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1.
2.
We develop two implementable algorithms, the first for the solution of finite and the second for the solution of semi-infinite min-max-min problems. A smoothing technique (together with discretization for the semi-infinite case) is used to construct a sequence of approximating finite min-max problems, which are solved with increasing precision. The smoothing and discretization approximations are initially coarse, but are made progressively finer as the number of iterations is increased. This reduces the potential ill-conditioning due to high smoothing precision parameter values and computational cost due to high levels of discretization. The behavior of the algorithms is illustrated with three semi-infinite numerical examples. 相似文献
3.
Vytautas Getautis Albina Stanisauskaite Tadas Malinauskas Jolanta Stumbraite Valentas Gaidelis Vygintas Jankauskas 《Monatshefte für Chemie / Chemical Monthly》2006,23(12):1401-1409
Hydrazones containing 1-phenyl-1,2,3,4-tetrahydroquinoline units were synthesized starting from diphenylamine. These compounds
were found to constitute novel hole transporting materials and were characterized by the time of flight method. The hole drift
mobility in these compounds exceeds 10−6 cm2 V−1 s−1 at an electric field of 106 V cm−1. 相似文献
4.
Summary. Phenoxyacetic acid distribution in two-phase systems n-aliphatic hydrocarbon (C5–C8) – water and its dimerization in organic phase were investigated. The values of distribution coefficient (D
HR), distribution constant (K
D), and dimerization constant (K
dim) of acid were obtained. The empirical correlations of these quantities with Hildebrand solubility parameter of organic solvents were established. The influence of pH of the aqueous phase as well as the polarity of the applied organic solvents on phenoxyacetic acid physical chemistry in
the two-phase systems was described. 相似文献
5.
A vinyl bis-sulfone Michael type approach towards heteroatom vinylation was applied on nitrogen derivatives. Cyclic thionocarbamates--mainly 1,3-oxazolidine-2-thiones--were converted into their N-vinyl counterparts; the procedure proved particularly efficient in the case of carbohydrate-derived complex structures. 相似文献
6.
The enantiomers of some amino acids have been separated on commercial chiral TLC plates in reversed-phase mode. The effect
of the pH* of the aqueous-organic mobile phase on the retention and mobility of the enantiomers and on selectivity was investigated.
It was shown that for most of the amino acids investigated the highest enantioselectivity was obtained at pH* 3–4 or 6–7.
The drift and disturbance of the baseline on the chromatograms were also much smaller at pH* 3–4 and 6–7. 相似文献
7.
Marion R. Surgi A. J. Polak R. C. Sundahl 《Journal of polymer science. Part A, Polymer chemistry》1989,27(8):2761-2776
Graph theory methods are shown to complement group additivity methods of predicting oxygen permeability in certain types of polymers. Graph theory is a topological approach that assigns a set of indices to a molecule to describe its structure. Since many physical properties of molecules depend upon their structure, graph theory indices can be used to describe important properties of molecules. In this work a set of graph theory indices are used to describe the property of a polymer based on a modified representation of the monomer unit. More specifically, Randic indices are used to describe the log of the oxygen permeability with 3.2% average relative error. Polymers comprising the basis set contain backbones of sp2, sp3, or aromatic carbons, oxygen, or silicon and have substituents that contain chloride, fluoride, alkyl groups, hydrogen, oxygen, aromatic carbons, or chloro and/or fluoro substituted alkyl groups. The correlation coefficient (R2) (0 ≤ R2 ≤ 1) of a nonlinear model is 0.91. The graph theory method for describing the oxygen permeability of these selected groups of polymers is in good agreement with that predicted by the permachor model. The permachor method makes oxygen permeability predictions based upon group additivity and distinguishes the degree of crystallinity of a polymer by empirically assigning different permachor (π) values to identical groups based upon the polymer crystallinity. The inability of graph theory to explain the remaining 9% of the scatter in the data is probably due to failure to incorporate into the graph theory model terms which quantify crystallinity. 相似文献
8.
Pulverized coal plasma gasification 总被引:11,自引:0,他引:11
R. A. Kalinenko A. P. Kuznetsov A. A. Levitsky V. E. Messerle Yu. A. Mirokhin L. S. Polak Z. B. Sakipov A. B. Ustimenko 《Plasma Chemistry and Plasma Processing》1993,13(1):141-167
A number of experiments on the plasma-vapor gasification of brown coals of three types have been carried out using an experimental plant with an electric-arc reactor of the combined type. On the basis of the material and heat balances, process parameters have been obtained: the degree of carbon gasification (c), the level of sulfur conversion into the gas phase (s), the synthesis gas concentration (CO+Hz) in the gaseous products, and the specific power consumption for the gasification process. The degree of gasification was 90.5-95.0%, the concentration of the synthesis gas amounted to 84.7–85.7%, and the level of sulfur conversion into the gas phase was 94.3–96.7%. Numerical study of the process of plasma gasification of coals was carried out using a mathematical model of motion, heating, and gasification of polydisperse coal particles in an electric-arc reactor of the combined type with an internal heat source (arc). The initial conditions for a conjugate system of nonlinear differential equations of the gas dynamics and kinetics of a pulverized coal stream interacting with the electric arc and oxidizer (water vapor) agree with the initial conditions of the experiments. The computation results satisfactorily correlate with the experimental data. The mathematical model can be used for the determination of reagent residence time and geometrical dimensions of the plasma reactor for the gasification of coals.Nomenclature
c
i
volume concentration of components (kmol m–3)
-
x
longitudinal coordinate (m)
-
f
i
source members, determined by variation of the ith component due to chemical reactions in unit volume in unit time (kmol m–3s–1)
-
velocity (m s–1)
-
M
s
ash mass in one particle (kg)
-
C
D
particle drag coefficient
-
3.14
-
r
s
particle radius (m)
-
d
particle diameter (m)
-
density (kg m–3)
-
C
p
heat capacity of components (J molt– K–1)
-
Q
j
thermal effect of reaction (J kmol–1)
- Ej
activation energy of reaction
-
N
l
volume concentration of particles of thelth fraction (m–3)
-
T
temperature (K)
-
emissivity factor of coal particles
-
5.67 × 10–8, blackbody emissivity coefficient (W m–2 K–4)
-
P
pressure (Pa)
-
S
reactor cross section (m2)
-
D
reactor diameter (m)
-
V
reactor volume (m3)
-
L
R
reactor length (m)
-
F
W
friction force on the wall (N)
-
f
g
friction coefficient
-
residence time (s)
- Nu
Nusselt number
- Re
Reynolds number
- Pr
Prandtl number
-
thermal conductivity of gas (J m– s–1 K–1)
-
R
8.3 × 103, universal gas constant (J kmol K–1)
- µ
i
molecular mass of component (kg kmol–1)
-
dynamic viscosity coefficient of gas (kg m–1 s–1)
-
thermal efficiency of plasma reactor
- qarc
specific heat flow from arc (W m–3)
-
P
1
heat supplied in vapor at T = 405 K (W)
-
P
2
heat loss to wall (W)
-
P
3
heat loss in the gas and slag separator chamber (W)
-
P
4
heat loss in the synthesis gas oxidation chamber (W)
-
P
5
heat loss in the slag catcher (W)
-
P
6
heat carried away in the off-gas (W)
- P
heat input of arc (W)
-
P
arc
electric power of arc (W)
- Qsp
specific power consumption (kw Hr kg–1)
-
d
w
specific heat flow to wall (W m–2)
-
c
degree of carbon gasification (%)
-
s
level of sulfur conversion into gas phase (%) 相似文献
9.
Jolanta Obniska Krzysztof Kaminski Agnieszka Dzierzawska-Majewska 《Journal of fluorine chemistry》2006,127(3):417-425
A series of N-phenyl- and N-benzyl-2-azaspiro[4.4]nonane- and [4.5]decane-1,3-diones containing a fluoro or trifluoromethyl substituents at the aryl ring was synthesized and tested for their anticonvulsant activity in the maximal electroshock (MES) and subcutaneous metrazole (sc.Met) tests. Among them, the most active were N-benzyl derivatives with fluoro and trifluoromethyl substituents especially at position-2 of the aryl moiety. The introduction of the phenyl ring at the imide nitrogen atom resulted in less active compounds. The results obtained showed that incorporation of fluoro or trifluoromethyl substituents increased the anticonvulsant activity in comparison to respective chloro, methoxy or methyl analogues. Crystallographically obtained conformation for one active and two inactive derivatives with trifluoromethyl substituents at position-2 or -3 of phenyl ring were initially used for molecular electrostatic potentials (MEP) calculation. The MEP distribution at carbonyl oxygen atoms was different for active and inactive molecules. 相似文献
10.