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排序方式: 共有1234条查询结果,搜索用时 31 毫秒
981.
Takashi Miyagawa Shinsuke Inuki Maho Honda Shinya Nakamura Isao Nakanishi Nobutaka Fujii Shinya Oishi Hiroaki Ohno 《Tetrahedron》2018,74(15):1802-1809
We recently reported a structure-activity relationship study of 4-epi-jaspine B derivatives toward sphingosine kinase (SphK) and identified selective inhibitors of two SphK isoforms. In this study, we designed and synthesized jaspine B regioisomers on the basis of palladium-catalyzed tetrahydrofuran formation and late-stage cross metathesis reactions to investigate the influence of the substitution position of functional groups on SphK inhibition. Evaluation of the jaspine B regioisomers SphK inhibitory activities revealed that several of these compounds exhibited comparable SphK1/2 inhibitory potency to that of 4-epi-jaspine B. 相似文献
982.
Tensile film stress of parylene deposited on liquid 总被引:1,自引:0,他引:1
Nguyen BK Matsumoto K Shimoyama I 《Langmuir : the ACS journal of surfaces and colloids》2010,26(24):18771-18775
We found that liquid droplets encapsulated by Parylene deposited directly on a liquid surface deformed toward spherical shapes during Parylene deposition. This deformation suggested that the film stress was tensile. We calculated the film stress of such Parylene films by studying the surface mean curvature of the droplet shape and found the film stress measured about 0.7-0.9 MPa tensile. This film stress is of opposite type to that of as-deposited Parylene films deposited on solid substrates, which was compressive. This difference might indicate a profound change of the Parylene polymer due to the use of liquid surface as deposition substrate. The tensile film stress and its effect on the droplet shape also have implications in the fabrication and operation of Parylene microdevices that have encapsulated liquid structures such as microlens or micropumps. 相似文献
983.
Osawa M Kawata I Igawa S Hoshino M Fukunaga T Hashizume D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(40):12114-12126
Tetrahedral gold(I) complexes containing the diphosphane ligand (dppb=1,2-bis(diphenylphosphino)benzene), [Au(dppb)(2)]X [X=Cl (1), Br (2), I (3), NO(3) (4), BF(4) (5), PF(6) (6), B(C(6)H(4)F-4)(4) (7)], and the ethanol and methanol adducts of complex 4, 8, and 9, were prepared to analyze their unique photophysical properties. These complexes are classified into two categories on the basis of their crystal structures. In Category I, the complexes (1-5) have relatively-small counter anions and two dppb ligands are symmetrically coordinated to the central Au(I) atom, and display an intense blue phosphorescence. Alternatively, the complexes (6-9) in Category II have large counter anions and two dppb ligands asymmetrically coordinated to Au(I) atom, and display a yellow or yellow orange phosphorescence. The difference in the phosphorescence color of the complexes between the Category I and II is ascribed to the change in the structure of the cationic moiety in the complex. According to DFT calculations, the symmetry reduction caused by the large counter anion of the complex in Category II gives the destabilization of HOMO (σ*) levels, leading to the red-shift of the emission peak. We have demonstrated that the symmetry reductions are responsible for the phosphorescence color alteration caused by external stimuli (volatile organic compounds and mechanical grinding). 相似文献
984.
Kitahara K Yoshihama I Hanada T Kokuba H Arai S 《Journal of chromatography. A》2010,1217(46):7249-7254
Monodispersed molecularly imprinted polymer particles selective for cholesterol were prepared by the copolymerization of styrene and divinylbenzene in the presence of template silica gel particles (particle size: 5 μm; pore size: 10 nm) functionalized with cholesterol on the surface, followed by dissolution of the cholesterol-bonded silica gel with a NaOH aqueous solution. Transmission and scanning electron micrographs of the molecularly imprinted polymer (MIP) particles revealed good monodispersity and porous structure. The MIP particles were packed into a high performance liquid chromatographic column, and its recognition ability of cholesterol was evaluated using cholesterol, cholesterol esters and fatty acid methyl esters by comparison with the non-imprinted polymer (NIP) particles prepared from styrene and divinylbenzene without cholesterol. The MIP particles showed a high affinity for cholesterol and cholesterol esters (K(MIP)'/K(NIP)' > 5.7). 相似文献
985.
The Ψ and Φ torsion angles around glycosidic bonds in a glycoside chain are the most important determinants of the conformation of a glycoside chain. We determined force‐field parameters for Ψ and Φ torsion angles around a glycosidic bond bridged by a sulfur atom, as well as a bond bridged by an oxygen atom as a preparation for the next study, i.e., molecular dynamics free energy calculations for protein‐sugar and protein‐inhibitor complexes. First, we extracted the Ψ or Φ torsion energy component from a quantum mechanics (QM) total energy by subtracting all the molecular mechanics (MM) force‐field components except for the Ψ or Φ torsion angle. The Ψ and Φ energy components extracted (hereafter called “the remaining energy components”) were calculated for simple sugar models and plotted as functions of the Ψ and Φ angles. The remaining energy component curves of Ψ and Φ were well represented by the torsion force‐field functions consisting of four and three cosine functions, respectively. To confirm the reliability of the force‐field parameters and to confirm its compatibility with other force‐fields, we calculated adiabatic potential curves as functions of Ψ and Φ for the model glycosides by adopting the Ψ and Φ force‐field parameters obtained and by energetically optimizing other degrees of freedom. The MM potential energy curves obtained for Ψ and Φ well represented the QM adiabatic curves and also these curves' differences with regard to the glycosidic oxygen and sulfur atoms. Our Ψ and Φ force‐fields of glycosidic oxygen gave MM potential energy curves that more closely represented the respective QM curves than did those of the recently developed GLYCAM force‐field. © 2009 Wiley Periodicals, Inc., J Comput Chem, 2009 相似文献
986.
Isao Kadota Yuji Yamagami Naoya Fujita Hiroyoshi Takamura 《Tetrahedron letters》2009,50(31):4552-4553
A useful method for the selective cleavage of primary MPM ethers by using TMSI/Et3N is described. Other protective groups such as secondary MPM ethers, silyl ethers, and benzylidene acetal were stable under the reaction conditions. 相似文献
987.
Attenuated total reflection (ATR)-based dynamic compression modulation two-dimensional (2D) correlation study of iso-phthalate based polyester (PES) films in the presence or absence of triphenyl phosphate (TPP) is carried out. In the PES without TPP, the dynamic response of side-chain (CO) groups is faster than that of the backbone (CCO) stretching, which is similar to the sequential result of our previous paper. With 15% TPP, the response of the backbone (CCO stretching) bands become faster than the side-chain (CO stretching) bands. In the case of 35% TPP, although slight differences are found, almost all of the observed peaks become synchronized with each other. The dynamic response feature is dramatically altered in the 45% TPP, suggesting that a transition point of larger molecular environment changes may exist between 35% and 45%. A model is proposed to explain these dynamic response features. 相似文献
988.
Jun Kobayashi Naoki Ohashi Hideyuki Sekiwa Isao Sakaguchi Miyuki Miyamoto Yoshiki Wada Yutaka Adachi Kenji Matsumoto Hajime Haneda 《Journal of Crystal Growth》2009,311(19):4408-4413
Bulk properties of gallium (Ga)- and aluminum (Al)-doped zinc oxide (ZnO) were studied using bulky single-crystalline thick films grown by liquid phase epitaxy (LPE). The highest possible dopant concentration was 1×1019 cm–3 for LPE growth at around 800 °C. The electron concentration was nearly same to the Ga and Al concentrations. The donor binding energy decreased to nearly zero with an increase in dopant concentration, and electron mobility of the sample with relatively high dopant concentration (1×1019 cm–3) was more than 60 cm2 V–1 s–1 at room temperature. The LPE technique is a potential solution for the production of ZnO for optical applications because the well-defined excitonic luminescence could be seen from the LPE-grown-doped single-crystals. 相似文献
989.
M. Markina A.N. Vasiliev N. Nakayama T. Mizota Y. Yeda 《Journal of magnetism and magnetic materials》2010,322(9-12):1249-1250
In a temperature range 5–300 K the specific heat C(T) on a new mixed valence cobalt oxides REBaCo4O7 (RE=Dy, Ho, Er, Tm, Yb, Lu) was investigated. The first-order structural phase transitions from hexagonal P63mc to orthorhombic Cmc21 phase was indicated by a peak-like anomaly in C(T) curves at TS~160, 178, 224, and 280 K for RE=Lu, Yb, Tm, and Er correspondingly. The magnetic phase transitions was indicated as the changes of slope on the C(T) curves were found at corresponding temperatures: TN~50, 74, 98, and 98 K for RE=Lu, Yb, Tm, and Er, correspondingly. 相似文献
990.