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   641篇
  免费   16篇
  国内免费   10篇
化学   410篇
晶体学   6篇
力学   13篇
数学   36篇
物理学   202篇
  2023年   4篇
  2022年   11篇
  2021年   6篇
  2020年   10篇
  2019年   13篇
  2018年   9篇
  2017年   9篇
  2016年   24篇
  2015年   12篇
  2014年   20篇
  2013年   46篇
  2012年   29篇
  2011年   43篇
  2010年   25篇
  2009年   25篇
  2008年   32篇
  2007年   36篇
  2006年   38篇
  2005年   33篇
  2004年   28篇
  2003年   25篇
  2002年   14篇
  2001年   10篇
  2000年   8篇
  1999年   6篇
  1998年   9篇
  1997年   6篇
  1996年   10篇
  1995年   5篇
  1994年   11篇
  1993年   10篇
  1992年   9篇
  1991年   3篇
  1990年   3篇
  1988年   5篇
  1987年   10篇
  1986年   4篇
  1985年   3篇
  1984年   8篇
  1983年   7篇
  1982年   6篇
  1981年   6篇
  1980年   9篇
  1979年   4篇
  1978年   5篇
  1977年   4篇
  1975年   3篇
  1973年   2篇
  1967年   1篇
  1966年   1篇
排序方式: 共有667条查询结果,搜索用时 0 毫秒
81.
We have identified novel CE conditions for the separation of 7‐amino‐4‐methylcoumarin‐labeled monosaccharides and oligosaccharides from glycoproteins. Using a neutrally coated capillary and alkaline borate buffer containing hydroxypropylcellulose and ACN, saccharide derivatives form anionic borate complexes, which move from the cathode to the anode in an electric field and are detected near the anodic end. Excess labeling reagents and other fluorescent products remain at the cathodic end. Fluorimetric detection using an LED as a light source enables determination of monosaccharide derivatives with good linearity between at least 0.4 and 400 μM, may correspond to 140 amol to 140 fmol. The lower LOD (S/N = 5) is only 80 nM in the sample solution (ca. 28 amol). The results were comparable to reported values using fluorometric detection LC. The method was also applied to the analysis of oligosaccharides that were enzymatically released from glycoproteins. Fine resolution enables profiling of glycans in glycoproteins. The applicability of the method was examined by applying it to other derivatives labeled with nonacidic tags such as ethyl p‐aminobenzoate‐ and 2‐aminoacridone‐labeled saccharides.  相似文献   
82.
We have developed intense vacuum ultraviolet (VUV) radiation sources for advanced material processing, such as photochemical surface reactions and precise processing on a nanometer scale. We have constructed a new VUV laser system to generate sub-picosecond pulses at the wavelength of 126 nm. A seed VUV pulse was generated in Xe as the 7th harmonic of a 882-nm Ti:sapphire laser. The optimum conversion was achieved at the pressure of 1.2 Torr. The seed pulse will be amplified by the Ar2*\mathrm{Ar}_{2}^{*} media generated by an optical-field-induced ionization Ar plasma produced by the Ti:sapphire laser. We have obtained a gain coefficient of g=0.16 cm−1. Our developing system will provide VUV ultra-short pulses with sub-μJ energy at a repetition rate of 1 kHz.  相似文献   
83.
84.
Journal of Radioanalytical and Nuclear Chemistry - This paper discusses the spatiotemporal variation in atmospheric tritiated water (HTO) concentration near the Fukushima Daiichi Nuclear Power...  相似文献   
85.
A series of experiments is described in which beta-ray asymmetry has been used to determine polarization of heavy-ion reaction products12B and the present status of the studies of polarization phenomena in heavy-ion reactions is reviewed. A large amount of angular momentum sustained by the two colliding nuclei gives rise to polarization phenomena of reaction products. Coupling between the degrees of freedom accompanying the intrinsic and the relative motions is investigated from the systematic behaviour of polarization of reaction products disclosed by the experiments.  相似文献   
86.
In order to evaluate the effect of annealing treatment on the proton conductivity of ??-alumina, the electrical conductivity of Mg-doped polycrystalline ??-alumina kept at 1,873?K under various conditions of the surrounding atmosphere and then cooled in the furnace was measured in the temperature range 1,173?C1,473?K. The H+/D+ isotope effect on the electrical conductivity was also examined under a hydrogen atmosphere at 1,273?K. The protonic conductivity measured at 1,273?K increased with the increase in the activity of oxygen and water vapor in the annealing atmosphere at 1,873?K. It is considered that the solubility limit of magnesium ions in ??-alumina in equilibrium with the small amount of the spinel phase increased with the increase in the activity of oxygen and water vapor at 1,873?K. This enhanced amount of magnesium ions is frozen in a non-equilibrium state to 1,273?K and works as the enriched acceptor dopant for the incorporation of protons.  相似文献   
87.
In this paper, the synthesis and characterization of a series of latent polymeric bis(N‐heterocyclic carbene) (NHC) copper(I) complexes is reported, which can be activated for the copper(I)‐catalyzed azide/alkyne cycloaddition (CuAAC) via ultrasound. To prove the influence of chain length and nature of the polymer towards the activation, poly(isobutylene) (PIB), poly(styrene) (PS) and poly(tetrahydrofuran) (PTHF) are synthesized via living polymerization techniques (LCCP, ATRP, CROP) obtaining different chain lengths (from 2500 to 9000 g/mol), followed by quaternization with N‐methylimidazole, generating the corresponding N‐methylimidazolium‐telechelic polymers. The deprotonation of these macroligands via strong bases like sodium tert‐butoxide (NaOtBu) or potassium hexamethyldisilazide (KHMDS) yields the free N‐heterocyclic carbenes (NHCs), which are used to coordinate to tetrakis(acetonitrile)copper(I) hexafluorophosphate, forming the final polymer‐based mono‐ and bis(N‐methylimidazole‐2‐ylidene) copper(I)X complexes. The structural proof of these complexes is accomplished via 1H‐NMR spectroscopy, MALDI‐TOF‐MS and GPC‐techniques. The activation of the copper(I) biscarbene catalysts by ultrasound is studied by GPC, revealing the cleavage of one shielding NHC‐ligand. The initial catalytic latency and the via ultrasound introduced catalytic activation is successfully demonstrated monitoring a CuAAC “click” reaction of benzyl azide and phenylacetylene by in situ 1H‐NMR spectroscopy introducing thus “click” conversions up to 97%. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3893–3907  相似文献   
88.
Ueda  Chiaki  Okita  Atsushi  Tanaka  Go  Suetake  Noriaki  Uchino  Eiji 《Optical Review》2017,24(3):442-447
Optical Review - A novel color removal method for digital color images is proposed. In this method, differences of colors in an input color image are reflected effectively, and the perceived...  相似文献   
89.
Mesoscopic nanomaterials with a size ranging from a few nanometers to hundreds of nanometers were generated on a metallic thin film by interfering femtosecond (fs) laser processing. Because the nanomaterials seemed to demonstrate liquid behavior, we named their structure nano water drop. The structure is considerably similar to that of a real water drop observed with a high-speed camera. Using the phase shift between interfering beams, a duplicate structure was generated. This is a new surface modification technique, using a top-down approach.  相似文献   
90.
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