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991.
Barbara Le?niewska Monika Kosi��ska Beata Godlewska-?y?kiewicz El?bieta Zambrzycka Agnieszka Z. Wilczewska 《Mikrochimica acta》2011,175(3-4):273-282
An ion-imprinted polymer (IIP) was obtained by copolymerization of methacrylic acid (as a functional monomer) and ethylene glycol dimethacrylate (as a crosslinking agent) in the presence of various chelators for Pt(II) ion and using 2,2??-azo-bis-isobutyronitrile as the initiator. Specifically, acetaldehyde thiosemicarbazone (AcTSn) and benzaldehyde thiosemicarbazone (BnTSn) were used as chelators. The IIPs were applied as sorbents for solid-phase extraction of Pt(II) and Pt(IV) ions from aqueous solutions. The effects of acidity and flow rate of the sample, of elution conditions and of potentially interfering ions were investigated. The imprinting effect of analyte is clearly demonstrated by the fact that only the IIP is capable of quantitative retention of Pt(II) and Pt(IV) ions. The method works best in the pH range from 0.5 to 1 and from 3.5 to 9.5. The ions can be recovered with an acidic solution of thiourea. The Pt-AcTSn polymer displays better sorption properties for the separation of analytes. The selectivity coefficients of the Pt-AcTSn and control polymers for Pt(IV) in the presence Pd(II), Rh(III), Ru(III), Al(III) and Cu(II) were calculated, and the sorbent capacity for Pt(IV) was found to be 4.56???g?g?-1. The method was successfully applied to the determination of Pt(IV) by electrothermal atomic absorption spectrometry in tap water, tunnel dust and anode slime samples. Figure
The new ion imprinted polymers based on Pt(II)-thiosemicarbazone derivative chelates were prepared and used as solid phase extraction sorbent for selective separation of platinum. The method was successfully applied to the determination of analyte in environmental samples by electrothermal atomic absorption spectrometry 相似文献
992.
A new multiresidue method for the efficient screening, identification and quantification of over 160 pesticides belonging to different chemical classes in red, rose and white wines have been developed. The analysis was based on gas chromatographic-tandem quadrupole mass spectrometric determination (GC-QqQ-MS/MS). An optimization strategy involved the selection of buffering conditions and sorbents for dispersive-solid phase extraction (dispersive-SPE) in order to achieve acceptably high recoveries and reduce co-extractives in the final extracts. As a result, the optimized procedure allowed us to obtain consistent recoveries of the target pesticides including problematic ones such as captan, chlorothalonil, dichlofluanid, folpet and tolylfluanid. The attained recoveries were typically between 80 and 110% (89% on average) with RSD values typically lower than 10% (8% on average) at three spiking levels of 0.01, 0.05 and 0.2 mg kg−1. Linearity was studied in the range between 0.005 and 0.2 mg kg−1 using pesticide standards prepared both in pure solvent and in the presence of matrix, showing coefficients of determination (R2) higher than 0.99 for all the pesticides except for desmedipham, thiabendazole and thiamethoxam in pure solvent. The study of the ratio of the slopes obtained in solvent and in matrix provided information about the matrix effects, which was <10%, 10-20% and >20% for 33, 36 and 31% of the studied pesticides, respectively. To improve accuracy, matrix matched standards were always used for calculation of the quantification results. The expanded uncertainties were estimated by using a “top-down” approach as being 17% on average (coverage factor k = 2, confidence level 95%). Finally, the method was used with success to detect and quantify pesticide residues in commercial wines. 相似文献
993.
A series of salts, with the 9-aminoacridinium cation (9-AA) and aromatic carboxylic acid: benzoate (1), ortho-phthalate (2), and salicylate (3) anions have been synthesized and characterized using X-ray diffraction. In the crystal packing, the ions are linked via N-H?O, O-H?O, and C-H?O hydrogen bonds. Analysis of the hydrogen bonds in the crystal lattices of the title compounds shows that the cations and anions form tetramers. The ions in these tetramers are linked via N(amino)-H?O(carboxy) hydrogen bonds forming R22(8) (1 and 3) or R24(15) (2) hydrogen bond ring motifs. The cations interact through π-π interactions in the ABBA (1), AB (2) or ABA (3) arrangement to form columns (1 and 2) or chains (3). 相似文献
994.
W. SzczepanikP. M?ynarz P. StefanowiczM. Kucharczyk-Klamińska N. D’AmelioA. Olbert-Majkut A. StaszewskaM. Ratajska Z. SzewczukM. Je?owska-Bojczuk 《Polyhedron》2011,30(1):9-15
The coordination properties of the novel conjugate towards copper ions were investigated. The performed studies exhibited the unusual binding properties of the ligand molecule having two potential strong coordination sites, namely dipeptidic chain and pyridyl nitrogens. On the basis of potentiometric and spectroscopic studies the binding at the low pH values to the aromatic entity is suggested, while the rise of pH (including physiological one) yielded the dimeric head-to-tail complex formation. This stable species possesses three nitrogen donors involved in Cu(II) chelation: N(pirydyl), NH2 and N−(amide). 相似文献
995.
996.
997.
Mesoporous carbons containing silver nanoparticles have been successfully synthesized under acidic conditions by employing
resorcinol and formaldehyde as carbon precursors and triblock copolymer EO101PO56EO101 (Lutrol F127) as a soft template. Silver nanoparticles of ∼90 nm were added to the synthesis mixture to achieve 10 wt% and
20 wt% of Ag loading in the carbon. Also, tetraethyl orthosilicate (TEOS) was introduced to the system in order to improve
adsorption properties of the silver-carbon composites and to reinforce its structure. The resulting carbons with incorporated
silver nanoparticles featured high surface areas, large total pore volumes and primary mesopores in the range between ∼6–7 nm. 相似文献
998.
999.
Stephen E Huang D Shaw JL Blake AJ Collison D Davies ES Edge R Howard JA McInnes EJ Wilson C Wolowska J McMaster J Schröder M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(37):10246-10258
The NiII complexes [Ni([9]aneNS2‐CH3)2]2+ ([9]aneNS2‐CH3=N‐methyl‐1‐aza‐4,7‐dithiacyclononane), [Ni(bis[9]aneNS2‐C2H4)]2+ (bis[9]aneNS2‐C2H4=1,2‐bis‐(1‐aza‐4,7‐dithiacyclononylethane) and [Ni([9]aneS3)2]2+ ([9]aneS3=1,4,7‐trithiacyclononane) have been prepared and can be electrochemically and chemically oxidized to give the formal NiIII products, which have been characterized by X‐ray crystallography, UV/Vis and multi‐frequency EPR spectroscopy. The single‐crystal X‐ray structure of [NiIII([9]aneNS2‐CH3)2](ClO4)6?(H5O2)3 reveals an octahedral co‐ordination at the Ni centre, while the crystal structure of [NiIII(bis[9]aneNS2‐C2H4)](ClO4)6?(H3O)3? 3H2O exhibits a more distorted co‐ordination. In the homoleptic analogue, [NiIII([9]aneS3)2](ClO4)3, structurally characterized at 30 K, the Ni? S distances [2.249(6), 2.251(5) and 2.437(2) Å] are consistent with a Jahn–Teller distorted octahedral stereochemistry. [Ni([9]aneNS2‐CH3)2](PF6)2 shows a one‐electron oxidation process in MeCN (0.2 M NBu4PF6, 293 K) at E1/2=+1.10 V versus Fc+/Fc assigned to a formal NiIII/NiII couple. [Ni(bis[9]aneNS2‐C2H4)](PF6)2 exhibits a one‐electron oxidation process at E1/2=+0.98 V and a reduction process at E1/2=?1.25 V assigned to NiII/NiIII and NiII/NiI couples, respectively. The multi‐frequency X‐, L‐, S‐, K‐band EPR spectra of the 3+ cations and their 86.2 % 61Ni‐enriched analogues were simulated. Treatment of the spin Hamiltonian parameters by perturbation theory reveals that the SOMO has 50.6 %, 42.8 % and 37.2 % Ni character in [Ni([9]aneNS2‐CH3)2]3+, [Ni(bis[9]aneNS2‐C2H4)]3+ and [Ni([9]aneS3)2]3+, respectively, consistent with DFT calculations, and reflecting delocalisation of charge onto the S‐thioether centres. EPR spectra for [61Ni([9]aneS3)2]3+ are consistent with a dynamic Jahn–Teller distortion in this compound. 相似文献
1000.
Asymmetric aldol-Tishchenko reaction catalyzed by Yb-complexes with basic amino acid-derived ligands
Simple amino acid-derived esters have been identified as promising chiral sources for the ytterbium-catalyzed aldol-Tishchenko reaction of aromatic aldehydes with aliphatic ketones. The 1,3-anti-diols with three stereogenic centers were isolated in excellent yields, complete anti-diastereocontrol and enantioselectivities of up to 50% ee. 相似文献