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991.
Tran L Choi SB Al-Najjar BO Yusuf M Wahab HA Le L 《Molecules (Basel, Switzerland)》2011,16(12):10227-10255
The M2 channel protein on the influenza A virus membrane has become the main target of the anti-flu drugs amantadine and rimantadine. The structure of the M2 channel proteins of the H3N2 (PDB code 2RLF) and 2009-H1N1 (Genbank accession number GQ385383) viruses may help researchers to solve the drug-resistant problem of these two adamantane-based drugs and develop more powerful new drugs against influenza A virus. In the present study, we searched for new M2 channel inhibitors through a combination of different computational methodologies, including virtual screening with docking and pharmacophore modeling. Virtual screening was performed to calculate the free energies of binding between receptor M2 channel proteins and 200 new designed ligands. After that, pharmacophore analysis was used to identify the important M2 protein-inhibitor interactions and common features of top binding compounds with M2 channel proteins. Finally, the two most potential compounds were determined as novel leads to inhibit M2 channel proteins in both H3N2 and 2009-H1N1 influenza A virus. 相似文献
992.
Sergei N. Chvalun Muhammad Ishaq John Blackwell Hans R. Kricheldorf 《Journal of Macromolecular Science: Physics》2013,52(1-2):93-106
Poly(p-phenylene phenylthio-terephthalate) (PPTT) forms nematic melts and is highly crystalline in the solid state, despite the probable random 2- and 3-dispo-sition of the S-phenyl substituents. The X-ray pattern of melt-spun fibers of PPTT contains 24 Bragg reflections that are indexed by a monoclinic unit cell with dimensions a = 28.6 Å, b = 4.81 Å, c = 12.57 Å (fiber axis), and γ= 101.6°. The cell contains monomer units of four chains that are arranged in pairs with the thiophenyl side chains interdigitated; successive pairs of chains are staggered by about c/2. We used molecular mechanics modeling to simulate arrays of chains with random 2- and 3-disposition of the side chains on the terephthalic acid units and compared the results with those for an idealized structure in which all the substituents were at the 2-position. The refined model for random substitution is more distorted, but the average separations of the monomer units are within the experimental errors of the observed unit cell dimensions, and their standard deviations are very similar to those derived from the line-broadening data. The potential energy of the model with random substitution is only about 1.9 kcal/mol of monomer higher than that for the model with all-2-substitution, indicating random substitution is not a major problem to the formation of an ordered structure. Compared to the structure formed by the analogous polyester, poly(p-phenylene phenylterephthalate) (PPT), the additional flexibility due to the thioether linkage between the backbone and phenyl side groups in PPTT allows better chain packing both within and between the layers of stacked chains. 相似文献
993.
Qiaofang Luo Ying Guan Yongjun Zhang Muhammad Siddiq 《Journal of polymer science. Part A, Polymer chemistry》2010,48(18):4120-4127
A series of lead‐sensitive poly(N‐isopropylacrylamide) microgels with pendant crown ether groups were prepared. Their cation‐sensitive behaviors were studied by dynamic light scattering. When ionic strength is not controlled, adding salts causes the microgel particles to deswell. However, when the salt effect is ruled out by keeping a constant ionic strength, adding Pb2+ results in much larger swelling. The Pb2+‐induced swelling was explained by the formation of host–guest complex between Pb2+ and the pendant crown ether groups, which increases the hydrophilicity of the polymer and accordingly the degree of swelling. The lead sensitivity of the microgels increases with increasing crown ether content. For the modified microgel with the highest crown ether content, it swells to ~430% of its original volume at [Pb2+] = 10 mM. Other cations also increase the swelling degree of the modified microgels. The extent of the cation‐induced swelling mainly depends on their affinity to the pendant crown ether groups. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4120–4127, 2010 相似文献
994.
Khasan Sanginovich Karimov Muhammad Tariq Saeed Chani Fazal Ahmad KhalidAdam Khan 《Physica E: Low-dimensional Systems and Nanostructures》2012,44(4):778-781
This paper presents the design, fabrication and experimental results of carbon nanotubes-cuprous oxide (CNTs-Cu2O) composite based strain sensors. The press-tablets were fabricated from the blend of CNTs (25 wt%) and Cu2O (75 wt%) at a pressure of 353 MPa. The diameter of multiwalled carbon nanotubes (MWCNTs) varied between 10 and 30 nm. The sizes of Cu2O micro-particles were in the range of 3-4 μm. The thickness of the press-tablets was 1 mm. The samples were installed on the polymer elastic beam by glue. The electric contacts to the samples were made by silver paste. The inter-electrodes distance (length) and diameter of the surface-type samples were in the range of 6-8 mm and 10 mm, respectively. The DC resistance of the strain sensors increases under tension and decreases under compression, while the average strain sensitivities are in the range of 44-46 and 24-28 for tension and compression, respectively. The simulation is in good agreement with the experimental results. 相似文献
995.
Munawar Ali Munawar Muhammad Azad Hamid Latif Siddiqui Faiz‐Ul‐Hassan Nasim 《中国化学会会志》2008,55(2):394-400
The quinolinylpyrimidine derivatives were prepared by the condensation of quinolinyl chalcones with urea (or thiourea) under basic conditions by using both conventional and microwave heating. Their IR, 1H NMR, 13C NMR, mass spectra and CHN analyses confirmed the prepared compounds. The newly prepared quinolinylpyrimidine derivatives were screened for antimicrobial activities against the bacterial strains viz. S. aureus, Shigella, Salmonela, P. aeroginosa, B. Subtilus and E. coli and found considerably active against S. aureus, P. aeroginosa and E. coli. 相似文献
996.
Siti Nuurul Fatimah Hasim Muhammad Azmi Abdul Hamid Roslinda Shamsudin Azman Jalar 《Journal of Physics and Chemistry of Solids》2009,70(12):1501-1504
ZnO thin films have been successfully synthesized by thermal evaporation of pure zinc at 900 °C under the flow of different percentages of argon and oxygen gases. The films were characterized by X-ray diffraction (XRD), variable pressure scanning electron microscopy (VPSEM), energy dispersive X-ray spectroscopy (EDS) and UV–vis spectroscopy. The aim of this paper is to study the influence of the oxygen percentage on the structural and morphological properties of the ZnO films. VPSEM results show that very thick needle structures were produced at high oxygen percentages. EDS results revealed that only Zn and O are present in the sample, indicating a composition of pure ZnO. XRD results showed that the ZnO synthesized under different quantities of oxygen were crystalline with the hexagonal wurtzite structure. UV–vis spectroscopy results indicated that the optical band gap energies from the transmission spectrum are between 3.62 and 3.69 eV for ZnO thin films. 相似文献
997.
D. D. Anderson Muhammad Zafrullah 《Proceedings of the American Mathematical Society》2003,131(12):3689-3692
We show that a weakly Krull domain satisfies : for every pair there is an such that is -invertible. For Noetherian, satisfies if and only if every grade-one prime ideal of is of height one. We also show that a modification of can be used to characterize Noetherian domains that are one-dimensional.
998.
Muhammad WT Tabb DL Fox KF Fox A 《Rapid communications in mass spectrometry : RCM》2003,17(24):2755-2762
A computer-based method is described for automated detection of peaks in product ion spectra that allows discrimination of structurally related polymerase chain reaction (PCR) products. PCR products of K-ras mutants having single nucleotide substitutions and isomeric sequence changes in positions 1 and 2 of codon 12 (e.g. TGT and GTT) were used as a model system. SpecDiff, a tool for differentiating pairs of mass spectra by identifying peaks that either differ in relative intensity between spectra or only appear in one of a pair of spectra, was created to help automate detection. This program was demonstrated to have great utility in detection of mutations and could also be useful as a general tool for differentiating other molecules of closely related structure. 相似文献
999.
Thomas Heinze Tim F. Liebert Katy S. Pfeiffer Muhammad A. Hussain 《Cellulose (London, England)》2003,10(3):283-296
This paper summarizes selected results obtained during a two-year research project in the framework of the focus program Cellulose and cellulose derivatives (SPP 1011), sponsored by the German Science Foundation (DFG). New synthesis paths for the preparation of the most important cellulose ester, cellulose acetate, were investigated. In contrast to conventional methods, cellulose was converted in a homogeneous phase reaction with acetyl chloride in the presence of different bases, including polyvinyl pyridine and cross-linked polyvinyl pyridine. Moreover, results of the conversion in the new solvent dimethyl sulfoxide/tetrabutylammonium fluoride trihydrate are discussed. The structures obtained were analyzed both on the level of the anhydroglucose unit (AGU) and along the polymer chain. It was found that the addition of a base can significantly change the selectivity of the reaction and thereby the properties of the products (e.g., solubility). No signs of a non-statistical distribution of the acetyl groups along the polymer chains were observed. Furthermore, reactivity and selectivity of the acylation reactions, using in situ activation with p-toluenesulfonyl chloride (Tos-Cl), were studied for different long-chain carboxylic acids (capric-, caprylic-, decanoic-, lauric-, palmitic-, stearic acid). The thermogravimetric analysis of these derivatives showed that the decomposition temperature increased with an increasing number of carbon atoms, starting from 292 °C (cellulose caprate) to 318 °C (cellulose stearate). New cellulose derivatives were synthesized, for example, cellulose adamantoyl ester. For this purpose cellulose was converted homogeneously in N,N-dimethylacetamide/LiCl with free acids in the presence of activating reagents, for example, Tos-Cl or 1,1-carbonyldiimidazol. 相似文献
1000.
An atomistic model of layered double hydroxides, an important class of nanoporous materials, is presented. These materials have wide applications, ranging from adsorbents for gases and liquid ions to nanoporous membranes and catalysts. They consist of two types of metallic cations that are accommodated by a close-packed configuration of OH- and other anions in a positively charged brucitelike layer. Water and various anions are distributed in the interlayer space for charge compensation. A modified form of the consistent-valence force field, together with energy minimization and molecular dynamics simulations, is utilized for developing an atomistic model of the materials. To test the accuracy of the model, we compare the vibrational frequencies, x-ray diffraction patterns, and the basal spacing of the material, computed using the atomistic model, with our experimental data over a wide range of temperature. Good agreement is found between the computed and measured quantities. 相似文献