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   3341篇
  免费   178篇
  国内免费   10篇
耳鼻咽喉   13篇
儿科学   72篇
妇产科学   87篇
基础医学   418篇
口腔科学   101篇
临床医学   196篇
内科学   780篇
皮肤病学   147篇
神经病学   307篇
特种医学   84篇
外科学   582篇
综合类   14篇
预防医学   90篇
眼科学   54篇
药学   227篇
中国医学   8篇
肿瘤学   349篇
  2022年   32篇
  2021年   61篇
  2020年   24篇
  2019年   32篇
  2018年   52篇
  2017年   32篇
  2016年   58篇
  2015年   56篇
  2014年   75篇
  2013年   88篇
  2012年   131篇
  2011年   144篇
  2010年   94篇
  2009年   90篇
  2008年   145篇
  2007年   177篇
  2006年   161篇
  2005年   176篇
  2004年   149篇
  2003年   204篇
  2002年   186篇
  2001年   127篇
  2000年   107篇
  1999年   100篇
  1998年   34篇
  1997年   38篇
  1996年   30篇
  1995年   26篇
  1994年   28篇
  1993年   35篇
  1992年   94篇
  1991年   89篇
  1990年   67篇
  1989年   61篇
  1988年   43篇
  1987年   52篇
  1986年   47篇
  1985年   55篇
  1984年   48篇
  1983年   40篇
  1982年   13篇
  1980年   16篇
  1979年   36篇
  1978年   14篇
  1977年   15篇
  1976年   14篇
  1972年   14篇
  1971年   23篇
  1970年   11篇
  1967年   13篇
排序方式: 共有3529条查询结果,搜索用时 107 毫秒
81.
A 58-year-old woman presented with muscle weakness, whole body myalgia, and dyspnea. On admission, neurological examination showed proximal muscle weakness in the extremities. The weakness gradually extended to the bulbar and respiratory muscles, necessitating an artificial ventilator. Serum CK level was markedly increased (33,774 IU/L; normal <150 IU/L) and myoglobinuria was noted in urinalysis. There was no sign of renal failure. Nerve conduction study was normal, but needle EMG showed myopathic changes in the weak muscles. Serological studies for virus titers showed more than a four-fold increase of cytomegalovirus (CMV) antibody titer during the disease course. The IgM anti-GM2 antibody was also elevated in the acute phase and decreased in the recovery phase. The muscle weakness and respiratory failure gradually improved after intravenous methylprednisolone administration, and the serum CK level was normalized in several days. CMV infection was thought to have played a central role in the rhabdomyolysis, leading to critical but reversible respiratory muscle paralysis.  相似文献   
82.
We have shown previously that Cyp11b1, an 11beta-hydroxylase responsible for glucocorticoid biosynthesis in the adrenal gland, was induced by cAMP in androgen-producing Leydig-like cells derived from mesenchymal stem cells. We found that Cyp11b1 was induced in male Leydig cells, or female theca cells, when human chorionic gonadotropin was administered in immature mice. Expression of Cyp11b1 in rodent gonads caused the production of 11-ketotestosterone (11-KT), a major fish androgen, which induces male differentiation or spermatogenesis in fish. As in teleosts, plasma concentrations of 11-KT were elevated in human chorionic gonadotropin-treated mice. In contrast to teleosts, however, plasma concentrations of 11-KT were similar in both sexes, despite levels of testosterone, a precursor substrate, being about 20 times higher in male mice. Because expression of 11beta-hydroxysteroid dehydrogenase type 2, was much higher in the mouse ovary than in the testis, conversion of testosterone into 11-KT may occur more efficiently in the ovary. In a luciferase reporter system that was responsive to and activated by androgens, 11-KT efficiently activated mammalian androgen receptor-mediated transactivation. Our results suggest that the androgen metabolic pathway is conserved between teleosts and mammals, despite sexual dominance and reproductive functions of 11-KT being altered during evolution.  相似文献   
83.
Circulating immune complexes as measured by conglutinin (IgG-IC) and IgM rheumatoid factor (IgM-RF) were studied in 114 patients with mycoplasmal pneumonia (58 inpatients and 56 outpatients). The levels of IgG-IC and IgM-RF of the patients were significantly higher than those of 13 healthy control subjects. In addition, the levels of IgG-IC of the inpatients were significantly higher than those of the outpatients. The highest titers of IgG-IC were obtained 9 to 30 days after onset of disease, and the levels of IgG-IC were elevated during the time period when pulmonary changes were pronounced. The levels of IgM-RF were irrelevant to infiltration on chest radiographs. An analysis using density gradient centrifugation showed that the decrease of IgG-IC with intermediate size was associated with improvement of the disease. A possible pathogenic role of IgG-IC in mycoplasmal pneumonia is discussed.  相似文献   
84.
Human term placental explants were used to investigate the possible role of phospholipid-sensitive and Ca2+ dependent protein kinase in the regulation of human placental progesterone production. Placental tissue was incubated with low density lipoprotein as a precursor of progesterone in the presence or the absence of phorbol 12-myristate-13-acetate, 1-oleoyl-2-acetyl-glycerol, and the calcium ionophore A23187. The rate of progesterone production by placental tissue was 21.7 +/- 4.6 ng. (mg wet wt)-1.(2 h)-1 (mean +/- SEM) with 500 mg low density lipoprotein/l (control). The rate of progesterone production was accelerated 2-fold by 1 nmol/l phorbol 12-myristate-13-acetate, 1.6-fold by 250 mumol/l 1-oleoyl-2-acetyl-glycerol and this increase was dose-related (25-250 mumol/l 1-oleoyl-2-acetyl-glycerol). A nonpromoting derivative, 4 alpha-phorbol-12,13-didecanoate had no effect. The phorbol 12-myristate-13-acetate or 1-oleoyl-2-acetyl-glycerol induced stimulation of progesterone production was not associated with a change in the intracellular cAMP level. Addition of 10 mumol/l A23187 further increased progesterone production with 125 mumol/l 1-oleoyl-2-acetyl-glycerol. The rate of progesterone production was accelerated 1.6-fold by 125 mumol/l 1-oleoyl-2-acetyl-glycerol and 10 mumol/l A23187 as compared with control. The effects of the phorbol ester and the diacyl glycerol were completely blocked by the addition of the protein synthesis inhibitor cycloheximide. We conclude that these phorbol regents are able to stimulate human placental progesterone production. The possible roles of intracellular Ca2+ and protein kinase C in placental steroidogenesis are discussed.  相似文献   
85.
Recently, it has become evident that elevated levels of plasminogen activator inhibitor-1 (PAI-1) are associated with myocardial infarction and stroke, especially in patients with diabetes. The molecular mechanisms involved in hyperglycemia-induced PAI-1 expression in bovine aortic endothelial cells (BAEC) were investigated. PAI-1 expression in BAEC was significantly increased in accordance with the concentration of glucose in media from 5.7 mM to 23 mM. Stimulation with high glucose (23 mM) significantly increased small GTPase Rho A activation. Pretreatment with a Rho-kinase inhibitor, Y-27632 (1-10 microM), significantly blocked high glucose-induced PAI-1 expression. NF-kappaB activity determined using the luciferase reporter gene assay was significantly enhanced by high glucose, and pretreatment with Y-27632 inhibited high glucose-induced PAI-1 expression at the basal level. An inhibitor of NF-kappaB action, namely parthenolide (0.1 microM), BAY 11-7082 (5 microM) and SN50 (1 microM), significantly blocked high glucose-mediated PAI-1 expression to a level with low glucose (5.7 mM). These data suggested that high glucose-induced PAI-1 expression in endothelial cells is mediated by NF-kappaB activation through the Rho/Rho-kinase pathway. Inhibition of Rho/Rho-kinase signaling might be a novel target for diabetes and metabolic syndrome.  相似文献   
86.
The gastrointestinal tract is a rare site for metastatic lung cancer. Programmed cell death-ligand 1 (PD-L1) expression in lung cancer is a biomarker for the response to anti-PD-1/PD-L1 therapy. We investigated clinicopathological features and PD-L1 expression in 25 gastrointestinal metastatic tumors from the lung and primary adenocarcinoma of the small bowel. The small bowel was the most common site (16/25; 64%) of gastrointestinal tract lung cancer metastasis. A total of 19 (76%) of the gastrointestinal metastasis showed PD-L1 expression in ≥5% of tumor cells, with 14 (56%) showing high expression levels (≥50%). In contrast, 21 (84%) expressed PD-L1 in ≥5% immune cells, including 4 (16%) showing a high expression levels (≥50%). The PD-L1 expression on tumor cells and immune cells in primary lung cancer and corresponding gastrointestinal metastasis was concordant in 13 (68%) and 11 (58%) of the 19 paired cases, respectively. Small-bowel metastasis of lung cancer was characterized by a higher incidence of perforation (31% vs. 0%), ulcerated mass (83% vs. 60%), and neoplastic PD-L1 expression (75% vs. 0%) compared to primary small-bowel adenocarcinoma. Gastrointestinal metastasis from lung cancer might be a potential target for immune checkpoint inhibitor therapy, given its high expression of PD-L1.  相似文献   
87.
Objectives:To evaluate the condyle-fossa relationship in adolescents with various skeletal patterns using cone-beam computed tomography (CBCT).Materials and Methods:CBCT images obtained in 120 adolescent patients were used for this study. The patients were divided into 3 groups according to 3 criteria: (1) age (early, middle, and late adolescence); (2) facial height ratio or Jarabak quotient (hyperdivergent, normodivergent, and hypodivergent); and (3) ANB classification (Class I, Class II, and Class III). Temporomandibular joint space (TMJS: AS, anterior space; SS, superior space; PS, posterior space; MS, medial space; LS, lateral space), width and depth of the condyle (MLT, mediolateral thickness; APT, anteroposterior thickness), articular slope (ArS) and vertical height of the fossa (VHF) were measured and compared using CBCT.Results:Differences in condyle-fossa relationships were not significantly different between male and female adolescents, but were significantly different (P < .05) between left and right sides. The mean values showed no statistical differences according to age and skeletal pattern. Most measurements in the sagittal view showed that SS was the greatest, and the mean ratio of AS to SS to PS was 1.00 to 1.27 to 1.19, respectively. The mean values of coronal MS and LS were not significantly different.Conclusions:There were almost no statistical differences in the TMJS in adolescents across various factors except between left and right sides.  相似文献   
88.
89.
We evaluated the minimum alveolar concentration of sevoflurane required to maintain the bispectral index below 50 in children. We studied 55 children, divided into 1‐year‐old, 2‐ to 4‐year‐old and 5‐ to 9‐year‐old groups and used Dixon's up‐and‐down method and probit analysis. In the 1‐year‐old group, the bispectral index values remained above 50, with the end‐tidal sevoflurane concentration reaching 4.0% or higher. The minimum alveolar concentration of sevoflurane for maintaining the bispectral index below 50 was significantly higher in the 2‐ to 4‐year‐old group (2.33%, 95% CI 2.25–2.57) than in the 5‐ to 9‐year‐old group (2.10%, 95% CI 1.94–2.25; p = 0.005). We conclude that assessing the depth of anaesthesia using bispectral index is unreliable in children aged < 2 years anaesthetised with sevoflurane.  相似文献   
90.
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