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191.
Following some ideas of Roberto Magari, we propose trial and error
probabilistic functions, i.e. probability measures on the sentences of
arithmetic that evolve in time
by trial and error. The set
of the sentences that get
limit probability 1 is a
theory, in fact
can be a
complete set.
We prove incompleteness results for this setting, by
showing for instance that for every
there are true
sentences
that get limit probability less than
. No set
as above
can contain the set of all true
sentences,
although we exhibit some
containing all the true
sentences.
We also consider an approach based on the notions of inner probability
and outer probability, and we compare this approach with the one based
on trial and error probabilistic functions. Although the
two approaches are shown to be different, we single out an important
case in which they are equivalent.
Received March 20, 1995 相似文献
192.
193.
Giulia Bonente Francesca Passarini Stefano Cazzaniga Carmine Mancone Maria Cristina Buia Marco Tripodi Roberto Bassi Stefano Caffarri 《Photochemistry and photobiology》2008,84(6):1359-1370
To avoid photodamage, photosynthetic organisms have developed mechanisms to evade or dissipate excess energy. Lumen overacidification caused by light‐induced electron transport triggers quenching of excited chlorophylls and dissipation of excess energy into heat. In higher plants participation of the PsbS protein as the sensor of low lumenal pH was clearly demonstrated. Although light‐dependent energy quenching is a property of all photosynthetic organisms, large differences in amplitude and kinetics can be observed thus raising the question whether a single common mechanism is in action. We performed a detailed study of PsbS expression/accumulation in Chlamydomonas reinhardtii and investigated its accumulation in other algae and plants. We showed that PsbS cannot be detected in Chlamydomonas under a wide range of growth conditions. Overexpression of the endogenous psbs gene showed that the corresponding protein could not be addressed to the thylakoid membranes. Survey of different unicellular green algae showed no accumulation of anti‐PsbS reactive proteins differently from multicellular species. Nevertheless, some unicellular species exhibit high energy quenching activity, suggesting that a PsbS‐independent mechanism is activated. By correlating growth habitat and PsbS accumulation in different species, we suggest that during the evolution the light environment has been a determinant factor for the conservation/loss of the PsbS function. 相似文献
194.
Galli S Masciocchi N Tagliabue G Sironi A Navarro JA Salas JM Mendez-Liñan L Domingo M Perez-Mendoza M Barea E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(32):9890-9901
The novel porous [{M(F-pymo)(2)}(n)]2.5n H(2)O coordination networks (M=Co, Zn; F-pymo=5-fluoropyrimidin-2-olate), possessing sodalitic topology, have been synthesised and structurally characterised by means of powder diffraction methods. Thermodiffractometry demonstrated their plasticity: when heated up to 363 K, they reversibly transform into three-dimensional dehydrated [{M(F-pymo)(2)}(n)] species, with significantly different lattice parameters. Further heating induces irreversible polymorphic transformations into layered phases, in which the original MN(4) coordination sphere changes into an MN(3)O one. A mixed-metal phase, [{Co(x)Zn(1-x)(F-pymo)(2)}(n)]2.5n H(2)O, was also prepared, showing that zinc is preferentially inserted, when starting from a Co/Zn reagent ratio of 1:1. The solid-gas adsorption properties of the anhydrous 3D frameworks have been explored towards N(2), H(2) (77 K) and CH(4), CO(2) (273 K). These results show that these materials permit the diffusion of CO(2) molecules only. Remarkably, the CO(2) adsorption process for the [{Co(F-pymo)(2)}(n)] network proceeds in two steps: the first step takes place at low pressures (<600 kPa) and the second one above a threshold pressure of 600 kPa. By contrast, the [{Zn(F-pymo)(2)}(n)] network only permits CO(2) diffusion by applying pressures above 900 kPa. This type of behaviour is typical of porous networks with gated channels. The high CO(2) selectivity of these systems over the rest of the essayed probe gases is explained in terms of flexibility and polarity of the porous network. Finally, the magnetic studies on the Co(II) systems reveal that the as synthesised [{Co(F-pymo)(2)}(n)]2.5n H(2)O material behaves as an antiferromagnet with a T(N) of about 29 K. At variance, the [{Co(F-pymo)(2)}(n)] layered phase shows an unusually weak ferromagnetic ordering below 17 K, arising from a spin-canting phenomenon. 相似文献
195.
In this paper we study the Dirichlet problem in Q
T
= Ω × (0, T) for degenerate equations of porous medium-type with a lower order term:
The principal part of the operator degenerates in u = 0 according to a nonnegative increasing real function α(u), and the term grows quadratically with respect to the gradient. We prove an existence result for solutions to this problem in the framework
of the distributional solutions under the hypotheses that both f and the initial datum u
0 are bounded nonnegative functions. Moreover as further results we get an existence result for the model problem
in the case that the principal part of the operator is of fast-diffusion type, i.e. α(u) = u
m
, with −1 < m < 0.
相似文献
196.
Rotondo A Rotondo E Casella GA Grasso G 《Dalton transactions (Cambridge, England : 2003)》2008,(5):596-601
A comparative kinetic study of anomerization between the four main forms (alpha/beta-pyranosides and alpha/beta-furanosides) of D-galacturonic acid (GalAH(2), 1) and tin(IV) complexed D-galacturonate ([Sn(CH(3))(2)(GalA)(H(2)O)(2)], 2) in D(2)O, is reported. Important differences are shown by pD vs. mutarotation rate profiles of 1 and 2. Coordination, in fact, causes: i) a spectacular increase of the rate due to kinetic template assistance of the carboxylic tail holding the metal in close proximity to the reactive centre and ii) a change in the dependence of the rate on the pD. Entropic and enthalpic factors contribute to the huge activation energy decrease in 2. Anomerization rates of the complexed ligand are determined by 2D-EXSY cross-peak integration. Analysis of up to twelve direct and reverse rate constants in the pD range 7.0-2.5 evidences ring size memory, and at least one reaction path which bypasses the aldehydo open chain intermediate. Solvent oxygen atom incorporation into the ligand is, at pH 4.5, about ten fold faster when catalyzed by the metal, and proves that the metal-assisted nucleophilic attack of water on the anomeric carbon atom cannot significantly contribute to mutarotation rates that are thousands of times faster. 相似文献
197.
Andrea Fiorani Stefania Rapino Giulia Fioravanti Giovanni Valenti Massimo Marcaccio Francesco Paolucci 《Journal of Solid State Electrochemistry》2016,20(4):1037-1042
Self-assembled monolayers (SAMs) are widely used in the field of nanotechnologies and (bio)sensors. The monolayer surface properties are tailored by employing several techniques. A large set of SAM post-modification routes are commonly performed to adapt them to a variety of nano-technological and bio-technological studies as well as to several bio-sensoristic applications. Here, we report a procedure to locally modify SAMs by electrochemical desorption of alkanethiols in order to create microsized spots of bare gold area without affecting the surrounding monolayer stability. The tip of the scanning electrochemical microscope (SECM) was employed to draw microstructured pattern according to a defined geometry. The time stability of the pattern was also tested. Furthermore, the patterned surface was post-functionalized using the same alkanethiol or a ferrocene-terminated thiol, in order to tune the surface reactivity of the microstructure. The local surface properties, including reactivity and electron transfer kinetics toward redox mediator reduction, were characterized by SECM. 相似文献
198.
The structure of aldehyde-terminated alkanethiol self-assembled monolayers (SAMs) on Au(111) is investigated using scanning tunneling microscopy (STM), atomic force microscopy (AFM), and density functional theory (DFT) calculations. For the first time, the structures of aldehyde-terminated SAMs are revealed with molecular resolution. SAMs of 11-mercapto-1-undecanal exhibit the basic (radical3xradical3)R30 degrees periodicity and form various c(4x2) superstructures upon annealing. In conjunction with DFT studies, the models of the (radical3xradical3)R30 degrees and the c(4x2) superstructures are constructed. In comparison with alkanethiol SAMs, the introduction of aldehyde-termini results in smaller domain size, lower degree of long-range order, large coverage of disordered areas, and higher density of missing molecules and other point defects within domains of closely packed molecules. The origin of these structural differences is mainly attributed to the strong dipole-dipole interactions among the aldehyde termini. 相似文献
199.
New radicals containing sulfur-sulfur bonds are detected in the gas phase: disulfur hydroxide SSOH and thiosulfenoxide HSSO, stable toward dissociation by ca. 50 and 40 kcal mol(-1), respectively. Energetic, structural features and fragmentation pathways of these [S2OH] radicals and their charged species [S2OH]+ and [S2OH]- are experimentally and computationally investigated by mass spectrometric techniques and ab initio calculations. [S2OH]+ is obtained by various ion-molecule reactions leading to S2O protonated on the oxygen and end-sulfur atoms, whose proton affinity is computed at different levels of theory. The first detection of [S2OH]-, the conjugate base of the oxatrisulfane HSSOH, is also reported. 相似文献
200.
Dr. Patricia Korn Arno Classen Dr. Sudarshan Murthy Dr. Riccardo Guareschi Mirko M. Maksimainen Barbara E. Lippok Albert Galera-Prat Sven T. Sowa Catharina Voigt Prof. Dr. Giulia Rossetti Prof. Dr. Lari Lehtiö Prof. Dr. Carsten Bolm Prof. Dr. Bernhard Lüscher 《ChemistryOpen》2021,10(10):939-948
Intracellular ADP-ribosyltransferases catalyze mono- and poly-ADP-ribosylation and affect a broad range of biological processes. The mono-ADP-ribosyltransferase PARP10 is involved in signaling and DNA repair. Previous studies identified OUL35 as a selective, cell permeable inhibitor of PARP10. We have further explored the chemical space of OUL35 by synthesizing and investigating structurally related analogs. Key synthetic steps were metal-catalyzed cross-couplings and functional group modifications. We identified 4-(4-cyanophenoxy)benzamide and 3-(4-carbamoylphenoxy)benzamide as PARP10 inhibitors with distinct selectivities. Both compounds were cell permeable and interfered with PARP10 toxicity. Moreover, both revealed some inhibition of PARP2 but not PARP1, unlike clinically used PARP inhibitors, which typically inhibit both enzymes. Using crystallography and molecular modeling the binding of the compounds to different ADP-ribosyltransferases was explored regarding selectivity. Together, these studies define additional compounds that interfere with PARP10 function and thus expand our repertoire of inhibitors to further optimize selectivity and potency. 相似文献