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71.
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73.
Li Jingqun Kirubarajan Thia Tharmarasa R. Brown Daly Pattipati Krishna R. 《Journal of Global Optimization》2021,81(3):691-716
Journal of Global Optimization - In this paper, we extend the purely dual formulation that we recently proposed for the three-dimensional assignment problems to solve the more general... 相似文献
74.
Methods are presented by which both harmonic input magnitudes and dynamic transmissibility can be estimated when only the output of a system can be measured. This is possible when the input to a system consists of components whose amplitude remains constant although their time scale changes with speed. An example of this occurs with gear induced vibration where the forcing function is provided by errors which remain constant in amplitude. Examples given show how the methods can be used to estimate the static transmission error components of gear drives from dynamic response measurements where drive speeds are restricted. 相似文献
75.
Characterizing Polyoxovanadate-Alkoxide Clusters Using Vanadium K-Edge X-Ray Absorption Spectroscopy
Rachel L. Meyer Samuel M. Greer Anastasia V. Blake Samantha K. Cary Alexander S. Ditter Scott R. Daly Feng Li Stosh A. Kozimor Ellen M. Matson Veronika Mocko Gerald T. Seidler Benjamin W. Stein Samuel D. Weinstein 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(5):1592-1597
A number of technologies would benefit from developing inorganic compounds and materials with specific electronic and magnetic exchange properties. Unfortunately, designing compounds with these properties is difficult because metal⋅⋅⋅metal coupling schemes are hard to predict and control. Fully characterizing communication between metals in existing compounds that exhibit interesting properties could provide valuable insight and advance those predictive capabilities. One such class of molecules are the series of Lindqvist iron-functionalized and hexavanadium polyoxovanadate-alkoxide clusters, which we characterized here using V K-edge X-ray absorption spectroscopy. Substantial changes in the pre-edge peak intensities were observed that tracked with the V 3d-electron count. The data also suggested substantial delocalization between the vanadium cations. Meanwhile, the FeIII cations were electronically isolated from the polyoxovanadate core. 相似文献
76.
Cross WB Daly CG Ackerman RL George IR Singh K 《Dalton transactions (Cambridge, England : 2003)》2011,40(2):495-505
With a view to applications in bifunctional catalysis, a modular cross-coupling strategy has been used to prepare amine bis(imidazolium) salts (3a and 3b) and an amine mono(imidazolium) salt (6) as precursors to chelating amido-NHC ligands. Treating the pro-ligands 3 with 3 equivalents of the bulky base KHMDS and Pd(OAc)(2) or PtCl(2)(COD) gave the four amido bis(N-heterocyclic carbene) pincer complexes [CNC-R]M-I [M = Pd (7) or Pt (8); R = i-Pr (a) or n-Bu (b)], including the first examples of platinum complexes of a CNC ligand. The reaction of 7a with AgOTf in pyridine gave the cationic complex {[CNC-i-Pr]Pd-py}OTf (9a). Heating a mixture of amine mono(imidazolium) salt 6 with PdCl(2) or K(2)PtCl(4), K(2)CO(3) and KI in pyridine at 100 °C gave the complexes [C,NH]MI(2)py [M = Pd (10) or Pt (11)], in which the amine arm of the NHC ligand is not deprotonated and does not coordinate to the metal. For a solution of 10 in 1,4-dioxane, deprotonation of the amine occurred in a biphasic reaction with aqueous KOH at 40 °C, giving the dimeric amido complex {[C,N]Pd(μ-OH)}(2) (12). The more inert Pt analogue 11 was unreactive under the same conditions. Solid-state structures of the complexes 7a, 7b, 9a, 10, 11 and 12 have been determined by single crystal X-ray diffraction. 相似文献
77.
Harry J. Sterling Michael P. Daly Geoffrey K. Feld Katie L. Thoren Alexander F. Kintzer Bryan A. Krantz Evan R. Williams 《Journal of the American Society for Mass Spectrometry》2010,21(10):1762-1774
The effects of two supercharging reagents, m-nitrobenzyl alcohol (m-NBA) and sulfolane, on the charge-state distributions and conformations of myoglobin ions formed by electrospray ionization
were investigated. Addition of 0.4% m-NBA to aqueous ammonium acetate solutions of myoglobin results in an increase in the maximum charge state from 9+ to 19+,
and an increase in the average charge state from 7.9+ to 11.7+, compared with solutions without m-NBA. The extent of supercharging with sulfolane on a per mole basis is lower than that with m-NBA, but comparable charging was obtained at higher concentration. Arrival time distributions obtained from traveling wave
ion mobility spectrometry show that the higher charge state ions that are formed with these supercharging reagents are significantly
more unfolded than lower charge state ions. Results from circular dichroism spectroscopy show that sulfolane can act as chemical
denaturant, destabilizing myoglobin by ∼1.5 kcal/mol/M at 25 °C. Because these supercharging reagents have low vapor pressures,
aqueous droplets are preferentially enriched in these reagents as evaporation occurs. Less evaporative cooling will occur
after the droplets are substantially enriched in the low volatility supercharging reagent, and the droplet temperature should
be higher compared with when these reagents are not present. Protein unfolding induced by chemical and/or thermal denaturation
in the electrospray droplet appears to be the primary origin of the enhanced charging observed for noncovalent protein complexes
formed from aqueous solutions that contain these supercharging reagents, although other factors almost certainly influence
the extent of charging as well. 相似文献
78.
Daly AM Mitchell EG Sanchez DA Block E Kukolich SG 《The journal of physical chemistry. A》2011,115(50):14526-14530
The microwave spectrum for N-hydroxypyridine-2(1H)-thione (pyrithione) was measured in the frequency range 6-18 GHz, providing accurate rotational constants and nitrogen quadrupole coupling strengths for three isotopologues, C(5)H(4)(32)S(14)NOH, C(5)H(4)(32)S(14)NOD, and C(5)H(4)(34)S(14)NOH. Pyrithione was found to be in a higher concentration in the gas phase than the other tautomer, 2-mercaptopyridine-N-oxide (MPO). Microwave spectroscopy is best suited to determine which structure predominates in the gas phase. The measured rotational constants were used to accurately determine the coordinates of the substituted atoms and provided sufficient data to determine some of the important structural parameters for pyrithione, the only tautomer observed in the present work. The spectra were obtained using a pulsed-beam Fourier transform microwave spectrometer, with sufficient resolution to allow accurate measurements of the (14)N nuclear quadrupole hyperfine interactions. Ab initio calculations provided structural parameters and quadrupole coupling strengths that are in very good agreement with measured values. The experimental rotational constants for the parent compound are A = 3212.10(1), B = 1609.328(7), and C = 1072.208(6) MHz, yielding the inertial defect Δ(0) = -0.023 amu·?(2) for the C(5)H(4)(32)S(14)NOH isotopologue. The observed near zero inertial defect clearly indicates a planar structure. The least-squares fit structural analysis yielded the experimental bond lengths R(O-H) = 0.93(2) ?, R(C-S) = 1.66(2) ?, and angle (N-O-H) = 105(4)° for the ground state structure. 相似文献
79.
The cyclotides are a family of small disulfide rich proteins that have a cyclic peptide backbone and a cystine knot formed by three conserved disulfide bonds. The combination of these two structural motifs contributes to the exceptional chemical, thermal and enzymatic stability of the cyclotides, which retain bioactivity after boiling. They were initially discovered based on native medicine or screening studies associated with some of their various activities, which include uterotonic action, anti-HIV activity, neurotensin antagonism, and cytotoxicity. They are present in plants from the Rubiaceae, Violaceae and Cucurbitaceae families and their natural function in plants appears to be in host defense: they have potent activity against certain insect pests and they also have antimicrobial activity. There are currently around 50 published sequences of cyclotides and their rate of discovery has been increasing over recent years. Ultimately the family may comprise thousands of members. This article describes the background to the discovery of the cyclotides, their structural characterization, chemical synthesis, genetic origin, biological activities and potential applications in the pharmaceutical and agricultural industries. Their unique topological features make them interesting from a protein folding perspective. Because of their highly stable peptide framework they might make useful templates in drug design programs, and their insecticidal activity opens the possibility of applications in crop protection. 相似文献
80.
Christiana Kitsiou Jordan J. Hindes Phillip I'Anson Paula Jackson Thomas C. Wilson Eleanor K. Daly Hannah R. Felstead Peter Hearnshaw Dr. William P. Unsworth 《Angewandte Chemie (International ed. in English)》2015,54(52):15794-15798
Structurally diverse macrocycles and medium‐sized rings (9–24 membered scaffolds, 22 examples) can be generated through a telescoped acylation/ring‐expansion sequence, leading to the insertion of linear fragments into cyclic β‐ketoesters without performing a discrete macrocyclization step. The key β‐ketoester motif is regenerated in the ring‐expanded product, meaning that the same sequence of steps can then be repeated (in theory indefinitely) with other linear fragments, allowing macrocycles with precise substitution patterns to be “grown” from smaller rings using the successive ring‐expansion (SuRE) method. 相似文献