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   196903篇
  免费   11355篇
  国内免费   561篇
耳鼻咽喉   2467篇
儿科学   6322篇
妇产科学   4118篇
基础医学   26753篇
口腔科学   8129篇
临床医学   14703篇
内科学   44369篇
皮肤病学   5066篇
神经病学   17087篇
特种医学   6068篇
外国民族医学   29篇
外科学   24016篇
综合类   1520篇
现状与发展   1篇
一般理论   70篇
预防医学   19585篇
眼科学   3627篇
药学   12325篇
中国医学   742篇
肿瘤学   11822篇
  2023年   1125篇
  2022年   2557篇
  2021年   4704篇
  2020年   2952篇
  2019年   4187篇
  2018年   5669篇
  2017年   4176篇
  2016年   4021篇
  2015年   4716篇
  2014年   6411篇
  2013年   8131篇
  2012年   12569篇
  2011年   13069篇
  2010年   6756篇
  2009年   5966篇
  2008年   10109篇
  2007年   10668篇
  2006年   9907篇
  2005年   10181篇
  2004年   9473篇
  2003年   8606篇
  2002年   6590篇
  2001年   5457篇
  2000年   5441篇
  1999年   4784篇
  1998年   1741篇
  1997年   1457篇
  1996年   1427篇
  1995年   1207篇
  1994年   1211篇
  1993年   1082篇
  1992年   2962篇
  1991年   2806篇
  1990年   2573篇
  1989年   2524篇
  1988年   2268篇
  1987年   2107篇
  1986年   1989篇
  1985年   1897篇
  1984年   1369篇
  1983年   1093篇
  1982年   620篇
  1981年   565篇
  1980年   541篇
  1979年   1007篇
  1978年   647篇
  1977年   523篇
  1975年   582篇
  1974年   593篇
  1973年   592篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
A series of 1153 fine-needle aspiration biopsies (FNAB) of breast masses obtained during the period 1985 to 1988 in one institution was examined. The following diagnostic accuracy values were found: sensitivity, 93.0%; specificity, 92.4%; predictive positive value, 93.7%; and efficiency, 92.8%. These results were compared with a previously published series for the period 1976 to 1984. The diagnostic accuracy values did not differ significantly between the two series.  相似文献   
133.
134.
135.
A retrospective study was performed to describe the features of the pollinosis caused by Betula in the area of Ourense, Spain. The pollen count was carried out with a Lanzoni volumetric Hirts spore trap (1993-2000). The Betula pollen represented 5% over the annual total (annual mean quantity: 965 grains). It was present in the air from March to mid-May. The highest peaks took place in April (maximum values mean: 131 grains/m3). The medical records of 222 patients (mean age 25.66 years) diagnosed with pollinosis (1998-2000), who lived at less than 30 km. from the spore trap, were reviewed. In all of them, the skin-prick test (SPT) was carried out with pollen allergens. The percentages of positive SPT were: Lolium perenne, 91.89% (16.6% monosensitized); Plantago lanceolata, 71.17% (1.26% monosensitized); Betula alba, 41.89% (10.75% monosensitized); Platanus hybrida, 34.95%; Olea europea, 10.36%; and Parietaria judaica, 6.3%. The mean age of Betula monosensitized patients was 44.7 years. The majority of them had symptoms in March-April, 40% had asthma symptoms, 80% had lived in Central Europe, and 30% of them presented an oral allergy syndrome to fruits. There were 41.93% of the patients with positive SPT to Betula pollen who had asthma symptoms, in comparison with 23.25% of the patients with negative SPT to Betula (p = 0.0034). There were 20.28% of the patients with positive SPT to Betula pollen, who had lived in Central Europe, in comparison with 4.27% of the patients with negative SPT to Betula, p: 0.00049. The relative risk of sensitization was 2.05. CONCLUSIONS: Betula pollen was the second cause of clinical pollinosis in our patients, after grass, being responsible of the symptoms in the early spring, in a small number of the patients in their forties. The presence of asthma was higher in Betula sensitized patients, and the residence in Central Europe was a sensitization risk factor.  相似文献   
136.
137.
Recent advances in cardiovascular applications of magnetic resonance (MR) imaging and phosphorus-31 spectroscopy are reported. MR velocity mapping is a valuable adjunct to conventional imaging techniques, providing information on flow velocities as well as on absolute blood flow volume in the aorta and pulmonary arteries. Recently, ultrafast MR techniques have become available to evaluate myocardial perfusion with the aid of MR contrast agents as perfusion marker. Dynamic MR imaging is a powerful tool to assess cardiac function and ventricular mass. In particular, right ventricular function and mass can be evaluated with great accuracy, contributing to improved assessment of the significance of disease processes which may affect the right heart. The role of phosphorus-31 spectroscopy of the heart is expanding for the evaluation of ischemic myocardial disease and cardiomyopathies. The phosphocreatine to adenosine triphosphate ratio appears to be a marker of disease in patients with cardiac hypertrophy. In conclusion, MR imaging and phosphorus-31 spectroscopy is gaining widespread acceptance for evaluation of many cardiovascular disease processes.  相似文献   
138.
481 pregnant women attended at first consultation from a S?o Paulo city suburb-subdistrict of Butantan-S?o Paulo State, Brazil, from April to October of 1988, were investigated regarding the prevalence of verminosis. The mean age was 24.5 years (range 14-46), the average family income was 0.97 PCMW (per capita minimum wage) and the average number of members of the family was 4 (1 to 15). The verminosis prevalence was 45.1% among the women. The most frequent parasites were: Ascaris lumbricoides (19.0%), ancilostomídeos (16.7%) and Trichuris trichiura (15.9%). The verminosis prevalence was significantly higher among the pregnant women (p < 0.05) who belonged to the families with income below 0.5 PCMW and greater than 4 members.  相似文献   
139.
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   
140.
A girl developed progressive weakness of bulbar and ocular muscles starting before the age of two years. Electromyography revealed a widespread subclinical myopathy. An intercostal muscle biopsy showed complex abnormalities including occasional neurofilamentous accumulations and honeycomb-like membranous material in terminal axons. Endplates were small and some secondary synaptic clefts were abnormally deep. Acetylcholine receptors extended unusually deeply into the clefts of the junctional folds. Muscle fibres showed subsarcolemmal vacuolation at some places. This form of congenital oculo-bulbar palsy does not appear to have been described previously.  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