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191.
Solladié N Walther ME Gross M Duarte TM Bourgogne C Nierengarten JF 《Chemical communications (Cambridge, England)》2003,(19):2412-2413
In addition to the ammonium-crown ether recognition, pi-stacking interactions between the C60 sphere and the porphyrin moiety have been evidenced in a supramolecular complex obtained from a porphyrin-crown ether conjugate and a fullerene derivative bearing an ammonium unit. 相似文献
192.
193.
[reaction: see text] The directing ability of an aziridine group for the epoxidation of adjacent double bonds is demonstrated. The aziridine group is also used to effectively protect a double bond in a cycloenone system for a short synthesis of the title compound. 相似文献
194.
In this paper, we study orthogonal polynomials with respect to the bilinear form (f, g)
S
= V(f) A
V(g)
T
+ <u, f
(N)
g
(N)V(f) =(f(c
0), f "(c
0), ..., f
(n – 1)
0(c
0), ..., f(c
p
), f "(c
p
), ..., f
(n – 1)
p(c
p
))
u is a regular linear functional on the linear space P of real polynomials, c
0, c
1, ..., c
p
are distinct real numbers, n
0, n
1, ..., n
p
are positive integer numbers, N=n
0+n
1+...+n
p
, and A is a N × N real matrix with all its principal submatrices nonsingular. We establish relations with the theory of interpolation and approximation. 相似文献
195.
196.
M. Teresa Garay Leire Ruiz J. Ramón Marín J. Manuel Laza Matilde Rodriguez Luis M. León 《Colloid and polymer science》2010,288(16-17):1593-1599
Poly(N-tert-butylacrylamide) (PNtBAm) and poly(acrylic acid) (PAA) form interpolymer complexes in 1- and 2-propanol, blend in ethanol, whereas a segregative phase separation is observed when using methanol as solvent as shown by Fourier transform infrared (FTIR) spectrometry and elemental analysis studies. The composition of PNtBAm/PAA complexes has been determined. Thermal studies demonstrated that all complexes show unique glass transition temperatures, higher than those of the polymer components. Complexation of PAA with PNtBAm results in an improvement of its thermal stability. Solvent effects and specific interactions in the system PNtBAm/PAA have been studied by FTIR, revealing that differences in the polymer–solvent interactions are a decisive factor governing complex formation in solution. 相似文献
197.
Evenson William E. Lu Jun Winz Michele W. Gardner John A. Zacate Matthew O. Lee Teresa Mommer Niels 《Hyperfine Interactions》1999,120(1-8):427-431
In order to explain PAC data for tetragonal zirconia at temperatures between 900 and 1300oC, we have developed a four-state
stochastic model. The model simulates vacancies which trap and detrap at a PAC probe nucleus. While trapped, the vacancies
hop around the probe in equivalent sites. The four states in this Winkler–Gerdau stochastic theory are three trapped states
with equivalent electric field gradients (EFGs) of different orientations and a detrapped state with a weaker EFG whose axis
of symmetry is oriented along the diagonal between the three trapped EFGs. There are three hopping rates in this model: w,
the rate a trapped vacancy hops around the probe, wD, the detrapping rate, and wt, the trapping rate. We report results of calculations for values of these hopping rates implied by our tetragonal zirconia
data, and we report heuristic fitting functions which summarize the computer results and can be used to fit data efficiently
for a wide range of parameters.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
198.
199.
Alexander Alex Sophie Harvey Teresa Parsons Frank S. Pullen Patricia Wright Jo‐Anne Riley 《Rapid communications in mass spectrometry : RCM》2009,23(17):2619-2627
Prediction of tandem mass spectrometric (MS/MS) fragmentation for non‐peptidic molecules based on structure is of immense interest to the mass spectrometrist. If a reliable approach to MS/MS prediction could be achieved its impact within the pharmaceutical industry could be immense. Many publications have stressed that the fragmentation of a molecular ion or protonated molecule is a complex process that depends on many parameters, making prediction difficult. Commercial prediction software relies on a collection of general heuristic rules of fragmentation, which involve cleaving every bond in the structure to produce a list of ‘expected’ masses which can be compared with the experimental data. These approaches do not take into account the thermodynamic or molecular orbital effects that impact on the molecule at the point of protonation which could influence the potential sites of bond cleavage based on the structural motif. A series of compounds have been studied by examining the experimentally derived high‐resolution MS/MS data and comparing it with the in silico modelling of the neutral and protonated structures. The effect that protonation at specific sites can have on the bond lengths has also been determined. We have calculated the thermodynamically most stable protonated species and have observed how that information can help predict the cleavage site for that ion. The data have shown that this use of in silico techniques could be a possible way to predict MS/MS spectra. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献