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991.
B. S. Randhawa Kamal Jeet Sweety 《Journal of Radioanalytical and Nuclear Chemistry》1999,241(3):675-677
Mössbauer spectra of alkali tris(maleato) ferrates(III), i.e., M3[Fe(C2H2C2O4)3]·nH2O [M=Li, Na, K, Cs] at 300 K display a doublet. The Mössbauer parameters indicate these complexes to be high spin with octahedral symmetry. The isomer shift shows a decreasing trend with the increase in electronegativity/polarizing power of the substituent cation (Li+, Na+, K+, Cs+). A linear correlation between isomer shift values and the (Fe?O) stretching frequencies has also been observed. 相似文献
992.
Gamil A. Guirgis Yasser E. Nashed Peter Klaeboe Valdemaras Aleksa James R. Durig 《Structural chemistry》1999,10(1):1-15
The Raman spectra (3500 to 30 cm–1) of allyltrifluorosilane, CH2CHCH2SiF3, in the liquid with quantitative depolarization ratios and solid states, and the infrared spectra (3500 to 30 cm–1) of the gas and solid have been recorded. Additionally, the mid-infrared spectra of the sample dissolved in liquified xenon as a function of temperature (–100° to –55°C) have been recorded. All of these data indicate there are two conformers, the more stable gauche rotamer and a very small amount of the cis conformer in the fluid states, but only the gauche form remains in the polycrystalline solid. The variable temperature studies of the infrared spectrum of the xenon solution indicate a relatively large enthalpy difference of 354±30 cm–1 (4.23±0.36 kJ/mol) between the conformers. The fundamental frequencies for the asymmetric (54 cm–1) and SiF3 (48 cm–1) torsions for the gauche conformer were observed in the far infrared spectrum, and from the SiF3 torsional frequency the barrier to internal rotation is calculated to have a value of 525 cm–1 (6.28 kJ/mol). A complete vibrational assignment is presented for the gauche conformer that is consistent with the predicted wavenumbers utilizing the force constants from ab initio MP2/6-31G* calculations. The optimized geometries, conformational stabilities, harmonic force fields, infrared intensities, Raman activities, depolarization ratios, and vibrational wavenumbers have been obtained from RHF/6-31G* and/or MP2/6-31G* ab initio calculations. These quantities are compared to the corresponding experimental quantities when appropriate as well as with corresponding results for some similar molecules.Taken in part from the dissertation of Y. E. Nashed, which will be submitted to the Department of Chemistry in partial fulfillment of the Ph.D. degree 相似文献
993.
The reaction of 3‐amino‐4,6‐dimethylthieno[2,3‐b]pyridine‐2‐carboxamide (1a) or its N‐aryl derivatives 1b‐d with carbon disulphide gave the pyridothienopyrimidines 2a‐d , whilst when the same reaction was carried out using N1‐arylidene‐3‐amino‐4,6‐dimethylthieno[2,3‐b]pyridine‐2‐carbohydrazides (1e‐h) , pyridothienothiazine 3 was obtained. Also, refluxing of 1b‐d with acetic anhydride afforded oxazinone derivative 4 . Compounds 2a and 2b‐d were also obtained by the treatment of thiazine 3 with ammonium acetate or aromatic amines, respectively. When compound 2a was allowed to react with arylidene malononitriles or ethyl α‐cyanocinnamate, novel pyrido[3″,2″:4′,5′]thieno[3′,2′:4,5]pyrimido[2,1‐b][1,3] thiazines 5a‐c were obtained. Treatment of 2b‐d with bromine in acetic acid furnished the disulphide derivatives 6a‐c . U.V. irradiation of 2b‐d resulted in the formation of pyrido[3″,2″:4′,5′]thieno[3′,2′:4,5]pyrimido[2,1‐b]benzthiazoles 7a‐c . The reaction of 2a‐d with some halocarbonyl compounds afforded the corresponding S‐substituted thiopyrido thienopyrimidines 8a‐j . Compound 8b was readily cyclized into the corresponding thiazolo[3″,2″‐a]‐pyrido[3′,2′:4,5]thieno[3,2‐d]pyrimidine 9 upon treatment with conc. sulphuric acid. Heating of 2a,b with hydrazine hydrate in pyridine afforded the hydrazino derivatives 11a,b . Reaction of ester 8c with hydrazine hydrate in ethanol gave acethydrazide 10 . Compounds 10 and 11a,b were used as versatile synthons for other new pyridothienopyrimidines 12–15 as well as [1,2,4] triazolopyridothienopyrimidines 16–19. 相似文献
994.
Kamal M. El‐Shaieb 《Heteroatom Chemistry》2006,17(5):365-368
Utilizing domestic microwave oven reactions of diaminomaleonitrile with various selected reagents, novel heterocycles such as dicyanopyrazine, 4,5‐dicyanoimidazole as well as dicyanobenzodiazocine derivatives were prepared. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:365–368, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20212 相似文献
995.
Haya Hussain Shujaat Ahmad Syed Wadood Ali Shah Mehreen Ghias Abid Ullah Shafiq Ur Rahman Zul Kamal Farman Ali Khan Nasir Mehmood Khan Juma Muhammad Mazen Almehmadi Osama Abdulaziz Saad Alghamdi 《Molecules (Basel, Switzerland)》2021,26(23)
Cognitive decline in dementia is associated with deficiency of the cholinergic system. In this study, five mono-carbonyl curcumin analogs were synthesized, and on the basis of their promising in vitro anticholinesterase activities, they were further investigated for in vivo neuroprotective and memory enhancing effects in scopolamine-induced amnesia using elevated plus maze (EPM) and novel object recognition (NOR) behavioral mice models. The effects of the synthesized compounds on the cholinergic system involvement in the brain hippocampus and their binding mode in the active site of cholinesterases were also determined. Compound h2 (p < 0.001) and h3 (p < 0.001) significantly inhibited the cholinesterases and reversed the effects of scopolamine by significantly reducing TLT (p < 0.001) in EPM, while (p < 0.001) increased the time exploring the novel object. The % discrimination index (DI) was significantly increased (p < 0.001) in the novel object recognition test. The mechanism of cholinesterase inhibition was further validated through molecular docking study using MOE software. The results obtained from the in vitro, in vivo and ex vivo studies showed that the synthesized curcumin analogs exhibited significantly higher memory-enhancing potential, and h3 could be an effective neuroprotective agent. However, more study is suggested to explore its exact mechanism of action. 相似文献
996.
Mohammad M. Kamal Zhizhou Liu Siyuan Zhai Dragoslav Vidovi 《Molecules (Basel, Switzerland)》2021,26(18)
Although there exists a variety of different catalysts for hydroboration of organic substrates such as aldehydes, ketones, imines, nitriles etc., recent evidence suggests that tetra-coordinate borohydride species, formed by activation, redistribution, or decomposition of boron reagents, are the true hydride donors. We then proposed that Me2S-BH3 could also act as a hydride donor for the reduction of various imines, as similar compounds have been observed to reduce carbonyl substrates. This boron reagent was shown to be an effective and chemoselective hydroboration reagent for a wide variety of imines. 相似文献
997.
Musa R. Kamal 《Macromolecular Symposia》1996,101(1):167-176
The use of computers in plastics processing has continued to grow in parallel with rapid expansion of computer availability and computing power. One of the main areas of application is in computer simulation of the injection molding process where more demanding applications relate to the simulation of molding of complex-shaped moldings. Recent development include the use of boundary fitted curvilinear coordinates, the incorporation of fountain flow, and the coupling of crystallization kinetics within the transport equations. Applications in computer control relate to the control of pressure and temperature throughout the injection molding process, self-tuning control, physically-based dynamic models, and the control of properties of the molding, e.g. the weight of the article. Recent developments relate to the application of inverse modeling. An example is given of the use of inverse modeling of thermal stresses to predict or optimize thermal or pressure history during molding. 相似文献
998.
999.
1000.
A. A. M. Kamal 《Acta Mathematica Hungarica》2001,90(3):209-217
We give some conditions under which an R-endomorphism f fixing an essential ideal I of a right near-ring R must be the identity R-automorphism on RR. As a consequence of the results obtained we generalize the theorem of [1].
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献