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   6743篇
  免费   402篇
  国内免费   21篇
耳鼻咽喉   62篇
儿科学   223篇
妇产科学   65篇
基础医学   1163篇
口腔科学   281篇
临床医学   555篇
内科学   1017篇
皮肤病学   239篇
神经病学   793篇
特种医学   270篇
外科学   865篇
综合类   37篇
一般理论   2篇
预防医学   262篇
眼科学   291篇
药学   545篇
中国医学   9篇
肿瘤学   487篇
  2023年   18篇
  2022年   38篇
  2021年   97篇
  2020年   83篇
  2019年   69篇
  2018年   110篇
  2017年   99篇
  2016年   135篇
  2015年   181篇
  2014年   195篇
  2013年   248篇
  2012年   373篇
  2011年   376篇
  2010年   268篇
  2009年   266篇
  2008年   484篇
  2007年   415篇
  2006年   427篇
  2005年   426篇
  2004年   467篇
  2003年   421篇
  2002年   395篇
  2001年   126篇
  2000年   110篇
  1999年   108篇
  1998年   101篇
  1997年   99篇
  1996年   73篇
  1995年   57篇
  1994年   48篇
  1993年   49篇
  1992年   47篇
  1991年   33篇
  1990年   38篇
  1989年   56篇
  1988年   41篇
  1987年   33篇
  1986年   26篇
  1985年   29篇
  1984年   21篇
  1983年   18篇
  1982年   29篇
  1981年   19篇
  1980年   19篇
  1979年   21篇
  1978年   19篇
  1977年   20篇
  1974年   18篇
  1973年   22篇
  1972年   19篇
排序方式: 共有7166条查询结果,搜索用时 46 毫秒
1.
2.
Facet joints play an important role in intervertebral load transmission and are crucial for rotational kinematics. Clinically, the role of facet joints as a possible source of low back pain is seen as controversial and at present is not sufficiently investigated. In this study, human lumbar facet (zygapopyhysial) joints from donors with advanced age were analyzed macroscopically, for degenerative changes. The aim was to determine the extent and morphology of degenerative changes in these joints. Lumbar facet joints (L1–L5) of 32 donors were studied (mean age 80.1±11.2 years). Joint capsules were carefully removed and joint surfaces (5 zones) examined using magnifying glasses and probes. In the result, the majority of facet joints showed cartilage defects of varying extent. Defects were located mostly at the margins of the articular surface, the central zone being relatively well preserved. Defect localization was different between superior (most cartilage defects in superior zone) and inferior (most defects inferiorly) facets. Further, defects were more severe caudal (level of L5) and in older persons. Osteophytes were present in up to 30%, located mostly at the latero-dorsal enthesis of the joint capsule on the superior facet. In conclusion, most margins of the articular facets are subject to degenerative changes in the lumbar spine of elderly persons, the topographical pattern being different in superior and inferior facets. This observation can be explained by the segmental motion patterns during extension/flexion movements of the facets. Sometimes, due to the marginal extension, it is obvious that not all changes can be assessed by CT or MRI.  相似文献   
3.
Adamantinoma of long bones is one of the rarest of malignant bone tumors; it is commonly located in the middle or lower third of the diaphysis of the tibia. A case with multiple occurrences affecting both the tibia and fibula is presented. En bloc resection with wide operative margins was performed, and a large tibial defect of 23 cm was effectively bridged by a revascularized free fibular flap. At 13 months follow-up, there was no sign of local recurrence or metastasis, and the patient was mobile.  相似文献   
4.
5.
Alzheimer's disease (AD) patients often present with concurrent major depression (MD). To investigate the reasons for this comorbidity, e.g. MD being a risk factor for AD, or both diagnoses having a common neurobiology, the temporal relationship between the first onset of AD and of MD during lifetime was investigated-57 out of 146 AD patients had a lifetime diagnosis of MD. The correlation between the ages at onset of MD and dementia was calculated. The incidence of MD in AD patients in several 5-year-intervals before and after the onset of AD was compared with the average incidence of MD in the present AD sample and with the expected incidence of MD in the general population. No significant correlation between the onset of AD and of MD could be found after controlling for age, gender and the Mini-Mental-State. However, the incidence of MD 5 years before and after the onset of AD significantly exceeded the expected incidences-MD is only partially related to AD. However, the increased incidence of MD within 5 years before and after the onset of dementia may indicate that a common neurobiological process causes cognitive decline and depression in a subsample of AD patients.  相似文献   
6.
Growth of malignant tumors is dependent on sufficient blood supply. Thus, inhibition of tumor angiogenesis is emerging as a promising target in the treatment of malignancies. Human angiostatin (hANG) is one of the most potent inhibitors of endothelial cell proliferation, angiogenesis, and tumor growth in vivo. However, its mechanisms operating in vivo are not well understood. METHODS: To obtain more information about functional changes in the angiogenic process, we established Morris hepatoma (MH3924A) cell lines expressing hANG (hANG-MH3924A). The effects of hANG expression on proliferation and apoptosis of human umbilical vein endothelial cells (HUVECs) were measured in coculture experiments in vitro. To evaluate changes in tumor perfusion and blood volume, H2 15O and 68Ga-DOTA-albumin (DOTA is 1,4,7,10-tetraazacyclododecane-N,N',N',N'-tetraacetic acid) were used for PET studies in vivo. Additionally, immunohistologic quantification of vascularization, apoptosis, and proliferation as well as gene array analyses were performed. RESULTS: Our in vitro experiments demonstrate reduced proliferation and increased apoptosis in HUVECs when being cocultured with hANG-MH3924A. In support, tumor growth of hANG-MH3924A is diminished by 95% in vivo. However, tumor perfusion and blood volume are increased in hANG-MH3924A corresponding to an increased microvessel density. Furthermore, hANG-transfected tumors show changes in expression of genes related to apoptosis, stress, signal transduction, and metabolism. CONCLUSION: hANG expression leads to inhibition of tumor growth, increased apoptosis, and changes in the expression of multiple genes involved in stress reactions, signal transduction, and apoptosis, which indicates a multifactorial reaction of tumors. An enhanced microvessel density is seen as part of these reactions and is associated with increased perfusion as measured by PET.  相似文献   
7.
8.
9.
Lymphocytes continuously migrate through the body, and their efficient extravasation from the blood via high endothelial venules (HEV) is essential for initiating an appropriate immune response. Most investigations have focused on the lymphocyte/HEV interaction in vitro. However, to what extent such systems reflect the situation in vivo is not known. It is also unclear whether lymphocyte subsets immigrate into the HEV in proportion to their presence in the blood, and whether import capacity is limited by the HEV. When rat mesenteric lymph node lymphocytes were incubated in vitro on cryostat sections, the well-known preferential binding of B lymphocytes to HEV of Peyer's patches (PP) and T cells to HEV of axillary lymph nodes (axLN) was observed (axLN vs. PP: B lymphocytes 21.2 ± 5.0% vs. 40.6 ± 11.0%, T lymphocytes 84.6 ± 6.3% vs. 56.5 ± 12.9%). However, when labeled mesenteric lymph node lymphocytes were injected and their location within the HEV was analyzed 15 min later, no preferential interaction was seen. After injection of labeled thoracic duct lymphocytes, the percentage of labeled cells among B and T lymphocytes in the blood was significantly different (4.4 ± 0.9% vs. 8.9 ± 3.6%), whereas that in HEV of axLN (19.0 ± 6.4% vs. 16.6 ± 6.0%) and PP (30.6 ± 6.1% vs. 33.9 ± 4.4%) was comparable. Although the number of injected lymphocytes was similar in magnitude to the total blood lymphocyte pool, after injection there was no increase in lymphocyte numbers in the HEV. Thus, the adhesion assay in vitro does not completely reflect immigration into HEV in vivo. In addition, our data suggest that both the availability of lymphocyte subsets in small venules and the immigration rate into HEV are actively regulated in vivo.  相似文献   
10.
We report on the successful regrafting of a transplanted liver. The donor liver was first grafted into a patient suffering from cryptogenic cirrhosis; the patient died 1 day after the elective transplantation of cerebral bleeding. The well-functioning graft was harvested again and transferred to our institution. After another 12 h of cold ischemia, the liver was reperfused in an urgently registered patient with recurrence of hepatitis B in his first graft. The transplantation was successfully performed and the patient is now doing well, more than 5 months after regrafting with the reused liver. Received: 21 October 1996 Received after revision: 9 January 1997 Accepted: 27 January 1997  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