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排序方式: 共有440条查询结果,搜索用时 31 毫秒
71.
Xu YiTing Lin SuJuan Peng XiaoLiang Luo Wei-Ang Gal Jean-Yves Dai LiZong 《中国科学:化学(英文版)》2010,53(9):2006-2014
Science China Chemistry - In this study, platinum (Pt)-polyaniline(PANI)/MWNTs catalysts were synthesized by two sequential reactions. First, core-shell structural PANI/MWNTs composites were... 相似文献
72.
Chemin Jean-Yves 《偏微分方程通讯》2013,38(11-12):1771-1779
In this article, we shall study the inviscid limit of two dimensional fluids with bounded voticity. We prove that the solution of incompressible Navier-Stokes system converges strongly in L2 to the solution of the Euler incompressible system in the case of two-dimensional fluids in the whole space. 相似文献
73.
Max Schütz Christian Gemel Maximilian Muhr Christian Jandl Samia Kahlal Jean-Yves Saillard Roland A. Fischer 《Chemical science》2021,12(19):6588
Cluster growth reactions in the system [Cu5](Mes)5 + [Al4](Cp*)4 (Mes = mesitylene, Cp* = pentamethylcyclopentadiene) were explored and monitored by in situ LIFDI-MS and 1H-NMR. Feedback into experimental design allowed for an informed choice and precise adjustment of reaction conditions and led to isolation of the intermetallic cluster [Cu4Al4](Cp*)5(Mes) (1). Cluster 1 reacts with excess 3-hexyne to yield the triangular cluster [Cu2Al](Cp*)3 (2). The two embryonic [Cu4Al4](Cp*)5(Mes) and [Cu2Al](Cp*)3 clusters 1 and 2, respectively, were shown to be intermediates in the formation of an inseparable composite of the closely related clusters [Cu7Al6](Cp*)6 (3), [HCu7Al6](Cp*)6 (3H) and [Cu8Al6](Cp*)6 (4), which just differ by one Cu core atom. The radical nature of the open-shell superatomic [Cu7Al6](Cp*)6 cluster 3 is reflected in its reactivity towards addition of one Cu core atom leading to the closed shell superatom [Cu8Al6](Cp*)6 (4), and as well by its ability to undergo σ(C–H) and σ(Si–H) activation reactions of C6H5CH3 (toluene) and (TMS)3SiH (TMS = tris(trimethylsilyl)).Cu/Al cluster growth reactions leading to open- and closed-shell superatoms are investigated. Therein, LIFDI-MS is presented as a powerful technique for the in situ detection of cluster identities and reactivity patterns. 相似文献
74.
Lincker F Bourgun P Masson P Didier P Guidoni L Bigot JY Nicoud JF Donnio B Guillon D 《Organic letters》2005,7(8):1505-1508
[reaction: see text] The synthesis and photonic and liquid-crystalline properties of a novel oligo biphenylene vinylene (OBV) chromophore with an extended pi-electron system are reported; the compound exhibits high fluorescence, a large two-photon absorption cross-section, and two- and three-dimensional liquid-crystalline mesophases. 相似文献
75.
Perruchas S Tard C Le Goff XF Fargues A Garcia A Kahlal S Saillard JY Gacoin T Boilot JP 《Inorganic chemistry》2011,50(21):10682-10692
Three copper(I) iodide clusters coordinated by different phosphine ligands formulated [Cu(4)I(4)(PPh(3))(4)] (1), [Cu(4)I(4)(Pcpent(3))(4)] (2), and [Cu(4)I(4)(PPh(2)Pr)(4)] (3) (PPh(3) = triphenylphosphine, Pcpent(3) = tricyclopentylphosphine, and PPh(2)Pr = diphenylpropylphosphine) have been synthesized and characterized by (1)H and (31)P NMR, elemental analysis and single crystal X-ray diffraction analysis. They crystallize in different space groups, namely, monoclinic P21/c, cubic Pa ?3, and tetragonal I ?42m for 1, 2, and 3, respectively. The photoluminescence properties of clusters 1 and 3 show reversible luminescence thermochromism with two highly intense emission bands whose intensities are temperature dependent. In accordance to Density Functional Theory (DFT) calculations, these two emission bands have been attributed to two different transitions, a cluster centered (CC) one and a mixed XMCT/XLCT one. Cluster 2 does not exhibit luminescence variation in temperature because of the lack of the latter transition. The absorption spectra of the three clusters have been also rationalized by time dependent DFT (TDDFT) calculations. A simplified model is suggested to represent the luminescence thermochromism attributed to the two different excited states in thermal equilibrium. In contrast with the pyridine derivatives, similar excitation profiles and low activation energy for these phosphine-based clusters reflect high coupling of the two emissive states. The effect of the Cu-Cu interactions on the emission properties of these clusters is also discussed. Especially, cluster 3 with long Cu-Cu contacts exhibits a controlled thermochromic luminescence which is to our knowledge, unknown for this family of copper iodide clusters. These phosphine-based clusters appear particularly interesting for the synthesis of original emissive materials. 相似文献
76.
Lamsabhi AM Mó O Yáñez M Guillemin JC Haldys V Tortajada J Salpin JY 《Journal of mass spectrometry : JMS》2008,43(3):317-326
The gas-phase reactions between Ni(+) ((2)D(5/2)) and aminoacetonitrile, a molecule of prebiological interest as possible precursor of glycine, have been investigated by means of mass spectrometry techniques. The mass-analyzed ion kinetic energy (MIKE) spectrum reveals that the adduct ions [NC--CH(2)--NH(2), Ni(+)] spontaneously decompose by loosing HCN, H(2), and H(2)CNH, the loss of hydrogen cyanide being clearly dominant. The structures and bonding characteristics of the aminoacetonitrile-Ni(+) complexes as well as the different stationary points of the corresponding potential energy surface (PES) have been theoretically studied by density functional theory (DFT) calculations carried out at B3LYP/6-311G(d,p) level. A cyclic intermediate, in which Ni(+) is bisligated to the cyano and the amino group, plays an important role in the unimolecular reactivity of these ions, because it is the precursor for the observed losses of HCN and H(2)CNH. In all mechanisms associated with the loss of H(2), the metal acts as hydrogen carrier favoring the formation of the H(2) molecule. The estimated bond dissociation energy of aminoacetonitrile-Ni(+) complexes (291 kJ mol(-1)) is larger than those measured for other nitrogen bases such as pyridine or pyrimidine and only slightly smaller than that of adenine. 相似文献
77.
An Analysis of the Movement of Wetting and Nonwetting Fluids in Homogeneous Porous Media 总被引:2,自引:0,他引:2
The movement of wetting and nonwetting fluid flow in columns packed with glass beads is used to understand the more complicated flows in homogeneous porous media. The motion of two immiscible liquids (oil and water) is observed with different surfactants. Through dimensional analyses, fluid velocity is well correlated with interfacial tension and less dependent on particle size. In water–oil (W/O) experiments, finger pattern flows are observed if water is the displacing fluid that flows in an oil-filled porous media, whereas oil ganglia tend to form if oil is the displacing fluid in the water-wetted porous media. The results are well described by a simple model based on an earlier theory of flow in a tube. 相似文献
78.
Christelle Machon Lars Petter Jordheim Jean-Yves Puy Isabelle Lefebvre Charles Dumontet Jérôme Guitton 《Analytical and bioanalytical chemistry》2014,406(12):2925-2941
An analytical method coupling online solid-phase extraction (SPE) and liquid chromatography–tandem mass spectrometry (LC-MS/MS) was developed to quantify 16 endogenous nucleoside mono- and triphosphates in cellular samples. Separation was achieved on a porous graphitic carbon (PGC) column without ion-pairing agent in the mobile phase. Low levels of the ion-pairing agent diethylamine (DEA) added to the reconstitution solution were necessary to prevent peak tailing of nucleoside triphosphates. The mass spectrometer, a triple quadrupole with an electrospray ionisation source, was operated in positive mode. Two multiple reaction monitoring (MRM) segments were programmed, each an internal standard. Extraction and separation of nucleoside mono- and triphosphates were obtained within 20 min. The total duration of a single run was 37 min. Calibration curves, performed with labelled nucleotides added to the sample matrix, ranged from 0.29 to 18.8 pmol injected for deoxyribonucleotides and from 3.9 to 3,156 pmol for ribonucleotides. Accuracy did not deviate more than ?14.6 and 10.2 % from nominal values for all compounds at all levels. CV results were all lower than 17.0 % for the LLOQ level and 14.6 % for the other levels. Quality control (QC) samples were also in agreement with acceptance criteria, except for the lower QC of GMP. Ion suppression, matrix effect, extraction recoveries and stability were assessed. After validation, the method was applied to the evaluation of the effects of gemcitabine and hydroxyurea on nucleotide pools in Messa cells. 相似文献
79.