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61.
Yvon Gauthier 《Foundations of Science》2009,14(3):153-165
This paper aims at a logico-mathematical analysis of the concept of chaos from the point of view of a constructivist philosophy
of physics. The idea of an internal logic of chaos theory is meant as an alternative to a realist conception of chaos. A brief
historical overview of the theory of dynamical systems is provided in order to situate the philosophical problem in the context
of probability theory. A finitary probabilistic account of chaos amounts to the theory of measurement in the line of a quantum-theoretical
foundational perspective and the paper concludes on the non-classical internal logic of chaos theory. Finally, deterministic
chaos points to a philosophy which asserts that chaotic systems are no less measurable than other physical systems where predictable
and non–predictable phenomena intermingle in a constructive theory of measurement.
相似文献
Yvon GauthierEmail: |
62.
Quantum control of individual spins in condensed-matter devices is an emerging field with a wide range of applications, from nanospintronics to quantum computing. The electron, possessing spin and orbital degrees of freedom, is conventionally used as the carrier of quantum information in proposed devices. However, electrons couple strongly to the environment, and so have very short relaxation and coherence times. It is therefore extremely difficult to achieve quantum coherence and stable entanglement of electron spins. Alternative concepts propose nuclear spins as the building blocks for quantum computing, because such spins are extremely well isolated from the environment and less prone to decoherence. However, weak coupling comes at a price: it remains challenging to address and manipulate individual nuclear spins. Here we show that the nuclear spin of an individual metal atom embedded in a single-molecule magnet can be read out electronically. The observed long lifetimes (tens of seconds) and relaxation characteristics of nuclear spin at the single-atom scale open the way to a completely new world of devices in which quantum logic may be implemented. 相似文献
63.
Fast and slow myosin in developing muscle fibres. 总被引:2,自引:0,他引:2
Slow and fast isoenzymes of myosin coexist in all the fibres of a fast-twitch mammalian muscle during early development. They later become segregated into different populations of fibres. Slow myosin is most abundant when the speed of contraction of the muscle is slow and the fibres are multiply innervated; its synthesis in the majority of the fibres seems to be 'switched off' when the speed of contraction increases and the fibres become innervated by single motoneurones. 相似文献
64.
A recurrent 15q13.3 microdeletion syndrome associated with mental retardation and seizures 总被引:1,自引:0,他引:1
Sharp AJ Mefford HC Li K Baker C Skinner C Stevenson RE Schroer RJ Novara F De Gregori M Ciccone R Broomer A Casuga I Wang Y Xiao C Barbacioru C Gimelli G Bernardina BD Torniero C Giorda R Regan R Murday V Mansour S Fichera M Castiglia L Failla P Ventura M Jiang Z Cooper GM Knight SJ Romano C Zuffardi O Chen C Schwartz CE Eichler EE 《Nature genetics》2008,40(3):322-328
We report a recurrent microdeletion syndrome causing mental retardation, epilepsy and variable facial and digital dysmorphisms. We describe nine affected individuals, including six probands: two with de novo deletions, two who inherited the deletion from an affected parent and two with unknown inheritance. The proximal breakpoint of the largest deletion is contiguous with breakpoint 3 (BP3) of the Prader-Willi and Angelman syndrome region, extending 3.95 Mb distally to BP5. A smaller 1.5-Mb deletion has a proximal breakpoint within the larger deletion (BP4) and shares the same distal BP5. This recurrent 1.5-Mb deletion contains six genes, including a candidate gene for epilepsy (CHRNA7) that is probably responsible for the observed seizure phenotype. The BP4-BP5 region undergoes frequent inversion, suggesting a possible link between this inversion polymorphism and recurrent deletion. The frequency of these microdeletions in mental retardation cases is approximately 0.3% (6/2,082 tested), a prevalence comparable to that of Williams, Angelman and Prader-Willi syndromes. 相似文献
65.
66.
Manuela Ambrosio Francesca Fanelli Silvia Brocchetti Francesco Raimondi Mario Mauri G. Enrico Rovati Valérie Capra 《Cellular and molecular life sciences : CMLS》2010,67(17):2979-2989
In class A GPCRs the E/DRY motif is critical for receptor activation and function. According to experimental and computational
data, R3.50 forms a double salt bridge with the adjacent E/D3.49 and E/D6.30 in helix 6, constraining the receptor in an inactive
state. The disruption of this network of interactions facilitates conformational transitions that generate a signal or constitutive
activity. Here we demonstrate that non-conservative substitution of either E129(3.49) or E240(6.30) of thromboxane prostanoid receptor (TP) resulted in mutants characterized by agonist-induced more efficient signaling properties,
regardless of the G protein coupling. Results of computational modeling suggested a more effective interaction between Gq and the agonist-bound forms of the TP mutants, compared to the wild type. Yet, none of the mutants examined revealed any
increase in basal activity, precluding their classification as constitutively active mutants. Here, we propose that these
alternative active conformations might be identified as superactive mutants or SAM. 相似文献
67.
68.
Witt H Sahin-Tóth M Landt O Chen JM Kähne T Drenth JP Kukor Z Szepessy E Halangk W Dahm S Rohde K Schulz HU Le Maréchal C Akar N Ammann RW Truninger K Bargetzi M Bhatia E Castellani C Cavestro GM Cerny M Destro-Bisol G Spedini G Eiberg H Jansen JB Koudova M Rausova E Macek M Malats N Real FX Menzel HJ Moral P Galavotti R Pignatti PF Rickards O Spicak J Zarnescu NO Böck W Gress TM Friess H Ockenga J Schmidt H Pfützer R Löhr M Simon P Weiss FU Lerch MM Teich N Keim V Berg T Wiedenmann B Luck W 《Nature genetics》2006,38(6):668-673
Chronic pancreatitis is a common inflammatory disease of the pancreas. Mutations in the genes encoding cationic trypsinogen (PRSS1) and the pancreatic secretory trypsin inhibitor (SPINK1) are associated with chronic pancreatitis. Because increased proteolytic activity owing to mutated PRSS1 enhances the risk for chronic pancreatitis, mutations in the gene encoding anionic trypsinogen (PRSS2) may also predispose to disease. Here we analyzed PRSS2 in individuals with chronic pancreatitis and controls and found, to our surprise, that a variant of codon 191 (G191R) is overrepresented in control subjects: G191R was present in 220/6,459 (3.4%) controls but in only 32/2,466 (1.3%) affected individuals (odds ratio 0.37; P = 1.1 x 10(-8)). Upon activation by enterokinase or trypsin, purified recombinant G191R protein showed a complete loss of trypsin activity owing to the introduction of a new tryptic cleavage site that renders the enzyme hypersensitive to autocatalytic proteolysis. In conclusion, the G191R variant of PRSS2 mitigates intrapancreatic trypsin activity and thereby protects against chronic pancreatitis. 相似文献
69.
Mario Pagliaro Rosaria Ciriminna 《复旦学报(自然科学版)》2005,44(5):760-761
A variety of sol-gel entrapped catalysts is available on the chemical market due to the unique advantages offered by these highly porous oxides doped with transition metal catalyst, enzymes or even living cells. Catalytic sol-gel lipase immobilizates were rapidly commercialized by Fluka after their invention by Reetz and coworkers in 1995 and have now reached a 2^nd generation level of performance. Besides esterification reactions these materials are also excellent catalysts in the kinetic resolution of chiral alcohols and amines, and are recyclable without any substantial loss in enantioselectivity (residual activity of 70 % even after 20 reaction cycles). 相似文献
70.
Sarno S Mazzorana M Traynor R Ruzzene M Cozza G Pagano MA Meggio F Zagotto G Battistutta R Pinna LA 《Cellular and molecular life sciences : CMLS》2012,69(3):449-460
8-hydroxy-4-methyl-9-nitrobenzo(g)chromen-2-one (NBC) has been found to be a fairly potent ATP site-directed inhibitor of
protein kinase CK2 (Ki = 0.22 μM). Here, we show that NBC also inhibits PIM kinases, especially PIM1 and PIM3, the latter
as potently as CK2. Upon removal of the nitro group, to give 8-hydroxy-4-methyl-benzo(g)chromen-2-one (here referred to as
“denitro NBC”, dNBC), the inhibitory power toward CK2 is almost entirely lost (IC50 > 30 μM) whereas that toward PIM1 and PIM3 is maintained; in addition, dNBC is a potent inhibitor of a number of other kinases
that are weakly inhibited or unaffected by NBC, with special reference to DYRK1A whose IC50 values with NBC and dNBC are 15 and 0.60 μM, respectively. Therefore, the observation that NBC, unlike dNBC, is a potent
inducer of apoptosis is consistent with the notion that this effect is mediated by inhibition of endogenous CK2. The structural
features underlying NBC selectivity have been revealed by inspecting its 3D structure in complex with the catalytic subunit
of Z. mays CK2. The crucial role of the nitro group is exerted both through a direct electrostatic interaction with the side chain of Lys68
and, indirectly, by enhancing the acidic dissociation constant of the adjacent hydroxyl group which interacts with a conserved
water molecule in the deepest part of the cavity. By contrast, the very same nitro group is deleterious for the binding to
the active site of DYRK1A, as disclosed by molecular docking. This provides the rationale for preferential inhibition of DYRK1A
by dNBC. 相似文献