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991.
《应用有机金属化学》2017,31(11)
A series of new cyclopentadienyl molybdenum compounds bearing substituted phenanthroline ligands [(η5‐C5H4CH2C6H4X‐4)Mo(CO)2(N,NL)][BF4] (X = F, Cl, Br; N,NL = phen, 5‐NH2‐phen, 4,7‐Ph2‐phen) was prepared and characterized using infrared and NMR spectroscopies. Crystal structures of [(η5‐C5H4CH2C6H4F‐4)Mo(CO)2(NCMe)2][BF4], [(η5‐C5H4CH2C6H4X‐4)Mo(CO)2(phen)][BF4] (X = F, Cl, Br) and [(η5‐C5H4CH2C6H4Cl‐4)Mo(CO)2(4,7‐Ph2‐phen)][BF4]⋅(4,7‐Ph2‐phen)⋅HBF4 were determined using X‐ray diffraction analysis. Biological studies revealed a strong cytotoxic effect of the chelating ligands. Although the cytostatic effect of the halogen in the side chain of the cyclopentadienyl ring is negligible, it could be used for future post‐modification of these types of cytotoxic active molybdenum‐based compounds. 相似文献
992.
离子选择性电极电位法测定钼矿石和钨矿石中氟 总被引:2,自引:0,他引:2
采用过氧化钠熔融钼矿石、钨矿石样品,乙二胺四乙酸钠和5-磺基水杨酸混合溶液浸取盐分,将样品溶液静置12h,吸取上层清液,以乙二胺四乙酸钠-硝酸钾组成的混合溶液作为总离子强度缓冲剂,控制溶液pH值为5.1,使用pF-1型氟离子选择电极,以饱和甘汞电极作参比电极测定溶液的平衡电位值。采用标准曲线法测定钼矿石和钨矿石中氟。钼矿石标准物质测定值的相对标准偏差(n=11)为3.36%,经4种国家一级钼矿石、钨矿石标准物质的分析验证,测定结果与标准值吻合。 相似文献
993.
El Moll H Nohra B Mialane P Marrot J Dupré N Riflade B Malacria M Thorimbert S Hasenknopf B Lacôte E Aparicio PA López X Poblet JM Dolbecq A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(50):14129-14138
The [ε-PMo(V)(8)Mo(VI)(4)O(36)(OH)(4){Ln(III)(H(2)O)}(4)](5+) (Ln=La, Ce, Nd, Sm) polyoxocations, called εLn(4), have been synthesized at room temperature as chloride salts soluble in water, MeOH, EtOH, and DMF. Rare-earth metals can be exchanged, and (31)P NMR spectroscopic studies have allowed a comparison of the affinity of the reduced {ε-PMo(12)} core, thus showing that the La(III) ions have the highest affinity and that rare earths heavier than Eu(III) do not react with the ε-Keggin polyoxometalate. DFT calculations provide a deeper insight into the geometries of the systems studied, thereby giving more accurate information on those compounds that suffer from disorder in crystalline form. It has also been confirmed by the hypothetical La→Gd substitution reaction energy that Ln ions beyond Eu cannot compete with La in coordinating the surface of the ε-Keggin molybdate. Two of these clusters (Ln=La, Ce) have been tested to evidence that such systems are representative of a new efficient Lewis acid catalyst family. This is the first time that the catalytic activity of polyoxocations has been evaluated. 相似文献
994.
Gougeon P Gall P Cuny J Gautier R Le Pollès L Delevoye L Trébosc J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(49):13806-13813
The new compounds LiLn(9)Mo(16)O(35) (Ln=La, Ce, Pr, and Nd) were synthesized from stoichiometric mixtures of Li(2)MoO(4), Ln(2)O(3), Pr(6)O(11) or CeO(2), MoO(3), and Mo heated at 1600 °C for 48 h in a molybdenum crucible sealed under a low argon pressure. The crystal structure, determined from a single crystal of the Nd member, showed that the main building block is the Mo(16)O(36) unit, the Mo(16) core of which is totally new and results from the fusion of two bioctahedral Mo(10) clusters. It can also be viewed as a fragment of an infinite twin chain of edge-sharing Mo(6) octahedra. The Mo(16)O(36) cluster units share some oxygen atoms to form infinite chains running parallel to the b axis, which are separated by the rare-earth and lithium cations. (7)Li-NMR experiments, carried out at high field on the nonmagnetic LiLa(9)Mo(16)O(35), provided insights into the local environment of the lithium ions. Magnetic susceptibility measurements confirmed the trivalent oxidation state of the magnetic rare-earth cations and indicated the absence of localized moments on the Mo(16) clusters. The electronic structure of the LiLn(9)Mo(16)O(35) compounds was analyzed using molecular and periodic quantum calculations. The study of the molecular orbital diagrams of isolated Mo(16)O(36) models allowed the understanding of this unique metallic architecture. Periodic density functional theory calculations demonstrated that few interactions occur between the Mo(16) clusters, and predicted semiconducting properties for LiLn(9)Mo(16)O(35) as a band gap of 0.57 eV was computed for the lanthanum phase. 相似文献
995.
Welsch S Lescop C Balazs G Réau R Scheer M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(33):9130-9141
The reaction of the [{CpMo(CO)(2)}(2)(μ,η(2):η(2)-P(2))] (Cp=cyclopentadienyl) metallo-ligand 2 with pre-organized Cu(I) bi- and trimetallic precursors afforded new coordination complexes with unprecedented coordination modes for a Mo(2)P(2) complex. Variable-temperature solution and solid-state (31)P NMR spectroscopy measurements were performed and X-ray diffraction studies revealed an η(2):η(1) coordination mode for the Mo(2)P(2) unit of 2 in the Cu(I) bimetallic complexes 3 and 4. DFT calculations were carried out to highlight the bonding situation of this unprecedented coordination mode in the Cu(I) bimetallic compound 3. It is built up from a side-on coordination of the P-P σ bond to one copper ion and from the interaction of the lone pair of one phosphorus atom with the second copper ion. The remaining available lone pair of the second phosphorus atom can be involved as well to interact with an additional metal centre, as evidenced in the Cu(I) trimetallic compound 5 in which an η(2):η(1):η(1) coordination mode of the ligand 2 is observed. Derivative 3 can be used as a molecular clip to obtain discrete π-stacked dimers through a ligand exchange reaction between acetonitrile ligands and cyano-capped π-conjugated systems, indicating the stability of the new η(2):η(1) coordination mode. 相似文献
996.
Fang W He Q Tan ZF Liu CY Lu X Murillo CA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(37):10288-10296
Binding two quadruply bonded dimolybdenum units [Mo2(DAniF)3]+ (DAniF=N,N′‐di‐p‐anisylformamidinate) with two chalcogen atoms generated two molecules with a central core composed of a cyclic six‐membered [Mo2]2(μ‐EH)2 species (E=S in 1 and O in 3 , and [Mo2] is a quadruple‐bonded [Mo2(formamidinate)3] unit). Aerobic oxidation of 1 and 3 followed by concomitant deprotonation gave rise to the corresponding [Mo2]2(μ‐E)2 compounds 2 and 4 . The latter show a striking coplanarity and near‐bond equalization of the Mo/E cluster. The oxidized species 2 and 4 are diamagnetic in the measured temperature range of 5 to 300 K, which is somewhat unexpected for molecules that have dimetal units with a σ2π4δ1 electronic configuration. This suggests there are strong interactions between the dimolybdenum units through the E atoms. The large electronic delocalization of the δ electrons over the entire Mo/E core is supported by the exceptionally large potential separation for the two successive one‐electron reductions of the linked Mo25+ units from the oxidized species (ΔE1/2=1.7 V for the sulfur analogue). This large electronic delocalization has an important effect on the NMR spectroscopic signals for the two sets of methine (N‐(CH)‐N) protons from the DAniF ligands. Those essentially parallel to the core, H∥, and those essentially perpendicular to the core, H⊥, exhibit downfield and upfield chemical shifts, respectively, that are separated by δ=1.32 ppm. The structural, electronic, magnetic, and chemical behaviors for 2 and 4 are consistent with aromaticity, with the [Mo2E2Mo2] cores that resemble the prototypical benzene molecule. Theoretical studies, including DFT calculations, natural bond orbital (NBO) analyses, and gauge‐independent atomic orbital (GIAO) NMR spectroscopic calculations, are also consistent with the aromaticity of the [Mo2]2(μ‐E)2 units being promoted by dδ(Mo2)–pπ(E) π conjugation. The cyclic π conjugation of the central moiety in 2 and 4 involves a total of six electrons with 2e from δ(Mo2) and 4e from pπ(E) orbitals, thereby conforming to Hückel’s rule when electrons in the MOs with δ character are considered part of the delocalized system. 相似文献
997.
998.
Single-step thermal carburization synthesis of Supported molybdenum carbides from molybdenum-containing methyl-silica 下载免费PDF全文
A novel synthesis route to obtain highly dispersed molybdenum carbides in porous silica is described. The synthesis was carried out by a single-step heat treatment of molybdenum-containing and methyl-modified silica (Mo-M-SiO2) in argon atmosphere at 973 K. Mo-M-SiO2 precursor was facilely obtained via a one-pot synthesis route, using (NH4)6Mo7O24 4H2O (AHM) as molybdenum sources and polymethylhydrosiloxane (PMHS) as silica sources at the initial synthetic step. The optimal C/Mo molar ratio in reaction system for complete carburization of molybdenum species was 7. The carburization process of molybdenum species followed a nontopotactic route involving a MoO2 intermediate phase, which was evidenced by XRD, N2 adsorption-desorption and in situ XPS. Formation mechanism of Mo-M-SiO2 precursor was also proposed by observation of the reaction between AHM and PMHS with TEM. Furthermore, by adding TEOS into silica sources and adjusting TEOS/PMHS mass ratio, crystal phase of molybdenum carbides transferred from β-Mo2C to α-MoC1-x, and SiO2 structure changed from microporous to micro/mesoporous. Catalytic performances of samples were tested using CO hydrogenation as a probe reaction. The supported molybdenum carbides exhibited high selectivity for higher alcohol synthesis compared with bulk β-Mo2C and α-MoC1-x. 相似文献
999.
《Journal of Energy Chemistry》2014,23(1):35-42
The effect of promoter cobalt and the sequences of adding cobalt and molybdenum precursors on the performance of sulfur-resistant methanation were investigated. All these samples were prepared by impregnation method and characterized by N2-adsorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and laser Raman spectroscopy (LRS). The conversions of CO for Mo-Co/Al, Co-Mo/Al and CoMo/Al catalysts were 59.7%, 54.3% and 53.9%, respectively. Among these catalysts, the Mo-Co/Al catalyst prepared stepwisely by impregnating Mo precursor firstly showed the best catalytic performance. Meanwhile, the conversions of CO were 48.9% for Mo/Al catalyst and 10.5% for Co/Al catalyst. The addition of cobalt species could improve the catalytic activity of Mo/Al catalyst. The N2-adsorption results showed that Co-Mo/Al catalyst had the smallest specific surface area among these catalysts. CoMoO4 species in CoMo/Al catalyst were detected with XRD, TPR and LRS. Moreover, crystal MoS2 which was reported to be less active than amorphous MoS2 was found in both Co-Mo/Al and CoMo/Al catalysts. Mo-Co/Al catalyst showed the best catalytic performance as it had an appropriate surface structure, i.e., no crystal MoS2 and very little CoMoO4 species. 相似文献
1000.
The electrical stability of molybdenum disulfide (MoS2) transistors is crucial for their use in various applications. However, it is tricky to evaluate the inherent stability of MoS2 transistors because it is highly dependent on environmental conditions during measurement such as humidity, light, and electrical factors. We studied the threshold voltage instability under negative bias stress at a variety of temperatures in a vacuum and in the dark to eliminate any environmental effects. In particular, the measurement of transfer curves under stress is minimized in order to study the inherent instability of MoS2 transistors, even though the measurement of transfer curves is normally indispensable to check for the evolution of electrical instability. MoS2 transistors have high average effective energy when compared to conventional amorphous Si and oxide semiconductor transistors, which allows for adequate operation at high temperatures. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献