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241.
Martin Tsvetkov Maria Milanova Laura C. J. Pereira Jaão C. Waerenbourgh Zara Cherkezova-Zheleva Joana Zaharieva Ivan Mitov 《Chemical Papers》2016,70(12):1600-1610
The spinel-type ferrites NiFe2O4 and Zn0.5Ni0.5Fe2O4 modified by lanthanide ions Eu3+ and Tb3+ were prepared by a sol—gel process with propylene oxide as a gelating agent. The phase homogeneity of the samples was tested by XRD and Mössbauer spectroscopy. Transmission electronic microscopy used for characterisation of the morphology of the samples revealed nanosized powdered samples with a narrow distribution of particle sizes. It was noted that the presence of Ln3+ ions influenced the magnetic properties of nanosized NiFe2O4 and Ni0.5Zn0.5Fe2O4 ferrites. The dependence of the magnetic properties of the samples on the rare-earth doping may be explained by the different grain sizes. The saturation magnetisation tends to decrease with increasing rare-earth doping and decreasing crystallite size. A similar trend was observed for the coercive field, with the exception of the Tb3+-doped Zn0.5Ni0.5Fe2O4 where it remained the same as in the pure ferrite. 相似文献
242.
Laura Calió Dr. Samrana Kazim Prof. Michael Grätzel Dr. Shahzada Ahmad 《Angewandte Chemie (International ed. in English)》2016,55(47):14522-14545
The pressure to move towards renewable energy has inspired researchers to look for ideas in photovoltaics that may lead to a major breakthrough. Recently the use of perovskites as a light harvester has lead to stunning progress. The power conversion efficiency of perovskite solar cells is now approaching parity (>22 %) with that of the established technology which took decades to reach this level of performance. The use of a hole transport material (HTM) remains indispensable in perovskite solar cells. Perovskites can conduct holes, but they are present at low levels, and for efficient charge extraction a HTM layer is a prerequisite. Herein we provide an overview of the diverse types of HTM available, from organic to inorganic, in the hope of encouraging further research and the optimization of these materials. 相似文献
243.
Dr. Sabina Rodríguez‐Hermida Dr. Ana Belén Lago Arantxa Pino‐Cuevas Dr. Adelheid Hagenbach Dr. Laura Cañadillas‐Delgado Prof. Rosa Carballo Prof. Ulrich Abram Prof. Ezequiel M. Vázquez‐López 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(5):1847-1853
Materials based on the cationic copper(II) hexanuclear 18‐membered metallacrown [18‐MC ‐6]6+ (2phH=2‐piconyl hydrazide) and tetrafluoroborate, perchlorate, nitrate, sulfate, and perrhenate anions were prepared by an easy method in aqueous medium. Single‐crystal X‐ray characterization of six members of this new family of complexes showed that the anions are attached to the metallacrown by direct coordination to a copper cation or by hydrogen‐bonding interaction with the center of the hexamer. The stable cationic nature of the complexes and their ability to bind different anions allows them to adsorb and immobilize environmentally relevant anions such as MO4? (M=Tc, Re). The MO4? trapping capacities suggest that these materials would be useful in the treatment of oxoanionic contaminants in water. 相似文献
244.
Dr. Lukiana L. Anka‐Lufford Kierra M. M. Huihui Dr. Nicholas J. Gower Dr. Laura K. G. Ackerman Prof. Dr. Daniel J. Weix 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(33):11564-11567
Cross‐electrophile coupling of aryl halides with alkyl halides has thus far been primarily conducted with stoichiometric metallic reductants in amide solvents. This report demonstrates that the use of tetrakis(dimethylamino)ethylene (TDAE) as an organic reductant enables the use of non‐amide solvents, such as acetonitrile or propylene oxide, for the coupling of benzyl chlorides and alkyl iodides with aryl halides. Furthermore, these conditions work for several electron‐poor heterocycles that are easily reduced by manganese. Finally, we demonstrate that TDAE addition can be used as a control element to ‘hold’ a reaction without diminishing yield or catalyst activity. 相似文献
245.
Barbara Berkes Kristóf Ozsváth Laura Molnár Tamás Gáti Tamás Holczbauer György Kardos Tibor Soós 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(50):18101-18106
We report an expedient approach to highly functionalized cis‐ and trans‐decalines that could function as key structural subunits toward the synthesis of various classes of terpenoids. Key to the strategy is an organocatalyzed Robinson annulation reaction of the Nazarov reagent that affords chiral enone building blocks with high enantioselectivities. The quaternary carbon stereogenic center can direct the subsequent reactions and allow the rapid and diastereoconvergent assembly of complex decalines with contiguous stereocenters. 相似文献
246.
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248.
Escola N Di Salvo F Haddad R Perissinotti L Eberlin MN Doctorovich F 《Inorganic chemistry》2007,46(12):4827-4834
Electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) data of a unique family of complexes of nitroso compounds coordinated to pentachloroiridate(III), [Cl5IrN(O)XR]2- (X=NH, S, CH and R=alkyl, aryl) are presented. These novel complexes are obtained by nucleophilic attack of primary amines, thiols. and alkenes to the coordinated nitrosyl. Despite their lability and low volatility, MS analysis of complexes of the type MN(O)X was done for the first time, complementing other spectroscopic techniques. The intrinsic dissociation chemistry of the gaseous diagnostic ions was studied via ESI-MS/MS and found to be very useful to confirm the proposed connectivities of the parent complexes. In particular, ESI-MS of their solutions allows the detection of series of diagnostic ions, mainly, [M-Cl]-, [M+K]-, [M-NO]-*, and [M-Cl+AcN]- (AcN=acetonitrile), which confirmed the identity of the analyzed complexes to be M=[Cl5IrN(O)XR]2-. Major fragments were formed by losses of NO or N(O)XR. ESI-MS and ESI-MS/MS measurements are therefore shown to be the proper techniques to complement the spectroscopic characterization of this important class of nitroso complexes. An interesting rearrangement that does not take place in solution was observed in the gaseous phase, and a plausible mechanism is discussed. 相似文献
249.
Douhal A Angulo G Gil M Organero JA Sanz M Tormo L 《The journal of physical chemistry. B》2007,111(19):5487-5493
In this contribution, we report on studies of rotational and diffusional dynamics of 7-hydroxyquinoline (7HQ) within a reverse micelle (RM) containing different amounts of water. Analyzed in terms of the wobbling-in-a-cone model, the data reveal structural and dynamical properties of the nanopool. We clearly observed three regions in the behavior of confined water molecules within the RM hosting a double proton-transfer reaction between the probe and water. This observation remarkably reproduces the change of calculated water density within this life-mimicking medium. The number of water molecules per AOT head in the transition regions changes from 2 to 5, the latter being very near to the full solvation number (6) of the RM heads. Moreover, the H-bonds breaking and making within the RM to give new structures of the probe strongly affect the environment fluidization in different extents, reflected in different relaxation times of these structures; however, they are of similar sizes. We discuss the role of RM confinement and the proton-transfer dynamics on the behavior of water and their relationships to the packing of water molecules in the studied range of concentrations. 相似文献
250.