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   6705篇
  免费   413篇
  国内免费   34篇
耳鼻咽喉   51篇
儿科学   153篇
妇产科学   41篇
基础医学   872篇
口腔科学   184篇
临床医学   413篇
内科学   1952篇
皮肤病学   67篇
神经病学   502篇
特种医学   152篇
外科学   1149篇
综合类   37篇
预防医学   154篇
眼科学   251篇
药学   474篇
中国医学   16篇
肿瘤学   684篇
  2023年   53篇
  2022年   116篇
  2021年   169篇
  2020年   108篇
  2019年   126篇
  2018年   143篇
  2017年   151篇
  2016年   159篇
  2015年   172篇
  2014年   161篇
  2013年   209篇
  2012年   363篇
  2011年   390篇
  2010年   222篇
  2009年   211篇
  2008年   344篇
  2007年   376篇
  2006年   353篇
  2005年   305篇
  2004年   284篇
  2003年   299篇
  2002年   308篇
  2001年   257篇
  2000年   240篇
  1999年   195篇
  1998年   93篇
  1997年   46篇
  1996年   65篇
  1995年   46篇
  1994年   33篇
  1993年   25篇
  1992年   110篇
  1991年   102篇
  1990年   87篇
  1989年   86篇
  1988年   91篇
  1987年   85篇
  1986年   92篇
  1985年   72篇
  1984年   56篇
  1983年   38篇
  1982年   17篇
  1980年   22篇
  1979年   32篇
  1975年   27篇
  1974年   24篇
  1972年   20篇
  1968年   16篇
  1967年   19篇
  1966年   17篇
排序方式: 共有7152条查询结果,搜索用时 15 毫秒
61.
The malignant transformation of mature cystic teratoma is rare, thus occurring in only 1-2% of all cases. The most common malignancy arising in mature cystic teratoma is squamous cell carcinoma. Adenocarcinoma occurs with less frequency. We herein present a patient with an ovarian mature cystic teratoma who demonstrated a malignant transformation to well-differentiated adenocarcinoma. Malignant transformation was diagnosed preoperatively by contrast enhanced computed tomography (CT) and magnetic resonance imaging (MRI). Microscopically and immunohistochemically, the adenocarcinoma was considered to have arisen from the ciliated respiratory epithelium. After a 28-month of follow-up period, she remains free of the disease. This is the third reported case of adenocarcinoma arising in the respiratory epithelium of an ovarian mature cystic teratoma. Contrast enhanced CT and MRI are useful for making a preoperative diagnosis and an immunohistochemical study is helpful for defining its origin.  相似文献   
62.
Background: The importance of maintaining good mental health with overall well-being has recently drawn attention from various spheres of academics and the working population. Amino acid intake has been reported to reduce depression symptoms and other mental health problems. However, the effectiveness of amino acid intake (i.e., single or combined) remains unknown. In this study, we assessed a combination of five amino acids (serine, alanine, glutamate, aspartate, and tyrosine; SAGAT) reported to regulate mental health. Methods: A randomized, double-blind, placebo-controlled exploratory trial was conducted. Participants, aged between 20 and 65 years with fatigue sensation, were randomized to receive either SAGAT or the placebo and ingested them for four weeks. A transient mental work was loaded at day 0 and after four weeks of intervention. As the primary outcomes, the fatigue sensation was assessed. The mood status, cognitive function, work efficiency, and blood marker were also measured as secondary outcomes. Results: The number of participants analyzed for the efficacy evaluation were 20 in SAGAT and 22 in the placebo. There were no significant differences in the primary outcomes. However, as the secondary outcomes, the SAGAT group showed a significant improvement in motivation and cognitive function in the recovery period after mental work loaded in a four-week intervention compared to the placebo. Conclusion: The current findings suggest that SAGAT contributes to maintaining proper motivation and cognitive function. Clinical Trial Registration: University Hospital Medical Information Network Clinical Trial Registry (ID: UMIN 000041221).  相似文献   
63.
Unidentified Mycobacterium species are sometimes detected in respiratory specimens. We identified a novel Tsukamurella species (Tsukamurella sp. TY48, RIMD 2001001, CIP 111916T), Tsukamurella toyonakaense, from a patient given a misdiagnosis of nontuberculous mycobacterial pulmonary disease caused by unidentified mycobacteria. Genomic identification of this Tsukamurella species helped clarify its clinical characteristics and epidemiology.  相似文献   
64.
Attenuation of endothelium-dependent relaxation in aorta from diabetic rats   总被引:25,自引:0,他引:25  
Endothelium-dependent relaxation was examined in aortic ring preparations obtained from rats with streptozotocin-induced diabetes. The endothelium-dependent relaxation which was produced by acetylcholine and histamine in aortic rings precontracted with norepinephrine was significantly attenuated in aortic rings from diabetic rats when compared with the relaxation in rings from age-matched control animals. However, the relaxation induced by sodium nitroprusside (an endothelium-independent relaxant agent) in diabetic preparations was comparable to the control. These results show that diabetes leads to an impairment of the endothelium-dependent relaxation of aorta.  相似文献   
65.
Chondroitin sulfate (CS) is an important glycosaminoglycan and is mainly found in the extracellular matrix as CS proteoglycans. In the brain, CS proteoglycans are highly concentrated in perineuronal nets (PNNs), which surround synapses and modulate their functions. To investigate the importance of CS, we produced and precisely examined mice that were deficient in the CS synthesizing enzyme, CSGalNAcT1 (T1KO). Biochemical analysis of T1KO revealed that loss of this enzyme reduced the amount of CS by approximately 50% in various brain regions. The amount of CS in PNNs was also diminished in T1KO compared to wild-type mice, although the amount of a major CS proteoglycan core protein, aggrecan, was not changed. In T1KO, we observed abnormalities in several behavioral tests, including the open-field test, acoustic startle response, and social preference. These results suggest that T1 is important for plasticity, probably due to regulation of CS-dependent PNNs, and that T1KO is a good model for investigation of PNNs.  相似文献   
66.

Purpose

Although both sevoflurane and isoflurane are thought to be less hepatotoxic than halothane or enflurane, recent case reports have described liver injury after sevoflurane or isoflurane anaesthesia. There are no studies comparing liver function after sevoflurane or isoflurane anaesthesia. The purpose of this study was to compare serum liver enzyme concentrations in patients receiving either sevoflurane or isoflurane anaesthesia prospectively.

Methods

Ninety patients scheduled for elective neurosurgery were studied. Serum concentrations of aspartame aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin (TBil), alkaline phosphatase (ALP), γ- glutamyl transpeptidase (GTP), and lactate dehydrogenase (LDH) were measured before and, 1, 2, 3, 7, and 14 days after either sevoflurane (45 patients) or isoflurane (45 patients) anaesthesia.

Results

AST ALT and GTP increased peaking seven days after anaesthesia, especially in the isoflurane group. The numbers of patients with abnormal values in AST and ALT were not different in the isoflurane from that in the sevoflurane group. The increase in TBil peaked one day after anaesthesia in both groups.

Conclusion

Even in a small number of patients, isoflurane induced an elevation of serum levels of liver enzymes more frequently than did sevoflurane three to 14 days after anaesthesia.  相似文献   
67.
Management of pancreatic mass accompanying chronic pancreatitis   总被引:1,自引:0,他引:1  
We report two patients with focal, chronic pancreatitis that was diagnosed by dynamic computed tomography (CT) combined with intraoperative biopsy. In case 1, serum carbohydrate antigen (CA) 19-9 level rose to 160 U/ml. Abdominal ultrasonography, CT, and magnetic resonance imaging demonstrated a mass, of 4.5 cm in diameter, in the pancreatic head. On dynamic CT, the mass was enhanced similarly to the normal pancreatic parenchyma. In case 2, dynamic CT demonstrated a mass, of 3.0 cm in diameter, in the pancreatic head, which was enhanced similarly to the normal pancreatic parenchyma. From such characteristics of enhancement, both masses were suspected to be chronic pancreatitis rather than cancer, and the diagnosis was confirmed by intraoperative biopsy. Three years in case 1 and 2 years in case 2 have passed since their operations, and the size of each mass has not changed. With the use of dynamic CT combined with intraoperative biopsy, focal chronic pancreatitis could be diagnosed more accurately, and this may lead to a reduction in unnecessary pancreatic resection. Received: November 16, 2001 / Accepted: February 8, 2002  相似文献   
68.
OBJECTIVE: To better determine the role of portal vein resection and its effect on survival, as well as to appreciate the impact of portal vein invasion on prognosis in hilar cholangiocarcinoma. SUMMARY BACKGROUND DATA: Hepatectomy with portal vein resection is sometimes performed for locally advanced hilar cholangiocarcinoma. However, the significance of microscopic invasion of the portal vein has not been determined. METHODS: Medical records of 160 patients with hilar cholangiocarcinoma who underwent macroscopically curative hepatectomy with (n = 52) or without portal vein resection (n = 108) were reviewed. Invasion of the portal vein was assessed histologically on the surgical specimen, and results were correlated with clinicopathologic features and survival. RESULTS: Surgical mortality, including all hospital deaths, was similar in patients who did and did not undergo portal vein resection (9.6% vs. 9.3%), but the primary tumor was more advanced in patients who underwent portal vein resection. Histologically, no invasion was found in 16 (30.8%) of resected portal veins. However, dense fibrosis adjacent to the portal vein was common, and the mean distance between the leading edge of cancer cells and the adventitia of the portal vein was 437 +/- 431 mum. The prognosis was worse in patients with than without portal vein resection (5-year survival, 9.9% vs. 36.8%; P < 0.0001). The presence or absence of microscopic invasion of the resected portal vein did not influence survival (16.6 months in patients with microscopic invasion vs. 19.4 months in those without; P = 0.1506). Multivariate analysis identified histologic differentiation, lymph node metastasis, and macroscopic portal vein invasion as independent prognostic factors. CONCLUSIONS: Microscopic invasion of the portal vein may be misdiagnosed clinically in patients with hilar cholangiocarcinoma. However, the distance between tumor and adventitia is so narrow that curative resection without portal vein resection is unlikely to be possible. Gross portal vein invasion has a negative impact on survival, and hepatectomy with portal vein resection can offer long-term survival in some patients with advanced hilar cholangiocarcinoma.  相似文献   
69.
70.
The family Arenaviridae, genus Arenavirus, consists of two phylogenetically independent groups: Old World (OW) and New World (NW) complexes. The Lassa and Lujo viruses in the OW complex and the Guanarito, Junin, Machupo, Sabia, and Chapare viruses in the NW complex cause viral hemorrhagic fever (VHF) in humans, leading to serious public health concerns. These viruses are also considered potential bioterrorism agents. Therefore, it is of great importance to detect these pathogens rapidly and specifically in order to minimize the risk and scale of arenavirus outbreaks. However, these arenaviruses are classified as BSL-4 pathogens, thus making it difficult to develop diagnostic techniques for these virus infections in institutes without BSL-4 facilities. To overcome these difficulties, antibody detection systems in the form of an enzyme-linked immunosorbent assay (ELISA) and an indirect immunofluorescence assay were developed using recombinant nucleoproteins (rNPs) derived from these viruses. Furthermore, several antigen-detection assays were developed. For example, novel monoclonal antibodies (mAbs) to the rNPs of Lassa and Junin viruses were generated. Sandwich antigen-capture (Ag-capture) ELISAs using these mAbs as capture antibodies were developed and confirmed to be sensitive and specific for detecting the respective arenavirus NPs. These rNP-based assays were proposed to be useful not only for an etiological diagnosis of VHFs, but also for seroepidemiological studies on VHFs. We recently developed arenavirus neutralization assays using vesicular stomatitis virus (VSV)-based pseudotypes bearing arenavirus recombinant glycoproteins. The goal of this article is to review the recent advances in developing laboratory diagnostic assays based on recombinant viral proteins for the diagnosis of VHFs and epidemiological studies on the VHFs caused by arenaviruses.  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