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   12908篇
  免费   646篇
  国内免费   69篇
耳鼻咽喉   197篇
儿科学   200篇
妇产科学   166篇
基础医学   1474篇
口腔科学   534篇
临床医学   984篇
内科学   3402篇
皮肤病学   160篇
神经病学   767篇
特种医学   497篇
外科学   2221篇
综合类   50篇
预防医学   402篇
眼科学   236篇
药学   790篇
中国医学   14篇
肿瘤学   1529篇
  2023年   85篇
  2022年   124篇
  2021年   231篇
  2020年   127篇
  2019年   168篇
  2018年   206篇
  2017年   171篇
  2016年   235篇
  2015年   251篇
  2014年   318篇
  2013年   351篇
  2012年   639篇
  2011年   676篇
  2010年   396篇
  2009年   321篇
  2008年   684篇
  2007年   664篇
  2006年   734篇
  2005年   696篇
  2004年   693篇
  2003年   672篇
  2002年   677篇
  2001年   343篇
  2000年   364篇
  1999年   374篇
  1998年   173篇
  1997年   145篇
  1996年   135篇
  1995年   125篇
  1994年   134篇
  1993年   136篇
  1992年   295篇
  1991年   254篇
  1990年   207篇
  1989年   190篇
  1988年   180篇
  1987年   184篇
  1986年   161篇
  1985年   153篇
  1984年   125篇
  1983年   86篇
  1982年   58篇
  1981年   58篇
  1979年   64篇
  1978年   56篇
  1977年   40篇
  1975年   49篇
  1974年   51篇
  1971年   39篇
  1969年   49篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Thirty-eight patients with convexity lesions were studied prospectively with the two-dimensional time-of-flight (2D-TOF) magnetic resonance angiography (MRA) method. Of these 21 cases had additional surface anatomy scanning (SAS) and 7 cases had three-dimensional phase contrast (3D-PC) MRA. The findings were compared during surgery, and the predictability of 2D-TOF evaluated. 2D-TOF was obtained with 2 mm slice thickness after the administration of contrast media for routine magnetic resonance imaging (MRI). Cortical veins were visualized with a good resolution with a scan time of only 5 minutes. The tumor was also visible in the background, due to enhancement, and thus the tumor-vessels relation was shown. Slow-flow vessels were also adequately seen. SAS was done at the same sitting with fast spin echo (FSE) with a scan time of 3 minutes. Once both images were incorporated, information on gyri and their relation to the lesions and vasculature could be obtained from a single image. We found 2D-TOF alone, or at times in combination with SAS, useful for planning of operation for convexity lesions.  相似文献   
42.
Toluene in blood as a marker of choice for low-level exposure to toluene   总被引:1,自引:1,他引:0  
The validity of two new biological exposure markers of toluene in blood (TOL-B) and toluene in urine (TOL-U) was examined in comparison with that of the traditional marker of hippuric acid in urine (HA-U) in 294 male workers exposed to toluene in workroom air (TOL-A), mostly at low levels. The exposure was such that the geometric mean for toluene was 2.3 ppm with a maximum of 132 ppm; the workers were also exposed to other solvents such as hexane, ethyl acetate, styrene, and methanol, but at lower levels. The chance of cutaneous absorption was remote. Higher correlation with TOL-A and better sensitivity in separating the exposed workers from the nonexposed subjects were taken as selection criteria. When workers exposed to TOL-A at lower concentrations (< 50 ppm, < 10 ppm, < 2 ppm, etc.) were selected and correlation with TOL-A was examined, TOL-B showed the largest correlation coefficient which was significant even at TOL-A of < 1 ppm, whereas correlation of HA-U was no longer significant when TOL-A was < 10 ppm. TOL-U was between the two extremes. The sensitivities of TOL-B and TOL-U were comparable; HA-U showed the lowest sensitivity. Thus, it was concluded that TOL-B is the indicator of choice for detecting toluene exposure at low levels.  相似文献   
43.
Late Effects of Childhood Acute Leukemia and Its Treatment   总被引:1,自引:0,他引:1  
Late effects of childhood acute leukemia and its treatment were studied in 766 patients (684 ALL, 73 ANLL, and 9 others) in Japan who had remained in remission for more than 1 year after their first complete remission. Delayed adverse sequelae involve a wide variety of organs and their functions. Short stature was present in 2.61%, obesity in 3.79%, abnormalities of growth hormone secretion in 1.5%, delayed secondary sex characteristics in 1.5% of males and 0.6% of females, motor disturbances in 1.17%, sensory disturbances in 0.91%, intellectual and learning disabilities in 2.48%, abnormal findings in routine neurologic examinations in 1.31%, EEG abnormalities in 4.30%, brain CT abnormalities in 5.09% and cardiac dysfunction in 1.07%. Various other disorders were seen in 20 patients. Many of these delayed adverse sequelae are caused by or related to central nervous system prophylaxis and systemic combination chemotherapy. The results suggest that it is needed to improve therapeutic methods through the stratification of patients by risk factors and detailed analysis of prognostic factors. Moreover it is important to render medical and psychosocial support to long-term survivors of childhood leukemia through interactions between the patient, parents and medical staff.  相似文献   
44.
A case of a ruptured fusiform aneurysm of the posterior cerebral artery is reported. The aneurysm was excised and end-to-end anastomosis was carried out between the two ends of the posterior cerebral artery. There is no previous report of a posterior cerebral artery aneurysm treated with this technique. The pertinent literature is reviewed and the significance of this technique in the treatment of unclippable cerebral aneurysms is discussed.  相似文献   
45.
46.
To examine the effects of ischemic preconditioning on efferent autonomic responses following acute transmural myocardial ischemia/infarction (MI), the time course and extent of efferent sympathetic and vagal denervation were compared between control dogs that received a one-stage sustained coronary occlusion and preconditioned dogs that received four 5-minute coronary occlusions separated by 5 minutes of reperfusion before sustained occlusion. Effective refractory periods (ERP) basal and apical to MI were determined in the baseline state and during neural stimulation before and after preconditioning occlusions and 20, 60, 120, and 180 minutes after sustained occlusion by ligature ligation of diagonal branches of the left anterior descending coronary artery. In 10 control dogs with transmural MI, ERP shortening induced by bilateral ansae subclaviae stimulation (4-msec pulses, 2-4 Hz and 2-4 mA) was unchanged at basal sites but was attenuated at apical sites. Four of 40 apical test sites exhibited efferent sympathetic denervation (less than or equal to 2 msec shortening) 20 minutes after sustained occlusion. Thirteen of 40 apical sites became denervated during a 3-hour period. In 10 preconditioned dogs, ERP shortening at apical sites was unchanged after preconditioning occlusions and during the first 60 minutes of sustained ischemia but was attenuated at 120 minutes. Three of 40 apical test sites became denervated during a 3-hour period. The cumulative percentage of denervated apical test sites was significantly less in the preconditioned group compared with the control group (p = 0.006) despite a comparable degree of subepicardial involvement in the MI (8.2 +/- 1.0% vs. 8.4 +/- 1.4%, the ratio to the left ventricular circumference, mean +/- SEM). In 11 control dogs tested for efferent vagal response after MI, ERP prolongation induced by bilateral vagal stimulation (4-msec pulses, 20 Hz with current strength 0.05 mA greater than that required to produce asystole) was unchanged at basal sites, but was attenuated at apical sites, and five of 44 test sites exhibited denervation (less than or equal to 1 msec prolongation) 20 minutes after sustained coronary occlusion. Fourteen of 40 apical sites became denervated during a 3-hour period. In 10 preconditioned dogs, vagally induced ERP prolongation was unchanged both at basal and apical sites, and none of 36 apical test sites exhibited denervation after preconditioning and during a 3-hour period of sustained coronary occlusion (p less than 0.001 vs. control group) despite a comparable degree of subendocardial involvement in the MI (11.8 +/- 0.8% vs. 11.9 +/- 1.3%).(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
47.
48.
Abstract: This case report describes a patient with a rectal ulcer who had an unusual defecation habit. Complete healing was recognized colonoscopically after the patient was instructed to break this habit. A polyp of the ascending colon was detected by a barium enema in a 37-year-old man complaining of anal bleeding. He was admitted to our division to undergo a polypectomy. At the time of the polypectomy, a round ulcer, measuring 1 cm in diameter, was detected on the right wall of the rectum 3 cm from the anal verge. A diagnosis of mucosal prolapse syndrome of the rectum could not be made because the patient did not exhibit the characteristic habit of excessive “straining” mentioned by patients with this syndrome, and no characteristic finding of fibromuscular obliteration was found on histological examination of biopsied specimens taken endoscopically from the lesion. Repeated history taking, however, revealed that the patient had the unusual habit of inserting his finger into his rectum after defecation. He broke this habit following instruction to do so. As a result, on colonoscopic examination 15 month later, the ulcer was found to have become a scar:  相似文献   
49.
This report describes our experience with a 60 year old male who suffered from a recrudescence of groove pancreatitis. He had been treated by conservative medication therapy by proton pump inhibitor used for therapy of duodenal ulcer, and was in remission. During a follow-up one year later, endoscopy revealed gastric cancer, for which a proximal gastrectomy and vagotomy were performed. The patient continues to remain in remission for the groove pancreatitis. Our experience with the clinical course of this disease, in which treatment for duodenal ulcer was used effectively, offers new insights into the progression and therapy of groove pancreatitis.  相似文献   
50.
Gastric cancer heterogeneity   总被引:1,自引:0,他引:1  
This study was carried out on 222 samples from 37 gastric carcinomas to assess the incidence of multiple stem lines in primary tumors and metastasis as reflected by multiple DNA stem lines and their relationship to epidermal growth factor (EGF) receptor expression, histologic grade, tumor size, and degree of wall infiltration. Fifteen primary tumors (40.5%) were homogeneously diploid/peridiploid whereas 22 (59.5%) were aneuploid. In the lymph node metastasis, seven patients (29.2%) had an homogeneous diploid/peridiploid pattern in all metastatic lymph nodes. On the other hand, 17 (70.8%) had at least one aneuploid peak in the lymph node metastasis. DNA content heterogeneity was seen in 12 (33%) of primary tumors whereas 14 (66.6%) of 21 patients had multiple cell clones in the metastasis. Therefore, 12 patients had a metastatic clone which was not observed in the primary tumor. DNA content heterogeneity was seen even in tumors with submucosal invasion suggesting that this phenomenon is also present at earlier stages. No correlation between the histologic grade and the DNA distribution was observed. Furthermore, histologic heterogeneity was independent of DNA content heterogeneity. The EGF receptor expression was observed in six of the 23 patients in whom this analysis was done. The EGF receptor expression was constant in all samples which were studied and even samples with a different DNA content and histologic grade were stables for the EGF receptor expression.  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