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101.
102.
103.
T. Sanders 《Journal d'Analyse Mathématique》2007,101(1):123-162
The paper has two main parts. To begin with, suppose that G is a compact abelian group. Chang’s Theorem can be viewed as a structural refinement of Bessel’s inequality for functions
ƒ ∈ L
2(G). We prove an analogous result for functions ƒ ∈ A(G), where A(G) is the space
endowed with the norm
, and generalize this to the approximate Fourier transform on Bohr sets.
As an application of the first part of the paper, we improve a recent result of Green and Konyagin. Suppose that p is a prime number and A ⊂ ℤ/pℤ has density bounded away from 0 and 1 by an absolute constant. Green and Konyagin have shown that ‖χ
A
‖
A(ℤ/pℤ) ≫ ɛ (log p)1/3−ɛ; we improve this to ‖χ
A
‖
A(ℤ/pℤ) ≫ ɛ (log p)1/2−ɛ. To put this in context, it is easy to see that if A is an arithmetic progression, then ‖χ
A
‖
A(ℤ/pℤ) ≪ log p. 相似文献
104.
Mao J Mukherjee S Zhang Y Cao R Sanders JM Song Y Zhang Y Meints GA Gao YG Mukkamala D Hudock MP Oldfield E 《Journal of the American Chemical Society》2006,128(45):14485-14497
Bisphosphonates are a class of molecules in widespread use in treating bone resorption diseases and are also of interest as immunomodulators and anti-infectives. They function by inhibiting the enzyme farnesyl diphosphate synthase (FPPS), but the details of how these molecules bind are not fully understood. Here, we report the results of a solid-state (13)C, (15)N, and (31)P magic-angle sample spinning (MAS) NMR and quantum chemical investigation of several bisphosphonates, both as pure compounds and when bound to FPPS, to provide information about side-chain and phosphonate backbone protonation states when bound to the enzyme. We then used computational docking methods (with the charges assigned by NMR) to predict how several bisphosphonates bind to FPPS. Finally, we used X-ray crystallography to determine the structures of two potent bisphosphonate inhibitors, finding good agreement with the computational results, opening up the possibility of using the combination of NMR, quantum chemistry and molecular docking to facilitate the design of other, novel prenytransferase inhibitors. 相似文献
105.
Microwave dielectric heating proved to be an efficient method for the one-pot and stepwise syntheses of symmetrical and unsymmetrical naphthalenediimide derivatives of alpha-amino acids. Acid-labile side chain protecting groups are stable under the reaction conditions; protection of the alpha-carboxylic group is not required. The stepwise condensation of different amino acids resulted in high yields of unsymmetrical naphthalenediimides. The reaction proceeds without racemization and is essentially quantitative. 相似文献
106.
Ko Sanders 《Communications in Mathematical Physics》2010,295(2):485-501
We prove that the singularity structure of all n-point distributions of a state of a generalised real free scalar field in curved spacetime can be estimated if the two-point
distribution is of Hadamard form. In particular this applies to the free field and the result has applications in perturbative
quantum field theory, showing that the class of all Hadamard states is the state space of interest. In our proof we assume
that the field is a generalised free field, i.e. that it satisfies scalar (c-number) commutation relations, but it need not
satisfy an equation of motion. The same arguments also work for anti-commutation relations and for vector-valued fields. To
indicate the strengths and limitations of our assumption we also prove the analogues of a theorem by Borchers and Zimmermann
on the self-adjointness of field operators and of a weak form of the Jost-Schroer theorem. The original proofs of these results
make use of analytic continuation arguments. In our case no analyticity is assumed, but to some extent the scalar commutation
relations can take its place. 相似文献
107.
GH. R. Kefayati 《Theoretical and Computational Fluid Dynamics》2013,27(6):865-883
In this paper, the effects of a magnetic field on natural convection flow in filled long enclosures with Cu/water nanofluid have been analyzed by lattice Boltzmann method. This study has been carried out for the pertinent parameters in the following ranges: the Rayleigh number of base fluid, Ra = 103–105, the volumetric fraction of nanoparticles between 0 and 6 %, the aspect ratio of the enclosure between A = 0.5 and 2. The Hartmann number has been varied from Ha = 0 to 90 with interval 30 while the magnetic field is considered at inclination angles of θ = 0°, 30°, 60° and 90°. Results show that the heat transfer decreases by the increment of Hartmann number for various Rayleigh numbers and the aspect ratios. Heat transfer decreases with the growth of the aspect ratio but this growth causes the effect of the nanoparticles to increase. The magnetic field augments the effect of the nanoparticles at high Rayleigh numbers (Ra = 105). The effect of the nanoparticles rises for high Hartmann numbers when the aspect ratio increases. The rise in the magnetic field inclination improves heat transfer at aspect ratio of A = 0.5. 相似文献
108.
Lisa Brase Tina Sanders Kirstin Dähnke 《Isotopes in environmental and health studies》2018,54(2):168-184
Anthropogenic nutrient inputs increase the N-load in many aquatic systems, leading to eutrophication and potential changes of biological N-retention capacity. In this study, nitrate inputs in a small river were investigated along a gradient of anthropogenic influence. We aimed to determine changes in nitrate load and isotope signatures in the water column and to identify the anthropogenic influence on biological nitrogen assimilation and nitrification or denitrification in sediments. In seasonal sampling campaigns, we analysed dissolved inorganic nitrogen concentrations, and stable isotopes of nitrate. To differentiate rates of nitrate production and consumption in the pristine vs. agricultural river section, intact sediment cores were incubated with 15N-labelled nitrate. δ15N values of nitrate in the pristine river section were low, reflecting natural sources, but, as expected, increased with nitrate concentration in all seasons along the gradient. In general, nitrate retention and consumption were higher in the anthropogenically impacted than in the pristine river section, and nitrate consumption exceeded production. In addition to our measurements, modelled results also show that even in a small river, the anthropogenically enhanced consumption capacity is overwhelmed by surplus N-inputs, and nitrate consumption cannot increase in turn with external loads. 相似文献
109.
Xu BJ Caprioli RM Sanders ME Jensen RA 《Journal of the American Society for Mass Spectrometry》2002,13(11):1292-1297
Laser capture microdissection (LCM) has become an important tool in biological research, permitting isolation of specific cell populations from frozen tissue samples containing a mixture of cell types. Cells obtained by LCM can be directly analyzed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). We report here methodology for the preparation and analysis of LCM captured cells with MALDI MS, giving high sensitivity and mass resolution. Comparison of the spectra obtained from cell populations of interest can identify unique disease or function-related protein markers. Using this approach, mass spectra obtained from human breast tissue containing invasive mammary carcinoma and normal breast epithelium using LCM were compared. Over 40 peaks were identified that significantly differed in intensity between invasive mammary carcinoma and normal breast epithelium. In addition, mass spectra are presented that show protein patterns from mouse liver and mouse colon crypts. The reported tissue preparation procedure and subsequent analysis by MALDI MS provide a new methodology for protein discovery involving LCM captured cells. 相似文献
110.