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71.
María Catalina Ramírez Jaime Plazas Camilo Torres Juan Camilo Silva Luis Camilo Caicedo Miguel Angel González 《Systemic Practice and Action Research》2012,25(2):95-116
In several rural areas in Colombia there is a serious lack of water quality supply. Thereby the problematic situation is understood
as complex one that involves stakeholders with pluralistic interests, multiple variables and requires the development of sustainable
and suitable solutions. In order to address this issue, this paper proposes an integration of engineering design framework
(CDIO) with a systemic approach. Particularly the approach emphasizes on systemic elements such as autonomy, systems within
systems, cooperation between stakeholders and cause effect relations; it also proposes a previous observing phase for engineering
design framework. Thus the proposed systemic framework aims to generate projects that improve living conditions in rural communities
and promote the production of knowledge between the stakeholders to ensure sustainability in the long term. To illustrate
the proposal, this work contains a case study that discusses a project carried out by a research team—Ingenieros Sin Fronteras Colombia—in a rural district near to Colombia’s capital. The experience, which involved and benefited 16 families in the community,
provided strong evidence to support the proposed framework. The paper concludes with a discussion about the replication of
this proposal in other contexts. 相似文献
72.
Separability of clusters is an issue that arises in many different areas, and is often used in a rather vague and subjective
manner. We introduce a combinatorial notion of interiority to derive a global view on separability of a set of entities. We
develop this approach further to evaluate the overall separability of a partition in the context of cluster analysis. Our
approach captures combinatorial and geometrical aspects of data and provides, in addition to numerical evaluations, graphical
representations particularly useful when data are not easily visualized. We illustrate the methodology on some real and simulated
datasets. 相似文献
73.
74.
The Toffoli gate is a three-quantum-bit (three-qubit) operation that inverts the state of a target qubit conditioned on the state of two control qubits. It makes universal reversible classical computation possible and, together with a Hadamard gate, forms a universal set of gates in quantum computation. It is also a key element in quantum error correction schemes. The Toffoli gate has been implemented in nuclear magnetic resonance, linear optics and ion trap systems. Experiments with superconducting qubits have also shown significant progress recently: two-qubit algorithms and two-qubit process tomography have been implemented, three-qubit entangled states have been prepared, first steps towards quantum teleportation have been taken and work on quantum computing architectures has been done. Implementation of the Toffoli gate with only single- and two-qubit gates requires six controlled-NOT gates and ten single-qubit operations, and has not been realized in any system owing to current limits on coherence. Here we implement a Toffoli gate with three superconducting transmon qubits coupled to a microwave resonator. By exploiting the third energy level of the transmon qubits, we have significantly reduced the number of elementary gates needed for the implementation of the Toffoli gate, relative to that required in theoretical proposals using only two-level systems. Using full process tomography and Monte Carlo process certification, we completely characterize the Toffoli gate acting on three independent qubits, measuring a fidelity of 68.5?±?0.5 per cent. A similar approach to realizing characteristic features of a Toffoli-class gate has been demonstrated with two qubits and a resonator and achieved a limited characterization considering only the phase fidelity. Our results reinforce the potential of macroscopic superconducting qubits for the implementation of complex quantum operations with the possibility of quantum error correction. 相似文献
75.
Sicardy B Bellucci A Gendron E Lacombe F Lacour S Lecacheux J Lellouch E Renner S Pau S Roques F Widemann T Colas F Vachier F Martins RV Ageorges N Hainaut O Marco O Beisker W Hummel E Feinstein C Levato H Maury A Frappa E Gaillard B Lavayssière M Di Sora M Mallia F Masi G Behrend R Carrier F Mousis O Rousselot P Alvarez-Candal A Lazzaro D Veiga C Andrei AH Assafin M da Silva Neto DN Jacques C Pimentel E Weaver D Lecampion JF Doncel F Momiyama T Tancredi G 《Nature》2006,439(7072):52-54
Pluto and its satellite, Charon (discovered in 1978; ref. 1), appear to form a double planet, rather than a hierarchical planet/satellite couple. Charon is about half Pluto's size and about one-eighth its mass. The precise radii of Pluto and Charon have remained uncertain, leading to large uncertainties on their densities. Although stellar occultations by Charon are in principle a powerful way of measuring its size, they are rare, as the satellite subtends less than 0.3 microradians (0.06 arcsec) on the sky. One occultation (in 1980) yielded a lower limit of 600 km for the satellite's radius, which was later refined to 601.5 km (ref. 4). Here we report observations from a multi-station stellar occultation by Charon, which we use to derive a radius, R(C) = 603.6 +/- 1.4 km (1sigma), and a density of rho = 1.71 +/- 0.08 g cm(-3). This occultation also provides upper limits of 110 and 15 (3sigma) nanobar for an atmosphere around Charon, assuming respectively a pure nitrogen or pure methane atmosphere. 相似文献
76.
77.
Human antisera detect a Plasmodium falciparum genomic clone encoding a nonapeptide repeat 总被引:3,自引:0,他引:3
M Koenen A Scherf O Mercereau G Langsley L Sibilli P Dubois L Pereira da Silva B Müller-Hill 《Nature》1984,311(5984):382-385
Plasmodium falciparum causes malaria infections in its human host. Its wide distribution in tropical countries is a major world health problem. Before a vaccine can be produced, the identification and characterization of parasite antigens is necessary. This can be achieved by the cloning and subsequent analysis of genes coding for parasite antigens. Recently established cDNA banks allow the expression of cDNA derived from the simian parasite Plasmodium knowlesi and P. falciparum in Escherichia coli. Recombinants encoding parasite antigens have been identified by immunodetection in both banks. Two of them contain repetitive units of 11 (ref. 7) or 12 (ref. 5) amino acids. We describe here the construction of an expression bank made directly from randomly generated fragments of P. falciparum genomic DNA. We detect several clones which react strongly with human African immune sera. One clone expresses an antigenic determinant composed of occasionally degenerated repeats of a peptide nonamer. 相似文献
78.
Comparison of the genomes of two Xanthomonas pathogens with differing host specificities 总被引:3,自引:0,他引:3
da Silva AC Ferro JA Reinach FC Farah CS Furlan LR Quaggio RB Monteiro-Vitorello CB Van Sluys MA Almeida NF Alves LM do Amaral AM Bertolini MC Camargo LE Camarotte G Cannavan F Cardozo J Chambergo F Ciapina LP Cicarelli RM Coutinho LL Cursino-Santos JR El-Dorry H Faria JB Ferreira AJ Ferreira RC Ferro MI Formighieri EF Franco MC Greggio CC Gruber A Katsuyama AM Kishi LT Leite RP Lemos EG Lemos MV Locali EC Machado MA Madeira AM Martinez-Rossi NM Martins EC Meidanis J Menck CF Miyaki CY Moon DH 《Nature》2002,417(6887):459-463
The genus Xanthomonas is a diverse and economically important group of bacterial phytopathogens, belonging to the gamma-subdivision of the Proteobacteria. Xanthomonas axonopodis pv. citri (Xac) causes citrus canker, which affects most commercial citrus cultivars, resulting in significant losses worldwide. Symptoms include canker lesions, leading to abscission of fruit and leaves and general tree decline. Xanthomonas campestris pv. campestris (Xcc) causes black rot, which affects crucifers such as Brassica and Arabidopsis. Symptoms include marginal leaf chlorosis and darkening of vascular tissue, accompanied by extensive wilting and necrosis. Xanthomonas campestris pv. campestris is grown commercially to produce the exopolysaccharide xanthan gum, which is used as a viscosifying and stabilizing agent in many industries. Here we report and compare the complete genome sequences of Xac and Xcc. Their distinct disease phenotypes and host ranges belie a high degree of similarity at the genomic level. More than 80% of genes are shared, and gene order is conserved along most of their respective chromosomes. We identified several groups of strain-specific genes, and on the basis of these groups we propose mechanisms that may explain the differing host specificities and pathogenic processes. 相似文献
79.
80.
Cortical plasticity seems to be critical for the establishment of permanent memory traces. Little is known, however, about the molecular and cellular processes that support consolidation of memories in cortical networks. Here we show that mice heterozygous for a null mutation of alpha-calcium-calmodulin kinase II (alpha-CaMKII+/-) show normal learning and memory 1-3 days after training in two hippocampus-dependent tasks. However, their memory is severely impaired at longer retention delays (10-50 days). Consistent with this, we found that alpha-CaMKII+/- mice have impaired cortical, but not hippocampal, long-term potentiation. Our results represent a first step in unveiling the molecular and cellular mechanisms underlying the establishment of permanent memories, and they indicate that alpha-CaMKII may modulate the synaptic events required for the consolidation of memory traces in cortical networks. 相似文献