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191.
Samia Mahouche Nejib Mekni Leila Abbassi Philippe Lang Christian Perruchot Mohamed Jouini Fayna Mammeri Mireille Turmine Hatem Ben Romdhane Mohamed M. Chehimi 《Surface science》2009,603(21):3205-3211
Bis-alkynylated oligoethyleneglycol (OEG) and a monopropargyl-functionalized perfluorinated ethylene glycol (FEG) were clicked to azide-functionalized gold surface (Au–N3) at room temperature via the well known 1,3 cycloaddition click chemical reaction. The Au–N3 substrate was obtained by nucleophilic attack of NaN3 on gold substrates modified by the electrochemical reduction of the , +N2–C6H4–CH2Br diazonium salt. This electrochemical process yields aryl layer-modified gold of the type Au–C6H4–CH2Br (hereafter Au–Br). The untreated and modified gold plates were examined by XPS, PMIRRAS and contact angle measurements. XPS brought evidence for electrografting aryl layers by the detection of Br3d; azide functionalization by the increase of the N/Br atomic ratio; and click reaction of OEG with Au–N3 by the increase of O/N ratio. In addition, the perfluorinated plate (Au-FEG) exhibited F1s and characteristic C1s peaks from -(CF2)7- chain and terminal CF3. Infra red spectroscopy (PMIRRAS) evidenced (i) grafting N3 to Au–Br; (ii) characteristic stretching bands, from ethylene glycol units, C–O–C (1100–1300 cm−1); CF2 (1000–1100 cm−1) and CF3 (1100–1350 cm−1) from FEG grafts; and (iii) suppression of alkynyl bands from OEG and FEG after surface click chemistry. More importantly, PMIRRAS results support an important bridging of the bispropargyl oligoethylene glycol at the gold surface. Water drop contact angles were found to be 48.7° and 83.0° for Au-OEG and Au-FEG, respectively, therefore highlighting the control over the hydrophilic/hydrophobic character of the clicked substrate.This work shows that clicking macromolecules to grafted, diazonium salt-derived aryl layers is a novel, simple and valuable approach for designing robust, functional surface organic coatings. 相似文献
192.
Martínez-Viviente E Pregosin PS Vial L Herse C Lacour J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(12):2912-2918
1H, (19)F and (31)P pulsed field gradient spin-echo (PGSE) diffusion studies on chiral organic salts that contain hexacoordinate phosphate anions, namely tris(tetrachlorobenzenediolato)phosphate(V) (TRISPHAT) and bis(tetrachlorobenzenediolato)mono([1,1']binaphthalenyl-2,2'diolato)-phosphate(V) (BINPHAT), are reported. The first example of the dependence of a diffusion value on diastereomeric structure is presented. Marked solvent and concentration effects on the diffusion constants (D) of these salts are noted and the question of ion pairing is discussed. 相似文献
193.
A new, one-step procedure for the generation of azomethine ylides, 4 and 20, via chloroiminium salts, 3 and 19, is reported. The generation of the azomethine ylides was confirmed by their trapping with dimethyl acetylenedicarboxylate (DMAD) which, upon spontaneous 1,4-dehydrochlorination, gave the corresponding pyrroles 17 and 21. 相似文献
194.
Amit S. Nagare Arpan Manna Pramod D. Sonawane Anil Kumar 《Journal of Physical Organic Chemistry》2015,28(11):665-673
Prevailing classification of salts based on their effect in solubility and stability of proteins in aqueous solution predicts that tetraalkylammonium salts, guanidinium chloride (GnCl), LiClO4 act as salting‐in (S/I) and LiCl, NaCl act as salting‐out (S/O) in aqueous conditions. In the same context the behaviour of GnCl, LiClO4 and LiCl are contradictory in polar solvents like ethylene glycol and formamide. In these solvents, expected salt effect shows just opposite nature from their usual expectation. However, in the aqueous solution salts like tetraalkylammonium halide (R4NX, R = alkyl group, X = Br group) behave like salting‐in salts. The physicochemical origin of the salting in effect of R4NX type of salts has been discussed elaborately in the present work. The role of cations in terms of substitution of various alkyl groups on R4NX has been systematically presented here on the basis of experimental kinetic and thermodynamic studies. The abnormal behaviour of R4NX salts in aqueous solution has also been explained by the Setschenov equation (ks) and Δμsolvation values, which highlights their individual nature out of common properties of R4NX. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
195.
In the crystallographic literature, there is an ever-increasing number of publications on crystals that are referred to as ‘new non-linear optical materials’, many of them reporting salts of amino acids. However, the term NLO material is used improperly in most cases. In fact, the establishment of any crystal species as such a material requires several experimental and computational procedures, which are seldom satisfied when characterizing a supposedly new species. Here, some frequent hazards and problems are addressed and observations of papers reporting amino acid compounds as supposedly new NLO materials are made. 相似文献
196.
Synthesis Pb1‐xBi4+xTi4‐xMnxO15 compounds (0 ≤ × ≤ 1) were carried out by molten salts method using eutectic mixture of Na2SO4/K2SO4 salts (1:1 molar ratio) as the flux. The samples were characterized by X‐ray powder diffraction and refined by Le Bail method using Rietica program. The refinement results revealed that the compounds with the composition 0 ≤ x ≤ 0.6 formed Aurivillius phase with the space group A21am while the other composition (x ≥ 0.8) showed another phase beside A21am. The ratio b/a of the lattices constants for all the samples are larger than 1 indicating the direction of the orthorhombic along the b axis of their cells. The lattice parameters and volume of the unit cells decrease as the Mn content increasing from x = 0 to 0.6, for x ≥ 0.8 a second phase were observed. The morphologies of Pb1‐xBi4+xTi4‐xMnxO15 samples were observed by SEM and show plate‐like aggregate crystals, typical of layered compounds belonging to the Aurivillius phase. 相似文献
197.
Yusuke Kumatabara Shiho Kaneko Satoshi Nakata Prof. Dr. Seiji Shirakawa Prof. Dr. Keiji Maruoka 《化学:亚洲杂志》2016,11(15):2126-2129
A piperidine‐derived tetraalkylammonium salt with a non‐coordinating counteranion worked as an effective hydrogen‐bonding catalyst in an aza‐Diels–Alder reaction of imines and a Danishefsky diene. The hydrogen‐bonding interaction between the ammonium salt and an imine was observed as part of a 1H NMR titration study. 相似文献
198.
Kenneth S. Pitzer John R. Peterson Leonard F. Silvester 《Journal of solution chemistry》1978,7(1):45-56
The extensive data for the osmotic coefficients, heats of dilution, and densities of aqueous solutions of rare earth chlorides, nitrates, and perchlorates are fitted to a single type of equation found satisfactory for many other solutes Good agreement is obtained. The various parameters do not show simple trends with cation radius. While there are some plausible explanations of these complexities, the total picture is far from clear. 相似文献
199.
Eli Ruckenstein Xiaonong Chen 《Journal of polymer science. Part A, Polymer chemistry》2000,38(5):818-825
Alkali‐ and alkali‐earth‐metal salts of dicyclopentadiene dicarboxylic acid (DCPDCA) were prepared and employed as crosslinkers for chlorine‐containing polymers such as polychloromethylstyrene (PCMS), chlorinated polypropylene (CPP), polyepichlorohydrin (PECH), and poly(vinyl chloride) (PVC). Thermally reversible covalent crosslinks (i.e., DCPD bridges) between polymer chains were generated through esterification between the chlorine–carbon bonds of the polymer and the carboxylic salt groups of the crosslinker. The crosslinking reactivity decreased in the following sequence: K > Na > LiDCPDCA > alkali‐earth‐metal salts of DCPDCA. In addition, PCMS and CPP had higher gelation rates than PECH and PVC. Good flowability at about 195 °C and solubility in maleimide‐containing dichlorobenzene on heating indicated that the crosslinked PCMS and CPP exhibited thermally reversible crosslinking because of dimer/monomer (cyclopentadiene) conversion of DCPD moieties via reversible Diels–Alder cycloaddition. Samples of PECH and PVC crosslinked by the alkali salts of DCPDCA were insoluble even when heated in maleimide‐containing dichlorobenzene. However, these crosslinked polymers could be dissolved partially after the same treatment when the crosslinker was an alkali‐earth‐metal salt of DCPDCA. Thermal degradation such as dehydrochlorination of the PECH and PVC might have been responsible for uncontrolled crosslinking because these two polymers are known to be thermally unstable. The unreacted COOK, COONa, or COOLi of the crosslinkers might have initiated base‐induced dehydrochlorination when PECH and PVC were heated at high temperatures. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 818–825, 2000 相似文献
200.
Dr. Andrey Belyaev Prof. Pi-Tai Chou Prof. Igor O. Koshevoy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(2):537-552
Tunable electron-accepting properties of the cationic phosphorus center, its geometry and unique preparative chemistry that allows combining this unit with diversity of π-conjugated motifs, define the appealing photophysical and electrochemical characteristics of organophosphorus ionic chromophores. This Minireview summarizes the achievements in the synthesis of the π-extended molecules functionalized with P-cationic fragments, modulation of their properties by means of structural modification, and emphasizes the important effect of cation-anion interactions, which can drastically change physical behavior of these two-component systems. 相似文献