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211.
Walter Maringgele Sven Dielkus Regine Herbst-Irmer H. Michaelsen Anton Meller 《Journal of organometallic chemistry》1994,470(1-2):23-29
The reaction of 2,3-dimethylbuta-1,3-diene or 2-methylbuta-1,3-diene with Na/K-alloy and dichloro(diisopropylamino)borane in n-hexane yielded the 1-bora-cyclopent-3-enes, A and II, and 1-bora-cyclonona-1,3-diene, I, respectively. Cycloocta-3,7-diene reacts with dibalogeno(diorganylamino)boranes and Na/K-alloy in n-hexane to yield the 9-bora-bicyclo[4,2,1]non-7-enes III, V, VI and the 1,6-bis(diorganylaminofluoroboryl)-cyclooct-7-enes IV and VH. When 1,2-dimethoxyethane was the solvent, only the dimeric cyclooctene, C, was obtained. The compounds were characterized by elemental analyses and spectroscopy [MS; NMR (1H, 11B, 13C, 19F)]. An X-ray analysis is presented for I, MNDO-calculations have been carried out for III and III. 相似文献
212.
Stolker AA Niesing W Hogendoorn EA Versteegh JF Fuchs R Brinkman UA 《Analytical and bioanalytical chemistry》2004,378(4):955-963
LC–MS–MS has been performed with triple-quadrupole (QqQ) and quadrupole-time of flight (Q-ToF) instruments and has been used for screening and confirmation of pharmaceuticals in surface, drinking, and ground water. Screening was based on monitoring of one specific MS–MS ion of the target compounds. Confirmation of the identity of the pharmaceuticals was based either on the monitoring of two specific MS–MS ions and calculation of the ratio of their intensities, or on the exact masses of MS–MS product ions obtained for a molecular ion by use of LC–Q-ToF MS. The set of pharmaceuticals included four analgesics (acetylsalicylic acid, diclofenac, ibuprofen, and paracetamol), three antibiotics (sulfamethoxazole, erythromycin, and chloramphenicol), five blood-lipid regulators and beta-blockers (fenofibrate, bezafibrate, clofibric acid, bisoprolol, and metoprolol), and the anti-epileptic drug carbamazepine. Limits of quantification ranged from 5 to 25 ng L–1. Fifty-six samples were analysed and residues of the pharmaceuticals were detected in almost all surface and groundwater and in some drinking water samples. The identity of the compounds could be confirmed by use of both QqQ- and Q-ToF-based LC–MS–MS. However, the latter technique has the distinct advantage that a large number of pharmaceuticals can be screened and confirmed at low concentrations (1–100 ng L–1) in one run. 相似文献
213.
Pasquier N Keul H Heine E Moeller M Angelov B Linser S Willumeit R 《Macromolecular bioscience》2008,8(10):903-915
Cationic amphiphilic polymers were prepared from PEI and functional ethylene carbonates bearing cationic, hydrophobic or amphiphilic groups. The polymers are designed to exhibit antimicrobial properties. In a one-step addition, different functional ethylene carbonates were added to react with the primary amine groups of PEI. The water soluble polymers were studied regarding their ability to form soluble aggregates. Their hydrodynamic radii, their inhibition potential against proliferation of E. coli and their hemolytic potential were determined. A structure-property relationship was established by analyzing the antimicrobial activity as a function of the ratio of alkyl to cationic groups, length of the alkyl chains, and molecular weight of the PEI. 相似文献
214.
Angelov B Angelova A Garamus VM Lebas G Lesieur S Ollivon M Funari SS Willumeit R Couvreur P 《Journal of the American Chemical Society》2007,129(44):13474-13479
The structural evolution of a diamond-type bicontinuous lipid cubic phase upon application of thermal and chemical (hydration agent) stimuli is investigated by means of small-angle neutron (SANS) and X-ray scattering (SAXS). The soft-matter cubic architecture responds by dramatic swelling (DLarge cubic structure) upon incorporation of a hydration-enhancing guest component (octyl glucoside) at low and ambient temperatures, the aqueous channel diameter increasing twice to approximately 7 nm. DLarge appears to be built up from an assembly of cubosomic domains, which may coexist with an amphiphilic lamellae domain at low temperatures. The chemical stimulus concentration can be selected as to tune the hydration of the nanochannels in the DLarge phase and its transformation into a DNormal phase at temperatures above the body temperature. Two-dimensional SANS images recorded upon heating scan reveal growth of spontaneously oriented domains of single-crystal cubic nature. Phase separation and squeezing out the guest-hydrating agent from the higher-curvature regions of the amphiphilic bilayer suggest a possible mechanism for the established transformations. The order-order structural transition, cubic DLarge-cubic DNormal, is found to be reversible upon cooling. The obtained results put forward a structure-based concept for release of encapsulated guest molecules from stimuli-responsive and self-regulated cubosomic nanocarriers. 相似文献
215.
Treatment of [MoO2(eta2-Pz)2] (Pz = 3,5-di-tert-butylpyrazolate) with the diketiminate ligand NacNacH (NacNac = CH[C(Me)NAr]2-, Ar = 2,6-Me2C6H3) at 55 degrees C leads under reduction of the metal to the formation of the dimeric molybdenum(V) compound [{MoO2(NacNac)}2] (1). The compound was characterized by spectroscopic means and by X-ray crystal structure analysis. The dimer consists of a [Mo2O4]2+ core with a short Mo-Mo bond (2.5591(5) A) and one coordinated diketiminate ligand on each metal atom. The reaction of [MoO2(eta2-Pz)2] with NacNacH in benzene at room temperature leads to a mixture of 1 and the monomeric molybdenum(VI) compound [MoO2(NacNac)(eta2-Pz)] (2). From such solutions, yellow crystals of 2 suitable for X-ray structural analysis were obtained revealing the coordination of one bidentate NacNac and one eta2-coordinate Pz ligand. This renders the two oxo groups inequivalent. Further high oxidation state molybdenum compounds containing the NacNac ligand were obtained by the reaction of [Mo(NAr)2Cl2(dme)] (Ar = 2,6-Me2C6H3) and [Mo(N-t-Bu)2Cl2(dme)] (dme = dimethoxyethane) with 1 equiv of the potassium salt NacNacK forming [Mo(NAr)2Cl(NacNac)] (3) and [Mo(N-t-Bu)2Cl(NacNac)] (4), respectively, in good yields. The X-ray structure analysis of 3 revealed a penta-coordinate compound where the geometry is best described as trigonal-bipyramidal. 相似文献
216.
Temperature, pH, and ionic strength induced changes of the swelling behavior of PNIPAM-poly(allylacetic acid) copolymer microgels 总被引:1,自引:0,他引:1
Karg M Pastoriza-Santos I Rodriguez-González B von Klitzing R Wellert S Hellweg T 《Langmuir : the ACS journal of surfaces and colloids》2008,24(12):6300-6306
The volume phase transition of colloidal microgels made of N-isopropylacrylamide (NIPAM) is well-studied and it is known that the transition temperature can be influenced by copolymerization. A series of poly( N-isopropylacrylamide- co-allylacetic acid) copolymers with different contents of allylacetic acid (AAA) was synthesized by means of a simple radical polymerization approach. The thermoresponsive behavior of these particles was studied using dynamic light scattering (DLS). Further characterization was done by employing transmission electron microscopy (TEM) and zeta potential measurements. TEM observations reveal the approximately spherical shape and low polydispersity of the copolymer particles. In addition, the measured zeta potentials provide information about the relative surface charge. Since these copolymers are much more sensitive to external stimuli such as pH and ionic strength than their pure PNIPAM counterparts, the volume phase transition was investigated at two different pH values and various salt concentrations. At pH 10 for the copolymer microgels with the highest AAA content, a significant shift of the volume phase transition temperature toward higher values is found. For higher AAA content, a change in pH from 8 to 10 can induce a change in radius of up to 100 nm making the particles interesting as pH controlled actuators. 相似文献
217.
Dr. Mohd Asif Ansari Dr. Mursaleem Ansari Dr. Madhusudan K. Pandey Christian Köhler Dr. Regine Herbst-Irmer Prof. Dr. Dietmar Stalke Prof. Dr. Herbert W. Roesky 《欧洲无机化学杂志》2023,26(24):e202300209
Herein we report the reactions of 3,4,5,6-tetrafluoroterephthalonitrile ( 1 ) with bis(silylene) and bis(germylene) LE−EL [E=Si ( 2 ) and Ge( 3 ): L=PhC(NtBu)2)]. The reaction of LSi−SiL (L=PhC(NtBu)2) ( 2 ) with two equivalents of 1 resulted in an unprecedented oxidative addition of a C−F bond of 1 leading to disilicon(III) fluoride {L(4-C8F3N)FSi−SiF(4-C8F3N)L}( 4 ), wherein the Si−Si single bond was retained. In contrast, the reaction of LGe−GeL (L=PhC(NtBu)2) ( 3 ) with one equivalent of 1 resulted in the oxidative cleavage of Ge−Ge bond leading to L(4-C8F3N2)Ge ( 5 ) and LGeF ( 6 ). All three compounds ( 4 – 6 ) were characterized by NMR spectroscopy, EI-MS spectrometry, and elemental analysis. X-ray single-crystal structure determination of compound 4 unequivocally established that the SiIII−SiIII bond remains uncleaved. 相似文献
218.
219.
Prinson P. Samuel Roman Neufeld Kartik Chandra Mondal Herbert W. Roesky Regine Herbst-Irmer Dietmar Stalke Serhiy Demeshko Franc Meyer Vallyanga Chalil Rojisha Susmita De Pattiyil Parameswaran A. Claudia Stückl Wolfgang Kaim Jonathan H. Christian Jasleen K. Bindra Naresh S. Dalal 《Chemical science》2015,6(5):3148-3153
Cr(i)Cl is a very unstable species. The present work describes the stabilisation of Cr(i)Cl in the low coordinate environment of cyclic alkyl(amino) carbene ligands and its synthetic application to yield an unprecedented cationic complex with a two coordinate Cr(i). One electron reduction of (cAAC)2CrCl2 (1) with equivalent amount of KC8 results in the formation of (cAAC)2CrCl (2), with a distorted trigonal planar configuration at the metal centre. SQUID, EPR and theoretical studies reveal a Cr(i) centre with S = 5/2 spin ground state for 2. It represents the first example of a mononuclear Cr complex showing slow relaxation of magnetisation under an applied magnetic field. The chlorine atom in 2 is expected to be prone to further reactions with appropriate reagents. This qualifies 2 as a promising precursor for the preparation of various interesting complexes with Cr(i) in a low coordinate environment. The first example of this metathesis reaction is observed when 2 is treated with Na[B(C6H3(CF3)2)4] resulting in [(cAAC)2Cr]+[B(C6H3(CF3)2)4]–, a linear cationic complex with two coordinate Cr(i) and an S = 5/2 spin ground state. 相似文献
220.
Jochen Jung Florian Benner Dr. Regine Herbst-Irmer Prof. Dr. Selvan Demir Prof. Dr. Dietmar Stalke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(48):12310-12319
Lanthanide ions are particularly well-suited for the design of single-molecule magnets owing to their large unquenched orbital angular momentum and strong spin-orbit coupling that gives rise to high magnetic anisotropy. Such nanoscopic bar magnets can potentially revolutionize high-density information storage and processing technologies, if blocking temperatures can be increased substantially. Exploring non-classical ligand scaffolds with the aim to boost the barriers to spin-relaxation are prerequisite. Here, the synthesis, crystallographic and magnetic characterization of a series of each isomorphous mono- and dinuclear lanthanide (Ln=Gd, Tb, Dy, Ho, Er) complexes comprising tetraimido sulfate ligands are presented. The dinuclear Dy complex [{(thf)2Li(NtBu)2S(tBuN)2DyCl2}2 ⋅ ClLi(thf)2] ( 1c ) shows true signatures of single-molecule magnet behavior in the absence of a dc field. In addition, the mononuclear Dy and Tb complexes [{(thf)2Li(NtBu)2S(tBuN)2LnCl2(thf)2] ( 2b , c ) show slow magnetic relaxation under applied dc fields. 相似文献