首页 | 官方网站   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   117239篇
  免费   19503篇
  国内免费   14691篇
数理化   151433篇
  2024年   260篇
  2023年   2194篇
  2022年   2876篇
  2021年   3899篇
  2020年   4610篇
  2019年   4500篇
  2018年   4060篇
  2017年   3740篇
  2016年   5521篇
  2015年   5454篇
  2014年   6686篇
  2013年   8774篇
  2012年   10634篇
  2011年   11037篇
  2010年   7889篇
  2009年   7601篇
  2008年   8070篇
  2007年   7139篇
  2006年   6779篇
  2005年   5732篇
  2004年   4484篇
  2003年   3618篇
  2002年   3409篇
  2001年   2814篇
  2000年   2427篇
  1999年   2405篇
  1998年   1978篇
  1997年   1718篇
  1996年   1702篇
  1995年   1508篇
  1994年   1374篇
  1993年   1117篇
  1992年   970篇
  1991年   857篇
  1990年   700篇
  1989年   548篇
  1988年   413篇
  1987年   355篇
  1986年   352篇
  1985年   291篇
  1984年   201篇
  1983年   167篇
  1982年   137篇
  1981年   94篇
  1980年   69篇
  1979年   36篇
  1978年   29篇
  1976年   24篇
  1975年   25篇
  1957年   30篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
71.
72.
As a new type of quantum dots (QDs), hexagonal boron nitride quantum dots (BNQDs) exhibit promising potential in the applications of disease diagnosis, fluorescence imaging, biosensing, metal ion detection, and so on, because of their remarkable chemical stability, excellent biocompatibility, low cytotoxicity, and outstanding photoluminescence properties. However, the large-scale fabrication of homogeneous BNQDs still remains challenging. In this article, the properties and common fabrication methods of BNQDs are summarized based on the recent research progress. Then, the corresponding yields, morphologies, and fabrication mechanisms of these as-obtained BNQDs are discussed in detail. Moreover, the applications of these as-obtained BNQDs in different fields are also discussed. This article is expected to inspire new methods and improvements to achieve large-scale fabrication of homogeneous BNQDs, which will enable their practical applications in future.  相似文献   
73.
Journal of Thermal Analysis and Calorimetry - Artificial neural network/kriging interpolation method optimization method which is evaluated concerned the hybrid nanofluid composed of iron oxide...  相似文献   
74.
Three‐dimensional (3D) nanometal films serving as current collectors have attracted much interest recently owing to their promising application in high‐performance supercapacitors. In the process of the electrochemical reaction, the 3D structure can provide a short diffusion path for fast ion transport, and the highly conductive nanometal may serve as a backbone for facile electron transfer. In this work, a novel polypyrrole (PPy) shell@3D‐Ni‐core composite is developed to enhance the electrochemical performance of conventional PPy. With the introduction of a Ni metal core, the as‐prepared material exhibits a high specific capacitance (726 F g?1 at a charge/discharge rate of 1 A g?1), good rate capability (a decay of 33 % in Csp with charge/discharge rates increasing from 1 to 20 A g?1), and high cycle stability (only a small decrease of 4.2 % in Csp after 1000 cycles at a scan rate of 100 mV s?1). Furthermore, an aqueous symmetric supercapacitor device is fabricated by using the as‐prepared composite as electrodes; the device demonstrates a high energy density (≈21.2 Wh kg?1) and superior long‐term cycle ability (only 4.4 % and 18.6 % loss in Csp after 2000 and 5000 cycles, respectively).  相似文献   
75.
A new spectral problem is proposed, and nonlinear differential equations of the corresponding hierarchy are obtained. With the help of the nonlinearization appr...  相似文献   
76.
For the orthosymplectic Lie superalgebra ◂⋅▸OSP(2,2), we choose a set of basis matrices. A linear combination of those basis matrices presents a spatial spectral matrix. The compatible condition of the spatial part and the corresponding temporal parts of the spectral problem leads to a generalized super AKNS (GSAKNS) hierarchy. By making use of the supertrace identity, the obtained GSAKNS hierarchy can be written as the super bi-Hamiltonian structures.  相似文献   
77.
Photoactivated chemotherapy (PACT) has appealing merits over traditional chemotherapy as well as photodynamic therapy (PDT) by virtue of its spatial and temporal control on drug activity and oxygen-independent mechanisms of action. However, the short photoactivation wavelengths, e.g., visible light–activated Ru(II)-based PACT agents, limit the clinical application severely. In this work, a facile construction of supramolecular nanoparticles from a poly(ethylene glycol) (PEG)-modified [Ru(dip)2(py-SO3)]+ (abbreviated as Ru-PEG, dip = 4,7-diphenyl-1,10-phenanthroline, py-SO3 = pyridine-2-sulfonate) and 1,3-phenylenebis(pyren-1-ylmethanone) (BP) is shown. While Ru-PEG may undergo photoinduced ligand dissociation and release anticancer species of [Ru(dip)2(H2O)2]2+, BP has extremely large two-photon absorption cross sections (δ2) in the NIR region and intense fluorescence over the wavelengths where Ru-PEG has strong absorption. Thus, two-photon excitation of BP followed by an efficient Förster resonance energy transfer (FRET) from BP to Ru-PEG may lead to a potent inactivation against cisplatin-resistant cancer cells and 3D multicellular tumor spheroids (MCTSs). The residue fluorescence of BP also allows the cellular uptake of the particles to be visualized. This work provides a universal and convenient strategy to realize theranostic PACT in the ideal phototherapeutic window of 650–900 nm.  相似文献   
78.
79.
A new approach has been developed to improve SO2 sorption by cyano‐containing ionic liquids (ILs) through tuning the basicity of ILs and cyano–sulfur interaction. Several kinds of cyano‐containing ILs with different basicity were designed, prepared, and used for SO2 capture. The interaction between these cyano‐containing ILs and SO2 was investigated by FTIR and NMR methods. Spectroscopic investigations and quantum chemical calculations showed that dramatic effects on SO2 capacity originate from the basicity of the ILs and enhanced cyano–sulfur interaction. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the ILs. This efficient and reversible process, achieved by tuning the basicity of ILs, is an excellent alternative to current technologies for SO2 capture.  相似文献   
80.
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-23

京公网安备 11010802026262号