首页 | 官方网站   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   65篇
  免费   1篇
工业技术   66篇
  2023年   1篇
  2021年   7篇
  2018年   4篇
  2017年   6篇
  2016年   1篇
  2015年   1篇
  2014年   4篇
  2013年   4篇
  2012年   2篇
  2011年   4篇
  2010年   3篇
  2009年   3篇
  2008年   4篇
  2007年   2篇
  2006年   1篇
  2005年   1篇
  2004年   1篇
  2002年   1篇
  2001年   1篇
  1999年   1篇
  1998年   1篇
  1996年   2篇
  1995年   1篇
  1992年   1篇
  1991年   3篇
  1990年   1篇
  1988年   1篇
  1987年   1篇
  1978年   2篇
  1976年   1篇
排序方式: 共有66条查询结果,搜索用时 0 毫秒
1.
Metalworking fluid (MWF) supplies a film of lubricant to abate friction, acts as a cooling media to rebate induced heat, and prevents metal pick-ups by flushing away the chips. Hence a liquid used as a cutting fluid reduces wear on the tool, reduces the energy consumption, and produces a better surface quality on the work piece. This paper describes the formulation of a novel water-soluble MWF and its performance evaluation during straight turning and end milling experiments carried out with AISI 304 stainless steel, mild steel, and cast iron as work piece materials. The MWF was prepared by mixing water with white coconut oil as the base oil and food-grade additives as surfactants. Viscosity, pH value, and biodegradability were measured and compared with a commercially available non-vegetable oil–based MWF. The surface roughness and tool surface temperature were measured throughout the machining experiments, and better performances were observed with the coconut oil–based MWF. Tool tip geometry and flank wear for straight turning machining operation were identified by observing scanning electron microscope (SEM) images.  相似文献   
2.
The selenol group of selenocysteine is much more nucleophilic than the thiol group of cysteine. Selenocysteine residues in proteins thus offer reactive points for rapid post-translational modification. Herein, we show that selenoproteins can be expressed in high yield and purity by cell-free protein synthesis by global substitution of cysteine by selenocysteine. Complete alkylation of solvent-exposed selenocysteine residues was achieved in 10 minutes with 4-chloromethylene dipicolinic acid (4Cl-MDPA) under conditions that left cysteine residues unchanged even after overnight incubation. GdIII−GdIII distances measured by double electron–electron resonance (DEER) experiments of maltose binding protein (MBP) containing two selenocysteine residues tagged with 4Cl-MDPA-GdIII were indistinguishable from GdIII−GdIII distances measured of MBP containing cysteine reacted with 4Br-MDPA tags.  相似文献   
3.
Abstract: The effects of red meat consumption with and without fermentable carbohydrates on indices of large bowel health in rats were examined. Sprague‐Dawley rats were fed cellulose, potato fiber, or potato‐resistant starch diets containing 12% casein for 2 wk, then similar diets containing 25% cooked beef for 6 wk. After week 8, cecal and colonic microbiota composition, fermentation end‐products, colon structure, and colonocyte DNA damage were analyzed. Rats fed potato fiber had lower Bacteroides‐Prevotella‐Porphyromonas group compared to other diet groups. Colonic Bifidobacterium spp. and/or Lactobacillus spp. were higher in potato fiber and potato‐resistant starch diets than in the cellulose diet. Beneficial changes were observed in short‐chain fatty acid concentrations (acetic, butyric, and propionic acids) in rats fed potato fiber compared with rats fed cellulose. Phenol and p‐cresol concentrations were lower in the cecum and colon of rats fed potato fiber. An increase in goblet cells per crypt and longer crypts were found in the colon of rats fed potato fiber and potato‐resistant starch diets. Fermentable carbohydrates had no effect on colonic DNA damage. Dietary combinations of red meat with potato fiber or potato‐resistant starch have distinctive effects in the large bowel. Future studies are essential to examine the efficacy of different types of nondigestible carbohydrates in maintaining colonic health during long‐term consumption of high‐protein diets. Practical Application: Improved understanding of interactions between the food consumed and gut microbiota provides knowledge needed to make healthier food choices for large bowel health. The impact of red meat on large bowel health may be ameliorated by consuming with fermentable dietary fiber, a colonic energy source that produces less harmful by‐products than the microbial breakdown of colonic protein for energy. Developing functional red meat products with fermentable dietary fiber could be one way to promote a healthy and balanced macronutrient diet.  相似文献   
4.
We report synthesis, characterization and ion transport in polyether-based ionic melt electrolytes consisting of Li salts of low-basicity anions covalently attached to polyether oligomers. Purity of the materials was investigated by HPLC analysis and electrospray ionization mass spectrometry. The highest ionic conductivity of 7.1 × 10−6 S/cm at 30 °C was obtained for the sample consisting of a lithium salt of an arylfluorosulfonimide anion attached to a polyether oligomer with an ethyleneoxide (EO) to lithium ratio of 12. The conductivity order of various ionic melts having different polyether chain lengths suggests that at higher EO:Li ratios the conductivity of the electrolytes at room temperature is determined in part by the amount of crystallization of the polyether portion of the ionic melt.  相似文献   
5.
Deterrence theory is one of the most widely applied theories in information systems (IS) security research, particularly within behavioral IS security studies. Based on the rational choice view of human behavior, the theory predicts that illicit behavior can be controlled by the threat of sanctions that are certain, severe, and swift. IS scholars have used deterrence theory to predict user behaviors that are either supportive or disruptive of IS security, and other IS security-related outcome variables. A review of this literature suggests an uneven and often contradictory picture regarding the influence of sanctions and deterrence theory in general in the IS security context. In this paper, we set out to make sense of the discrepant findings in the IS deterrence literature by drawing upon the more mature body of deterrence literature that spans multiple disciplines. In doing so, we speculate that a set of contingency variables and methodological and theoretical issues can shed light on the inconsistent findings and inform future research in this area. The review and analysis presented in this paper facilitates a deeper understanding of deterrence theory in the IS security domain, which can assist in cumulative theory-building efforts and advance security management strategies rooted in deterrence principles.  相似文献   
6.
Frequency of homozygous deletion at p16/CDKN2 in primary human tumours   总被引:1,自引:0,他引:1  
BACKGROUND: Carcinoma of the breast is characterized by a variable course with prognosis dependent on disease stage at presentation. Paradoxically, some patients with early malignancy demonstrate disease progression within a short time. The role of tumor markers in the management of carcinoma of the breast is controversial. While CA15-3 is the most widely used tumor marker in carcinoma of the breast, its role in the management of patients with early disease is controversial. STUDY DESIGN: Since 1986, all patients presenting to our unit with carcinoma of the breast have had serial CA15-3 levels measured. This study evaluates the role of serial CA15-3 levels in the management of a consecutive series of 168 patients with Stage I disease at presentation. RESULTS: The mean preoperative CA15-3 levels at presentation were significantly elevated in patients with Stage I disease compared with patients with benign disease. Sixteen patients had either locoregional (five patients) or metastatic recurrence (11 patients). CA15-3 levels were not elevated in patients with locoregional disease and were significantly elevated in patients with bony metastases and gave a mean lead time of 6.3 months over bone scintigraphy. CONCLUSIONS: Serial CA15-3 measurements are an efficient and cost-effective method of monitoring disease progression and have advantages over conventional investigations in patients with early carcinoma of the breast.  相似文献   
7.
The electrochemical behavior of tris(4-bromophenyl)amine (TBPA) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was comparatively studied in room temperature ionic liquids (RTILs) containing 1-butyl-3-methylimidazolium cation [BMIm]+ and the anions BF4, PF6and CF3SO3. TEMPO showed a well-defined electrochemical reversibility with anodic to cathodic peak current ratio (Ia/Ic) equals to unity in all RTILs, at a glassy carbon electrode. In contrast, Ia/Ic ratio greater than unity was observed at all scan rates employed (10-1000 mV s−1) in cyclic voltammograms (CV) of TBPA in RTILs. Controlled-potential bulk electrolysis of TBPA in RTILs yielded a dark blue colored solution of monocation TBPA+, which is stable under nitrogen. Diffusion coefficient of TBPA+ cation was determined in all three ILs by chronoamperometry and found to be at least one order of magnitude less than the calculated value of TBPA. This effect, in conjunction with the deviation of the Ia/Ic ratio from unity could be ascribed to ion-pairing interaction between the TBPA+ cation and the anion of the RTILs.  相似文献   
8.
This article evaluates the equity performance of bulk water allocation as an irrigation management strategy in the Mahaweli Ganga Development Project, Sri Lanka. Through semi-structured interviews with farmers and irrigation officials, the study collected local perceptions using seven indicators: water rights; decision-making process; contribution of resources for irrigation maintenance; water allocation rules; actual water distribution; information sharing; and conflict resolution. The results highlight gaps in the institution such as the need to enhance the water rights of landless farmers, further encourage crop diversification, increase transparency in decision making, instil a risk-management approach, and strengthen accountability.  相似文献   
9.
10.
This paper presents the design and implementation techniques employed in a Japanese-to-Sinhalese machine translation system. The main result of this work is the successful application of Bunsetsu in generating meaningful translations for a flexible-grammar language. The system has been developed considering the similarities between Japanese Bunsetsu and Sinhalese units. Such efforts are being focused on determining the minimum reasonable grammatical knowledge necessary for machine translation. The principal characteristics of the system, the translation process, problems encountered during the development stages, present status, and future plans will be discussed.  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-23

京公网安备 11010802026262号