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排序方式: 共有406条查询结果,搜索用时 218 毫秒
41.
Silke C. Wenzel Holger Hoffmann Jidong Zhang Laurent Debussche Sabine Haag‐Richter Michael Kurz Frederico Nardi Peer Lukat Irene Kochems Heiko Tietgen Dietmar Schummer Jean‐Paul Nicolas Loreley Calvet Valerie Czepczor Patricia Vrignaud Agnes Mühlenweg Stefan Pelzer Rolf Müller Mark Brnstrup 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(51):15781-15785
42.
Ansa‐Complexes of [Mn(η5‐C5H5)(η6‐C6H6)]: Preparation,Characterization, and Reactivity of [n]Manganoarenophanes (n=1, 2, 3) 下载免费PDF全文
Prof. Dr. Holger Braunschweig Dr. Alexander Damme Dr. Klaus Dück Dr. Marco Fuß Dr. Christian Hörl Dr. Thomas Kramer Dr. Ivo Krummenacher Dr. Thomas Kupfer Valerie Paprocki Christoph Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14797-14803
We report the synthesis of [n]manganoarenophanes (n=1, 2) featuring boron, silicon, germanium, and tin as ansa‐bridging elements. Their preparation was achieved by salt‐elimination reactions of the dilithiated precursor [Mn(η5‐C5H4Li)(η6‐C6H5Li)]?pmdta (pmdta=N,N,N′,N′,N′′‐pentamethyldiethylenetriamine) with corresponding element dichlorides. Besides characterization by multinuclear NMR spectroscopy and elemental analysis, the identity of two single‐atom‐bridged derivatives, [Mn(η5‐C5H4)(η6‐C6H5)SntBu2] and [Mn(η5‐C5H4)(η6‐C6H5)SiPh2], could also be determined by X‐ray structural analysis. We investigated for the first time the reactivity of these ansa‐cyclopentadienyl–benzene manganese compounds. The reaction of the distannyl‐bridged complex [Mn(η5‐C5H4)(η6‐C6H5)Sn2tBu4] with elemental sulfur was shown to proceed through the expected oxidative addition of the Sn?Sn bond to give a triatomic ansa‐bridge. The investigation of the ring‐opening polymerization (ROP) capability of [Mn(η5‐C5H4)(η6‐C6H5)SntBu2] with [Pt(PEt3)3] showed that an unexpected, unselective insertion into the Cipso?Sn bonds of [Mn(η5‐C5H4)(η6‐C6H5)SntBu2] had occurred. 相似文献
43.
A radical-mediated approach to metal-free alkene oxyamination is described. This method capitalizes on the unique reactivity of the amidoxyl radical in alkene additions to furnish a general difunctionalization using simple diisopropyl azodicarboxylate (DIAD) as a radical trap. This protocol capitalizes on the intramolecular nature of the process, providing single regioisomers in all cases. Difunctionalizations of cyclic alkenes provide trans oxyamination products inaccessible using current methods with high levels of stereoselectivity, complementing cis-selective oxyamination processes. 相似文献
44.
Kersten H Derpmann V Barnes I Brockmann KJ O'Brien R Benter T 《Journal of the American Society for Mass Spectrometry》2011,22(11):2070-2081
We report on the development of a novel atmospheric pressure photoionization setup and its applicability for in situ degradation
product studies of atmospherically relevant compounds. A custom miniature spark discharge lamp was embedded into an ion transfer
capillary, which separates the atmospheric pressure from the low pressure region in the first differential pumping stage of
a conventional atmospheric pressure ionization mass spectrometer. The lamp operates with a continuous argon flow and produces
intense light emissions in the VUV. The custom lamp is operated windowless and efficiently illuminates the sample flow through
the transfer capillary on an area smaller than 1 mm2. Limits of detection in the lower ppbV range, a temporal resolution of milliseconds in the positive as well as the quasi
simultaneously operating negative ion mode, and a significant reduction of ion transformation processes render this system
applicable to real time studies of rapidly changing chemical systems. The method termed capillary atmospheric pressure photo
ionization (cAPPI) is characterized with respect to the lamp emission properties as a function of the operating conditions,
temporal response, and its applicability for in situ degradation product studies of atmospherically relevant compounds, respectively. 相似文献
45.
Two fused thienoacene compounds with two-dimensional ring connectivity were synthesized, and their semiconducting properties were characterized. Both compounds have a crystal structure comprised of herringbone arrays of tight π-π stacks. Strong π-π interactions lead to self-assembly into well-defined crystalline thin films from the vapor phase for both compounds. Field effect transistors were fabricated, affording identical hole mobilities of 3.0 × 10(-3) cm(2)/(V s) and I(on/off) > 10(5). 相似文献
46.
Giglio BC Schmidt VA Alexanian EJ 《Journal of the American Chemical Society》2011,133(34):13320-13322
The dioxygenation of alkenes using molecular oxygen and a simple hydroxamic acid derivative has been achieved. The reaction system consists of readily prepared methyl N-hydroxy-N-phenylcarbamate and molecular oxygen with a radical initiator, offering an alternative to common dioxygenation processes catalyzed by precious transition metals. This transformation capitalizes on the unique reactivity profile of hydroxamic acid derivatives in radical-mediated alkene addition processes. 相似文献
47.
Threshold photoelectron spectra (TPESs) were obtained for naphthalene, anthracene, pyrene, 1,2-dihydronaphthalene, and 9,10-dihydroanthracene using imaging photoelectron photoion coincidence spectroscopy, from threshold to a photon energy of ~20 eV. Outer valence Green's function calculations at the OVGF∕cc-pVTZ level of theory were used to assign molecular orbitals to the observed TPES features. There is generally good agreement between the predicted and observed bands. Threshold regions for each molecule exhibit vibrational structure which is readily assigned based on previous PES studies. While the measured adiabatic ionization energies (IE(a)) for naphthalene, anthracene, and pyrene are in good agreement with previous works, new values are reported for the two dihydro species (1,2-dihydronaphthalene, 8.010 ± 0.010 eV and 9,10-dihydroanthracene, 8.335 ± 0.010 eV). A comparison is also made with the G3∕∕B3LYP composite method, which consistently overestimates the IE values by 0.06-0.09 eV. The double ionization energies for anthracene and pyrene have been measured to be 19.3 ± 0.2 and 19.8 ± 0.2 eV, respectively. 相似文献
48.
49.
Valerie Belton Stephen P. Vickers 《The Journal of the Operational Research Society》1993,44(9):883-896
Both Data Envelopment Analysis (DEA) and Multiple Criteria Analysis (MCA) can be used to assess the efficiency with which units perform similar tasks. This paper describes an approach derived from the integration of data envelopment analysis and a multi-attribute value function. This approach is implemented as a visual interactive decision support system, the use of which is illustrated by a practical application. The authors feel that this approach overcomes some of the limitations of the original DEA approach and, in particular, increases users' understanding of DEA. The approach is particularly well suited to the analysis of the efficiency of a small number of units. 相似文献
50.