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91.
Alaa S. Abd‐El‐Aziz Leslie J. May Andrea L. Edel 《Macromolecular rapid communications》2000,21(9):598-602
Synthesis and characterization of new thermally stable polynorbornenes functionalized with pendent flexible side‐chains are reported. The flexible side‐chains with terminal hydroxy groups were synthesized via SNAr reactions of cyclopentadienyliron‐complexed chlorobenzenes with aliphatic diols. Condensation of these side‐chains with exo,endo‐5‐norbornene‐2‐carboxylic acid led to the formation of substituted monomers which were characterized using one‐ and two‐dimensional NMR techniques. Ring‐opening metathesis polymerization of these monomers yielded polynorbornenes with pendent side‐chains. 相似文献
92.
Several pyrido[2,1-b]thiazines and thiazolo[2,3-a]pyridines were synthesized by reactions of cinnamonitriles with appropriate halocarbonyl compounds. Hydrazones of 3-diazotized aminopyrazolo[3,4-b]pyridinones were synthesized by coupling of their corresponding diazonium salts with several active methylene reagents. The obtained hydrazones were cyclized in refluxing ethanol containing a catalytic amount of triethylamine to afford the corresponding pyrazolopyridotriazines. All structures were established by considering the data of elemental analyses, IR, 1H-NMR, and mass spectra. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9: 571–579, 1998 相似文献
93.
94.
Christine R. de Denus Philip Baker Jaclyn Toner Sheila McKevitt Erin K. Todd Alaa S. Abd-El-Aziz 《Macromolecular Symposia》2003,196(1):113-123
Cyclic voltammetry was employed to investigate the electrochemical behavior of numerous cyclopentadienyliron (CpFe+) and pentamethyl-cyclopentadienylruthenium (Cp*Ru+) coordinated oligomers and polymers. The electrochemical behavior of the iron systems indicated the cyclopentadienyliron complexes had isolated redox centers and that changes in the reversibility of the redox couple occurred with changes in solvent and temperature. In contrast, the monometallic ruthenium systems showed large peak separations that suggested slow kinetics on the CV timescale. The cyclic voltammograms of the larger ruthenium-containing oligomers and polymers showed multiple redox steps indicating complex electrochemical behavior. 相似文献
95.
Alaa S. Amin 《Chemical Papers》2009,63(6):625-634
A simple, selective, highly sensitive and accurate procedure for the determination of trace amounts of copper has been developed
based on solid-phase spectrophotometry. Copper reacts with 5-(2-benzothiazolylazo)-8-hydroxyquinoline (BTAHQ) to give a complex
with high molar absorptivity (3.17 × 107 L mol−1 cm−1, 3.07 × 108 L mol−1 cm−1, 1.22 × 109 L mol−1 cm−1, and 1.80 × 109 L mol−1 cm−1), fixed on a Dowex 1-X8 type anion-exchange resin for 10 mL, 100 mL, 500 mL, and 1000 mL, respectively. The absorbance at
667 nm and 800 nm packed in a 1.0 mm cell was measured directly. Calibration is linear over the range 0.2–3.7 μg L−1 with RSD of < 1.28 % (n = 10). The detection and quantification limits of the 500 mL sample method are 79 ng L−1 and 260 ng L−1 when using 60 mg of Dowex 1-X8. For a 1000 mL sample, the detection and quantification limits are 67 ng L−1 and 220 ng L−1 using 60 mg of the exchanger. Increasing the sample volume can enhance the sensitivity. The proposed method was applied to
the determination of copper in different environmental water samples (tap, pit, spring, and river), food products (rice, corn
flour, and tea), and mushrooms, using the standard addition technique. 相似文献
96.
Lamsabhi AM Mó O Gutiérrez-Oliva S Pérez P Toro-Labbé A Yáñez M 《Journal of computational chemistry》2009,30(3):389-398
The intermolecular double proton transfer in dimers of uracil and 2-thiouracil is studied through density functional theory calculations. The reaction force framework provides the basis for characterizing the mechanism that in all cases has been associated to a dynamic balance between polarization and charge transfer effects. It has been found that the barriers for proton transfer depend upon the nature of the acceptor atoms and its position within the seminal monomer. Actually, the change in the nature of the hydrogen bonds connecting the two monomers along the reaction coordinate may favor or disfavor the double-proton transfer. 相似文献
97.
Ahmed Ait Mokhtar 《Comptes Rendus Mathematique》2009,347(21-22):1227-1230
98.
The clonal analysis of a diverse collection of Salmonella Enteritidis indicates that most strains belong to a single multilocus genotype (i.e., ET-3) regardless of phage type, geographic origin, or time of isolation that spanned over 2 decades (1978 to 2004). Attachment and invasion assays, however, indicate that, among ET-3 isolates, there is a distinct invasive bacterial subpopulation that is more readily recovered from eggs and clinical cases in humans than from chicken cecal samples. These observations support the hypothesis that the specialized ability of S. Enteritidis to infect the avian reproductive tract and contaminate eggs has been critical in its emergence as a frequent cause of human illness. 相似文献
99.
In a multistep reaction, 3,3′-(2-aryl-2H-isoindol-1,3-ylene)-di-(1,4-naphthoquinone-2-carbonitriles) 13a-f have been formed in 25-61% yield from a series of N-arylisoindolines 8a-f with (1,3-dioxo-2,3-dihydro-1H-inden-2-ylidene)propanedinitrile (1) in aerated pyridine. The structure of one of these products (13f) has been unambiguously confirmed by a single crystal X-ray structure analysis. Under otherwise the same conditions, 2-(3-methoxyphenyl)-isoindoline (8g) and 1 gave 38% of [4-(2,3-dihydro-1H-isoindol-2-yl)-2-methoxyphenyl]-1,3-dioxoindan-2-ylidene)acetonitrile (15). Rationales for these conversions involving the known rearrangement of the radical anion of 1 into the radical anion of 1,4-naphthoquinone-2,3-dicarbonitrile (3) are presented. 相似文献
100.
For the first time, polyaniline-coated cerium oxide nanoparticles were synthesized in alkaline media and applied for preconcentration of ultra-trace levels of cadmium (??) in different real samples followed by electrothermal atomic absorption spectrometry. Cerium oxide nanoparticles were synthesized by a microwave method and modified by polyaniline to produce polyaniline-coated cerium oxide nanoparticles. Fourier-transform infrared spectroscopy and scanning electron microscopy were used to characterize the synthesized adsorbent. To optimize the critical experimental conditions; surface response methodology—Box–Behnken experimental design was used. On the basis of the results, pH 8.4, 10?mg of polyaniline-coated cerium oxide nanoparticles, 14.4?min extraction time, and 4.3?min desorption time were selected as the optimum conditions. Under the optimum conditions the calibration curve of cadmium (??) was linear in the range of 0.02–0.4?ng?mL?1 with a correlation coefficient of 0.9976. The relative standard deviation based on seven replicate analysis of 0.1?ng?mL?1 cadmium (??) was 4.2% and limit of detection was 0.005?ng?mL?1 cadmium (??). The analysis of certified reference material shows very good agreement with the certified value. Finally, the proposed method was applied for the determination of ultra-trace levels of cadmium (??) in different water, rice, and tea samples. 相似文献