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   88786篇
  免费   15503篇
  国内免费   9692篇
化学   61968篇
晶体学   894篇
力学   5881篇
综合类   494篇
数学   10563篇
物理学   34181篇
  2024年   99篇
  2023年   1856篇
  2022年   2000篇
  2021年   2925篇
  2020年   3735篇
  2019年   3567篇
  2018年   3065篇
  2017年   2824篇
  2016年   4312篇
  2015年   4182篇
  2014年   4993篇
  2013年   6590篇
  2012年   8214篇
  2011年   8515篇
  2010年   5713篇
  2009年   5500篇
  2008年   5859篇
  2007年   5309篇
  2006年   4766篇
  2005年   4006篇
  2004年   3188篇
  2003年   2513篇
  2002年   2211篇
  2001年   1867篇
  2000年   1722篇
  1999年   1815篇
  1998年   1546篇
  1997年   1481篇
  1996年   1499篇
  1995年   1245篇
  1994年   1123篇
  1993年   928篇
  1992年   807篇
  1991年   710篇
  1990年   618篇
  1989年   489篇
  1988年   386篇
  1987年   323篇
  1986年   305篇
  1985年   265篇
  1984年   185篇
  1983年   129篇
  1982年   94篇
  1981年   83篇
  1980年   72篇
  1979年   43篇
  1978年   34篇
  1977年   47篇
  1976年   38篇
  1973年   33篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Journal of Optimization Theory and Applications - This paper considers an optimal control problem governed by nonlinear fractional-order systems with multiple time-varying delays and subject to...  相似文献   
102.
Journal of Radioanalytical and Nuclear Chemistry - In the present work the final products of coumarin radiation chemical transformation are investigated by chromatography. During radiolysis of...  相似文献   
103.
The combination of the macrocyclic hosts p-sulfonatocalix[4]arene and cucurbit[7]uril with the fluorescent dyes lucigenin and berberine affords two label-free enzyme assays for the detection of kinase and phosphatase activity by fluorescence monitoring. In contrast to established assays, no substrate labeling is required. Since phosphorylation is one of the most important regulatory mechanisms in biological signal transduction, the assays should be useful for identification of inhibitors and activators in high-throughput screening (HTS) format for drug discovery.  相似文献   
104.
Wu  Peng  Wang  Yun  Li  Yang  Hu  Xuewen  Xiu  Taoyuan  Yuan  Dingzhong  Liu  Yan  Wu  Zhenyu  Liu  Zhirong 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(2):553-559
Journal of Radioanalytical and Nuclear Chemistry - In order to reduce the potential toxicity to the environment after treatment of radioactive waste water, an eco-friendly graphene oxide...  相似文献   
105.
A new A, D-seco limonoid, named 12-acetyloxyperforatin (1), along with three known ones, were isolated from the leaves of Harrisonia perforata. Their structures were elucidated on the basis of spectroscopic analysis, including extensive NMR techniques and computational modelling. These compounds showed no inhibitory activity against the 11β-HSD1 enzyme.  相似文献   
106.
107.
Journal of Thermal Analysis and Calorimetry - In order to understand the catalytic effects of inherent inorganic elements in biomass on the pyrolysis mechanism of lignin, density functional theory...  相似文献   
108.
Two‐dimensional (2D) PtSe2 shows the most prominent layer‐dependent electrical properties among various 2D materials and high catalytic activity for hydrogen evolution reaction (HER), and therefore, it is an ideal material for exploring the structure–activity correlations in 2D systems. Here, starting with the synthesis of single‐crystalline 2D PtSe2 with a controlled number of layers and probing the HER catalytic activity of individual flakes in micro electrochemical cells, we investigated the layer‐dependent HER catalytic activity of 2D PtSe2 from both theoretical and experimental perspectives. We clearly demonstrated how the number of layers affects the number of active sites, the electronic structures, and electrical properties of 2D PtSe2 flakes and thus alters their catalytic performance for HER. Our results also highlight the importance of efficient electron transfer in achieving optimum activity for ultrathin electrocatalysts. Our studies greatly enrich our understanding of the structure–activity correlations for 2D catalysts and provide new insight for the design and synthesis of ultrathin catalysts with high activity.  相似文献   
109.
Both experimental and computational studies showed owing to strong π-π stacking interactions, 1-acetylpyrene mainly exists in dimers and molecular aggregates even at low concentrations, which led to the mis-assignment of its monomer emission peaks.  相似文献   
110.
Zhang  Yi  Huang  Peng  Long  Mei  Liu  Song  Yang  Huaming  Yuan  Shuwen  Chang  Shi 《中国科学:化学(英文版)》2019,62(1):58-61
An innovative cancer therapy strategy regarding the interface engineering of kaolinite has been designed. The exposed silanol group facilitates more guest species with high dispersion on the supports. Mn_3O_4 magnetic nanoparticles are uniformly distributed on external surfaces of the Kaolin_(C12N)with the Al–O–Mn bond for the detection of the tumor microenvironment by T1-MRI; Doxorubicin(DOX) are loaded in the interlayer space with the electrostatic interaction for chemo-treating; and KI is coated on the outer layer of the nanocomposites based on the electrostatic interaction for thyroid cancer targeting. The synergetic effects and the treatment mechanism enhanced by the interface engineering, KI@DOX-Mn_3O_4-Kaolin_(C12N)can cause remarkably low cell viability(57%, 200 μg/mL), tumor shrinking(75%, 20 μg/kg), and accumulation into the tumor tissues. The novel kaolinite based drug delivery system is expected to incorporate imaging diagnosis, targeted therapy and drug delivery into one single system for postoperative residual thyroid cancer treatment and observation for metastasis of focal area.  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