篇
  1997年   8901篇
  1996年   8333篇
  1995年   7469篇
  1994年   7550篇
  1993年   7271篇
  1992年   7661篇
  1991年   8075篇
  1990年   7791篇
  1989年   7673篇
  1988年   7495篇
  1987年   7247篇
  1986年   6965篇
  1985年   8985篇
  1984年   9414篇
  1983年   7864篇
  1982年   8080篇
  1981年   7637篇
  1980年   7201篇
  1979年   7869篇
  1978年   8093篇
  1977年   8117篇
  1976年   8083篇
  1975年   7716篇
  1974年   7498篇
  1973年   7881篇
  1972年   5787篇
排序方式: 共有10000条查询结果,搜索用时 25 毫秒
1.
Journal of Experimental and Theoretical Physics - Dzyaloshinskii–Moriya interaction, DMI in short, represents an antisymmetric type of magnetic interactions that favor orthogonal orientation...  相似文献   
2.
Kinetics and Catalysis - The catalytic properties of a nickel phosphide catalyst supported on silica gel in the reductive amination of carbonyl compounds were studied in a flow reactor using...  相似文献   
3.
Favipiravir is a potential antiviral medication that has been recently licensed for Covid-19 treatment. In this work, a gadolinium-based magnetic ionic liquid was prepared and used as an extractant in dispersive liquid–liquid microextraction (DLLME) of favipiravir in human plasma. The high enriching ability of DLLME allowed the determination of favipiravir in real samples using HPLC/UV with sufficient sensitivity. The effects of several variables on extraction efficiency were investigated, including type of extractant, amount of extractant, type of disperser and disperser volume. The maximum enrichment was attained using 50 mg of the Gd-magnetic ionic liquid (MIL) and 150 μl of tetrahydrofuran. The Gd-based MIL could form a supramolecular assembly in the presence of tetrahydrofuran, which enhanced the extraction efficiency of favipiravir. The developed method was validated according to US Food and Drug Administration bioanalytical method validation guidelines. The coefficient of determination was 0.9999, for a linear concentration range of 25 to 1.0 × 105 ng/ml. The percentage recovery (accuracy) varied from 99.83 to 104.2%, with RSD values (precision) ranging from 4.07 to 11.84%. The total extraction time was about 12 min and the HPLC analysis time was 5 min. The method was simple, selective and sensitive for the determination of favipiravir in real human plasma.  相似文献   
4.
Chromatographia - We developed a simple, rapid, ecological RP-HPLC method for the estimation of Pitavastatin (PIT), Fenofibrate (FEN), and their impurities in a novel fixed dose combination. We...  相似文献   
5.
Kinetics and Catalysis - A new ruthenium(II) cage complex with polar terminal groups in the apical substituents has been synthesized; the molecular design of the complex contributes to the...  相似文献   
6.
Crystallography Reports - The crystal structure and crystallochemical features of a Fe-deficient zirconium-rich analog of eudialyte from the Lovozero alkaline massif (Kola peninsula) have been...  相似文献   
7.
Nikolaev  N. N. 《JETP Letters》2022,115(11):639-643
JETP Letters - A new approach to search for axions in the storage ring experiments, applicable at a short coherence time of the in-plane polarization as is the case for protons is discussed. The...  相似文献   
8.
Russian Journal of General Chemistry - Aminophosphabetaines, i.e., isobutyl {[alkyl(dimethyl)ammonio]methyl}phosphonates with higher alkyl substituents at the nitrogen atom, were obtained by a...  相似文献   
9.
10.
Thin films with a nanometer-scale thickness are of great interest to both scientific and industrial communities due to their numerous applications and unique behaviors different from the bulk. However, the understanding of thin-film mechanics is still greatly hampered due to their intrinsic fragility and the lack of commercially available experimental instruments. In this review, we first discuss the progression of thin-film mechanical testing methods based on the supporting substrate: film-on-solid substrate method, film-on-water tensile tests, and water-assisted free-standing tensile tests. By comparing past studies on a model polymer, polystyrene, the effect of different substrates and confinement effect on the thin-film mechanics is evaluated. These techniques have generated fruitful scientific knowledge in the field of organic semiconductors for the understanding of structure–mechanical property relationships. We end this review by providing our perspective for their bright prospects in much broader applications and materials of interest.  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