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201.
202.
Arbuzova S. N. Verkhoturova S. I. Borodina T. N. Artem΄ev A. V. 《Journal of Structural Chemistry》2022,63(9):1383-1389
Journal of Structural Chemistry - By the interaction of CuI with bis(2-pyridyl)phosphine oxides (2-Py)2RP(O) containing E-1-phenyl-2-aroylethenyl–C(Ph)=CHC(O)R′... 相似文献
203.
A new modification to the particle swarm optimization (PSO) algorithm is proposed aiming to make the algorithm less sensitive to selection of the initial search domain. To achieve this goal, we release the boundaries of the search domain and enable each boundary to drift independently, guided by the number of collisions with particles involved in the optimization process. The gradual modification of the active search domain range enables us to prevent particles from revisiting less promising regions of the search domain and also to explore the areas located outside the initial search domain. With time, the search domain shrinks around a region holding a global extremum. This helps improve the quality of the final solution obtained. It also makes the algorithm less sensitive to initial choice of the search domain ranges. The effectiveness of the proposed Floating Boundary PSO (FBPSO) is demonstrated using a set of standard test functions. To control the performance of the algorithm, new parameters are introduced. Their optimal values are determined through numerical examples. 相似文献
204.
E. V. Ilyakina O. G. Mishchenko A. V. Piskunov S. V. Maslennikov I. V. Spirina Yu. A. Kurskii A. V. Lado 《Russian Journal of General Chemistry》2009,79(4):724-727
The quantum yields of photolytic transformations of aluminum, gallium, and indium tris(3,6-di-tert-butyl-1,2-semiquinolates) in solutions of saturated hydrocarbons were determined. The final products of photodecomposition formed upon irradiation of the compounds with the light of wavelength 313 nm were identified. The kinetic scheme for decomposition of the metal o-semiquinone complexes upon irradiation is suggested. 相似文献
205.
G.?I.?Mel’man N.?P.?Mishchenko V.?A.?Denisenko D.?V.?Berdyshev V.?P.?Glazunov V.?F.?Anufriev 《Russian Journal of Organic Chemistry》2009,45(1):37-43
2-Hydroxynaphthazarins reacted with aqueous ammonia at the C1=O carbonyl group, following the addition-elimination pattern with formation of 8-aminojuglone derivatives. Reactions of 2,3-dihydroxynaphthazarins with the same reagent involved the C2=O carbonyl group of the corresponding 1,2-naphthoquinoid tautomer to produce 2-aminonaphthazarin derivatives. 7-Ethyl-2,3,6-trihydroxynaphthazarin (echinochrome) reacted with aqueous ammonia to give 3(2)-amino-7-ethyl-2(3),6-dihydroxynaphthazarins (echinamines A and B) that are metabolites recently isolated from the sand dollar Scaphechinus mirabilis. 相似文献
206.
Greis KD Zhou S Burt TM Carr AN Dolan E Easwaran V Evdokimov A Kawamoto R Roesgen J Davis GF 《Journal of the American Society for Mass Spectrometry》2006,17(6):815-822
Mass Spectrometry (MS) has been widely reported for measuring the conversion of substrates to products for enzyme assays. These measurements are typically performed by time-consuming LC-MS to eliminate buffer salts that interfere with electrospray ionization MS. However, matrix-assisted laser desorption ionization, time-of-flight MS (MALDI-TOF MS) offers a label-free and direct readout of substrate and product, a fast sampling rate, and is tolerant of many buffer salts, reagents, and compounds that are typically found in enzyme reaction mixtures. In this report, a demonstration of how MALDI-TOF MS can be used to directly measure ratios of substrates and products to produce IC(50) curves for rapid enzyme assays and compound screening is provided. Typical reproducibility parameters were <7% RSD-a value comparable to ESI MS quantitative assays and well within the acceptable limits for screening assays. The speed of the MALDI readout is currently about 10 s per sample, thus allowing for over 7500 samples/day. From a simplicity standpoint, the enzymatic reaction mixtures are prepared by liquid handling robots, the reactions are stopped by addition of a 10 times volume of acidic matrix solution, and the samples are simultaneously transferred to MALDI target plate for analysis. Importantly, the ratios of substrate to product are of sufficient reproducibility to eliminate the need for internal standards and, thus, minimize the cost and increasing the speed of assay development. 相似文献
207.
Kireev AS Nadein ON Agustin VJ Bush NE Evidente A Manpadi M Ogasawara MA Rastogi SK Rogelj S Shors ST Kornienko A 《The Journal of organic chemistry》2006,71(15):5694-5707
Pancratistatin is a potent anticancer natural product, whose clinical evaluation is hampered by the limited natural abundance and the stereochemically complex structure undermining practical chemical preparation. Fifteen aromatic analogues of conduritol F, l-chiro-inositol, and dihydroconduritol F that possess four of the six pancratistatin stereocenters have been synthesized and evaluated for anticancer activity. These compounds serve as truncated pancratistatin analogues lacking the lactam ring B, but retaining the crucial C10a-C10b bond with the correct stereochemistry. The lack of activity of these compounds provides further insight into pancratistatin's minimum structural requirements for cytotoxicity, particularly the criticality of the intact phenanthridone skeleton. Significantly, these series provide rare examples of simple aromatic conduritol and inositol analogues and, therefore, this study expands the chemistry and biology of these important classes of compounds. 相似文献
208.
Alexei A. Belik Artem P. Malakho Bogdan I. Lazoryak 《Journal of solid state chemistry》2006,179(1):161-168
Solid solutions of Sr9+xCo1.5−x(PO4)7 were found in the compositional range of 0.05?x?0.30. The structure of Sr9.2Co1.3(PO4)7 (x=0.2) was determined from single crystal X-ray diffraction (space group (No. 166); Z=3; and ; ; ; ) and refined to R1=0.0343 and wR2=0.0633 for 586 reflections with I>2σ(I). Sr9.2Co1.3(PO4)7 is structurally related to β-Ca3(PO4)2 and Sr3(PO4)2 and has disordered arrangements of some Sr2+, Co2+, and PO43− ions. Sr2+ ions at a 9e site are statistically disordered among four positions near the center of symmetry. Co2+ and Sr2+ ions are split along the c-axis to occupy a 6c site that is 75% vacant. The P1O4 tetrahedra are orientationally disordered. Sr2+ ions at an 8-fold coordinated 18h site, Co2+ ions at an octahedral 3a site, and the P2O4 tetrahedra are ordered in the structure of Sr9.2Co1.3(PO4)7. Features of Raman spectra are discussed in relation to the crystallographic structure of Sr9.2Co1.3(PO4)7 and in comparison with Raman spectra of β-Ca3(PO4)2-type and Sr3(PO4)2-type compounds. Sr9.2Co1.3(PO4)7 is paramagnetic between 2 and 300 K with an effective magnetic moment of 4.98μB per Co2+ ion. 相似文献
209.
Current models used to predict the stereochemical outcome of organocopper conjugate addition processes focus on the nucleophilic addition step as stereochemistry-determining. Recent kinetic, NMR, kinetic isotope effect, and theoretical density functional studies strongly support the proposal that stereochemical preferences in these processes are dictated by the reductive elimination step, transforming Cu(III) to Cu(I) intermediates. A new model that considers various steric and stereoelectronic factors involved in the transition state of the reductive elimination step is proposed and then used to interpret the results of systematic studies of arylcuprate conjugate addition reactions with cis and trans gamma-alkoxy-alpha,beta-enoates. The results give rise to the following selectivity guidelines for this process. To achieve high anti-addition diastereoselectivities the use of trans esters with a bulky nonalkoxy substituent at the gamma-position is recommended. While stereoelectronics disfavor syn-addition, a judicious choice of properly sized gamma-substituents may lead to the predominant formation of syn-products, especially with cis enoates. However, high syn-selectivities may be achieved by using gamma-amino-alpha,beta-enoates. 相似文献
210.
Kurbatov S Tatarov A Minkin V Goumont R Terrier F 《Chemical communications (Cambridge, England)》2006,(41):4279-4281
Coupling of superelectrophilic 4,6-dinitrobenzofuroxan with a pi-excessive indolizine structure affords a strongly dipolar substitution product which undergoes a facile but unusual rearrangement induced by an intramolecular oxygen atom transfer from the N-oxide functionality of the DNBF moiety. 相似文献