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   2467篇
  免费   3篇
综合类   2篇
化学工业   8篇
机械仪表   1篇
建筑科学   1篇
轻工业   3篇
水利工程   1篇
石油天然气   1篇
无线电   2篇
一般工业技术   8篇
冶金工业   2437篇
自动化技术   6篇
  2023年   2篇
  2022年   2篇
  2021年   3篇
  2020年   1篇
  2019年   1篇
  2018年   2篇
  2017年   2篇
  2016年   1篇
  2013年   2篇
  2012年   2篇
  2011年   1篇
  2010年   2篇
  2009年   3篇
  2008年   1篇
  2007年   1篇
  2003年   4篇
  2000年   1篇
  1999年   71篇
  1998年   746篇
  1997年   418篇
  1996年   301篇
  1995年   148篇
  1994年   128篇
  1993年   143篇
  1992年   13篇
  1991年   23篇
  1990年   26篇
  1989年   21篇
  1988年   22篇
  1987年   21篇
  1986年   19篇
  1985年   13篇
  1984年   1篇
  1983年   7篇
  1982年   14篇
  1981年   15篇
  1980年   23篇
  1979年   3篇
  1978年   9篇
  1977年   62篇
  1976年   177篇
  1975年   4篇
  1973年   2篇
  1965年   1篇
  1964年   3篇
  1963年   1篇
  1960年   1篇
  1955年   3篇
排序方式: 共有2470条查询结果,搜索用时 15 毫秒
21.
Gonadal hormones affect body composition, food intake, weight gain and serum lipids in numerous species including man. In this study, mature male Sprague-Dawley rats were castrated or sham-operated at 16 weeks of age. During the 6-week observation period with weekly records of food intake and weight gain, these parameters were significantly lower in the castrated group. The decrease in food intake in this group could not account for the difference in body weight between the groups, indicating a lower feed utilisation in the castrates. At sacrifice accessory reproductive organs, the levator ani muscle, thymus and adrenals were dissected for determination of organ weight and histology, revealing significant reductions in the accessory reproductive organs and levator ani of the castrates. The thymus was significantly heavier in the castrated animals. No differences were found in the adrenals. Two of the sham-operated animals had signs of accidental functional castration. The proportion of body cell mass and total lipid of the carcass was the same in both groups. Significant reductions in adipocyte weights were found in the epididymal depots of the castrated rats. Blood samples taken at sacrifice in pentobarbital anaesthesia were analysed for glucose, insulin, triglycerides, cholesterol, FFA, glycerol and protein. Statistically significant reductions in triglycerides and protein were recorded in the castrated animals without any significant changes in the other parameters studied. The results are discussed with reference to the age of castration and the importance of the reduced food intake in castrated animals.  相似文献   
22.
In the Public Salughter-House of Utrecht, a percentage increase in the number of pigs with inflammation of the tail, which had or had not healed, was observed during the period from 1972 to 1974 inclusive. The most common secondary symptoms of inflammation consisted in embolic pneumonia, osteomyelitis of the vertebrae and abscess formation in other parts of the body, particularly the semimebranosus muscles. Osteomyelitis was found to be the most common complication in pigs in which the inflammation of the tail had healed, whereas this usually consisted in embolic pneumonia in those cases in which the inflammation of the tail had not healed. The bacteriological examination carried out in accordance with the Meat Inspection Regulations was positive in 21.7 per cent, 13.5 per cent of the cases respectively in 1972, 1973 and 1974. Micro-organisms were isolated much more frequently from the kidney than they were from the spleen and meat. There was no relationship between the presence of inflammation of the tail and climatological conditions during the fattening period. The losses at slaughter from inflammation of the tail in the Netherlands are estimated at 3-4 million guilders per annum.  相似文献   
23.
Although iodine prevents goiter, enlarged thyroid glands continue to be detected in subjects, especially children, in spite of adequate iodine ingestion. Iodine may cause goiter in susceptible individuals by inhibiting the organic binding of iodine as is seen in adult asthmatics, neonates born of iodine ingesting mothers and in subjects residing along the littoral of Japan. Myxedema, especially in treated Graves' disease and Hashimoto's disease, may also be precipitated by iodine. On the other hand, iodine given to euthyroid subjects in areas of endemic goiter and to subjects with nontoxic nodular goiter may induce thyrotoxicosis by disclosing diffuse autonomously functioning thyroid tissue. An indirect adverse effect of iodine upon the thyroid gland may be manifested by lymphocyte glandular infiltrates and chronic thyroiditis which were sparse or absent in thyroid glands removed from subjects living in iodine deficient areas before iodine prophylaxis and therapy. Not only has the incidence of thyroiditis increased, but the histologic and clinical distinctions between treated Graves' disease and chronic thyroiditis have become indistinct. Experimentally, chronic thyroiditis has been produced in animals following large doses of iodine. Accumulated evidence supports the concept that iodine contributes to the genesis of chronic thyroiditis.  相似文献   
24.
We have used dacryoscintigraphy to study the efficiency of the lacrimal system following the repair of a divided lower canaliculus in 4 children. This test has been reliable in evaluating lacrimal function and suggests that a canaliculus can be repaired and splinted satisfactorily. Our experience with dacryoscintigraphy confirms that it is a safe comfortable, and reliable method for studying the patency of the lacrimal drainage system.  相似文献   
25.
In the routine laboratory for hematology conflicting results may be obtained for the red blood cell parameters with the Coulter Counter Model S. These parameters2) are: mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC). When the values of the MCHC are above 36 g/dl something must be wrong with the blood sample of the patient. One of the reasons can be agglutination e.g. by cold agglutinins. The blood sample should be reanalysed before and after heating for 1 hour at 37 degrees C. If the values change: cold agglutinins are present; if no change occurs paraproteins, or other disturbing factors, such as bilirubin or high leucocyte levels, will be found. MCH values may also be high in some cases e.g. if the red blood cells are coated with antibodies (Coombs test positive) or after ingestion of medicines like Azathioprine. These examples show that it is possible in some cases to correlate immunological findings with the red blood cell parameters. In addition to the results with the Coulter Counter Model S, some observations on the Hemalog (Technicon) are also presented.  相似文献   
26.
27.
Four patterns of inositol fermentation by different isolates of Klebsiellae are described. Inositol fermentation by some isolates may be modified by medium incorporation of acetoin and diacetyl. An inositol--hydrogen sulphide--motility medium, modified by reducing the pH value, increasing the inositol concentration, and the incorporation of acetoin, is described and evaluated as a means of detecting acid production by isolates showing different inositol fermentation patterns.  相似文献   
28.
Administered a revision of the Test Anxiety Scale for Children (TASC) on which there were separate comparative Self-Evaluation and Anxiety scales to 133 females and 131 males in Form 1 (equivalent to Grade 6). Ss also responded to self-report measures (self-concept of attainment, causal attribution, independent reading, and friendship choices), and teachers rated Ss on their classroom behavior. Findings indicate that correlations between Ss' TASC scores and variables that had been found to be related to the original scale and assumed to be affected by anxiety were generally higher for the Self-Evaluation scale than the Anxiety scales. It is suggested that many results with the TASC may be better interpreted in terms of self-evaluation than anxiety effects. Results with measures of causal attributions suggest that self-evaluation measures are more effective predictors of achievement behavior than anxiety measures because anxiety is but one of a number of possible consequences of poor self-evaluation that could mediate relatively unproductive achievement behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
29.
This study was undertaken to determine the relative effects of morphine and halothane anesthesia on coronary blood flow. Right heart bypass was instituted in 20 dogs by draining the vena cava blood into a cardiotomy reservoir and returning it to the main pulmonary artery. Coronary sinus drainage was measured by a right ventricular cannula. Group I (10 dogs) was sequentially given 0.5, 1, 1.5, 2.0, and 2.5% halothane. Group II (10 dogs) was given 1, 2, 3, 4, and 5 mg per kilogram of morphine intravenously. Arterial pressure, coronary sinus blood flow, cardiac output, arterial pH, PCO2, and PO2 were determined and repeated at each dose level of anesthesia and compared to the control values. Morphine significantly increased coronary flow at 3, 4, and 5 mg/kg without pressure adjustment and at 2 mg/kg after pressure adjustment. Coronary flow with halothane was unchanged from control values except for a decrease at 2.5%. Coronary flow was significantly greater with 3, 4, and 5 mg/kg of morphine than with 1.0 and 1.5% halothane.  相似文献   
30.
Ribosomes isolated from either dry viable or non-viable pea embryonic axis tissue were equally effective in the support of polyphenylalanine synthesis in a poly(U)-directed cell-free protein-synthesising system. Ribosomes isolated from imbibed non-viable axis tissue were impaired in their ability to support polyphenylalanine synthesis in the cell-free system. RNA isolated from ribosomes and 40-S ribosomal subunits of dry or imbibed viable axis tissue was found not to be degraded, whereas the equivalent RNA species isolated from non-viable axis tissue showed an increased degree of breakdown as imbibition proceeded. Even though rRNA of imbibed non-viable axis tissue was degraded, the ribosomes and ribosomal subunits of these embryos appeared intact. In viable embryonic axis tissue the percentage of ribosomes present in the cell in the form of polysomes increased during imbibition whereas no polysomes could be detected in ribosomal preparations from dry or imbibed non-viable axis tissue. The breakdown of rRNA in ribosomal particles from non-viable axis tissue may be a contributory factor to senescence and loss of viability in Pisum arvense.  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