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   298789篇
  免费   17774篇
  国内免费   419篇
耳鼻咽喉   4240篇
儿科学   10342篇
妇产科学   10297篇
基础医学   45309篇
口腔科学   7887篇
临床医学   24450篇
内科学   56400篇
皮肤病学   6392篇
神经病学   21155篇
特种医学   11684篇
外国民族医学   43篇
外科学   47016篇
综合类   7778篇
现状与发展   1篇
一般理论   160篇
预防医学   20292篇
眼科学   6975篇
药学   21060篇
中国医学   806篇
肿瘤学   14695篇
  2021年   2350篇
  2018年   3743篇
  2017年   2728篇
  2016年   3176篇
  2015年   3609篇
  2014年   4711篇
  2013年   7415篇
  2012年   9277篇
  2011年   9696篇
  2010年   6260篇
  2009年   5664篇
  2008年   8807篇
  2007年   9660篇
  2006年   9479篇
  2005年   9070篇
  2004年   8771篇
  2003年   8250篇
  2002年   7831篇
  2001年   13376篇
  2000年   13684篇
  1999年   11455篇
  1998年   3037篇
  1997年   2799篇
  1996年   2642篇
  1995年   2547篇
  1994年   2356篇
  1992年   8335篇
  1991年   8477篇
  1990年   8270篇
  1989年   8088篇
  1988年   7335篇
  1987年   7079篇
  1986年   6726篇
  1985年   6532篇
  1984年   4772篇
  1983年   4128篇
  1982年   2471篇
  1979年   4438篇
  1978年   3235篇
  1977年   2735篇
  1976年   2511篇
  1975年   2836篇
  1974年   3357篇
  1973年   3368篇
  1972年   3119篇
  1971年   2950篇
  1970年   2844篇
  1969年   2586篇
  1968年   2541篇
  1967年   2377篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Thirty patients with malignant tumours in the upper abdomen underwent surgery and intraoperalive radiation (IORT), using electron beam, to: the surgical bed, residual or unresected tumour. The technical aspects and results of this treatment are described. Renal, adrenal, bile duct and gastrointestinal tumours were treated. along with several other lesions. The surgical procedure consisted in 10 cases simply of exposure of the tumour for IORT and in 20 the tumour was resected. The TORT dose ranged from 10 to: 20 Gv. In 13 patients, external beam radiation was also given to: residual tumour or to: areas of high risk for recurrence. Chemotherapy was given to: 10 patients. Tolerance to: the combined treatment was acceptable; with few complications related to: IORT.The median follow-up and survival time 23 months (range 4-more than 70 months). Local tumour control rate (or tumour stabilisation) is 90%. Distant metastases developed in 19 patients (63%). The actuarial survival rate for the group projected at 70 months (maximum follow-up) is 37%. IORT in useful in the management of tumours arising in the upper abdominal organs, for palliation surgery or when resectability of the tumour is in doubt. Indications for IORT include patients with uncommon tumours of the upper abdomen who are not be candidates for standardised cancer treatment.Presented at the European Congress of Radiology, Vienna, September 15–20,1991  相似文献   
992.
Recent studies have shown that proto–oncogene c–fos mRNA is induced in the central nervous system by a variety of stimuli including generalised convulsions. In this study, the expression of c–fos protein (c–Fos) following lignocaine–induced convulsions was examined and compared with that following convulsions induced by non–anesthetic convulsants, such as pentylenetetrazol, kainic acid and electroconvulsive shocks, in rat brain.
Administration of 120 mg kg-1 lignocaine by the intraperitoneal route induced generalised convulsions in all rats examined within 10 min. C–Fos was markedly induced in the piriform cortex and amygdala, and slightly induced in the neocortex and thalamus, while no c–Fos expression was observed in the hippocampus. In contrast, c–Fos expression following generalised convulsions induced by non–anaesthetic convulsants was very marked in the hippocampal region, piriform cortex and amygdala, and extended to the thalamus and neocortex.
These results contradict those of previously reported local cerebral metabolic studies using 2–deoxyglucose as a metabolic marker, and suggest that lignocaine–induced convulsions, unlike those induced by non–anaesthetic convulsants, may not cause severe sequelae (plastic changes) in the hippocampus.  相似文献   
993.
Xenon is a more potent anesthetic than nitrous oxide, and gives more profound analgesia. This investigation was performed to assess the potential of xenon for becoming an anesthetic inspite of its high manufacturing cost. Seven ASA I—-II patients undergoing cholecystectomy (n = 4), hernia repair (n = 2), or mammoplasty (n=l) were studied. Denitrogenation by 15–20 min of oxygen breathing under propofol anesthesia was followed by fentanyl–supplemented xenon anesthesia administered via an automatic minimal flow system which held the oxygen concentration at 30%. Xenon anesthesia lasted 76–228 min and 8–14 1 of xenon (ATPD) was used, of which 5.6–8.1 1 was expended during the first 15 min. Anesthesia appeared to be satisfactory, and the patients woke up rapidly after xenon was discontinued. The automatic system made minimal flow xenon anesthesia easy to administer, but nitrogen accumulation is still a problem. Assuming a xenon price of 10 US $ per litre, the average cost for xenon was about 65 US $ for the first 15 min and then about 25 USS for each subsequent hour of anesthesia.  相似文献   
994.
Altogether twenty-six elderly subjects (aged 65-74 years) with persistent impaired glucose tolerance (World Health Organization (1985) criteria) identified in a population-based study, were randomly treated either with chromium-rich yeast (160 micrograms Cr/d) or with placebo for 6 months. The 24 h urinary Cr increased from 0.13 (SE 0.03) to 0.40 (SE 0.06) micrograms/d in the Cr group (n 13) but no change was found in the placebo group (n 11) (0.13 (SE 0.02) v. 0.11 (SE 0.02) micrograms/d). No significant change was observed in the oral glucose tolerance test (glucose dose 75 g; 0, 1 and 2 h blood glucose respectively): 5.3 (SE 0.1), 9.3 (SE 0.3), 8.2 (SE 0.3) mmol/l v. 5.0 (SE 0.1), 8.5 (SE 0.4), 7.3(SE 0.5) mmol/l in the Cr group; 4.9 (SE 0.2), 9.2 (SE 0.6), 8.1 (SE 0.3) mmol/l v. 4.8 (SE 0.2), 8.5 (SE 0.5), 7.0 (SE 0.6) mmol/l in the placebo group (baseline v. 6 months). Glycosylated haemoglobin, plasma insulin, C-peptide and apolipoprotein A1 and B levels remained unchanged, and no improvement was seen in serum total cholesterol (6.2 (SE 0.3) v. 6.4 (SE 0.3) mmol/l for the Cr group, 6.2 (SE 0.4) v. 6.5 (SE 0.3) mmol/l for the placebo group), high-density-lipoprotein-cholesterol (1.1 (SE 0.1) v. 1.2 (SE 0.1) mmol/l for the Cr group, 1.0 (SE 0.1) v. 1.1 (SE 0.1) mmol/l for the placebo group) or triacylglycerols (2.5 (SE 0.4) v. 2.0 (SE 0.4) mmol/l for the Cr group, 2.4 (SE 0.2) v. 2.5 (SE 0.2) mmol/l for the placebo group). The present results indicate that Cr supplementation does not improve glucose tolerance or serum lipid levels in elderly subjects with stable impaired glucose tolerance.  相似文献   
995.
S Ferro  A Caroli  O Nanni  A Biggeri  A Gambi 《Tumori》1992,78(2):98-105
In 1988, a cross-sectional survey was carried out in the Romagna region (Italy) to evaluate the association between knowledge of breast pathophysiology and preventive attitudes and screening tests practice for breast cancer. A self-administered questionnaire was distributed to a sample of asymptomatic women aged 20-64 years living in the city of Faenza (Northern Italy). Of the 657 responders, 58% reported that they practiced breast self-examination; 55% had had a professional breast examination, and only 9% had had a mammogram as a screening test. Logistic regression analysis (including variables such as age, education, employment) was performed to explore the relationship between screening tests practice and factors associated with their use. Breast self-examination practice (n = 590) was associated with preventive attitudes (aOR = 1.67, 95% CI = 1.09-2.53) and with a positive history of breast disease (aOR = 3.48, 95% CI = 1.72-7.04). Professional breast examination (n = 480) was related to preventive attitudes (aOR = 2.37, 95% CI = 1.51-3.71), knowledge of breast pathophysiology (aOR = 2.07, 95% CI = 1.31-3.28), and use of oral contraceptives (aOR = 1.81, 95% CI = 1.12-2.91). Mammography use (n = 540) was associated with preventive attitudes (aOR = 3.08, 95% CI = 1.40-6.76). The results show an inadequate utilization of screening tests in our population. Breast self-examination is strongly related to a positive history of breast disease, and this could reflect the lack of health educational programs aimed at the general population.  相似文献   
996.
Neutropenic enterocolitis. Clinical diagnosis and treatment.   总被引:6,自引:0,他引:6  
D S Wade  H R Nava  H O Douglass 《Cancer》1992,69(1):17-23
Review of the consultation records of the Gastrointestinal Surgical Oncology service at Roswell Park Memorial Institute from 1982 to 1987 revealed 22 patients with a clinical diagnosis of neutropenic enterocolitis. Ninety-one percent of the patients had hematologic malignancies, and 95% were receiving cytotoxic chemotherapy. Sixteen patients were treated nonsurgically; 11 died. Of those 11 cases, autopsies were performed in 9. At autopsy, the clinical diagnosis was confirmed in four cases; four cases were found to have normal intestinal tracts, and one case had a small bowel volvulus. In none of the four cases for which autopsy proved neutropenic enterocolitis was transmural bowel necrosis or perforation found. Laparotomy was performed in six patients; three survived. The clinical diagnosis was verified in four of the six patients. Neutropenic enterocolitis must be considered a diagnosis of exclusion. Care of these patients should be individualized. Nonoperative management with bowel rest, decompression, nutritional support, and broad spectrum antibiotics is recommended initially. Operative intervention is recommended for those with perforation or those whose condition deteriorates clinically during close, frequent observation.  相似文献   
997.
BACKGROUND. This study reports the barriers and challenges for hospital tobacco control efforts after the institution of smoke-free policies. METHODS. Surveys of employees and inpatients of five hospitals in Augusta, Georgia, were conducted and evaluated 4 months after joint hospital implementation of smoke-free policies. A random sample of 1997 employees and a convenience sample of 517 inpatients returned usable surveys. RESULTS. Although attitudes to the hospital bans on smoking reflected strong support for smoke-free policies, four out of five hospitals reported significant implementation problems. Despite the bans, 49% of patients who were smokers continued to smoke while hospitalized, and almost one half of all hospitalized smokers had received no advice to quit smoking from a physician or a nurse since admission. Employees and patients both agreed that the smoke-free policies had benefited employees more than patients. CONCLUSIONS. Despite achieving a smoke-free status, there are many challenges that remain for comprehensive hospital tobacco-control efforts. Hospitals and health care professionals must remain particularly alert and attentive to the needs of patients and employees still addicted to tobacco.  相似文献   
998.
A total of 83 cirrhotic nodules (pseudolobules) individually collected from 11 cirrhotic livers of hepatitis B virus carrier patient were analyzed for the frequency and mode of hepatitis B virus integration as well as histological features. Southern blot analysis disclosed discrete bands at higher molecular weight region in 26 of 83 nodules (31.3%), indicating a clonal growth of hepatocytes with viral integration. Considerable variation (0-75%) existed in the positive rates for discrete bands in nodules among livers. Molecular cloning revealed the sequence flanking an integrated viral sequence to be host DNA and thus confirmed true integration. Histological analysis, however, did not reveal any neoplastic-appearing foci of growth within nodules, despite the fact that the detection sensitivity would predict clones of more than 10(5) cells to give rise to clonal integration patterns on Southern blot analysis. The question of whether clonal expansion of hepatocytes reflects any viral integration-associated growth advantage and/or a preneoplastic condition awaits future studies.  相似文献   
999.
1000.
Effects of nicotine and ethanol on rat atrial membrane potentials.   总被引:2,自引:0,他引:2  
The purpose of this research was to study the effects of nicotine and ethanol, alone and in combination, on cardiac membrane potentials (MP). Rat atrial preparations driven at 5 Hz were superfused with Tyrode's solution (37 degrees C) while recording MP with intracellular microelectrodes. Nicotine concentrations below and including 6.2 x 10(-5) M did not affect MP. Within 15 s, nicotine 3.1 x 10(-3) M shortened the action potential duration (APD) and depressed the overshoot of the action potential (OS). This action was blocked by atropine. After 3 min, nicotine prolonged the APD and depressed Vmax of phase O, OS and the amplitude of the action potential (AAP), without affecting the resting membrane potential (RMP). Nifedipine blocked the depression of the OS while tetraethylammonium chloride blocked the prolongation of the APD. Acute exposure to ethanol depressed OS and AAP and shortened APD, but it did not affect RMP or Vmax of phase O. When nicotine and ethanol were administered simultaneously, the APD-prolonging effects of nicotine prevailed. The influence of chronic ethanol ingestion on the acute action of nicotine and/or ethanol was studied in rats pair-fed a liquid diet with (ER) or without (NR) ethanol (35% of total caloric intake) for 24 weeks. Chronic ethanol ingestion accentuated the depressant effect of nicotine 3.1 x 10(-3) M on OS and AAP, but it did not modify the APD-prolonging action of nicotine. The same results were observed when ER and NR were exposed to nicotine and ethanol simultaneously.  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