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801.
Ihsan Ullah Muhammad Sher Rasheed Ahmad Khera Muhammad Farooq Ibad Christine Fischer 《Tetrahedron》2010,66(10):1874-1884
The [3+3] cyclization of 1,3-bis(silyloxy)-1,3-butadienes with 1-hydroxy-5-silyloxy-hex-4-en-3-ones resulted in the one-pot formation of 3-aryl-3,4-dihydroisocoumarins. The reactions proceeded by regioselective cyclization to give 6-(2-aryl-2-chloroethyl)salicylates, which underwent a silica gel-mediated lactonization. The cyclizations of protected 1-amino-5-silyloxy-hex-4-en-3-ones proved to be not regioselective. 相似文献
802.
Tanveer Hussain Bokhari A. Mushtaq Islam Ullah Khan 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(2):265-271
Production of radioactive scandium by irradiating natural titanium metal in Pakistan Research Reactor-1 was evaluated. The
production rate of 47Sc and other radioactive scandium was estimated. High specific activity 47Sc can be produced by irradiating enriched 47Ti in sufficient quantities needed for therapeutic applications. A new separation technique based on column chromatography
was developed. Neutron irradiated titanium was dissolved in hydrofluoric acid, which was evaporated and taken in distilled
water. The resulting solution was loaded on silica gel column. The radioactive scandium comes out first and the inactive titanium
is removed with 2 M HCl. More than 95% radioactive scandium was recovered, while chemical impurity of titanium determined
by optical emission spectroscopy was less than 0.01 μg/mL in final product. 相似文献
803.
Theoretical study of exohedral chemical functionalization of C48B6N6 with NH3 molecules has been investigated using DFT. It was found that NH3 molecule can be chemically adsorbed on boron sites of C48B6N6, with a charge transfer from NH3 to C48B6N6. Adsorption energy and the quantity of electron charge transfer from latest adsorbed ammonia to C48B6N6 decreased with increasing in the adsorbed NH3 molecules. Despite the strong adsorption energies, electronic properties of C48B6N6 is preserved after modification(s) with NH3 molecule(s) and chemical modification of C48B6N6 with NH3 molecules can be viewed as some kind of safe modification. 相似文献
804.
Ehsan Zahedi 《Physica B: Condensed Matter》2012,407(23):4503-4511
The nonequilibrium Green's function approach in combination with density-functional theory is used to perform quantum mechanical calculations of the electron transport properties of furan and thiophene dimmers. Both the molecular systems have two S-linker and translated into the Gold junction with (1 1 1) surfaces. The studied molecular junctions at zero bias voltage are HOMO-based junctions and currents through these systems are driven by hole transport. The current–voltage characteristics of the both studied molecular junctions illustrate that negative differential resistance (NDR) feature is observed over the bias voltage of 2.0 V. Higher conductivity of fused furan dimmer and NDR character have been explained by the monitoring of the transmission resonance peak across the bias window against varying bias voltages. 相似文献
805.
Afaq Ullah KHAN Faheem SHAH Rafaqat Ali KHAN Bushra ISMAIL Asad Mohammad KHAN Haji MUHAMMAD 《Turkish Journal of Chemistry》2021,45(4):1201
Every year, tuberculosis affects the lungs of millions of people and rifampicin is the commonly used medicine for its treatment due to its antibiotic nature. The frequent use of rifampicin may lead to its increased concentration in the water resources. This research work is focused on the cloud point extraction (CPE) procedure for the preconcentration of rifampicin prior to its determination in water. The UV/vis spectrophotometric method was adapted for the measurement of rifampicin content after the phase separation. Triton-X 100 was used as the nonionic surfactant which contains hydrophilic polyethylene chain feasible for the extraction of analyte. Various analytical parameters that can affect the extraction efficacy were optimized to achieve linearity of the proposed method in the concentration range of 3.54–81.41 mgL–1. The Limit of detection and quantification were 1.261 and 4.212 mgL–1, respectively. The Preconcentration factor was 40 with relative standard deviation (%RSD) of 2.504%. The standard addition methodology was adopted for the validation of this procedure and effectively applied for the determination of rifampicin in real wastewater samples. 相似文献
806.
Nisar Ullah Prinz Sonja Ernst Haslinger Wagar Ahmed Mohammed Arfan Abdul Malik 《Helvetica chimica acta》2001,84(1):157-162
Three new natural products, a lignoid glycoside 1 and two dimeric phenylpropanoids 2 and 3 , along with two known lignans 4 and 5 , were isolated from the BuOH‐ and CHCl3‐soluble fractions of the whole plant of Daphne oleoides (Thymelaeaceae). The structures of the new compounds were established by spectroscopic techniques, including 2D NMR, as 4‐(β‐D ‐glucopyranosyloxy)‐9′‐hydroxy‐3,3′,4′‐trimethoxy‐7′,9‐epoxylignan ( 1 ), (1R,2S,5R,6R)‐6‐(3‐ethyl‐4‐hydroxy‐5‐methoxyphenyl)‐2‐(4‐hydroxy‐3,5‐dimethoxyphenyl)‐3,7‐dioxabicyclo[3.3.0]octane ( 2 ) and (1R,2S,5R,6S)‐2,6‐bis(3‐ethyl‐4‐hydroxy‐5‐methoxyphenyl)‐3,7‐dioxabicyclo[3.3.0]octane ( 3 ). The other lignans were identified as (+)‐pinoresinol O‐(β‐D ‐glucopyranoside) ( 4 ) and (+)‐medioresinol ( 5 ). 相似文献
807.
Munir Ullah Khan Safir Ullah Khan Jiraya Kiriratnikom Shah Zareen Xinghong Zhang 《中国化学快报》2022,33(2):1081-1086
The development of effective and low-energy-consumption catalysts for CO2conversion into high-valueadded products by constructing versatile active sites on the surface of heterogeneous compounds is an urgent and challenging task.In this study,a stable and well-defined heterogeneous cobalt hexacyanocobaltate (Co3[Co(CN)6]2),typical cobalt Prussian blue analogue (Co Co-PBA) modified with tetrabutylammonium bromide (TBAB),is proven to be the superior cata... 相似文献
808.
Studying the excited-state decay process is crucial for materials research because what happens to the excited states determines how effective the materials are for many applications, such as photoluminescence and photocatalysis. The high computational cost, however, limits the use of high-accuracy theoretical approaches for analyzing research systems containing a significant number of atoms. Time-dependent density functional theory is a practical approach to investigate the photorelaxation processes in these systems, as demonstrated in the studies of the excited-state decays of heptazine-water clusters and adenine in water described in this review. Here, we highlight the importance of conical intersections in the excited-state decay processes of these systems using the aforementioned examples. In the heptazine-water and adenine-water systems, these intersections are associated with the photocatalytic water splitting reaction, caused by a barrierless reaction called water to adenine electron-driven proton transfer. We expect the result would be helpful for researching the excited-state decays of graphitic carbon nitride materials and DNA nucleotides. 相似文献
809.
Khan Shahab Ullah 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2023,77(8):1-18
The European Physical Journal D - The spectrum of quadruply ionized bismuth (Bi V) has been investigated in the vacuum ultraviolet region 190–1900 Å. Several bismuth... 相似文献
810.
Ullah Asad Zaman Shahid Hamraz Anila Muzammal Muniba 《The European physical journal. E, Soft matter》2023,46(8):1-8
The European Physical Journal E - In this article, we experimentally investigate the nonlinear behaviour of a viscoplastic film flow down an inclined plane. We focus on the nonlinear instabilities... 相似文献