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排序方式: 共有446条查询结果,搜索用时 859 毫秒
71.
Testing is an important activity in product development. Past studies, which are developed to determine the optimal scheduling of tests, often focused on single-stage testing of sequential design process. This paper presents an analytical model for the scheduling of tests in overlapped design process, where a downstream stage starts before the completion of upstream testing. We derive optimal stopping rules for upstream and downstream stages’ testing, together with the optimal time elapsed between beginning the upstream tests and beginning the downstream development. We find that the cost function is first convex then concave increasing with respect to upstream testing duration. A one-dimensional search algorithm is then proposed for finding the unique optimum that minimizes the overall cost. Moreover, the impact of different model parameters, such as the problem-solving capacity and opportunity cost, on the optimal solution is discussed. Finally, we compare the testing strategies in overlapped process with those in sequential process, and get some additional results. The methodology is illustrated with a case study at a handset design company. 相似文献
72.
Takami T Arnold DP Fuchs AV Will GD Goh R Waclawik ER Bell JM Weiss PS Sugiura K Liu W Jiang J 《The journal of physical chemistry. B》2006,110(4):1661-1664
Initial stages of two-dimensional crystal growth of the double-decker sandwich complex Lu(Pc*)2 [Pc* = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] have been studied by scanning tunneling microscopy at the liquid/solid interface between 1-phenyloctane and highly oriented pyrolytic graphite. High-resolution images strongly suggest alignment of the double-decker molecules into monolayers with the phthalocyanine rings parallel to the surface. Domains were observed with either hexagonal or quadrate packing motifs, and the growing interface of the layer was imaged. Molecular resolution was achieved, and the face of the phthalocyanine rings appeared as somewhat diffuse circular features. The alkyl chains are proposed to be interdigitating to maintain planar side-by-side packing. 相似文献
73.
Extending band-limited constructions of orthonormal refinable functions, a special class of periodic functions is used to generate a family of band-limited refinable functions. Characterizations of Riesz bases and frames formed by integer shifts of these refinable functions are obtained. Such families of refinable functions are employed to construct band-limited biorthogonal wavelet bases and biframes with desirable time-frequency localization. 相似文献
74.
SHUbarICHI NOSÉ 《Molecular physics》2013,111(1):191-198
A molecular dynamics simulation method which can generate configurations belonging to the canonical (T, V, N) ensemble or the constant temperature constant pressure (T, P, N) ensemble, is proposed. The physical system of interest consists of N particles (f degrees of freedom), to which an external, macroscopic variable and its conjugate momentum are added. This device allows the total energy of the physical system to fluctuate. The equilibrium distribution of the energy coincides with the canonical distribution both in momentum and in coordinate space. The method is tested for an atomic fluid (Ar) and works well. 相似文献
75.
Nickel(II) meso‐Hydroxyporphyrin Complexes Revisited: Palladium‐Catalysed Synthesis,Electronic Structures of Derived Oxy Radicals,and Oxidative Coupling to a Dioxoporphodimethene Dyad
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Dr. Louisa J. Esdaile Dr. Llew Rintoul Mean See Goh Khalissa Merahi Dr. Nathalie Parizel Dr. R. Mark Wellard Dr. Sylvie Choua Prof. Dennis P. Arnold 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3430-3446
We report the synthesis and characterisation of new examples of meso‐hydroxynickel(II) porphyrins with 5,15‐diphenyl and 10‐phenyl‐5,15‐diphenyl/diaryl substitution. The OH group was introduced by using carbonate or hydroxide as nucleophile by using palladium/phosphine catalysis. The NiPor?OHs exist in solution in equilibrium with the corresponding oxy radicals NiPor?O.. The 15‐phenyl group stabilises the radicals, so that the 1H NMR spectra of {NiPor?OH} are extremely broad due to chemical exchange with the paramagnetic species. The radical concentration for the diphenylporphyrin analogue is only 1 %, and its NMR line‐broadening was able to be studied by variable‐temperature NMR spectroscopy. The EPR signals of NiPor?O. are consistent with somewhat delocalised porphyrinyloxy radicals, and the spin distributions calculated by using density functional theory match the EPR and NMR spectroscopic observations. Nickel(II) meso‐hydroxy‐10,20‐diphenylporphyrin was oxidatively coupled to a dioxo‐terminated porphodimethene dyad, the strongly red‐shifted electronic spectrum of which was successfully modelled by using time‐dependent DFT calculations. 相似文献
76.
77.
Amanda M Goh Kylie J Walters Suzanne Elsasser Rati Verma Raymond J Deshaies Daniel Finley Peter M Howley 《BMC biochemistry》2008,9(1):4
Background
The delivery of ubiquitinated proteins to the proteasome for degradation is a key step in the regulation of the ubiquitin-proteasome pathway, yet the mechanisms underlying this step are not understood in detail. The Rad23 family of proteins is known to bind ubiquitinated proteins through its two ubiquitin-associated (UBA) domains, and may participate in the delivery of ubiquitinated proteins to the proteasome through docking via the Rad23 ubiquitin-like (UBL) domain. 相似文献78.
Potassium ion mediated collagen microfibril assembly on mica 总被引:1,自引:0,他引:1
Potassium ion can critically effect the interaction between collagen microfibrils and mica leading to different ordered structures that vary dramatically with changing ion concentration. AFM images of the structures formed at different ion concentrations appear to be intermediate stages in the progression from disordered to ordered film. At 200 mM potassium ion concentration, a nanometer-thick array of aligned and bundled microfibrils covering large areas can be created easily and reproducibly on mica. 相似文献
79.
Poulsen A William A Lee A Blanchard S Teo E Deng W Tu N Tan E Sun E Goh KL Ong WC Ng CP Goh KC Bonday Z 《Journal of computer-aided molecular design》2008,22(12):897-906
The Aurora family of serine/threonine kinases are mitotic regulators involved in centrosome duplication, formation of the
bipolar mitotic spindle and the alignment of the chromosomes along the spindle. These proteins are frequently overexpressed
in tumor cells as compared to normal cells and are therefore potential therapeutic oncology targets. An Aurora A high throughput
screen revealed a promising sub-micromolar indazole-benzimidazole lead. Modification of the benzimidazole portion of the lead
to a C2 linker with a phenyl ring was proposed to achieve novelty. Docking revealed that a conjugated linker was optimal and
the resulting compounds were equipotent with the lead. Further structure-guided optimization of substituents on the 5 & 6
position of the indazole led to single digit nanomolar potency. The homology between the Aurora A & Aurora B kinase domains
is 71% but their binding sites only differ at residues 212 & 217 (Aurora A numbering). However interactions with only the
latter residue may be used for obtaining selectivity. An analysis of published Aurora A and Aurora B X-ray structures reveals
subtle differences in the shape of the binding sites. This was exploited by introduction of appropriately sized substituents
in the 4 & 6 position of the indazole leading to Aurora B selective inhibitors. Finally we calculate the conformational energy
penalty of the putative bioactive conformation of our inhibitors and show that this property correlates well with the Aurora
A binding affinity. 相似文献
80.
Lau HF Ang PC Ng VW Kuan SL Goh LY Borisov AS Hazendonk P Roemmele TL Boeré RT Webster RD 《Inorganic chemistry》2008,47(2):632-644
The reaction of the 1,2,3,5-dithiadiazolyls (4-R-C(6)H(4)CN(2)S(2))(2) (R = Me, 2a; Cl, 2b; OMe, 2c; and CF3, 2d) and (3-NC-5-tBu-C(6)H(3)CN(2)S(2))(2) (2e) with [CpCr(CO)(3)](2) (Cp = eta(5)-C(5)H(5)) (1) at ambient temperature respectively yielded the complexes CpCr(CO)(2)(eta(2)-S(2)N(2)CC(6)H(4)R) (R = 4-Me, 3a; 4-Cl, 3b; 4-OMe, 3c; and 4-CF(3), 3d) and CpCr(CO)(2)(eta(2)-S(2)N(2)CC(6)H(3)-3-(CN)-5-(tBu)) (3e) in 35-72% yields. The complexes 3c and 3d were also synthesized via a salt metathesis method from the reaction of NaCpCr(CO)(3) (1B) and the 1,2,3,5-dithiadiazolium chlorides 4-R-C(60H(4)CN(2)S(2)Cl (R = OMe, 8c; CF(3), 8d) with much lower yields of 6 and 20%, respectively. The complexes were characterized spectroscopically and also by single-crystal X-ray diffraction analysis. Cyclic voltammetry experiments were conducted on 3a-e, EPR spectra were obtained of one-electron-reduced forms of 3a-e, and variable temperature 1H NMR studies were carried out on complex 3d. Hybrid DFT calculations were performed on the model system [CpCr(CO)(2)S(2)N(2)CH] and comparisons are made with the reported CpCr(CO)(2)(pi-allyl) complexes. 相似文献