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   28744篇
  免费   5086篇
  国内免费   3716篇
化学   20814篇
晶体学   314篇
力学   1733篇
综合类   230篇
数学   3382篇
物理学   11073篇
  2024年   28篇
  2023年   564篇
  2022年   618篇
  2021年   908篇
  2020年   1144篇
  2019年   1139篇
  2018年   1005篇
  2017年   934篇
  2016年   1373篇
  2015年   1361篇
  2014年   1673篇
  2013年   2118篇
  2012年   2606篇
  2011年   2657篇
  2010年   1870篇
  2009年   1833篇
  2008年   2042篇
  2007年   1838篇
  2006年   1688篇
  2005年   1414篇
  2004年   1041篇
  2003年   846篇
  2002年   842篇
  2001年   702篇
  2000年   630篇
  1999年   641篇
  1998年   520篇
  1997年   491篇
  1996年   496篇
  1995年   432篇
  1994年   327篇
  1993年   298篇
  1992年   236篇
  1991年   217篇
  1990年   217篇
  1989年   175篇
  1988年   114篇
  1987年   90篇
  1986年   93篇
  1985年   83篇
  1984年   47篇
  1983年   50篇
  1982年   44篇
  1981年   29篇
  1980年   15篇
  1979年   6篇
  1977年   4篇
  1974年   4篇
  1972年   4篇
  1957年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Zheng  Xinyan  Hu  Po  Yao  Ruxian  cheng  Jinhe  Chang  Yiheng  Wu  Haitao  Mei  Hongying  Sun  Shuxiang  Chen  Qingtai  liu  Fang  Chen  Shujing  Wen  Hua 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(5):2217-2226
Journal of Radioanalytical and Nuclear Chemistry - Enhancement of U(VI) biomineralization by Saccharomyces cerevisiae through addition of inorganic phosphorus was studied in this work. The addition...  相似文献   
2.
3.
Hou  Gaoyuan  Zhao  Sishun  Peng  Liyuan  Fang  Zhiqiang  Isogai  Akira 《Cellulose (London, England)》2022,29(13):7365-7376
Cellulose - A bleached softwood kraft pulp was phosphorylated with (NH4)2HPO4 and urea at 150 ℃ for 0‒40 min, and the structures and properties of the resulting...  相似文献   
4.
Given a graph sequence denote by T3(Gn) the number of monochromatic triangles in a uniformly random coloring of the vertices of Gn with colors. In this paper we prove a central limit theorem (CLT) for T3(Gn) with explicit error rates, using a quantitative version of the martingale CLT. We then relate this error term to the well-known fourth-moment phenomenon, which, interestingly, holds only when the number of colors satisfies . We also show that the convergence of the fourth moment is necessary to obtain a Gaussian limit for any , which, together with the above result, implies that the fourth-moment condition characterizes the limiting normal distribution of T3(Gn), whenever . Finally, to illustrate the promise of our approach, we include an alternative proof of the CLT for the number of monochromatic edges, which provides quantitative rates for the results obtained in [7].  相似文献   
5.
Surface plasmon can trigger or accelerate many photochemical reactions, especially useful in energy and environmental industries. Recently, molecular adsorption has proven effective in modulating plasmon-mediated photochemistry, however the realized chemical reactions are limited and the underlying mechanism is still unclear. Herein, by using in situ dark-field optical microscopy, the plasmon-mediated oxidative etching of silver nanoparticles (Ag NPs), a typical hot-hole-driven reaction, is monitored continuously and quantitatively. The presence of thiol or thiophenol molecules is found essential in the silver oxidation. In addition, the rate of silver oxidation is modulated by the choice of different thiol or thiophenol molecules. Compared with the molecules having electron donating groups, the ones having electron accepting groups accelerate the silver oxidation dramatically. The thiol/thiophenol modulation is attributed to the modulation of the charge separation between the Ag NPs and the adsorbed thiol or thiophenol molecules. This work demonstrates the great potential of molecular adsorption in modulating the plasmon-mediated photochemistry, which will pave a new way for developing highly efficient plasmonic photocatalysts.  相似文献   
6.
Chemistry of Natural Compounds - A new carotane sesquiterpenoid, methyl gymnabloate (1), was isolated from the fermentation broth of the wild macrofungus Gymnopus sp. 0612-9. Its structure was...  相似文献   
7.
Zhang  Zhen  Gao  Zhi-Tong  Fang  Bo  Zhang  Ye-Wei 《Nonlinear dynamics》2022,109(3):1259-1275
Nonlinear Dynamics - As a simplified model of structures of many kinds, the Euler Bernoulli beam has proved useful for studying vibration suppression. In order to meet engineering design...  相似文献   
8.
Cubic-like CaTaO2N photocatalysts with high crystallinity and uniform particle size were successfully prepared by the flux-assisted nitridation method. The growth of CaTaO2N single crystals under different synthesis conditions was systematically investigated to understand the effects of the crystallinity and optical property on photocatalytic performance of CO2 reduction. Moreover, the modification of CaTaO2N single crystals with core-shell Ni−Ag bicomponent cocatalyst by two-step decoration process gave a 2.4 times higher amount of CO evolution than the deposition of sole Ag cocatalyst, because of the synergistic effects of bicomponent cocatalyst on the interfacial electron transfer and surface catalytic process. This study provides a valuable way to construct high-crystalline photocatalysts with effective bicomponent cocatalyst for visible-light-driven CO2 reduction with H2O.  相似文献   
9.
The Bcl-2 family small molecule inhibitor navitoclax is being clinically evaluated to treat multiple cancers including lymphoid malignancies and small cell lung cancer. A sensitive and reliable method was developed to quantitate navitoclax in human plasma using liquid chromatography with tandem mass spectrometry with which to perform detailed pharmacokinetic studies. Sample preparation involved protein precipitation using acetonitrile. Separation of navitoclax and the internal standard, navitoclax-d8, was achieved with a Waters Acquity UPLC BEH C18 column using isocratic flow over a 3 min total analytical run time. A SCIEX 4500 triple quadrupole mass spectrometer operated in positive electrospray ionization mode was used for the detection of navitoclax. The assay range was 5–5,000 ng/ml and proved to be accurate (89.5–104.9%) and precise (CV ≤ 11%). Long-term frozen plasma stability for navitoclax at −70°C was at least 43 months. The method was applied for the measurement of total plasma concentration of navitoclax in a patient receiving a 250 mg daily oral dose.  相似文献   
10.
Journal of Radioanalytical and Nuclear Chemistry - The simplified 8-oxide system (SiO2-B2O3-Na2O-Al2O3-CaO-TiO2-MoO3-La2O3) has been prepared under two types of cooling methods, and analyzed with...  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