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   2699942篇
  免费   199668篇
  国内免费   7591篇
耳鼻咽喉   35342篇
儿科学   88626篇
妇产科学   73453篇
基础医学   388123篇
口腔科学   77113篇
临床医学   252232篇
内科学   521699篇
皮肤病学   58321篇
神经病学   215863篇
特种医学   100056篇
外国民族医学   594篇
外科学   395102篇
综合类   62593篇
现状与发展   6篇
一般理论   948篇
预防医学   214541篇
眼科学   62817篇
药学   198837篇
  16篇
中国医学   7165篇
肿瘤学   153754篇
  2021年   21334篇
  2019年   22251篇
  2018年   31827篇
  2017年   24156篇
  2016年   26447篇
  2015年   30183篇
  2014年   41809篇
  2013年   62534篇
  2012年   86203篇
  2011年   91129篇
  2010年   53827篇
  2009年   49923篇
  2008年   84047篇
  2007年   89181篇
  2006年   89762篇
  2005年   86084篇
  2004年   82596篇
  2003年   78598篇
  2002年   76080篇
  2001年   131372篇
  2000年   134682篇
  1999年   112203篇
  1998年   30706篇
  1997年   27140篇
  1996年   27049篇
  1995年   25860篇
  1994年   23961篇
  1993年   22241篇
  1992年   86793篇
  1991年   84221篇
  1990年   81151篇
  1989年   77692篇
  1988年   71317篇
  1987年   69688篇
  1986年   66065篇
  1985年   62852篇
  1984年   46706篇
  1983年   39786篇
  1982年   23029篇
  1979年   41806篇
  1978年   29323篇
  1977年   24534篇
  1976年   23320篇
  1975年   24297篇
  1974年   29578篇
  1973年   28692篇
  1972年   26613篇
  1971年   24688篇
  1970年   22957篇
  1969年   21265篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
BACKGROUND: The aim was to determine the influence of the socioeconomic status of the family and the hygienic practices in the home on the prevalence of head lice infestation in children. METHODS: The study was carried out by analyzing the answers to a standardized epidemiological questionnaire given to parents of school children aged 4-17 in Bet Shemesh, a medium-sized urban town 25 km from Jerusalem. RESULTS: Of 3,000 questionnaires distributed, 958 (31.9%) were completed and returned. The majority of the children (72.4%) had been previously infested with lice. Half of them had other family members, mainly brothers and sisters, who had been infested in the past with lice. In 97.5% of the families the mother was responsible for examining the children for lice, and for carrying out treatment when infestation was present. An association was found between presence of lice infestation and mother's education, age of child, and frequency of shampooing, combing, and examination for lice. There was no association between infestation rates and mother's country of origin, crowding in the home, and the sharing of combs, brushes, hats, scarves, towels, and clothes. CONCLUSIONS: There is evidence that the incidence of lice infestation depends on the hygienic practices in the home rather than on the socioeconomic status of the family or sharing of personal articles among family members.  相似文献   
992.
We report herein, a new method devised of producing neurogenic stress ulceration in rats. An experimental subarachnoid hemorrhage (SAH) was produced in rats by injecting 0.2 ml of arterial blood from other rats into the cisterna magna. Three days later, the rats were laparotomized for 1 hour under ether anesthesia, followed by restraint for 3 hours in wakefulness. The SAH rats were found to develop stress ulcers (UL-I) in the glandular stomach, which were significantly (p less than 0.001) more marked than those in non-SAH rats. Measurements were performed on gastric acid secretion, an important aggressive factor. It was found that the SAH rats undergoing the laparotomy-restraint stress showed a more marked increase in gastric acid secretion and a more marked reduction in MBF, than the non-SAH rats. The effects of bilateral vagotomy, upper abdominal sympathectomy and bilateral adrenalectomy were examined, and it was revealed that the SAH rats were under the condition of hyperreactivity both in the sympathetic and parasympathetic systems and, on this basis, the laparotomy-restraint stress caused the stress gastric ulceration. In this rat model, the laparotomy stress was applied under anesthesia and any exposure to low temperatures which may have interfered with blood circulation was avoided.  相似文献   
993.
Computed tomography and nonoperative treatment for blunt abdominal trauma   总被引:1,自引:0,他引:1  
Studies were undertaken to determine if computed tomography (CT) could reliably assist physical examination in the initial assessment of blunt abdominal trauma, and also to examine how various abdominal injuries were managed with the guidance of CT. A total of 255 patients underwent emergency abdominal CT following blunt abdominal trauma over a period of seven years. One hundred and fifty two patients had abnormal CT scans, including 58 hepatic, 36 renal, 25 splenic and 9 pancreatic injuries as well as 67 patients with intra-abdominal hemorrhage and 21 patients with free abdominal air. A comparative study on the detection of pneumoperitoneum revealed CT to be far superior to plain radiography. One hundred and three patients had normal CT scans, all of whom were managed nonoperatively, except for three false-negative cases and two nontherapeutic cases. The patients with injury to the parenchymal organs were given nonoperative treatment if they had stable vital signs and no evidence of associated injuries demanding immediate surgery and the majority of these patients were managed well nonoperatively. CT was thus found to be a useful adjunct in the management of victims of blunt abdominal trauma, since in a rapid and noninvasive fashion, CT accurately defined the extent of parenchymal organ injury and also disclosed any other abdominal injuries.  相似文献   
994.
Assessment of glomerular filtration rate (GFR) with inulin is cumbersome and time-consuming. Radioisotopic filtration markers have been studied as filtration markers because they can be used without continuous intravenous (IV) infusion and because analysis is relatively simple. Although the clearances of 99mTc-diethylenetriamine-pentaacetic acid (DTPA), 169Yb-DTPA, and 125I-iothalamate have each been compared with inulin, rarely has the comparability of radioisotopic filtration markers been directly evaluated in the same subject. To this purpose, we determined the renal clearance of inulin administered by continuous infusion and the above radioisotopic filtration markers administered as bolus injections, simultaneously in four subjects with normal renal function and 16 subjects with renal insufficiency. Subjects were studied twice in order to assess within-study and between-study variability. Unlabeled iothalamate was infused during the second half of each study to assess its effect on clearances. We found that renal clearance of 125I-iothalamate and 169Yb-DTPA significantly exceeded clearance of inulin in patients with renal insufficiency, but only by several mL.min-1.1.73m-2. Overestimation of inulin clearance by radioisotopic filtration markers was found in all normal subjects. No differences between markers were found in the coefficient of variation of clearances either between periods on a given study day (within-day variability) or between the two study days (between-day variability). The true test variability between days did not correlate with within-test variability. We conclude that the renal clearance of 99mTc-DTPA, 169Yb-DTPA, or 125I-iothalamate administered as a single IV or subcutaneous injection can be used to accurately measure GFR in subjects with renal insufficiency; use of the single injection technique may overestimate GFR in normal subjects.  相似文献   
995.
The effect of dietary vomitoxin on the serum IgA and IgG responses to two model intestinal antigens, casein and cholera toxin (CT), were assessed in 4 experimental groups: (1) mice fed casein-based diet, (2) mice fed casein-based diet containing 25 ppm vomitoxin, (3) mice fed casein-based diet and immunized with CT, and (4) mice fed casein-based diet containing 25 ppm vomitoxin and immunized with CT. Unimmunized and CT-immunized mice that were fed vomitoxin exhibited increased levels of total serum IgA relative to matched control animals fed the standard diet. Relative concentrations of casein-specific IgA were greater in both unimmunized mice and CT-immunized mice fed standard diet with vomitoxin than in matched controls fed standard diet only. CT-specific serum IgA in CT-immunized mice was not affected by vomitoxin feeding, but relative levels of CT-specific IgA were higher in unimmunized mice fed vomitoxin than in unimmunized mice fed standard diet. Both casein- and CT-specific serum IgG were depressed in mice fed vomitoxin. Significant differences in total, casein-specific and CT-specific IgA within the intestinal contents were not observed between CT-immunized mice fed vomitoxin and those fed the control diet. The results suggest that vomitoxin altered regulation of the normal immunoglobulin response to intestinal antigens and that this was manifested in the systemic compartment.  相似文献   
996.
The effect of metronidazole on TPN-associated liver dysfunction in neonates   总被引:3,自引:0,他引:3  
The effect of metronidazole (MNZ) on hepatic dysfunction associated with total parenteral nutrition (TPN) in neonates was investigated. Neonates receiving TPN for more than 2 weeks were divided into three groups. In group 1, TPN was given alone, in group 2, 25 mg/kg/d of MNZ was administered intravenously for the first 2 weeks of TPN, and in group 3, 50 mg/kg/d of MNZ was given for the first 3 weeks of TPN. Several parameters of liver function tests (LFTs) during the first 4 weeks of TPN were compared among these three groups. There was no significant difference of these parameters between group 1 and group 2. Although there was no significant difference of alkaline phosphatase, gamma-glutamyl transpeptidase, direct bilirubin, and total bile acid between groups 1 and 3, transaminase (glutamic oxaloacetic, glutamic pyruvic) of group 3 remained significantly lower than those of group 1. In conclusion, the administration of MNZ 50 mg/kg/d for 3 weeks, at least, prevented the elevation of transaminase during TPN in neonates, suggesting the possible involvement of intestinal anaerobic flora in the pathogenesis of TPN-associated liver dysfunction.  相似文献   
997.
Since 1987, 80 hydroxyapatite-coated (HA) cementless total hip prostheses have been implanted. Thirty patients were examined 21 months postoperatively and the results compared with data for uncoated prosthesis. Earlier mobilization and freedom from pain, together with evidence of bone ingrowth without connective tissue membrane formation, confirmed the benefits of HA-coated prostheses.  相似文献   
998.
Summary Eight patients with malignant gliomas verified on CT scan, received an intravenous injection of 50 mg of Adriamycin R, 24 hours prior to surgical removal of the tumour. Peroperatively, both tumour and surrounding tissue specimens were obtained for determination of the tissue concentrations of Adriamycin and its reduced metabolite Adriamycinol. It was found that Adriamycin could be detected in tumour tissue from all patients. The concentration varied between 0,9 and 4,6 nmol/g tissue. In contrast, Adriamycin could only be detected in surrounding brain tissue from one patient.In anin vitro study a human malignant glioma cell line (U-251 MG) was exposed to various concentrations of Adriamycin for 24 hours. It was found that an intracellular drug concentration above 30 nmol/g cells caused a concentration dependent inhibition of cell growth. Thus, it is likely that the poor effect of Adriamycin on patients with malignant gliomas is due to an ineffective drug accumulation in the tumour tissue.  相似文献   
999.
In a retrospective study, 217 patients with conservatively treated adolescent idiopathic scoliosis (AIS) were investigated. Forty-nine cases were operated and 168 were treated only conservatively and had been out of the brace for at least 4 years at the time of the investigation. The progression between cessation of brace treatment and follow-up (a mean of 6.9 years later) was 5.1 degrees. Almost all progression (4.5 degrees) occurred within 2 years of the end of weaning, however. The incidence of failure with regard to the length of follow-up was also studied. A follow-up of 2 years was sufficient to predict with great accuracy (97%) all incidences of failure.  相似文献   
1000.
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