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   21713篇
  免费   954篇
  国内免费   116篇
耳鼻咽喉   103篇
儿科学   286篇
妇产科学   172篇
基础医学   2675篇
口腔科学   547篇
临床医学   1620篇
内科学   5584篇
皮肤病学   297篇
神经病学   1481篇
特种医学   844篇
外科学   3895篇
综合类   94篇
一般理论   2篇
预防医学   560篇
眼科学   382篇
药学   1396篇
中国医学   30篇
肿瘤学   2815篇
  2023年   123篇
  2022年   236篇
  2021年   392篇
  2020年   217篇
  2019年   311篇
  2018年   349篇
  2017年   306篇
  2016年   373篇
  2015年   372篇
  2014年   511篇
  2013年   673篇
  2012年   1034篇
  2011年   1094篇
  2010年   631篇
  2009年   534篇
  2008年   1013篇
  2007年   1054篇
  2006年   1052篇
  2005年   1075篇
  2004年   1049篇
  2003年   1011篇
  2002年   1068篇
  2001年   685篇
  2000年   685篇
  1999年   643篇
  1998年   322篇
  1997年   246篇
  1996年   233篇
  1995年   193篇
  1994年   171篇
  1993年   189篇
  1992年   557篇
  1991年   516篇
  1990年   487篇
  1989年   469篇
  1988年   388篇
  1987年   343篇
  1986年   313篇
  1985年   266篇
  1984年   180篇
  1983年   175篇
  1982年   73篇
  1979年   140篇
  1978年   98篇
  1977年   81篇
  1974年   90篇
  1973年   74篇
  1972年   79篇
  1971年   73篇
  1969年   65篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
A P300 (P3)-evoked response is generated in a variety of mammalian species upon detection of significant environmental events. The P3 component has been proposed to index a neural system involved in attention and memory capacity. We investigated the contribution of anterior and posterior association cortex to somatosensory P3 generation. Somatosensory event-related potentials (ERPs) were recorded in controls (n = 10) and patients with unilateral lesions in temporal-parietal junction (n = 8), lateral parietal cortex (n = 8), or dorsolateral frontal cortex (n = 10). Subjects pressed a button to mechanical taps of the fifth finger (targets; p = 0.12), randomly interposed in sequences of taps to the second (standards; p = 0.76) and the third or fourth finger (tactile novels; p = 0.06). Occasional shock stimuli were delivered to the wrist (shock novels; p = 0.06). The scalp-recorded P3 was differentially affected by anterior and posterior association cortex lesions. Subjects with temporal-parietal lesions showed markedly reduced P3s to all types of stimuli at all scalp locations. The reductions were largest at the parietal electrode site over the lesioned hemisphere. Parietal patients had normal P3s for all stimulus types except for contralateral shock novels, which generated reduced P3s. Frontal lesions had reductions of the novelty P3 over frontal sites with minimal changes in the target P3. The data support the existence of multiple intracranial P3 sources. The data further indicate that association cortex in the temporal-parietal junction is critical for generating the scalp-recorded target and novelty P3s, whereas dorsolateral frontal cortex contributes preferentially to novelty P3 generation. The N2 component was reduced by parietal and frontal lesions in patients who had intact target P3s, suggesting that different neural systems underlie N2 and P3 generation.  相似文献   
52.
A 36-year-old man was admitted to a hospital with complaints of fever, polyarthralgia and dyspnea. Erythema was observed on his face, extensor surface of the fingers and extremities, and a chest X-ray revealed massive bilateral pleural effusion. He had no sign of myopathy at this point. Pleural fluid was proved to be exudative and contained extremely high levels of hyaluronic acid. He was also complicated with interstitial pneumonitis and was given a pulse therapy with methyl prednisolone followed by daily administration of 55 mg prednisolone (PSL). Twenty days after the commencement of the therapy, pleural effusion decreased but muscle weakness gradually appeared, accompanied by elevation of myogenic enzymes. Myogenic changes on electromyogram, and irregularity of the muscle fibers with slight inflammatory cell infiltrates in a biopsy specimen were demonstrated. He was transferred to our hospital, and a diagnosis of dermatomyositis was made. Later, pleural effusion waxed and waned depending on the dosage of PSL, but no other causative disorder was demonstrated by extensive examinations. This case indicates that the pleuritis could be one of the vasculitic manifestations of dermatomyositis.  相似文献   
53.
54.
A 49-year-old woman was referred to our hospital with complaints of epigastric colicky pain and high fever. Abdominal computed tomography and ultrasonography showed a solid tumor in the lower abdomen. Laparotomy revealed a neoplastic mass arising in Meckel's diverticulum; therefore, a segment of the ileum, including the tumor-possessing diverticulum, was resected with a lymph node dissection. A histologic examination confirmed the lesion to be leiomyosarcoma. In the English literature, 59 cases of leiomyosarcoma in Meckel's diverticulum were reported from 1941 to 1994. The majority of patients were in their 4th decade of life, with both sexes equally affected. The most frequent symptoms associated with this disease were abdominal pain with nausea, vomiting, and melena. The majority were larger than egg-size. Although Meckel's diverticulum is difficult to diagnose preoperatively, mesenteric arteriography may at times prove useful. The standard management of this particular tumor is wide segmental resection, including the tumor and diverticulum with lymph node dissection.  相似文献   
55.
The technique of extended lid-splitting surgery is described. This procedure was used to repair marginal defects of the lower and upper lid, and provided postoperative results that were excellent both functionally and cosmetically, principally because the technique allowed the anatomical structures to be maintained.  相似文献   
56.
Nuclear size and shape on histological specimens were used to quantify nuclear abnormality in gastric tubular tumors. A valid technique for this morphometrical analysis by image processing was developed. Furthermore, the present study examined the nuclear size and shape to determine if they were reliable criteria to be used for differential diagnosis. Nuclear area, maximum diameter and maximum width on the histological specimens were defined as factors to represent nuclear size. Nuclear aspect ratio represented nuclear shape. Histological features revealed varied degrees of condensation of nuclei; this was due to different protocols for preparing the histological specimens. This finding indicated that the size of intermediate lymphocytes on the same specimens should be measured as a control in order to estimate the degree of nuclear condensation. The present study also demonstrated that at least 200 nuclei should be measured on the histological specimens to obtain accurate nuclear size and shape. Histologically, the nuclei in benign tubular adenoma and borderline lesions tended to be spindle-shaped, while those in well-differentiated type tubular adenocarcinoma tended to be round and swollen. The nuclei in borderline lesions were larger than those in benign tubular adenoma and smaller than those in well-differentiated type tubular adenocarcinoma. Our results for the above 4 factors corresponded well with these histological findings. The nuclear size and shape on histological specimens were concluded to be reliable criteria for assessing nuclear abnormality in gastric tubular tumors and useful ones for differential diagnosis.  相似文献   
57.
Summary. A man, 79 years of age, developed a malignant fibrous histiocytoma which arose in relation to a calcifying enchondroma of the distal femur. Radiographs showed a fracture through an intensely calcified bony tumour with no bony destruction. The clinical diagnosis was a dedifferentiated chondrosarcoma. Histology showed an anaplastic sarcoma with calcified tissue showing extensive areas of necrosis and degeneration. No chondrosarcomatous foci were found.
Resumé. Nous rapportons le cas d’un homme de 79 ans, qui a développé un histiocytofibrome malin à partir d’un enchodrome calcifié du fémur distal. L’examen radiologique a montré une fracture au sein d’une tumeur très calcifiée sans association de destruction osseuse. Cette lésion apparaissait cliniquement être un chondrosarcome dédifférencié. Mais l’étude histologique a montré un sarcome anaplasique avec un tissu cartilagineux calcifié présentant des plages étendues de nécrose et de dégénérescence. Il n’y avait pas de foyer chondrosarcomateux visible.


Accepted: 9 November 1996  相似文献   
58.
Three cases of tubular adenoma of the gallbladder with squamoid spindle cell metaplasia are reported. Two of the three patients, who were middle-aged Japanese, had a solitary polyp in the gallbladder, and the other had three polyps. All the lesions were detected incidentally by ultrasonography. The polyps were pedunculated with a fine or frail stalk, and ranged from 0.5 to 3.9 cm in diameter. Histologically, they were tubular adenomas accompanied by scattered foci composed of a compact collection of short-spindle or oval cells with mild atypia. These cells did not retain intercellular bridges, and lacked intracellular keratinization. Immunohistochemically, the spindle cells stained positively for high-molecular-weight cytokeratin (EAB 903, a marker of squamous cell differentiation), whereas adenoma cells lining the tubules were negative for this antigen. Therefore, the spindle cell component is considered to represent squamoid metaplasia of adenoma cells.  相似文献   
59.
In a previous study, we used a murine monoclonal antibody, A7, against human colon carcinoma as a drug-carrier to treat colorectal cancer.1 In the present study, we found that MAb A7 also reacted immunohistochemically with 73% of human pancreatic carcinoma cell lines, with the A7 antigen mainly being detected on the cell surface. However, the A7 antigen was found in only 9% of the spent media of these human pancreatic carcinoma cell lines by ELISA. On the other hand, the positive incidence of CA19-9, POA, ferritin, CEA, DU-PAN-2 and SLX in those spent media was 100%, 64%, 64%, 55%, 55% and 36%, respectively. These results suggest that the A7 antigen may only rarely be shed into the sera of pancreatic cancer patients, in which case MAb A7 could be a suitable drug-carrier in targeting chemotherapy for pancreatic cancer patients.  相似文献   
60.
A 10-year-old girl having bilateral subclavian steal associated with severe coarctation of the thoracic aorta and an aberrant right subclavian artery was found, on admission, to have no difference between upper and lower extremity blood pressure, but echocardiography revealed severe thoracic aorta coarctation and systolic blood pressure in the carotid arteries exceeding 200 mmHg estimated by Doppler ultrasonography. Magnetic resonance imaging and angiography demonstrated bilateral subclavian steal without esophageal compression. We reconstructed the aortic arch using the left subclavian artery and a reversed Blalock-Park procedure, then repaired the coarctation with a 14 mm woven double velor vascular graft. The girl was symptom-free following uncomplicated recovery from surgery. Doppler ultrasonography 2 weeks after surgery showed the pressure gradient across the aortic arch had decreased from 180 mmHg to 60 mmHg. This residual gradient at the anastomosis between the ascending aorta and left subclavian artery may improve as native vessels grow.  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