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701.
Dr. Feda'a M. Al-Qaisi Dr. Abdussalam K. Qaroush Ibrahim K. Okashah Dr. Ala'a F. Eftaiha Dr. Petra Vasko Fatima Alsoubani Prof. Timo Repo 《欧洲无机化学杂志》2023,26(6):e202200357
Following green chemistry principles, we present a one pot synthesis of zinc curcumin complex as a homogeneous, sustainable catalyst for cyclic carbonate (CC) synthesis from CO2 and a variety of terminal and internal epoxides under 1 bar CO2 at 60 °C using DMSO as a solvent. Zinc curcumin ( Zn-Cur ) complex was identified via 1H/13C NMR and ATR-FTIR spectroscopies, elemental analysis, ionic conductivity, and quantitative silver nitrate test to confirm a 1 : 1 molar ratio of metal to the ligand. Interestingly, Zn-Cur showed an outstanding performance in catalysing the synthesis of renewable CCs including dimeric pinene and limonene carbonates. In this context, other metal complexes, including magnesium (MgII), calcium (CaII), and nickel (NiII) complexes showed good to excellent catalytic activity. Furthermore, a plausible reaction mechanism was investigated by density functional theory (DFT) calculations. The reaction was found to be overall exergonic by 39 kJ/mol and the rate determining step was CO2 insertion, which is in good agreement with the experimental findings. 相似文献
702.
Evelyn Artmann Tobias Schmider Prof. Dr. Timo Jacob Dr. Albert K. Engstfeld 《Chemphyschem》2023,24(19):e202300428
Nanoporous Au (NPG) has different properties compared to bulk Au, making it an interesting material for numerous applications. To modify the structure of NPG films for specific applications, e. g., the porosity, thickness, and homogeneity of the films, a fundamental understanding of the structure formation is essential. Here, we focus on NPG prepared via electrochemical reduction from Au oxide formed during high voltage (HV) electrolysis on poly-oriented Au single crystal (Au POSC) electrodes. These POSCs consist of a metal bead, with faces with different crystallographic orientations and allow screening of the influence of crystallographic orientation on the structure formation for different facets in one experiment. The HV electrolysis is performed between 100 ms and 30 s at 300 V and 540 V. The amount of Au oxide formed is determined by electrochemical measurements and the structural properties are investigated by scanning electron and optical microscopy. We show that the formation of Au oxide is mostly independent of the crystallographic orientation, except for thick layers, while the macroscopic structure of the NPG films depends on experimental parameters such as the Au oxide precursor thickness and the crystallographic orientation of the substrate. Possible reasons for the frequently observed exfoliation of the NPG films are discussed. 相似文献
703.
Evelyn Artmann Lukas Forschner Konstantin M. Schüttler Dr. Mohammad Al-Shakran Prof. Dr. Timo Jacob Dr. Albert K. Engstfeld 《Chemphyschem》2023,24(5):e202200645
Nanoporous Au (NPG) films have promising properties, making them suitable for various applications in (electro)catalysis or (bio)sensing. Tuning the structural properties, such as the pore size or the surface-to-volume ratio, often requires complex starting materials such as alloys, multiple synthesis steps, lengthy preparation procedures or a combination of these factors. Here we present an approach that circumvents these difficulties, enabling for a rapid and controlled preparation of NPG films starting from a bare Au electrode. In a first approach a Au oxide film is prepared by high voltage (HV) electrolysis in a KOH solution, which is then reduced either electrochemically or in the presence of H2O2. The resulting NPG structures and their electrochemically active surface areas strongly depend on the reduction procedure, the concentration and temperature of the H2O2-containing KOH solution, as well as the applied voltage and temperature during HV electrolysis. Secondly, the NPG film can be prepared directly by applying voltages that result in anodic contact glow discharge electrolysis (aCGDE). By carefully adjusting the corresponding parameters, the surface area of the final NPG film can be specifically controlled. The structural properties of the electrodes are investigated by means of XPS, SEM and electrochemical methods. 相似文献
704.
Log-linear models are the popular workhorses of analyzing contingency tables. A log-linear parameterization of an interaction model can be more expressive than a direct parameterization based on probabilities, leading to a powerful way of defining restrictions derived from marginal, conditional and context-specific independence. However, parameter estimation is often simpler under a direct parameterization, provided that the model enjoys certain decomposability properties. Here we introduce a cyclical projection algorithm for obtaining maximum likelihood estimates of log-linear parameters under an arbitrary context-specific graphical log-linear model, which needs not satisfy criteria of decomposability. We illustrate that lifting the restriction of decomposability makes the models more expressive, such that additional context-specific independencies embedded in real data can be identified. It is also shown how a context-specific graphical model can correspond to a non-hierarchical log-linear parameterization with a concise interpretation. This observation can pave way to further development of non-hierarchical log-linear models, which have been largely neglected due to their believed lack of interpretability. 相似文献
705.
Kalenius E Kekäläinen T Neitola R Beyeh K Rissanen K Vainiotalo P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(17):5220-5228
The noncovalent complexation of tetraethyl and tetraphenyl resorcinarenes with mono-, di-, and oligosaccharides was studied with negative-polarization electrospray ionization quadrupole ion trap and electrospray ionization Fourier-transform ion cyclotron resonance mass-spectrometric analysis. The saccharides formed 1:1 complexes with deprotonated resorcinarenes, which exhibited clear size and structure selectivity in their complexation. In the case of the monosaccharides, hexoses formed much more abundant and kinetically stable complexes than pentoses or deoxyhexoses. A comparison of the mono-, di-, and oligosaccharides revealed that both the relative abundance and stability of the complexes increase up to biose and triose, but start to decrease after that point, as the length of the oligosaccharide is increased. This behavior was rationalized by comparing the lowest-energy conformations of the complexes formed between the resorcinarene and oligosaccharides. This comparison was achieved by using theoretical calculations and X-ray crystal studies. 相似文献
706.
707.
Until now, partial filling micellar EKC-ESI-MS (PF-MEKC-ESI-MS) has seldom been applied for human biomolecules. In this study, determination of three electrically neutral endogenous steroid hormones, namely androstenedione, testosterone, and epitestosterone, by PF-MEKC-ESI-MS was investigated. Since ESI-MS and ESI-MS/MS behaviors of testosterone and epitestosterone proved to be nearly identical, efficient separation of the two compounds was required to obtain reliable identification. The chemical conditions as well as the instrumental parameters affecting the PF-MEKC-ESI-MS analysis were researched. In optimal conditions, ESI-MS showed excellent selectivity, and all the steroids could be identified using SIM. LODs were 0.75-5 microg/mL. The results obtained by PF-MEKC-ESI-MS were compared with those obtained by corresponding PF-MEKC-UV. PF-MEKC-UV provided better resolution, repeatability, and more than ten-fold higher sensitivity, in terms of LODs, than PF-MEKC-ESI-MS. The reasons for this were carefully examined. In comparison with PF-MEKC-UV, PF-MEKC-ESI-MS suffered from greater band broadening owing to the sheath-liquid interface. Resolution was also decreased owing to the elevated capillary temperature. Finally, we discovered that in the analysis of electrically neutral compounds, in-capillary sample concentration by micellar sweeping could be more efficiently utilized in PF-MEKC-UV than in PF-MEKC-ESI-MS. 相似文献
708.
Pedersen CS Lauritsen FR Sysoev A Viitanen AK Mäkelä JM Adamov A Laakia J Mauriala T Kotiaho T 《Journal of the American Society for Mass Spectrometry》2008,19(9):1361-1366
Ionized acetates were used as model compounds to describe gas-phase behavior of oxygen containing compounds with respect to their formation of dimers in ion mobility spectrometry (IMS). The ions were created using corona discharge at atmospheric pressure and separated in a drift tube before analysis of the ions by mass spectrometry. At the ambient operational temperature and pressure used in our instrument, all acetates studied formed dimers. Using a homolog series of n-alkyl-acetates, we found that the collision cross section of a dimer was smaller than that of a monomer with the same reduced mass. Our experiments also showed that the reduced mobility of acetate dimers with different functional groups increased in the order n-alkyl = branched chain alkyl = cyclo alkyl < aromat. For mixed n-alkyl dimers we found that the reduced mobility of acetate dimers having the same number of carbons, for example a dimer of acetyl acetate and hexyl acetate has the same reduced mobility as a dimer composed of two butyl acetates. The fundamental behavior of acetate monomers and dimers described in this paper will assist in a better understanding of the influence of dimer formation in ion mobility spectrometry. 相似文献
709.
Reiss TO Khaneja N Glaser SJ 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,154(2):192-195
Based on principles of geometric optimal control theory, coherence transfer building blocks can be derived which achieve optimal sensitivity. Here, experimental pulse sequences are presented that achieve the best possible coherence-order-selective in-phase transfer (S(-)-->I(-)) for a heteronuclear 2-spin system for any given mixing time in the absence of relaxation. For short mixing times, the optimal experiment improves the sensitivity of isotropic mixing by up to 12.5%. 相似文献
710.
W Gao JE Mueller Q Jiang T Jacob 《Angewandte Chemie (International ed. in English)》2012,51(37):9448-9452
Synergy with potential: Analysis of relevant mechanistic pathways by density functional theory, reveals the synergistic role of co-adsorbed CO and OH in promoting HCOOH electrooxidation on Pt(111). Kinetic models derived from these studies show the atomistic surface phenomena underlying the experimental CV observation in the potential range between 0.0 and 1.2?V. 相似文献