全文获取类型
收费全文 | 348篇 |
免费 | 13篇 |
专业分类
化学 | 240篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 34篇 |
物理学 | 84篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 12篇 |
2020年 | 14篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 15篇 |
2015年 | 7篇 |
2014年 | 10篇 |
2013年 | 16篇 |
2012年 | 16篇 |
2011年 | 19篇 |
2010年 | 9篇 |
2009年 | 7篇 |
2008年 | 15篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 11篇 |
2004年 | 13篇 |
2003年 | 10篇 |
2002年 | 10篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 11篇 |
1993年 | 3篇 |
1992年 | 9篇 |
1990年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1966年 | 2篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1938年 | 4篇 |
1935年 | 2篇 |
1934年 | 2篇 |
1932年 | 1篇 |
1930年 | 3篇 |
1929年 | 3篇 |
1927年 | 1篇 |
排序方式: 共有361条查询结果,搜索用时 78 毫秒
11.
Given a function space spanned by a basis {?i}, we are interested in finding another basis {gi} for which the overlaps (gi | gi) assume arbitrarily prefixed values in a subset ?? of the full set of the pairs of indices (i, j). The other overlaps are let free. We show how it is possible to perform this linear transformation ?i → gi minimizing the “distortion” J = Σi(gi – ?i | gi – ?i). 相似文献
12.
Spyridon Divanis Tugce Kutlusoy Ida Marie Ingmer Boye Isabela Costinela Man Jan Rossmeisl 《Chemical science》2020,11(11):2943
Multiple strategies to overcome the intrinsic limitations of the oxygen evolution reaction (OER) have been proposed by numerous research groups. Despite the substantial efforts, the driving force required for water oxidation is largely making the reaction inefficient. In the present work, we collected published studies involving DFT calculations for the OER, with the purpose to understand why the progress made so far, for lowering the overpotential of the reaction, is relatively small. The data revealed that the universal scaling relationship between HO* and HOO* intermediates is still present and robust, despite the variety in methods and structures used for calculating the binding energies of the intermediates. On the other hand, the data did not show a clear trend line regarding the O* binding. Our analysis suggested that trends in doped semiconducting oxides behave very differently from those in other oxides. This points towards a computational challenge in describing doped oxides in a realistic manner. We propose a way to overcome these computational challenges, which can be applied to simulations corresponding to doped semiconductors in general.Multiple strategies to overcome the intrinsic limitations of the oxygen evolution reaction (OER) have been proposed by numerous research groups. 相似文献
13.
Volker Seibert Corinna Prohl Ida Schoultz Edward Rhee Rebecca Lopez Kareem Abderazzaq Chunshui Zhou Dieter A Wolf 《BMC biochemistry》2002,3(1):22-15
Background
SCF ubiquitin ligases share the core subunits cullin 1, SKP1, and HRT1/RBX1/ROC1, which associate with different F-box proteins. F-box proteins bind substrates following their phosphorylation upon stimulation of various signaling pathways. Ubiquitin-mediated destruction of the fission yeast cyclin-dependent kinase inhibitor Rum1p depends on two heterooligomerizing F-box proteins, Pop1p and Pop2p. Both proteins interact with the cullin Pcu1p when overexpressed, but it is unknown whether this reflects their co-assembly into bona fide SCF complexes. 相似文献14.
This stability of Sb(III) and Sb(V) species was studied during single extraction from soils by water. EDTA, diluted H2SO4 and H3PO4, and oxalic acid/oxalate solutions, with and without ascorbic acid, were used as stabilizing reagent of both Sb species. Antimony redox speciation in soil extracts was performed by selective hydride generation-atomic fluorescence spectrometry. Simulated extraction procedures (without soil) showed that, except in oxalate medium, Sb(III) was oxidized to Sb(V), and this reaction was avoided with ascorbic acid. Recovery studies from a spiked agricultural soil showed that no oxidation but sorption of Sb(III) occurred during the extraction process in water and H2SO4 medium, and quantitative oxidation in EDTA and oxalate medium. With ascorbic acid, this oxidation was totally avoided in EDTA and partially avoided in oxalate solution. A new sequential extraction procedure was proposed and applied to the fractionation and redox speciation of antimony in agricultural soils, using EDTA + ascorbic acid, pH 7 (available under complexing and moderately reducible conditions); oxalic acid/oxalate + ascorbic acid (extractable in reducible conditions) and HNO3 + HCl + HF (residual fraction). The proposed extraction scheme can provide information about the availability and mobility of antimony redox species in agricultural soils. 相似文献
15.
16.
Ida Bo
ek Pavlinac Katarina Zlati Leentje Persoons Dirk Daelemans Mihajlo Banjanac Vedrana Radovanovi Kristina Butkovi Marijeta Kralj Marijana Hranjec 《Molecules (Basel, Switzerland)》2023,28(1)
A series of cyano- and amidino-substituted imidazo[4,5-b]pyridines were synthesized using standard methods of organic synthesis, and their biological activity was evaluated. Biological evaluation included in vitro assessment of antiproliferative effects on a diverse selection of human cancer cell lines, antibacterial activity against chosen Gram-positive and Gram-negative bacterial strains, and antiviral activity on a broad panel of DNA and RNA viruses. The most pronounced antiproliferative activity was observed for compound 10, which contained an unsubstituted amidino group, and compound 14, which contained a 2-imidazolinyl amidino group; both displayed selective and strong activity in sub-micromolar inhibitory concentration range against colon carcinoma (IC50 0.4 and 0.7 μM, respectively). All tested compounds lacked antibacterial activity, with the exception of compound 14, which showed moderate activity against E. coli (MIC 32 μM). Bromo-substituted derivative 7, which contained an unsubstituted phenyl ring (EC50 21 μM), and para-cyano-substituted derivative 17 (EC50 58 μM) showed selective but moderate activity against respiratory syncytial virus (RSV). 相似文献
17.
Ida Vang Andersen Rocío García-Vzquez Umberto Maria Battisti Matthias M. Herth 《Molecules (Basel, Switzerland)》2022,27(13)
Radiolabeling of tetrazines has gained increasing attention due to their important role in pretargeted imaging or therapy. The most commonly used radionuclide in PET imaging is fluorine-18. For this reason, we have recently developed a method which enables the direct aromatic 18F-fluorination of tetrazines using stannane precursors through copper-mediated fluorinations. Herein, we further optimized this labeling procedure. 3-(3-fluorophenyl)-1,2,4,5-tetrazine was chosen for this purpose because of its high reactivity and respective limited stability during the labeling process. By optimizing parameters such as elution conditions, precursor amount, catalyst, time or temperature, the radiochemical yield (RCY) could be increased by approximately 30%. These conditions were then applied to optimize the RCY of a recently successfully developed and promising pretargeting imaging agent. This agent could be isolated in a decay corrected RCY of 14 ± 3% and Am of 201 ± 30 GBq/µmol in a synthesis time of 70 min. Consequently, the RCY increased by 27%. 相似文献
18.
Bounouri Yassine Berkani Madjid Zamouche Abdelmalek Dańczak Anna Chojnacka Ida Rycerz Leszek 《Journal of Thermal Analysis and Calorimetry》2018,134(3):1589-1597
Thixoforming involves heating different types of alloys to the semisolid state at high heating rates and forming in die-casting machines or conventional presses. At temperatures higher than the solidus and lower than the liquidus, the mush metal behaves like a high-viscosity thixotropic material. Therefore, determining the thermodynamic behavior of the solid-to-liquid transition is paramount to control thixoforming processes. This article describes a simple, novel experimental setup based on differential thermal analysis (DTA) for analyzing the phase transitions in an alloy heated using high heating rates typical of industrial applications. A365 alloy was chosen to demonstrate the effectiveness of the method as the phase transformations for this alloy in semisolid materials (SSM) processing are well understood. Samples were heated to 750 °C using constant linear heating rates of 5, 10, 15, 20, 25, 50, 75, 100 and 125 °C min in a Norax 25 kW 8 kHz induction furnace with an Omron E5CK temperature controller. AISI 316 austenitic stainless steel was used as the inert reference. Comparison of the results of DTA using the proposed method and the results of simulation with Thermo-Calc® indicates that the proposed in situ DTA device and its method is suitable for analyzing phase transitions when high heating rates are used. 相似文献
19.
Francesca Di Gaudio Sergio Indelicato Roberto Monastero Grazia Ida Altieri Francesca Fayer Ornella Palesano Manuela Fontana Angelo B. Cefalù Massimiliano Greco David Bongiorno Serena Indelicato Angela Aronica Davide Noto Maurizio R. Averna 《Analytical and bioanalytical chemistry》2016,408(9):2215-2226
20.
Single‐Walled Carbon Nanotubes in Highly Viscous Media: A Comparison between the Dispersive Agents [BMIM][BF4], L121, and Triton X‐100 下载免费PDF全文
Dr. Carla Gasbarri Prof. Fausto Croce Dr. Ida Meschini Christopher H. Bowen Dr. Lisa Marinelli Prof. Antonio Di Stefano Dr. Guido Angelini 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):546-549
Dispersions of single‐walled carbon nanotubes (SWNTs) have been prepared by using the room‐temperature ionic liquid [BMIM][BF4] (1‐butyl‐3‐methylimidazolium tetrafluoroborate), the triblock copolymer Pluronic L121 [poly(ethylene oxide)5‐poly(propylene oxide)68‐poly(ethylene oxide)5] and the non‐ionic surfactant Triton X‐100 (TX100) in the pure state. The size of the SWNTs aggregates and the dispersion degree in the three viscous systems depend on the sonication time, as highlighted by UV/Vis/NIR spectroscopy and optical microscopy analysis. A nonlinear increase in conductivity can be observed as a function of the SWNTs loading, as suggested by electrochemical impedance spectroscopy. The generation of a three‐dimensional network of SWNTs showing a viscoelastic gel‐like behavior above a critical percolation concentration has been found at 25 °C in all the investigated systems by oscillatory rheology measurements. 相似文献