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   729篇
  免费   74篇
电工技术   5篇
综合类   2篇
化学工业   263篇
金属工艺   9篇
机械仪表   2篇
建筑科学   50篇
矿业工程   4篇
能源动力   9篇
轻工业   146篇
水利工程   13篇
无线电   37篇
一般工业技术   84篇
冶金工业   119篇
原子能技术   2篇
自动化技术   58篇
  2024年   5篇
  2023年   10篇
  2022年   38篇
  2021年   60篇
  2020年   28篇
  2019年   29篇
  2018年   28篇
  2017年   18篇
  2016年   24篇
  2015年   33篇
  2014年   26篇
  2013年   54篇
  2012年   40篇
  2011年   43篇
  2010年   33篇
  2009年   34篇
  2008年   36篇
  2007年   28篇
  2006年   20篇
  2005年   32篇
  2004年   17篇
  2003年   16篇
  2002年   17篇
  2001年   6篇
  2000年   7篇
  1999年   9篇
  1998年   16篇
  1997年   8篇
  1996年   11篇
  1995年   7篇
  1994年   5篇
  1993年   7篇
  1992年   6篇
  1991年   4篇
  1990年   5篇
  1989年   6篇
  1988年   4篇
  1985年   3篇
  1983年   5篇
  1981年   2篇
  1978年   2篇
  1977年   3篇
  1976年   2篇
  1975年   2篇
  1974年   2篇
  1973年   2篇
  1968年   1篇
  1967年   1篇
  1964年   2篇
  1945年   1篇
排序方式: 共有803条查询结果,搜索用时 234 毫秒
261.
1. Arginine-hydrochloride and ornithine-aspartate solutions have been infused intravenously to children of two families. Three children of the WOL. family are affected with hyperargininemia and hyperammonemia, due to a lack of arginase. They present a secondary cystine-lysinuria. The three WIL. siblings are suffering from muscular hypotonia, dwarfism, incomplete renal tubular acidosis and primary cystinuria. 2. The aim was to verify how and to what extent the artificial rise of one serum amino acid could influence the serum concentrations and the urinary losses of the other amino acids. The results found for the serum have been submitted to a statistical analysis of variance. 3. The variations observed for the amino acids of the urea cycle can be interpreted as being the reflections of known metabolic pathways. 4. Additional remarks are made on a paradox in the lysinemia-lysinuria relation after arginine infusion, with a simultaneous rise of this essential amino acid in serum and urine.  相似文献   
262.
Studied the perceptions of empathy among 12 clients, 12 counselors, 12 observers, and 2 judges on the empathy subscale of the Truax Relationship Inventory and on R. R. Carkhuff's (1969) empathy rating scale. Psychology graduate students served as counselor Ss; all other Ss were undergraduates. Results indicate strong agreement among all participants of the counseling process on their perceptions of empathy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
263.
Six derivatives with increased resistance to ox gall (MIC: > or = 1% w/v) and one derivative resistant to sodium cholate (MIC: 0.8% w/v) were obtained from more sensitive original Bifidobacterium strains. These microorganisms, and two additional cholate resistant derivatives obtained in a previous study (Int. J. Food Microbiol. 82 (2003) 191), were partially characterised in this study. Acquisition of resistance against a given bile salt, also conferred cross-resistance to other bile salts, and promoted an increase in the survival of these microorganisms at low pH. Bile resistance levels of derivatives were dependent on the external pH so that the resistance was lower at neutral pH values than in acidic environments. In addition, the acquisition of bile resistance induced changes on glycoside-hydrolysing activities of derivatives obtained from five out of eight original strains, with certain activities such as beta-glucosidase showing more than tenfold increases in some of these microorganisms. These data suggest that the exposure to high bile salts concentrations may have induced a synergic response on Bifidobacterium for the adaptation to the conditions of the gastrointestinal tract. This could have improved the survival at low pH in these microorganisms, the resistance to high bile salts concentrations, and the assimilation of non-digestible carbohydrates by the enhancement of some glycoside-hydrolysing activities.  相似文献   
264.
Walnut tannins were maximally extracted with absolute methanol and an extraction time of 60 min. Storage (21 days at 25 °C) significantly reduced (20–40% reduction) the assayable tannin content in walnuts. The ranges of tannin content in freshly cracked inshell and shelled walnuts were respectively 372–1095 and 363–667 mg catechin equivalent per 100 g dry weight. The assayable tannin content in inshell and shelled walnuts was 10–20% higher when the particle size was reduced from 2‐ to 8‐mesh. Using 0.5 as compared to 2% (w/v) vanillin as colour development reagent yielded 15–20% higher assayable tannin contents. The assay colour development reached a maximum after 20 min of incubation at 25 °C. Roasting (204 °C for 5 min) caused a small (14%) but significant reduction in assayable tannins. Soaking in aqueous alkali solutions was more effective (44–100% reduction) than soaking in aqueous acid solutions (6–76% reduction) in decreasing the assayable tannin content in walnuts. Microwave heating in distilled deionised water resulted in 93–98% reduction in walnut assayable tannins. Blanching at 100 °C for 2 min was as effective as alkali soaking in significantly reducing the amount of extractable walnut tannins (98% reduction). The tannin content in blanched walnuts was positively related to astringency scores (r = 0.92). © 2001 Society of Chemical Industry  相似文献   
265.
The authors disagree with A. E. Kelly's (see record 2000-08364-001) conclusions that clients conceal things from therapists primarily for self-presentational reasons and that client concealment is positively related to positive therapy process and outcome. They also disagree with A. E. Kelly regarding the implications of self-presentation theory for therapy. Their review of the research suggests that clients do not conceal much from therapists, that what they do conceal involves many different kinds of information hidden for many different reasons, that therapists have wide variability in being able to detect hidden client material, and that the relationship of client concealment and therapist awareness of client concealment with therapy process and outcome is not clear. Finally, the authors discuss their views about implications of client concealment and self-presentation for therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
266.
267.
268.
Nephronophthisis (NPHP) is a pediatric form of hereditary polycystic kidney disease (PKD), and is the leading cause of end stage renal disease in children. The pcy mouse is an orthologous model of human NPHP, with a mutation in the Nphp3 gene. Renal phospholipase A2, cyclooxygenase (COX) 1 and cyclic AMP are elevated in this model, suggesting that eicosanoid formation may be altered. In another type of PKD observed in the Han:SPRD-Cy rat, inhibition of eicosanoid production slows disease progression. If renal eicosanoids are similarly altered in NPHP, potential for pharmacologic intervention also may exist for this disorder. Therefore, renal fatty acids and eicosanoids were determined in pcy and normal mice at 15, 30 and 60 days of age by gas chromatography and HPLC–tandem mass spectrometry, respectively. Renal cysts in enlarged kidneys were observed in pcy mice by 15 days of age and increased over time. Renal phospholipid ARA levels were higher in pcy compared to normal mice at 15 and 30 days. Eicosanoid differences were observed starting at 30 days, when the COX products 6-keto-prostaglandin (PG) F, thromboxane B2 and PGE2 were higher in pcy compared to normal kidneys. Overall, total COX products were elevated at 30 and 60 days. In contrast, the levels of the lipoxygenase (LOX) products were not altered until 60 days of age and these were lower in pcy kidneys compared to normal. These findings suggest that altered eicosanoids play a role in NPHP, and that manipulating these levels with pharmacologic agents may have therapeutic potential.  相似文献   
269.
Three-dimensional (3-D) photonic crystals (PCs) have been studied as possible strain sensing materials, based on strain-induced stop band frequency shifting. Self-assembly of polystyrene microspheres, achieved by sedimentation over a flexible polyimide tape substrate whose surface hydrophilicity was optimized in order to achieve maximum wettability, led to an organized 3-D direct opal template. This was infiltrated with a silica sol-gel solution by dip-coating or by chemical vapour deposition and an inverse opal structure was ultimately obtained by chemical dissolution of the polymer template. The structural and optical properties of these PCs have been studied by scanning electron microscopy (FE-SEM) and UV/visible spectroscopy under variable degrees of strain. FE-SEM showed the presence of ordered domains up to ∼30 μm2. A mechano-optical effect was evidenced by strain-induced shifting of the photonic stop band peak wavelength of the direct, infiltrated and inverse opals up to 50 nm in transmission mode, due to changes in interplanar spacing upon bending the flexible PCs. Optical response strain cycles were studied, suggesting the possible use of these structures in reversible photonic strain sensors integrated in sensor/actuator devices.  相似文献   
270.
Drying is one of the most cost-effective methods of worthwhile by-product valorisation. This study had two main objectives. The first was to determine the effect of hot air drying (HAD) combined with microwave (MW) irradiation on the treatment kinetics and the macrostructural and microstructural properties of the dried product. The second aim was to develop engineering tools to predict the extent of dehydration. Drying was performed using hot air at 55 °C and the combined (HAD?+?MW) treatment at different power intensities (2, 4, and 6 W/g). After 5, 15, 40, 60, and 120 min, the mass, surface, volume, water activity and moisture were measured in fresh and dried samples. Sorption isotherms were obtained and fitted to the GAB model, with high correlation coefficients. The macroscopic and microscopic analyses showed shrinkage and swelling in the peel tissue caused by the MW treatment. The HAD?+?MW methods not only resulted in increased moisture reduction but also induced microstructural changes that generated higher sorption capacity.  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