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921.
Marios A. Menelaou Frank R. Fronczek Martin A. Hjortso Anne F. Morrison Maryam Foroozesh Tina M. Thibodeaux 《光谱学快报》2013,46(10):1405-1413
In the course of our biosynthetic studies of constituents of hairy root cultures of Tagetes patula, we isolated four bithiophenes,[5-(3-buten-1-yny1)]-2,2′-bithiophenes(BBT),5-(4-acetoxy-1-butyny1)-2,2′-bithiophenes (BBTOAc),5-(4-hydroxy-1-butyny1)-2,2′bithiophenes (BBTOH) and 5-(3,4-diacetoxy-1-butyny1)-2,2′-bithiophenes [BBT(OAc)2]. In addition, stigmasterol, α-farnesene, three known benzofurans, of which only one was previouly isolated from T.patula, as well as a new benzofuran were obtained. The structures of the componds were determined by spectral analysis and comparison with published data. The molecular structure of the benzofuran isoeuparin was established by single crystal x-ray diffraction. 相似文献
922.
This paper introduces the use of nonlinear damping for extending the dynamic range of vibration energy harvesters. A cubic nonlinear damper is initially considered and the average harvested power and the throw are obtained for different sinusoidal base excitation amplitudes and frequencies, both numerically and analytically. It is demonstrated that when excited at resonance, at an amplitude below its maximum operational limit, the harvested power using a nonlinear damper can be significantly larger than that of a linear energy harvester, therefore expanding its dynamic range. A potential approach to implementing cubic nonlinearity using a shunted electromagnetic device is also presented. 相似文献
923.
Bibi Narjes Haerizade Mohammad Zaman Kassaee Hassan Zandi Maryam Koohi Ali A. Ahmadi 《Journal of Physical Organic Chemistry》2014,27(11):902-908
High‐level Density Functional Theory calculations, coupled with appropriate isodesmic reaction, are employed to investigate the effects of α‐carbon, ammonium, phosphorus, and sulfur ylides, cyclization, and unsaturation on the stability, multiplicity, and reactivity of novel singlet (S) and triplet (T) carbenes. Among them the highly π‐donating α‐ammonium ylide is found to exert the highest stabilizing effect on the carbenic center. α‐Ammonium ylides resist dimerization and hydrogenation. They show wider singlet–triplet energy gap (ΔΕS–T), broader band gap (ΔΕHOMO–LUMO), and higher nucleophilicity compared to the reported stable N‐heterocyclic carbenes. Aromatic cyclic unsaturated ammonium, phosphorus, and sulfur ylide carbenes appear more stable than their saturated cyclic analogs which are in turn more viable than their acyclic counterparts. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
924.
Mohammad Zaman Kassaee Maryam Koohi Reza Mohammadi Monireh Ghavami 《Journal of Physical Organic Chemistry》2013,26(11):908-916
Replacement of α‐methylenes with BH, AlH, CMe2, SiH2, NH, NMe, NtButyl, NPh, PH, O, and S in non‐planar cyclonona‐3,5,7‐trienylidene (CH2) alters its status from an unstable transition state to rather stable minima, at B3LYP/6‐311++G**//B3LYP/6‐31 + G* levels of theory. All species appear with singlet closed shell (Scs) global minima, except for SiH2 and CH2 which exhibit triplet electronic ground states. The order of stability based on singlet–triplet energy gap (ΔEs–t / kcalmol?1) is: CMe2 (45.8) > NH (35.8) > NMe (32.3) > O (31.5) > NtButyl (27.7) ≥ NPh (27.5) ≥ BH (27.4) > S (21.9) > PH (17.0) > CH2 (?4.4) > SiH2 (?12.5). In contrast to many reports on N‐heterocyclic carbenes, here alkyl groups appear to exert a higher stabilizing effect than heteroatoms, making CMe2 the most stable. In addition bulky NMe, NtButyl, and NPh appear more nucleophilic than their synthesized imidazol‐2‐ylidene congeners. Excluding SiH2, isodesmic reactions reveal that all substituents stabilize singlet state considerably more than the corresponding triplet. Finally, this work is hoped to pave the path for future matrix isolations and IR studies of these rather stable cyclic non‐planar carbenes. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
925.
Ali Morsali S. Ali Beyramabadi S. Hooman Vahidi Maryam Ghorbani 《Molecular physics》2013,111(8):483-490
The curves of experimental heat capacity against density show a minimum around and below the critical temperature (Tc), but at higher temperatures, this minimum is not observed. In this study, the role of attractive and repulsive forces on excess heat capacity of Lennard–Jones (LJ) dense fluids has been investigated using a molecular dynamics simulation technique. LJ potential is divided into attractive and repulsive parts. From the molecular dynamics calculations, potential energy and heat capacities have been obtained for Argon at temperatures of 100–500?K. The repulsive forces play the main role in causing the heat capacities at temperatures greater than critical point. Around and below the critical temperature, the role of repulsion is dominant at high densities, but attraction has the main role at low densities, consequently at middle densities, a minimum is formed. 相似文献
926.
We have applied density functional theory (DFT) calculations to study the structures, stabilities, electronic and magnetic properties of mono and multiply oxygenated Si60H60 fullerenes (Si60H60–2nOn, n = 1, 3, 6, 9, 10, 12, 18, 20, 21, 27 and 30). DFT results show that rearrangement between the closed [6,6] and [5,6] isomers of Si60H58O follows a two-step pathway involving an intermediate and two transition states. Preserving the C3 symmetry in the cage structure, extra epoxidation of Si60H60 has been accomplished. Based on our results, formation energies per oxygen atom for the multiple additions of oxygen atoms on Si60H60 cage are positive (endothermic character), and increase with the increasing of the number of oxygen atoms. In general, the oxygenation of Si60H60 cage leads to an increase in the electrophilicity of the Si60H60–2nOn oxides. The oxygenation of Si–Si bonds not only introduces a substantial broadening of the NMR pattern but also yield individual peaks, indicating different electrostatic environments of silicon nuclei in the Si60H60–2nOn oxides. 相似文献
927.
Maryam Jahangiri 《代数通讯》2013,41(12):5454-5463
928.
Let C be a semidualizing module for a commutative ring R. In this paper, we study the resulting modules of finite G C -projective dimension in Bass class, showing that they admit G C -projective precover. Over local ring, we prove that dim R (M) ≤ 𝒢? C ? id R (M) for any nonzero finitely generated R-module M, which generalizes a result due to Bass. 相似文献
929.
A new rarely reported ZnII mixed‐polypyridine coordination polymer with both rigid and flexible spacers, {[Zn(bpp)2(μ‐4,4′‐bipy)(H2O)2](ClO4)2 · H2O}n ( 1 ), has been synthesized and characterized by elemental analysis, IR‐, 1H NMR‐, 13C NMR spectroscopy and single‐crystal X‐ray diffraction. The thermal stability of compound 1 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The single‐crystal X‐ray structure of 1 shows that the complex has been formed from a 1D polymer as a result of bridging by the 4,4′‐bipy ligands. Solution and solid‐state luminescent spectra of the compound 1 indicate intense fluorescent emissions at ca. 353.6 and 468.8 nm, respectively. Removal of the interstitial water guest molecules results in a loss of crystallinity, but exposure to water vapor reestablishes the original structure, thus constituting 1 as a third‐generation porous framework. 相似文献
930.
Maryam Shojaei Abdolreza Mirmohseni Yadollah Omidi Maryam Farbodi 《Applied biochemistry and biotechnology》2009,159(1):54-64
Homovanillic acid (HVA) and vanillylmandelic acid (VMA) were selectively determined by quartz crystal nanobalance sensor in
conjunction with net analyte signal (NAS)-based method called HLA/GO. An orthogonal design was applied for the formation of
calibration and prediction sets including HVA, VMA, and some common and structurally similar urine compounds. The selection
of the optimal time range involved the calculation of the NAS regression plot in any considered time window for each test
sample. The searching of a region with maximum linearity of NAS regression plot (minimum error indicator) and minimum of predicted
error sum of squares value was carried out by applying a moving window strategy. Based on the obtained results, the differences
on the adsorption profiles in the time range between 1 and 300 s were used to determine mixtures of compounds by HLA/GO method.
Several figures of merit like selectivity, sensitivity, analytical sensitivity, and limit of detection were calculated for
both compounds. The results showed that the method was successfully applied for the determination of VMA and HVA. 相似文献