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   49679篇
  免费   2283篇
  国内免费   269篇
耳鼻咽喉   760篇
儿科学   842篇
妇产科学   812篇
基础医学   6234篇
口腔科学   1535篇
临床医学   3392篇
内科学   12155篇
皮肤病学   604篇
神经病学   4083篇
特种医学   1638篇
外科学   8771篇
综合类   215篇
现状与发展   1篇
一般理论   3篇
预防医学   1712篇
眼科学   782篇
药学   3917篇
中国医学   103篇
肿瘤学   4672篇
  2023年   252篇
  2022年   529篇
  2021年   897篇
  2020年   464篇
  2019年   649篇
  2018年   799篇
  2017年   619篇
  2016年   770篇
  2015年   818篇
  2014年   1104篇
  2013年   1402篇
  2012年   2221篇
  2011年   2397篇
  2010年   1442篇
  2009年   1249篇
  2008年   2310篇
  2007年   2467篇
  2006年   2377篇
  2005年   2379篇
  2004年   2320篇
  2003年   2344篇
  2002年   2286篇
  2001年   1719篇
  2000年   1856篇
  1999年   1606篇
  1998年   626篇
  1997年   487篇
  1996年   444篇
  1995年   375篇
  1994年   351篇
  1993年   302篇
  1992年   1161篇
  1991年   958篇
  1990年   925篇
  1989年   970篇
  1988年   855篇
  1987年   858篇
  1986年   801篇
  1985年   789篇
  1984年   549篇
  1983年   447篇
  1982年   233篇
  1979年   492篇
  1978年   285篇
  1977年   261篇
  1974年   229篇
  1972年   209篇
  1971年   235篇
  1969年   238篇
  1968年   221篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Since the prevalence and clinical characteristics of young-onset hypertension are still to be elucidated, we performed targeted-screening at an annual university health check-up for two consecutive years. Out of 16,464 subjects in 2003 and 17,032 in 2004 that were aged less than 30 years, 22 and 26 students (all males) exhibited high blood pressure (BP), respectively, on three occasions during casual BP measurements at the Tohoku University Health Center (systolic and diastolic BP of 140 and/or 90 mmHg or greater, respectively). These students were asked to measure their BP at home, and 9 subjects in total were diagnosed as having essential hypertension (EH). The remaining students were diagnosed as having white coat hypertension (WCH). In 8 out of 9 EH students, their father and/or mother had also been treated with antihypertensive medication. Adjustment by attendance ratio for each BP measurement suggested that the incidence of EH was around 0.1% and that of hypertension (EH and WCH) was around 0.5% in university students aged less than 25 years, since most of the subjects and hypertensive students were between 18 and 24 years old. Body mass index of the EH, which was more than 25 kg/m2 (overweight), was significantly higher than that with WCH. In conclusion, the combination of repeated casual BP measurements and home BP effectively identified young-onset EH. The clinical parameters indicated that male gender, genetic background, and excessive weight were risk factors for young-onset hypertension.  相似文献   
72.
The p53 gene has been implicated as a tumor suppressor gene involved in the pathogenesis of lung cancer. Our previous study revealed that the p53 gene is frequently mutated with a distinct nucleotide substitution pattern in small cell lung cancer specimens in Japanese patients. In this study, we examined 30 primary, resected non-small cell lung cancer samples in Japanese patients using complementary DNA-polymerase chain reaction and sequencing. Mutations changing the p53 coding sequence were found in 14 of 30 tumor samples (47%), while G:C to T:A transversions which are uncommon in other cancers such as colon cancer were the most frequently observed mutations, in agreement with an earlier report on non-small cell lung cancer in American patients. Furthermore, the present study shows for the first time that in univariate and multivariate analyses, the presence of p53 mutations is closely associated with lifetime cigarette consumption.  相似文献   
73.
Thymidylate synthetase (TS) and thymidine kinase (TK) are know to catalyze the methylation of dUMP for the de novo synthesis of dTMP and the phosphorylation of thymidine for the salvage synthesis of dTMP in the pyrimidine pathway, respectively, and both enzyme activities are high in rapidly proliferating tissues. In the present study, these enzyme activities and the immunohistochemistry using monoclonal anti-bromodeoxyuridine (BrdU) were investigated during the period of proliferation of bone marrow cells after the hypoplastic period induced by cyclophosphamide (Cy) treatment in rats. Right after Cy treatment, nucleated cell count (NCC) of bone marrow cells, BrdU labelling ratio and TK activity were abruptly decreased. On the other hand, TS activity peaked at day 5 followed by an increase of TK activity, NCC and BrdU labelling ratio from day 7 after Cy treatment. These results indicate that, in the proliferation of bone marrow cells, the DNA de novo synthesis rises at first, and secondly, the DNA salvage synthesis predominantly increases with the increase of bone marrow cells labelled with BrdU, i.e., increase of the cells in the S phase.  相似文献   
74.
Squamous cell carcinoma of the thyroid--a report of three cases   总被引:1,自引:0,他引:1  
Three cases of squamous cell carcinoma of the thyroid are reported herein. In all cases, the carcinoma occurred in old age and was characterized by a rapidly growing tumor, usually associated with dyspnea and dysphagia. The prognosis of all 3 cases was poor, with a mean survival of only 6.3 months. Although squamous metaplasia is an accepted etiology of this disease, clinical investigation of the cases presented here does not favor it in consideration of the clinical features of papillary carcinoma of the thyroid with squamous metaplasia. The histological findings of our cases revealed areas of cystic formation, suggesting that some of these carcinomas may be derived from remnants of embryonic origin.  相似文献   
75.
A case of inflammatory pseudosarcoma of the urinary bladder in a 35 year-old Japanese male is presented. This benign lesion can easily be mistaken for spindle cell sarcoma since it consists of rhabdomyoblast like elongated strap cells showing infiltrative growth, and whether it is benign or malignant is difficult to determine by microscopic examination. In this case, spindle cell proliferation extended among bundles of the superficial muscle layer. However, no abnormal mitoses, severe nuclear atypia or cellular pleomorphism could be seen, thus indicating inflammatory pseudosarcoma. Although the lesion was not completely resected, no recurrent disease has been clinically observed for two years following transurethral resection. Urologists and surgical pathologists must be able to detect this lesion in order to avoid unnecessary surgical procedures. Acta Pathol Jpn 42: 760 765,1992.  相似文献   
76.
A case-control study to evaluate the efficacy of lung cancer screening conducted by us showed that lung cancer screening may reduce the mortality of the disease up to 28%. Assuming this efficacy is unbiased, and that the screening rate is 51.6%, which was observed in the control group in the above study, the number of lung cancer deaths prevented by screening in the study period was calculated to be 47 for males and females combined. In the same study population, screen-detected lung cancer patients (N = 207) in the same study period were followed and the 7-year survival rate (46.9%) was compared to the 5-year survival rate (11.3%) obtained by the Osaka Cancer Registry, in which screen-detected lung cancer patients were only 1.8%. The number of lung cancer deaths prevented by screening, estimated by the difference in the above two survival rates, was 74 (95% confidence interval; 55–93). The number of lung cancer deaths prevented by screening estimated from the case-control study was significantly lower than that estimated from the survival analysis. This indicates that the efficacy of lung cancer screening estimated by the case-control study was within the range that could be explained by the actual long-term survivors among the screen-detected patients in the study population.  相似文献   
77.
MRI of ossification of ligamentum flavum.   总被引:11,自引:0,他引:11  
Magnetic resonance imaging of 28 patients with radiological and/or histopathologically proved ossification of the ligamentum flavum (OLF) was reviewed. The locations of OLF were cervical (n = 4), thoracic (n = 22), and lumbar (n = 2). On T1- and T2-weighted images, OLF demonstrated low signal intensity. Areas of high or intermediate signal intensity within the OLF on T1-weighted images were observed in three cases and were interpreted to be due to fat infiltration. In six cases, high intensity areas in the spinal cord caused by compressing OLF were demonstrated on T2-weighted images. Gadolinium-diethylenetriamine pentaacetic acid, which was used in four cases, showed cord enhancement at the level of compression by OLF in three cases.  相似文献   
78.
Y Matsuki  K Suzuki  M Hara  A Kitani  T Hirose  M Harigai  M Kawakami  N Tanaka  M Kawagoe  H Nakamura 《Ryūmachi》1992,32(2):154-9; discussion 159-62
Arterial thrombosis is one of the major symptoms of antiphospholipid syndrome (APS). However, thrombosis in a primary branch of the aorta has rarely been reported in APS. We report here a case of APS complicated by thromboses in both the left subclavian artery and the left external iliac vein. A 32-year-old woman was admitted in May, 1990 complaining of no pulse in the left superficial arteries (e.g., left radial artery) for the past 5 years and acute swelling of the left lower extremity. A left ascending phlebography showed an occlusion of the external iliac vein and arteriography revealed obstruction in the left subclavian artery. Collateral circulations were developed at the site of each thrombus. Clotting and immunological studies revealed a prolonged APTT, a high titer of anticardiolipin antibody and lupus anticoagulant positive. We ruled out various diseases and clinical risk factors predisposing to both arterial and venous thromboses. Accordingly, we concluded that both thromboses were based on APS. Following treatment with anticoagulants, aspirin and corticosteroid, the swelling of her left thigh was diminished and the antibody titer was decreased within 3 months.  相似文献   
79.
We describe our technique for performing direct thoracoscopic closure of a congenital partial pericardial defect, which was successfully employed in a 15-year-old boy. This is the first such report of a procedure that is noninvasive and may therefore become the treatment of choice for patients with a small congenital pericardial defect.  相似文献   
80.
Summary Effects of STA-MCA anastomosis on two patients with neovascular glaucoma due to occlusion of the internal carotid artery are presented. Both patients improved in visual acuity and central retinal artery pressure as well as in signs of transient ischaemic attack. Postoperative angiography showed a marked decrease in collateral flow through the ophthalmic artery, which is reversed from the normal direction, with the development of blood flow through the anastomosis. Discussion is offered indicating that the lack of collateral flow through both the anterior and posterior communicating arteries is important in addition to occlusion of the internal carotid artery in order to produce full-blown ischaemic oculopathy such as venous stasis retinopathy, neovascular glaucoma or rubeosis iridis. It is stressed that EC-IC bypass surgery should be performed soon after the appearance of ischaemia and before the development of neovascular glaucoma or rubeosis iridis in order to obtain normal vision. In ischaemic oculopathy the results of EC-IC bypass can be evaluated objectively and quantitatively by many noninvasive neuro-ophthalmological tests which are important in discussing the efficacy of the bypass surgery.  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