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   5706篇
  免费   485篇
  国内免费   9篇
耳鼻咽喉   45篇
儿科学   125篇
妇产科学   216篇
基础医学   848篇
口腔科学   95篇
临床医学   551篇
内科学   1285篇
皮肤病学   154篇
神经病学   413篇
特种医学   266篇
外国民族医学   5篇
外科学   795篇
综合类   61篇
一般理论   6篇
预防医学   505篇
眼科学   52篇
药学   330篇
中国医学   11篇
肿瘤学   437篇
  2022年   39篇
  2021年   81篇
  2020年   41篇
  2019年   71篇
  2018年   82篇
  2017年   68篇
  2016年   73篇
  2015年   76篇
  2014年   117篇
  2013年   163篇
  2012年   255篇
  2011年   283篇
  2010年   154篇
  2009年   140篇
  2008年   267篇
  2007年   270篇
  2006年   224篇
  2005年   243篇
  2004年   247篇
  2003年   239篇
  2002年   213篇
  2001年   216篇
  2000年   224篇
  1999年   162篇
  1998年   103篇
  1997年   85篇
  1996年   67篇
  1995年   52篇
  1994年   64篇
  1993年   49篇
  1992年   143篇
  1991年   110篇
  1990年   120篇
  1989年   116篇
  1988年   115篇
  1987年   120篇
  1986年   88篇
  1985年   94篇
  1984年   79篇
  1983年   65篇
  1981年   40篇
  1979年   59篇
  1978年   45篇
  1974年   50篇
  1973年   50篇
  1972年   42篇
  1971年   47篇
  1969年   38篇
  1968年   35篇
  1967年   45篇
排序方式: 共有6200条查询结果,搜索用时 0 毫秒
81.
Biological parameters known to be affected in lead poisoning were measured in rats following ingestion of graded dosages of lead. Intranuclear inclusion bodies are formed in renal tubular lining cells with smaller doses of lead than produce other changes. Decreased body weight is the next most sensitive abnormality. This is followed by increased delta-aminolevulinic acid (ALA) excretion, reticulocytosis, renal edema, and aminoaciduria. Anemia only occurs at the highest lead dosage. Over a wide range of lead ingestion, urinary lead excretion remains constant, although renal lead content increases. Quantitative lead analyses of cell organelles show that lead is concentrated within the inclusion bodies. Relatively small amounts of lead are present in the cytoplasm and mitochondria. It is suggested that soft-tissue lead accumulates in the intranuclear inclusion body, thereby sparing toxic injury to cytoplasmic organelles.  相似文献   
82.
Hyperglycemia and compromised β-cell development were demonstrated in neonatal rats programmed with a gestational high-fat diet. The aim of this study was to determine whether these changes were attributed to impaired insulin release and altered immunoreactivity of Pdx-1, glucokinase (GK), and glucose transporter (GLUT)–2 in high-fat–programmed neonates. Fetuses were maintained, via maternal nutrition, on either a standard laboratory diet (control) or a high-fat diet throughout gestation (HFG). Pancreata from 1-day–old neonates were excised for islet isolation and the subsequent measurement of insulin release at 2.8, 6.5, 13, and 22 mmol/L glucose. Other pancreata were either snap frozen for quantitative polymerase chain reaction or formalin fixed for immunohistochemistry followed by image analysis. The HFG neonates had reduced insulin release at 13- and 22-mmol/L glucose concentrations. No significant differences were found in Pdx-1, GK, or GLUT-2 messenger RNA expression. In HFG neonates, immunoreactivity of both Pdx-1 and GK was significantly reduced, with a nonsignificant reduction in GLUT-2. Gestational high-fat programming impairs insulin release and reduces Pdx-1 and GK immunoreactivity.  相似文献   
83.
84.
85.
Bovine testicular hyaluronidase (BTH) reduces experimental myocardial infarct size and ameliorates electrocardiographic signs of ischemia. This study was done to determine if heparin, an in vitro inhibitor of hyaluronidase activity, blocks the action of BTH in the myocardium of dogs after coronary artery occlusion. BTH was administered intravenously as 5,000 NF units/kg at 0.5 and 2.5 hours after coronary occlusion. Heparin was administered intravenously as a 150-unit/kg loading dose, followed by 10 units/kg per hour i.v., beginning 15 minutes before coronary occlusion. The area of myocardial ischemia at risk was assessed by a radiolabeled microsphere technique; the area that developed necrosis was assessed by a histochemical technique. In vivo activity of BTH was assessed by a colorimetric analysis of the BTH substrate, i.e., hyaluronic acid (HA), extracted from myocardial tissue. For biochemical analysis of HA, the heart was divided into anterior myocardium, which included ischemic tissue and posterior nonischemic myocardium. The myocardial HA content of dogs treated with BTH plus heparin (anterior, 3.44 +/- 0.40 micrograms HA/mg protein; posterior, 3.69 +/- 0.33 micrograms HA/mg protein) was not significantly different from control (anterior, 3.61 +/- 0.29 micrograms HA/mg protein; posterior, 3.55 +/- 0.23 micrograms HA/mg protein). In contrast, BTH lowered myocardial HA content (anterior, 2.16 +/- 0.21 micrograms HA/mg protein; posterior, 2.08 +/- 0.14 micrograms HA/mg protein) compared with either BTH plus heparin or control groups in both anterior myocardium (p = 0.006) and posterior myocardium (p = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
86.
87.
88.
In this study we investigated in the rat the binding and corticotropin-releasing factor (CRF) activity of various constituents of the renin-angiotensin system and the possible angiotensin II receptor changes following procedures known to alter plasma renin activity. We investigated also the CRF activity of angiotensin II in vitro and in vivo in humans. The CRF activity of peptides was studied by their ability to stimulate ACTH release from pituitary cells. Deleting amino acids from the N-terminus of angiotensin II resulted in decreased CRF activity; while the ED50 for angiotensin II was 2 nM, it increased to about 10 nM for the (2-8)-heptapeptide. Angiotensin I had a weak CRF activity, whereas the substrate angiotensinogen had no stimulatory effect even at a concentration of 100 nM. There was a strong correlation between the activation and binding properties of all peptides tested. Dietary salt load or depletion as well as dexamethasone treatment did not affect the number nor the affinity of pituitary angiotensin II receptors. Angiotensin II had a CRF activity on human pituitary cells in vitro. However, peripherally injected agiotensin II at a pressive dose of 7 ng/kg/min did not produce any ACTH release in normal male volunteers. These data suggest that angiotensin II may play a modulatory role in the physiological regulation of ACTH secretion, but this role might be attributed to the endogenous brain angiotensin II as it is not closely dependent on the angiotensin II plasma levels.  相似文献   
89.
90.
Alström Syndrome (ALMS), a recessive, monogenic ciliopathy caused by mutations in ALMS1, is typically characterized by multisystem involvement including early cone‐rod retinal dystrophy and blindness, hearing loss, childhood obesity, type 2 diabetes mellitus, cardiomyopathy, fibrosis, and multiple organ failure. The precise function of ALMS1 remains elusive, but roles in endosomal and ciliary transport and cell cycle regulation have been shown. The aim of our study was to further define the spectrum of ALMS1 mutations in patients with clinical features of ALMS. Mutational analysis in a world‐wide cohort of 204 families identified 109 novel mutations, extending the number of known ALMS1 mutations to 239 and highlighting the allelic heterogeneity of this disorder. This study represents the most comprehensive mutation analysis in patients with ALMS, identifying the largest number of novel mutations in a single study worldwide. Here, we also provide an overview of all ALMS1 mutations identified to date.  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