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151.
152.
Konstantin Karaghiosoff Prof. Dr. Thomas M. Klapötke Prof. Dr. Carles Miró Sabaté Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(5):1164-1176
Methylation of 5-amino-1H-tetrazole ( 1 ) gives 1-methyl-5-amino-1H-tetrazole ( 2 ) and 2-methyl-5-amino-1H-tetrazole ( 3 ). A new family of energetic silver complexes based on ligands 1 , 2 and 3 with perchlorate and nitrate anions ( 10 – 15 ) were synthesized and characterized by using IR, Raman, and NMR (1H, 13C, 14N, and 35Cl NMR) spectroscopy, elemental analysis, and mass spectrometry. The crystal structures of the compounds were determined where possible and reveal interesting structural details that are discussed herein. Additionally, differential scanning calorimetry was used to assess the thermal stability of the new salts, which showed excellent thermal stabilities at temperatures up to and above 225 °C. Standard tests were also used to assess the sensitivity of the materials towards impact and friction. All the silver complexes showed increased sensitivity values in comparison with analogous protonated 5-amino-1H-tetrazolium perchlorate and nitrate salts. Some of these materials have sensitivity values that are comparable to commonly used primary explosives and all of them either deflagrate ( 12 – 14 ) or detonate loudly ( 10 and 11 ) on contact with an open flame. Lastly, nitrate salt 11 is easily initiated by thermal shock. It shows reasonably low sensitivity in comparison with other silver salts (e.g., silver azide or silver fulminate), which makes handling it much less hazardous. Compound 11 also has good thermal stability, decomposing at ≈300 °C, and shows interesting properties as a more environmentally benign alternative to lead(II) diazide in initiation devices for civil and military applications. 相似文献
153.
Chameleon sequences are amino acid sequences found in several distinct configurations in experiment. They challenge our understanding of the link between sequence and structure, and provide insight into structural competition in proteins. Here, we study the energy landscapes for three such sequences, and interrogate how pulling and twisting forces impact the available structural ensembles. Chameleon sequences do not necessarily exhibit multiple structural ensembles on a multifunnel energy landscape when we consider them in isolation. The application of even small forces leads to drastic changes in the energy landscapes. For pulling forces, we observe transitions from helical to extended structures in a very small span of forces. For twisting forces, the picture is much more complex, and highly dependent on the magnitude and handedness of the applied force as well as the reference angle for the twist. Depending on these parameters, more complex and more simplistic energy landscapes are observed alongside more and less diverse structural ensembles. The impact of even small forces is significant, confirming their likely role in folding events. In addition, small forces exerted by the remaining scaffold of a protein may be sufficient to lead to the adoption of a specific structural ensemble by a chameleon sequence. 相似文献
154.
Eitan Altman Konstantin Avrachenkov Merouane Debbah Daniel Sadoc Menasche 《Operations Research Letters》2008,36(2):160-164
We study non-cooperative constrained stochastic games in which each player controls its own Markov chain based on its own state and actions. Interactions between players occur through their costs and constraints which depend on the state and actions of all players. We provide an example from wireless communications. 相似文献
155.
156.
N-terminal tagging strategy for De Novo sequencing of short peptides by ESI-MS/MS and MALDI-MS/MS 总被引:1,自引:0,他引:1
Tatiana Yu. Samgina Sergey V. Kovalev Vladimir A. Gorshkov Konstantin A. Artemenko Nikita B. Poljakov Albert T. Lebedev 《Journal of the American Society for Mass Spectrometry》2010,21(1):104-111
The major portion of skin secretory peptidome of the European Tree frog Hyla arborea consists of short peptides from tryptophyllin family. It is known that b-ions of these peptides undergo head-to-tail cyclization, forming a ring that can open, resulting in several linear forms.
As a result, the spectrum contains multiple ion series, thus complicating de novo sequencing. This was observed in the Q-TOF spectrum of one of the tryptophyllins isolated from Hyla arborea; the sequence FLPFFP-NH2 was established by Edman degradation and counter-synthesis. Though no rearrangements were observed in FTICR-MS and MALDI-TOF/TOF
spectra, both of them were not suitable for mass-spectrometry sequencing due to the low sequence coverage. To obtain full
amino acid sequence by mass spectrometry, three chemical modifications to N-terminal amino moiety were applied. They include
acetylation and sulfobenzoylation of N-amino group and its transformation to 2,4,6-trimethylpyridinium by interaction with
2,4,6-trimethylpyrillium tetrafluoroborate. All three reagents block scrambling and provide spectra better than the intact
peptide. Unfortunately, all of them also readily react with lysine side chain. Hence, all investigated procedures can be used
to improve sequencing of short peptides, while acetylation is the recommended one. It shows excellent results, and it is plain
and simple to perform. This is the procedure of choice for MS-sequencing of short peptides by manual or automatic algorithms. 相似文献
157.
158.
Konstantin A. Borovkov David C.M. Dickson 《Insurance: Mathematics and Economics》2008,42(3):1104-1108
We derive a closed-form (infinite series) representation for the distribution of the ruin time for the Sparre Andersen model with exponentially distributed claims. This extends a recent result of Dickson et al. [Dickson, D.C.M., Hughes, B.D., Zhang, L., 2005. The density of the time to ruin for a Sparre Andersen process with Erlang arrivals and exponential claims. Scand. Actuar. J., 358–376] for such processes with Erlang inter-claim times. The derivation is based on transforming the original boundary crossing problem to an equivalent one on linear lower boundary crossing by a spectrally positive Lévy process. We illustrate our result in the cases of gamma, mixed exponential and inverse Gaussian inter-claim time distributions. 相似文献
159.
Konstantin Runovski Hans-Jürgen Schmeisser 《Journal of Fourier Analysis and Applications》2008,14(1):16-38
Means and families of operators generated by Bochner-Riesz kernels are studied. Some sharp results on their convergence are
achieved. The equivalence of the approximation errors of these methods to smoothness quantities related to the Laplacian is
proved.
相似文献
160.
Konstantin V. Tretiakov 《Journal of Non》2009,355(24-27):1435-1438
A two-dimensional system of hard, cyclic tetramers has been investigated by constant pressure Monte Carlo (MC) simulations with variable shape of the periodic box. The molecules (tetramers) are composed of four identical hard disks (atoms) with centers forming a square with sides equal to the diameter of the disks. The elastic constants and the Poisson’s ratio are determined by the analysis of strain fluctuations and the reference state of the system. The singular behavior of the elastic constants is in agreement with free volume theory. It has been found that the hard cyclic tetramer system is auxetic – that is, the Poisson’s ratio of the tetramer system is negative. 相似文献