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   126033篇
  免费   9117篇
  国内免费   213篇
耳鼻咽喉   1138篇
儿科学   3475篇
妇产科学   2595篇
基础医学   19639篇
口腔科学   3320篇
临床医学   10647篇
内科学   25575篇
皮肤病学   2173篇
神经病学   12110篇
特种医学   5331篇
外国民族医学   9篇
外科学   15769篇
综合类   537篇
现状与发展   1篇
一般理论   106篇
预防医学   14390篇
眼科学   1978篇
药学   7374篇
中国医学   235篇
肿瘤学   8961篇
  2023年   539篇
  2022年   896篇
  2021年   1950篇
  2020年   1417篇
  2019年   2058篇
  2018年   2588篇
  2017年   2199篇
  2016年   2388篇
  2015年   2672篇
  2014年   3669篇
  2013年   4781篇
  2012年   7372篇
  2011年   7440篇
  2010年   3863篇
  2009年   4051篇
  2008年   6586篇
  2007年   6806篇
  2006年   6540篇
  2005年   6199篇
  2004年   5290篇
  2003年   4989篇
  2002年   4542篇
  2001年   4436篇
  2000年   4382篇
  1999年   3908篇
  1998年   1632篇
  1997年   1358篇
  1996年   1426篇
  1995年   1165篇
  1994年   1100篇
  1993年   986篇
  1992年   2684篇
  1991年   2405篇
  1990年   2284篇
  1989年   2144篇
  1988年   1975篇
  1987年   1711篇
  1986年   1645篇
  1985年   1574篇
  1984年   1119篇
  1983年   981篇
  1982年   536篇
  1981年   463篇
  1980年   399篇
  1979年   859篇
  1978年   525篇
  1977年   434篇
  1974年   417篇
  1973年   409篇
  1972年   366篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Dabis Maleate (1,4-bis(2'-chloroethyl)-1,4-diazabicyclo[2.2.1] Heptane dihydrogen dimaleate) (NSC 262666) is an alkylating quaternary nitrogen compound. In a previous phase I study using a once-every-3-weeks administration the dose-limiting toxicity was neurotoxicity and the recommended dose for phase II studies was 750 mg/m2 iv every 3 weeks. In vitro studies suggested a higher activity after more frequent administration, and in vivo studies a better therapeutic index with prolonged infusion. We studied 11 patients with solid tumors. Dose levels tested ranged from 250-750 mg/m2, either as a day 1-3 regimen or weekly, the latter as bolus administration or as prolonged infusion. The dose-limiting toxicity was neurotoxicity consisting of paresthesias and ataxia. Nausea and vomiting were moderate. No other major toxicity was observed. The dose recommended for phase II studies is 500 mg/m2/week as a 6-hour iv infusion for 6 weeks, followed by a 3-week rest period.  相似文献   
122.
OBJECTIVE: The purpose of this study was to develop a clinician-based cognitive, psychoeducational, preventive intervention for families with parental affective disorder that would be suitable to widespread use, test its feasibility and safety, and define the areas affected by the intervention. The intervention was designed to increase understanding of parental illness and resilience in the children. METHOD: The authors studied the first seven families (14 parents) to receive the intervention. Enrollment criteria included affective disorder during the preceding year in at least one parent, presence of at least one child between the ages of 8 and 14 years who was not psychiatrically ill at the time of participation, and willingness to participate in the research study. The intervention consisted of parent, child, and family sessions. Assessment included semistructured interviews with parents about affective disorders, standard ratings of marital satisfaction and therapeutic alliance, and a recently developed semistructured interview to assess response to the intervention. RESULTS: Overall satisfaction with the intervention was rated moderate to high by parents. No harm was reported. Ten of 14 parent subjects reported five or more behavior and attitude changes that they attributed to the intervention. The most frequent behavior and attitudinal changes reported were increased discussion of the illness and related issues and increased understanding of information about affective illness. CONCLUSIONS: The authors conclude that the intervention is safe and feasible in families with parental affective disorder.  相似文献   
123.
Background. Chinese herbs nephropathy is a new type of subacute interstitial nephropathy reported in women who had followed a slimming regimen including Chinese herbs. Methods. We report the clinical presentation and follow-up of 15 cases and compare them with a control group of 15 women with interstitial nephropathies of other origins, matched for age, sex, and initial serum creatinine (mean 3 mg/dl). Results. At presentation the Chinese herbs nephropathy group differed from the control group by a lower proteinuria (P=0.009), a more severe anaemia (P=0.002), and a higher prevalence of aortic insufficiency (42% vs 0%, P <0.005). It was further characterized by mild hypertension in 80%, glycosuria and leukocyturia in 40% and asymmetric kidneys in 43% of the cases. During follow-up, deterioration of renal function was faster in the Chinese herbs nephropathy than in the control group (P <0.05). It was influenced by the duration of Chinese herbs treatment (P=0.037) and the delay between the end of Chinese herbs ingestion and diagnosis of the disease (P-0.013). In three cases, renal failure developed 3 years after Chinese herbs ingestion. Complications included severe aortic regurgitation requiring surgery (n=1), urothelial carcinoma (n=2), bilateral ureterohydronephrosis due to periureteral fibrosis (n=1). Five patients with Chinese herbs nephropathy were successfully transplanted, without evidence of recurrence of the disease. Conclusion. Chinese herbs nephropathy is characterized by a lower proteinuria, more severe anaemia, and a faster progression of renal failure than other interstitial nephropathies. The duration of Chinese herbs treatment and interval between withdrawal of Chinese herbs and diagnosis are correlated with the rate of progression. Severe, unusual extrarenal complications may affect Chinese herbs nephropathy patients.  相似文献   
124.
In order to study the correlation between HLA mismatches and the cytotoxic T lymphocyte precursor frequency, we used a limiting dilution analysis to determine the CTLp frequencies against individual mismatched HLA-A and -B alloantigens in 21 patients waiting for a renal transplant. Altogether, thirty-three mismatched HLA-A antigens and 55 HLA-B antigens were tested. The CTLp frequencies against mismatches of HLA-B locus antigens were found to be significantly higher than those against HLA-A antigens (P less than 0.002). This may explain why matching for HLA-B antigens is more important for a good renal allograft survival than matching for HLA-A antigens.  相似文献   
125.
There remains doubt about the need for gastroenterostomy in patients with advanced cancer of the pancreatic head, performed either prophylactically or when passage of food becomes impossible. The records of 142 patients admitted for advanced pancreatic cancer to the Erasmus University Hospital over a period of 11 years were reviewed. We concentrated especially on the pre- and postoperative intake of food in cases involving gastroenterostomy and the morbidity and mortality associated with abdominal surgery in these patients. Of 129 patients without symptoms of gastric outlet obstruction at the time of diagnosis, 31 underwent prophylactic gastroenterostomy. The procedure did not prevent gastric outlet obstruction in 4 patients. Of the remaining 98 patients, 15 developed gastric outlet obstruction. Cox proportional hazards analysis showed no significant difference in the interval to the occurrence of a symptomatic obstruction between these two groups, taking into account other covariables. Postoperative complications and mortality regarding a gastroenterostomy were high, ranging from 9% to 41% and 11% to 33%, respectively. Our results do not indicate that prophylactic gastroenterostomy may significantly prevent future gastric outlet obstruction; therefore, as it also increases morbidity, it should not be performed. A gastroenterostomy to relieve symptoms should be considered carefully, as the success rate is low and is accompanied by a considerable incidence of morbidity and mortality.
Resumen Persiste la duda sobre la necesidad de practicar gastroenterostomía en pacientes con cáncer avanzado de la cabeza del páncreas, así sea profiláctica o en presencia de obstrucción al paso de los alimentos. Se revisaron las historias de 142 pacientes con cáncer avanzado de la cabeza del páncreas en el Hospital de la Universidad de Erasmo observados en un periodo de 11 años. El estudio se concentré especialmente sobre la ingesta pre y postoperatoria de alimentos en los pacientos con gastroenterostomía y en la morbilidad y mortalidad asociada con la cirugía abdominal. De 129 pacientes libres de síntomas de obstrucción en el momento del diagnóstico, 31 fueron sometidos a gastroenterostomía profiláctica; el procedimiento no logró prevenir la obstrucción gástrica en 4 casos. De los 98 pacientes restantes, 15 desarrollaron obstrucción gástrico. El análisis proporcional de Cox no demostró diferencia significativa en el intervalo transcurrido hasta la aparición de los sintomas entre los dos grupos, tomando en consideración diversas variables. Las tasas de complicaciones y de mortalidad postoperatoria en relación con la gastroenterostomía fueron elevadas, 9–41% y 11–33%, respectivamente. Nuestros resultados no indican que la gastroenterostomía profiláctica pueda prevenir la obstrucción gástrica y, por cuanto incrementa la morbilidad, no debe ser realizada. La gastroenterostomía por razones de sintomatologia debe ser cuidadosamente considerada, puesto que la tasa de éxito es baja y se acompana de considerable morbilidad y mortalidad.

Résumé Réaliser une gastroentérostomie de faÇon prophylactique ou seulement lorsque l'alimentation devient impossible chez un patient ayant un cancer de la tÊte du pancréas reste une question sans réponse. Les dossiers de 142 patients ayant un cancer avancé de la tÊte du pancréas, observés à l'HÔpital Universitaire Erasmus en l'espace de 11 ans, ont été revus. Nous avons noté la possibilité d'alimentation en périodes préet postopératoire ainsi que la morbidité et mortalité en rapport avec la chirurgie chez ces patients. Des 129 patients n'ayant pas de symptÔmes d'obstruction postpylorique au moment du diagnostic, 31 ont eu une gastroentérostomie à titre prophylactique. Cette intervention n'a pu prévenir l'obstruction chez 4 de ces patients. Des 98 autres patients, 15 ont développé une obstruction postpylorique. Une analyse multifactorielle selon le modèle de Cox n'a pu démontrer de différence significative entre les deux groupes pour l'intervalle entre le moment du diagnostic et la survenue de l'obstruction. Le taux de complications et de décès postopératoires après gastroentérostomie était élevée, variant respectivement entre 9% et 41% et 11% et 33%. Nos résultats indiquent que la gastroentérostomie à titre prophylactique ne prévient pas la survenue d'une obstruction postpylorique mais qu'elle accroÎt la morbidité. Dans ces conditions, la gastroentérostomie ne devrait Être réalisée qu'en cas d'obstruction symptomatique, mais en sachant qu'elle n'est pas toujours couronnée de succès et que les taux de mortalité et de morbidité ne sont pas nuls.
  相似文献   
126.
127.
128.
Separate exposures to 0.12 ppm ozone (O3) or 0.18 ppm nitrogen dioxide (NO2) have not demonstrated consistent changes in pulmonary function in adolescent subjects. However, in polluted urban air, O3 and NO2 occur in combination. Therefore, this project was designed to investigate the pulmonary effects of combined O3 and NO2 exposures during intermittent exercise in adolescent subjects. Twelve healthy and twelve well-characterized asthmatic adolescent subjects were exposed randomly to clean air or 0.12 ppm O3 and 0.30 ppm NO2 alone or in combination during 60 minutes of intermittent moderate exercise (32.5 1/min). The inhalation exposures were carried out while the subjects breathed on a rubber mouthpiece with nose clips in place. The following pulmonary functional values were measured before and after exposure: peak flow, total respiratory resistance, maximal flow at 50 and 75 percent of expired vital capacity, forced expiratory volume in one second and forced vital capacity (FVC). Statistical significance of pulmonary function changes was tested by analysis of covariance for repeated measures. After exposure to 0.12 ppm O3 a significant decrease was seen in maximal flow at 50% of FVC in asthmatic subjects. After exposure to 0.30 ppm NO2 a significant decrease was seen in FVC also in the asthmatic subjects. One possible explanation for these changes is the multiple comparison effect. No significant changes in any parameters were seen in the asthmatic subjects after the combined O3-NO2 exposure or in the healthy subjects after any of the exposures.  相似文献   
129.
Myocardial biopsies were obtained from 27 patients undergoing corrective cardiac surgery for congenital heart disease. Normal hearts of 18 autopsied patients were used as reference. The biopsy material was assessed for desoxyribonucleic acid (DNA) concentration and ploidy profile of cell nuclei in order to quantitate myocardial hypertrophy at the time of operation. DNA-concentration decreased significantly with age (r = -0.76; p less than 0.001). Ploidy profile of myocardial nuclei correlated with age: the relative number of diploid nuclei decreased (r = -0.67; p less than 0.001), the relative numbers of tetraploid and octoploid nuclei increased with age (r = 0.58; p less than 0.01 and r = 0.77; p less than 0.001 respectively). At 8 years of age the patients with congenital heart disease reached myocardial DNA-concentrations comparable with those in normal adult hearts. At higher age the patients with congenital heart disease exceeded normal adult values for myocardial DNA-concentration. These findings are interpreted to represent rapid development of hypertrophy with an early onset, reaching at 8 years of age values observed in normal adult hearts. Quantitation of myocardial hypertrophy by DNA-concentration and ploidy profile of nuclei may offer a means to explain some of the factors of influence on the outcome of corrective cardiac surgery for congenital heart disease in relation to its timing. Our data stress the need for preventing irreversible myocardial damage by timely (surgical) therapy.  相似文献   
130.
Some studies on energy metabolism of men and women in Third World countries suggested that their basal metabolic rate (BMR) is lower compared to BMRs of people in Northern European and American countries. It is, however, not clear whether this results from ethnic factors, climate or adaptation to, for instance, a low energy intake. A study on energy requirements of people from Third World countries has therefore been performed. People with different ethnic backgrounds participated; they were divided into four ethnic groups: 8 African males, 7 Asian males of Mongolian origin (Asian-M), 8 Asian males of Caucasian origin (Asian-C) and 7 European males, who formed the control group. The participants from outside Europe had spent at least 3 months in the Netherlands. All participants consumed a diet (12 per cent of energy from protein, 22 per cent from fat and 66 per cent from carbohydrate) during 8 d. The dietary energy given to each individual was estimated to maintain energy equilibrium during the experiment. The last 3 nights and 2 days were spent in an indirect whole-body calorimeter. Two 24-h energy expenditure (24hEE) measurements were performed on each subject. The environmental temperature inside the calorimeter was 22.0-24.5 degrees C. Physical activity was light, mainly sedentary, with 75 min bicycling at 15 W. The Asian subjects had a significantly lower body weight and fat-free mass than the Europeans. Energy requirement (ER), 24hEE and EE during the night (8 h sleep) was lower in the Asian and African subjects compared to the Europeans, but the difference only reached significance for the Asian-C and African males. When ER, 24hEE and EE-night were expressed in relation to body weight and fat-free mass the Asian groups showed a higher ER and higher EE than the Europeans. This result is contrary to findings of others and may be caused eg, by a higher body weight and fat-free mass of the European controls. Comparison of EE-night with BMR estimated from FAO/WHO/UNU equations showed that the EE-night was consistently lower by about 9 per cent. This suggests that EE during the night may not be predicted by the BMR estimated by widely used equations. This study does not give conclusive evidence that an ethnic factor is involved in energy metabolism in humans.  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