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71.
Franziska Lauer Sabrina Diehn Stephan Seifert Janina Kneipp Volker Sauerland Cesar Barahona Steffen Weidner 《Journal of the American Society for Mass Spectrometry》2018,29(11):2237-2247
Mixtures of pollen grains of three different species (Corylus avellana, Alnus cordata, and Pinus sylvestris) were investigated by matrix-assisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-TOF imaging MS). The amount of pollen grains was reduced stepwise from >?10 to single pollen grains. For sample pretreatment, we modified a previously applied approach, where any additional extraction steps were omitted. Our results show that characteristic pollen MALDI mass spectra can be obtained from a single pollen grain, which is the prerequisite for a reliable pollen classification in practical applications. MALDI imaging of laterally resolved pollen grains provides additional information by reducing the complexity of the MS spectra of mixtures, where frequently peak discrimination is observed. Combined with multivariate statistical analyses, such as principal component analysis (PCA), our approach offers the chance for a fast and reliable identification of individual pollen grains by mass spectrometry. 相似文献
72.
Hannes Kulla Sebastian Haferkamp Irina Akhmetova Mathias Röllig Dr. Christiane Maierhofer Prof. Dr. Klaus Rademann Dr. Franziska Emmerling 《Angewandte Chemie (International ed. in English)》2018,57(20):5930-5933
We present an in situ triple coupling of synchrotron X‐ray diffraction with Raman spectroscopy, and thermography to study milling reactions in real time. This combination of methods allows a correlation of the structural evolution with temperature information. The temperature information is crucial for understanding both the thermodynamics and reaction kinetics. The reaction mechanisms of three prototypical mechanochemical syntheses, a cocrystal formation, a C?C bond formation (Knoevenagel condensation), and the formation of a manganese‐phosphonate, were elucidated. Trends in the temperature development during milling are identified. The heat of reaction and latent heat of crystallization of the product contribute to the overall temperature increase. A decrease in temperature occurs via release of, for example, water as a by‐product. Solid and liquid intermediates are detected. The influence of the mechanical impact could be separated from temperature effects caused by the reaction. 相似文献
73.
Modular Functionalization of Arenes in a Triply Selective Sequence: Rapid C(sp2) and C(sp3) Coupling of C−Br,C−OTf,and C−Cl Bonds Enabled by a Single Palladium(I) Dimer 下载免费PDF全文
Dr. Sinead T. Keaveney Gourab Kundu Prof. Dr. Franziska Schoenebeck 《Angewandte Chemie (International ed. in English)》2018,57(38):12573-12577
Full control over multiple competing coupling sites would enable straightforward access to densely functionalized compound libraries. Historically, the site selection in Pd0‐catalyzed functionalizations of poly(pseudo)halogenated arenes has been unpredictable, being dependent on the employed catalyst, the reaction conditions, and the substrate itself. Building on our previous report of C?Br‐selective functionalization in the presence of C?OTf and C?Cl bonds, we herein complete the sequence and demonstrate the first general arylations and alkylations of C?OTf bonds (in <10 min), followed by functionalization of the C?Cl site (in <25 min), at room temperature using the same air‐ and moisture‐stable PdI dimer. This allowed the realization of the first general and triply selective sequential C?C coupling (in 2D and 3D space) of C?Br followed by C?OTf and then C?Cl bonds. 相似文献
74.
An all-glass miniaturized light-phase rotary perforator for the enrichment of polar compounds has been modified/miniaturized
and applied. Its application is demonstrated here for the analysis of nitrophenols and dinitrophenols from low-concentration/low-volume
samples. For the method development of high-performance liquid chromatography–mass spectrometry (MS) four eluents were tested:
(1) water–methanol, (2) acetic acid–methanol, (3) trifluoroacetic acid–methanol and (4) water–acetonitrile. The last eluent
mentioned was used for the subsequent investigation of samples from field experiments. Detection limits varied between 1 ng
and 50 pg. The relative standard deviation in repeated measurements was below 15%, corresponding to a good reproducibility.
Recoveries ranged between 31 and 100%, showing a significant dependence on the extraction time and the final volume of the
sample after evaporation. Quantification was carried out by using deuterated 4-nitrophenol and 2,4-dinitrophenol as standards
and applying previously determined response factors. Structure determination of further substances under atmospheric pressure
chemical ionization was performed by a first screening with a source collision-induced dissociation, followed by the definite
analysis by MS
n
. The first results are shown for cloud water, fog water and rainwater samples from different locations. 相似文献
75.
Pb(18‐crown‐6)Cl2 and Hg(18‐crown‐6)I2 are obtained as transparent colourless crystals of needle and hexagonal shape, respectively, by isothermal evaporation of their dichloromethane solutions. Pb(18‐crown‐6)Cl2 crystallizes with the trigonal crystal system [ , no. 148, a = b = 1176.3(2), c = 1191.8(3) pm, V = 1428.2(5) 106·pm3, Z = 3] whereas Hg(18‐crown‐6)I2 crystallizes with the orthorhombic crystal system (Pnma, no. 62, a = 1613.9(2) pm, b = 2822.2(5) pm, c = 841.3(1) pm, V = 3832(1)106·pm3, Z = 8). Both compounds are characterized by linear MX2 (HgI2 or PbCl2) molecular units which are encrypted by the crown ether. In both cases, the divalent metal ion resides in the middle of the crown ether resulting in a hexagonal bipyramidal coordination environment for the metal cations. The molecular symmetry comes close to D3d. Hg(18‐crown‐6)I2 and Pb(18‐crown‐6)Cl2 differ in the way the single MX2@18‐crown‐6 units are packed. Whereas the Hg(18‐crown‐6)I2 molecules are arranged in a (distorted) cubic closest packing, the Pb(18‐crown‐6)Cl2 molecules adopt a hexagonal closest packing. 相似文献
76.
Amit Dahiya Markus D. Schoetz Prof. Dr. Franziska Schoenebeck 《Angewandte Chemie (International ed. in English)》2023,62(43):e202310380
Reported herein is a fully orthogonal olefination, which involves the site- and E-selective coupling of aryl germanes with alkenes, tolerating otherwise widely employed coupling handles such as aromatic (pseudo)halogens (C−I, C−Br, C−Cl, C−F, C−OTf, C−OSO2F), silanes and boronic acid derivatives as well as alternative functionalities. This unprecedented [Ge]-based oxidative Heck coupling proceeds at room temperature with high speed (10 min to 2 hours) and operational simplicity owing to its base-free and air-tolerant features. 相似文献
77.
Dr. Franziska Kreuzer Dr. Elena Mena-Osteritz Prof. Peter Bäuerle 《European journal of organic chemistry》2023,26(27):e202300358
Dithienopyrazines are only scarcely used as building blocks in organic electronic materials. Here, we report efficient preparation and investigation of syn- and anti-dithienopyrazines, which were functionalized with triaraylamine units to provide different series of donor-acceptor-donor-type materials. The characterization of the optoelectronic properties resulted in valuable structure-property relationships and allowed for the elucidation of the influence of structural effects such as core structure (syn vs anti), type of substituents (directly arylated vs ethynylated aryl), and substitution pattern (α,α’- vs β,β’- vs fourfold substitution). Finally, first application of a dithienopyrazine derivative as model for hole-transport materials tailored for organic electronic devices has been realized. 相似文献
78.
Mechanochemical Synthesis of 3d Transition‐Metal–1,2,4‐Triazole Complexes as Precursors for Microwave‐Assisted and Thermal Conversion to Coordination Polymers with a High Influence on the Dielectric Properties 下载免费PDF全文
Franziska A. Brede Dr. Johanna Heine Prof. Dr. Gerhard Sextl Prof. Dr. Klaus Müller‐Buschbaum 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(8):2708-2718
The complexes [MCl2(TzH)4] (M=Mn ( 1 ), Fe ( 2 ); TzH=1,2,4‐1H‐triazole) and [ZnCl2(TzH)2] ( 3 ) have been obtained by mechanochemical reactions of the corresponding divalent metal chloride and 1,2,4‐1H‐triazole. They were successfully used as precursors for the formation of coordination polymers either by a microwave‐assisted reaction or by thermal conversion. For manganese, the conversion directly yielded [MnCl2TzH] ( 4 ), whereas for the iron‐containing precursor, [FeCl2TzH] ( 6 ), was formed via the intermediate coordination polymer [FeCl(TzH)2]Cl ( 5 ). For cobalt, the isotypic polymer [CoCl(TzH)2]Cl ( 7 ) was obtained, but exclusively by a microwave‐induced reaction directly from CoCl2. The crystal structures were resolved from single crystals and powders. The dielectric properties were determined and revealed large differences in permittivity between the precursor complexes and the rigid chain‐like coordination polymers. Whereas the monomeric complexes exhibit very different dielectric behaviour, depending on the transition metal, from “low‐k” to “high‐k” with the permittivity ranging from 4.3 to >100 for frequencies of up to 1000 Hz, the coordination polymers and complexes with strong intermolecular interactions are all close to “low‐k” materials with very low dielectric constants up to 50 °C. Therefore, the conversion procedures can be used to deliberately influence the dielectric properties from complex to polymer and for different 3d transition‐metal ions. 相似文献
79.
Franziska Fischer Sebastian Greiser Dr. Dietmar Pfeifer Prof. Dr. Christian Jäger Prof. Dr. Klaus Rademann Dr. Franziska Emmerling 《Angewandte Chemie (International ed. in English)》2016,55(46):14281-14285
Benzamide has been known for its polymorphism for almost 200 years. Three polymorphic forms are described. To date, it was only possible to crystallize a metastable form in a mixture together with the thermodynamically most stable form I. A complete transformation of form I into the metastable form III by mechanochemical treatment has been achieved. Catalytic amounts of nicotinamide seeds were used to activate the conversion by mechanochemical seeding. NMR experiments indicated that the nicotinamide molecules were incorporated statistically in the crystal lattice of benzamide form III during the conversion. The transformation pathway was evaluated using in situ powder X‐ray diffraction. 相似文献
80.