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   12025篇
  免费   581篇
  国内免费   55篇
耳鼻咽喉   144篇
儿科学   146篇
妇产科学   111篇
基础医学   1547篇
口腔科学   269篇
临床医学   760篇
内科学   2788篇
皮肤病学   257篇
神经病学   1017篇
特种医学   445篇
外科学   2313篇
综合类   50篇
一般理论   1篇
预防医学   464篇
眼科学   196篇
药学   1034篇
中国医学   40篇
肿瘤学   1079篇
  2023年   50篇
  2022年   140篇
  2021年   227篇
  2020年   128篇
  2019年   175篇
  2018年   202篇
  2017年   179篇
  2016年   235篇
  2015年   208篇
  2014年   257篇
  2013年   374篇
  2012年   496篇
  2011年   572篇
  2010年   300篇
  2009年   290篇
  2008年   443篇
  2007年   539篇
  2006年   490篇
  2005年   503篇
  2004年   465篇
  2003年   449篇
  2002年   492篇
  2001年   428篇
  2000年   449篇
  1999年   407篇
  1998年   145篇
  1997年   124篇
  1996年   105篇
  1995年   83篇
  1994年   84篇
  1993年   85篇
  1992年   350篇
  1991年   310篇
  1990年   314篇
  1989年   291篇
  1988年   283篇
  1987年   282篇
  1986年   276篇
  1985年   214篇
  1984年   144篇
  1983年   141篇
  1982年   50篇
  1981年   56篇
  1979年   117篇
  1978年   57篇
  1977年   58篇
  1974年   52篇
  1973年   60篇
  1972年   65篇
  1970年   49篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
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   
42.
This study examined the incidence of downhill esophageal varices due to SVC syndrome. The presence of downhill esophageal varices was examined by esophagoscopy or autopsy. Downhill esophageal varices were detected in two of nine (22%) patients with SVC syndrome. One case was a 66-year-old male case who and underwent upper lobectomy for lung cancer in September 1985. He developed SVC syndrome due to recurrence in 1986 and died in 1987. Downhill esophageal varices wer in the upper esophagus by esophagoscopy and confirmed by autopsy. The another case was a 61-year-old female who developed carcinoma of the tongue in 1986 and lymph node metastasis to the mediastinum in 1987. Autopsy revealed downhill esophageal varices in the upper and middle esophagus. Eleven cases of downhill esophageal varices due to SVC syndrome reported in Japan were reviewed and discussed.  相似文献   
43.
The spin-lattice relaxation time (T1) of water protons and the cross-relaxation time (TIS) between irradiated protein protons and observed water protons were measured in order to study water-macromolecular interactions in ischemic rat brain tissues. Tissues were obtained by bilateral common carotid artery occlusion from stroke-prone spontaneously hypertensive rats. Water, Na, and K contents were measured in ischemic brain tissue at the same time. Water and Na content increased while the TIS value and K content decreased following ischemic insults. The T1 value did not change until 180 min after ischemia had been induced. Changes in the TIS value occurred earlier than changes observed for the T1 value, water, and electrolyte contents. Results indicate that the value of TIS may be useful for detecting cerebral ischemia and that the physical structure of water-macromolecular interaction may be altered soon after ischemic onset in brain tissue.  相似文献   
44.
While nonspecific airway hyperresponsiveness (AHR) is a central feature of allergic bronchial asthma, the mechanism underlying the development of AHR is not clearly understood. We have previously demonstrated in vitro hyperresponsiveness of bronchial smooth muscle to acetylcholine (ACh) in rats that were actively sensitized and repeatedly challenged with aerosolized antigen. It has also been demonstrated that the ACh-induced, RhoA-mediated Ca(2+) sensitization is markedly augmented concomitantly with an increased expression and activation of RhoA protein in the bronchial smooth muscle of the antigen-treated rats. In the present study, we have investigated whether TNF-alpha, a proinflammatory cytokine which is involved in bronchial asthma, causes upregulation of RhoA mRNA and protein in the rat bronchus. Treatment of rat bronchial smooth muscle preparations with TNF-alpha (300 ng/ml for 24 hr) significantly shifted the concentration-response curve to ACh upwards, but did not alter the response to high K(+), when compared to that of control tissues. Levels of RhoA mRNA and protein in the TNF-alpha-treated bronchus were significantly greater than those in the control group. In conclusion, it is suggested that the augmentation of the ACh-induced contractile response evoked by TNF-alpha might be mediated by an upregulation of RhoA in rat bronchial smooth muscle.  相似文献   
45.
A 30-year-old female at 27 weeks' gestation, was hospitalized on September 24 1990 because of the premature rupture of the amniotic sac. She underwent Caesarean section on the same day with 700 ml blood loss, but no blood transfusion was required. For several days after the operation, her hemoglobin level remained 7.8 g/dl and did not increase significantly in spite of parenteral iron therapy. On the 9th postoperative day, chills and pyrexia developed with leukopenia. Bone-marrow aspiration revealed severe erythroblastopenia with giant proerythroblasts, suggesting recent HPV infection, which was confirmed by the presence of anti-HPV IgM and HPV antigen by ELISA. The hemoglobin level gradually decreased to 6.0 g/dl by the 21st day, then began to increase rapidly. The serum of acute-phase containing HPV antigens inhibited BFU-E and CFU-E but not CFU-GM. The serum of convalescent-phase inhibited neither erythroid colony growth nor myeloid colony growth. These results indicate that the inhibitory effect of HPV in colony assay is highly specific for erythropoiesis and that HPV play a role in transient cessation of erythropoiesis. The reason, however, for leukopenia in HPV infection remained unclear. This case shows that HPV infection may induce severe hematological disorders even in normal person under erythropoietic stress.  相似文献   
46.
A 54-year-old female presented with subarachnoid hemorrhage due to rupture of a small middle cerebral artery aneurysm, found to be thrombosed at surgery and not visualized on the preoperative angiograms. One major branch of the middle cerebral artery was found to be occluded near the trifurcation. The lumen of the branch proximal to the occlusion had appeared as the aneurysmal opacification on the preoperative angiograms.  相似文献   
47.
A sensitive enzyme-linked immunosorbent assay (ELISA) was used in a retrospective study of placental alkaline phosphatase (PLAP) levels in serum, cerebrospinal fluid (CSF), and intratumoral cyst fluid in primary intracranial germinoma. The ELISA showed no cross-reactivity with intestinal alkaline phosphatase except in very high concentrations, after samples had been heat-treated. Three patients with germinoma were studied for serum PLAP levels and in all the levels were elevated (3.78, 0.52, and 2.11 IU/liter). Two of the germinoma patients were studied for PLAP levels in the CSF, and both had elevated levels (0.83 and 9.83 IU/liter). The intratumoral cyst fluid in one case of germinoma was tested for PLAP and the level was found to be very high (603 IU/liter). These PLAP levels decreased concomitantly with the reduction in tumor size during irradiation. Serum PLAP levels were measured in 40 control adult male individuals and in the CSF of 20 nonpregnant patients with subarachnoid hemorrhage. The upper normal limits were 0.20 and 0.11 IU/liter in the serum and the CSF, respectively. All PLAP levels measured in the serum of patients with various brain tumors were 0.18 IU/liter or less. This study strongly suggests that PLAP is a clinically useful tumor marker for primary intracranial germinoma.  相似文献   
48.
Sialolipoma is a new variant of salivary gland lipoma, which was first proposed by Nagao et al. (Histopathology 2001; 38: 30) in 2001. We report this rare case of sialolipoma in the hard palate. A 60-year-old Japanese woman was referred to our department complaining of a painless swelling on the right side of the hard palate. Intra-oral examination revealed a soft, elastic, dome-shaped mass with 1 cm in diameter located in the posterior part of the hard palate. Magnetic resonance imaging examination revealed high intensity on T(1)-weighted image and isointensity on T(2)-weighted image. Incisional biopsy revealed that the tumor was encapsulated by fibrous tissue, consisted of adipose tissue, and also contained normal salivary gland tissue peripherally. First diagnosed as an ordinary lipoma of the hard palate, the tumor was excised. According to the recent criteria of histologic findings of sialolipoma, we rediagnosed the tumor as sialolipoma of the hard palate.  相似文献   
49.
To investigate the relationship between the effects of bone turnover and bone marrow cell development in bone cells, we developed a mouse voluntary climbing exercise model. Climbing exercise increased bone volume and transient osteogenic potential of bone marrow. This model would be suitable for investigating the mechanistic roles of mechanical loading. INTRODUCTION: The relationship between bone mass gain and local bone formation and resorption in mechanically loaded bone is not well understood. MATERIALS AND METHODS: Sixty-five C57BL/6J mice, 8 weeks of age, were assigned to five groups: a baseline control and two groups each of ground control and climbing exercise mice for 2 and 4 weeks. Mice were housed in a 100-cm tower and had to climb toward a bottle placed at the top to drink water. RESULTS: Compared with the ground control, bone mineral density of the left femur increased in the climbing mice at 4 weeks. At 2 and 4 weeks, bone formation rate (BFR/BS) of periosteal surface, the cross-sectional area, and moment of inertia were increased in the climbing mice, whereas BFR/BS and eroded surface (ES/BS) of endosteal surface did not differ. The trabecular bone volume (BV/TV) of the proximal tibia increased in climbing mice, and osteoclast surface (Oc.S/BS) and osteoclast number decreased at 2 weeks. At 4 weeks, there were increases in BV/TV and parameters of bone formation, including mineralized surface, mineral apposition rate, and bone formation rate. In marrow cell cultures from the tibia, the number of alkaline phosphatase+ colony forming units-fibroblastic and the area of mineralized nodule formation in climbing mice were increased, and the number of osteoclast-like TRACP+ multinucleated cells was lower at 2 weeks. At 4 weeks, these parameters recovered to the levels of the ground controls. CONCLUSION: Our results indicate that climbing increased trabecular bone volume and reduced bone resorption, with a subsequent increase in bone formation. Intermittent climbing downregulates marrow osteoclastogenic cells and upregulates osteogenic cells initially, but further exercise seemed to desensitize them. Cortical envelopes were enlarged earlier, but the response seems to differ from trabecular bone.  相似文献   
50.
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