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191.
Yue Zhu Min Pu De-Cai Fang Yong-Qiang Ji Jing He David G. Evans 《Structural chemistry》2010,21(4):817-825
Abstract
The cis–trans isomerization pathways of 3,3′-azobenzene disulphonate in the S0 and T1 states are studied by DFT method at the B3LYP/6-31G(d,p) level. In the S0 state, the cis–trans isomerization concerns the complex pathway that is characterized by the inversion of one NNC angle combined with rotation around the NC bond, and the three sequential transition states are also found on the potential energy profile. Therefore, the cis–trans isomerization of 3,3′-azobenzene disulphonate can be understood in terms of a pathway involving successive rotation, inversion, and rotation processes. The energy barrier of the S0 state is 22.79 kcal mol−1. In the T1 state, the isomerization mainly concerns the rotational pathway around the NN double bond, and the two isomers are connected through only one transition state. The isomerization of the T1 state is related to a lower energy barrier, 5.02 kcal mol−1, but requires a change in spin-multiplicity. 相似文献192.
The effects of the identity and position of basic residues on peptide dissociation were explored in the positive and negative modes. Low‐energy collision‐induced dissociation (CID) was performed on singly protonated and deprotonated heptapeptides of the type: XAAAAAA, AAAXAAA, AAAAAXA and AAAAAAX, where X is arginine (R), lysine (K) or histidine (H) residues and A is alanine. For [M + H]+, the CID spectra are dominated by cleavages adjacent to the basic residues and the majority of the product ions contain the basic residues. The order of a basic residue's influence on fragmentation of [M + H]+ is arginine > histidine ≈ lysine, which is also the order of decreasing gas‐phase basicity for these amino acids. These results are consistent with the side chains of basic residues being positive ion charge sites and with the more basic arginine residues having a higher retention (i.e. sequestering) of the positive charge. In contrast, for [M ? H]? the identity and position of basic residues has almost no effect on backbone fragmentation. This is consistent with basic residues not being negative mode charge sites. For these peptides, more complete series of backbone fragments, which are important in the sequencing of unknowns, can be found in the negative mode. Spectra at both polarities contain C‐terminal y‐ions, but yn″+ has two more hydrogens than the corresponding yn?. Another major difference is the production of the N‐terminal backbone series bn+ in the positive mode and cn? in the negative mode. Thus, comparison of positive and negative ion spectra with an emphasis on searching for pairs of ions that differ by 2 Da (yn″+ vs yn?) and by 15 Da (bn+ vs cn?) may be a useful method for determining whether a product ion is generated from the C‐terminal or the N‐terminal end of a peptide. In addition, a characteristic elimination of NH?C?NH from arginine residues is observed for deprotonated peptides. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
193.
Janko Drnovšek Igor Pušnik Jovan Bojkovski Gaber Begeš 《Accreditation and quality assurance》2010,15(2):125-131
The article describes the project of regional cooperation in proficiency testing within CARDS 2006 (assistance programme to
the Western Balkans), which was coordinated by European Committee for Standardization, European Commission and European Free
Trade Association and conducted by the University of Ljubljana, Faculty of Electrical Engineering, Laboratory of Metrology
and Quality. The later is the holder of the national standard for thermodynamic temperature as well as an accredited proficiency
testing provider and also accredited as a calibration, testing and inspection laboratory. It is also responsible for graduate
study programme Quality Engineering. Proficiency testing was considered as a core activity of the entire project, but additionally
as a very appropriate platform for knowledge transfer of EU technical legislation in selected sectors, metrology, testing
and quality assurance in general. The project had a high added value for participating laboratories in countries of Western
Balkans, because it required an active role of all participating laboratories, assured participation of staff from national
metrology institutions, all national accreditation bodies, and was supported by national quality infrastructures, such as
standardization, governmental institutions etc. in the entire Western Balkans region. The activities stimulated progress in
the area of conformity assessment, added knowledge to the implementation of technical directives and development of the technical
part of national legislation and therefore facilitated the process toward the accession to the European Union. The main objective
was therefore to organize proficiency testing in those sectors (construction, consumer protection and environment) that were
vital in the pre-accession process of countries seeking full implementation of EU technical legislation. 相似文献
194.
195.
Different non-exponential decays such as the concave and the convex double sloped decays in the coupled rooms provide distinct sound qualities. These are commonly considered to occur in the less reverberant sub-room and the more reverberant sub-room, respectively. However, numerical simulations and experiments in this paper show that the demarcation line is not located along the physical boundaries (e.g., the partition and the coupling aperture), but in the more reverberant sub-room. The sound field with the concave double sloped decay penetrates into the auxiliary sub-room to an extent which is influenced by the difference between the two natural reverberations of the sub-rooms. Furthermore the sound energy flows in different regions are investigated, demonstrating how energy feedback leads to the concave double sloped decay. 相似文献
196.
Dunlop MW Zhang QH Bogdanova YV Lockwood M Pu Z Hasegawa H Wang J Taylor MG Berchem J Lavraud B Eastwood J Volwerk M Shen C Shi JK Constantinescu D Frey H Fazakerley AN Sibeck D Escoubet P Wild JA Liu ZX 《Physical review letters》2011,107(2):025004
The extent of where magnetic reconnection (MR), the dominant process responsible for energy and plasma transport into the magnetosphere, operates across Earth's dayside magnetopause has previously been only indirectly shown by observations. We report the first direct evidence of X-line structure resulting from the operation of MR at each of two widely separated locations along the tilted, subsolar line of maximum current on Earth's magnetopause, confirming the operation of MR at two or more sites across the extended region where MR is expected to occur. The evidence results from in-situ observations of the associated ion and electron plasma distributions, present within each magnetic X-line structure, taken by two spacecraft passing through the active MR regions simultaneously. 相似文献
197.
Motivated by the prospect of realizing a Fermi gas with a synthetic non-Abelian gauge field, we investigate theoretically a strongly interacting Fermi gas in the presence of a Rashba spin-orbit coupling. As the twofold spin degeneracy is lifted by spin-orbit interaction, bound pairs with mixed singlet and triplet components emerge, leading to an anisotropic superfluid. We calculate the relevant physical quantities, such as the momentum distribution, the single-particle spectral function, and the spin structure factor, that characterize the system. 相似文献
198.
199.
200.
A cathode material of an electrically conducting carbon–LiFePO4 nanocomposite is synthesized by wet ball milling and spray drying of precursor powders prior to a solid-state reaction. The
structural characterization shows that the composite is composed of LiFePO4 crystals and 4.8 wt.% amorphous carbon. Galvanostatic charge/discharge measurements indicate that the composite exhibits
a superior high energy and high cycling stability. This composite delivers a discharge capacity of 159.1 mAh g−1 at 0.1 C, 150.8 mAh g−1 at 1 C, and 140.1 mAh g−1 at 2 C rate. The capacity retention of 99% is achieved after 200 cycles at 2 C. The 18,650 cylindrical batteries are assembled
using the composite as cathode materials and demonstrate the capacity of 1,400 mAh and the capacity retention of 97% after
100 cycles at 1 C. These results reveal that the as-prepared LiFePO4–carbon composite is one of the promising cathode materials for high-performance, advanced lithium-ion batteries directed
to the hybrid electric vehicle and pure electric vehicle markets. 相似文献