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71.
Professional vocalists encounter demands requiring voluntary control of phonation, while utilizing a considerable range of frequency and intensity. These quantifiable acoustic events can be measured and represented in a phonetogram. Previous research has compared the phonetograms of trained and untrained voices and found significant differences between these groups. This study was designed to assess the effects of vocal training for singers over a period of nine months. Phonetogram contour changes were examined, with the primary focus on expansion of frequency range and/or intensity control. Twenty-one first-year, master's level, vocal music students, who were engaged in an intensive vocal performance curriculum, participated in this study. Following nine months of vocal training, significant differences were revealed in the subjects' mean frequency range and minimum vocal intensity across frequency levels. There was no significant difference for the mean maximum vocal intensity across frequency levels following vocal training. 相似文献
72.
Barbara L. Osofsky 《代数通讯》2013,41(7):2071-2080
An = An(?) denotes the unique left distributive binary system on {0, 1,…,2n?1) that satisfies a ? 1 = a + 1 mod 2nfor all a ? An, and on(a) = k indicates the period 2kof a ? An (if b,c ? An, then a ? b = a ? c iff b ‵ c mod 2kand if 0 < b < c < 2kthen a < a ? b < a ? c). Amongs others, we prove that ot2(2t?2) ≤ t holds for every integer t ≥ 2, the equality taking place iff t is of the form 22? for an integer s ≥ 0. 相似文献
73.
74.
Barbara Nelli Ricardo Sa Earp Walcy Santos Eric Toubiana 《Annals of Global Analysis and Geometry》2008,33(4):307-321
We prove that a H-surface M in ${\mathbb{H}}^2 \times {\mathbb{R}} ,\vert H\vert \leq 1/2$ , inherits the symmetries of its boundary $\partial M,$ when $\partial M$ is either a horizontal curve with curvature greater than one or two parallel horizontal curves with curvature greater than one, whose distance is greater or equal to π. Furthermore we prove that the asymptotic boundary of a surface with mean curvature bounded away from zero consists of parts of straight lines, provided it is sufficiently regular. 相似文献
75.
Four commercially available formulations containing iron, zinc, and manganese were subjected to dissolution profile testing during 60 min and the dissolution was analyzed by ion chromatography. The obtained curves were analyzed directly by principal component analysis (PCA). The main trend (87.1% of variance) was connected with average dissolution percentage over the investigated time. The second component (11.2% of variance) is connected with shape of dissolution profile. All metals behave in the similar way and the differences were connected with excipients. An additional fit was completed on 12 kinetic models: first order kinetics (4 variants), Higuchi (2 variants), Hixson-Crowell (2 variants), Korsemeyer-Peppas, Logistic (2 variants), Peppas-Sahlin, Quadratic (2 variants), Weibull (3 variants), and Zero order kinetics (2 variants). The ranking of the fitting was performed by Akaike information criteria (AIC) values with additional PCA analysis on them, an approach presented in literature for the first time. The main trend (67.4% of variance) was connected with average fit. The second (14.8% of variance) is connected with differences of fitting ability to investigated dissolution curves. This methodology brought an overall look to trends and variances inside obtained data, both the profile shape and fitting ability to particular models. 相似文献
76.
[structures: see text] We studied the conformation of a series of primary amides in a solution of chloroform. Classical NMR tools such as dilution experiments, influence of DMSO, and 2D-NOESY, together with X-ray diffraction, were combined with an analysis of the difference of the chemical shift Deltadelta between the geminal amidic protons. This study was addressed in order to understand the conformation adopted by hydrazino acetamides 1a and 1b as model compounds for aza-beta3-peptides. In this manner, it was possible to show that the amidic group of these compounds acts as a H-bond donor and interacts with two different H-bond acceptors. We concluded that the hydrazinoturn, a specific bifurcated H-bond system observed in the solid state, is also the preferred conformation of hydrazino acetamides 1a and 1b in solution. Our results show that the short-range interaction with the N(alpha)-nitrogen lone pair not only stabilizes the C8 pseudocycle but could also contribute to the folding process of aza-beta3-peptides. In light of this, it could explain why aza-beta3-peptides develop a different H-bond network in comparison to their isosteric beta3-peptides analogues. Our work is in keeping with the recent interest of hydrazino peptides as an extension of the beta-peptide concept. 相似文献
77.
Barbara Marciniec M. Stawny Magdalena Hofman M. Naskrent 《Journal of Thermal Analysis and Calorimetry》2008,93(3):733-737
The study has been undertaken to check the effect of ionising radiation on the physical and chemical properties of florfenicol,
an antibiotic of a wide range of antibacterial activity. The solid-state samples were subjected to an electron beam generated
by accelerator corresponding to the doses of 25, 100 and 400 kGy, and the effect of the exposure was analysed by the methods
not requiring changes in the state (with no preliminary treatment), such as SEM, DSC, FTIR, XRD, EPR and HPLC.
Florfenicol irradiated with a dose of 25 kGy has not changed the form or colour, however, a small increase in intensity of
some absorption bands in the FTIR spectrum and of some peaks in the XRD pattern, a decrease in the melting point by 0.6°C,
the appearance of free radicals and a loss in the FF content within the error of the method (0.91%) have been observed. After
irradiation with greater doses (100 and 400 kGy) the changes have intensified, yellow discolouration appeared and the loss
of FF content has increased to 6.39%. As follows from the results, the compound studied in solid-state undergoes radiolysis
after e-beam irradiation in the doses ≥25 kGy, but lower doses (15–20 kGy) can be applied for its decontamination or sterilization
with no adverse effect on its physico-chemical properties. 相似文献
78.
David R. McMullin Mark W. Sumarah Barbara A. Blackwell J. David Miller 《Tetrahedron letters》2013,54(6):568-572
A strain of Chaetomium globosum (DAOM 240359) was isolated from an indoor air sample in Ottawa, Ontario, Canada. When fermented in liquid culture, this strain produced a number of known metabolites including chaetoglobosins A (6), C, and F (7), chaetomugilin D (5), chaetoviridin A (4), and three new nitrogenous azaphilones; 4′-epi-N-2-hydroxyethyl-azachaetoviridin A (1), N-2-butyric-azochaetoviridin E (2), and isochromophilone XIII (3). The structures were elucidated by spectroscopic analysis including; HRMS, 1D and 2D NMR, UV, and ORD. Compounds 2–7 were antimicrobial when tested using quantitative growth inhibition assays. 相似文献
79.
Attia MI Güclü D Hertlein B Julius J Witt-Enderby PA Zlotos DP 《Organic & biomolecular chemistry》2007,5(13):2129-2137
A structure for the self-condensation product of 2-(1H-indol-2-yl)ethyl tosylate 2a, previously proposed as 6,7,14,15-tetrahydro-15aH-azocino[1,2-a:6,5-b]diindole 3a, was revised based on the (13)C-2D-INADEQUATE experiment, and proved to be 7,7a,13,14-tetrahydro-6H-cyclobuta[b]pyrimido[1,2-a:3,4-a']diindole 4a. A mechanism for the unexpected formation of this novel hexacyclic heterocycle was proposed and its NMR solution structure was elucidated. Five derivatives of the title ring skeleton 12-16 designed as melatonin receptor ligands were synthesized and their affinities for the human MT(1) and MT(2) receptors were determined. Both butyramides 13 and 15, as well as the non-methoxy acetamide 12 exhibited micromolar binding affinities for both receptors being slightly MT(2) selective. The methoxy acetamide 14 showed the best pharmacological profile exhibiting a five times higher affinity for MT(1) (K(i) = 49 nM) than for MT(2) (K(i) = 246 nM) receptor. 相似文献
80.
Kerney Jebrell Glover Eranthie Weerapana Shin Numao Barbara Imperiali 《Chemistry & biology》2005,12(12):1311-1316
The gram-negative bacterium Campylobacter jejuni has a general N-linked glycosylation pathway encoded by the pgl gene cluster. One of the proteins in this cluster, PglB, is thought to be the oligosaccharyl transferase due to its significant homology to Stt3p, a subunit of the yeast oligosaccharyl transferase complex. PglB has been shown to be involved in catalyzing the transfer of an undecaprenyl-linked heptasaccharide to the asparagine side chain of proteins at the Asn-X-Ser/Thr motif. Using a synthetic disaccharide glycan donor (GalNAc-α1,3-bacillosamine-pyrophosphate-undecaprenyl) and a peptide acceptor substrate (KDFNVSKA), we can observe the oligosaccharyl transferase activity of PglB in vitro. Furthermore, the preparation of additional undecaprenyl-linked glycan variants reveals the ability of PglB to transfer a wide variety of saccharides. With the demonstration of PglB activity in vitro, fundamental questions surrounding the mechanism of N-linked glycosylation can now be addressed. 相似文献