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31.
Anna Rakowska Robert Filipek Krzysztof Sikorski Marek Danielewski Renata Bachorczyk 《Mikrochimica acta》2004,145(1-4):183-186
The interdiffusion process in thin and thick (500nm–60µm) Au–Ni layers deposited on different substrates is studied using the EDS technique. In-depth X-ray analysis based on the Pouchou and Pichoir method is applied for obtaining the concentration profiles in nanometre scale multi-layers. A theoretical analysis using the Darken method is employed for modelling interdiffusion in the Au–Ni system. Computer simulations, where intrinsic diffusivities of the Au and Ni are functions of composition, are presented and compared with experimental results. 相似文献
32.
Jose′ L. F. C. Lima Antoacutenio O. S. S. Rangel M. Renata S. Souto 《Fresenius' Journal of Analytical Chemistry》1997,358(5):657-662
A flow injection system was developed for the sequential determination of total nitrogen and phosphorus in digests of vegetables
using potentiometric and spectrophotometric detection systems, respectively. A tubular ammonium selective electrode with a
sensor system composed of nonactin/monactin in tris(2-ethylhexyl) phosphate was used. The selectivity limitations of this
electrode were overcome by the inclusion of a gas-diffusion unit in the system that separated ammonium from the rest of the
sample matrix and allowed the determination of total nitrogen and phosphorus by the partition of the sample plug between two
streams.
The results obtained with the developed FIA system were in good agreement with those of the reference methods. Sampling rates
from 40 to 60 samples per hour and relative standard deviations below 3.5% were achieved.
Received: 17 October 1996/Revised: 21 November 1996/Accepted: 27 November 1996 相似文献
33.
Flow injection system with gas diffusion for the sequential determination of total nitrogen and phosphorus in vegetables 总被引:1,自引:0,他引:1
Jose´ L. F. C. Lima Antoacutenio O. S. S. Rangel M. Renata S. Souto 《Analytical and bioanalytical chemistry》1997,358(5):657-662
A flow injection system was developed for the sequential determination of total nitrogen and phosphorus in digests of vegetables
using potentiometric and spectrophotometric detection systems, respectively. A tubular ammonium selective electrode with a
sensor system composed of nonactin/monactin in tris(2-ethylhexyl) phosphate was used. The selectivity limitations of this
electrode were overcome by the inclusion of a gas-diffusion unit in the system that separated ammonium from the rest of the
sample matrix and allowed the determination of total nitrogen and phosphorus by the partition of the sample plug between two
streams.
The results obtained with the developed FIA system were in good agreement with those of the reference methods. Sampling rates
from 40 to 60 samples per hour and relative standard deviations below 3.5% were achieved.
Received: 17 October 1996/Revised: 21 November 1996/Accepted: 27 November 1996 相似文献
34.
This review presents a survey of the condensations of 3-formylchromone with various active methylene and methyl compounds, e.g. malonic or barbituric acid derivatives, five-membered heterocycles, etc. The utilisation of the condensation products for the synthesis of different heterocyclic systems, which is based on the ability of the gamma-pyrone ring to be opened by the nucleophilic attack is also reviewed. Finally, the applications of microwave irradiation as an unconventional method of reaction activation in the synthesis of condensation products is described and the biological activity of some chromone derivatives is noted. 相似文献
35.
36.
Angela Somavilla Higioka Renata Cristina Messores Rudolf-Oliveira Flavia Martinello Maria Luiza Bazzo 《Accreditation and quality assurance》2016,21(2):143-149
Point-of-care (POC) testing of glucose (glucometers) represents a convenient alternative to monitor glycemia since the measurement procedure is performed without delay after sampling of the capillary blood, thereby avoiding the metabolism by the blood cells of glucose present in plasma. Likely because of sample instability, there is no proficiency test provider in Brazil for this type of POC sample. In this context, this study aimed to evaluate the analytical performance of glucometers used in a tertiary care hospital. The glucometers used were the Accu-Chek Performa® model from Roche Diagnostics, which use the principle of amperometry. The reference method was the reaction with modified hexokinase/glucose-6-phosphate in a Dimension® device. The stability evaluation of the control samples showed that it can be performed up to 90 min after the collection of whole blood samples. In the two rounds performed, only one result of the 17 glucometers evaluated was out of the threshold of two standard deviation. Thus, this method for control of glucometers met the expectations and enabled comparing the glucometers in a hospital. Given the current quality guidelines, daily internal quality control of glucometers is recommended, besides at least two annual comparisons between the results of the glucometers and the reference method and one EQA every 3 months. 相似文献
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39.
Małgorzata T. Kaczmarek Renata Jastrząb Wanda Radecka-Paryzek 《Journal of solution chemistry》2013,42(1):18-26
Formation of complexes between the lanthanide ions and N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine ligand was studied in solution by pH potentiometry. The potentiometric titration was performed at 25.00 °C in 0.1 mol·dm?3 NaClO4 ionic strength and in DMSO:water (30:70 v:v) solvent mixture. N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine ligand (H2L) occurs in three forms: fully or partially deprotonated and unionized. Computer analysis of potentiometric data indicated that in solution the lanthanide (Ln) complexes exist as LnL2, Ln(HL)2 and Ln(H2L)2 species. This observation appears to be in contrast to the solid-state behavior of these complexes prepared in a self-assembly process and structurally defined. Stability constants for La3+, Eu3+, Gd3+, Tb3+, Ho3+ and Lu3+ (Ln3+) complexes were determined. The order of stabilities of LnL2 species in terms of metal ions is La3+ > Eu3+ ≈ Gd3+ = Tb3+ < Ho3+ < Lu3+ with a prominent “gadolinium break”. 相似文献
40.
Dr. Renata Kaczmarek Samuel Ward Dipra Debnath Taisiya Jacobs Alexander D. Stark Dariusz Korczyński Prof. Dr. Anil Kumar Prof. Dr. Michael D. Sevilla Dr. Sergey A. Denisov Dr. Viacheslav Shcherbakov Dr. Pascal Pernot Prof. Dr. Mehran Mostafavi Prof. Dr. Roman Dembinski Prof. Dr. Amitava Adhikary 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(43):9495-9505
The directionality of the hole-transfer processes between DNA backbone and base was investigated by using phosphorodithioate [P(S−)=S] components. ESR spectroscopy in homogeneous frozen aqueous solutions and pulse radiolysis in aqueous solution at ambient temperature confirmed initial formation of G.+-P(S−)=S. The ionization potential of G-P(S−)=S was calculated to be slightly lower than that of guanine in 5′-dGMP. Subsequent thermally activated hole transfer from G.+ to P(S−)=S led to dithiyl radical (P-2S.) formation on the μs timescale. In parallel, ESR spectroscopy, pulse radiolysis, and density functional theory (DFT) calculations confirmed P-2S. formation in an abasic phosphorodithioate model compound. ESR investigations at low temperatures and higher G-P(S−)=S concentrations showed a bimolecular conversion of P-2S. to the σ2-σ*1-bonded dimer anion radical [-P-2S 2S-P-]− [ΔG (150 K, DFT)=−7.2 kcal mol−1]. However, [-P-2S 2S-P-]− formation was not observed by pulse radiolysis [ΔG° (298 K, DFT)=−1.4 kcal mol−1]. Neither P-2S. nor [-P-2S 2S-P-]− oxidized guanine base; only base-to-backbone hole transfer occurs in phosphorodithioate. 相似文献