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141.
142.
Takeo Taguchi Tomoyuki Takigawa Yumiko Tawara Tsutomu Morikawa Yoshiro Kobayashi 《Tetrahedron letters》1984,25(49):5689-5692
β-Fluoroallyl alcohols () were obtained with high stereoselectivity by the LiA1H4 reduction of 1-acetoxy-3-alkyl-2,2-difluorocyclopropanes (). 相似文献
143.
144.
Yoshiro Kakehashi 《Journal of magnetism and magnetic materials》1984,43(1):79-88
The magnetic properties of NiMn alloys at finite temperatures are investigated on the basis of an improved theory of the local environment effect (LEE). Magnetization vs. concentration curves, magnetization-temperature curves, phase diagram, high-field susceptibility and atomic short-range order dependence of the magnetization vs. temperature curves are calculated. The asymmetric behaviour of the high-field susceptibility around the critical concentration of ferromagnetism is explained by the LEE, as well as the itinerant character of the amplitude of the Ni local moment, for the first time. Two self-consistent solutions, corresponding to the high magnetization state and the low magnetization state, are found for a certain intermediate region of atomic order in Ni3Mn. Therefore, the existence of metamagnetism is suggested in that region. The anomalous double-stage magnetization-temperature curves in Ni3Mn alloys are explained by the transition from the high magnetization state to the low magnetization state. 相似文献
145.
Katsuhiko Ono Shoji Tanaka Yoshiro Yamashita 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1994,106(19):2030-2032
146.
This paper considers the set packing problem max{wx: Ax b, x 0 and integral}, whereA is anm × n 0–1 matrix,w is a 1 ×n weight vector of real numbers andb is anm × 1 vector of ones. In equality form, its linear programming relaxation is max{wx: (x, y) P(A)} whereP(A) = {(x, y):Ax +I
m
y =b, x0,y0}. Letx
1 be any feasible solution to the set packing problem that is not optimal and lety
1 =b – Ax
1; then (x
1,y
1) is an integral extreme point ofP(A). We show that there exists a sequence of simplex pivots from (x
1,y
1) to (x*,y*), wherex* is an optimal solution to the set packing problem andy* =b – Ax*, that satisfies the following properties. Each pivot column has positive reduced weight and each pivot element equals plus one. The number of pivots equals the number of components ofx* that are nonbasic in (x
1,y
1).This research was supported by NSF Grants ECS-8005360 and ECS-8307473 to Cornell University. 相似文献
147.
Naraso N Nishida J Ando S Yamaguchi J Itaka K Koinuma H Tada H Tokito S Yamashita Y 《Journal of the American Chemical Society》2005,127(29):10142-10143
Aromatic ring-condensed TTF derivatives exhibited excellent p-type FET performances in thin films. Introduction of fused benzene and pyrazine rings to the TTF skeleton was effective to enhance the intermolecular interactions and stability to oxygen. Ordered molecular alignment was confirmed by XRD studies. A pi-stacking structure was observed in the single crystal of diquinoxalinoTTF. 相似文献
148.
Yamaguchi S Muro S Kobayashi M Miyazawa M Hirai Y 《The Journal of organic chemistry》2003,68(16):6274-6278
The absolute structures of some naturally occurring chiral 2-isopropenyl-2,3-dihydrobenzofurans, (+)-remirol (1a), (+)-remiridiol (1b), (+)-angenomalin (2), and (+)-isoangenomalin (3), were studied by respective chiral synthesis. Kinetic resolutions of racemic 2-isopropenyl-2,3-dihydrobenzofurans, 2-isopropenyl-4,6-dimethoxy-2,3-dihydrobenzofuran (4), 4-hydroxy-2-isopropenyl-2,3-dihydrobenzofuran-5-carbaldehyde (8), and 2-isopropenyl-6-(MOM)oxy-2,3-dihydrobenzofuran-5-carbaldehyde (11c), by Sharpless dihydroxylation using (DHQ)(2)AQN or (DHQD)(2)AQN gave the corresponding chiral 2-isopropenyl-2,3-dihydrobenzofurans. Chiral (S)-(+)-4 (99% ee, using (DHQD)(2)AQN) was converted to natural remirol (S)-(+)-1a and then to natural remiridiol (S)-(+)-1b. (S)-(+)-8 (97% ee, using (DHQD)(2)AQN) was converted to natural angenomalin (S)-(+)-2. (R)-(-)-11c (>99% ee, using (DHQ)(2)AQN), was converted to natural isoangenomalin (R)-(+)-3. Thus, the absolute structures of natural remirol (+)-1a and remiridiol (+)-1b and angenomalin (+)-2 were determined to be S, and the structure of natural isoangenomalin (+)-3 was R. 相似文献
149.
Shrestha NK Kohn H Imamura M Irie K Ogihara H Saji T 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):17024-17027
The absorption spectra of copper phthalocyanine (CuPc) 1,2-dichloroethane (DCE) solutions containing trifluoroacetic acid (TFAA) shows that the number of protons coordinating to the CuPc molecule was 1 and 2 for the first and second proton adducts, respectively, which indicates the formations of CuPcH(+) and CuPcH(2)(2+). This CuPc molecule may act as a catalyst to dissociate TFAA into trifluoroacetate anion (A(-)) and H(+) and form the proton adducts. The electrical conductivity dependence of the solution on CuPc concentration also supports this mechanism. A dense film of CuPc was deposited on an indium tin oxide cathode plate by electrophoresis of the solution. Similar dense films of a wide variety of phthalocyanines (MPc; M = Cu, H(2), Fe, Ni, Zn, Pb, VO) were also deposited using this method. Similar films of CuPc were also formed using dichloromethane (DCM) and 1,1,1-trichloroethane (TCE) in place of DCE. Depositions are ascribed to the migration of positively charged monomers (i.e., protonated MPc). Scanning electron microscopy revealed that these films are composed of fibrous crystallites, size of which was found to increase with the electrophoresis time, the strength of the applied electrical field and the concentration of CuPc in the bath. The influence of the dielectric constant of the organic solvent on the film growth is discussed. 相似文献
150.
Yoshiro Ito Hajime Ohtani Shouji Ueda Yasuki Nakashima Shin Tsuge 《Journal of polymer science. Part A, Polymer chemistry》1994,32(2):383-388
The determination of end groups in polystyrenes (PSts) polymerized anionically with n-butyllithium as the initiator was carried out by pyrolysis-gas chromatography (Py-GC). The relative proportions of the end groups decrease with increasing molecular weight (MW). Consequently, the peaks which reflect the structure of the end groups can be distinguished by comparing pyrograms of samples with different MW. By comparing the intensities of these peaks relative to total intensities of all the peaks in the pyrogram, the numberaverage molecular weight (Mn) of the polymer can be estimated. The observed Mn values of PSts estimated by this method are compared with those determined by size exclusion chromatography (SEC). By this method it was possible to make direct determination of Mn values of PSts with MWs between 1000 and ca. 1 million. Furthermore, the calibration curve produced by the relative intensity of one of the most characteristic peaks (2-phenyl-1-heptene; C4H9? CH2C (Ph) = CH2) for the end group to total intensity of all the peaks in the pyrogram, gave rapid and highly reproducible Mn values. © 1994 John Wiley & Sons, Inc. 相似文献