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51.
52.
A simulation study has been performed to quantify the effect of volume reduction on the thyroid absorbed dose per decay and to investigate the variation of energy deposition per decay due to β- and γ-activity of 131I with volume/mass of thyroid, for water, ICRP- and ICRU-soft tissue taken as thyroid material. A Monte Carlo model of the thyroid, in the Geant4 radiation transport simulation toolkit was constructed to compute the β- and γ-absorbed dose in the simulated thyroid phantom for various values of its volume. The effect of the size and shape of the thyroid on energy deposition per decay has also been studied by using spherical, ellipsoidal and cylindrical models for the thyroid and varying its volume in 1-25 cm3 range. The relative differences of Geant4 results for different models with each other and MCNP results lie well below 1.870%. The maximum relative difference among the Geant4 estimated results for water with ICRP and ICRU soft tissues is not more than 0.225%. S-values for ellipsoidal, spherical and cylindrical thyroid models were estimated and the relative difference with published results lies within 3.095%. The absorbed fraction values for beta particles show a good agreement with published values within 2.105% deviation. The Geant4 based simulation results of absorbed fractions for gammas again show a good agreement with the corresponding MCNP and EGS4 results (±6.667%) but have 29.032% higher values than that of MIRD calculated values. Consistent with previous studies, the reduction of the thyroid volume is found to have a substantial effect on the absorbed dose. Geant4 simulations confirm dose dependence on the volume/mass of thyroid in agreement with MCNP and EGS4 computed values but are substantially different from MIRD8 data. Therefore, inclusion of size/mass dependence is indicated for 131I radiotherapy of the thyroid. 相似文献
53.
M. Wasim A. Rahman J. H. Zaidi S. Waheed S. Ahmad 《Journal of Radioanalytical and Nuclear Chemistry》2002,254(1):219-222
The proposed reference material from the International Atomic Energy Agency, namely IAEA-407 (Fish Homogenate) was analyzed using instrumental neutron activation analysis (INAA). 15 elements, Al, As, Cl, Co, Cr, Fe, Hg, Mg, Mn, K, Na, Sb, Se, V and Zn, were determined using two irradiations (5 minutes and 5 hours) and four countings. IAEA-MA-A-1/TM (Copepoda Homogenate), NIST-SRM-1566 (Oyster Tissue), NIST-SRM-1572 (Citrus Leaves) and NIST-SRM-1577a (Bovine Liver) were utilized as standards in the quantification step. 相似文献
54.
Sabiha-Javied S. Waheed N. Siddique M. Tufail M. M. Chaudhry N. Irfan 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(1):17-24
The concentration of 32 elements was determined in phosphate rock samples from the Hazara phosphate deposits of Pakistan using
instrumental neutron activation analysis (INAA) technique employing different irradiation protocols. These included 23 major,
minor and trace elements (Al, As, Ba, Br, Co, Cr, Cs, Fe, Ga, Hf, K, Mn, Na, Rb, Sb, Sc, Sn, Ta, Th, U, V, Zn and Zr) and
9 rare earth elements (REEs) namely Ce, Eu, Ho, La, Lu, Nd, Sm, Tb and Yb. The results have been compared with the global
values of these elements. The concentrations for most of the elements studied are lower than the concentrations reported in
the literature whereas the concentrations of As, Co, Fe, K, Mn, Na and Sb are comparable. Two samples namely HR-4 and HR-5
have the highest concentrations for majority of the REFs with high enrichment factors. The quality assurance of data was performed
through the concurrent use of Lake Sediment (SL-1) and GSJ-JR-1 (Rhyolite) reference materials. The acquired data will serve
as a reference for the follow-up studies to assess the agronomic effectiveness of the Hazara phosphate rocks. 相似文献
55.
K. J. M. Abu Alnaja S. E. Waheed S. Abdel-Khalek 《Journal of Russian Laser Research》2016,37(3):219-226
We present a model of interaction between a four-level atom and the cavity field initially prepared in the coherent state in the presence of the phase damping effect. We discuss the atom–field entanglement and statistical properties under the damping effect in view of numerical calculations. We use the Mandel parameter as a quantifier of the statistical properties of the field; moreover, we study the different effects of the collective parameters in the master equation on the dynamical behavior of the field statistical properties and the entanglement measured by the negativity. Finally, we explore the link between the entanglement and statistical properties in view of the numerical results during the time evolution. 相似文献
56.
Usman Z Cao C Nabi G Kun DY Khan WS Mehmood T Hussain S 《The journal of physical chemistry. A》2011,115(24):6622-6628
The ab initio pseudopotential (PP) method within the generalized gradient approximation (GGA) has been used to investigate the electronic, elastic constants, and optical properties of zinc-blende GaN. An underestimated band gap along with higher DOS and squeezed energy bands around the fermi level is obtained. The d-band effect is briefly discussed for electronic band structure calculations. With the help of elastic constants, acoustic wave speeds are calculated in [100], [110], and [111] planes. The dielectric constant, refractive index, and its pressure coefficient are well illustrated. The effect of hydrostatic pressure is explicated for all these properties. The results of the present study are evaluated with the existing experimental and first-principle calculations. 相似文献
57.
Muhammad Mufakkar Anvarhusein A. Isab Tobias Rüffer Heinrich Lang Saeed Ahmad Najma Arshad Abdul Waheed 《Transition Metal Chemistry》2011,36(5):505-512
Copper(I) complexes of thioureas having the general formulae [CuLnBr] and [CuLn]Br [where, n = 1 − 4 and L = thiourea (Tu), N-methylthiourea (Metu), N-ethylthiourea (Ettu), N,N′-dipropylthiourea (Dprtu), N,N′-dibutylthiourea (Dbtu) or N,N′-diphenylthiourea (Dphtu)] were prepared and characterized by elemental analysis, IR, and NMR (1H and 13C) spectroscopy. The crystal structure of one of them, [Cu(Metu)4]Br (1), was determined by X-ray crystallography. The X-ray structure of 1 describes a tetrahedral geometry around copper(I) with all Metu ligands binding through sulfur atoms. An upfield shift in
the 13C NMR and downfield shift in the 1H NMR spectra are consistent with the thione coordination to copper(I). Antimicrobial activities of the complexes were evaluated
by the minimum inhibitory concentration method. The results showed that only [Cu(Ettu)3Br] was effective in inhibiting the growth of all the tested organisms (gram-positive, gram-negative bacteria, and Candida sp.), while the other complexes were not effective against all the organisms. 相似文献
58.
The International Atomic Energy Agency Marine Environmental Laboratory (IAEA-MEL) conducted an intercomparison exercise for
the “Trace elements and methyl mercury in fish scallop: IAEA-452” in 2009. The Neutron Activation Analysis (NAA) laboratory
at PINSTECH, Pakistan took part in this exercise. Comparison with the IAEA results showed that of the 18 elements reported
to the IAEA 7 had unacceptable z-scores while the data for two elements was questionable (2< |z-score| <3). Upon investigation it was discovered that the large number of elements having unacceptable z-scores was due to human error and the greater difficulty in analyzing biological samples which have low amounts of trace
elements. Therefore selection of values corresponding to matrix matched reference materials (RMs), such as IAEA-436 and IAEA-407,
and to non-interfering peaks the results obtained became comparable to the IAEA results with only the result for As having
|z-score|> 3. 相似文献
59.
A. A. Qureshi A. Sultan A. Rashid M. Ali A. Waheed S. Manzoor M. A. Baloch Matiullah S. Batool H. A. Khan 《Journal of Radioanalytical and Nuclear Chemistry》2012,293(3):955-963
Mount Arafat is a sacred place for Muslims. It has been classified as a granodiorite rock which mainly consists of feldspar and quartz, muscovite, etc. During the Hajj and Umra, Muslims visit this holly place and stay there for some time. In order to study the geology and thermal history as well as to assess the radiological hazards due to the presence of primordial radionuclides, systematic studies using petrographic, fission track dating and γ-spectrometric (HPGe) techniques were carried out. Our study yielded fission track age of 9.13 ± 1.05 Ma of the Mount Arafat granodiorite. Rifting, magmatism, volcanism and sea floor spreading that resulted in the formation of Red Sea seems may have altered the original age of the Arafat granodiorite under study to 9.13 ± 1.05 Ma. Measured radioactivity concentrations due to 226Ra, 232Th and 40K were found to be 10.75 ± 3.92, 29.21 ± 4.34 and 664.49 ± 7.45 Bq kg?1, respectively. From the measured radioactivity, gamma index (Iγ) and radium equivalent (Raeq) were calculated as 0.402 and 103.23 Bq kg?1 whereas outdoor external dose (Dout) and annual effective dose (Eout) were estimated to be 40.30 nGyh?1 and 0.045 mSvy?1 respectively. All the above mentioned values are well below the recommended limits. The Mount Arafat thus does not pose any radiological health hazard to the general public. 相似文献
60.