全文获取类型
收费全文 | 3038篇 |
免费 | 96篇 |
国内免费 | 21篇 |
专业分类
化学 | 2044篇 |
晶体学 | 20篇 |
力学 | 118篇 |
数学 | 525篇 |
物理学 | 448篇 |
出版年
2023年 | 27篇 |
2022年 | 49篇 |
2021年 | 45篇 |
2020年 | 50篇 |
2019年 | 77篇 |
2018年 | 45篇 |
2017年 | 28篇 |
2016年 | 85篇 |
2015年 | 95篇 |
2014年 | 111篇 |
2013年 | 156篇 |
2012年 | 215篇 |
2011年 | 247篇 |
2010年 | 157篇 |
2009年 | 135篇 |
2008年 | 172篇 |
2007年 | 186篇 |
2006年 | 191篇 |
2005年 | 187篇 |
2004年 | 176篇 |
2003年 | 112篇 |
2002年 | 116篇 |
2001年 | 44篇 |
2000年 | 41篇 |
1999年 | 24篇 |
1998年 | 31篇 |
1997年 | 28篇 |
1996年 | 24篇 |
1995年 | 25篇 |
1994年 | 10篇 |
1993年 | 23篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 11篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 20篇 |
1983年 | 13篇 |
1982年 | 19篇 |
1981年 | 13篇 |
1980年 | 22篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 10篇 |
排序方式: 共有3155条查询结果,搜索用时 15 毫秒
61.
62.
Annija Lace Aideen Byrne Simon Bluett Laurent Malaquin Vincent Raimbault Remi Courson Zain Hayat Breda Moore Eoin Murray 《Journal of separation science》2022,45(5):1042-1050
An ion chromatography system employing a low-cost three-dimensional printed absorbance detector for indirect ultraviolet detection towards portable phosphate analysis of environmental and industrial waters has been developed. The optical detection cell was fabricated using stereolithography three-dimensional printing of nanocomposite material. Chromatographic analysis and detection of phosphate were carried out using a CS5A 4 × 250 mm analytical column with indirect ultraviolet detection using a 255 nm light-emitting diode. Isocratic elution using a 0.6 mM potassium phthalate eluent combined with 1.44 mM sodium bicarbonate was employed at a flow rate of 0.75 mL/min. A linear calibration range of 0.5 to 30 mg/L PO43− applicable to environmental and wastewater analysis was achieved. For retention time and peak area repeatability, relative standard deviation values were 0.68 and 4.09%, respectively. Environmental and wastewater samples were analyzed with the optimized ion chromatography platform and the results were compared to values obtained by an accredited ion chromatograph. For the analysis of environmental samples, relative errors of <14 % were achieved. Recovery analysis was also carried out on both freshwater and wastewater samples and recovery results were within the acceptable range for water analysis using standard ion chromatography methods. 相似文献
63.
We report the operation of a 50 mW continuous-wave quantum cascade laser (QCL) in the 9.2 microm range, phase locked to a single-mode CO(2) laser with a tunable frequency offset. The wide free-running emission spectrum of the QCL (3-5 MHz) is strongly narrowed down to the kilohertz range, making it suitable for high-resolution molecular spectroscopy. 相似文献
64.
65.
The numerical approximation of one-dimensional relativistic Dirac wave equations is considered within the recent framework consisting in deriving local scattering matrices at each interface of the uniform Cartesian computational grid. For a Courant number equal to unity, it is rigorously shown that such a discretization preserves exactly the \(L^2\) norm despite being explicit in time. This construction is well-suited for particles for which the reference velocity is of the order of \(c\), the speed of light. Moreover, when \(c\) diverges, that is to say, for slow particles (the characteristic scale of the motion is non-relativistic), Dirac equations are naturally written so as to let a “diffusive limit” emerge numerically, like for discrete 2-velocity kinetic models. It is shown that an asymptotic-preserving scheme can be deduced from the aforementioned well-balanced one, with the following properties: it yields unconditionally a classical Schrödinger equation for free particles, but it handles the more intricate case with an external potential only conditionally (the grid should be such that \(c \Delta x\rightarrow 0\)). Such a stringent restriction on the computational grid can be circumvented easily in order to derive a seemingly original Schrödinger scheme still containing tiny relativistic features. Numerical tests (on both linear and nonlinear equations) are displayed. 相似文献
66.
Dr. Romain Ramozzi Dr. Nicolas Chéron Dr. Laurent El Kaïm Dr. Laurence Grimaud Dr. Paul Fleurat‐Lessard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(29):9094-9099
Following our previous mechanistic studies of multicomponent Ugi‐type reactions, theoretical calculations have been performed to predict the efficiency of new substrates in Ugi–Smiles couplings. First, as predicted, 2,4,6‐trichlorophenol experimentally gave the corresponding aryl‐imidate. Theoretical predictions of nitrosophenols as good acidic partners were then successfully confirmed by experiments. In the latter case, the reaction offers a new access to benzimidazoles. 相似文献
67.
Functionalization of a Ruthenium–Diacetylide Organometallic Complex as a Next‐Generation Push–Pull Chromophore 下载免费PDF全文
Samuel De Sousa Dr. Laurent Ducasse Dr. Brice Kauffmann Prof. Thierry Toupance Dr. Céline Olivier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(23):7017-7024
The design and preparation of an asymmetric ruthenium–diacetylide organometallic complex was successfully achieved to provide an original donor–π–[M]–π–acceptor architecture, in which [M] corresponds to the [Ru(dppe)2] (dppe: bisdiphenylphosphinoethane) metal fragment. The charge‐transfer processes occurring upon photoexcitation of the push–pull metal–dialkynyl σ complex were investigated by combining experimental and theoretical data. The novel push–pull complex, appropriately end capped with an anchoring carboxylic acid function, was further adsorbed onto a semiconducting metal oxide porous thin film to serve as a photosensitizer in hybrid solar cells. The resulting photoactive material, when embedded in dye‐sensitized solar cell devices, showed a good spectral response with a broad incident photon‐to‐current conversion efficiency profile and a power conversion efficiency that reached 7.3 %. Thus, this material paves the way to a new generation of organometallic chromophores for photovoltaic applications. 相似文献
68.
A Cationic Zinc Hydride Cluster Stabilized by an N‐Heterocyclic Carbene: Synthesis,Reactivity, and Hydrosilylation Catalysis 下载免费PDF全文
Dr. Arnab Rit Dr. Alessandro Zanardi Dr. Thomas P. Spaniol Prof. Dr. Laurent Maron Prof. Dr. Jun Okuda 《Angewandte Chemie (International ed. in English)》2014,53(48):13273-13277
The trinuclear cationic zinc hydride cluster [(IMes)3Zn3H4(THF)](BPh4)2 ( 1 ) was obtained either by protonation of the neutral zinc dihydride [(IMes)ZnH2]2 with a Brønsted acid or by addition of the putative zinc dication [(IMes)Zn(THF)]2+. A triply bridged thiophenolato complex 2 was formed upon oxidation of 1 with PhS? SPh. Protonolysis of 1 by methanol or water gave the corresponding trinuclear dicationic derivatives. At ambient temperature, 1 catalyzed the hydrosilylation of aldehydes, ketones, and nitriles. Carbon dioxide was also hydrosilylated under forcing conditions when using (EtO)3SiH, giving silylformate as the main product. 相似文献
69.
Gerardo Salinas Alice L. Dauphin Camille Colin Elena Villani Stphane Arbault Laurent Bouffier Alexander Kuhn 《Angewandte Chemie (International ed. in English)》2020,59(19):7508-7513
Miniaturized autonomous chemo‐electronic swimmers, based on the coupling of spontaneous oxidation and reduction reactions at the two poles of light‐emitting diodes (LEDs), are presented as chemotactic and magnetotactic devices. In homogeneous aqueous media, random motion caused by a bubble‐induced propulsion mechanism is observed. However, in an inhomogeneous environment, the self‐propelled devices exhibit positive chemotactic behavior, propelling themselves along a pH or ionic strength gradient (?pH and ?I, respectively) in order to reach a thermodynamically higher active state. In addition, the intrinsic permanent magnetic moment of the LED allows self‐orientation in the terrestrial magnetic field or following other external magnetic perturbations, which enables a directional motion control coupled with light emission. The interplay between chemotaxis and magnetotaxis allows fine‐tuning of the dynamic behavior of these swimmers. 相似文献
70.
Remote Actuation of a Light-Emitting Device Based on Magnetic Stirring and Wireless Electrochemistry
Alice L. Dauphin Dr. Stéphane Arbault Prof. Dr. Alexander Kuhn Prof. Dr. Neso Sojic Dr. Laurent Bouffier 《Chemphyschem》2020,21(7):600-604
We propose a straightforward access to a rotating light-emitting device powered by wireless electrochemistry. A magnetic stirrer is used to rotate a light-emitting diode (LED) due to the intrinsic magnetic properties of the tips that contain iron. At the same time, the LED is submitted to an electric field and acts as a bipolar electrode. The electrochemical processes that are coupled on both extremities of the LED drive an electron flow across the device, resulting in light emission. The variation of the LED alignment in time enables an alternating light emission that is directly controlled by the rotation rate. The stirring also enables a continuous mixing of the electrolyte that improves the stability of the output signal. Finally, the LED brightness can readily reveal a change of chemical composition in the electrolyte solution. 相似文献