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81.
82.
Classical unidimensional scaling provides a difficult combinatorial task. A procedure formulated as a nonlinear programming
(NLP) model is proposed to solve this problem. The new method can be implemented with standard mathematical programming software.
Unlike the traditional procedures that minimize either the sum of squared error (L
2 norm) or the sum pf absolute error (L
1 norm), the proposed method can minimize the error based on any L
p
norm for 1 ≤p < ∞. Extensions of the NLP formulation to address a multidimensional scaling problem under the city-block model are also
discussed. 相似文献
83.
84.
Perfluorooctane sulfonate (PFOS) and related fluorochemicals in chicken egg in China 总被引:4,自引:0,他引:4
WANG Yuan YEUNG Leo Wai Yin YAMASHITA Nobuyoshi TANIYASU Sachi SO Man Ka Margaret B. MURPHY LAM Paul Kwan Sing 《科学通报(英文版)》2008,53(4):501-507
The ubiquitous occurrence of perfluorinated compounds (PFCs) in environmental samples has drawn much attention. Recent human exposure studies found relatively high perfluorooctane sulfonate (PFOS) concentrations in blood samples from several cities in China when compared with other countries. The objectives of the present study were: (1) to measure PFC concentrations and compositions in chicken egg samples from local markets in China; and (2) to conduct a preliminary human health risk assessment of egg consumption. Eight pooled egg samples from eight locations were analyzed for 11 PFCs. The results showed that close to 100% of the PFOS in the egg was distributed in egg yolk and PFOS was not detected in egg white (〈0.08 ng/g wet weight, w/w). Of the perfluoroalkylsulfonates, only PFOS was detected in all egg samples, while of the perfluoroalkylcarboxylates, perfluoroundecanoic acid (PFUnDA) was detected in all samples, followed by perfluorooctanoate (PFOA) (75% occurrence) and perfluorodecanoic acid (PFDA) (50% occurrence). PFOS concentrations in egg ranged from 45.0 to 86.9 ng/g w/w. The results suggested that current concentrations of PFOS in domestic chicken eggs are unlikely to cause immediate harm to Chinese populations. 相似文献
85.
In this paper,the complexity of intra coding is first analyzed so as to achieve a weight of complexity measurement for each intra mode.Then.a new complexity sealable control algorithm for intra coding in H.264 is proposed,based on the rearrangement of the order of candidate modes and an efficient complexity allocation and control(CAAC)scheme at the macroblock(MB)level.The candidate modes of each MB ale rearranged according to the local-edge information.Experimental results show that our proposed algorithm can make an appropriate cut-off point of the candidate modes sequence adaptively according to the current energy condition of a mobile device,so as to adjust the complexity at any level while maximizing the video quality,which can prolong the operational lifetime of the battery with minimum degradation in video quality. 相似文献
86.
The d-enantiomers of amino acids have been thought to have relatively minor functions in biological processes. While l-amino acids clearly predominate in nature, d-amino acids are sometimes found in proteins that are not synthesized by ribosomes, and d-Ala and d-Glu are routinely found in the peptidoglycan cell wall of bacteria. Here, we review recent findings showing that d-amino acids have previously unappreciated regulatory roles in the bacterial kingdom. Many diverse bacterial phyla synthesize
and release d-amino acids, including d-Met and d-Leu, which were not previously known to be made. These noncanonical d-amino acids regulate cell wall remodeling in stationary phase and cause biofilm dispersal in aging bacterial communities.
Elucidating the mechanisms by which d-amino acids govern cell wall remodeling and biofilm disassembly will undoubtedly reveal new paradigms for understanding how
extracytoplasmic processes are regulated as well as lead to development of novel therapeutics. 相似文献
87.
Yang JJ Cheng C Devidas M Cao X Fan Y Campana D Yang W Neale G Cox NJ Scheet P Borowitz MJ Winick NJ Martin PL Willman CL Bowman WP Camitta BM Carroll A Reaman GH Carroll WL Loh M Hunger SP Pui CH Evans WE Relling MV 《Nature genetics》2011,43(3):237-241
Although five-year survival rates for childhood acute lymphoblastic leukemia (ALL) are now over 80% in most industrialized countries, not all children have benefited equally from this progress. Ethnic differences in survival after childhood ALL have been reported in many clinical studies, with poorer survival observed among African Americans or those with Hispanic ethnicity when compared with European Americans or Asians. The causes of ethnic differences remain uncertain, although both genetic and non-genetic factors are likely important. Interrogating genome-wide germline SNP genotypes in an unselected large cohort of children with ALL, we observed that the component of genomic variation that co-segregated with Native American ancestry was associated with risk of relapse (P = 0.0029) even after adjusting for known prognostic factors (P = 0.017). Ancestry-related differences in relapse risk were abrogated by the addition of a single extra phase of chemotherapy, indicating that modifications to therapy can mitigate the ancestry-related risk of relapse. 相似文献
88.
89.
Albagha OM Wani SE Visconti MR Alonso N Goodman K Brandi ML Cundy T Chung PY Dargie R Devogelaer JP Falchetti A Fraser WD Gennari L Gianfrancesco F Hooper MJ Van Hul W Isaia G Nicholson GC Nuti R Papapoulos S Montes Jdel P Ratajczak T Rea SL Rendina D Gonzalez-Sarmiento R Di Stefano M Ward LC Walsh JP Ralston SH;Genetic Determinants of Paget's Disease 《Nature genetics》2011,43(7):685-689
Paget's disease of bone (PDB) is a common disorder characterized by focal abnormalities of bone remodeling. We previously identified variants at the CSF1, OPTN and TNFRSF11A loci as risk factors for PDB by genome-wide association study. Here we extended this study, identified three new loci and confirmed their association with PDB in 2,215 affected individuals (cases) and 4,370 controls from seven independent populations. The new associations were with rs5742915 within PML on 15q24 (odds ratio (OR) = 1.34, P = 1.6 × 10(-14)), rs10498635 within RIN3 on 14q32 (OR = 1.44, P = 2.55 × 10(-11)) and rs4294134 within NUP205 on 7q33 (OR = 1.45, P = 8.45 × 10(-10)). Our data also confirmed the association of TM7SF4 (rs2458413, OR = 1.40, P = 7.38 × 10(-17)) with PDB. These seven loci explained ~13% of the familial risk of PDB. These studies provide new insights into the genetic architecture and pathophysiology of PDB. 相似文献
90.
Bowman AB Lam YC Jafar-Nejad P Chen HK Richman R Samaco RC Fryer JD Kahle JJ Orr HT Zoghbi HY 《Nature genetics》2007,39(3):373-379
Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited neurodegenerative disease caused by expansion of a glutamine tract in ataxin-1 (ATXN1). SCA1 pathogenesis studies support a model in which the expanded glutamine tract causes toxicity by modulating the normal activities of ATXN1. To explore native interactions that modify the toxicity of ATXN1, we generated a targeted duplication of the mouse ataxin-1-like (Atxn1l, also known as Boat) locus, a highly conserved paralog of SCA1, and tested the role of this protein in SCA1 pathology. Using a knock-in mouse model of SCA1 that recapitulates the selective neurodegeneration seen in affected individuals, we found that elevated Atxn1l levels suppress neuropathology by displacing mutant Atxn1 from its native complex with Capicua (CIC). Our results provide genetic evidence that the selective neuropathology of SCA1 arises from modulation of a core functional activity of ATXN1, and they underscore the importance of studying the paralogs of genes mutated in neurodegenerative diseases to gain insight into mechanisms of pathogenesis. 相似文献