全文获取类型
| 收费全文 | 842篇 |
| 免费 | 43篇 |
专业分类
| 化学 | 591篇 |
| 晶体学 | 4篇 |
| 力学 | 21篇 |
| 数学 | 82篇 |
| 物理学 | 187篇 |
出版年
| 2024年 | 5篇 |
| 2023年 | 7篇 |
| 2022年 | 21篇 |
| 2021年 | 25篇 |
| 2020年 | 28篇 |
| 2019年 | 35篇 |
| 2018年 | 16篇 |
| 2017年 | 14篇 |
| 2016年 | 45篇 |
| 2015年 | 26篇 |
| 2014年 | 28篇 |
| 2013年 | 36篇 |
| 2012年 | 54篇 |
| 2011年 | 72篇 |
| 2010年 | 32篇 |
| 2009年 | 25篇 |
| 2008年 | 40篇 |
| 2007年 | 42篇 |
| 2006年 | 36篇 |
| 2005年 | 35篇 |
| 2004年 | 32篇 |
| 2003年 | 24篇 |
| 2002年 | 18篇 |
| 2001年 | 4篇 |
| 2000年 | 7篇 |
| 1999年 | 5篇 |
| 1998年 | 4篇 |
| 1997年 | 15篇 |
| 1996年 | 8篇 |
| 1995年 | 6篇 |
| 1994年 | 15篇 |
| 1993年 | 8篇 |
| 1992年 | 6篇 |
| 1991年 | 12篇 |
| 1990年 | 6篇 |
| 1989年 | 4篇 |
| 1987年 | 6篇 |
| 1986年 | 8篇 |
| 1985年 | 4篇 |
| 1983年 | 6篇 |
| 1982年 | 3篇 |
| 1978年 | 4篇 |
| 1977年 | 4篇 |
| 1976年 | 5篇 |
| 1973年 | 4篇 |
| 1968年 | 4篇 |
| 1967年 | 5篇 |
| 1966年 | 3篇 |
| 1960年 | 4篇 |
| 1958年 | 4篇 |
排序方式： 共有885条查询结果，搜索用时 15 毫秒
11.
A new spectrophotometric method for the determination of traces of tin in steel is presented. The tin is isolated by an acid sulfide separation and a double carbamate-chloroform extraction and then determined by a phenylfluorone method in which the selectivity is increased by the use of peroxide and oxalate as masking agents and the sensitivity is increased by extracting the colored tin compound into a small volume of MIBK for the spectrophotometric analysis. 相似文献
12.
Dr. Zhen Jiang Ming Li Tan Mahdiar Taheri Dr. Qiao Yan Prof. Takuya Tsuzuki Dr. Michael G. Gardiner Broden Diggle Prof. Luke A. Connal 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(18):7115-7122
The most pressing challenges for light-driven hydrogel actuators include reliance on UV light, slow response, poor mechanical properties, and limited functionalities. Now, a supramolecular design strategy is used to address these issues. Key is the use of a benzylimine-functionalized anthracene group, which red-shifts the absorption into the visible region and also stabilizes the supramolecular network through π–π interactions. Acid–ether hydrogen bonds are incorporated for energy dissipation under mechanical deformation and maintaining hydrophilicity of the network. This double-crosslinked supramolecular hydrogel developed via a simple synthesis exhibits a unique combination of high strength, rapid self-healing, and fast visible-light-driven shape morphing both in the wet and dry state. As all of the interactions are dynamic, the design enables the structures to be recycled and reprogrammed into different 3D objects. 相似文献
13.
James O. Jensen Pallassana N. Krishnan Luke A. Burke 《Journal of Molecular Structure》1996,370(2-3):245-252
Twenty-two structures with the empirical formula H3CNO are presented. These structures are examined since they have the same formula as the H2O…HCN complex. The H2O…HCN potential energy surface is of interest to chemists studying the water catalyzed polymerization of HCN. Structures, thermodynamics, and vibrational spectra are examined. 相似文献
14.
T. H. Prettyman C. S. Cooper P. N. Luke P. A. Russo M. Amman D. J. Mercer 《Journal of Radioanalytical and Nuclear Chemistry》1998,233(1-2):257-264
A physics-based approach to gamma-ray response-function generation is presented in which the response of CdZnTe detectors
is modeled from first principles. Numerical modeling is used to generate response functions needed for spectrum analysis for
general detector configurations (e.g., electrode design, detector materials and geometry, and operating conditions). With
numerical modeling, requirements for calibration and characterization are significantly reduced. Elements of the physics-based
model, including gamma-ray transport, charge carrier drift and diffusion, and circuit response, are presented. Calculated
and experimental gamma-ray spectra are compared for a coplanar-grid CdZnTe detector. 相似文献
15.
John J. Porter Joel Luke Murray Kenneth B. Takvorian 《Journal of heterocyclic chemistry》1973,10(1):43-46
The complexing ability of derivatives of azobenzene (I) is well known (I) and responsible for the production of a wide variety of dyestuffs and analytical chemicals. While the azo group generally participates in the coordination, the determination of the degree of its interaction is complicated by other functional groups which are also coordinated with the transition metal. In a previous publication (2), we reported the preparation of the silver and palladium complexes of benzo[c]cinnoline (II) and proposed that these results might be used to explain the electron donor properties of azobenzene. We are now reporting the preparation of some additional complexes with ligands containing the azo group. 相似文献
16.
J. Moche S. J. Rubaschkin S. M. Gutman S. L. Yovanovitch W. L. Miller B. L. Clarke L. A. Wooten C. Luke A. Winkel und G. Proske 《Fresenius' Journal of Analytical Chemistry》1938,112(7-8):266-271
Ohne Zusammenfassung 相似文献
17.
Pu Duan Bo Zhi Luke Coburn Christy L. Haynes Klaus Schmidt-Rohr 《Magnetic resonance in chemistry : MRC》2020,58(11):1130-1138
The composition of fluorescent polymer nanoparticles, commonly referred to as carbon dots, synthesized by microwave-assisted reaction of citric acid and ethylenediamine was investigated by 13C, 13C{1H}, 1H─13C, 13C{14N}, and 15N solid-state nuclear magnetic resonance (NMR) experiments. 13C NMR with spectral editing provided no evidence for significant condensed aromatic or diamondoid carbon phases. 15N NMR showed that the nanoparticle matrix has been polymerized by amide and some imide formation. Five small, resolved 13C NMR peaks, including an unusual ═CH signal at 84 ppm (1H chemical shift of 5.8 ppm) and ═CN2 at 155 ppm, and two distinctive 15N NMR resonances near 80 and 160 ppm proved the presence of 5-oxo-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine-7-carboxylic acid (IPCA) or its derivatives. This molecular fluorophore with conjugated double bonds, formed by a double cyclization reaction of citric acid and ethylenediamine as first shown by Y. Song, B. Yang, and coworkers in 2015, accounts for the fluorescence of the carbon dots. Cross-peaks in a 1H─13C HETCOR spectrum with brief 1H spin diffusion proved that IPCA is finely dispersed in the polyamide matrix. From quantitative 13C and 15N NMR spectra, a high concentration (18 ± 2 wt%) of IPCA in the carbon dots was determined. A pronounced gradient in 13C chemical-shift perturbations and peak widths, with the broadest lines near the COO group of IPCA, indicated at least partial transformation of the carboxylic acid of IPCA by amide or ester formation. 相似文献
18.
Atika Muhammad Dr. Graziano Di Carmine Luke Forster Dr. Carmine D'Agostino 《Chemphyschem》2020,21(11):1101-1106
Solvent effects in homogeneous catalysis are known to affect catalytic activity. Whilst these effects are often described using qualitative features, such as Kamlet-Taft parameters, experimental tools able to quantify and reveal in more depth such effects have remained unexplored. In this work, PFG NMR diffusion and T1 relaxation measurements have been carried out to probe solvent effects in the homogeneous catalytic reduction of propionaldehyde to 1-propanol in the presence of aluminium isopropoxide catalyst. Using data on diffusion coefficients it was possible to estimate trends in aggregation of different solvents. The results show that solvents with a high hydrogen-bond accepting ability, such as ethers, tend to form larger aggregates, which slow down the molecular dynamics of aldehyde molecules, as also suggested by T1 measurements, and preventing their access to the catalytic sites, which results in the observed decrease of catalytic activity. Conversely, weakly interacting solvents, such as alkanes, do not lead to the formation of such aggregates, hence allowing easy access of the aldehyde molecules to the catalytic sites, resulting in higher catalytic activity. The work reported here is a clear example on how combining traditional catalyst screening in homogeneous catalysis with NMR diffusion and relaxation time measurements can lead to new physico-chemical insights into such systems by providing data able to quantify aggregation phenomena and molecular dynamics. 相似文献
19.
Richard N. Butler Denise C. Grogan Luke A. Burke 《Journal of heterocyclic chemistry》1997,34(6):1825-1827
An unusual inverted V-shaped Hammett plot has been observed for substituent effects at the N-terminus of 1,2,3-triazolium-1-imide 1,3-dipoles in cycloaddition reactions. Theoretical studies (3-21G and 6-31G) suggest strong resonance interactions separately stabilizing both ends of the dipole. 相似文献
20.
Dr. Lei Qin Dr. Luke Schkeryantz Prof. Yiying Wu 《Angewandte Chemie (International ed. in English)》2023,62(10):e202213996
A battery cathode based on the superoxide/peroxide redox not only inherits the advantage of oxygen (O2) batteries in high capacities and low costs but also overcomes the disadvantages in O2 storage, electrolyte evaporation, and anode deactivation due to O2 crossover. Herein, we report an enhanced potassium superoxide (KO2)/peroxide (K2O2) conversion by adopting a high-donicity anion additive in the ether-based electrolyte. Such an anion was synthesized via a “Solvent-in-Anion” strategy and validated to enhance the electron donicity of the electrolyte. The use of high-donicity anion could lead to enhanced KO2 utilization (≈90.2 %) by retarding electrode passivation and allow the full charging back of K2O2 through the solution-mediated pathway without electrocatalysts. No apparent cell degradation is observed during the first 120 cycles by controlling the reversible depth-of-discharge capacity at 292 mAh g−1 within an O2-free region. The K−KO2 cell delivers a high energy efficiency (>84.4 %) and a lifespan of over 1440 hours. 相似文献