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21.
Paolo Domiano Amos Musatti Mario Nardelli Corrado Pelizzi Giovanni Predieri 《Transition Metal Chemistry》1979,4(6):351-354
Summary The x-ray crystal structure of the title complex is described Crystals are monoclinic, space groupP21/n, with unit-cell dimensions:a=18.070(2),b=13.471(2),c=6.788(2) Å,=94.70(1),Z=4. The structure was solved from diffractometer data by Patterson and Fourier methods and refined by least-squares techniques toR=5.0% for 2451 independent reflections. It consists of complex molecules, in which the copper atom square planar coordination comprises the chlorine atom, Cu-Cl=2.240(3) Å, and the organic ligand which acts as terdentate through the oxygen atom [Cu-O=1.948(3) Å] and a nitrogen atom, [Cu-N=1.933(5) Å] from the hydrazidic chain and the oxygen atom, [Cu-O = 1.894(4) Å] from the pyridoxal group. 相似文献
22.
[structure: see text] A second generation total synthesis of the potent antitumor agent (+)-phorboxazole A (1) has been achieved. The cornerstone of this approach comprises a more convergent strategy, involving late-stage Stille union of a fully elaborated C(1-28) macrocycle with a C(29-46) side chain. The second generation synthesis entails the longest linear sequence of 24 steps, with an overall yield of 4.2%. 相似文献
23.
Amos Korin Moshe Levy David Vofsi 《Journal of polymer science. Part A, Polymer chemistry》1980,18(1):109-121
Vinyl fluoride was polymerized by photochemical initiation in a continuous-flow cylindrical reactor at room temperature and at pressures of up to 30 atm. Copolymers with vinyl acetate were prepared in order to improve the solubility and processability of poly(vinyl fluoride) (PVF). The copolymers were hydrolyzed to the corresponding vinyl alcohol copolymers and yielded hydrophilic films that are strong and flexible only when swollen by water. It was found that on hydrolysis the Tg, Tm, and heat of fusion as well as degree of crystallinity increased. It was suggested that PVF and the copolymers with vinyl alcohol are isomorphous. 相似文献
24.
The approximation order provided by a directed set {S
h
}
h>0 of spaces, each spanned by thehZ
d
-translates of one function, is analyzed. The nearoptimal approximants of [R2] from eachs
h
to the exponential functions are used to establish upper bounds on the approximation order. These approximants are also used on the Fourier transform domain to yield approximations for other smooth functions, and thereby provide lower bounds on the approximation order. As a special case, the classical Strang-Fix conditions are extended to bounded summable generating functions.The second part of the paper consists of a detailed account of various applications of these general results to spline and radial function theory. Emphasis is given to the case when the scale {s
h
} is obtained froms
1 by means other than dilation. This includes the derivation of spectral approximation orders associated with smooth positive definite generating functions. 相似文献
25.
26.
A.T. Amos 《Molecular physics》2013,111(4):393-407
The theory of long waves originally developed by Born and Huang for ionic crystals and then adapted for molecular crystals with one molecule per unit cell by Hall is extended to include molecular crystals with two molecules per unit cell. A study is made of the non-analytic behaviour of the energy bands as the wave vector tends to zero and it is found that the energies of the optically excited levels will be different from the values usually assumed. The dispersion relation is obtained and used to discuss metallic reflectivity. The finite lifetime of the excited states can also be included in the theory and this has the effect of changing the position of maximum absorption as well as reducing the reflectivity. A comparison is made between the long wave theory, the simple form of Davydov theory and experiment. 相似文献
27.
28.
29.
Mark Farrell Bruno Melillo Amos B. Smith 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(1):240-243
The design, synthesis, and validation of new highly effective bifunctional linchpins for type II anion relay chemistry (ARC) has been achieved. The mechanistically novel negative‐charge migration that comprises the Brook rearrangement is now initiated by a stabilized tetrahedral intermediate, which is generated by nucleophilic addition to a Weinreb amide, rather than by a simple oxyanion that is generated from an epoxide. As a result, the linchpin preserves the carbonyl functionality in the ARC adducts, thus permitting access to functionally complex systems in a single flask without the need for further chemical manipulations. This tactic was validated with the one‐pot preparation of monoprotected 1,3‐diketones as well as pyran and spiroketal scaffolds, depending on the choice of nucleophile, electrophile, and work‐up conditions. 相似文献
30.
ABSTRACT Copolymers of 1,5-dioxepan-2-one (DXO) and e-caprolactone (?-CL), δ-valerolactone (δ-VL) or L-lactide (LLA) have been synthesized and characterized. High molecular weight copolymers were obtained using stannous-2-ethyl hexanoate as catalyst in bulk. Reactivity ratios for the copolymerization of DXO and δ-VL were determined at 110°C as rVL=0.5 and rDXO=2.3. At high conversion, depolymerization of δ-VL occurred, resulting in lower molecular weight and variations in the copolymer composition. Physical properties, such as crystallinity and melting temperature of the DXO-copolymers proved to be strongly dependent on the choice of comonomer and on the molar composition of the copolymers. DXO appears to be incorporated into the poly-?-caprolactone (PCL) crystals and to some extent into the poly-δ-valerolactone (PVL) crystals, resulting in a more gradual decrease in crystallinity with increasing amount of DXO. 相似文献