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   696467篇
  免费   31131篇
  国内免费   19197篇
化学   388726篇
晶体学   10513篇
力学   31342篇
综合类   38篇
数学   85175篇
物理学   231001篇
  2020年   5129篇
  2019年   5829篇
  2018年   6282篇
  2017年   6845篇
  2016年   10994篇
  2015年   8810篇
  2014年   11524篇
  2013年   31957篇
  2012年   23920篇
  2011年   30033篇
  2010年   23902篇
  2009年   23653篇
  2008年   25978篇
  2007年   25654篇
  2006年   24573篇
  2005年   22970篇
  2004年   22038篇
  2003年   19259篇
  2002年   18933篇
  2001年   20998篇
  2000年   16178篇
  1999年   13398篇
  1998年   11089篇
  1997年   10756篇
  1996年   10942篇
  1995年   10417篇
  1994年   10305篇
  1993年   10022篇
  1992年   10663篇
  1991年   9998篇
  1990年   9444篇
  1989年   9361篇
  1988年   9515篇
  1987年   8875篇
  1986年   8424篇
  1985年   11249篇
  1984年   11472篇
  1983年   9295篇
  1982年   10295篇
  1981年   9932篇
  1980年   9731篇
  1979年   9885篇
  1978年   10161篇
  1977年   10103篇
  1976年   10221篇
  1975年   9310篇
  1974年   9093篇
  1973年   9653篇
  1972年   6258篇
  1968年   5283篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Journal of Fluorescence - This report describes a combined immunofluorescence and fluorescence viability stain applied as one staining solution for rapid detection of live Legionella...  相似文献   
2.
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   
3.
Yang  T. L.  Kao  C. L.  Kuo  C. E.  Yeh  H. C.  Li  W. J.  Li  H. T.  Chen  C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the...  相似文献   
4.
Kinetics and Catalysis - The results of studies in the field of synthesis and characterization of layered double hydroxides (LDHs) obtained using solid-phase reactions are summarized. The effect of...  相似文献   
5.
Mechanics of Composite Materials - Carbon fiber (CF)/ polyamide (PA6) composites are one of the most promising thermoplastic materials for automobile applications. However, the interfacial...  相似文献   
6.
Journal of Structural Chemistry - A new polymorph of the [ReCl3(MeCN)(PPh3)2] complex is synthesized and characterized by single crystal X-ray diffraction (XRD). Its recrystallization from the...  相似文献   
7.
A selective, highly sensitive, precise, and novel bioanalytical method has been developed and validated to quantify sinococuline, an active constituent present in the phytopharmaceutical drug product containing Cocculus hirsutus plant extract, in vivo. Chromatographic separation was achieved on a Luna Omega Polar-C18 bonded analytical column maintained at 45°C. The isocratic mobile phase consisted of methanol and ammonium formate buffer (60:40, v/v) at acidic pH with a low flow rate of 0.250 mL/min. Detection was performed on an API 4000 mass spectrometer using electrospray ionization in positive polarity and multiple reaction monitoring mode to achieve a lower limit of quantification of 1.50 ng/mL. Excellent accuracy and precision were obtained after extracting the analyte from plasma samples using a chemical analogue as an internal standard in the absence of an isotope-labeled compound. The extraction efficacy was evidenced from recovery study, and the analyte was found to be stable in plasma. Validation study demonstrated linearity with coefficient of correlation, r ≥ 0.99, and minimal matrix effect. This bioanalytical method was successfully applied to evaluate pharmacokinetic parameters of sinococuline from a phase I clinical trial of an aqueous extract of C. hirsutus in healthy human volunteers.  相似文献   
8.
9.
Aequationes mathematicae - In this paper, we establish a new class of dynamic inequalities of Hardy’s type which generalize and improve some recent results given in the literature. More...  相似文献   
10.
Russian Journal of Applied Chemistry - A method for the disposal of hydrolysis lignin waste based on its modification with ZnCl2 and FeCl3 and subsequent carbonization at 800°C was proposed....  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