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   19332篇
  免费   3136篇
  国内免费   2971篇
化学   13924篇
晶体学   277篇
力学   1170篇
综合类   270篇
数学   2553篇
物理学   7245篇
  2024年   13篇
  2023年   266篇
  2022年   336篇
  2021年   485篇
  2020年   625篇
  2019年   646篇
  2018年   605篇
  2017年   596篇
  2016年   870篇
  2015年   916篇
  2014年   1188篇
  2013年   1444篇
  2012年   1586篇
  2011年   1792篇
  2010年   1409篇
  2009年   1429篇
  2008年   1520篇
  2007年   1400篇
  2006年   1323篇
  2005年   1161篇
  2004年   921篇
  2003年   726篇
  2002年   876篇
  2001年   618篇
  2000年   489篇
  1999年   395篇
  1998年   283篇
  1997年   231篇
  1996年   211篇
  1995年   152篇
  1994年   158篇
  1993年   114篇
  1992年   111篇
  1991年   103篇
  1990年   71篇
  1989年   91篇
  1988年   71篇
  1987年   54篇
  1986年   28篇
  1985年   32篇
  1984年   16篇
  1983年   14篇
  1982年   6篇
  1981年   10篇
  1980年   10篇
  1979年   6篇
  1978年   14篇
  1977年   3篇
  1976年   4篇
  1957年   3篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
11.
12.
Chang  Mingning  Wang  He  Zheng  Yonglei  Li  Ningning  Chen  Siheng  Wan  Yong  Yuan  Feng  Shao  Weiquan  Xu  Sheng 《Journal of Solid State Electrochemistry》2019,23(2):607-613
Journal of Solid State Electrochemistry - Li1.2Ni1/3Co1/3Mn1/3O2 was synthesized as a cathode material for lithium-ion batteries and coated with various amounts of CoAl2O4 (0–5 wt%)...  相似文献   
13.
Self‐emulsion polymerization (SEP), a green route developed by us for the polymerization of amphiphilic monomers, does not require any emulsifier or an organic solvent except that the water‐soluble initiators such as 2,2′‐azobis[2‐(2‐imidazolin‐2‐yl)propane]dihydrochloride (VA‐044) and potassium persulfate (KPS) are only used. We report here the polymer nanoscaffolds from a number of amphiphilic monomers, which can be used for in situ encapsulation of a variety of nanoparticles. As a demonstration of the efficacy of these nanoscaffolds, the synthesis of a biocompatible hybrid nanoparticle (nanohybrid), prepared by encapsulating Fe3O4 magnetic nanoparticle (Fe3O4 MNPs) in poly(2‐hydroxyethyl methacrylate) in water, for MRI application is presented. The nanohybrid prepared following the SEP in the form of an emulsion does not involve the use of any stabilizing agent, crosslinker, polymeric emulsifier, or surfactant. This water‐soluble, spherical, and stable nanohybrid containing Fe3O4 MNPs of average size 10 ± 2 nm has a zeta potential value of ?41.89 mV under physiological conditions. Magnetic measurement confirmed that the nanohybrid shows typical magnetic behavior having a saturation magnetization (Ms) value of 32.3 emu/g and a transverse relaxivity (r2) value of 29.97 mM?1 s?1, which signifies that it can be used as a T2 contrast agent in MRI. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019  相似文献   
14.
The first alkaline-earth metal tin(II) phosphate, BaSn2(PO4)2, has been discovered, which consists of layered structures constructed from strictly alternating [SnO3]4− and [PO4]3− moieties. This compound is expected to have a large birefringence with Δn≈0.071 at 1064 nm, owing to the presence of stereochemically active lone pair metal cations.  相似文献   
15.
零误差计算     
研究采用有误差的数值计算来获得无误差的准确值具有重要的理论价值和应用价值.这种通过近似的数值方法获得准确结果的计算被称为零误差计算.本文首先指出,只有一致离散集合中的数才能够开展零误差计算,即有非零隔离界的数集,这也是"数"可以进行零误差计算的一个充要条件.以此为基本出发点,本文分析代数数零误差计算的最低理论精度,该精度对应于恢复近似代数数的准确值时必要的误差控制条件,但由于所采用恢复算法的局限性,这一理论精度往往不能保证成功恢复出代数数的准确值.为此,本文给出采用PSLQ (partial-sum-LQ-decomposition)算法进行代数数零误差计算所需的精度控制条件,与基于LLL (Lenstra-Lenstra-Lovász)算法相比,该精度控制条件关于代数数次数的依赖程度由二次降为拟线性,从而可降低相应算法的复杂度.最后探讨零误差计算未来的发展趋势.  相似文献   
16.
Yin  Weidi  Cheng  Songsong  Wei  Yiheng  Shuai  Jianmei  Wang  Yong 《Numerical Algorithms》2019,82(1):201-222
Numerical Algorithms - This paper comes up with a stable bias-compensated fractional order normalized least mean square (BC-FONLMS) algorithm with noisy inputs. This kind of bias-compensated...  相似文献   
17.
18.
In this study, the synthesis of TaN nanosheets and their application in theranostic agents is reported. After coating polyethylene glycol (PEG) on the TaN nanosheets, the as-synthesized PEG-modified TaN nanosheets (TaN-PEG) show good stability and biocompatibility. Because of their high absorbance in the near-IR region, TaN-PEG can be utilized as photoacoustic imaging contrast agents for tumor imaging. Moreover, TaN-PEG has significant photothermal conversion performance, exhibiting effective laser-induced tumor ablation capability. The TaN-PEG possessing excellent photoacoustic contrast effect and photothermal properties thus have great promise in theranostic applications, especially imaging-guided cancer treatment.  相似文献   
19.
Structural Chemistry - Quinoline- and acridine-based drugs are widely used as anti-breast cancer agents. These drugs act through various mechanisms of action; for example, neratinib acts on...  相似文献   
20.
Although tremendous efforts have been devoted to understanding the origin of boosted charge storage on heteroatom-doped carbons, none of the present studies has shown a whole landscape. Herein, by both experimental evidence and theoretical simulation, it is demonstrated that heteroatom doping not only results in a broadened operating voltage, but also successfully promotes the specific capacitance in aqueous supercapacitors. In particular, the electrolyte cations adsorbed on heteroatom-doped carbon can effectively inhibit hydrogen evolution reaction, a key step of water decomposition during the charging process, which broadens the voltage window of aqueous electrolytes even beyond the thermodynamic limit of water (1.23 V). Furthermore, the reduced adsorption energy of heteroatom-doped carbon consequently leads to more stored cations on the heteroatom-doped carbon surface, thus yielding a boosted charge storage performance.  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