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Sir Gavin de Beer D.Sc. Hon. D.-ès-L. F.R.S. 《Annals of science》2013,70(3):189-223
It is argued that Hugo de Vries's conversion to Mendelism did not agree with his previous theoretical framework. De Vries regarded the number of offspring expressing a certain character as a hereditary quality, intrinsic to the state of the pangene involved. His was a shortlived conversion since after the ‘rediscovery’ he failed to unify his older views with Mendelism. De Vries was never very much of a Mendelian. The usual stories of the Dutch ‘rediscovery’ need, therefore, a considerable reshaping. 相似文献
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Giora Hon Bernard R. Goldstein 《Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics》2012,43(4):236-257
The term “analogy” stands for a variety of methodological practices all related in one way or another to the idea of proportionality. We claim that in his first substantial contribution to electromagnetism James Clerk Maxwell developed a methodology of analogy which was completely new at the time or, to borrow John North’s expression, Maxwell’s methodology was a “newly contrived analogue”. In his initial response to Michael Faraday’s experimental researches in electromagnetism, Maxwell did not seek an analogy with some physical system in a domain different from electromagnetism as advocated by William Thomson; rather, he constructed an entirely artificial one to suit his needs. Following North, we claim that the modification which Maxwell introduced to the methodology of analogy has not been properly appreciated. In view of our examination of the evidence, we argue that Maxwell gave a new meaning to analogy; in fact, it comes close to modeling in current usage. 相似文献
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增值税按扣税对象的不同,可分为生产型、收入型和消费型增值税。在1994年税制改革中根据我国实际我们选择实行生产型增值税,但在以后的经济运行中,生产型增值税的弊端日益显现,阻碍了经济的发展。因此由生产型增值税向消费型增值税转变在当前显得尤为重要。 相似文献
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Zang ZJ Cutcutache I Poon SL Zhang SL McPherson JR Tao J Rajasegaran V Heng HL Deng N Gan A Lim KH Ong CK Huang D Chin SY Tan IB Ng CC Yu W Wu Y Lee M Wu J Poh D Wan WK Rha SY So J Salto-Tellez M Yeoh KG Wong WK Zhu YJ Futreal PA Pang B Ruan Y Hillmer AM Bertrand D Nagarajan N Rozen S Teh BT Tan P 《Nature genetics》2012,44(5):570-574
Gastric cancer is a major cause of global cancer mortality. We surveyed the spectrum of somatic alterations in gastric cancer by sequencing the exomes of 15 gastric adenocarcinomas and their matched normal DNAs. Frequently mutated genes in the adenocarcinomas included TP53 (11/15 tumors), PIK3CA (3/15) and ARID1A (3/15). Cell adhesion was the most enriched biological pathway among the frequently mutated genes. A prevalence screening confirmed mutations in FAT4, a cadherin family gene, in 5% of gastric cancers (6/110) and FAT4 genomic deletions in 4% (3/83) of gastric tumors. Frequent mutations in chromatin remodeling genes (ARID1A, MLL3 and MLL) also occurred in 47% of the gastric cancers. We detected ARID1A mutations in 8% of tumors (9/110), which were associated with concurrent PIK3CA mutations and microsatellite instability. In functional assays, we observed both FAT4 and ARID1A to exert tumor-suppressor activity. Somatic inactivation of FAT4 and ARID1A may thus be key tumorigenic events in a subset of gastric cancers. 相似文献
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According to the received view, the first spyglass was assembled without any theory of how the instrument magnifies. Galileo,
who was the first to use the device as a scientific instrument, improved the power of magnification up to 30 times. How did
he accomplish this feat? Galileo does not tell us what he did. We hold that such improvement of magnification is too intricate
a problem to be solved by trial and error, accidentally stumbling upon a complex procedure. We construct a plausibility argument
and submit that Galileo had a theory of the telescope. He could develop it by analogical reasoning based on the phenomenon
of reflection in mirrors—as it was put to use in surveying instruments—and applied to refraction in sets of lenses. Galileo
could appeal to this analogy and assume Della Porta’s theory of refraction. He could thus turn the spyglass into a revolutionary
scientific instrument—the telescope. 相似文献
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设G是连通图,X=V(G),G〔X〕是G的X生成子图,记σk(X)=min{Σi=1 k d(Vi);{v1,v2,…,vk}是G〔X〕的顶点独立集},得到如下结果,对于n阶的1-坚韧图(n≥3),X=V(G),且σ3(X)≥n+r≥n,3│X│-2n≥8t-6r-17,则存在一个圈C满足│C(X)│≥{C(X)│≥{│X│,│N(It)∩V(C)│},其中It是X中t个顶点的独立集。 相似文献