全文获取类型
收费全文 | 151篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
系统科学 | 5篇 |
理论与方法论 | 2篇 |
现状及发展 | 51篇 |
研究方法 | 18篇 |
综合类 | 77篇 |
自然研究 | 1篇 |
出版年
2021年 | 1篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 2篇 |
2012年 | 8篇 |
2011年 | 16篇 |
2010年 | 6篇 |
2008年 | 7篇 |
2007年 | 15篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 10篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2000年 | 2篇 |
1996年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1969年 | 2篇 |
1968年 | 4篇 |
1967年 | 2篇 |
1945年 | 2篇 |
排序方式: 共有154条查询结果,搜索用时 31 毫秒
91.
Stuart PE Nair RP Ellinghaus E Ding J Tejasvi T Gudjonsson JE Li Y Weidinger S Eberlein B Gieger C Wichmann HE Kunz M Ike R Krueger GG Bowcock AM Mrowietz U Lim HW Voorhees JJ Abecasis GR Weichenthal M Franke A Rahman P Gladman DD Elder JT 《Nature genetics》2010,42(11):1000-1004
We carried out a meta-analysis of two recent psoriasis genome-wide association studies with a combined discovery sample of 1,831 affected individuals (cases) and 2,546 controls. One hundred and two loci selected based on P value rankings were followed up in a three-stage replication study including 4,064 cases and 4,685 controls from Michigan, Toronto, Newfoundland and Germany. In the combined meta-analysis, we identified three new susceptibility loci, including one at NOS2 (rs4795067, combined P = 4 × 10?11), one at FBXL19 (rs10782001, combined P = 9 × 10?1?) and one near PSMA6-NFKBIA (rs12586317, combined P = 2 × 10??). All three loci were also associated with psoriatic arthritis (rs4795067, combined P = 1 × 10??; rs10782001, combined P = 4 × 10??; and rs12586317, combined P = 6 × 1??) and purely cutaneous psoriasis (rs4795067, combined P = 1 × 10??; rs10782001, combined P = 2 × 10??; and rs12586317, combined P = 1 × 10??). We also replicated a recently identified association signal near RNF114 (rs495337, combined P = 2 × 10??). 相似文献
92.
Future steam turbines will use hollow structures so that the turbine inlet temperature can be in- creased to improve the thermal efficiency. These hollow structures are made of the nickel-base alloy Nicro- fer 6025 HT and consist of a wire mesh between two cover sheets. The cover sheets can be joined to the wire mesh by capacitor discharge welding due to its extremely short welding duration. The goal of this re- search is to investigate suitable welding parameters so that the weld spots form in an optimum way to in- crease the tensile shear strength and reduce spattering. Tensile shear tests, three-point bending tests, and micrographs were used to judge the joint quality of structures made with various welding parameters. The results show that the best welds are obtained with a transmission ratio of 1:200, welding energy of 70% to 95%, and electrode force of 7 to 9 MPa. 相似文献
93.
Unexpected complexity of the Wnt gene family in a sea anemone 总被引:1,自引:0,他引:1
Kusserow A Pang K Sturm C Hrouda M Lentfer J Schmidt HA Technau U von Haeseler A Hobmayer B Martindale MQ Holstein TW 《Nature》2005,433(7022):156-160
The Wnt gene family encodes secreted signalling molecules that control cell fate in animal development and human diseases. Despite its significance, the evolution of this metazoan-specific protein family is unclear. In vertebrates, twelve Wnt subfamilies were defined, of which only six have counterparts in Ecdysozoa (for example, Drosophila and Caenorhabditis). Here, we report the isolation of twelve Wnt genes from the sea anemone Nematostella vectensis, a species representing the basal group within cnidarians. Cnidarians are diploblastic animals and the sister-group to bilaterian metazoans. Phylogenetic analyses of N. vectensis Wnt genes reveal a thus far unpredicted ancestral diversity within the Wnt family. Cnidarians and bilaterians have at least eleven of the twelve known Wnt gene subfamilies in common; five subfamilies appear to be lost in the protostome lineage. Expression patterns of Wnt genes during N. vectensis embryogenesis indicate distinct roles of Wnts in gastrulation, resulting in serial overlapping expression domains along the primary axis of the planula larva. This unexpectedly complex inventory of Wnt family signalling factors evolved in early multi-cellular animals about 650 million years (Myr) ago, predating the Cambrian explosion by at least 100 Myr (refs 5, 8). It emphasizes the crucial function of Wnt genes in the diversification of eumetazoan body plans. 相似文献
94.
Yan Ma Rui Zheng Ziyuan Gao Ulrich Krupp Hai-wen Luo Wenwen Song Wolfgang Bleck 《矿物冶金与材料学报》2021,28(5):847-853
Medium-Mn steels have attracted immense attention for automotive applications owing to their outstanding combination of high strength and superior ductility. This steel class is generally characterized by an ultrafine-grained duplex microstructure consisting of ferrite and a large amount of austenite. Such a unique microstructure is processed by intercritical annealing, where austenite reversion occurs in a fine martensitic matrix. In the present study, austenite reversion in a medium-Mn alloy was simulated by the multiphase-field approach using the commercial software MICRESS? coupled with the thermodynamic database TCFE8 and the kinetic database MOBFE2. In particular, a faceted anisotropy model was incorporated to replicate the lamellar morphology of reversed austenite. The simulated microstructural morphology and phase transformation kinetics (indicated by the amount of phase) concurred well with experimental observations by scanning electron microscopy and in situ synchrotron high-energy X-ray diffraction, respectively. 相似文献
95.
96.
Steidl C Shah SP Woolcock BW Rui L Kawahara M Farinha P Johnson NA Zhao Y Telenius A Neriah SB McPherson A Meissner B Okoye UC Diepstra A van den Berg A Sun M Leung G Jones SJ Connors JM Huntsman DG Savage KJ Rimsza LM Horsman DE Staudt LM Steidl U Marra MA Gascoyne RD 《Nature》2011,471(7338):377-381
97.
98.
99.
100.
Werner Ulrich 《Systemic Practice and Action Research》1993,6(6):583-611
We probably have simplified matters too much. We tend to talk about systems thinking and practice as if we knew what they are. The fashionable call for “holistic” or “systems” thinking in ecological issues provides a major example. This much is certain: the quest for comprehensiveness, although it represents an epistemologically necessary idea, is not realizable. If we assume that it is realizable, the critical idea underlying the quest will be perverted into its opposite, i.e., into a false pretension to superior knowledge and understanding—a danger of which the environmental movement does not always appear to be sufficiently aware. My question, therefore, is this: How can we deal critically with the fact that our thinking, and hence our knowledge, designs, and actions, cannot possibly be comprehensive, in the sense that we never “comprehend” all that ought to be understood before we pass to judgment and action? What consequences does this fact imply for a critical systems approach to ecological concerns and, ultimately, for our concepts of rationality in general? 相似文献