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23.
Krishanu Nandy Sayani Chaudhuri Ranjan Ganguly Ishwar K. Puri 《Journal of magnetism and magnetic materials》2008
Magnetic microspheres are used as mobile substrates in micro-total-analysis systems (μTAS), since the particles can be selectively functionalized to attach different bioconjugates and can be precisely manipulated using external magnetic field gradients. A large number of MEMS-based bio-analytical devices employ magnetophoretic separation as an important step during their operation. An analytical technique is proposed in this paper that describes the magnetophoretic transport of magnetic microspheres under an imposed magnetic field when there is a pressure-driven or electroosmotic flow through a microchannel. Successful magnetophoretic capture occurs if the strength of the field-inducing magnetic dipole exceeds a critical value, or if the particles are larger than a critical size. The magnetophoretic separator performance is characterized in terms of capture efficiency. The analysis shows that the capture efficiency is a function of two independent non-dimensional parameters, λ and γ that in turn involve all the physical design and operating parameters of the microfluidic separator, e.g., the dipole strength, particle size and susceptibility, fluid viscosity and velocity, channel height, and the separation of the dipole. Parametric plots of capture efficiency as function of λ and γ helps in choosing the right design and operation parameter of a practical microfluidic separator for a target level of performance. 相似文献
24.
Munish Puri Aneet Kaur Ram Sarup Singh Anubhav Singh 《Applied biochemistry and biotechnology》2010,162(1):181-191
Response surface methodology was used to optimize the fermentation medium for enhancing naringinase production by Staphylococcus xylosus. The first step of this process involved the individual adjustment and optimization of various medium components at shake
flask level. Sources of carbon (sucrose) and nitrogen (sodium nitrate), as well as an inducer (naringin) and pH levels were
all found to be the important factors significantly affecting naringinase production. In the second step, a 22 full factorial
central composite design was applied to determine the optimal levels of each of the significant variables. A second-order
polynomial was derived by multiple regression analysis on the experimental data. Using this methodology, the optimum values
for the critical components were obtained as follows: sucrose, 10.0%; sodium nitrate, 10.0%; pH 5.6; biomass concentration,
1.58%; and naringin, 0.50% (w/v), respectively. Under optimal conditions, the experimental naringinase production was 8.45 U/mL. The determination coefficients
(R
2) were 0.9908 and 0.9950 for naringinase activity and biomass production, respectively, indicating an adequate degree of reliability
in the model. 相似文献
25.
Munish Puri Shivani Gupta Parveen Pahuja Aneet Kaur J. R. Kanwar J. F. Kennedy 《Applied biochemistry and biotechnology》2010,160(1):98-108
β-D-galactosidase (EC 3.2.1.23) from Kluyveromyces marxianus YW-1, an isolate from whey, has been studied in terms of cell disruption to liberate the useful enzyme. The enzyme produced
in a bioreactor on a wheat bran medium has been successfully immobilized with a view to developing a commercially usable technology
for lactose hydrolysis in the food industry. Three chemical and three physical methods of cell disruption were tested and
a method of grinding with river sand was found to give highest enzyme activity (720 U). The enzyme was covalently immobilized
on gelatin. Immobilized enzyme had optimum pH and temperature of 7.0 and 40 °C, respectively and was found to give 49% hydrolysis
of lactose in milk after 4 h of incubation. The immobilized enzyme was used for eight hydrolysis batches without appreciable
loss in activity. The retention of high catalytic activity compared with the losses experienced with several previously reported
immobilized versions of the enzyme is significant. The method of immobilization is simple, effective, and can be used for
the immobilization of other enzymes. 相似文献
26.
S. PatilVijaya Puri 《Applied Surface Science》2011,258(4):1535-1540
The magnesium oxide thin films were prepared by thermal oxidation (in air) of vacuum evaporated magnesium thin film on alumina. It was found that oxidation temperature (623 K, 675 K and 723 K) and thickness (103 nm and 546 nm) dependent effects were prominently manifested in the surface morphology. Electrical and microwave properties (8-12 GHz) of the MgO thin films were also carried out. X-ray diffraction showed orientation along (2 0 0) and (2 2 0) directions. Flowerlike morphology was observed from SEM and flake like morphology for films of higher thickness oxidized at higher temperatures. The magnesium oxide thin film showed NTC behavior. Microwave transmittance was found to increase with increase in oxidation temperature but was lower than alumina. Frequency and oxidation temperature dependent microwave permittivity was obtained. The microwave dielectric constant varied in the range 8.3-15.3. 相似文献
27.
Summary A modified Wald statistic for testing simple hypothesis against fixed as well as local alternatives is proposed. The asymptotic
expansions of the distributions of the proposed statistic as well as the Wald and Rao statistics under both the null and alternative
hypotheses are obtained. The powers of these statistics are compared and its is shown that for special structures of parameters
some statistics have same power in the sence of order
. The results obtained are applied for testing the hypothesis about the covariance matrix of the multivariate normal distribution
and it is shown that none of the tests based on the above statistics is uniformly superior.
Research supported by the National Science Foundation Grant MCS 830149. 相似文献
28.
A. P. Singh W. R. Kalsi A. K. Tewari S. K. Puri B. Basu A. S. Sarpal 《Chromatographia》2001,54(7-8):537-540
Summary A procedure has been standarized for the determination of p-dioxan (1,4-dioxan) in benzene feedstock in the range of 1 to
100 ppm by capillary GC. The GC conditions such as oven temperature, length of the column etc were optimized to achieve better
resolution of p-dioxan from hydrocarbons. The standard addition method of quantitation, was used to determine the amount of
p-dioxan and was found to give better results than those obtained by external standardization. Prior to analysis the identity
of the p-dioxan peak was established by GC-MS. The proposed method has been applied for the monitoring of p-dioxan in high
purity benzene feedstock produced by the Udex extraction process in the refinery. The data were used for optimization of plant
conditions for the production of high purity benzene feedstock. By using this method, the p-dioxan content down to 0.5 ppm
can be determined in the benzene feedstock. 相似文献
29.
Frank N. Proske Madan L. Puri 《Proceedings of the American Mathematical Society》2002,130(5):1493-1501
In this paper we prove a central limit theorem for Borel measurable nonseparably valued random elements in the case of Banach space valued fuzzy random variables.
30.
Ching-Yuan Chiang Madan L. Puri 《Annals of the Institute of Statistical Mathematics》1984,36(1):35-50
Summary In the linear regression modelX
i=α+βci+Zi, we consider the problem of testing the subhypothesis that some (but not all) components of β are equal to 0. A class of
asymptotically distribution-free tests based on a quadratic form in aligned rank statistic is studied and the asymptotic relative
efficiencies of the proposed tests with respect to the general likelihood ratio test and the test based on least-squares estimates
of regression parameters are derived. Asymptotic optimality (à la Wald) is also discussed.
Work done under the National Science Foundation Grant MCS 8301409 and NATO Grant 1465. 相似文献