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   4840篇
  免费   801篇
  国内免费   542篇
化学   3354篇
晶体学   46篇
力学   345篇
综合类   24篇
数学   623篇
物理学   1791篇
  2024年   18篇
  2023年   102篇
  2022年   119篇
  2021年   182篇
  2020年   199篇
  2019年   194篇
  2018年   181篇
  2017年   139篇
  2016年   269篇
  2015年   220篇
  2014年   256篇
  2013年   371篇
  2012年   472篇
  2011年   456篇
  2010年   308篇
  2009年   290篇
  2008年   307篇
  2007年   250篇
  2006年   248篇
  2005年   211篇
  2004年   185篇
  2003年   162篇
  2002年   132篇
  2001年   111篇
  2000年   94篇
  1999年   100篇
  1998年   75篇
  1997年   74篇
  1996年   74篇
  1995年   60篇
  1994年   45篇
  1993年   45篇
  1992年   27篇
  1991年   38篇
  1990年   35篇
  1989年   26篇
  1988年   12篇
  1987年   13篇
  1986年   14篇
  1985年   18篇
  1984年   9篇
  1983年   10篇
  1982年   7篇
  1981年   4篇
  1974年   2篇
  1944年   4篇
  1943年   1篇
  1942年   3篇
  1941年   1篇
  1940年   1篇
排序方式: 共有6183条查询结果,搜索用时 15 毫秒
181.
Journal of Radioanalytical and Nuclear Chemistry - The concentrations of 238U, 226Ra, 232Th and 40K and gross α, β were measured in soils and sediments around a uranium tailings reservoir...  相似文献   
182.
Carbon dots (CDs), as an emerging fluorescent nanomaterial with low toxicity, has been widely applied in various bio‐related fields. However, investigations on their capabilities in guiding osteogenic differentiation are rarely seen, which has great significance in osteoporosis therapy and bone regeneration. Herein, for the first time, a new kind of Mg2+‐doped CDs is facilely synthesized through a one‐step hydrothermal method from metal gluconate salts. The CDs can serve as nanocarrier of Mg2+ ions entering into cells, and the bioessential metal ions subsequently stimulate osteoblastic differentiation by improving alkaline phosphatase (ALP) activity and upregulation related mRNA expression. Noteworthy, the raw material has almost negligible performance on osteoblastic differentiation compared to Mg‐CDs, which is due to the ultrasmall sizes of CDs and the efficient uptake by cells. Moreover, benefitting from the fluorescence properties, Mg‐CDs can also be applied as cell labeling agents. This work proposes a new strategy to synthesize multifunctional metal ion‐doped CDs, which might had great potential in serving as promising nanodrugs for bone loss therapy.  相似文献   
183.
A highly selective and efficient LC–MS/MS method was developed to determine the plasma concentration of magnolol, hesperidin, neohesperidin and geniposide following oral administration of Zhi‐Zi‐Hou‐Po decoction in normal and depressed rats. Plasma samples were pretreated by protein precipitation with methanol. Chromatographic separation was performed on an XTerra® MS C18 column using a gradient elution with a mobile phase composed of acetonitrile–0.1% aqueous formic acid. The proposed method was validated to be specific, accurate and precise for the analytes determination in plasma samples. The calibration curves displayed good linearity over definite concentration ranges for the analytes. The intra‐ and inter‐day precision of the proposed method at three different levels were all within <11.13% and the relative errors ranged from ?8.46 to 8.93%. The recovery of the four compounds ranged from 82.72 to 89.08% and no apparent matrix effect was observed during sample analysis. After full validation, the established method was successfully applied for comparing the pharmacokinetics of four components between normal and depressed rats. The results showed that the AUC and Cmax of four analytes in depressed rats were significantly different from those in normal rats and might provide helpful information to guide the clinical use of Zhi‐Zi‐Hou‐Po to treat depression.  相似文献   
184.
Journal of Thermal Analysis and Calorimetry - The effect of cadmium phenylmalonate (PMA-Cd) as a novel nucleating agent on the crystallization behaviors and spherulitic morphology of poly(lactic...  相似文献   
185.
186.
Russian Journal of General Chemistry - The Grubbs–Hoveyda catalysts have a wide range of applications in catalyzed formation of the carbon-carbon double bonds. In this study, several...  相似文献   
187.
Bai  Hongyi  Min  Rui  Yang  Ziheng 《Optical Review》2019,26(6):549-560
Optical Review - An efficient method of reconstructing the phase distribution for off-axis digital holography is proposed using hologram multiplexing with hologram rotation and complex encoding. A...  相似文献   
188.
Zhu  Hong  Zeng  Xiangbing  Han  Tianli  Li  Xuexue  Zhu  Shuguang  Sun  Bai  Zhou  Ping  Liu  Jinyun 《Journal of Solid State Electrochemistry》2019,23(7):2173-2180
Journal of Solid State Electrochemistry - Since conventional graphite-based anode possesses a low capacity, seeking for high-capacity anode candidates becomes significant for constructing emerging...  相似文献   
189.
190.
The core–shell structure Fe3O4/SiO2 magnetic microspheres were prepared by a sol–gel method, and immobiled with iminodiacetic acid (IDA) as metal ion affinity ligands for protein adsorption. The size, morphology, magnetic properties and surface modification of magnetic silica nanospheres were characterized by various modern analytical instruments. It was shown that the magnetic silica nanospheres exhibited superparamagnetism with saturation magnetization values of up to 58.1 emu/g. Three divalent metal ions, Cu2+, Ni2+ and Zn2+, were chelated on the Fe3O4@SiO2–IDA magnetic microspheres to adsorb lysozyme. The results indicated that Ni2+‐chelating magnetic microspheres had the maximum adsorption capacity for lysozyme of 51.0 mg/g, adsorption equilibrium could be achieved within 60 min and the adsorbed protein could be easily eluted. Furthermore, the synthesized Fe3O4@SiO2–IDA–Ni2+ magnetic microspheres were successfully applied for selective enrichment lysozyme from egg white and His‐tag recombinant Homer 1a from the inclusion extraction expressed in Escherichia coli. The result indicated that the magnetic microspheres showed unique characteristics of high selective separation behavior of protein mixture, low nonspecific adsorption, and easy handling. This demonstrates that the magnetic silica microspheres can be used efficiently in protein separation or purification and show great potential in the pretreatment of the biological sample. Copyright © 2015 John Wiley & Sons, Ltd.  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