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991.
The electronic structure and redox properties of the highly oxidizing, isolable RuV?O complex [RuV(N4O)(O)]2+, its oxidation reactions with saturated alkanes (cyclohexane and methane) and inorganic substrates (hydrochloric acid and water), and its intermolecular coupling reaction have been examined by DFT calculations. The oxidation reactions with cyclohexane and methane proceed through hydrogen atom transfer in a transition state with a calculated free energy barrier of 10.8 and 23.8 kcal mol?1, respectively. The overall free energy activation barrier (ΔG≠=25.5 kcal mol?1) of oxidation of hydrochloric acid can be decomposed into two parts: the formation of [RuIII(N4O)(HOCl)]2+ (ΔG=15.0 kcal mol?1) and the substitution of HOCl by a water molecule (ΔG≠=10.5 kcal mol?1). For water oxidation, nucleophilic attack on RuV?O by water, leading to O? O bond formation, has a free energy barrier of 24.0 kcal mol?1, the major component of which comes from the cleavage of the H? OH bond of water. Intermolecular self‐coupling of two molecules of [RuV(N4O)(O)]2+ leads to the [(N4O)RuIV? O2? RuIII(N4O)]4+ complex with a calculated free energy barrier of 12.0 kcal mol?1. 相似文献
992.
Sébastien Gagné 《Biomedical chromatography : BMC》2013,27(5):664-668
A novel method for the biological monitoring of benzene‐exposed workers has been developed through ultra‐performance liquid chromatography coupled to tandem mass spectrometry. The method uses trans,trans‐muconic acid in urine as the benzene‐exposure biomarker. The method was developed using a triple quadrupole mass spectrometer with enough sensitivity to facilitate diluting and injecting the urine samples directly, rather than performing a solid‐phase extraction procedure as is common in the available protocols. Moreover, compared with a conventional high‐pressure liquid chromatography system, the separation power provided by the ultra‐performance liquid chromatography system allows a 10‐fold reduction in run time. The method was adjusted to a dynamic range of between 198.9 and 4916.7 µg/L to cover the biological exposure index of trans,trans‐muconic acid in urine. Also, the method demonstrated intra‐day and inter‐day precision at 98%, and accuracy within an acceptable range of 101 ± 8%. The method has been used to quantify various types of urine samples, such as workers' urine and inter‐laboratory proficiency tests. Depending on the sample, the quantified levels ranged from less than the limit of quantitation to 3836.7 µg/L. No levels exceeding the calibration range were detected in the urine of workers, and the reported concentrations in urine for the proficiency tests were, as expected, based on known values. Moreover, the new method using sample dilution and faster chromatographic run was more effective, facilitating fast communication of results, as needed, to decision‐makers. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
993.
Tzu‐Chuan Huang Shih‐Ming Chen Yi‐Chieh Li Jen‐Ai Lee 《Biomedical chromatography : BMC》2013,27(9):1100-1106
Urinary d ‐lactate is highly correlated to diabetic nephropathy – a progressive kidney disease in renal glomeruli. In this study, we used a C3H/3e mouse model to investigate the relationship between urinary d ‐lactate and aristolochic acid nephropathy where the glomerular structure is not affected. The nephropathy was induced using intravenous injections of aristolochic acid at a dosage of 10 mg/kg per day for 5 days and was characterized biochemically and histologically. The urinary excretions of proteins, N‐acetyl‐β‐d ‐glucosaminidase and serum creatinine were determined and connected to histological conventional findings. Urinary d ‐lactate was analyzed using column‐switching high‐performance liquid chromatography with fluorescence detection. The results showed a remarkable increase of urinary markers, including of urinary proteins and N‐acetyl‐β‐d ‐glucosaminidase, and the histological examination confirmed a diagnosis of acute tubule necrosis. The ratio of d ‐lactate to creatinine in the urine of aristolochic acid‐treated mice was approximately 36 times greater than that of the mice in the control group (p < 0.05). The ratios for the two groups of mice were 311.00 ± 71.70 and 8.60 ± 1.80 µmol/mmol creatinine, respectively. These data confirm in vivo that urinary d ‐lactate reflects renal injury conditions in aristolochic acid‐treated mice and may be a marker for the assessment of nephropathy. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
994.
采用浸渍法将糠醇负载在铝改性的SBA-15介孔孔道中,经550℃不完全碳化制备了结构规整、含多苯环的中空管状硅碳复合介孔材料.结果表明,通过温和磺酸化作用可使磺酸基团成功取代在多苯环上,其酸量随着多苯环涂层厚度变化在0.38~0.84 mmol/g范围内可控调变.相比于蔗糖作为糖源的复合固体酸,所制碳多苯环-硅酸催化剂具有中空碳纳米管堆积的类似CMK-5介孔结构,以及较大的反应空间、稳定的机械性能、较高的比表面和大量可以接触的质子酸中心,因而在大分子缩醛(酮)反应中表现了良好的催化性能. 相似文献
995.
Three isomeric metal-organic frameworks,[Cd2(X)(btc)(DMA)3]n(X = Cl(1),Br(2),I(3),H3btc =1,3,5-benzenetricarboxylic acid and DMA = N,Nˊ-dimethylacetamide),have been synthesized and characterized by elemental analysis,infrared spectra(IR),thermogravimetric(TG) analyses and single-crystal X-ray diffraction.Single-crystal X-ray analysis reveals that compounds 1–3 crystallize in the orthorhombic P212121 space group,and feature a three-dimensional(3D) extended framework containing dinuclear [Cd2(COO)3] units as the secondary building units(SBUs).Topological analysis reveals that compounds 1–3 can be simplified into a 3-connected srs topological network. 相似文献
996.
997.
An efficient synthesis of novel coumarin derivatives via a three‐component condensation of 4‐hydroxycoumarin, aldehydes and aromatic amines catalyzed by sulfonic acid functionalized ionic liquid L‐2‐(hydroxymethyl)‐1‐(4‐sulfobutyl)pyrrolidinium hydrogen sulfate ([HYSBPI]·HSO4) is reported. The condensed product was obtained with excellent yields in water under microwave irradiation condition. The antitumor activities of all the synthesized compounds were assessed on two different human cancer cell lines (A‐549 and MCF‐7), and the results showed that these compounds had weak‐to‐good antitumor activities and their IC50 ranged from 0.05 to more than 100 µmol·L?1. 相似文献
998.
999.
1000.
Selective Exo‐Enzymatic Labeling of N‐Glycans on the Surface of Living Cells by Recombinant ST6Gal I