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   612篇
  免费   0篇
化学工业   4篇
机械仪表   3篇
轻工业   1篇
冶金工业   604篇
  2023年   1篇
  2021年   1篇
  2014年   1篇
  2010年   1篇
  2005年   1篇
  2000年   1篇
  1999年   15篇
  1998年   194篇
  1997年   103篇
  1996年   66篇
  1995年   33篇
  1994年   41篇
  1993年   40篇
  1992年   2篇
  1991年   3篇
  1990年   2篇
  1989年   3篇
  1988年   4篇
  1987年   5篇
  1986年   2篇
  1985年   1篇
  1983年   2篇
  1982年   4篇
  1981年   4篇
  1980年   6篇
  1979年   1篇
  1977年   21篇
  1976年   50篇
  1975年   2篇
  1974年   1篇
  1955年   1篇
排序方式: 共有612条查询结果,搜索用时 15 毫秒
161.
We review the evidence supporting the role of glucocorticosteroids, trilazad, and GM1 ganglioside in spinal cord injury and provide our critique of the published studies, along with our recommendations for pharmacologic therapy for this complex and difficult problem.  相似文献   
162.
To address the effect of electroacupuncture (Ea) on autonomic nerve activity, the responses of rhythmic micturition contraction (RMC), urine excretion (UE), blood pressure (BP), renal sympathetic nerve activity (RNA) and pelvic parasympathetic nerve activity (PNA) to Ea were investigated in urethane-anesthetized rats. The acupoint Hoku (Li-4) was tested with two different stimulation frequencies (2 Hz and 20 Hz). Elongation of the RMC cycle and an increase in UE associated with the elevation of BP and RNA was elicited during Ea at Hoku. However, the pressor response induced by low frequency Ea (LFEa) was different from that by high frequency Ea (HFEa), i.e. a tonic effect was elicited by LFEa, while a phasic one was induced by HFEa. These results imply that: (1) Ea at Hoku may selectively activate the sympathetic, but not the parasympathetic nervous system, (2) Ea at Hoku with a different stimulation frequency may elicit a distinct mechanism to activate the sympathetic nervous system and (3) Ea at Hoku may ameliorate the hyperactive bladder in clinical therapy.  相似文献   
163.
BACKGROUND: Change in body weight is a potentially modifiable risk factor for hip fracture in older women but, to our knowledge, its relationship to risk in older men has not been reported previously. OBJECTIVE: To investigate the effects of weight loss and weight gain from age 50 years to old age on the risk of hip fracture among elderly men. METHODS: The association between weight change and risk of hip fracture was studied in a cohort of 2413 community-dwelling white men aged 67 years or older from 3 sites of the Established Populations for Epidemiologic Study of the Elderly. RESULTS: The older men in this study, observed for a total of 13620 person-years during the 8 years of follow-up, experienced 72 hip fractures, yielding an overall incidence rate of 5.3 per 1000 person-years. Extreme weight loss (> or =10%) beginning at age 50 years was associated in a proportional hazards model with increased risk of hip fracture (relative risk, 1.8; 95% confidence interval, 1.04-3.3). Weight loss of 10% or more was associated with several indicators of poor health, including physical disability, low mental status score, and low physical activity (P<.05). Weight gain of 10% or more beginning at age 50 years provided borderline protection against the risk of hip fracture (relative risk, 0.4; 95% confidence interval, 0.1-1.00). CONCLUSIONS: Despite differences between older men and women in the incidence of and risk factors for hip fracture, weight history is also an important determinant of the risk of hip fracture among older men. Weight loss of 10% or more beginning at age 50 years increases the risk of hip fracture in older white men; weight gain of 10% or more decreases the risk of hip fracture. The relationship between extreme weight loss and poor health suggests that weight loss is a marker of frailty that may increase the risk of hip fracture in older men. Physicians should include weight history in their assessment of the risk of hip fracture among older men.  相似文献   
164.
165.
Twenty-one chronic schizophrenics were stabilized with chlorpromazine therapy at their therapeutic dosage for one month. Trihexyphenidyl hydrochloride or identical placebo was then added according to a double-blind, split crossover design. The duration of each half of the crossover was 15 days. Steady state blood samples were drawn three times weekly during the experimental period and the amount of chlorpromazine was determined. The results indicated there were no differences in the levels obtained between the trihexyphenidyl and the placebo phases. A two-hour postdrug blood sample was also drawn at the end of each phase and again, there were no differences between the two conditions. The importance of these results is discussed.  相似文献   
166.
Including controls, 978 mice were studied. On days corresponding to days 6 through 14 of pregnancy, groups of pregnant and nonpregnant CD-1 mice and male and nonpregnant female dihybrid cross F2 mice received by gavage 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) ranging in dosage from 30 to 140 mg/kg. Some groups received a technical preparation containing 97.9 +/- 0.4% 2,4,5-T and some a purified preparation containing 99 +/- 0.3% 2,4,5-T. Mice were sacrificed when they became moribund and at 1, 2, 4, 6, 8, and 11 days after beginning treatment. Sick or moribund mice sacrificed after 2-9 doses of 2,4,5-T often showed severe myocardial lesions, hypocellularlity of the bone marrow, and depletion of lymphocytes in the thymus, spleen or lymph nodes. They also showed marked hematologic and blood chemistry changes. Treated mice remaining healthy showed few or no lesions or blood chemistry changes, but often developed a mild anemia attributable to a hemolytic effect of 2,4,5-T. The incidence of animals becoming moribund was less than 1% in the CD-1 mice, including those given 140 mg/kg, and 53-82% in groups of male and female F2 mice receiving 120 mg/kg 2,4,5-T. The incidence of moribund mice tended to be higher in male than in female F2 mice and in those given the purified compound. These findings indicate that impairment of maternal health by severe lesions early in gestation is not the primary cause of an increase in incidence of fetal abnormalities observed in mice given 2,4,5-t. they also indicate that the lesions are due primarily to 2,4,5-T, rather than contaminants in the technical preparation, and illustrate the importance of using more than one strain of mouse in a toxicologic or teratologic study.  相似文献   
167.
Lipids were extracted from the lyophylized free-living planariae P. sibirica according to the procedure of Folch et al. [14] and fractionated by means of thin-layer and column chromatography on the silicagel KSK. Total lipid content of planariae is equal to 28.70% of lyophylized weight, 21.70% of them being presented by phospholipids. Polar lipids include phosphatidylethanolamine, phosphatidylcholine, sphingomyelin, lysophosphatidylcholine and cerebrosides. Neutral lipids are presented by triglycerides, cholesterol cholesterol esters and free fatty acids. Saturated and unsaturated C6--C22 fatty acis were detected in the lipids.  相似文献   
168.
1. The time course of changes in specific activities of citrate, lactose and fatty acids in milk during frequent milking, following the I.V. administration of labelled glucose, acetate and chylomicrons in goats has been studied. Peak specific activities of lactose and citrate in milk were reached at 2-3 hr, while peak specific activites of fatty acids were reached at 5-7 hr. 2. Following short I.A. infusions of 24Na, 36Cl, and 42K, peak specific activities in milk were reached in 1 hr or less. 3. The mammary epithelium of lactating goats was found to be virtually impermeable to labelled citrate in both directions. 4. Labelled citrate had an apparent volume of distribution in lactating guinea-pigs mammary slices in vitro similar to that of extracellular space markers. 5. Treatment of goats with large doses of oxytocin markedly increased the permeability of the secretory epithelium to labelled citrate. 6. In the goat mammary gland, citrate, protein and calcium failed to enter milk which had been diluted with isosmotic lactose by intraductal injection, whereas Na, K and Cl did enter, thus tending to restore the concentrations of these ions to normal. 7. It is suggested that citrate, which is formed within the sucretory cell, enters milk not by passage across the apical cell membrane but, in common with lactose and milk protein, by exocytosis of Golgi vesicles. It appears that citrate is held at high concentrations in milk by virtue of the impermeability of the mammary epithelium to the forms in which it occurs in milk.  相似文献   
169.
170.
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