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   2251篇
  免费   15篇
电工技术   5篇
综合类   1篇
化学工业   139篇
金属工艺   7篇
机械仪表   11篇
建筑科学   10篇
矿业工程   1篇
能源动力   24篇
轻工业   57篇
水利工程   5篇
石油天然气   3篇
无线电   34篇
一般工业技术   129篇
冶金工业   1747篇
原子能技术   12篇
自动化技术   81篇
  2022年   18篇
  2021年   19篇
  2020年   2篇
  2019年   6篇
  2018年   15篇
  2017年   11篇
  2016年   15篇
  2015年   9篇
  2014年   13篇
  2013年   35篇
  2012年   35篇
  2011年   42篇
  2010年   27篇
  2009年   37篇
  2008年   34篇
  2007年   21篇
  2006年   15篇
  2005年   24篇
  2004年   14篇
  2003年   16篇
  2002年   11篇
  2001年   19篇
  2000年   12篇
  1999年   55篇
  1998年   497篇
  1997年   306篇
  1996年   196篇
  1995年   117篇
  1994年   112篇
  1993年   113篇
  1992年   16篇
  1991年   29篇
  1990年   19篇
  1989年   24篇
  1988年   17篇
  1987年   32篇
  1986年   18篇
  1985年   27篇
  1983年   4篇
  1982年   10篇
  1981年   20篇
  1980年   18篇
  1979年   3篇
  1978年   5篇
  1977年   46篇
  1976年   109篇
  1975年   5篇
  1973年   6篇
  1972年   2篇
  1968年   2篇
排序方式: 共有2266条查询结果,搜索用时 0 毫秒
11.
Two patients with mitochondrial myopathy (Kearns-Sayre syndrome) received general anaesthesia. In the first case propofol-alfentanil anaesthesia was carried out; the second patient received propofol-fentanyl anaesthesia. Muscle relaxation was provided with vecuronium. In both cases we observed a short episode of bradycardia (heart rate < 50.min-1), which was successfully treated with atropine. After the propofol infusion had been stopped, both patients rapidly gained consciousness and were extubated after prompt spontaneous ventilation had returned. Reversal of neuromuscular blockade in the second patient was achieved within 5 min by neostigmine. Special anaesthetic problems in patients with mitochondrial myopathies such as myocardial conduction disturbances, postoperative muscle hypotonia, and possible increased susceptibility to malignant hyperthermia can be overcome by the described anaesthetic management.  相似文献   
12.
13.
The mechanism behind the hypolipidemic effect of tetradecylthioacetic acid (CMTTD, a non-beta-oxidizable 3-thia fatty acid) was studied in hamsters fed a high cholesterol diet (2%), which resulted in hyperlipidemia. Treating hyperlipidemic hamsters with CMTTD resulted in a progressive hypocholesterolemic and hypotriacylglycerolemic effect. Decreased plasma cholesterol was followed by a 39% and 30% reduction in VLDL-cholesterol and LDL-cholesterol, respectively. In contrast, the HDL-cholesterol content was not affected, thus decreasing the VLDL-cholesterol/HDL-cholesterol and LDL-cholesterol/HDL-cholesterol ratios. 3-Hydroxy-3-methylglutaryl- (HMG) CoA reductase activity and its mRNA level were unchanged after CMTTD administration. Also, the LDL receptor and LDL receptor-related protein (LRP-4) mRNAs were unchanged. The decrease in plasma triacylglycerol was accompanied by a 45% and 56% reduction in VLDL-triacylglycerol and LDL-triacylglycerol, respectively. The hypolipidemic effect of CMTTD was followed by a 1.4-fold increase in mitochondrial fatty acid oxidation and a 2.3-fold increase in peroxisomal fatty acid oxidation. CMTTD treatment led to an accumulation of dihomo-gamma-linolenic acid (20:3n-6) in liver, plasma, very low density lipoprotein, and heart. Noteworthy, CMTTD accumulated more in the heart, plasma, and VLDL particles compared to the liver, and in the VLDL particle alpha-linolenic acid (18:3n-3) decreased whereas eicosatetraenoic acid (20:4n-3) increased. In addition, linoleic acid (18:2n-6) and the total amount of polyunsaturated fatty acids decreased, the latter mainly due to a decrease in n-6 fatty acids. The present data show that CMTTD was detected in plasma and incorporated into VLDL, liver, and heart. The relative incorporation (mol%) of CMTTD was heart > VLDL > liver. In conclusion, CMTTD causes both a hypocholesterolemic and hypotriacylglycerolemic effect in hyperlipidemic hamsters.  相似文献   
14.
In patients with cervical instability as the primary injury, either ligamentous or bony, a posterior approach and stabilization is the most likely definitive treatment. The goals should be to obtain and maintain satisfactory alignment, promote fusion, and allow safe and early mobilization. Many techniques that differ in safety, ease of application, cost, biomechanical strength, and postoperative requirements of immobilization are available. This article reviews different methods of posterior surgical interventions in subaxial cervical spine injuries and discusses the advantages and disadvantages of each.  相似文献   
15.
Mineralocorticoid action is facilitated by 11 beta-hydroxysteroid dehydrogenase type II (11 beta HSD2), which metabolizes glucocorticoids and allows aldosterone to bind to the nonselective mineralocorticoid receptor. We have recently demonstrated the presence of the 11 beta HSD2 protein in a wide range of human epithelia, suggesting that it is the sole isoform endowing specificity in man. In the present study we have used an immunopurified polyclonal antibody (RAH23) raised against a C-terminal peptide derived from the cloned rat 11 beta HSD2 protein to perform immunohistochemical and molecular analysis in rat tissues. In frozen sections of rat kidney, strong staining was seen with the RAH23 antibody in the distal tubule; weaker staining was observed in the thick ascending loop of Henle and the medullary and papillary collecting ducts. Punctate cortical staining was observed in the fetus at 20 days gestation and in 8-day-old rats, with a noticeable increase in the staining pattern at 16 days of age. The kidney did not attain the adult pattern of staining until 28 days of age. Epithelia of ileum and colon also stained with RAH23, as did excretory ducts of the submandibular gland. Intrahepatic and excretory bile ducts displayed strong immunoreactivity in the epithelial lining. Rat adrenal glands showed evidence of the 11 beta HSD2 antigen in the zona fasciculata and zona reticularis, but not in the zona glomerulosa or medulla. Western blot analysis with the RAH23 antibody revealed strong bands in the kidney, colon, adrenal gland, and submandibular gland at 40 kDa, colinear with the migration of the cloned 11 beta HSD2 enzyme. A band of medium intensity was also seen at this size in the pancreas, whereas a band of moderate intensity was seen in the bile duct, and weaker bands were noticed in the stomach, small intestine, and liver, with a diffuse band at 36-42 kDa in the prostate. Strong bands were seen in the pancreas and prostate at 78 kDa, with weaker signals in the colon, adrenal, stomach, and bile duct. A number of tissues also displayed multiple bands at about 30 kDa. Enzymatic assays on tissue homogenates showed extensive conversion of corticosterone to its 11-dehydro product in an NAD-dependent manner in the submandibular gland, adrenal gland, and kidney, but not in the pancreas or prostate. This study confirms the ubiquitous presence of 11 beta HSD2 in sodium-transporting epithelia, demonstrates the high level of 11 beta HSD2 protein and enzyme activity in the rat adrenal, and suggests a possible role for the enzyme in the biliary system. Further studies are required to determine the relevance of the various molecular species to the activity, latency, and processing of the enzyme.  相似文献   
16.
17.
18.
A semi-quantitative right coronary artery score (RCA score) was derived from the ratio of the number of the major left ventricular branches of the right coronary artery to the total of the right coronary and left circumflex arteries, to stratify the extent of perfusion in patients with right coronary artery dominance. Thirty-seven patients with one-vessel coronary disease involving a dominant right coronary artery proximal to the left ventricular branches were selected for study. Thallium scintigraphy was performed after right intracoronary injection in 11 patients, and 26 patients underwent conventional stress thallium scintigraphy (24 exercise thallium and two dipyridamole thallium scintigraphy). Thallium scores of perfusion region size after right intracoronary thallium injection and perfusion defect size in stress thallium studies were quantitated from planar thallium images. Both the RCA score and the regional thallium scores spanned over a wide range. The RCA score (range 0.23-0.85) correlated best with the posterior (70 degrees left anterior oblique view) plus lateral segment (40 degrees left anterior oblique view) thallium score (r = 0.88 and 0.53 for intracoronary and stress thallium studies respectively). It also correlated with the summed thallium scores in the posterior, lateral, apical and inferior segments (r = 0.73 and 0.54 respectively) but not with thallium scores in the apex or inferior segment alone. The proposed RCA score quantitates the variable posterolateral perfusion territory of the right coronary artery, and could stratify the area of myocardium at risk from coronary stenosis in the majority of patients with right coronary dominance.  相似文献   
19.
20.
We recently diagnosed subcutaneous fat necrosis in a newborn female infant using fine needle aspiration cytology. The neonate had perinatal asphyxia and her mother a difficult labor, but otherwise the neonate was well developed and healthy and within a few days developed well-defined areas of subcutaneous induration all over. On cytologic examination of the aspirated material, many necrotizing fat cells were found with refractile, needle-shaped crystals arranged in a sheaflike or starburst pattern. Subcutaneous fat necrosis of the newborn is uncommon today, and although the histologic findings from excised tissue are known, this appears to be the first case in which the diagnosis was possible from a sample of fine needle aspirate.  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