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   109篇
  免费   2篇
电工技术   2篇
化学工业   12篇
金属工艺   1篇
机械仪表   1篇
建筑科学   3篇
轻工业   29篇
石油天然气   1篇
无线电   12篇
一般工业技术   6篇
冶金工业   38篇
自动化技术   6篇
  2019年   1篇
  2018年   3篇
  2017年   3篇
  2014年   2篇
  2013年   1篇
  2012年   4篇
  2011年   6篇
  2010年   1篇
  2009年   4篇
  2008年   6篇
  2007年   6篇
  2006年   4篇
  2005年   2篇
  2004年   1篇
  2003年   3篇
  2002年   2篇
  2001年   1篇
  2000年   1篇
  1999年   2篇
  1998年   10篇
  1997年   11篇
  1996年   10篇
  1995年   4篇
  1994年   4篇
  1993年   4篇
  1992年   1篇
  1990年   2篇
  1984年   1篇
  1982年   1篇
  1981年   1篇
  1979年   4篇
  1977年   1篇
  1976年   2篇
  1975年   1篇
  1974年   1篇
排序方式: 共有111条查询结果,搜索用时 15 毫秒
91.
The aim of this research was to compare the occurrence of patulin in a large group of organic, conventional, and handcrafted apple juices marketed in Belgium. An analytical procedure based on high-performance liquid chromatography with UV detection was validated and used to analyze 177 apple juice samples: 65 organic, 90 conventional, and 22 handcrafted. Patulin was detected in 22 samples (12%), and quantification was possible in 10 (6%) of these samples. The patulin content was higher than the European legal limit of 50 microg/liter in two samples of organic apple juice. Although, the incidence of patulin in organic (12%), conventional (13%), and handcrafted (10%) apple juices was not significantly different (P = 0.863), the mean concentration of patulin in contaminated samples was significantly higher in organic (43.1 microg/liter) than in conventional (10.2 microg/liter) (P = 0.02) and handcrafted (10.5 microg/liter) (P = 0.037) apple juice. The highest patulin concentrations were found in the most expensive apple juices because of the higher price of organic apple juice. This relation was not observed when only conventional apple juices were analyzed.  相似文献   
92.
Last summer, within the pages of this journal, an essay described the uncertainty surrounding the future of our small but independent VNA ("Dissolution of Tradition into Fantasy: A Lament," May/June, 1996). Supposedly, harsh financial pressures bombarded us and our Board began an inexorable movement toward affiliation with a powerful local hospital. When professional staff became jittery, Board representatives soothed us. This anxious period, given the decidedly unromantic coinage "due diligence," was likened to a courtship phase, an arranged engagement of sorts. Cold feet, second thoughts, panic attacks, and troubled dreams--all were to be expected, considered perfectly natural. All would be forgotten in the bliss of connubial union. Be patient and trust, we were advised; the consummation would make it all worthwhile. And we tried. What has transpired between last summer and this spring, however, exceeded our most vivid nightmare. Betrayed and angry, we scrambled to save what we could of our VNA before it was consigned to obsolescence in this, the year of our centennial.  相似文献   
93.
A comparative study examining Bolton broth and Preston broth for enrichment and reliable detection of Campylobacter jejuni (both healthy and freeze stressed cells) was performed. Tested as pure cultures, Bolton broth enabled faster resuscitation and growth of C. jejuni compared to Preston broth. When C. jejuni was co-incubated with extended-spectrum-beta-lactamase (ESBL) producing Escherichia coli isolated from Belgian poultry meat preparations, the latter dominated in the Bolton enrichment broth and crowded the mCCDA plates. This resulted in the inability to recover C. jejuni by ISO 10272-1:2006 standard method. Preston broth did not support the growth of the ESBL E. coli isolates, but showed longer detection time of C. jejuni compared to Bolton broth. The use of the same antibiotic (sodium cefoperazone) in Bolton broth and in mCCDA plates may explain the problems encountered for detection of C. jejuni, as high numbers of ESBL E. coli present after enrichment in Bolton broth, also caused overgrowth and masked the few C. jejuni colonies present on the mCCDA plates. The use of Campylobacter spp. specific real-time PCR circumvented these problems and enabled rapid detection of the pathogen after 24 h enrichment in both Bolton and Preston broth, for both healthy and freeze stressed cells.  相似文献   
94.
The aim of this study was to determine whether the intrarenal resistive index (RI) can be used for the diagnosis of acute obstruction in patients with renal colic and to determine whether the index is time-related. Seventy patients referred to the Emergency Department with acute renal colic and without known associated renal disease underwent duplex Doppler ultrasonography to determine the intrarenal RI at the symptomatic and asymptomatic side. The age range of the patients was 18-72 years. An RI greater than 0.68 and/or an interrenal difference in RI greater than 0.06 and/or an increase in RI of more than 11% compared with the normal side proved reliable cut-off values to diagnose acute renal obstruction. In addition, time dependency of the increase in RI was noted. No significant differences were observed within the first 6 h after the onset of symptoms. From 6 to 48 h, however, the mean RI in the affected kidney (0.70 +/- 0.06; mean +/- SD) was significantly different from that in the normal kidney (0.59 +/- 0.04) (P < 0.001). In the same period the mean difference in RI was 0.08-0.13 (P < 0.001). After 48 h the sensitivity of RI dropped substantially. It is concluded that renal duplex Doppler ultrasonography is useful for diagnosing acute renal obstruction between 6 and 48 h after the onset of symptoms.  相似文献   
95.
The stability properties of the forward and the flyback inverter are compared. A free-running inverter is not suited for grid-connected applications. The realisation of a high open-circuit gain in a system with an externally determined switching frequency and without the loss of the power capacity is discussed. A 250 W low-distortion grid-connected forward inverter has been realised.  相似文献   
96.
97.
A sensitive and reliable method was developed for the measurement of simple flavanols in beer by direct-injection High Performance Liquid Chromatography using dual-electrode electrochemical detection. When operated in the amperometric mode the detector was extremely sensitive for readily-oxidized substances such as polyphenols, so that sample preparation was minimal. The dimeric flavanols in a commercial beer were positively identified as procyanidin B3 and prodelphinidin B3. Tentative identifications for three trimeric proanthocyanidins were made also. Collectively, monomeric, dimeric and trimeric flavanols accounted for only about 4% of the colorimetrically determined total polyphenol content, and about 35% of the total flavanol content of a non-haze stabilized beer. The improved chromatographic method was applied to measuring the decreases in simple flavanols caused by treatment of beer with polyvinylpolypyrrolidone.  相似文献   
98.
We have studied the histopathology of 87 dorsal penile veins, obtained from patients who underwent a resection of the deep dorsal penile vein because of proven venous leakage. The amount of muscle tissue and of collagenous connective tissue has been numerically quantified. Special attention has been focused on the muscular/collagenization ratio. We show that this ratio is not correlated to age neither with the outcome of the operation and that no differences exist between veins in venous leakage patients and in potent patients. This study confirms that the reduction of venous outflow-the so called corporeal veno-occlusive mechanism-is probably a secondary passive phenomenon, due to smooth muscular relaxation, and mainly located within the corpora cavernosa, between the expanding sinusoidal wall and the noncompliant tunica albuginea. Our findings also strongly refute the hypothesis that polsters or other venous wall characteristics contribute to the normal physiology of the deep dorsal penile vein.  相似文献   
99.
The pancreaticoduodenocystostomy has become the most acquired technique to perform a combined pancreas-kidney-transplantation. This operation shows some disadvantages. There sometimes are urological problems. In this article, we describe two patients, who showed urethral problems due to this operation. At the same time, we would like to describe the possible causes and the preferable treatment of this rare complication. We advise to start with a conservative treatment and, if problems persist, to consider an intestinal conversion.  相似文献   
100.
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