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   6399篇
  免费   1篇
电工技术   2篇
化学工业   29篇
能源动力   1篇
轻工业   16篇
石油天然气   3篇
无线电   3篇
一般工业技术   6篇
冶金工业   6332篇
自动化技术   8篇
  2019年   1篇
  2017年   2篇
  2013年   1篇
  2011年   1篇
  2010年   3篇
  2009年   2篇
  2008年   1篇
  2007年   4篇
  2006年   1篇
  2005年   4篇
  2004年   8篇
  2003年   3篇
  2002年   1篇
  2000年   1篇
  1999年   181篇
  1998年   2022篇
  1997年   1130篇
  1996年   726篇
  1995年   370篇
  1994年   327篇
  1993年   385篇
  1992年   41篇
  1991年   93篇
  1990年   68篇
  1989年   77篇
  1988年   76篇
  1987年   84篇
  1986年   72篇
  1985年   69篇
  1984年   3篇
  1983年   12篇
  1982年   34篇
  1981年   44篇
  1980年   38篇
  1979年   2篇
  1978年   17篇
  1977年   158篇
  1976年   317篇
  1975年   13篇
  1965年   1篇
  1955年   7篇
排序方式: 共有6400条查询结果,搜索用时 8 毫秒
11.
12.
13.
Medical nutrition therapy is essential for successful management in persons with diabetes. This article discusses implementation of the 1994 revised nutrition guidelines for persons with diabetes by the nonregistered dietitian professional, particularly in the nurse practitioner's setting. Major changes in the guidelines are addressed including the liberalization of sucrose, and basic nutrition assessment, referral guidelines, a sample nutrition history, and case studies to assist the nurse practitioner when a registered dietitian is unavailable.  相似文献   
14.
15.
16.
Tlg1p and Tlg2p, members of the syntaxin family of SNAREs in yeast, have been implicated in both endocytosis and the retention of late Golgi markers. We have investigated the functions of these and the other endocytic syntaxins Pep12p and Vam3p. Remarkably, growth is possible in the absence of all four proteins. In the absence of the others, Pep12p and Tlg1p can each create endosomes accessible to the endocytic tracer dye FM4-64. However, although Pep12p is required for the ligand-induced internalization of the alpha factor receptor and its passage via Pep12p-containing membranes to the vacuole, Tlg1p is not. In contrast, Tlg1p is required for the efficient localization of the catalytic subunit of chitin synthase III (Chs3p) to the bud neck, a process that involves endocytosis and polarized delivery of Chs3p. In wild-type cells, internalized Chs3p cofractionates with Tlg1p and Tlg2p, and in a strain lacking the other endocytic syntaxins, either Tlg1p or Tlg2p is sufficient for correct localization of the enzyme. Pep12p is neither necessary nor sufficient for this process. We conclude that there are two endocytic routes in yeast that can operate independently and that Tlg1p is located at the junction of one of these with the polarized exocytic pathway.  相似文献   
17.
DNA topoisomerase VI from the hyperthermophilic archaeon Sulfolobus shibatae is the prototype of a novel family of type II DNA topoisomerases that share little sequence similarity with other type II enzymes, including bacterial and eukaryal type II DNA topoisomerases and archaeal DNA gyrases. DNA topoisomerase VI relaxes both negatively and positively supercoiled DNA in the presence of ATP and has no DNA supercoiling activity. The native enzyme is a heterotetramer composed of two subunits, A and B, with apparent molecular masses of 47 and 60 kDa, respectively. Here wereport the overexpression in Escherichia coli and the purification of each subunit. The A subunit exhibits clusters of arginines encoded by rare codons in E.coli . The expression of this protein thus requires the co-expression of the minor E.coli arginyl tRNA which reads AGG and AGA codons. The A subunit expressed in E.coli was obtained from inclusion bodies after denaturation and renaturation. The B subunit was overexpressed in E.coli and purified in soluble form. When purified B subunit was added to the renatured A subunit, ATP-dependent relaxation and decatenation activities of the hyperthermophilic DNA topoisomerase were reconstituted. The reconstituted recombinant enzyme exhibits a specific activity similar to the enzyme purified from S.shibatae . It catalyzes transient double-strand cleavage of DNA and becomes covalently attached to the ends of the cleaved DNA. This cleavage is detected only in the presence of both subunits and in the presence of ATP or its non-hydrolyzable analog AMPPNP.  相似文献   
18.
19.
Well-differentiated thyroid cancer (i.e. papillary microcarcinoma) may be revealed by a clinically palpable cervical node, especially in young patients. Primary tumor specificity (small-sized, superior location, invasion, multifocality) and characteristics of cervical node involvement (with synchronous central and lateral multiple node spread) require appropriate treatment by a skilled surgeon. Contrary to the primary tumor treatment (total thyroidectomy), surgical management of the cervical node basins remains controversial. Only a special knowledge of the specificity of this disease and cervical lymphatic anatomy will ensure a good prognosis for the patient.  相似文献   
20.
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