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   308篇
  免费   29篇
  2021年   2篇
  2020年   4篇
  2019年   6篇
  2018年   7篇
  2017年   6篇
  2016年   11篇
  2015年   20篇
  2014年   15篇
  2013年   23篇
  2012年   12篇
  2011年   14篇
  2010年   14篇
  2009年   8篇
  2008年   9篇
  2007年   16篇
  2006年   13篇
  2005年   12篇
  2004年   15篇
  2003年   9篇
  2002年   11篇
  2001年   3篇
  2000年   9篇
  1999年   4篇
  1998年   4篇
  1997年   2篇
  1996年   3篇
  1995年   2篇
  1994年   4篇
  1993年   4篇
  1992年   3篇
  1991年   4篇
  1990年   4篇
  1988年   7篇
  1987年   11篇
  1986年   3篇
  1985年   4篇
  1984年   2篇
  1983年   4篇
  1982年   2篇
  1981年   3篇
  1977年   2篇
  1974年   3篇
  1973年   2篇
  1972年   2篇
  1970年   4篇
  1968年   1篇
  1967年   3篇
  1966年   2篇
  1965年   1篇
  1940年   1篇
排序方式: 共有337条查询结果,搜索用时 171 毫秒
231.
Heritage as a category reflects diverse political positions. All heritagisation processes imply the creation of hierarchies, selection, ranking, and categorisation of what is worthy or unworthy of being heritage, and all heritage creation involves certain disciplinary processes that confer legitimacy. As a modern invention, heritage was built on two closely related cornerstones: the distinction between nature and culture and the difference between normalised knowledge and marginal knowledge. As a result, refining processes were applied which became strategies to legitimise political domination. In this paper the constituent process of heritage creation and its links to normative knowledge are analysed, illustrating the various relationships between types of knowledge in the heritagisation process with the case of the Albufera Natural Park in Spain. A particular focus is placed on the processes that affect territories and natural resources, modifying the material conditions of the local population. Beyond giving rise to a mere acceptance of imposed expert knowledge, the analysed dynamics reveal the responsiveness of the local actors, as they make use of this knowledge in the context of a counter-hegemonic discourse.  相似文献   
232.
233.
A stable GS115 Pichia pastoris recombinant strain was constructed to secrete a truncated form of the human alpha(1,3/4) fucosyltransferase (amino acids 45-361). Enzyme production resulted from a secretory pathway based on the pre-pro- alpha mating factor signal sequence of the yeast Saccharomyces cerevisiae . Following its transit through the Golgi apparatus, the enzyme accumulated in the periplasmic space before its release in the culture broth (about 30 mg/l). Cell-enclosed enzyme ( approximately 0.16%) proved to be fairly stable for many freezing and thawing cycles and could be used several times as an immobilized catalyst. Soluble enzyme (>99.8%) representing the main protein of the culture broth (10%) has been characterized by Western-blotting, substrate specificities and kinetic parameters. The two forms (cell- enclosed and soluble) of recombinant enzyme may be used for in vitro synthesis of Lewisadeterminants.   相似文献   
234.
The equine embryonic capsule replaces the zona pellucida and envelops the conceptus during the second and third weeks of pregnancy. Although this capsule was described more than 100 years ago, its molecular structure has not been characterized. Here we present evidence that the glycoprotein(s) of the equine capsule resembles those of the mucin glycoprotein family. The resistance of the capsule to chemical and enzymatic solubilization was confirmed, and, as in mucins, protein constituted only 35–40% of its total dry mass. Determination of the sugar composition of the capsule using colorimetric assays and high-performance anion-exchange chromatography also showed it to have mucin-like characteristics. Gal, GalNAc, sulfated sugars, and sialic acid make up a high proportion of the capsular carbohydrate, while GlcNAc, Glc, and Man are minor components. These findings were verified using lectin histochemical staining of frozen sections of conceptuses. The results of amino acid analysis were also consistent with the proposal that the capsular glycoproteins belong to the mucin family. Removal of the covalently bound carbohydrate by b?-elimination under reducing conditions demonstrated that the capsule is O-glycosylated mainly on threonine residues. Affinity chromatography on jacalin-agarose confirmed that, like mucins, the capsular glycoproteins are heavily O-glycosylated. SDS-PAGE analysis revealed a prominent 21-kDa band, specific to the capsule, in preparations solubilized by trypsin but not by other proteases. Characterization of its constituent glycoprotein(s) should be helpful in elucidating the role of the capsule (and analogous blastocyst coverings in other species) during early pregnancy. © 1993 Wiley-Liss, Inc.  相似文献   
235.
At least six hydrolases of the human intestinal brush-border membrane bear ABH blood group antigenic determinants related to the erythrocyte phenotype: the intestinal glycoproteins of blood group A and B subjects express A or B determinants, respectively, while blood group O subjects express the H determinant identified with Ulex europaeus lectin I. These expressions are under the control of the secretor gene: ABH antigens were not detected in the hydrolases of non-secretor subjects.  相似文献   
236.
Two variants of recessive, H-deficient nonsecretor individuals (h/h, se/se) were identified on Reunion Island: (1) H-negative individuals corresponding to the classical Bombay phenotypes (OhO, OhA, OhB, OhAB) who lack completely the H antigen on their red cells; all of them were Indian and had strong anti-H antibodies reacting with normal O and Oh red cells from whites; and (2) H-weak individuals (Oh, Ah, Bh, ABh). This phenotype represented the majority (85%) of the H-deficient phenotypes on Reunion Island, and all of them were white. They had only a weak expression of the H antigen and showed small but detectable amounts of ABH antigens on their red cells. Their anti-H antibodies reacted with normal O erythrocytes, but failed to react with Oh red cells, regardless of the ethnic origin of the donor. They were all from the same geographical area on the Island (Cilaos) and showed homogeneous titers of anti-H antibodies in sera. We propose to call this particular variant of weak H phenotype, belonging to the so-called para-Bombay series, Reunion.  相似文献   
237.
238.
239.
240.
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