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61.
N-Activated 2-phenylazetidines were opened regioselectively at the benzylic carbon with various allylsilanes or propargylsilane in the presence of BF3·Et2O, providing amino olefins, precursors of biomolecules such as phenyl-homo-kainoids. 相似文献
62.
Reactivity of Intramolecular Basestabilized Tin(II) Compounds with Halogens, Tin Tetrachloride, and Trichloromethane Intramolecular basestabilized tin(II) compounds of the type RN(CH2CH2Y)2Sn (Y = O, S and R = Me, t-Bu) react with halogens, tin tetrachloride, and trichloromethan at room temperature by oxydative addition reaction to tin(IV) derivatives. These compounds are characterized by n.m.r. investigations and by Mössbauer studies. 相似文献
63.
Senge MO Hatscher SS Wiehe A Dahms K Kelling A 《Journal of the American Chemical Society》2004,126(42):13634-13635
Vilsmeier formylation is one of the most widely used substitution reactions for the functionalization of porphyrins. However, its utility is limited by the electrophilic/acidic reaction conditions, deactivation of the aromatic system and regiochemical problems, the requirement for metal complexes and necessity for subsequent demetalation under harsh conditions, and low functional group tolerance. To overcome these limitations, the dithianyl group has been utilized as a latent formyl synthon in porphyrin chemistry. 2-Formyl-1,3-dithiane can be used directly in pyrrole condensation reactions to regioselectively yield porphyrins with up to four dithianyl residues. Likewise, 5-dithianyldipyrromethane could be prepared quantitatively as a key building block for various porphyrin condensation reactions yielding the respective free base formylporphyrins after deprotection. Additionally, dithianyllithium can be used as a reagent for the direct aromatic substitution of metallo- and free base porphyrins under nucleophilic conditions. 相似文献
64.
Düggeli M Goujon-Ginglinger C Ducotterd SR Mauron D Bonte C von Zelewsky A Stoeckli-Evans H Neels A 《Organic & biomolecular chemistry》2003,1(11):1894-1899
A series of new tetradentate ligands containing two bipyridine groups or two pyridine moieties carrying amine substituents has been synthesised either from 5'- and 6'-substituted chiral bipyridines, or from chiral pyridine derivatives. These precursors have been prepared from (-)-alpha-pinene or (-)-myrtenal, respectively. The structures of three tetradentate-, and of five chiral bipyridine ligands have been determined by X-ray diffraction. 相似文献
65.
Establishing a reliable method to predict the global mean temperature (Te) is of great importance because CO2 reduction activities require political and global cooperation and significant financial resources. The current climate models all seem to predict that the earth's temperature will continue to increase, mainly based on the assumption that CO2 emissions cannot be lowered significantly in the foreseeable future. Given the earth's multifactor climate system, attributing atmospheric CO2 as the only cause for the observed temperature anomaly is most likely an oversimplification; the presence of water (H2O) in the atmosphere should at least be considered. As such, Te is determined by atmospheric water content controlled by solar activity, along with anthropogenic CO2 activities. It is possible that the anthropogenic CO2 activities can be reduced in the future. Based on temperature measurements and thermodynamic data, a new model for predicting Te has been developed. Using this model, past, current, and future CO2 and H2O data can be analyzed and the associated Te calculated. This new, esoteric approach is more accurate than various other models, but has not been reported in the open literature. According to this model, by 2050, Te may increase to 15.5 ℃ under "business-as-usual" emissions. By applying a reasonable green technology activity scenario, Te may be reduced to approximately 14.2 ℃. To achieve CO2 reductions, the scenario described herein predicts a CO2 reduction potential of 513 gigatons in 30 years. This proposed scenario includes various CO2 reduction activities, carbon capturing technology, mineralization, and bio-char production; the most important CO2 reductions by 2050 are expected to be achieved mainly in the electricity, agriculture, and transportation sectors. Other more aggressive and plausible drawdown scenarios have been analyzed as well, yielding CO2 reduction potentials of 1051 and 1747 gigatons, respectively, in 30 years, but they may reduce global food production. It is emphasized that the causes and predictions of the global warming trend should be regarded as open scientific questions because several details concerning the physical processes associated with global warming remain uncertain. For example, the role of solar activities coupled with Milankovitch cycles are not yet fully understood. In addition, other factors, such as ocean CO2 uptake and volcanic activity, may not be negligible. 相似文献
66.
Although heme protein-based, amperometric nitric oxide (NO) biosensors have been well documented in previous studies, most have been conducted in anaerobic conditions. Herein we report a novel hemoglobin-based NO biosensor that is not only very sensitive but also usable in air. The heme protein was entrapped in a sodium montmorillonite film, which was immobilized at a pyrolytic graphite electrode surface. Film-entrapped hemoglobin can directly exchange electrons with the electrode, and this process has proven to favor the catalytic reduction of oxygen. In addition, NO induced a cathodic potential shift of the catalytic reduction peak of oxygen. This potential shift was proportional to the logarithm of NO concentration ranging from 4.0 × 10−11 to 5.0 × 10−6 mol/L. The detection limit has been estimated to be 20 pM, approximately four orders lower than previously reported amperometric detectors. 相似文献
67.
68.
Mathias JM 《OR manager》1991,7(7):1, 17-1, 18
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