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   39863篇
  免费   1781篇
  国内免费   304篇
耳鼻咽喉   315篇
儿科学   724篇
妇产科学   637篇
基础医学   5191篇
口腔科学   1091篇
临床医学   2360篇
内科学   9920篇
皮肤病学   880篇
神经病学   2692篇
特种医学   1375篇
外科学   7104篇
综合类   159篇
一般理论   1篇
预防医学   1108篇
眼科学   675篇
药学   2332篇
中国医学   135篇
肿瘤学   5249篇
  2023年   222篇
  2022年   582篇
  2021年   930篇
  2020年   488篇
  2019年   691篇
  2018年   896篇
  2017年   702篇
  2016年   829篇
  2015年   853篇
  2014年   1148篇
  2013年   1448篇
  2012年   2374篇
  2011年   2765篇
  2010年   1566篇
  2009年   1281篇
  2008年   2342篇
  2007年   2610篇
  2006年   2447篇
  2005年   2635篇
  2004年   2534篇
  2003年   2549篇
  2002年   2538篇
  2001年   532篇
  2000年   482篇
  1999年   576篇
  1998年   625篇
  1997年   492篇
  1996年   454篇
  1995年   395篇
  1994年   358篇
  1993年   323篇
  1992年   335篇
  1991年   292篇
  1990年   299篇
  1989年   285篇
  1988年   260篇
  1987年   238篇
  1986年   183篇
  1985年   163篇
  1984年   167篇
  1983年   143篇
  1982年   97篇
  1981年   104篇
  1980年   94篇
  1979年   87篇
  1978年   58篇
  1976年   42篇
  1975年   44篇
  1974年   42篇
  1973年   43篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
We describe a 54-year-old woman with primary pulmonary adenocarcinoma showing a characteristic papillary architecture and prominent cilia formation. Immunohistochemically, the tumor cells were positive for carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA) and Leu Ml, and negative for lactoferrin and surfactant apoprotein. An ultrastructural study also indicated differentiation toward bronchial surface epithelial cells. To our knowledge, this type of neoplasm has not been reported as peripheral-type adenocarcinoma of the lung. Acta Pathol Jpn 42: 745–750, 1992.  相似文献   
32.
We describe a case of type B aortic dissection with large ascending aortic aneurysm occurring 12.8 years after aortic root replacement (Cabrol procedure) in a non-Marfan patient with cystic medial necrosis of the aorta. We have successfully performed an extended total aortic arch replacement using a four-branched graft through the “L-indsion” approach (a combination of a left anterior thoracotomy and upper half median sternotomy). Of note, a histological specimen from the aneurysmal ascending aortic wall revealed “healed aortic dissection” with fibrous tissue replacing the media and intima in addition to multiple foci of cystic medial necrosis.  相似文献   
33.
The roles of glutathione (GSH), cysteine, vitamin C., liposome-encapsulated superoxide dismutase (L-SOD) and vitamin E in preventing oxidative DNA damage and cytotoxicity in the rat kidney after administration of potassium bromate (KBrO3) to male F344 rats were investigated by measuring 8-hydroxydeoxyguanosine (8-OH-dG), an oxidative DNA product, lipid peroxidation (LPO) levels and relative kidney weight (RKW). Combined pre- and posttreatment of animals with 2 × 800 mg/kg GSH i.p. inhibited the increase of 8-OH-dG, LPO levels and RKW caused by 80 mg/kg KBrO3 i.p. administration. In contrast, pretreatment with 0.3 ml/kg diethylmaleate (DEM) i.p., a depletor of tissue GSH, was associated with elevation of 8-OH-dG, LPO levels and RKW after a 20 mg/kg KBrO3 i.p. treatment, which itself caused no change. Administration of KBrO3 itself reduced renal non-protein thiol levels, but this was inhibited by the two doses of exogenous GSH. Combined treatment with DEM and KBrO3 lowered the non-protein thiol level in the kidney more than did DEM treatment alone. Protective effects against the oxidative damage caused by KBrO3 were also observed for pre- and posttreatment with 400 mg/kg cysteine i.p., another sulfhydryl compound, and daily i.g. application of 200 mg/kg vitamin C for 5 days. However, no influence was evident after pre- and posttreatment with 18,000 U/kg L-SOD i.p. or daily i.g. 100 mg/kg of vitamin E for 5 days. The results suggest that intracellular GSH plays an essential protective role against renal oxidative DNA damage and nephrotoxicity caused by KBrO3.  相似文献   
34.
An early gastric carcinoma, measuring 1.7 X 0.6 cm, had already metastasized to the extra-perigastric lymph node in a 71 year old symptom-free man. Radiographic and endoscopic studies showed a small depressed lesion on the lesser curvature of the antrum and histology of the biopsied specimen revealed a well differentiated adenocarcinoma. Under the diagnosis of IIc type intramucosal carcinoma, partial gastrectomy and wide lymph node dissection was performed. Pathologic study of the resected specimen showed that the cancer cells had invaded the submucosa at an area via a lymphatic vessel and that only one lymph node along the common hepatic artery was involved.  相似文献   
35.
Four patients with untreated renal tubular acidosis had a urinary excretion of low-molecular-weight (LMW) proteins which was restored to normal by alkali therapy. Hypokalaemic proximal tubular damage in untreated patients with distal renal tubular acidosis is believed to be the cause of LMW proteinuria. An examination of urinary excretion of LMW proteins is useful for determining hypokalaemic proximal tubular dysfunction, as well as the efficiency of alkali therapy.  相似文献   
36.
Lewis Y (Ley) antigen, a difucosylated tetrasaccharide found on type 2 blood group oligosaccharides of glycolipids and glycoproteins, is thought to be a phenotypic marker predictive of cell differentiation. The distribution of this antigen in human anagen hair follicles was examined by immunohistochemical staining using a monoclonal antibody (AH-6) to Ley. In the bulbar and suprabulbar portion of anagen hair follicles, Ley antigen was detected in the three layers of the inner root sheath. Subsequently, the positive staining became translocated to the innermost layer of the outer root sheath in the middle part of the hair follicles. In the upper portion of the hair follicles, Ley antigen was found in the outer cells of the outer root sheath. These findings suggested that the expression of Ley antigen in the anagen hair follicles was correlated with the processes of keratinization or terminal differentiation.  相似文献   
37.
38.
We investigated the temporal and spatial expression of transforming growth factor-β in the healing patellar ligament of the rat by immunohistochemistry. The mid-portion of the medial half of the patellar ligament in 14-week-old male Wistar rats was cut transversely with a scalpel. On day 1 after ligament injury, diffuse staining for transforming growth factor-β was observed in the extracellular matrix filling the wound, and the staining in the adjacent ligament tissue was as weak as it was in the normal ligament. On day 3, the intensity of the diffuse extracellular staining decreased, and the staining was observed in correspondence with the cellular distribution in the wound site and in the adjacent uninjured ligament tissue. On day 7, the intense staining was widely distributed over the whole length of the ligament tissue. On day 28, the staining for transforming growth factor-β was still observed at the wound site and in the adjacent uninjured ligament tissue, where the staining was reduced in intensity but still stronger than it was in the normal ligament. On day 56, the expression of transforming growth factor-β was still detectable at the wound site: however, in the adjacent uninjured ligament tissue, it had almost subsided to the normal level. The results of the present study suggest that ligament healing may be accompanied by extensive changes in the expression of transforming growth factor-β over the whole length of ligament tissue.  相似文献   
39.
A case is reported of Wilms' tumor associated with multiple pulmonary metastases histologically showing maturation of the tumor cells at 9 years after the resection of the primary tumor and intensive therapy. A huge tumor of a 22-month-old patient's right kidney was resected. The tumor was diagnosed as Wilms' tumor of mesenchymal type (stage 1), which consisted of predominantly immature mesenchymal tissue including rhabdomyoblasts, smooth muscle and fibrous tissue, and few blastemal and epithelial components. Intensive preoperative and postoperative chemotherapy with actinomycin D and vincristine and postoperative irradiation therapy totaling 16 Gy were carried out. The patient was regularly followed up uneventfully until 9 years after the surgery. On routine chest x ray at the age of 10 years 11 months, multiple pulmonary nodules were found. The excised nodules from the bilateral lungs disclosed similar histology, exclusively composed of dense collagen bundles and fibrocytes intermingled with mature striated muscle bundles. No immature tumor components were detected. The possible effect of intensive therapy in this maturation was stressed, although spontaneous benign differentiation of tumor cells cannot be excluded.  相似文献   
40.
Abstract: Studies on the circadian rhythm of urine excretion in healthy men have demonstrated that the maximal urine flow occurs in the early afternoon and the minimal around midnight. In this study, an abnormality in the variation of urine volume was found in parkinsonian patients. Urine samples were collected during daytime (9:00–21:00) and nighttime (21:00–9:00). Fifteen healthy control subjects were examined and found to excrete 60% during the daytime and 40% during the nighttime of the total urine volume. Sixteen parkinsonian patients excreted 43% during the daytime and 57% during the nighttime. In contrast to the control subjects, the parkinsonian patients excreted a smaller volume of their urine during the daytime than during the nighttime. This finding might be related to the degeneration of dopaminergic and/or nondopaminergic neurons in the brain which control urinary excretion.  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