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71.
Armaforte E Mancebo-Campos V Bendini A Desamparados Salvador M Fregapane G Cerretani L 《Journal of separation science》2007,30(15):2401-2406
The hydrophilic extract of virgin olive oil contains several phenolic compounds such as simple phenols, lignans, and secoiridoids that have been widely studied in recent years. Interest in the hydrophilic extract has also been extended to the fraction of oxidized phenols that form during storage as a consequence of oxidative stress. The present investigation compares the two most commonly used extraction methods, namely liquid-liquid extraction and SPE, on fresh virgin olive oil and that kept at different temperatures in the presence of oxygen to promote the formation of oxidative products. The selective retention of these natural and oxidized phenolic compounds in relation to the extraction method was assessed. Quantification of eight identified phenolic molecules and 11 unknown peaks was performed by HPLC-DAD/MSD. 相似文献
72.
Seraglia R Molin L Tonidandel L Pucciarelli S Agostini M Urso ED Bedin C Quaia M Nitti D Traldi P 《Journal of mass spectrometry : JMS》2007,42(12):1606-1612
In an investigation devoted to the search for plasma markers for colorectal cancer (CRC), carried out by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, a series of overexpressed peptides were identified in the plasma of patients. Among them the peptide with molecular weight 903 Da was the most abundant one, with a mean +/- (SD) relative abundance of 37 +/- 17% and a frequency over 60%. Interestingly, also in plasma samples of ten subjects affected by familial adenomatous polyposis (FAP), the peptide with molecular weight 903 was overexpressed. In this investigation, MALDI/MS/MS experiments were carried out on the ion at m/z 904 detected in the MALDI mass spectra of CRC and FAP patients. The data analysis by SwissProt.2007.01.09 indicates that this peptide is due to the sequence RPPGFSPF, found in the kininogen-1 precursor, which is an alpha-2-thiol proteinase inhibitor. In the case of subjects affected by a particular FAP syndrome, the MALDI/MS/MS spectra were quite different from those obtained from CRC and FAP patients. In fact, two sequences have been evidenced: RPPGFSPF belonging to kininogen-1 precursor, and PRKSSSSR belonging to Forkhead box protein 01A. 相似文献
73.
Riccardo Destro Emanuele Ortoleva Giorgio Modena Lucia Pasquato Vittorio Lucchini 《Helvetica chimica acta》2001,84(4):860-866
Four‐membered ring thiosulfonium ions may be obtained quantitatively and under mild conditions by anionotropic rearrangement of C‐(tert‐butyl)‐substituted thiiranium ion precursors. Thus, t‐4‐(tert‐butyl)‐r‐1,2,2,c‐3‐tetramethylthietanium tetrafluoroborate or hexachloroantimonate ( 2a or 2b , resp.) were formed from thiiranium ion 1 . The thietanium salts 2a and 2b were characterized by X‐ray crystal‐structure analysis. Their cation geometry was also optimized by ab initio calculations at the RHF/6‐31G*//RHF/6‐31G* level, as were those of its stereoisomer 3 and of the unsubstituted S‐methylthietanium ion 5 . Comparison of 2 , 3 , and 5 with 4 – the only other thietanium ion studied by XRD, where the C‐atoms of the thioniacyclobutane ring are part of a trinorbornane skeleton – indicates that, in these systems, relief from substituent overcrowding is easily achieved by a folding of the four‐membered ring along the line connecting the two opposite C‐atoms. The corresponding ring‐deformation normal mode has a calculated frequency as low as 109 cm−1 in ion 5 , to be compared with a frequency of 138 cm−1 in methylcyclobutane. For thietanium ion 2 , the frequencies of the two normal modes involving such ring deformation have calculated values of 61 and 85 cm−1. 相似文献
74.
Beat Grolimund Emanuele Boselli Konrad Grob Renato Amad Giovanni Lercker 《Journal of separation science》1998,21(7):378-382
Solvent trapping reconcentrates volatile components after injection or on-line transfer of large volumes. When an early vapor exit is used, typically after a 5–10 m × 0.53 mm i.d. uncoated precolumn, the solvent trapping process differs from that described previously. The visual experiments and the conclusions drawn therefrom, as described in a previous paper, are supplemented with chromatographic results. They show that even hexane can be quantitatively analyzed in 250 μl of a pentane solution. Injection of a volume of 250 μl by vaporizer/precolumn solvent splitting was used in the analysis of gasoline in drinking water. Conditions for the transfer of a 1000 μl volume can easily be adjusted through detection of the front end of the flooded zone by a thermocouple mounted on the outer wall of the precolumn. 相似文献
75.
76.
Bin Yang Marina Lledos Riaz Akhtar Giuseppe Ciccone Long Jiang Emanuele Russo Sunil Rajput Chunyu Jin Maria Galini Faidra Angelereou Thomas Arnold Jonathan Rawle Massimo Vassalli Maria Marlow Dave J. Adams Mischa Zelzer 《Chemical science》2021,12(42):14260
Controlling supramolecular self-assembly across multiple length scales to prepare gels with localised properties is challenging. Most strategies concentrate on fabricating gels with heterogeneous components, where localised properties are generated by the stimuli-responsive component. Here, as an alternative approach, we use a spiropyran-modified surface that can be patterned with light. We show that light-induced differences in surface chemistry can direct the bulk assembly of a low molecular weight gelator, 2-NapAV, meaning that mechanical gel properties can be controlled by the surface on which the gel is grown. Using grazing incidence X-ray diffraction and grazing incidence small angle X-ray scattering, we demonstrate that the origin of the different gel properties relates to differences in the architectures of the gels. This provides a new method to prepare a single domain (i.e., chemically homogeneous) hydrogel with locally controlled (i.e., mechanically heterogeneous) properties.A mechanical pattern is created in a hydrogel film by pre-patterning the underlying surface chemistry. This allows spatial variation of the viscous component of the gel, controlling dissipative forces in the gel film without altering gel chemistry. 相似文献
77.
Emanuele Pugliese Claudio Castellano Matteo Marsili Luciano Pietronero 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(3):319-327
We introduce and study a model of an interacting population of agents who collaborate in groups which compete for limited
resources. Groups are formed by random matching agents and their worth is determined by the sum of the efforts deployed by
agents in group formation. Agents, on their side, have to share their effort between contributing to their group’s chances
to outcompete other groups and resource sharing among partners, when the group is successful. A simple implementation of this
strategic interaction gives rise to static and evolutionary properties with a very rich phenomenology. A robust emerging feature
is the separation of the population between agents who invest mainly in the success of their group and agents who concentrate
in getting the largest share of their group’s profits. 相似文献
78.
79.
The equilibrium free energy difference between two long-lived molecular species or "conformational states" of a protein (or any other molecule) can in principle be estimated by measuring the work needed to shuttle the system between them, independent of the irreversibility of the process. This is the meaning of the Jarzynski equality (JE), which we test in this paper by performing simulations that unfold a protein by pulling two atoms apart. Pulling is performed fast relative to the relaxation time of the molecule and is thus far from equilibrium. Choosing a simple protein model for which we can independently compute its equilibrium properties, we show that the free energy can be exactly and effectively estimated from nonequilibrium simulations. To do so, one must carefully and correctly determine the ensemble of states that are pulled, which is more important the farther from equilibrium one performs simulations; this highlights a potential problem in using the JE to extract the free energy from forced unfolding experiments. The results presented here also demonstrate that the free energy difference between the native and denatured states of a protein measured in solution is not always equal to the free energy profile that can be estimated from forced unfolding simulations (or experiments) using the JE. 相似文献
80.
Scifoni E Gianturco FA Grebenshchikov SY Schinke R 《The Journal of chemical physics》2006,125(16):164304
Ab initio quantum calculations have been carried out on the helium ionic trimer. The potential energy surface is accurately fitted, especially in the vicinity of the three equivalent minima. The spectrum of bound states for the zero angular momentum is computed and analyzed in detail. Energies and wave functions reveal several interesting features related to the fact that He3+ represents one of the few homonuclear ionic trimers that are linear in their ground vibrational state. At low energies, the triply degenerate eigenfunctions are localized at the potential minimum. With growing excitation energy, however, the wave functions exhibit stronger spatial delocalization. 相似文献