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   75403篇
  免费   13190篇
  国内免费   7593篇
化学   52506篇
晶体学   690篇
力学   4913篇
综合类   365篇
数学   8655篇
物理学   29057篇
  2024年   181篇
  2023年   1602篇
  2022年   2328篇
  2021年   2765篇
  2020年   3224篇
  2019年   2991篇
  2018年   2592篇
  2017年   2373篇
  2016年   3640篇
  2015年   3486篇
  2014年   4176篇
  2013年   5446篇
  2012年   6889篇
  2011年   7023篇
  2010年   4699篇
  2009年   4430篇
  2008年   4814篇
  2007年   4313篇
  2006年   3927篇
  2005年   3279篇
  2004年   2525篇
  2003年   2022篇
  2002年   1844篇
  2001年   1556篇
  2000年   1430篇
  1999年   1635篇
  1998年   1367篇
  1997年   1365篇
  1996年   1351篇
  1995年   1110篇
  1994年   968篇
  1993年   806篇
  1992年   698篇
  1991年   603篇
  1990年   516篇
  1989年   393篇
  1988年   340篇
  1987年   279篇
  1986年   261篇
  1985年   208篇
  1984年   144篇
  1983年   103篇
  1982年   82篇
  1981年   71篇
  1980年   65篇
  1979年   32篇
  1978年   30篇
  1977年   40篇
  1976年   30篇
  1973年   28篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
71.
72.
73.
A high‐throughout bioanalytical method based on salting‐out‐assisted liquid/liquid extraction (SALLE) method with acetonitrile and mass spectrometry‐compatible salts followed by LC‐MS/MS analysis of trimetazidine in rat plasma is presented. It required only 50 μL of plasma and allows the use of minimal volumes of organic solvents. The seamless interface of SALLE and LC‐MS eliminated the drying‐down step and the extract was diluted and injected into an LC‐MS/MS system with a cycle time of 2.5 min/sample. The retention times of trimetazidine and IS were approximately 1.1 and 1.7 min, respectively. Calibration curves were linear over the concentration range of 0.1–100 ng/mL, which can be extended to 500 ng/mL by dilution. The intra‐ and inter‐batch precision, accuracy and the relative standard deviation were all <15%. This method was successfully applied to determine trimetazidine concentrations in rat plasma. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
74.
75.
In this Letter,a novel system for adaptively correcting the phase of a dynamic multimode beam is proposed.While using merely one spatial light modulator,the phase measurement of the first-order diffraction pattern and the correction of the zeroth diffraction order are simultaneously realized.The real-time experimental result is obtained at a control rate of 10 Hz.The power-in-the-bucket value is improved from 38.5%to 61.8%,even with fundamental mode content that is consistently below 30%.To the best of our knowledge,this is the first implementation of real-time adaptive correction of the entire multimode beam.  相似文献   
76.
Floquet engineering appears as a new protocol for designing topological states of matter,and features anomalous edge modes pinned at quasi-energy π/T with vanished topological index.We propose how to predict the anomalous edge modes via the bulk Hamiltonian in frequency space,and use Zak phase to quantitatively index the topological properties.The above methods are clarified by the example of time periodic Kitaev chain with chemical potential of harmonic driving and pulse driving,and topological phase transitions are manifested at different driving frequencies.  相似文献   
77.
78.
79.
In order to improve the signal-to-noise ratio and mitigate the damage of noise to the communication quality,an effective interference suppression algorithm,which is based on the improved density-based spatial clustering of applications with noise algorithms,is proposed for visible light communication systems using the complementary metal–oxide–semiconductor image sensor as the receiver.Experimental results show that the algorithm can learn the region where the payload data is located,filter out the noise data,and greatly decrease the interference.The effect of the algorithm is also studied through bit error ratio performance.  相似文献   
80.
The discharge of diverse pollutants has led to a complex water environment and posed a huge health threat to humans and animals. Self-propelled micromotors have recently attracted considerable attention for efficient water remediation due to their strong localized mass transfer effect. However, a single functionalized component is difficult to tackle with multiple contaminants and requires to combine different decontamination effects together. Here, we introduced a multifunctional micromotor to implement the adsorption and degradation roles simultaneously by integrating the poly(aspartic acid) (PASP) adsorbent with a MnO2-based catalyst. The as-prepared micromotors are well propelled in contaminated waters by MnO2 catalyzing hydrogen peroxide. In addition, the catalytic ramsdellite MnO2(R-MnO2) inner layer is decorated with Fe2O3 nanoparticles to improve their catalytic performance, contributing to an excellent degradation ability with 90% tetracycline (TC) removal in 50 minutes by enhanced Fenton-like reactions. Combining the attractive adsorption capability of poly (aspartic acid) (PASP), the composite micromotors offer an efficient removal of heavy metal ions in short time. Moreover, the designed micromotors are able to simultaneously remove antibiotic and heavy metals in mixed contaminants circumstance just in single treatment. This multifunctional micromotor with distinctive decontamination ability exhibits a promising prospective in treating multiple pollutants in the future.  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