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   4974篇
  免费   275篇
  国内免费   13篇
耳鼻咽喉   25篇
儿科学   108篇
妇产科学   105篇
基础医学   585篇
口腔科学   115篇
临床医学   272篇
内科学   1306篇
皮肤病学   169篇
神经病学   462篇
特种医学   124篇
外科学   935篇
综合类   17篇
预防医学   124篇
眼科学   102篇
药学   253篇
中国医学   10篇
肿瘤学   550篇
  2023年   36篇
  2022年   78篇
  2021年   135篇
  2020年   79篇
  2019年   90篇
  2018年   129篇
  2017年   88篇
  2016年   105篇
  2015年   122篇
  2014年   146篇
  2013年   159篇
  2012年   255篇
  2011年   269篇
  2010年   156篇
  2009年   147篇
  2008年   232篇
  2007年   263篇
  2006年   245篇
  2005年   262篇
  2004年   243篇
  2003年   270篇
  2002年   247篇
  2001年   141篇
  2000年   112篇
  1999年   110篇
  1998年   57篇
  1997年   44篇
  1996年   45篇
  1995年   36篇
  1994年   35篇
  1993年   43篇
  1992年   102篇
  1991年   94篇
  1990年   71篇
  1989年   65篇
  1988年   49篇
  1987年   59篇
  1986年   51篇
  1985年   53篇
  1984年   51篇
  1983年   40篇
  1982年   17篇
  1980年   21篇
  1979年   37篇
  1978年   15篇
  1977年   17篇
  1976年   16篇
  1972年   14篇
  1971年   23篇
  1967年   13篇
排序方式: 共有5262条查询结果,搜索用时 15 毫秒
71.
RATIONALE: Adrenomedullin, a potent vasodilator peptide, regulates cell growth and survival. However, whether adrenomedullin contributes to lung regeneration remains unknown. OBJECTIVES: To investigate whether adrenomedullin influences the kinetics of bone marrow cells, and whether adrenomedullin promotes regeneration of alveoli and vasculature and thereby improves lung structure and function in elastase-induced emphysema in mice. METHODS: Adrenomedullin or vehicle was randomly administered to C57BL/6 mice for 5 days. We counted the numbers of mononuclear cells and stem cell antigen-1-positive cells in circulating blood. After intratracheal injection of elastase or saline, mice were randomized to receive continuous infusion of adrenomedullin or vehicle for 14 days. Functional and histologic analyses were performed 28 days after treatment. RESULTS: Twenty-eight days after elastase injection, destruction of the alveolar walls was observed. However, adrenomedullin infusion significantly inhibited the increase in lung volume, static lung compliance, and mean linear intercept in mice given elastase. Adrenomedullin increased the numbers of mononuclear cells and stem cell antigen-1-positive cells in circulating blood. Adrenomedullin significantly increased the number of bone marrow-derived cells incorporated into the elastase-treated lung. Some of these cells were positive for cytokeratin or von Willebrand factor. Infusion of adrenomedullin after the establishment of emphysema also had beneficial effects on lung structure and function. In vitro, addition of adrenomedullin attenuates elastase-induced cell death in alveolar epithelial cells and endothelial cells. CONCLUSIONS: Adrenomedullin improved elastase-induced emphysema at least in part through mobilization of bone marrow cells and the direct protective effects on alveolar epithelial cells and endothelial cells.  相似文献   
72.
73.
We observed the quantitative estimation of the transmural changes associated with gastric ulcer healing by using endoscopic ultrasonography (EUS). It was possible to diagnose the depth of ulcer by EUS. Forty-eight patients were divided into three treatment groups. Group A (n = 16) was treated with 800 mg cimetidine daily, group B (n = 22) with 20 mg omeprazole daily, and group C (n = 10) with 400 mg cimetidine + 300 mg gefarnate daily. EUS was performed before and after 2, 4, and 8 weeks of treatment. The groups were compared from the viewpoints of endoscopic findings and contraction rate of the length and the cross-sectional area of the ulcer in EUS pictures. The best healing of both the endoscopic and EUS findings was seen in group B. By estimating the changes inside the ulcer, EUS may provide useful information for choice of anti-ulcer agents.  相似文献   
74.
75.
A 50-year-old woman with rest angina underwent cardiac catheterization; coronary angiography in the presence of acetylcholine revealed 99% coronary spasm of the proximal left anterior descending artery. The patient's 82-year-old mother was also admitted to hospital with rest angina. Her Holter electrocardiogram showed ST-segment elevation during the attack at rest and coronary angiography showed 99% spasm of the right coronary artery and 90% spasm of the left coronary artery. Both women complained of chest pain during the spasm, which was accompanied by ST-segment depression. The 62-year-old brother of the original patient was also found to have coronary spasm of the left coronary artery. Human leukocyte antigen was analyzed in the 2 women: A2, B51, CW1, DR8 and DQ1 were common factors. A Glu298Asp point mutation of the endothelial nitric oxide synthase gene was investigated in both parents, their 2 daughters and 2 sons, but was not detected in the 3 patients, and was detected only in the 90-year-old father who did not suffer from angina. Nor was the T-786-C mutation found in the 3 cases. Other causes of familial spasm need to be elucidated.  相似文献   
76.
We have previously reported that prostaglandin F(2alpha) (PGF(2alpha)) stimulates interleukin-6 (IL-6), a potent bone resorptive agent, through p44/p42 mitogen-activated protein (MAP) kinase in osteoblast-like MC3T3-E1 cells. In the present study, we investigated whether Rho-kinase is implicated in the PGF(2alpha)-stimulated IL-6 synthesis in MC3T3-E1 cells. PGF(2alpha) time-dependently induced the phosphorylation of myosin phosphatase targeting subunit (MYPT-1), a Rho-kinase substrate. Y27632, a specific Rho-kinase inhibitor, significantly reduced the PGF(2alpha)-stimulated IL-6 synthesis as well as the MYPT-1 phosphorylation. Fasudil, another inhibitor of Rho-kinase, suppressed the PGF(2alpha)-stimulated IL-6 synthesis. Y27632 and fasudil failed to affect the PGF(2alpha)-induced phosphorylation of p44/p42 MAP kinase. SB203580 and BIRB0796, potent inhibitors of p38 MAP kinase, suppressed the IL-6 synthesis induced by PGF(2alpha). While SP600125, an inhibitor of stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), failed to reduce the synthesis. Y27632 as well as fasudil attenuated the PGF(2alpha)-induced phosphorylation of p38 MAP kinase. These results strongly suggest that Rho-kinase regulates PGF(2alpha)-stimulated IL-6 synthesis via p38 MAP kinase activation in osteoblasts.  相似文献   
77.
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   
78.
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   
79.
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   
80.
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   
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