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1.
Herbert W. Zimmermann 《Angewandte Chemie (International ed. in English)》1986,25(2):115-130
Ethidium and acridine dyes are classical model substances for studying the binding of small, pharmacologically active molecules to DNA. Intercalation between the DNA base pairs is nearly always proposed as the most important type of binding. According to our investigations, however, there is a second type of binding, which also occurs when the concentration of the bound molecules is low and will be referred to here as external or preintercalative binding. The experimental binding isotherms show that the binding constant for intercalation KS1 is considerably smaller than that for external binding KS2 (KS1 > KS2). This surprising result is not due to the binding enthalpy (ΔH ≈ ΔH) but to the binding entropy (ΔS > ΔS). Electrostatic interactions between the dye and the DNA represent the most important contribution to both types of binding; they are supplemented by hydrogen bonds and hydrophobic interactions. The behavior of a substance in living cells, however, cannot be reliably predicted from its in vitro binding to DNA. Very few substances are bound to the DNA of the nuclear chromatin in cell culture; for example, dyes often accumulate instead in the lysosomes. In some cases the dye binds specifically and very efficiently to the mitochondria of the living cell, especially to the mitochondrial membranes, the sites of oxidative phosphorylation. 相似文献
2.
W Schoner 《Angewandte Chemie (International ed. in English)》1971,10(12):882-889
The transport of Na+ out of the cell and K+ into the cell against a concentration gradient is catalyzed by a (Na+ + K+)-activated ATPase. The way in which the cations pass through the cell membrane has not yet been elucidated. Studies on the ATP hydrolysis revealed a Na+-dependent phosphorylation of the enzyme protein; the conformation of the enzyme also appears to change. The energy required for transport of the cations against their concentration gradients is probably provided by K+-dependent hydrolysis of the enzyme-bound phosphate. The enzyme can synthesize ATP from inorganic phosphate and ADP on reversal of the cation concentration gradient. By keeping the enzyme in a particular conformation, the cardiac glycoside ouabain specifically inhibits the Na+ pump. 相似文献
3.
A device for aeration and mixing of cell or organelle suspensions in a vertical bore NMR magnet is described. Multiple external sensors (e.g., ion-selective electrodes) may be immersed in the suspension within the bore of the magnet. The sensors are positioned to avoid noise due to contact with gas bubbles and proximity to the probe head. The required sample volume is minimised. The modular design of components permits the use of the device in magnets of various internal dimensions, or with probe heads of different sample tube diameter, by modification of the simpler components of the assembly. 相似文献
4.
Sharpe G. J.; Falle S. A. E. G.; Billingham J. 《IMA Journal of Applied Mathematics》2008,73(1):107-122
Numerical simulations of a surface-catalysed flame in a tubeare performed, corresponding to an experiment where a premixedfuel is fed into a tube whose inner surface is coated with acatalyst. In these experiments, subsequent to ignition, a reactionwave can be seen as a red-hot region which propagates back alongthe tube towards the inlet, and is due to low temperature combustionoccurring only on the inner surface of the tube where the catalystis present. The solutions of a mathematical model for this behaviourshow that initial-value problems do indeed result in such steadilypropagating waves. The numerically obtained wave speeds andsteady solution are compared to a previous large Damköhlernumber (Da) asymptotic analysis using a simple reaction ratemodel, and agreement is very good even for moderately largevalues of Da. However, for such Damköhler numbers, thewave speeds are found to be much larger than observed experimentally.Indeed, the simulations show that O(1) values of Da are requiredto obtain the lower experimental wave speeds. Nevertheless,the wave speeds as a function of flow rate through the tubedo not agree well with the preliminary experimental resultsfor any choice of the parameters. A more realistic, Arrheniusreaction rate model is then considered. The Arrhenius modelpredicts a rapid change in temperature at the wave front, inmuch better agreement with the experiments than for the simplerreaction model. 相似文献
5.
设计合成了一种用于检测半胱氨酸的新型荧光探针乙二醛(N-羟乙基-1,8-二甲酰亚胺-4-萘基)单腙(NAD),该荧光探针对半胱氨酸表现出较高的灵敏度和选择性.当半胱氨酸加入NAD溶液中,会形成分子内氢键,抑制C■N的异构化,导致荧光增强.此外,探针NAD可应用于细胞内半胱氨酸的检测,表明该类型探针在生物检测应用方面具有较大的潜力. 相似文献
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Much work on semiconductors, soft solids and biological materials does not require the megabar capability of the diamond anvil cell; a few accurate kbar being all that may be required. Work in this range poses its own challenges, to make the experiments routine, safe and reliable, and well-calibrated. We contrast diamond anvil cells working at what for them is very low pressure, with traditional bombs working at what for them is dangerously high pressure. We describe our preferred solution, a single-diamond cell, and demonstrate its use with Raman data from ethanol under low pressure. Negative hydrostatic pressure cannot be obtained by traditional methods. However, we present data showing the Raman spectrum of ethanol apparently at the negative pressure of m 3 kbar. 相似文献
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Dr. Pengwei Li Linfang Yan Qingli Cao Prof. Chao Liang He Zhu Sihui Peng Yongpeng Yang Yuncai Liang Rudai Zhao Prof. Shuangquan Zang Prof. Yiqiang Zhang Prof. Yanlin Song 《Angewandte Chemie (International ed. in English)》2023,62(13):e202217910
Low-dimensional Ruddlesden-Popper (LDRP) perovskites still suffer from inferior carrier transport properties. Here, we demonstrate that efficient exciton dissociation and charge transfer can be achieved in LDRP perovskite by introducing γ-aminobutyric acid (GABA) as a spacer. The hydrogen bonding links adjacent spacing sheets in (GABA)2MA3Pb4I13 (MA=CH3NH3+), leading to the charges localized in the van der Waals gap, thereby constructing “charged-bridge” for charge transfer through the spacing region. Additionally, the polarized GABA weakens dielectric confinement, decreasing the (GABA)2MA3Pb4I13 exciton binding energy as low as ≈73 meV. Benefiting from these merits, the resultant GABA-based solar cell yields a champion power conversion efficiency (PCE) of 18.73 % with enhanced carrier transport properties. Furthermore, the unencapsulated device maintains 92.8 % of its initial PCE under continuous illumination after 1000 h and only lost 3 % of its initial PCE under 65 °C for 500 h. 相似文献