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   523869篇
  免费   33847篇
  国内免费   679篇
耳鼻咽喉   7001篇
儿科学   17025篇
妇产科学   13664篇
基础医学   86153篇
口腔科学   14698篇
临床医学   44991篇
内科学   96249篇
皮肤病学   12273篇
神经病学   36786篇
特种医学   18846篇
外国民族医学   63篇
外科学   78853篇
综合类   8531篇
一般理论   119篇
预防医学   39260篇
眼科学   12423篇
药学   41078篇
中国医学   1021篇
肿瘤学   29361篇
  2018年   5143篇
  2016年   4298篇
  2015年   4711篇
  2014年   6360篇
  2013年   9826篇
  2012年   13318篇
  2011年   14820篇
  2010年   8635篇
  2009年   8026篇
  2008年   14067篇
  2007年   15134篇
  2006年   15386篇
  2005年   14808篇
  2004年   14468篇
  2003年   13752篇
  2002年   13651篇
  2001年   24391篇
  2000年   25401篇
  1999年   20837篇
  1998年   5535篇
  1997年   4786篇
  1996年   5112篇
  1995年   4703篇
  1994年   4383篇
  1992年   15974篇
  1991年   16506篇
  1990年   16621篇
  1989年   16023篇
  1988年   14759篇
  1987年   14612篇
  1986年   13777篇
  1985年   13144篇
  1984年   9742篇
  1983年   8345篇
  1982年   4594篇
  1981年   4257篇
  1979年   9507篇
  1978年   6920篇
  1977年   5821篇
  1976年   5629篇
  1975年   6434篇
  1974年   7671篇
  1973年   7169篇
  1972年   7002篇
  1971年   6726篇
  1970年   6213篇
  1969年   5920篇
  1968年   5605篇
  1967年   5048篇
  1966年   4479篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
We have examined immunohistochemically the presence of human chorionic gonadotrophin (hCG) in 29 esophageal carcinomas: 24 squamous cell carcinomas, 2 adenocarcinomas, 2 adenoid cystic carcinomas and 1 adenosquamous carcinoma. In hCG-positive tumors, the presence of human placental lactogen (hPL) and pregnancy-specific beta-1 glycoprotein (SP-1) was also assessed. HCG immunoreactive cells were found in 5 squamous cell carcinomas (21%) and in none of 5 non-squamous cell tumors. The hCG positive cells were found in the most infiltrating areas of the tumors where poorly differentiated and pleomorphic cells predominated. The positive tumors were 4 poorly differentiated (31%) and one moderately differentiated carcinoma (12%). Four out of 10 cases (40%) with lymph node metastases had hCG in the primary tumor, whereas only one out of 11 cases (9%) without metastases was hCG positive. HPL and SP-1 were found in two cases. These placental proteins were detected in similar areas than hCG but the number of hPL and SP-1 immunoreactive cells was lower than hCG positive cells. SP-1 was also seen in areas of squamous cell differentiation negative for hCG. None of these two cases showed trophoblastic differentiation.  相似文献   
992.
Vascular lesions in Beh?et's disease are generally localized in the venous system: up to 24% of the cases reported in the literature are accompanied by thrombosis/thrombophlebitis. Reports of arterial involvement are rare but have increased during the last decade. Surgical treatments of arterial aneurysms and occlusions are often followed by recurrences due to progression or relapses of the inflammatory vessel wall lesions. Aneurysms of the pulmonary artery are rare. They may be complicated by thrombosis within the aneurysm and massive hemoptysis due to bronchial erosion and formation of an arterio-bronchial fistula. 27 cases of Beh?et's disease are reported.  相似文献   
993.
994.
We studied 14 patients from three unrelated Belgian pedigrees with a familial mitochondrial disorder and multiple deletions of mitochondrial DNA (mtDNA). In one family with an oculopharyngeal presentation there is a clear autosomal dominant inheritance. Progressive external ophthalmoplegia (PEO), “ragged red fibres” (RRF) and multiple deletions of mtDNA are common to all three families. Therefore a diagnosis of autosomal dominant progressive ophthalmoplegia with multiple deletions of mtDNA (adPEO) was made in one family at least. Our data confirm the previous observations that adPEO is a systemic disorder rather than a pure myopathy. In our pedigrees frequently associated features include axonal peripheral neuropathy, dysphagia, psychiatric illness, and sudden death. Mild ataxia, pes cavus and mitral valve prolapse with associated mitral insufficiency also occur. In some cases onset is atypical with neuropathy, adolescent onset myopathy or psychiatric illness. In such cases the common features of PEO and muscle weakness always complete the clinical phenotype later during the course of the disease. Biochemical studies on mitochondrial fractions prepared from one patient's muscle, revealed no abnormalities of respiratory chain enzyme activities.  相似文献   
995.
996.
Haemophilus influenzae causing conjunctivitis in day-care children   总被引:1,自引:0,他引:1  
The role of Haemophilus influenzae in acute purulent conjunctivitis was studied during an outbreak among children in day care. Five day-care centers contributed 20 cases and 35 controls. All the children were subjected to culture of the nasopharynx and the eyes. H. influenzae was carried in the nasopharynx of 53% of the children (range between day care centers, 20 to 91%). Of the 20 children with acute conjunctivitis 8 had eye cultures positive for H. influenzae, 2 had Moraxella and the remaining were culture-negative. Ten colonies of H. influenzae were isolated from each positive culture and identified by capsular type, biotype and multi-locus enzyme electrophoresis. All but one of the isolates were nonencapsulated. They belonged to 4 biotypes and 8 electrophoretic types. The same strain was recovered from the eyes and nasopharynx of the symptomatic children, suggesting that the H. influenzae in the eyes originated from the nasopharynx. There was no evidence for spread of the same H. influenzae strains between day-care centers. Even within each center the Haemophilus strains recovered from the eyes varied among the symptomatic children. The in vitro capacity to attach to oropharyngeal epithelial cells was not increased among the H. influenzae recovered from the eyes. The results question if the majority of conjunctivitis cases were caused by H. influenzae and suggested that eyes were colonized with the nasopharyngeal carrier strain rather than infected by an isolate with special virulence for the eye.  相似文献   
997.
A case of successful quadruplet pregnancy followed from date of diagnosis, through delivery, and to the third year of life is presented. The emotional, social, and economic problems encountered by the parents and hospital personnel are examined with a detailed analysis of the financial burden placed on all parties. Individual, voluntary donations made at the time of delivery have proved insufficient to cover the care involved before, during, and after the birth of multiples. A more concrete commitment on the part of government in the form of legislation or subvention is suggested in order to ease some of the stress on the parents of multiples.  相似文献   
998.
The role of lymphokines was estimated in induction of autoreactive T-cells during Langat virus infection in mice. It was shown that in vitro cultured splenocytes from virus-infected animal containing autoreactive lymphocytes (ARL) spontaneously produce a lymphokine which is capable to activate the autoreactivity of lymphocytes derived from the spleen of intact syngeneic mice. The capacity of this lymphokine to activate the autoreactivity of acceptor cells within 2 hr was demonstrated by local graft-versus host reaction (GVHR) in the donor-recipient system. According to their surface markers (theta-antigen expression, absence of immunoglobulins) the lymphokine activating autoreactivity (LAA) producers may belong to T-lymphocyte population. Autoreactivity could be induced by the lymphokine only if the LAA producers and acceptors were compatible by the major histocompatibility complex antigens.  相似文献   
999.
1000.
31P, 1H and lactate spectroscopic imaging was used to evaluate the effects of hypothermia on focal cerebral ischemia produced by middle cerebral artery occlusion. The effects on high energy phosphate metabolism, pH, lactate and NAA were investigated in 24 spontaneously hypertensive rats subjected to either permanent or transient ischemia. Under either normothermic (37.5°C) or hypothermic (32°C) conditions, with permanent 6-h occlusion, there was little difference between groups in either the NMR measurements or the volume of infarction. In animals that underwent 3 h of ischemia followed by 12 h of reperfusion, the ischemic changes in lactate, pH, NAA, and high-energy phosphate returned toward control values, and there was a protective effect of hypothermia (infarct volume of 211 ± 26 and 40 ± 14 mm3 in normothermic and hypothermic groups, respectively). Thus, hypothermia did not ameliorate the changes in lactate, pH, NAA, or high energy phosphate levels occurring during ischemia, however, during reperfusion there was an improvement in both the recovery of these metabolites and pathological outcome in hypothermic compared with normothermic animals.  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