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991.
Six organic–inorganic hybrid materials were synthesized by the in situ oxidation of neocuproine by using MoO3/Na2MoO4 as the catalyst in the presence of Cu(NO3)2. The crystal structures of Mo8‐Cu4‐PHEN and Mo8‐Cu2‐5(2PIC) are composed of [Mo8O26]4? polyoxometalate (POM) units, whereas the crystal structure of Mo6‐Cu‐COPHEN is composed of a [Mo6O19]2? POM unit; both POM units could be considered as the active form of the catalyst. Reaction of the hybrid materials with 1,3,5‐benzenetricarboxylic acid (BTC) resulted in the formation of two different coordination polymers (CPs) under different reaction conditions. These CPs, depending on their structural attributes, exhibit distinct differences in the adsorption of H2, CO2, and water. The use of 2‐methylpyridine instead of neocuproine does not give any oxidation products under the same reaction conditions due to the incorrect positioning of the methyl group with respect to the CuII center. 相似文献
992.
993.
A new bilirubinoid analog (1) with two methoxy beta-substituents on the lactam ring of each dipyrrinone was synthesized and examined spectroscopically. It is more soluble in CH3OH and CHCl3 than bilirubin, which is insoluble in CH3OH but soluble in CHCl3. The solubility of 1 is approximately 10 microg/mL in CH3OH (vs < or =1 microg/mL for bilirubin) and approximately 3 mg/mL in CHCl3 (vs approximately 0.6 mg/mL for bilirubin). Vapor pressure osmometry indicates that 1, like bilirubin, is monomeric in CHCl3, and NMR studies show that the most stable structure has the syn-4Z,syn-15Z configuration, with the pigment's dipyrrinones engaged in intramolecular hydrogen bonding to the propionic acid carboxyl groups. And, like bilirubin, Z,Z-1 adopts a conformation that is bent in the middle into a ridge-tile shape. For the first time, a crystal structure of a bilirubin E-isomer has been obtained. Crystallization of 1 under dim room lighting gave an X-ray quality crystal of the anti-4E,syn-15Z-(photo) isomer, in which only the Z-dipyrrinone half is engaged in intramolecular hydrogen bonding to a propionic acid. Hydrogen bonding is nearly completely disengaged in the E-dipyrrinone half; yet, the ridge-tile conformation persists. 相似文献
994.
Strongly fluorescent dipyrrinones can be prepared by bridging the pyrrole and lactam nitrogens with a carbonyl group, from
reaction with N,N′-carbonyldiimidazole in the presence of a strong, non-nucleophilic base. The yellow, N,N′-carbonyl-bridged dipyrrinones typically have fluorescent quantum yields (φF) approaching 1.0. Thus, in chloroform, N,N′-bridged 9H-dipyrrinones with β-alkyl substituents: 2,3-diethyl-7,8-dimethyl has φF = 0.90 (λem = 465 nm) and 2,3-dimethyl-7,8-dimethoxy has φF = 0.84 (λem = 482 nm). In contrast, 2,3-dimethoxy-7,8-dimethyl and 2,3,7,8-tetramethoxy show red-shifted λem but with strongly reduced φF: φF = 0.10 (λem = 511 nm) and 0.08 (λem = 511 nm), respectively. Methoxy substituents on the lactam, but not the pyrrole ring act to quench the fluorescence and
shift the emission and excitation wavelengths bathochromically. The first X-ray crystal structure of an N,N′-carbonyl-bridged dipyrrinone was obtained from 7,8-dimethoxy-2,3-dimethyl-10H-dipyrrin-1-one.
Correspondence: David A. Lightner, Department of Chemistry, University of Nevada, Reno, Nevada 89557-0020, USA. 相似文献
995.
Abhishikta Chatterjee Dr. Papri Mondal Priyanka Chakraborty Bidyapati Kumar Sourav Mandal Prof. Corrado Rizzoli Dr. Rajat Saha Prof. Bibhutosh Adhikary Prof. Subrata K. Dey 《Angewandte Chemie (International ed. in English)》2023,62(42):e202307832
In this research, highly efficient heterogeneous bifunctional (BF) electrocatalysts (ECs) have been strategically designed by Fe coordination (CR) complexes, [Fe2L2(H2O)2Cl2] (C1) and [Fe2L2(H2O)2(SO4)].2(CH4O) (C2) where the high seven CR number synergistically modifies the electronic environment of the Fe centre for facilitation of H2O electrolysis. The electronic status of Fe and its adjacent atomic sites have been further modified by the replacement of −Cl− in C1 by −SO42− in C2 . Interestingly, compared to C1 , the O−S−O bridged C2 reveals superior BF activity with extremely low overpotential (η) at 10 mA cm−2 (140 mVOER, 62 mVHER) and small Tafel slope (120.9 mV dec−1OER, 45.8 mV dec−1HER). Additionally, C2 also facilitates a high-performance alkaline H2O electrolyzer with cell voltage of 1.54 V at 10 mA cm−2 and exhibits remarkable long-term stability. Thus, exploration of the intrinsic properties of metal–organic framework (MOF)-based ECs opens up a new approach to the rational design of a wide range of molecular catalysts. 相似文献
996.
Dr. Anna J. Parker Dr. Arnab Dey Mohammad Usman Qureshi Jakob M. Steiner Dr. John W. Blanchard Dr. Jochen Scheuer Nikolas Tomek Dr. Stephan Knecht Felix Josten Dr. Christoph Müller Dr. Patrick Hautle Dr. Ilai Schwartz Prof. Patrick Giraudeau Dr. Tim R. Eichhorn Dr. Jean-Nicolas Dumez 《Angewandte Chemie (International ed. in English)》2023,62(50):e202312302
The HYPNOESYS method (Hyperpolarized NOE System), which relies on the dissolution of optically polarized crystals, has recently emerged as a promising approach to enhance the sensitivity of NMR spectroscopy in the solution state. However, HYPNOESYS is a single-shot method that is not generally compatible with multidimensional NMR. Here we show that 2D NMR spectra can be obtained from HYPNOESYS-polarized samples, using single-scan acquisition methods. The approach is illustrated with a mixture of terpene molecules and a benchtop NMR spectrometer, paving the way to a sensitive, information-rich and affordable analytical method. 相似文献
997.
Ratiometric detection of analyte is highly deserving since the technique is free from background correction. This work reports the design and synthesis of a pyridine-end oligo p-phenylenevinylene (OPV) derivative, 1 and its application in ratiometric dual-mode (both colorimetric and fluorogenic) recognition of dual anions, bisulfate (LOD=12.5 ppb) followed by fluoride (LOD=18.2 ppb) by sequence-specific relay (SPR) technique. The colorless probe turns brown with addition of bisulfate and again becomes colorless with the sequential addition of fluoride ion. In addition to such naked-eye color change, interestingly the ratiometric spectroscopic signals are reversible and evidently, the probe is reusable for several cycles. Besides, in presence of bisulfate, the protonated probe molecules, owing to their larger amphiphilic characteristics, formed self-assembled nanostructures. In addition to colorimetric and fluorescent changes, 1H NMR titration and systematic DFT study evidently establish the underneath proton transfer mechanisms. Such reusable OPV-based chemosensor particularly with the capability of naked-eye recognition of dual anions using the SPR technique is seminal and possibly the first report in the literature. 相似文献
998.
999.
Many of the active sites involved in electron transfer (ET) in biology have more than one metal and are mixed valent in at least one redox state. These include Cu(A), and the polynuclear Fe-S clusters which vary in their extent of delocalization. In this tutorial review the relative contributions to delocalization are evaluated using S K-edge X-ray absorption, magnetic circular dichroism and other spectroscopic methods. The role of intra-site delocalization in ET is considered. 相似文献
1000.
Adhikari A Dey S Mandal U Das DK Ghosh S Bhattacharyya K 《The journal of physical chemistry. B》2008,112(11):3575-3580
Solvation dynamics of coumarin 480 (C480) in the secondary aggregate of a bile salt (sodium deoxycholate, NaDC) is studied using femtosecond up-conversion. The secondary aggregate resembles a long (approximately 40 A) hollow cylinder with a central water-filled tunnel. Different regions of the aggregate are probed by variation of the excitation wavelength (lambdaex) from 375 to 435 nm. The emission maximum of C480 displays an 8 nm red shift as the lambdaex increases from 345 to 435 nm. The 8 nm red edge excitation shift (REES) suggests that the probe (C480) is distributed over regions of varied polarity. Excitation at a short wavelength (375 nm) preferentially selects the probe molecule in the buried locations and exhibits slow dynamics with a major (84%) slow component (3500 ps) and a small (16%) contribution of the ultrafast component (2.5 ps). Excitation at lambdaex=435 nm (red end) corresponds to the exposed sites where solvation dynamics is very fast with a major (73%) ultrafast component (相似文献