首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   41940篇
  免费   133篇
  国内免费   179篇
系统科学   258篇
丛书文集   706篇
教育与普及   66篇
理论与方法论   237篇
现状及发展   19485篇
研究方法   1710篇
综合类   19106篇
自然研究   684篇
  2013年   313篇
  2012年   625篇
  2011年   1246篇
  2010年   273篇
  2008年   696篇
  2007年   820篇
  2006年   798篇
  2005年   829篇
  2004年   915篇
  2003年   776篇
  2002年   846篇
  2001年   1260篇
  2000年   1127篇
  1999年   801篇
  1992年   728篇
  1991年   525篇
  1990年   592篇
  1989年   573篇
  1988年   532篇
  1987年   570篇
  1986年   644篇
  1985年   804篇
  1984年   584篇
  1983年   502篇
  1982年   462篇
  1981年   480篇
  1980年   561篇
  1979年   1303篇
  1978年   1075篇
  1977年   1041篇
  1976年   786篇
  1975年   862篇
  1974年   1256篇
  1973年   1042篇
  1972年   1126篇
  1971年   1231篇
  1970年   1644篇
  1969年   1290篇
  1968年   1155篇
  1967年   1242篇
  1966年   1091篇
  1965年   848篇
  1964年   275篇
  1959年   440篇
  1958年   806篇
  1957年   576篇
  1956年   432篇
  1955年   425篇
  1954年   476篇
  1948年   296篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Analysis of 78 Huntington's disease (HD) chromosomes with multi-allele markers revealed 26 different haplotypes, suggesting a variety of independent HD mutations. The most frequent haplotype, accounting for about one third of disease chromosomes, suggests that the disease gene is between D4S182 and D4S180. However, the paucity of an expected class of chromosomes that can be related to this major haplotype by assuming single crossovers may reflect the operation of other mechanisms in creating haplotype diversity. Some of these mechanisms sustain alternative scenarios that do not require a multiple mutational origin for HD and/or its positioning between D4S182 and D4S180.  相似文献   
82.
Both an ontoepistemology for reductionist modern science (counter-ontoepistemology) and an ontology for interpretive Systemology have been outlined in the two preceding papers in this special issue ofSystems Practice. In the present article, the notion of “truth” is interpreted in terms of both the ontoepistemology of “reductionism” and the ontology of interpretive systemology. Both interpretations are discussed. Such a discussion represents the objective of this paper, that is, to outline the epistemological “face” of the ontoepistemology of interpretive systemology. In order to design that “epistemological face,” the relation between ontology and epistemology must be clarified. Such a relation is seen from the standpoint already provided by the ontology. After the discussion on the notion of truth, the general shape of a systemic-interpretive inquiring process is outlined.  相似文献   
83.
84.
85.
86.
Progress on nuclear liquid gas phase transition (LGPT) or critical behavior has been simply reviewed and some signals of LGPT in heavy ion collisions, especially in NIMROD data, are focused. These signals include the power-law charge distribution, the largest fluctuation of the fragment observables, the nuclear Zipf law, caloric curve and critical exponent analysis etc.  相似文献   
87.
88.
Summary By means of intratracheal injection, particles of metalloid silicium about five microns in size are introduced into the lungs of guinea pigs, and the secondary parenchymatous reactions are studied from 10 minutes to 105 days. In the dust cells, the silicium is progressively broken up into very small particles of less than 1 micron in size. The cells do not show degeneration or mummification as the ordinary silica cells (Mavrogordato) do.  相似文献   
89.
90.
Summary All sensory endings of the trigeminal nerve in the dura mater of the rat are formed by a small swelling, from which continues themetaterminal apparatus, fine filaments at the limit of visibility. Periodically the fine granules at the extremity of the filaments swell, whereas the fibrils themselves disappear, leaving a small, round, argentophil mass. Later the filaments reappear, then redeposit their debris, which persists for a time.Thus the metaterminal apparatus manifests cyclic variations, which recall the transitory existence of collaterals observed duringin vivo orin vitro development of nerve fibres.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号