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891.
In this paper we use subsets and algebraic substructures of a 3-prime nearring R admitting a derivation d to study the commutativity of the subsets, the algebraic substructures and the near-ring R under suitable conditions on d, R and the algebraic substructures. The results obtained in this paper generalize several commutativity theorems due to some authors. 相似文献
892.
Khalid Hussain Zhari Ismail Amirin Sadikun Amin Malik Abdual Majid Shah Abida Latif Furqan Khurshid Hashmi 《中国化学会会志》2012,59(9):1137-1143
Orthosiphon stamineus Benth. (Family: Lamiaceae), a famous traditional medicinal plant in tropical and sub‐tropical region, is being used for treating various ailments including inflammatory conditions. Since anti‐inflammation and antiangiogenesis involve cyclooxygenase‐II pathway, the present study is aimed to carry out antiangiogenic studies and bioassay‐guided isolation on aqueous extract of the plant. After antiangiogenic activity studies on the extract, fractions were prepared by partitioning the extract with hexane, chloroform and ethyl acetate, which were then evaluated for antiangiogenic activity. The most active, hexane fraction (HF) upon activity‐guided isolation gave three compounds, 1 (betulinic acid), 2 (oleanolic acid) and 3 (ursolic acid). The total contents of these three compounds were determined in the extract and its fractions using HPLC. The extract and HF exhibited 20% and 80% antiangiogenic activity, respectively, whereas, chloroform and ethyl acetate fractions were inactive. The three isolated compounds exhibited 100% antiangiogenic activity. Median effective concentrations (EC50s) of HF, 1, 2 and 3 were found to be 84, 32, 34 and 38 μg/mL, respectively. The results of this study indicate that hexane fraction and the isolated compounds have promising antiangiogenic activity. Additionally, the isolated compounds may be sued as analytical markers to standardize extracts and formulations prepared from O. stamineus. 相似文献
893.
A synthesis of the E-isomer of the proposed structure of the novel tripeptide, lucentamycin A, was performed in an attempt to define the correct stereochemistry of this natural product. The synthetic route developed employs a stereoselective Rh-catalyzed reductive cyclization process to generate the key pyrrolidine residue in the target and a stereospecific inversion of the Z-olefin geometry to form desired E-isomer. Subsequent amide coupling reactions afforded the desired E-isomer of putative lucentamycin A. A comparison of the NMR data of synthetic E-1a with that of the naturally occurring lucentamycin A demonstrated that they are not identical substances and the E-1a was found to display no anti-proliferative activity on the colon cancer cell line HCT-116 in contrast to natural lucentamycin A. 相似文献
894.
In this article, we present three dimensional CFD study of turbulent vortex flow in an annular passage using OpenFOAM 1.6. The vortex flow is generated by introducing the flow through a tangential entry to the passage. For the analysis presented in this article, turbulence was modeled using the Rε/k − ε model, in addition, a comparison between such model with the standard k − ε model was conducted and discussed. The main characteristics of the flow such as vortex structure and recirculation zone were investigated. It was found that flow is subjected to Rankine vortex structure with three forced vortex regimes and a free vortex region near to the outer wall. The phenomenon of vortex decay was investigated by depicting the swirl number trend along the axial direction of the flow domain. It was found that the vortex decay is subjected to an exponential decay behavior. New coefficients for the exponential decay correlation were derived based on local values of velocity components in different radial planes. 相似文献
895.
Khan KM Saify ZS Arif Lodhi M Butt N Perveen S Maharvi GM Choudhary MI Atta-Ur-Rahman 《Natural product research》2006,20(6):523-530
A variety of piperidines (2-12, 14-26) with variable substituents at N-atoms have been synthesized and evaluated as urease inhibitors. The synthesized compounds showed varying degree of urease inhibitory activity ranging from 31.97 to 254 microM. The size and electron-donating or -withdrawing effects of substituents influence the activity, which lead to the formation of urease inhibitors. 相似文献
896.
UPLC-MS/MS determination of doxazosine in human plasma 总被引:2,自引:0,他引:2
Al-Dirbashi OY Aboul-Enein HY Jacob M Al-Qahtani K Rashed MS 《Analytical and bioanalytical chemistry》2006,385(8):1439-1443
A sensitive, selective and rapid method for the analysis of doxazosine (DOX) in human plasma based on ultra-performance liquid
chromatography tandem mass spectrometry (UPLC-MS/MS) is described. DOX and tamsulosin, used as an internal standard (IS),
were extracted by liquid-liquid extraction, and the chromatography was performed on a C18 UPLC column packed with 1.7 μm particles.
The total run time was 2 min. Detection was achieved by the multiple reaction monitoring of the following transitions: m/z 452→344 and m/z 409→228 for DOX and IS, respectively. Transitions of m/z 452→247 and m/z 409→271 were also collected for confirmation purposes. The calibration curve based on peak area ratio was linear up to at
least 100 ng ml−1, with a detection limit of 0.02 ng ml−1 (a signal-to-noise ratio of 3). The method showed satisfactory reproducibility, and the short-term stability of the analyte
was assessed. The method was successfully applied to the analysis of DOX in human plasma. 相似文献
897.
Sol-gel coating containing highly polar cyanopropyl and nonpolar poly(dimethylsiloxane) components (sol-gel CN-PDMS coating) was developed for capillary microextraction (CME). The sol-gel chemistry provided an efficient means to immobilize the CN-PDMS coating by establishing chemical anchorage between the coating and the fused silica capillary inner surface. This chemical bond provided excellent thermal and solvent stability to the created sol-gel coating. For the extraction of polar and nonpolar analytes, the upper allowable conditioning temperatures were 330 degrees C and 350 degrees C, respectively. To our knowledge, this is the first time when a CN-PDMS thick coating survived such a high operation temperature. The prepared sol-gel CN-PDMS coating provided effective extraction of polar and nonpolar analytes simultaneously from aqueous samples. The cyanopropyl moiety in sol-gel CN-PDMS coatings provided effective extraction of highly polar analytes such as free fatty acids, alcohols, and phenols without requiring derivatization, pH adjustment or salting out procedures. The PDMS moiety, on the other hand, provided efficient extraction of nonpolar analytes. The extraction properties of the sol-gel CN-PDMS coatings can be fine tuned via manipulation of relative proportions of 3-cyanopropyltriethoxysilane and hydroxy-terminated PDMS in the sol solution used to create the coatings. Detection limits of nanogram/liter (ng/L) were achieved for both highly polar and nonpolar analytes directly extracted from aqueous media using sol-gel CN-PDMS coated microextraction capillaries followed by GC analysis. 相似文献
898.
Chaudhry AA Haque S Kellici S Boldrin P Rehman I Khalid FA Darr JA 《Chemical communications (Cambridge, England)》2006,(21):2286-2288
Nano-particle hydroxyapatite (HA) rods, were rapidly synthesised using a three pump continuous hydrothermal process (using a water feed at up to 400 degrees C and at 24 MPa): the product was obtained as a highly crystalline and phase pure material, without the need for an ageing step or subsequent heat treatment. 相似文献
899.
Rao RN Venkateswarlu N Khalid S Narsimha R Sridhar S 《Journal of chromatography. A》2006,1113(1-2):20-31
Three different sample preparation techniques (i) solid-phase extraction, (ii) reverse osmosis and (iii) vacuum distillation have been investigated and the recoveries were compared for determination of highly water-soluble benzene and stilbene sulfonic acids in aqueous environment by liquid chromatography with photodiode array (PDA) and electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The recoveries were quite high using vacuum distillation (>90%) compared to solid phase extraction and reverse osmosis. The negative ion ESI mass spectra containing the peaks of quasimolecular ion [M-H]- allow the molecular mass determination of unknown compounds whereas the structures were proposed using fragments obtained from MS/MS analysis of [M-H]- ions. At lower fragmentation voltages only the quasimolecular ion [M-H]- was observed and as fragmentation voltages increased, it led to the formation of fragment ions corresponding to [M-H-SO3]-, [M-H-SO2]-, and SO3-. The detection limits were 1-28 microg/L with LC-ESI-MS. The sample collected from wastewater treatment plant was found to contain 21.1, 13.3, 12.1, 41.8 and 9.9 microg/L of cis-4,4(l)-diaminostilbene-2,2(l)-disulfonic acid (cis-DASDA), trans-4,4(l)-diaminostilbene-2,2(l)-disulfonic acid (trans-DASDA), 3-amino acetanilide-4-sulfonic acid (3-AASA), 4-chloroaniline-2-sulfonic acid (4-CASA), 2-chloroaniline-5-sulfonic acid (2-CASA), respectively. 相似文献
900.
Arlette Solladié-Cavallo Khalid Azyat Loïc Jierry Dominique Cahard 《Journal of fluorine chemistry》2006,127(11):1510-1514
A new tetrasubstituted cyclohexanone 5 fluorinated at C2 and having a fluoroisopropyl group at C5 has been synthesized in five steps from 3-methyl cyclohexenone and the structure of both diastereomers fully assigned. It is shown that diastereomer Ia having the fluorine atom at C2 in the axial position (in the most populated conformer of this diastereomer) is major and is a good catalyst for epoxidation of trans-olefins by oxone while diastereomer IIe is not. Moreover, only 0.3 equiv. of 5-Ia are necessary and the ketone is totaly recovered after reaction (no Baeyer-Villiger). 相似文献