全文获取类型
收费全文 | 928篇 |
免费 | 61篇 |
国内免费 | 6篇 |
专业分类
化学 | 608篇 |
晶体学 | 7篇 |
力学 | 38篇 |
综合类 | 1篇 |
数学 | 91篇 |
物理学 | 250篇 |
出版年
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 13篇 |
2019年 | 22篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 25篇 |
2015年 | 33篇 |
2014年 | 31篇 |
2013年 | 46篇 |
2012年 | 75篇 |
2011年 | 70篇 |
2010年 | 43篇 |
2009年 | 56篇 |
2008年 | 41篇 |
2007年 | 44篇 |
2006年 | 45篇 |
2005年 | 38篇 |
2004年 | 31篇 |
2003年 | 18篇 |
2002年 | 26篇 |
2001年 | 17篇 |
2000年 | 19篇 |
1999年 | 23篇 |
1998年 | 8篇 |
1997年 | 17篇 |
1996年 | 14篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 13篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1974年 | 7篇 |
1973年 | 4篇 |
1970年 | 4篇 |
1969年 | 3篇 |
排序方式: 共有995条查询结果,搜索用时 217 毫秒
811.
We propose an optical compensator configuration with switchable modes by combining the polymer stabilized liquid crystal (PSLC) technology with the novel electrode design. It could be applied to a fixed-focus lens module for providing the defocus compensation of an optical imaging system. The device has two operation modes that can be switched by the electrode connection and provide respective optical retardation effects. It was designed by using the optical simulation tool and fabricated by using the standard photolithographic processes, the liquid crystal (LC) cell assembly procedure, and the particular ultra-violet (UV) exposure steps. The device was implemented and experimental results qualitatively showed its feasibility for realizing the capability of switching different compensation modes. 相似文献
812.
Abstract This study considers the effect of a slanted side cooling wall that has varying inclination angles on the development of thermosolutal convection during the solidification of a super-eutectic aqueous ammonium chloride (NH4Cl-H2O) solution. The shadowgraph and particle image velocimetry techniques were employed to observe the flow development and measure the flow velocity during solidification. The transient temperature distribution within the test cell was also measured by type-T thermocouples. Experimental results reveal that a more slanted side cooling wall accelerated the “filling-box” process, thus it could cause more serious A-segregates and material defects in the solidified ingot. 相似文献
813.
Jeng‐Yueh Shieh Shih‐Peng Yang Mei‐Feng Wu Chun‐Shan Wang 《Journal of polymer science. Part A, Polymer chemistry》2004,42(11):2589-2600
For the purpose of increasing the mobility of residual bisphenol A dicyanate ester (BADCY) during the final stage of curing and achieving a complete reaction of cyanate groups, a small quantity of monofunctional phenol was added to BADCY to form an imidocarbonate, or a small quantity of monofunctional cyanate esters was added to form cyanate ester copolymers. The proposed structures were confirmed with Fourier transform infrared, elemental analysis, mass spectrometry, and NMR spectroscopy. The thermal properties of the cured cyanate esters were measured with dynamic mechanical analysis, thermogravimetric analysis, and dielectric analysis. These data were compared with those for the cured BADCY resin. The cured modified cyanate esters exhibited a lower dielectric constant, a lower dissipation factor, and lower moisture absorption than the cured BADCY system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2589–2600, 2004 相似文献
814.
Y. Shih 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):485-493
One of the most surprising consequences of quantum mechanics is the entanglement of two or more distant particles. Even though
we still have questions in regard to fundamental issues of the entangled quantum systems, quantum entanglement has started
to play important roles in practical applications. Quantum imaging is one of the hot topics. Quantum imaging has many interesting
features which are useful for different applications. For example, quantum imaging can be nonlocal, which is useful for secure
two-dimensional information transfer. Quantum imaging can reach a much higher spatial resolution comparing with classical
imaging, even beyond the diffraction limit, which is useful for lithography and other microsystem fabrication technology.
It is not a violation of the uncertainty principle, however, a quantum mechanical multi-particle phenomenon.
Received 30 August 2002 / Received in final form 11 November 2002 Published online 4 February 2003 相似文献
815.
A novel organic‐inorganic hybrid electrolyte based on poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) triblock copolymer (Pluronic P123) complexed with LiClO4 via the co‐condensation of an epoxy trialkoxysilane and tetraethylorthosilicate was prepared. Characterization was made by a variety of techniques including powder X‐ray diffraction, AC impedance, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and multinuclear solid state NMR measurements. The hybrid with [O]/[Li] = 16 exhibited a mesophase with a certain degree of ordering, which arose by the self‐assembly of P123 with the silica network. The P123 triblock copolymer acts as a structure‐directing surfactant to organize with silica networks and as a polymer matrix to dissolve alkali lithium salts as well. The DSC results indicated the formation of transient crosslinking between Li+ ions and the ether oxygens of the EO and PO segments, resulting in an increase the Tg with increasing salt concentrations. Variable temperature 7Li‐{1H} MAS NMR spectra revealed the presence of two different local environments for lithium cations, probably due to the lithium cations in the polymer‐rich domain and in the silica‐rich domain, respectively. A combination of XRD and conductivity results suggests that the drastically enhanced conductivity for the ordered hybrid electrolyte is closely related to the formation of mesophase, which may provide unique Li+ conducting pathways. 相似文献
816.
Shih-Yuan Lin Chih-Ming Wang Po-Tsung Hsieh Ying-Chung Chen Chan-Chih Liu Shun-Chou Shih 《Colloid and polymer science》2009,287(11):1355-1358
A novel gel polymer electrolyte (GPE) that contains Li+ ions was fabricated. An appropriate amount of ethyl cellulose (EC) was added to 1 M lithium perchlorate in propylene carbonate to prepare the GPE. The ionic conductivity (σ) of the GPE depends on the EC content, and the GPE with an EC content of 4.5 wt.% exhibits a maximum σ of 6.47 mS/cm, a viscosity of 141 mPa?s, and a transmittance of over 80% (visible region) at room temperature. High σ and transparent GPE can be obtained. In this work, the EC was used as natural thickener to enhance the viscosity of the liquid-state electrolyte and could improve the leakage of electrolyte solution. 相似文献
817.
Using a solution of hexafluorotitanic acid and boric acid, high-refractive-index and high-dielectric-constant films can be
deposited on silicon substrates. The constituents of the films were Ti, Si and O analyzed by secondary-ion mass spectroscopy,
which indicates that the structure of the films is TixSi(1-x)Oy. The Ti/Si ratio can be modulated by the mole concentration of boric acid. The leakage current density and dielectric constant
of the deposited films can be improved by thermal annealing in N2 ambience.
Received: 16 November 2000 / Accepted: 2 March 2001 / Published online: 23 May 2001 相似文献
818.
A large-volume sample injection (> 5 microL) with an extremely high theoretical plate number (N > 10(7)) was achieved when the sweeping-MEKC mode and a coupled-capillary (100 - 50 microm i.d.) were simultaneously used in a capillary electrophoresis (CE) separation. A low-cost and compact violet-LED ( approximately 2 mW) was used as the fluorescence excitation source. As a result, the theoretical plate numbers of the detected peaks (two model compounds: naphthalene-2,3-dicarboxaldehyde derivatized-dopamine and -norepinephrine) were 1.0 x 10(7) and 7.4 x 10(6), respectively. The limits of detection (at S/N = 3) of these were determined to be 2.8 x 10(-10) M (92 ppt) and 2.3 x 10(-10) M (83 ppt), respectively. 相似文献
819.
Jasmine Chia-hsin Shih Laure BourgeoisKiyonori Suzuki Jose S. Garitaonandia 《Journal of magnetism and magnetic materials》2006
In order to clarify the origin of the high thermal stability of the microstructure in bcc-Fe/amorphous two-phase nanocrystalline soft magnetic materials, we have investigated the changes in the magnetic and microstructural properties upon isothermal annealing at 898 K for an Fe89Zr7B3Cu1 alloy by means of transmission electron microscopy, Mössbauer spectroscopy and DC magnetometry. The mean grain size was found to remain almost unchanged at the early stage of annealing. However, rapid grain coarsening was evident at an annealing time of 7.2 ks where the intergranular amorphous phase begins to crystallize into Fe23Zr6. The grain growth process with a kinetic exponent of 1.6 is observed for the growth process beyond this annealing time, reflecting the disappearance of the intergranular amorphous phase. Our results confirm that the thermal stability of the bcc-Fe/amorphous two-phase nanocrystalline soft magnetic alloys is governed by the residual amorphous phase. 相似文献
820.
Affinity‐Driven Covalent Modulator of the Glyceraldehyde‐3‐Phosphate Dehydrogenase (GAPDH) Cascade
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jeffy Chern Chun‐Ping Lu Zhanxiong Fang Ching‐Ming Chang Kuo‐Feng Hua Yi‐Ting Chen Cheng Yang Ng Yi‐Lin Sophia Chen Yulin Lam Shih‐Hsiung Wu 《Angewandte Chemie (International ed. in English)》2018,57(24):7040-7045
Traditional medicines provide a fertile ground to explore potent lead compounds, yet their transformation into modern drugs is fraught with challenges in deciphering the target that is mechanistically valid for its biological activity. Herein we reveal that (Z)‐(+)‐isochaihulactone ( 1 ) exhibited significant inhibition against multiple‐drug‐resistant (MDR) cancer cell lines and mice xenografts. NMR spectroscopy showed that 1 resisted an off‐target thiolate, thus indicating that 1 was a target covalent inhibitor (TCI). By identifying the pharmacophore of 1 (α,β‐unsaturated moiety), a probe derived from 1 was designed and synthesized for TCI‐oriented activity‐based proteome profiling. By MS/MS and computer‐guided molecular biology approaches, an affinity‐driven Michael addition of the noncatalytic C247 residue of GAPDH was found to control the “ON/OFF” switch of apoptosis through non‐canonically nuclear GAPDH translocation, which bypasses the common apoptosis‐resistant route of MDR cancers. 相似文献