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   332篇
  免费   4篇
电工技术   7篇
化学工业   59篇
金属工艺   3篇
建筑科学   7篇
能源动力   2篇
轻工业   33篇
无线电   46篇
一般工业技术   37篇
冶金工业   64篇
原子能技术   18篇
自动化技术   60篇
  2022年   3篇
  2021年   2篇
  2019年   4篇
  2018年   4篇
  2017年   5篇
  2016年   6篇
  2015年   2篇
  2014年   8篇
  2013年   13篇
  2012年   11篇
  2011年   7篇
  2010年   16篇
  2009年   9篇
  2008年   10篇
  2007年   9篇
  2006年   12篇
  2005年   10篇
  2004年   10篇
  2003年   7篇
  2002年   11篇
  2001年   11篇
  2000年   8篇
  1999年   6篇
  1998年   33篇
  1997年   16篇
  1996年   13篇
  1995年   8篇
  1994年   8篇
  1993年   12篇
  1992年   7篇
  1991年   2篇
  1990年   5篇
  1989年   3篇
  1988年   3篇
  1987年   2篇
  1986年   4篇
  1985年   3篇
  1984年   3篇
  1983年   1篇
  1982年   2篇
  1981年   4篇
  1980年   3篇
  1979年   1篇
  1978年   1篇
  1977年   3篇
  1976年   6篇
  1974年   1篇
  1973年   4篇
  1972年   1篇
  1970年   2篇
排序方式: 共有336条查询结果,搜索用时 15 毫秒
51.
52.
BACKGROUND: Surgical management of ductal carcinoma in situ (DCIS) has been a controversial issue in the selection of breast-conserving surgery as a method of treatment. The definition of intraductal spreading of carcinoma becomes an important factor in the decision making process, but little is known about how much intraductal extension influences the spreading of tumor in the whole breast. To define any unfavorable pathologic factors existing in limited surgery for patients with DCIS, the authors investigated histopathologic characteristics using a sequential slicing of tissues. METHODS: Duct-lobular segmentectomy, a limited surgery, was performed on 110 patients with a bloody nipple discharge. Six patients with invasive carcinoma and 17 patients with DCIS subsequently received a total mastectomy. The specimens obtained by segmentectomy and mastectomy were histopathologically examined. Using subserial sections, the authors examined the relationship between intraductal spreading of carcinoma in the segmentectomy specimens and carcinoma residue in the mastectomy specimens. RESULTS: Among 16 mastectomy specimens, the authors found residual DCIS in 6, and atypical ductal hyperplasia in 4. Intraductal spreading of carcinoma was detected in 8 of 16 segmentectomy specimens. Six of eight patients with intraductal spreading had residual DCIS. The other two patients had atypical hyperplasia in breasts. No residual DCIS was detected in the other eight patients without intraductal spreading. Among 12 patients under observation who did not have a mastectomy, invasive carcinoma subsequently developed in 3. Two of three patients had intraductal spreading in segmentectomy specimens. Only 1 of 10 patients without intraductal spreading, however, developed carcinoma. CONCLUSIONS: Intraductal spreading of carcinoma is an unfavorable pathologic factor in breast-conserving surgery for patients with ductal carcinoma in situ with nipple discharge.  相似文献   
53.
Large-scale integrated (LSI) memory circuit reliability is reviewed. Reliability of large-scale integrated memory circuits is discussed. The major physical mechanisms for failures in memory LSIs and measures to counter these failures are reviewed. Fault-tolerant techniques, divided into the spare row/column line substitution. (SLS) technique and the on-chip error-correcting code (ECC) technique, developed to overcome hard and soft failures are described. Design approaches for realizing high performance and high reliability are also discussed  相似文献   
54.
The template effect plays important roles not only in modern synthetic and enzymatic catalysis but also in the ancient “RNA‐polypeptide (RNP) world,” which has been postulated to be a crucial stage in the origin of life. To mimic primitive template catalysis of peptide ligations by RNAs, we previously reported the design and synthesis of a ternary RNP complex in which the ligation of two peptides was significantly facilitated by a template RNA with two peptide‐binding units. However, RNA molecules also promoted the ligation reaction in a nonspecific manner through electrostatic interactions between RNA and basic peptides. In this study, we suppressed this effect by reducing the length of the original template derived from the Tetrahymena intron RNA. This modification, however, decreased the template ability for the specific reaction. As an alternative RNA that was as effective as the original template, we found that a self‐dimerizing RNA was a promising template for peptide ligation without a nonspecific effect.  相似文献   
55.
Multimedia Tools and Applications - Cost-volume filtering (CVF) is one of the most widely used techniques for solving general multi-labeling problems based on a Markov random field (MRF). However...  相似文献   
56.
The effects of aging and moisture on the dynamic viscoelastic properties of three oriental lacquer films were investigated. With aging over 1000 days at room temperature, the glass‐transition temperature of the lacquer films (Tα) shifted to higher temperatures, the maximum loss tangent (tanδα) decreased, and the storage modulus at 20°C (E) increased. These changes were analogous irrespective of lacquers. With increasing moisture content, E decreased and tanδ increased at room temperature. Although the equilibrium moisture content of the virgin lacquer (sap) film was higher than that of the clear lacquer film, its E and tanδ were more stable with an increase of moisture content. It was speculated that the polysaccharides aggregated in the sap film did not effectively contribute to the mechanical properties of the film, while their hygroscopicity resulted in higher moisture content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2288–2294, 2002  相似文献   
57.
Group I (GI) self‐splicing ribozymes are attractive tools for biotechnology and synthetic biology. Several trans‐splicing and related reactions based on GI ribozymes have been developed for the purpose of recombining their target mRNA sequences. By combining trans‐splicing systems with rational modular engineering of GI ribozymes it was possible to achieve more complex editing of target RNA sequences. In this study we have developed a cooperative trans‐splicing system through rational modular engineering with use of dimeric GI ribozymes derived from the Tetrahymena group I intron ribozyme. The resulting pairs of ribozymes exhibited catalytic activity depending on their selective dimerization. Rational modular redesign as performed in this study would facilitate the development of sophisticated regulation of double or multiple trans‐splicing reactions in a cooperative manner.  相似文献   
58.
2-Alkylcyclobutanones, such as 2-dodecylcyclobutanone and 2-tetradecylcyclobutanone, were analyzed to assess the irradiation history of irradiated meats or fish, and cooked foods with irradiated ingredients, which had been stored frozen for up to one year. The purpose of the study was to show that irradiated meats could be detected even after having been stored in the distribution system. 2-Alkylcyclobutanones showed a small decrease in irradiated raw meats that had been stored frozen for one year. Cooked foods, such as pancake and fried chicken made with irradiated eggs and chicken, respectively, contained detectable levels of 2-alkylcyclobutanones after storage frozen for one year. The 2-alkylcyclobutanones became undetectable in highly dried samples, such as feed for lab animals, during the same period.  相似文献   
59.
It has been found that ion implantation can induce a swelling (step-height) phenomenon on crystal surface. In this paper, we studied about the control of swelling height of Si crystal by irradiating Ar beam under various parameters (fluence, charge and energy). These irradiation parameters were regulated by an irradiation facility that enables to achieve the multiple ionization. For both charges, the swelling height was studied with the various fluencies of two different charges Ar(1+) and Ar(4+). The swelling height increased with increasing the fluence. The swelling height was also studied by changing energy of Ar(4+) beam. The swelling height increased by increasing the energy. The obtained swelling heights are understood base on the contribution of ion-beam induced defect, which is evaluated by SRIM. By comparing with the previous results, it was found that the expansion phenomena also depend on irradiated ion. The swelling structures were found to be stable more than two months. The present results have shown that this method of producing swelling structure indicates the potential application to fabricate 3-D nanostructure.  相似文献   
60.
A highly geometry‐selective organocatalytic acylation of tri‐ and tetra‐substituted 2‐alkylidene‐1,3‐propanediols has been developed. The highly E‐selective acylation of various tetrasubstituted 2‐alkylidene‐1,3‐propanediols was achieved in 96 to >99% selectivity for the first time by a non‐enzymatic protocol.  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