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511.
Andrea Spolaor Paul Vallelonga Jacopo Gabrieli Natalie Kehrwald Clara Turetta Giulio Cozzi Luisa Poto John M. C. Plane C. Boutron Carlo Barbante 《Analytical and bioanalytical chemistry》2013,405(2-3):647-654
Iodine and bromine species participate in key atmospheric reactions including the formation of cloud condensation nuclei and ozone depletion. We present a novel method coupling a high-performance liquid chromatography with ion chromatography and inductively coupled plasma mass spectrometry, which allows the determination of iodine (I) and bromine (Br) species (IO 3 ? , I?, Br?, BrO 3 ? ) at the picogram-per-gram levels presents in Antarctic ice. Chromatographic separation was achieved using an IONPAC® AS16 Analytical Column with NaOH as eluent. Detection limits for I and Br species were 5 to 9 pg g?1 with an uncertainty of less than 2.5% for all considered species. Inorganic iodine and bromine species have been determined in Antarctic ice core samples, with concentrations close to the detection limits for iodine species, and approximately 150 pg g?1 for Br?. Although iodate (IO 3 ? ) is the most abundant iodine species in the atmosphere, only the much rarer iodide (I?) species was present in Antarctic Holocene ice. Bromine was found to be present in Antarctic ice as Br?. 相似文献
512.
Geetha T Langlais P Luo M Mapes R Lefort N Chen SC Mandarino LJ Yi Z 《Journal of the American Society for Mass Spectrometry》2011,22(3):457-466
Protein–protein interactions are key to most cellular processes. Tandem mass spectrometry (MS/MS)-based proteomics combined
with co-immunoprecipitation (CO-IP) has emerged as a powerful approach for studying protein complexes. However, a majority
of systematic proteomics studies on protein–protein interactions involve the use of protein overexpression and/or epitope-tagged
bait proteins, which might affect binding stoichiometry and lead to higher false positives. Here, we report an application
of a straightforward, label-free CO-IP-MS/MS method, without the use of protein overexpression or protein tags, to the investigation
of changes in the abundance of endogenous proteins associated with a bait protein, which is in this case insulin receptor
substrate-1 (IRS-1), under basal and insulin stimulated conditions. IRS-1 plays a central role in the insulin signaling cascade.
Defects in the protein–protein interactions involving IRS-1 may lead to the development of insulin resistance and type 2 diabetes.
HPLC-ESI-MS/MS analyses identified eleven novel endogenous insulin-stimulated IRS-1 interaction partners in L6 myotubes reproducibly,
including proteins play an important role in protein dephosphorylation [protein phosphatase 1 regulatory subunit 12A, (PPP1R12A)],
muscle contraction and actin cytoskeleton rearrangement, endoplasmic reticulum stress, and protein folding, as well as protein
synthesis. This novel application of label-free CO-IP-MS/MS quantification to assess endogenous interaction partners of a
specific protein will prove useful for understanding how various cell stimuli regulate insulin signal transduction. 相似文献
513.
514.
Supramolecular fibers of Ru(II) complexes act as efficient photosensitizers, photochemically generating methylviologen radical (MV.+) and then converting it quantitatively to doubly reduced methylviologen, (MV0), in the presence of triethanolamine. 相似文献
515.
Benjamin M. Mills Dr. Natalie Fey Dr. Tomasz Marszalek Prof. Wojciech Pisula Patrice Rannou Prof. Charl F. J. Faul 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):16950-16956
We have prepared a simple star‐shaped oligo(aniline) ( TDPB ) and characterised it in detail by MALDI‐TOF MS, UV/Vis/NIR spectroscopy, time‐dependent DFT, cyclic voltammetry and EPR spectroscopy. TDPB is part of an underdeveloped class of π‐conjugated molecules with great potential for organic electronics, display and sensor applications. It is redox active and reacts with acids to form radical cations. Acid‐doped TDPB shows behaviour similar to discotic liquid crystals, with X‐ray scattering investigations revealing columnar self‐assembled arrays. The combination of unpaired electrons and supramolecular stacking suggests that star‐shaped oligo(aniline)s like TDPB have the potential to form conducting nanowires and organic magnetic materials. 相似文献
516.
Nicholas Yu. Borovkov Svetlana V. Blokhina Alexis M. Kutepov Natalie Sh. Lebedeva Natalie A. Pavlycheva 《Thermochimica Acta》2005,430(1-2):167-171
Co-aggregation of fullerene C60 and thiophene has been studied calorimetrically in cyclohexene at 25 °C. The total aggregation heat is found to depend on initial concentration of thiophene and fall between −1.9 and −5.8 kJ mol−1. The corresponding thiophene/fullerene molar ratio (“co-aggregation number”) ranges from 7 to 12. The data are rationalized by formation of heteromolecular nanoaggregates with intermolecular contacts of both fullerene–thiophene and fullerene–fullerene types. A physical model describing interaction between fullerenes and π-donors in solution is substantiated and used to explain heterogeneity of composites containing fullerenes. 相似文献
517.
Mansfield NE Coles MP Hitchcock PB 《Dalton transactions (Cambridge, England : 2003)》2005,(17):2833-2841
Diisopropylcarbodiimide, (i)PrN[double bond, length as m-dash]C[double bond, length as m-dash]N(i)Pr, inserts into the lithium-phosphorus bond of in situ prepared "Ph(2)PLi(THF)(n)" to afford the lithium salt, [Li(Ph(2)PC{N(i)Pr}(2))(THF)(n)](x)(2a); alternatively, this compound can be made by deprotonation of the neutral phosphaguanidine, Ph(2)PC{N(i)Pr}{NH(i)Pr}(1a) with (n)BuLi. Displacement of the THF solvate in 2a is readily achieved with TMEDA to afford Li(Ph(2)PC{N(i)Pr}(2))(TMEDA)(3a). X-Ray crystallographic analyses show that 2a exists as a dimer in the solid state with a folded ladder structure and an N,N' chelating phosphaguanidinate, while 3a is monomeric with N,P-coordination of the ligand to lithium. Compound 2a reacts via a transmetallation pathway with AlMe(2)Cl to afford the dimethylaluminium complex, Al(Ph(2)PC{N(i)Pr}(2))Me(2)(4a), which can also be prepared by protonation of a methyl group of AlMe(3) using 1a. The formation of a series of dialkylaluminium compounds has been investigated employing this latter pathway using both 1a and the N,N'-dicyclohexyl analogue, Ph(2)PC{NCy}{NHCy}(1b), affording Al(Ph(2)PC{NR}(2))Et(2)(5a,b), Al(Ph(2)PC{NR}(2))(i)Bu(2)(6a,b) and the diphenylaluminium compound Al(Ph(2)PC{N(i)Pr}(2))Ph(2)(7a). The oily nature of most of the dialkyl compounds and high sensitivity to oxygen and moisture lead to difficulty in manipulation and characterization; however, NMR spectroscopy indicated highly pure products (>95%) upon removal of the solvent. The molecular structures of the crystalline examples 4a and 7a are reported, showing monomeric aluminium species with symmetrically chelating phosphaguanidinate ligands. The series of aluminium compounds AlLCl(2){L=[EC{NiPr}(2)](-): A, E=Me; B, E=Me(2)N; C, E=(Me(3)Si)(2)N and D, E=Ph(2)P} were investigated using density functional theory. In the more simple cases A and B, the delocalized electron density of the metallacycle was represented by a combination of the HOMO and an orbital of lower energy (A, HOMO-5; B, HOMO-6). The HOMO-1 in B was pi-bonded across the Me(2)N-C bond suggesting delocalization of electron density into the metallacycle. In the more complex systems C and D, delocalization within the metallacycle was less extensive due to the (Me(3)Si)(2)N- and Ph(2)P-moieties. A number of occupied orbitals in D, however, display phosphorus 'lone-pair' characteristics, indicating that these species have the potential to behave as Lewis bases in the formation of poly(metallic) systems. 相似文献
518.
Shklyarevskiy IO Jonkheijm P Stutzmann N Wasserberg D Wondergem HJ Christianen PC Schenning AP de Leeuw DM Tomović Z Wu J Müllen K Maan JC 《Journal of the American Chemical Society》2005,127(46):16233-16237
A magnetic field has been utilized for producing highly oriented films of a substituted hexabenzocoronene (HBC). Optical microscopy studies revealed large area HBC monodomains that covered the entire film, while wide-angle X-ray measurements showed that the HBC molecules are aligned with their planes along the applied field. On the basis of this method, solution-processed field-effect transistors (FET) have been constructed with charge carrier mobilities of up to 10(-3) cm2/V.s, which are significantly enhanced with respect to the unaligned material. Exceptionally high mobility anisotropies of 25-75 for current flow parallel and perpendicular to the alignment direction have been measured as a function of the channel length. Atomic force microscopy performed on the FET structures reveals fibril superstructures that are oriented perpendicularly to the magnetic field direction, consisting of molecular columns with a slippage angle of 40 degrees between the molecules. For channel lengths larger than 2.5 mum, the fibrils are smaller than the electrode spacing, which adversely affects the device performance. 相似文献
519.
Reaction of potassium 3{5}-(3′,4′-dimethoxyphenyl)pyrazolide with 2-bromopyridine in diglyme at 130°C for 3 days followed by an aqueous quench, affords 1-{pyrid-2-yl}-3-{3′,4′-dimethoxyphenyl}pyrazole (L2) in 69% yield after recrystallization from hot hexanes. Complexation of [Cu(NCMe)4]BF4 by 2 molar equivalents of 1-{pyrid-2-yl}-3-{2′,5′-dimethoxyphenyl}pyrazole (L1) or L2 in MeCN at room temperature, followed by concentration and crystallisation with Et2O, gives [Cu(L)2]BF4 L = L1, L2) in good yields. Treatment of AgBF4 with L1 or L2 in MeNO2 similarly gives [Ag(L)2]BF4 L = L1, L2); reaction of AfBF4 with L2 in MeCN gives a product of stoichiometry [Ag(L2)(NCMe)]BF4. The 1H NMR spectra of the [M(L)2]BF4 complexes show peaks arising from a single coordinated environment. The single crystal X-ray structure of [Cu(L1)2]BF4 shows a tetrahedral complex cation with Cu---N = 2.011(8), 2.036(8), 2.039(8), 2.110(8) Å. The CuI centre is close to tetrahedral, the dihedral angle between the least-squares planes formed by the Cu atom and the N donor atoms of the two ligands being 88.3(3)°. Complexation of hydrated Cu(BF4)2 by L2 in MeCN at room temperature yields [Cu(L2)2](BF4)2. The cyclic voltammograms of the three AgI complexes in MeCN/0.1 M Bu4n NPF6 are suggestive of extensive ligand dissociation in this solvent. 相似文献
520.
Eva Marie Freiberger Dr. Florian Späth Dr. Udo Bauer Dr. Fabian Düll Dr. Philipp Bachmann Johann Steinhauer Felix Hemauer Natalie J. Waleska Valentin Schwaab Prof. Dr. Hans-Peter Steinrück Dr. Christian Papp 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13172-13180
We present detailed studies on the covalent adsorption of molecular oxygen and atomic hydrogen on the hexagonal boron nitride (h-BN) nanomesh on Rh(111). The functionalization of this two-dimensional (2D) material was investigated under ultra-high vacuum conditions using synchrotron radiation-based in situ high-resolution X-ray photoelectron spectroscopy, temperature-programmed X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. We are able to provide a deep insight into the adsorption behavior and thermal stability of oxygen and hydrogen on h-BN/Rh(111). Oxygen functionalization was achieved via a supersonic molecular beam while hydrogen functionalization was realized using an atomic hydrogen source. Adsorption of the respective species was observed to occur selectively in the pores of h-BN leading to spatially defined modification of the 2D layer. The adsorption of the observed molecular oxygen species was found to be an activated process that requires high-energy oxygen molecules. Upon heating to 700 K, oxygen functionalization was observed to be almost reversible except for small amounts of boron oxides evolving due to the reaction of oxygen with the 2D material. Hydrogen functionalization of h-BN/Rh(111) was fully reversed upon heating to about 640 K. 相似文献