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181.
Michael Marquardt Dr. Beatrice Cula Vishal Budhija Dr. André Dallmann Dr. Matthias Schwalbe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(12):3991-3996
The synthesis and characterization of a hetero-dinuclear compound is presented, in which a copper(I) trishistidine type coordination unit is positioned directly above a zinc porphyrin unit. The close distance between the two coordination fragments is secured by a rigid xanthene backbone, and a unique (intramolecular) copper porphyrin-π-bond was determined for the first time in the molecular structure. This structural motif was further analyzed by temperature-dependent NMR studies: In solution at room temperature the coordinative bond fluctuates, while it can be frozen at low temperatures. Preliminary reactivity studies revealed a reduced reactivity of the copper(I) moiety towards dioxygen. The results adumbrate why nature is avoiding metal porphyrin-π-bonds by fixing reactive metal centers in a predetermined distance to each other within multimetallic enzymatic reaction centers. 相似文献
182.
Henry Dube Dr. Besnik Kasumaj Carlos Calle Dr. Beatrice Felber Dr. Makoto Saito Dr. Gunnar Jeschke Prof. Dr. François Diederich Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(1):125-135
Distal hydrogen bonding in natural dioxygen binding proteins is crucial for the discrimination between different potential ligands such as O2 or CO. In the present study, we probe the chemical requirements for proper distal hydrogen bonding in a series of synthetic model compounds for dioxygen‐binding heme proteins. The model compounds 1‐Co to 7‐Co bear different distal residues. The hydrogen bonding in their corresponding dioxygen adducts is directly measured by pulse EPR spectroscopy. The geometrical requirements for this interaction to take place were found to be narrow and very specific. Only two model complexes, 1‐Co and 7‐Co , form a hydrogen bond to bound dioxygen, which was characterized in terms of geometry and nature of the bond. The geometry and dipolar nature of this interaction in 1‐Co ‐O2 is more similar to the one in natural cobalt myoglobin (Co‐Mb), making 1‐Co the best model compound in the entire series. 相似文献
183.
As ever more protease sequences are uncovered through genome sequencing projects, efficient parallel methods to discover the potential substrates of these proteases becomes crucial. Herein we describe the first use of fluorous-based microarrays to probe peptide sequences and begin to define the scope and limitations of fluorous microarray technologies for the screening of proteases. Comparison of a series of serine proteases showed that their ability to cleave peptide substrates in solution was maintained upon immobilization of these substrates onto fluorous-coated glass slides. The fluorous surface did not serve to significantly inactivate the enzymes. However, addition of hydrophilic components to the peptide sequences could induce lower rates of substrate cleavage with enzymes such as chymotrypsin with affinities to hydrophobic moieties. This work represents the first step to creating robust protease screening platforms using noncovalent microarray interface that can easily incorporate a range of compounds on the same slide. 相似文献
184.
Michela Antonelli Pietro Ducange Beatrice Lazzerini Francesco Marcelloni 《International Journal of Approximate Reasoning》2009,50(7):1066
In this paper we propose a multi-objective evolutionary algorithm to generate Mamdani fuzzy rule-based systems with different good trade-offs between complexity and accuracy. The main novelty of the algorithm is that both rule base and granularity of the uniform partitions defined on the input and output variables are learned concurrently. To this aim, we introduce the concepts of virtual and concrete rule bases: the former is defined on linguistic variables, all partitioned with a fixed maximum number of fuzzy sets, while the latter takes into account, for each variable, a number of fuzzy sets as determined by the specific partition granularity of that variable. We exploit a chromosome composed of two parts, which codify the variables partition granularities, and the virtual rule base, respectively. Genetic operators manage virtual rule bases, whereas fitness evaluation relies on an appropriate mapping strategy between virtual and concrete rule bases. The algorithm has been tested on two real-world regression problems showing very promising results. 相似文献
185.
The problem of reducing an algebraic Riccati equation XCX − AX − XD + B = 0 to a unilateral quadratic matrix equation (UQME) of the kind PX
2 + QX + R = 0 is analyzed. New transformations are introduced which enable one to prove some theoretical and computational properties.
In particular we show that the structure preserving doubling algorithm (SDA) of Anderson (Int J Control 28(2):295–306, 1978)
is in fact the cyclic reduction algorithm of Hockney (J Assoc Comput Mach 12:95–113, 1965) and Buzbee et al. (SIAM J Numer
Anal 7:627–656, 1970), applied to a suitable UQME. A new algorithm obtained by complementing our transformations with the
shrink-and-shift technique of Ramaswami is presented. The new algorithm is accurate and much faster than SDA when applied
to some examples concerning fluid queue models. 相似文献
186.
Dr. Tiago Zaminelli Dr. Elisa Magli Prof. Francesco Frecentese Dr. Caroline H. Lescano Dr. Rafael Campos Dr. Irene Saccone Dr. Angela Corvino Dr. Paola Di Vaio Dr. Flavia Giordano Dr. Paolo Luciano Prof. Ferdinando Fiorino Prof. Elisa Perissutti Prof. Vincenzo Santagada Prof. Beatrice Severino Prof. Giuseppe Caliendo Prof. Gilberto De Nucci 《ChemistryOpen》2019,8(4):464-475
The increased levels of cyclic nucleotides (cGMP and cAMP) in enterocytes trigger intracellular mechanisms of ion and fluid secretion into the lumen, causing secretory diarrhea. Twelve novel pyridopyrimidines derived from 5-(3,5-bistrifluoromethylphenyl)-1,3-dimethyl-5,11-dihydro-1H-indeno[2,1 : 5,6]pyrido[2,3-d]pyrimidine-2,4,6-trione (FPIPP) were synthesized and evaluated on intracellular cyclic nucleotide accumulation. All compounds had no effect on either cyclic nucleotide basal levels or on pre-contracted aortic rings. The metabolic activity and viability in T84 cells, assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) and the LDH (lactate dehydrogenase) assays, respectively, were not affected by incubation with the compounds (50 μM). Compound VI almost abolished cGMP accumulation (94 % inhibition) induced by STa toxin in T834 cells and significantly reduced (69 %) forskolin-induced cAMP accumulation in Jurkat cells. Compound VI was active in an in vivo model for diarrhea in rabbits. These results prompted us to perform a microscopic histopathological analysis of intestinal tissues, showing that only compound VI preserves the intestine without significant pathological changes and with a decreased inflammatory pattern in comparison to FPIPP. In vitro stability test revealed that compound VI is resistant to oxidation promoted by atmospheric oxygen. 相似文献
187.
H. R. Kirchmayr 《Monatshefte für Chemie / Chemical Monthly》1964,95(6):1667-1670
Zusammenfassung Durch direkte Reaktion der metallischen Komponenten Dy, Ho oder Er mit Hg werden die PhasenSEHg,SEHg2 undSEHg3 (SE-Dy, Ho, Er) hergestellt. Ihre Gitterkonstanten und Kristallstrukturen [SEHg: CsCl(B 2)-Typ;SEHg2: AlB2(C 32)-Typ;SEHg3: Mg3Cd(DO19)-Typ] werden bestimmt.
A direct reaction between the metallic components Dy, Ho or Er with Hg yields the phasesREHg,REHg2 andREHg3 (RE=Dy, Ho, Er). The lattice spacings and crystal structures [REHg: CsCl(B 2)-type;REHg2: AlB2(C 32)-type;REHg3: Mg3Cd(DO19)-type] have been established.相似文献
188.
Beatrice Ruini Fulvia Spaggiari 《Abhandlungen aus dem Mathematischen Seminar der Universit?t Hamburg》2002,72(1):297-308
In this paper we compute surgery (resp. splitting) obstruction groups, here calledL-groups, and natural maps for many diagrams of oriented finite (not necessary abelian) 2-groups and homomorphisms which preserve orientations. 相似文献
189.
The interaction between the catalytic subunit Pol and the processivity subunit UL42 of herpes simplex virus DNA polymerase has been characterized structurally and mutationally and is a potential target for novel antiviral drugs. We developed and validated an assay for small molecules that could disrupt the interaction of UL42 and a Pol-derived peptide and used it to screen approximately 16,000 compounds. Of 37 "hits" identified, four inhibited UL42-stimulated long-chain DNA synthesis by Pol in vitro, of which two exhibited little inhibition of polymerase activity by Pol alone. One of these specifically inhibited the physical interaction of Pol and UL42 and also inhibited viral replication at concentrations below those that caused cytotoxic effects. Thus, a small molecule can inhibit this protein-protein interaction, which provides a starting point for the discovery of new antiviral drugs. 相似文献
190.