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   43707篇
  免费   2210篇
  国内免费   74篇
耳鼻咽喉   630篇
儿科学   1742篇
妇产科学   731篇
基础医学   5817篇
口腔科学   1000篇
临床医学   2752篇
内科学   10861篇
皮肤病学   1539篇
神经病学   3581篇
特种医学   1050篇
外科学   6028篇
综合类   286篇
一般理论   18篇
预防医学   3829篇
眼科学   1194篇
药学   2534篇
中国医学   200篇
肿瘤学   2199篇
  2024年   40篇
  2023年   297篇
  2022年   308篇
  2021年   1197篇
  2020年   548篇
  2019年   1252篇
  2018年   1944篇
  2017年   1121篇
  2016年   947篇
  2015年   836篇
  2014年   1044篇
  2013年   1796篇
  2012年   3180篇
  2011年   3527篇
  2010年   1733篇
  2009年   1055篇
  2008年   2747篇
  2007年   2816篇
  2006年   2595篇
  2005年   2677篇
  2004年   2476篇
  2003年   2407篇
  2002年   2174篇
  2001年   1567篇
  2000年   2003篇
  1999年   1120篇
  1998年   295篇
  1997年   171篇
  1996年   176篇
  1995年   161篇
  1994年   131篇
  1993年   116篇
  1992年   167篇
  1991年   152篇
  1990年   122篇
  1989年   119篇
  1988年   103篇
  1987年   100篇
  1986年   96篇
  1985年   81篇
  1984年   77篇
  1983年   59篇
  1982年   43篇
  1981年   30篇
  1980年   33篇
  1979年   31篇
  1978年   32篇
  1977年   33篇
  1975年   28篇
  1974年   25篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Adult respiratory distress syndrome (ARDS) complicating the course of fulminant hepatic failure is nearly always fatal without orthotopic liver transplantation. We report the case of a 50-year-old woman with fulminant hepatic failure and ARDS that resolved after her recovery from the acute liver failure without liver transplantation. The pathogenesis is discussed, particularly with regard to liver-lung interactions.  相似文献   
992.
AIM: To analyze the relationship between perisinusoidal stellate cell (PSC) activation and the dietary fat quantity and composition in the treatment of hepatic steatosis. METHODS: Using an experimental rat model of steatosis based on the intake of a hyperlipidic diet (14% fat as olive oil or sunflower oil, HL-O and HL-S, respectively), we analyzed the liver's capability of recovery after the treatment with a normal-lipidic diet (5% fat as olive oil or sunflower oil, NL-O and NL-S, respectively) by immu-nocytochemical and Western blot analysis of glial fibril-lary acidic protein (GFAP) expression in PSCs, collagen quantification and serum aminotransferase determination. RESULTS: The fatty infiltration in the steatotic livers decreased after the treatment with both NL diets, indicating liver recovery. This decrease was accompanied with a lower collagen deposition and aminotransferase level as well as changes in the PSC population that increased the GFAP expression. The above-mentioned effects were more pronounced in animals fed on NL-O based diet. CONCLUSION: Treatment with a balanced diet enriched in olive oil contributes to the liver recovery from a steatotic process. The PSC phenotype is a marker of this hepatic-recovery model.  相似文献   
993.
994.
Summary The aim of this study was to determine the value of von Willebrand factor (vWF), a well-characterized endothelial cell protein secretion, as a marker for prognosis in patients with primary pulmonary hypertension (PPH). Venous and arterial blood samples were obtained from 18 clinically diagnosed PPH patients and 12 case controls matched for age and sex. Plasma vWF antigen was determined by enzymelinked immunosorbent assay (ELISA). The patients' multimeric vWF pattern was analyzed by sodium dodecylsulfate (SDS)-agarose-acrylamide electrophoresis, Western blot, and densitometric analysis. vWF sialic acid content was determined by a lectin-based ELISA. The PPH patients showed a higher content of vWF antigen in venous (P = 0.0026) and arterial (P = 0.0094) blood samples than controls. The mean vWF sialic acid content of the PPH patients corresponded to 37.7% of the mean value for the control group. On the basis of the hemodynamic response to vasodilator trial, the PPH patients were grouped as responders or nonresponders. The latter group showed a significantly higher plasma vWF antigen antecubital vein/radial artery ratio, an increased number of unusually large vWF multimers, and a diminished content of vWF sialic acid in comparison with the first group. We believe that our results establish the nature of vWF alterations that are related to endothelial cell damage in patients with primary pulmonary hypertension and that this could be of value when establishing the prognosis in this group of patients.  相似文献   
995.
The most important factor in the management of alimentary tract bleeding is the adequate localization of the lesion. Small bowel bleeding is a rare entity and determination of the specific anatomic site is difficult. Once stomach, duodenum, or colon origin has been discharged through endoscopy, methods such as angiography and Tc99m RBC scans are appropriate. We present a patient with lower gastrointestinal bleeding secondary to jejunal angiodysplasia associated with jejunal diverticular disease. In the present case, Tc99m RBC scans were used to identify the bleeding site. In cases of lower gastrointestinal bleeding of undetermined origin, we suggest the consideration of both diagnoses (angiodysplasia or diverticular disease) with exploratory celiotomy to resolve these pathologies, particularly in the elderly patient.  相似文献   
996.
OBJECTIVES: LDL-cholesterol particles from hypertensive patients exhibit enhanced susceptibility to in vitro oxidation, an abnormality thought to increase cardiovascular risk. We tested whether blood pressure (BP) normalization can reverse this abnormality. DESIGN: Double-blind, randomized pharmacological intervention trial. SETTING: Clinical research centre. Subjects. A total of 29 nondiabetic, normolipidaemic patients with essential hypertension (BP= 151 +/- 3/99 +/- 1 mmHg) and 11 normotensive controls (BP=125 +/- 3/85 +/- 1 mmHg) matched for gender, age, obesity, glucose tolerance and lipid profile. Intervention. Anti-hypertensive treatment for 3 months with a calcium-antagonist in randomized combination with either an ACE inhibitor or a beta-blocker. MAIN OUTCOME MEASURES: Lag phase of copper-induced LDL oxidation, cell-mediated (human umbilical vein endothelium) generation of malondialdehyde (MDA) by LDL and vitamin E content in LDL. RESULTS: At baseline in hypertensives versus controls, lag phase was shorter (89 +/- 3 vs. 107 +/- 6 min, P < 0.04), MDA generation was higher (5.8 +/- 0.1 vs. 5.1 +/- 0.2 nmol L(-1), P=0.002), and vitamin E was reduced (6.40 +/- 0.05 vs. 6.67 +/- 0.11 microg mg(-1), P=0.03). At 3 months, BP was normalized (124 +/- 3/81 +/- 1, P < 0.0001 vs. baseline, P=ns versus controls), lag phase was prolonged (to 98 +/- 3 min, P=0.0005), MDA generation was reduced (5.6 +/- 0.1 nmol L-1, P = 0.001), and vitamin E was increased (6.53 +/- 0.05 microg mg(-1), P=0.003), with no significant differences between the randomized groups. CONCLUSIONS: In nondiabetic, nonobese, normolipidaemic patients with essential hypertension, LDL susceptibility to copper- and cell-mediated oxidation is increased. BP normalization is associated with a significant improvement, but not a full reversal, of this abnormality.  相似文献   
997.
A higher specific binding of GLP-1(7–36)amide is found in skeletal muscle plasma membranes from adult streptozotocin (STZ)-treated rats (insulin-dependent diabetes mellitus model) and from neonatal STZ-treated rats (non insulin-dependent diabetes mellitus model), as compared to that in normal controls; no apparent change in the affinity was observed, that indicating the presence in both diabetic models of an increased number of high affinity binding sites for the peptide. The maximal specific GLP-1(7–16)amide binding in the non insulin-dependent diabetes mellitus model was found to be significantly higher than that in the insulin-dependent diabetes mellitus model. As GLP-1(7–36)amide exerts a glycogenic effect in the rat skeletal muscle, the present data suggest that the action of the peptide in the muscle glucose metabolism may be increased in states of insulin deficiency accompanied or not by insulin resistance.  相似文献   
998.
OBJECTIVE: To explore the possible association/s of the first reported tumour necrosis factor (TNF-alphaTNF-) alpha promoter gene polymorphisms -308, -238, -376 and -163 (G-->A) with systemic (SoJIA) and oligoarticular subtypes of juvenile idiopathic arthritis (JIA); and to test the association between these polymorphisms and the class I/class II HLA alleles in our population. METHODS: The patient group comprised 29 oligoarticular and 26 systemic Caucasian Spanish children with JIA; 68 healthy volunteers from the same ethnic group and geographical region served as controls. HLA alleles were determined using low-resolution polymerase chain reaction (PCR). TNF-alpha promoter gene polymorphisms were screened using PCR denaturing gradient gel electrophoresis (PCR-DGGE), followed, if positive, by restriction fragment length polymorphism (RFLP) analysis for identification. RESULTS: No statistical association was found between the four polymorphisms studied and JIA. However, the -308 G-->A polymorphism (TNF A2) tended to be more frequent in patients with SoJIA than in the oligoarticular group. TNF A2 was strongly associated with the extended haplotype A1B8DR3 (p = 0.003), and the tandem polymorphism -238/-376 in the presence of B18 and DR3. CONCLUSION: The TNF A2 allele was more frequent in SoJIA than in the oligoarticular group. TNF A2 can help to create a more inflammatory milieu in this JIA subtype, in combination with other polymorphisms involved in regulatory sequences of key molecules in the inflammatory response. The association of the -308 and -238/-376 polymorphisms with specific alleles of the HLA is reconfirmed.  相似文献   
999.
BACKGROUND: Genetic factors are thought to be crucial in the pathogenesis of ankylosing spondylitis. Transforming growth factor beta 1 (TGF beta 1) is a multifunctional cytokine that plays a key role in inflammation. Two functional single nucleotide polymorphisms (SNPs) in the TGFB1 gene have been described: TGFB1 T869C and TGFB1 G915C. OBJECTIVE: To determine whether these SNPs contribute to ankylosing spondylitis susceptibility or its disease characteristics. METHODS: Genomic DNA was isolated from the peripheral blood of 134 patients with ankylosing spondylitis and 194 healthy blood donors. All subjects were unrelated and of white Dutch ethnicity. The diagnosis of ankylosing spondylitis was made according to the modified New York criteria. The TGFB1 T869C and TGFB1 G915C SNPs were genotyped by a polymerase chain reaction-single strand conformation polymorphism haplotyping method. RESULTS: No significant differences were found between patients and controls in genotype, allele, and haplotype frequencies or in the carrier rate of the rare alleles of the TGFB1 T869C and TGFB1 G915C SNPs. CONCLUSIONS: TGFB1 T869C and TGFB1 G915C SNPs are not major factors in the susceptibility to ankylosing spondylitis or its disease characteristics.  相似文献   
1000.
The safety and efficacy of early bacterial prophylaxis with piperacillin-tazobactam were prospectively evaluated in 51 autologous peripheral blood stem cell transplantation (PBSCT) recipients. The results were compared with those obtained in 51 control patients receiving oral fluoroquinolones in a retrospective matched-pair control study. Overall, 76% of the study group and 98% of the control group developed at least one febrile episode during neutropenia (P=0.002). Time from neutropenia to the first febrile episode (FFE) was significantly longer in the study group than in the control group (P=0.04). Once a febrile episode appeared, the duration of fever was significantly longer in cases than in controls (median of 5 and 2 days respectively, P<0.001), and led to a more frequent use of empirical amphotericin B (AmB), not statistically significant (P=0.13). However, the total time of antibiotic administration was significantly greater in the control than in the study group (P=0.05). The duration of AmB treatment shows a trend toward a longer duration in the control than in study group (P=0.2). Overall, 86% of the Gram-positive bacteremia and 85% of the Gram-negative bacteria were susceptible to the tested antibiotics. Our study suggests that a subgroup of patients could benefit from prophylaxis with piperacillin-tazobactam without increasing toxicity or bacterial resistance.  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