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排序方式: 共有351条查询结果,搜索用时 156 毫秒
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2.
Muhammad Usman Khan Muhammad Yasir Mehboob Riaz Hussain Zainab Afzal Muhammad Khalid Muhammad Adnan 《International journal of quantum chemistry》2020,120(22):e26377
The development of organic electron acceptor materials is one of the key factors for realizing high-performance organic solar cells (OSCs). Nonfullerene electron acceptors, compared to traditional fullerene acceptor materials, have gained much impetus owing to their better optoelectronic tunabilities and lower cost, as well as higher stability. Therefore, 5 three-dimensional (3D) cross-shaped acceptor materials having a spirobifullerene core flanked with 2,1,3-benzothiadiazole are designed from a recently synthesized highly efficient acceptor molecule SF(BR) 4 and are investigated in detail with regard to their use as acceptor molecules in OSCs. The density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been performed for the estimation of frontier molecular orbital (FMO) analysis, density of states analysis, reorganization energies of electron and hole, dipole moment, open-circuit voltage, photo-physical characteristics, and transition density matrix analysis. In addition, the structure-property relationship is studied, and the influence of end-capped acceptor modifications on photovoltaic, photo-physical, and electronic properties of newly selected molecules ( H1-H5 ) is calculated and compared with reference ( R ) acceptor molecule SF(BR) 4 . The structural tailoring at terminals was found to effectively tune the FMO band gap, energy levels, absorption spectra, open-circuit voltage, reorganization energy, and binding energy value in selected molecules H1 to H5 . The 3D cross-shaped molecules H1 to H5 suppress the intermolecular aggregation in PTB7-Th blend, which leads to high efficiency of acceptor material H1 to H5 in OSCs. Consequently, better optoelectronic properties are achieved from designed molecules H1 to H5 . It is proposed that the conceptualized molecules are superior than highly efficient spirobifullerene core-based SF(BR) 4 acceptor molecules and, thus, are recommended to experiments for future developments of highly efficient solar cells. 相似文献
3.
Let R be a ring and d : R → R a derivation of R. In the present paper we investigate commutativity of R satisfying any one of the properties (i)d([x,y]) = [x,y], (ii)d(x o y) = xoy, (iii)d(x) o d(y) = 0, or (iv)d(x) o d(y) = x o y, for all x, y in some apropriate subset of R. 相似文献
4.
Imtiaz Ahmad M. Arsala Khan M. Shakirullah M. Ishaq Yousaf Iqbal Saeed ur Rehman 《中国化学会会志》2004,51(4):729-734
Influence of pretreatments, i.e., demineralization and pre‐soaking in some solvents on the yields of liquefied products obtained from hydro‐depolymerization of Pakistani coal in a pool of hydrogen has been discussed. Results of hydrogenation experiments demonstrated that demineralizing the coal sample prior to liquefaction caused the yields to decrease compared with the virgin coal samples. The contribution of mineral matter of coal has been evaluated by comparing the yields of liquid products of virgin and leached samples. Increase in the yields obtained from the hydrogenation experiments of swollen coal samples was not satisfactorily significant. 相似文献
5.
H.?Hussain H.?U.?Rehman Z.?AhmadEmail author 《Journal of Sol-Gel Science and Technology》2005,36(3):239-248
Nano-composites from aramid-silica system have been prepared via sol-gel process. Poly (phenyleneterephthalamide) copolymer
chains were prepared by reacting a mixture of p- and m-phenylenediamines with terephthaloyl chloride in dimethylacetamide used as solvent. The sol-gel process in the polymer
matrix was carried out through hydrolysis and condensation of a mixture of tetraethoxysilane and (3-glycidoxypropyl) trimethoxysilane.
The latter was used to develop linkage, on one hand with silica network structure using alkoxy groups and on the other hand
with aramid chains at its secondary amine groups through glycidal groups of silane. Mutual interaction between the two disparate
phases aramid and silica network was thus created. Thin films of the composites containing different proportions of silica
ranging from 5.0 to 25.0-wt% were cast by the solvent elution technique. The α-relaxation temperature associated with the
glass transition was measured by the dynamic mechanical thermal analysis. The results showed an increase in the glass transition
temperature from 328°C for the pure aramid to 352°C for the hybrid materials containing 25-wt% silica, an indicative of the
increased interfacial interaction between the two phases. Films having relatively low silica content were flexible and transparent,
but those with high silica content were opaque and brittle. These films were tested for their tensile strength, modulus and
toughness. The mechanical strength of the composites as compared to the pure aramid increased initially but with further addition
of silica the strength decreased. The initial increase can be explained due to increased interfacial interaction between the
two phases, however agglomeration of silica particles was responsible for decreasing strength at higher silica contents. 相似文献
6.
Darr JA Guo ZX Raman V Bououdina M Rehman IU 《Chemical communications (Cambridge, England)》2004,(6):696-697
For the first time, the MOCVD technique has been used to deposit carbonated hydroxyapatite onto Ti6AL4V substrates using volatile monomeric (liquid) complexes [Ca(beta-diketonate)(2)(L)] and P(OEt)(3). 相似文献
7.
Summary The paper describes tests for liquid chromatographs to assess the autosampler and pump flow rate precision; suitability of
the instrument for normal phase chromatography; UV detector performance; and external band broadening characteristics. Tests
for mixing and proportioning characteristics of solvent pumps and performance of diode array detectors are also considered.
These tests are designed to evaluate the performance of both newly released liquid chromatography equipment and equipment
already in operation. Data from evaluations carried out by instrument manufacturer’s and suppliers is reported and discussed.
This data offers specifications to a common format for initial selection of instruments prior to purchase. 相似文献
8.
Habib-ur- Rehman Akbar Ali Jamil Anwar Wasim Yawar 《Journal of Radioanalytical and Nuclear Chemistry》2006,267(2):421-425
Summary The synergistic mixture comprising picrolonic acid (HPA) and benzo-15-crown-5 (B15C5) in chloroform has been used for the
extraction of Ce(III), Eu(III) and Tm(III) as representatives of lanthanide(III) ions from pH 1-2 solutions having ionic strength
of 0.1 mol. dm-3(K+/H+, Cl-). The composition of the extracted species has been determined as M(PA)3. nB15C5 where M is Ce, Eu and Tm and n=1 or 2. The influence of various anions and cations on the extraction of these ions has also been studied and only oxalate,
cyanide and tartrate have some deleterious effect. The extraction equilibrium constants have been evaluated and discussed. 相似文献
9.
Saidbakhrom Saidjalolov Dr. Zainab Edoo Dr. Matthieu Fonvielle Louis Mayer Dr. Laura Iannazzo Dr. Michel Arthur Prof. Dr. Mélanie Etheve-Quelquejeu Dr. Emmanuelle Braud 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(10):3542-3551
The carbapenem class of β-lactams has been optimized against Gram-negative bacteria producing extended-spectrum β-lactamases by introducing substituents at position C2. Carbapenems are currently investigated for the treatment of tuberculosis as these drugs are potent covalent inhibitors of l,d -transpeptidases involved in mycobacterial cell wall assembly. The optimization of carbapenems for inactivation of these unusual targets is sought herein by exploiting the nucleophilicity of the C8 hydroxyl group to introduce chemical diversity. As β-lactams are structure analogs of peptidoglycan precursors, the substituents were chosen to increase similarity between the drug and the substrate. Fourteen peptido-carbapenems were efficiently synthesized. They were more effective than the reference drug, meropenem, owing to the positive impact of a phenethylthio substituent introduced at position C2 but the peptidomimetics added at position C8 did not further improve the activity. Thus, position C8 can be modified to modulate the pharmacokinetic properties of highly efficient carbapenems. 相似文献
10.
Khalid Mujasam Batoo Khalid Mehmood Ur Rehman 《Chinese Journal of Physics (Taipei)》2018,56(1):108-116
A series of Sm-CoMn substituted hexagonal ferrites with chemical composition of Sr0.85-xCa0.15SmxFe12-y(Co0.5Mn0.5)yO19 (0.00?≤?x?≤?0.60, (0.00?≤?y?≤?0.50) were synthesized by the solid-state reaction method. Microstructure and magnetic properties of the hexaferrites have been investigated by the X-ray diffraction, field emission scanning electron microscopy and a permanent magnetic measuring system. A single magnetoplumbite phase is exhibited in the hexaferrites with the substitutiom of Sm (0.00?≤?x?≤?0.12) and CoMn (0.00?≤?y?≤?0.10) contents. For the hexaferrites containing Sm (x?≥?0.24) and CoMn (y?≥?0.20), impurity phases are observed in the structure. The FESEM micrographs exhibit that the hexaferrites with different Sm-CoMn contents have formed hexagonal structures and the grain size of the hexaferrites remains unchanged with increasing Sm-CoMn content. The remanence (Br), Hk/Hcj ratios, and maximum energy product [(BH)max] decrease with increasing Sm-CoMn content (0.00?≤?x?≤?0.60, (0.00?≤?y?≤?0.50). Instrinsic coercivity (Hcj) and magnetic induction coercivity (Hcb) increase with increasing Sm-CoMn content (0.00?≤?x?≤?0.12, 0.00?≤?y?≤?0.10), and then decrease with increasing Sm-CoMn content (0.12?≤?x?≤?0.36, 0.10?≤?y?≤?0.30), while for the hexaferrites with Sm (x?≥?0.36) and CoMn (y?≥?0.30), with increasing Sm-CoMn content, Hcj increases and Hcb decreases. 相似文献