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31.
We have studied the clouding phenomena in promethazine hydrochloride (PMT) aqueous solutions in presence of electrolytes and non-electrolytes. PMT, a tranquillizer, shows phase separation. The cloud point (CP) decreases with increase in pH due to deprotonation of drug molecules. At constant pH, increasing salt addition causes an increase in CP, which is explained on the basis of their position in Hofmeister series and their hydrated radii. With quaternary salts CP increases due to adsorption/mixed micelle formation. Ureas decrease the CP and the behavior is explained on the basis of removal of water from the headgroup region. 相似文献
32.
Electromagnetic scattering from an infinite and a finite length PEMC circular cylinder, illuminated by an arbitrarily oriented
dipole, is investigated theoretically. An electric dipole as a source of excitation is considered first, and then a magnetic
dipole as a source of excitation is treated. In contrast to the case of an axially directed dipole, it is shown that no additional
terms are needed to incorporate the cross-polarized component of the field for the case of radial and circumferential dipoles.
Numerical verifications are presented to verify the validity of derived results and numerical code by comparing results with
the published literature.
相似文献
33.
Cloud point (CP) phenomenon occurring in amphiphilic drug chlorpromazine hydrochloride (CPZ) solutions with and without salts is reported herein. The CP of a 50mM CPZ solution (prepared in 10mM sodium phosphate, SP, buffer) was found to decrease with increasing pH, both in the absence as well as presence (50mM) of added salts (NaCl, NaBr, LiBr, KBr, tetra-n-butylammonium bromide). Whereas, at a fixed concentration of NaCl, the CP increased with increasing CPZ concentration, addition of increasing amounts of salts (NaF, NaCl, NaBr, LiCl, KCl) to 50mM CPZ solution (at pH 6.7) caused continuous increase in CP. On the basis of these studies the binding-effect orders of counterions and co-ions have been deduced, respectively, as: Br(-)>Cl(-)>F(-) and Li(+)>Na(+)>K(+). The similar trend of increasing CP with addition of increasing amounts of quaternary bromides (tetramethylammonium bromide, TMeAB; tetraethylammonium bromide, TEtAB; tetra-n-propylammonium bromide, TPrAB; tetra-n-butylammonium bromide, TBuAB; tetra-n-pentylammonium bromide, TPeAB) to 50mM CPZ solutions (at pH 6.7) was found to be dependent upon the alkyl chain length of the particular salt. The overall behaviour has been discussed in terms of electrostatic interactions, micellar growth, and mixed micelle formation. 相似文献
34.
Mohammad Kazim Naqvi 《Polymer Degradation and Stability》1985,13(2):161-166
Although the Frye and Horst1–3 theory of PVC stabilisation has been widely accepted, it has also been subject to some criticism. An alternative approach to the stabilisation of PVC, based on polar interactions within the PVC matrix, is postulated. Some of the results of research in this area which may be explained more convincingly on the basis of this approach are discussed in this paper. 相似文献
35.
Anam Iqbal Syed Ali Raza Naqvi Rashid Rasheed Asim Mansha Matloob Ahmad Ameer Fawad Zahoor 《Applied biochemistry and biotechnology》2018,185(1):127-139
Bacterial infection poses life-threatening challenge to humanity and stimulates to the researchers for developing better diagnostic and therapeutic agents complying with existing theranostic techniques. Nuclear medicine technique helps to visualize hard-to-diagnose deep-seated bacterial infections using radionuclide-labeled tracer agents. Metronidazole is an antiprotozoal antibiotic that serves as a preeminent anaerobic chemotherapeutic agent. The aim of this study was to develop technetium-99m-labeled metronidazole radiotracer for the detection of deep-seated bacterial infections. Radiosynthesis of 99mTc-metronidazole was carried by reacting reduced technetium-99m and metronidazole at neutral pH for 30 min. The stannous chloride dihydrate was used as the reducing agent. At optimum radiolabeling conditions, ~ 94% radiochemical was obtained. Quality control analysis was carried out with a chromatographic paper and instant thin-layer chromatographic analysis. The biodistribution study of radiochemical was performed using Escherichia coli bacterial infection-induced rat model. The scintigraphic study was performed using E. coli bacterial infection-induced rabbit model. The results showed promising accumulation at the site of infection and its rapid clearance from the body. The tracer showed target-to-non-target ratio 5.57 ± 0.04 at 1 h post-injection. The results showed that 99mTc-MNZ has promising potential to accumulate at E. coli bacterial infection that can be used for E. coli infection imaging. 相似文献
36.
A. A. Naqvi M. M. Nagadi O. S. B. Al-Amoudi 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(1):151-154
Non-destructive evaluation of concrete is an important task of quality control in building construction industry. The quality
evaluation of concrete samples was carried out using prompt gamma ray activation analysis (PGNAA) technique. In this study
calcium and silicon contents of six concrete samples were determined through yield of 1.94 MeV gamma-rays from calcium and
3.54 MeV gamma-rays from silicon. The concrete samples were prepared by mixing cement, coarse and fine aggregates in different
proportions. A linear correlation has been observed between the experimental yield of the prompt gamma rays and the actual
calcium and silicon concentration in the concrete samples. Results of this study have demonstrated successful use of an accelerator-based
PGNAA setup in non-destructive analysis of the concrete samples. 相似文献
37.
A critique of some recent publications (concerning the so-called inverted region in exchange-induced electronic energy transfer) is presented. It is first pointed out that the phenomena reported therein have in fact been known for nearly two decades; next, a derivation of the expression (used in the aforementioned communications) for k EnT, the transfer rate constant, is presented; finally, it is stressed that this formula cannot provide reliable quantitative predictions. 相似文献
38.
K. Razi Naqvi 《光谱学快报》2013,46(4):319-330
The triplet-triplet (T-T) spectra of twelve symmetrical cyanine dyes have been recorded, using flash photolysis in the presence of triplet state sensitizers. Three sets of dyes have been studied, each set comprising four members which differ from one another by the length of the bridge joining two identical nuclei (quinoline or benzthiazole); the internuclear linking is made by one =CH-, or by a chain composed of three, five, or seven such groups. Excluding the shortest member of each set, the remaining nine dyes are found to follow a common trend: the wavenumber of the 0-0 vibrational peak of the most intense T-T absorption band is linearly related to that of the 0-0 peak of the first singlet-singlet absorption band. 相似文献
39.
Mohamad SB Yousef YA Melø TB Jávorfi T Partali V Sliwka HR Razi Naqvi K 《Journal of photochemistry and photobiology. B, Biology》2006,84(2):135-140
Thione analogues of three naturally occurring carotenones (canthaxanthin, echinenone, and rhodoxanthin) were synthesized just over ten years ago, and it was reported that substitution of the oxygen atom by sulphur brings about a large red shift and some broadening in the optical absorption spectrum of the compound. Since the three carotenothiones are scarce, determination of their molar absorption coefficients presents a challenge. A method for relating the molar absorption coefficient of a carotenothione (Car-S) to that of its ketone analogue (Car-O) has been developed, which has revealed that the peak molar absorption coefficient of a Car-S is only about 60% of the corresponding value for Car-O. Using methylene blue as the sensitizer and acetonitrile as the solvent, we have also investigated the quenching (under photostationary conditions) of the 1270nm phosphorescence emission of singlet oxygen by each of the six carotenoids. The data conform to the Stern-Volmer relation, and show that substitution of a carbonyl oxygen atom by sulphur does not lead to an appreciable change in the value of the quenching constant, which is close to 1.5 x 10(10)M(-1)s(-1) for all six quenchers. 相似文献
40.
Jávorfi T Erostyák J Gál J Buzády A Menczel L Garab G Razi Naqvi K 《Journal of photochemistry and photobiology. B, Biology》2006,82(2):127-131
Absorption spectrophotometry, a standard tool for quantitative analysis, suffers from two major drawbacks: lack of sensitivity and vulnerability to scattering. It has been pointed out earlier that the solution to these problems lies in using a reflecting cavity as a sample holder. Due to multiple reflections at the cavity wall, the effective pathlength becomes considerably larger than the diameter of the cavity, and scattering losses are eliminated because scattered light is prevented from escaping the detector. Though much effort has been spent in analysing and improving the performance of such a device, often called an integrating cavity absorption meter (ICAM), a simple strategy for deducing the absorbance of the sample is still lacking. It is shown here that the absorbance A' measured by using an ICAM exhibits a sublinear increase with the solute concentration C. The physical reason for this departure from linearity is explained, and a straightforward procedure for converting A' to the true absorbance A (proportional to C) is established. The reliability of the procedure is demonstrated by comparing the ICAM absorption spectrum of dilute dye solutions with the spectra of more concentrated solutions recorded in a conventional spectrophotometer. The ability of the device to cope with scattering was tested by filling the ICAM with a suspension of chloroplasts, and the spectrum was found, as expected, to be free from scattering artefacts. 相似文献