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   406篇
  免费   24篇
化学   347篇
晶体学   3篇
力学   4篇
数学   24篇
物理学   52篇
  2023年   4篇
  2022年   10篇
  2021年   8篇
  2020年   12篇
  2019年   12篇
  2018年   11篇
  2017年   11篇
  2016年   21篇
  2015年   20篇
  2014年   14篇
  2013年   21篇
  2012年   26篇
  2011年   26篇
  2010年   16篇
  2009年   10篇
  2008年   20篇
  2007年   14篇
  2006年   11篇
  2005年   13篇
  2004年   14篇
  2003年   6篇
  2002年   9篇
  2001年   7篇
  2000年   5篇
  1998年   3篇
  1997年   4篇
  1994年   3篇
  1993年   5篇
  1992年   4篇
  1991年   8篇
  1990年   3篇
  1987年   4篇
  1986年   5篇
  1985年   2篇
  1984年   2篇
  1980年   2篇
  1979年   6篇
  1977年   2篇
  1976年   3篇
  1975年   2篇
  1974年   4篇
  1973年   2篇
  1972年   4篇
  1969年   3篇
  1960年   23篇
  1926年   1篇
  1925年   2篇
  1924年   1篇
  1923年   1篇
  1915年   1篇
排序方式: 共有430条查询结果,搜索用时 281 毫秒
31.
32.
This study aimed to determine the effectiveness of photodynamic therapy (PDT), using δ‐aminolevulinic acid (5‐ALA), in the elimination of premalignant cervical lesions in Mexican patients with human papillomavirus (HPV) infection and/or cervical intraepithelial neoplasia (CIN). Thirty women diagnosed with CIN I and/or positive for HPV participated in the study. Topical 6% 5‐ALA in gel form was applied to the uterine cervix; after 4 h, the lesion area was irradiated with a light dose of 200 J cm?2 at 635 nm. This procedure was performed three times at 48‐h intervals. Clinical follow‐up was performed at 3, 6, and 12 months after the initial PDT administration, by colposcopy, cervical cytology, histopathological analysis, polymerase chain reaction, and hybrid capture. Of HPV‐infected patients without evidence of CIN I, 80% cleared the infection, while HPV associated with CIN I was eliminated in 83% of patients (P < 0.05). At 12 months, CIN I had regressed in 57% of patients, although this response was not statistically significant. PDT using 6% 5‐ALA is concluded to be effective in eliminating HPV infection associated or not with CIN I.  相似文献   
33.
Detlefsen (1986) reads Hilbert's program as a sophisticated defense of instrumentalism, but Feferman (1998) has it that Hilbert's program leaves significant ontological questions unanswered. One such question is of the reference of individual number terms. Hilbert's use of admittedly “meaningless” signs for numbers and formulae appears to impair his ability to establish the reference of mathematical terms and the content of mathematical propositions ( and ). The paper traces the history and context of Hilbert's reasoning about signs, which illuminates Hilbert's account of mathematical objectivity, axiomatics, idealization, and consistency.  相似文献   
34.
35.
36.
37.
The largest continuous bacterial nonribosomal peptide synthetase discovered so far is described. It consists of 15 consecutive modules arising from an uninterrupted, fully functional gene in the entomopathogenic bacterium Photorhabdus luminescens. The identification of its cryptic biosynthesis product was achieved by using a combination of genome analysis, promoter exchange, isotopic labeling experiments, and total synthesis of a focused collection of peptide candidates. Although it belongs to the growing class of D ‐/ L ‐peptide natural products, the encoded metabolite kolossin A was found to be largely devoid of antibiotic activity and is likely involved in interspecies communication. A stereoisomer of this peculiar natural product displayed high activity against Trypanosoma brucei rhodesiense, a recalcitrant parasite that causes the deadly disease African sleeping sickness.  相似文献   
38.
A contractile dendritic motional device is reported where metal ions with biological importance—Ca2+ (the main regulatory and signaling species of the natural muscles), Mg2+, and Zn2+—initiate two kinds of motional functions. The first motional function is the metal‐ion‐induced contraction of a linear strand into a Z‐shaped dinuclear complex, and the second one is the change of the height of Z‐shaped complexes via transmetalation. By means of the pH‐dependent counterligand tren, the two motional features of the machine can depend on alternate additions of acid and base. An optical response is associated with the conversion of the linear form (which is yellow) into the metalated Z‐shaped one (which is red).  相似文献   
39.
40.
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