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991.
Confined‐Space Alloying of Nanoparticles for the Synthesis of Efficient PtNi Fuel‐Cell Catalysts 下载免费PDF全文
Claudio Baldizzone Stefano Mezzavilla Dr. Hudson W. P. Carvalho Dr. Josef Christian Meier Dr. Anna K. Schuppert Dr. Marc Heggen Dr. Carolina Galeano Prof. Dr. Jan‐Dierk Grunwaldt Prof. Dr. Ferdi Schüth Dr. Karl J. J. Mayrhofer 《Angewandte Chemie (International ed. in English)》2014,53(51):14250-14254
The efficiency of polymer electrolyte membrane fuel cells is strongly depending on the electrocatalyst performance, that is, its activity and stability. We have designed a catalyst material that combines both, the high activity for the decisive cathodic oxygen reduction reaction associated with nanoscale Pt alloys, and the excellent durability of an advanced nanostructured support. Owing to the high specific activity and large active surface area, the catalyst shows extraordinary mass activity values of 1.0 A mgPt?1. Moreover, the material retains its initial active surface area and intrinsic activity during an extended accelerated aging test within the typical operation range. This excellent performance is achieved by confined‐space alloying of the nanoparticles in a controlled manner in the pores of the support. 相似文献
992.
Freitas PP Cardoso FA Martins VC Martins SA Loureiro J Amaral J Chaves RC Cardoso S Fonseca LP Sebastião AM Pannetier-Lecoeur M Fermon C 《Lab on a chip》2012,12(3):546-557
Since the fundamental discovery of the giant magnetoresistance many spintronic devices have been developed and implemented in our daily life (e.g. information storage and automotive industry). Lately, advances in the sensors technology (higher sensitivity, smaller size) have potentiated other applications, namely in the biological area, leading to the emergence of novel biomedical platforms. In particular the investigation of spintronics and its application to the development of magnetoresistive (MR) biomolecular and biomedical platforms are giving rise to a new class of biomedical diagnostic devices, suitable for bench top bioassays as well as point-of-care and point-of-use devices. Herein, integrated spintronic biochip platforms for diagnostic and cytometric applications, hybrid systems incorporating magnetoresistive sensors applied to neuroelectronic studies and biomedical imaging, namely magneto-encephalography and magneto-cardiography, are reviewed. Also lab-on-a-chip MR-based platforms to perform biological studies at the single molecule level are discussed. Overall the potential and main characteristics of such MR-based biomedical devices, comparing to the existing technologies while giving particular examples of targeted applications, are addressed. 相似文献
993.
The thermodynamic functions free energy, enthalpy, and entropy of solution, were evaluated from solubility data of benzocaine determined at several temperatures in octanol, water, and the mutually saturated solvents, in isopropyl myristate, water, and the mutually saturated solvents, and in cyclohexane. In aqueous media the solubility was determined at pH 7.4 and ionic strength 0.15 mol-L–1. The excess free energy and the activity coefficients of the solutes also were determined. The solubility was higher in organic media, such as octanol and isopropyl myristate, than in aqueous media and cyclohexane. 相似文献
994.
Cardoso CL Lima VV Zottis A Oliva G Andricopulo AD Wainer IW Moaddel R Cass QB 《Journal of chromatography. A》2006,1120(1-2):151-157
Immobilized enzyme reactors (IMERs) for on-line enzymatic studies are useful tool to select specific inhibitors and may be used for direct determination of drug-receptor binding interactions and for the rapid on-line screening to identify specific inhibitors. This technique has been shown to increase the stability of enzymes. The enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) plays an important role in the life cycle of the Trypanosoma cruzi and it has become a key target in the drug discovery program for Chagas' disease. Crystallographic studies have indicated that there are significant inter-species differences in GAPDH activity and sensitivity. For example the active sites of GAPDH in T. cruzi and humans differ by a substitution of ASP(210) (T. cruzi) by Leu(194) in human. Based on this information we initiated the study to develop optimal conditions for the covalent immobilization of the human GAPDH enzyme on a modified capillary support (400 mm x 0.10 mm). The chromatographic separation of NAD from NADH was achieved using a RP-Spherex-diol-OH (10 cm x 0.46 cm, 10 microm, 100 A) column. By using multidimensional HPLC chromatography system it was possible to investigate the activity and kinetic parameters of the GAPDH-IMER. The values obtained for D-GA3P and NAD were K(m)=3.5+/-0.2 mM and 0.75+/-0.04 mM, respectively, and were compared with values obtained with the free enzyme. The activity of the immobilized GAPDH has been preserved for over 120 days. 相似文献
995.
H. G. Von Schnering K. Peters W. Hnle R. H. Cardoso Gil N. Caroca-Canales 《无机化学与普通化学杂志》1996,622(1):112-122
The Cubic Phases Na16(ARb6)Sb7, Compounds with the Anions A = Rb?, Na?, Au?, I? The novel compounds Na16(ARb6)Sb7 have been synthesized from the elements in sealed Nb ampoules at 873 K (A = Rb) and 823 K (A = I, Na, Au). They form brittle cuboctahedra (silver metallic; A = Rb) and irregular polyhedra (silver metallic lustre; A = Na, I; golden metallic lustre; A = Au). They rapidly decompose in moist air to gray products. Their crystal structures have been determined by single crystal X-ray crystallography (A = Rb: a = 1565.8(2) pm; A = I: a = 1563.3(2) pm; A = Na: a = 1562.6(2) pm; A = Au: a = 1560.7(2) pm). They crystallize cubically in the space group Fm3 m (no. 225) with Z = 4 formula units and are isotypic with Sc11Ir4. The compounds are ZINTL phases and their structures can be described as an eightfold defect variant of the Li3Bi type of structure (cF128-8; a = 2a′(Li3Bi)). The Sb atoms form a network of cuboctahedra, centered alternatingly by a SbNa8 cube or a ARb6 octahedron. Main structural features are the anions A? within the Rb6 octahedron. Supporting the existence of A? are the isotypical compounds with the more common anion forming elements (A = Au, I), as well as electrostatic potential considerations together with calculations of the volume increments. The semiconducting properties (Eg = 0.33 eV) of Na16(RbRb6)Sb7, as well as the diamagnetism χmol = ?508 × 10?6 cm3 mol?1, are in accordance with those to be expected from the Zintl concept. 相似文献
996.
Ab initio calculations were performed on complexes between cations and s-triazine, which has a small and positive quadrupole moment. Minimum energy pi-complexes were found between s-triazine and cations. Minimum pi-complexes with anions were previously reported. This ability of s-triazine to form stable complexes with either anions or cations is studied using several theoretical methods. A likely explanation of this duality is the stabilization obtained from the ion-induced polarization. [structure: see text] 相似文献
997.
998.
Habiba Rechek Ammar Haouat Kaouther Hamaidia Hamza Allal Tarek Boudiar Diana C. G. A. Pinto Susana M. Cardoso Chawki Bensouici Noureddine Soltani Artur M. S. Silva 《Molecules (Basel, Switzerland)》2021,26(17)
Warionia saharae Benth. & Coss. (Asteraceae) is an endemic species of North Africa naturally grown in the southwest of the Algerian Sahara. In the present study, this species’ hydromethanolic leaf extract was investigated for its phenolic profile characterized by ultra-high-performance liquid chromatography coupled with a diode array detector and an electrospray mass spectrometer (UHPLC-DAD-ESI/MS). Additionally, the chemical composition of W. saharae was analyzed by gas chromatography–mass spectrometry, and its antioxidant potential was assessed through five in vitro tests: DPPH● scavenging activity, ABTS●+ scavenging assay, galvinoxyl scavenging activity, ferric reducing power (FRP), and cupric reducing antioxidant capacity. The UHPLC-DAD-ESI/MS analysis allowed the detection and quantification of 22 compounds, with taxifolin as the dominant compound. The GC–MS analysis allowed the identification of 37 compounds, and the antioxidant activity data indicate that W. saharae extract has a very high capacity to capture radicals due to its richness in compounds with antioxidant capacity. The extract also showed potent α-glucosidase inhibition as well as a good anti-inflammatory activity. However, weak anti-α-amylase and anticholinesterase activities were recorded. Moreover, an in silico docking study was performed to highlight possible interactions between three significant compounds identified in W. saharae extract and α-glucosidase enzyme. 相似文献
999.
Carolina Maria Fioramonti Calixto 《Analytical letters》2017,50(14):2323-2334
A bare graphite–polyurethane composite electrode (60% graphite, m/m) was used for the determination of tetracycline in bovine and breast milk. Limits of detection as low as 2.6?µmol?L?1 were obtained in pH 2.3 phosphate buffer using optimized differential pulse voltammetric parameters at the graphite–polyurethane composite electrode. The milk treatment consisted of acidification with 80% trichloroacetic acid, centrifugation to remove solid phase from milk, the isolation of the antibiotic from the whey using solid-phase extraction, and direct analysis in pH 2.3 phosphate buffer. Recoveries between 83 and 99% and 97% were obtained for tetracycline fortified in bovine and breast milk, suggesting that this approach is a promising screening procedure. 相似文献
1000.
Type I and Type II Photosensitized Oxidation Reactions: Guidelines and Mechanistic Pathways 下载免费PDF全文
Maurício S. Baptista Jean Cadet Paolo Di Mascio Ashwini A. Ghogare Alexander Greer Michael R. Hamblin Carolina Lorente Silvia Cristina Nunez Martha Simões Ribeiro Andrés H. Thomas Mariana Vignoni Tania Mateus Yoshimura 《Photochemistry and photobiology》2017,93(4):912-919
Here, 10 guidelines are presented for a standardized definition of type I and type II photosensitized oxidation reactions. Because of varied notions of reactions mediated by photosensitizers, a checklist of recommendations is provided for their definitions. Type I and type II photoreactions are oxygen‐dependent and involve unstable species such as the initial formation of radical cation or neutral radicals from the substrates and/or singlet oxygen (1O2 1?g) by energy transfer to molecular oxygen. In addition, superoxide anion radical () can be generated by a charge‐transfer reaction involving O2 or more likely indirectly as the result of O2‐mediated oxidation of the radical anion of type I photosensitizers. In subsequent reactions, may add and/or reduce a few highly oxidizing radicals that arise from the deprotonation of the radical cations of key biological targets. can also undergo dismutation into H2O2, the precursor of the highly reactive hydroxyl radical () that may induce delayed oxidation reactions in cells. In the second part, several examples of type I and type II photosensitized oxidation reactions are provided to illustrate the complexity and the diversity of the degradation pathways of mostly relevant biomolecules upon one‐electron oxidation and singlet oxygen reactions. 相似文献