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   1657篇
  免费   2篇
电工技术   1篇
化学工业   20篇
建筑科学   3篇
能源动力   1篇
轻工业   21篇
水利工程   1篇
石油天然气   5篇
无线电   6篇
一般工业技术   20篇
冶金工业   1568篇
自动化技术   13篇
  2021年   2篇
  2019年   1篇
  2018年   1篇
  2017年   1篇
  2016年   1篇
  2014年   1篇
  2013年   2篇
  2012年   2篇
  2011年   4篇
  2010年   4篇
  2009年   1篇
  2008年   3篇
  2007年   1篇
  2006年   4篇
  2005年   2篇
  2004年   3篇
  2003年   4篇
  2002年   3篇
  2001年   4篇
  2000年   5篇
  1999年   42篇
  1998年   473篇
  1997年   281篇
  1996年   179篇
  1995年   103篇
  1994年   78篇
  1993年   111篇
  1992年   15篇
  1991年   15篇
  1990年   12篇
  1989年   24篇
  1988年   24篇
  1987年   21篇
  1986年   31篇
  1985年   20篇
  1983年   4篇
  1982年   10篇
  1981年   8篇
  1980年   13篇
  1979年   2篇
  1978年   2篇
  1977年   42篇
  1976年   86篇
  1975年   3篇
  1974年   2篇
  1972年   5篇
  1971年   1篇
  1970年   2篇
  1955年   1篇
排序方式: 共有1659条查询结果,搜索用时 8 毫秒
81.
82.
Most infant formulas use vegetable oils in place of milk fat to provide an overall fatty acid profile similar to that of breast milk. Vegetable oils have 5 to 20% saturated fatty acids in the sn-2 position of triglycerides unless they are modified by interesterification. Interesterification is increasingly used for the fat for infant formulas to raise the level of saturated fatty acids in the sn-2 position to 40 to 60%. The objective of this study was to verify an alternative approach to providing the appropriate fatty acid profile, including in the sn-2 position, for a goat infant formula. In this method, 55% of total fat was made from goat milk fat and 45% from a mixture of unmodified high oleic sunflower, canola, and sunflower oils in a ratio of 44:30:26. The fatty acid profile was measured by gas-liquid chromatography and the relative percentage of fatty acids in the sn-2 position of triglycerides was measured via partial deacylation with Grignard reagent using trimethylsilyl derivatives of monoacylglycerols. Mixing goat milk fat with vegetable oils produced a formula with a profile of essential fatty acids and a ratio of linoleic:α-linolenic fatty acids within the required interval of 5 to 15:1 recommended for infant formula. The proportion of palmitic acid in the sn-2 position was 31%.  相似文献   
83.
84.
85.
The investigators present an analysis of baseline quality-of-life and patient-management approaches from an observational study of 150 patients being treated by podiatric physicians and dermatologists for onychomycosis. The majority (73%) made the initial office visit specifically because of their onychomycosis. Both men and women indicated that they had substantial physical discomfort as well as concerns related to appearance. Women reported significantly more problems than did men as a result of their onychomycosis. Physicians reported that 54% of patients suffered from toenail discomfort, 36% had pain while walking, 40% reported that their condition limited wearing of shoes, and 67% were embarrassed by the condition. The results of this study suggest that the treatment approach of podiatric physicians is more likely to address the palliative concerns of patients with onychomycosis, while the approach of dermatologists is more likely to attempt a definitive cure.  相似文献   
86.
DP Warren  JT Chan 《Canadian Metallurgical Quarterly》1997,45(2):134-40, 142; quiz 145-6
Fluoride's role in decreasing dental caries has been recognized for decades. The professional fluoride treatment has recently been augmented with home-use fluoride products. The introduction of many attractive products makes it difficult for dental professionals to know which are effective. Both professional and home-use products are described, as are proven techniques for their use. Recognition of fluoride toxicity, and its prevention and treatment, are also discussed.  相似文献   
87.
S Teich  DP Barton  ME Ginn-Pease  DR King 《Canadian Metallurgical Quarterly》1997,32(7):1075-9; discussion 1079-80
Since 1962, the Waterston classification has been used to stratify neonates who have esophageal atresia (EA) and/or tracheoesophageal fistula (TEF) into prognostic categories based on birth weight, the presence of pneumonia, and the identification of other congenital anomalies. In response to advances in neonatal care, the surgeons from the Montreal Children's Hospital proposed a new categorization system in 1993 in an attempt to define the current risk factors for patients who have EA/TEF. In the Montreal experience only two characteristics independently affected survival: preoperative ventilator dependence and associated major anomalies. The goal of this study was to determine which system had the greatest validity for the evaluation of prognosis in our patients with EA/TEF. The charts of 94 patients who had EA/TEF treated between 1972 and 1991 were reviewed. Patients were classified using both the Waterston and Montreal systems. Groups were compared with Fisher's Exact test using a 95% confidence level for statistical significance. Eleven infants were ventilator dependent preoperatively; 62 children had major associated anomalies, 8 of which were considered life threatening. Sixteen children died within 4 years, eight during their initial hospital stay. Five of the eight early postoperative deaths occurred in the highest-risk patients (Waterston C or Montreal II). Analysis was performed for multiple risk factors and mortality. As in the Montreal study, the presence of life-threatening and major congenital anomalies represented significant risk factors for death. Pulmonary disease as delineated by ventilator dependence appeared to be more accurate than pneumonia. This study confirms the accuracy of the Montreal classification in defining prognosis for EA/TEF. The Montreal system more accurately identifies children at highest risk than the Waterston classification.  相似文献   
88.
89.
Patients with craniocervical mandibular (TMD) disorders can present with tinnitus as a primary or secondary complaint. The embryology and functional anatomy of the middle ear, temporomandibular joint, muscles of mastication and associated tendons, ligaments, blood vessels, nerves and lymphatics was found to be helpful in establishing etiologic concepts which relate tinnitus to these temporomandibular disorders. In addition to etiologic concepts, treatment modalities are described. The authors relate their experiences as well as those of others with different patient populations.  相似文献   
90.
Although body condition score was not significantly different between light (<55 kg, n = 6) and heavy (> or =60 kg, n = 7) ewes at mating, it declined between Day 30 and Day 90 of gestation in light but not heavy ewes, and remained lower up to term. All ewes bore twins, delivered near term (Days 144-146) by Caesarean section. One lamb was immediately placed into a warm (30 degrees C; WD) and its twin into a cool (15 degrees C; CD) ambient temperature, and tissues were sampled at 0.5 h or 6 h. All CD lambs born to light ewes exhibited hypothermia and/or respiratory failure and did not survive longer than 30 min; these symptoms were not observed in their WD twins or any lamb born to heavy ewes. Total lamb birth weight, placental weight and fetal cotyledonary weight were lower with light than with heavy ewes. Lambs born to light ewes had less perirenal adipose tissue and smaller liver, heart, kidneys, brain, adrenals and thyroid, although their heart, brain and pancreas represented a larger proportion of total bodyweight; pancreas weight was similar to that in lambs born to heavy ewes. Hence, maternal bodyweight critically influences placental weight and lamb size and survival after birth.  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