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991.
Saman Babaie–Kafaki Reza Ghanbari 《Numerical Functional Analysis & Optimization》2017,38(9):1115-1124
Based on a singular value analysis on an extension of the Polak–Ribière–Polyak method, a nonlinear conjugate gradient method with the following two optimal features is proposed: the condition number of its search direction matrix is minimum and also, the distance of its search direction from the search direction of a descent nonlinear conjugate gradient method proposed by Zhang et al. is minimum. Under proper conditions, global convergence of the method can be achieved. To enhance e?ciency of the proposed method, Powell’s truncation of the conjugate gradient parameters is used. The method is computationally compared with the nonlinear conjugate gradient method proposed by Zhang et al. and a modified Polak–Ribière–Polyak method proposed by Yuan. Results of numerical comparisons show e?ciency of the proposed method in the sense of the Dolan–Moré performance profile. 相似文献
992.
Maysam Habibi Azizollah Habibi Saber Hakimi Nasab Hadi Dolati Seyedeh Mahbobeh Mahdavi 《Journal of heterocyclic chemistry》2017,54(3):1880-1886
Hexamethylenetetramine (HMTA) catalyzes synthesis of new polyfunctionalized 4H‐pyrans by reaction of aromatic aldehyde, malononitrile, and β‐keto esters via one‐pot three‐component procedure in water medium. Addition of reactants was performed by two methods led to achieve similar results. Using HMTA in catalytic amount not only represents the economic face of the reaction, but also due to the use of water, a green and safe reaction condition is organized. Thus, the current strategy provides the benefits of high productivity, convenient operation, and environmental friendliness. Structure of all products was proved by elemental analysis, IR, 1H‐NMR, and 13C‐NMR spectroscopy. 相似文献
993.
Hossein Reza Darabi Ehsan Khatamifar Ali Sharifi Kioumars Aghapoor Khosrow Jadidi 《合成通讯》2017,47(5):428-434
The McMurry coupling of a bis-salisaldehyde 3a with methyl linker as the smallest member of its alkyl series is known to give the remarkably lower yield of the corresponding stilbenophanes. The half part of this molecule, unlike bigger analogues, is a good leaving group which affordsthreo isomer of 4H, 4′H–4,4′-bibenzo[d][1,3]dioxine 4 in high diastereoisomeric ratio (99>). A further study showed that the formation of this key by-product is the reason for formation of other by-products, namely, 5a,10b-dihydrobenzofuro[2,3-b]benzofuran 9 and 2-(2,3-dihydrobenzofuran-2-yl)phenol 10. Two reaction pathways for the formation of by-products have been proposed which are responsible for the unusual activity of dialdehyde 3a. 相似文献
994.
Two novel correlations are introduced to predict decomposition temperatures of imidazolium‐based energetic ionic liquids. The first simple model is based only on the number of some of atoms in cationic and anionic structures. Meanwhile, a suitable correction term was added in the second correlation to adjust the predicted results for the presence of some specific cation/anion moieties. The measured data of 164 different types of imidazolium‐based energetic ionic liquids were used to derive the new correlations. The calculated mean absolute percent errors (MAPEs) of the first and second models are 6 and 4, respectively. The predicted results have confirmed that insertion of correcting function in the second correlation can provide better estimations. These models were also tested and compared with one of the best available group contribution methods, where group contribution method can be applied, for 17 further imidazolium‐based energetic ionic liquids containing complex molecular structures. Furthermore, the predicted values of MAPEs of the new models are close to that of obtained by group contribution method. 相似文献
995.
Yong Wang Katerina Szokolova Dr. Muhammad Zafir Mohamad Nasir Prof. Zdenek Sofer Prof. Martin Pumera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(30):7330-7338
Group 6 transition metal dichalcogenides (TMDs), such as MoS2 and WS2 have been extensively studied for various applications while few studies have delved into other TMDs such as platinum dichalcogenides. In this work, layered crystalline and amorphous platinum disulfide (PtS2) were synthesized, characterised and their fundamental electrochemical properties were investigated. Both materials exhibited inherent oxidation and reduction reactions which would limit their operating potential window for sensing applications. Amorphous phase materials are considered to be promising electrocatalysts due to the porous, and nanostructured morphology with high concentration of unsaturated active sites. The electrocatalytic performances towards oxygen reduction (ORR) and hydrogen evolution reactions (HER) of crystalline and amorphous PtS2 were analysed. Amorphous PtS2 was found to exhibit superior electrocatalytic performances towards ORR and HER as compared to crystalline PtS2. For HER, amorphous and crystalline PtS2 have overpotential values of 0.30 V and 0.70 V (vs. RHE) at current density of 10 mA cm−2, respectively. The influence of electrochemical reduction pre-treatment on their catalytic behaviours was also investigated. Electrochemical reduction pre-treatment on both crystalline and amorphous PtS2 removed the oxidized sulfate groups and increased the proportion of Pt0 oxidation state which exposed more catalytic sites. As such, these materials were activated and displayed improved ORR and HER performances. Electrochemically reduced amorphous PtS2 outperformed the untreated counterparts and exhibited the best HER performance with overpotential of 0.17 V (vs. RHE) at current density of −10 mA cm−2. These findings provide insights into the electrochemical properties of noble metal PtS2 in both crystalline and amorphous states which can be activated by electrochemical reduction pre-treatment. 相似文献
996.
1,8‐Diazabicyclo[5.4.0]undec‐7‐ene immobilized on silica (SB‐DBU)Cl as a reusable and heterogeneous catalyst was applied for the one‐pot, three‐component synthesis of 2‐amino‐4,8‐dihydropyrano[3,2‐b]pyrane‐3‐carbonitriles and pyridopyrimidines, under solvent‐free conditions. The reaction was carried out at room temperature, and pure products were obtained in high yields and short reaction times (3–7 min). This work introduced an environmentally benign procedure for the synthesis of these classes of biological active compounds. 相似文献
997.
Reza Omidyan Maryam Abbasi Gholamhassan Azimi 《International journal of quantum chemistry》2019,119(3):e25793
New platinum(II) complex with picolinate (pic) and 2-phenyl naphtothiazole (pntl) ligand as the guest material has been designed and its capability for OLED applications have been examined. Also, we have studied the effects of different substitutions (ie, electron-withdrawing and electron donating groups) on naphtothiazole moiety on optovoltaic characters. We have employed density functional theoretical (B3LYP/DFT) methods to reveal the photophysical and structure properties relationships with the typical host material. The valence MO energies, vertical and adiabatic triplet energy, reorganization energy, and triplet exciton generation fraction (χ T) have been extensively studied to exploring high phosphorescence efficiency in OLEDs. It has been predicted that substituted systems are good candidates for OLED applications as well as their parent system. 相似文献
998.
Hamid Reza Gholami Sakineh Asghari Mojtaba Mohseni 《Journal of heterocyclic chemistry》2019,56(5):1505-1513
In this work, the new benzoxazinones and benzoxathiinones were synthesized from reaction of alkyl X‐phenylpropiolates and aminophenol (or 2‐mercaptophenol) in the presence of triphenylphosphine. Their antibacterial activities were studied against Gram‐positive bacteria and Gram‐negative bacteria using the disc diffusion method. The obtained results showed that these compounds are more effective against Gram‐positive bacteria than against Gram‐negative bacteria. Also, evaluation of antioxidant activity of the obtained products showed that they have high to excellent antioxidant activity (79.2–93.6%). 相似文献
999.
Mozhgan Masoudi Mohammad Reza Shahbazi‐Manshadi Mohammad Anary‐Abbasinejad 《Journal of heterocyclic chemistry》2019,56(10):2772-2778
Heterocyclic systems containing bis (imidazolyl) pyrrole or imidazolyl indole moieties were synthesized by heterocyclization of pyrrole or indole with arylglyoxal monohydrates and N‐aryl amidines in ethanol catalyzed by FeCl3 at room temperature. The paper reports a facile, efficient, and environmentally friendly protocol for the synthesis of new products. Products were isolated by simple filtration, and their structures were established from their spectroscopic data. 相似文献
1000.
Najmeh Nazari Mahboubeh Masrournia Zarrin Es'haghi Mohammad‐Reza Bozorgmehr 《SEPARATION SCIENCE PLUS》2019,2(12):440-448
Simultaneous extraction of basic, acidic and neutral compounds is an important goal in sample preparation. In this study, dispersive solid‐phase microextraction of three analyte types was carried out in a single step. The target compounds: aniline, phenol and naphthalene with surfactant modified magnetic graphene oxide sheets, before gas chromatography with flame ionization detection. The dispersive solid‐phase microextraction performed in both cationic and anionic modes by cetyltrimethylammonium bromide and sodium dodecyl sulfate respectively. First, the analytes were vortexed and adsorbed then the supernatant was decanted with a magnet and the sorbent was eluted with the proper solvent. The linearity was obtained over a wide concentration range; 0.044–0.50, 0.043–0.50 and 0.027–0.25 µg/mL for aniline, phenol and naphthalene respectively in both modes. The limit of detection and the limit of quantitation for target analytes were 0.008 –0.02 and 0.027–0.067 µg/mL, respectively in both modes. The method relative standard deviations for the analytes (0.1 µg/mL conc.) were ranged from 4.0 to 10.9% (n = 10). Enrichment factors ranged from 60 to 373. The method was successfully evaluated to simultaneously extract three different types of analytes (basic, acidic and neutral) from water samples. The recoveries ranged from 90.0 to 100.0%. 相似文献