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   2484篇
  免费   0篇
电工技术   1篇
化学工业   7篇
建筑科学   1篇
轻工业   1篇
无线电   3篇
一般工业技术   3篇
冶金工业   2463篇
原子能技术   2篇
自动化技术   3篇
  2019年   1篇
  2016年   1篇
  2013年   1篇
  2006年   2篇
  2004年   1篇
  2001年   2篇
  1999年   58篇
  1998年   770篇
  1997年   459篇
  1996年   274篇
  1995年   184篇
  1994年   101篇
  1993年   150篇
  1992年   18篇
  1991年   26篇
  1990年   22篇
  1989年   18篇
  1988年   24篇
  1987年   31篇
  1986年   15篇
  1985年   14篇
  1984年   1篇
  1983年   5篇
  1982年   10篇
  1981年   28篇
  1980年   18篇
  1978年   4篇
  1977年   83篇
  1976年   153篇
  1975年   5篇
  1973年   2篇
  1955年   3篇
排序方式: 共有2484条查询结果,搜索用时 15 毫秒
101.
Reinfusion of autologous blood in 22 patients with cancer of the kidney was used during nephrectomy. Intraoperative blood loss made up 1000-4000 ml (20-80% VCB). 800-3600 ml of blood was collected from the operation wound and reinfused. In spite of massive blood loss, 20 patients recovered. Lethal outcomes (2 patients) were not caused by blood reinfusion. In 19 patients of control group with renal cancer massive blood loss was compensated by preserved donor blood transfusion. It is shown that reinfusion of autologous blood promotes more stable hemodynamics during the operation, reduces the quantity of postoperative complications and lethal outcomes, provides qucker restoration of morphologic structure of the blood and results in less substantial changes in filtration of a single kidney. There were no statistically significant differences in 5-year survival rate of patients in the study (40.9%) and control (42.1%) groups, nor in the frequency of hematogenous metastasizing of cancer. Because blood reinfusion does not increase the risk of hematogenous metastases of cancer, it is not contraindicated in massive blood loss during nephrectomy in patients with renal cancer.  相似文献   
102.
We report 23 prospective studies on 18 maintenance dialysis patients in whom we measured skeletal mineralization rate (m) using 47Ca, analyzed by the expanding pool model, and compared it with the histologic bone formation rate (bfr), volume referent, estimated on tetracycline-labeled iliac crest bone. The patients showed a spectrum of bone disease types including adynamic bone, aluminum-related osteomalacia, and various degrees of secondary hyperparathyroidism. The mean width between double labels, on which mineral apposition rate depended, was estimated using a simple formula relating area to perimeter for each feature enclosed by the labels. Values for m ranged from 0 to 155 mmol calcium per day and for bfr from 0 to 124% per year. There was close correlation between m and bfr (r = 0.976), serum alkaline phosphatase (r = 0.968), and serum immunological parathyroid hormone (iPTH) (r = 0.868). When the volumetric bfr was converted to mass units and applied to the whole skeleton, using literature values for mineral density and cortical and trabecular mass, there was close agreement between the histologic and isotopic estimates of m (r = 0.959). The results validate the two methods and suggest they are interchangeable. However, use of a rigorous method to determine bfr appears to be essential.  相似文献   
103.
MMPI, MBHI, and MCMI personality disorder scales were analyzed for convergent and discriminant validity. Friedman's ANOVA indicated that there were no significant differences among the sample's averaged scale scores. Further analyses of these data, however, demonstrated that the Millon instruments classified significantly more of the sample as personality disordered when compared to Morey's MMPI personality disorder scales. In addition, codetype correspondence among the three instruments was only 4 to 6%. When the instruments were analyzed in a pair-wise fashion, codetype correspondence increased to approximately 10 to 20%. These data indicate that these personality disorder scales do not demonstrate construct equivalence, particularly at the level of the individual profile.  相似文献   
104.
PURPOSE: We prospectively evaluated the current spectrum of urodynamic pathology in patients infected with human immunodeficiency virus (HIV) who presented with voiding dysfunction. MATERIALS AND METHODS: We obtained a directed genitourinary and neurological history, and performed a physical examination and urodynamic testing in 18 patients. A 4-channel membrane urethral catheter was used to record intravesical and intraurethral pressures simultaneously. RESULTS: Detrusor hyperreflexia was present in 28% of our patients and detrusor-sphincter dyssynergia in 28%. Detrusor areflexia, previously described as the most frequent abnormality, was uncommon in our series (6% of patients). CONCLUSIONS: This changing proportion of urodynamic diagnoses may reflect a changing pattern of neurological manifestations of HIV infection due to more aggressive management. Urodynamic evaluation remains critical for precise diagnosis and treatment in patients with HIV who present with urinary symptoms.  相似文献   
105.
Hematocrits (PCV) were measured at 29 and 106 d of age (PCV1 and PCV2, respectively) in male and female White Plymouth Rocks. Four lines were used, two of which had undergone 40 generations of divergent selection for 8-wk BW (HWS, LWS), and two respective sublines (HWR, LWR), in which selection had been relaxed for five generations. At both ages, males and females did not differ for PCV in lines HWR, LWR, and LWS. For line HWS there was an age by sex interaction that resulted from an age effect for males but not for females, and from a sex effect at each age. At both ages, PCV was higher for the HW than the LW lines. Initially, there was no difference between the selected and their respective relaxed lines, but by 106 d, HWR chickens had a higher PCV than HWS chickens. In lines HWR and LWR, PCV increased with age. There was a negative correlation in HWS males for PCV1 with 28 and 56 d BW. The HWR males also had a negative correlation for PCV1 with BW at 28 d, but not between PCV2 and BW. The correlation for PCV1 with PCV2 was high and positive for HWR males and females.  相似文献   
106.
107.
108.
The levels of phosphate esters and the activities of thiamine biotransformation enzymes in the blood and tissues of albino rats were studied during oxythiamine-induced B1 deficiency and after metabolic correction with thiamine and taurine. Among thiamine phosphates, the most informative indicators of thiamine deficiency were shown to be triphosphate esters and free thiamine diphosphate. The biosynthetic enzymes thiamine kinase and thiamine diphosphate kinase played a decisive role in maintaining the initial rate and in recovering the physiologically active forms of vitamin B1. The activation of hydrolytic enzymes of thiamine phosphate esters occurred by producing abundant free thiamine diphosphate and thiamine triphosphate. Within the first hours, taurine favoured the acceleration of phosphoester biosynthesis and, accumulating in the tissues, inhibited vitamin phosphorylation reactions.  相似文献   
109.
A community survey of all Danish speaking residents above the age of 64 in a geographically delimited area was performed. The aim of the survey was to establish the prevalence of dementia disorders and depression by the use of international screening tools: the Mini Mental State Examination for dementia and the Beck's Depression Inventory for depression. The screening was performed during the period of one year in the municipality of Karlebo and the interviews took place in the homes of the participants. Six hundred and sixty-four (66%) of the 1,008 eligible persons entered the study. Six percent were residents in nursing homes. Thirteen point seven percent were found to be suffering from dementia. Nine point six percent had symptoms of depression. These prevalences would indicate that more than 6,000 persons in Frederiksborg county suffer from dementia while more than 4,000 might be suffering from depression. The study confirms knowledge obtained in other studies, indicating that one out of seven of the elderly suffers from dementia. We do not conclude, however, that nine point six percent suffer from depression, but rather that they need further examination to make it possible to decide whether they are indeed depressed.  相似文献   
110.
A role for GH in the pathogenesis of diabetic retinopathy has long been postulated. Previous clinical studies, however, have been confounded by hyperglycemia. We have identified 2 cases of retinopathy associated with exogenous GH therapy in nondiabetic patients. Cases were identified through the MedWatch drug surveillance system of the U.S. Food and Drug Administration. Causality by concomitant medications was excluded by a search of the literature and the FDA data base. The first patient, an obese, 31-yr-old male with traumatic hypothalamic injury, presented with nonproliferative retinopathy and macular edema, resulting in decreased visual acuity (OD 20/40-1; OS count fingers), which required laser surgery. Human GH had been initiated at 0.009 mg/ kg.day, 14 months earlier, and titrated to 0.017 mg/kg.day. The second patient, a nonobese, 11-yr-old girl receiving GH for the management of short stature in Turner's Syndrome, presented with neovascularization. GH doses were 0.033 mg/kg.day for the first 17 months and 0.043 mg/ kg.day for the following 5 months. Cumulative laboratory and clinical observations suggest that GH and related peptides have a role in retinal pathology independent of the degree of glucose tolerance.  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