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   685篇
  免费   29篇
  国内免费   2篇
耳鼻咽喉   31篇
儿科学   46篇
妇产科学   5篇
基础医学   55篇
口腔科学   18篇
临床医学   39篇
内科学   175篇
皮肤病学   13篇
神经病学   23篇
特种医学   33篇
外科学   132篇
综合类   4篇
预防医学   16篇
眼科学   10篇
药学   61篇
中国医学   1篇
肿瘤学   54篇
  2023年   1篇
  2022年   4篇
  2021年   13篇
  2020年   12篇
  2019年   16篇
  2018年   19篇
  2017年   8篇
  2016年   10篇
  2015年   14篇
  2014年   21篇
  2013年   20篇
  2012年   47篇
  2011年   35篇
  2010年   21篇
  2009年   23篇
  2008年   52篇
  2007年   43篇
  2006年   43篇
  2005年   50篇
  2004年   42篇
  2003年   43篇
  2002年   53篇
  2001年   3篇
  2000年   10篇
  1999年   8篇
  1998年   11篇
  1997年   11篇
  1996年   9篇
  1995年   6篇
  1994年   6篇
  1993年   10篇
  1992年   11篇
  1991年   7篇
  1990年   7篇
  1989年   10篇
  1988年   3篇
  1987年   2篇
  1985年   2篇
  1984年   1篇
  1983年   3篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1963年   1篇
排序方式: 共有716条查询结果,搜索用时 15 毫秒
41.
We report herein the presence of a 56 kd platelet derived growth factor (PDGF)-related protein as a phosphorylated form in human glioma cells. The phosphorylation of the 56 kd form was found to be the longest of all PDGF-related proteins. By Western blotting using a monoclonal anti-PDGF B-chain, the 80 kd, 56 kd, 40 kd, 28 kd and 17 kd PDGF-related proteins were detected, while after treatment among the nitrocellulose membrane transblotted cell extracts with alkaline phosphatase, 40 kd was the most densely observed while the 56 kd and 80 kd PDGF-related proteins were also detected. In a 32P flush labeling study, it was revealed that PDGF-related proteins incorporated with 32P were detected at 28, 32, 35, 40, 56 and 80 kd but the 17 kd monomer was not labeled. Among the labeled PDGF-related proteins, the 56 kd PDGF-related protein alone remained intracellularly for at least 16 hours. These results indicated that the PDGF-related proteins in human glioma cells are synthesized in a phosphorylated form and partly remain in a 56 kd phosphorylated form intracellularly. The 56 kd form may thus be the most stable form and likely has a substantial biological effect.  相似文献   
42.
Synthetic or natural food dyes are typical xenobiotics, as are drugs and pollutants. After ingestion, part of these dyes may be absorbed and metabolized by phase I and II drug-metabolizing enzymes and excreted by transporters of phase III enzymes. However, there is little information regarding the metabolism of these dyes. It was investigated whether these dyes are substrates for CYP2A6 and UDP-glucuronosyltransferase (UGT). The in vitro inhibition of drug-metabolizing enzymes by these dyes was also examined. The synthetic food dyes studied were amaranth (food red no. 2), erythrosine B (food red no. 3), allura red (food red no. 40), new coccine (food red no. 102), acid red (food red no. 106), tartrazine (food Yellow no. 4), sunset yellow FCF (food yellow no. 5), brilliant blue FCF (food blue no. 1), and indigo carmine (food blue no. 2). The natural additive dyes studied were extracts from purple sweet potato, purple corn, cochineal, monascus, grape skin, elderberry, red beet, gardenia, and curthamus. Data confirmed that these dyes were not substrates for CYP2A6, UGT1A6, and UGT2B7. Only indigo carmine inhibited CYP2A6 in a noncompetitive manner, while erythrosine B inhibited UGT1A6 (glucuronidation of p-nitrophenol) and UGT2B7 (glucuronidation of androsterone). In the natural additive dyes just listed, only monascus inhibited UGT1A6 and UGT2B7.  相似文献   
43.
Numerous cellular and molecular perturbations have been studied to elucidate the pathogenic mechanisms underlying nephrotic-range proteinuria, which may in turn shed light on disease-specific mechanisms. We have analyzed the publicly available data from the PhysGen partial panel of consomic rats to determine whether there are quantitative trait loci that associate with nephrotic-range proteinuria. As of this writing, consomic rat strains subjected to the renal protocol have been bred by the Program for Genomic Applications for 15 of the 22 rat chromosomes for both genders, predominantly with the Brown–Norway (BN) and Dahl salt-sensitive (SS) strains as parents. We defined chromosomes of interest as consomic SS-xBN strains whose phenotype measurements differed significantly from SS but not BN strains, stratified by gender. We filtered and clustered differentially expressed genes by function in renal tissue from relevant strains. Proteinuria was significantly higher in male SS vs. male SS-18BN, and it was significantly higher in male SS vs. female SS. Functional clustering of differentially expressed genes yielded two specific functional clusters: apoptosis (p=0.022) and angiogenesis (p=0.046). Gene expression profiles demonstrated differential expression of apoptotic and angiogenic genes. However, TUNEL stains of renal tissue showed no significant difference in the number of apoptotic nuclei. We conclude that chromosomes 18 and X are quantitative trait loci for nephrotic-range proteinuria in rats.  相似文献   
44.
Novel magnetic resonance angiography stage grading for moyamoya disease   总被引:1,自引:0,他引:1  
BACKGROUND: Magnetic resonance angiography (MRA) has been acknowledged as a noninvasive diagnostic modality for moyamoya disease. However, in terms of staging of moyamoya disease, conventional angiography is still the gold standard. Therefore, the purpose of this study was to establish MRA grades for moyamoya disease as an alternative to conventional angiography. METHODS: Twenty-two patients (44 sides) with moyamoya disease diagnosed by conventional angiography were evaluated by MRA during the past 5 years. MRA scores were assigned based on the severity of occlusive changes of the internal carotid artery, the horizontal portion of the middle cerebral artery, the anterior and the posterior cerebral arteries and the signals of the distal branches of these arteries. Total points ranged from 0 (normal) to 10 (most severe). RESULTS: MRA scores (0-10) were significantly consistent with the conventional angiographic staging. Four grades based on this novel MRA scores correlated well with Suzuki's stages, with high sensitivity and specificity. CONCLUSIONS: These novel MRA grades can be a reliable alternative to conventional staging. By employing these novel MRA grades, the use of conventional angiography can be avoided for the purpose of evaluation of the stages of moyamoya disease.  相似文献   
45.
The purpose of this study was to build a visualization technique of the femorotibial contact in fixed-bearing total knee arthroplasty (TKA) using X-ray fluoroscopy, and to apply this technique to a TKA patient during dynamic motion. In vivo kinametcis of the metallic knee implant was determined using a 2D/3D registration technique, which uses computer assisted design (CAD) model of the implant to estimate the 3D pose of radiopaque metallic femoral and tibial components from a single-plane fluoroscopic image. In fixed-bearing TKA, a 3D pose of radiolucent tibial polyethylene insert can be determined from the estimated pose of the tibial component. To visualize femorotibial contact, the proximity between surfaces of femoral component and tibial insert was calculated, and mapped onto the insert surface model. For the clinical application, dynamic states of contact on the tibial insert were observed including axial rotation and unilateral loading during knee flexion, and post-cam contact of posterior stabilized TKA. The present technique provided us new information and enabled us to better understand the relationship between in vivo knee kinematics and articular shape of the implant.  相似文献   
46.

Purpose

Abnormalities in esophageal motor function underlie various symptoms in the pediatric population. Manometry remains an important tool for studying esophageal motor function, whereas its analyses have been conducted with considerable subjective interpretation. The usefulness of videomanometry with topographic analysis was examined in the current study.

Methods

Videomanometry was conducted in 5 patients with primary gastroesophageal reflux disease (GERD), 4 with postoperative esophageal atresia (EA), 1 with congenital esophageal stenosis (CES), and 1 with diffuse esophageal spasms (DES). Digitized videofluoroscopic images were recorded synchronously with manometric digital data in a personal computer. Manometric analysis was conducted with a view of concurrent esophageal contour and bolus transit.

Results

Primary GERD patients showed esophageal flow proceeding into the stomach during peristaltic contractions recorded manometrically, whereas patients with EA/CES frequently showed impaired esophageal transit during defective esophageal peristaltic contractions. A characteristic corkscrew appearance and esophageal flow in a to-and-fro fashion were seen with high-amplitude synchronous esophageal contractions in a DES patient. The topographic analysis showed distinctive images characteristic of each pathological condition.

Conclusions

Videomanometry is helpful in interpreting manometric data by analyzing concurrent fluoroscopic images. Topographic analyses provide characteristic images reflecting motor abnormalities in pediatric esophageal disease.  相似文献   
47.

Purpose

Children with neurologic and neuromuscular handicaps frequently have various symptoms related to gastroesophageal reflux (GER) disease. The long-term efficacy of antireflux surgery remains controversial in such children with GER. The clinical results of such patients who underwent laparoscopic fundoplication were examined in the current study.

Methods

Between 1997 and 2003, laparoscopic fundoplication was performed in 56 handicapped children (mean age, 6 years), and gastrostomy was performed concurrently in 52. The main symptoms were emesis/hematemesis in 40 and respiratory symptoms, including repeated respiratory infection and distress, in 31.

Results

There were no severe postoperative complications or operative mortality. Emesis/hematemesis was controlled adequately in those without recurrence. Respiratory symptoms were controlled unsuccessfully in 16 patients (52%), 8 of whom required further respiratory care including nasal airway tube, tracheostomy, and laryngotracheal separation. Recurrence of GER disease occurred in 10 patients, 7 of whom underwent a second Nissen fundoplication successfully. Thirteen died within the median follow-up period of 14 months.

Conclusions

Laparoscopic fundoplication is effective in controlling emesis/hematemesis, but its efficacy is limited in terms of respiratory problems in handicapped children. Further refinements in diagnostic and treatment strategies are mandatory to improve the quality of life in such patients.  相似文献   
48.
Amlodipine, a dihydropyridine Ca(2+) channel blocker, is reported to inhibit proliferation of human epidermoid carcinoma A431 cells, and specifically attenuates Ca(2+) responses evoked by thapsigargin, an inhibitor of endoplasmic reticulum Ca(2+)-ATPases. In this study, we further examined the possible mechanism of the antiproliferative action of amlodipine and its antitumor effect on A431 xenografts in nude mice. Amlodipine reduced BrdU incorporation into nucleic acids in serum-starved A431 cells, and the reduction was diminished by uridine 5'-triphosphate (UTP), a phospholipase C (PLC)-linked agonist. Fluorometric measurement of intracellular free Ca(2+) concentration revealed that amlodipine blunted the UTP-induced Ca(2+) release from the internal Ca(2+) stores and consequently Ca(2+) influx through Ca(2+)-permeable channels on the plasma membrane. Although amlodipine alone caused Ca(2+) release from thapsigargin-sensitive Ca(2+) stores, such an effect was not reproduced by other dihydropyridine Ca(2+) channel blockers, including nicardipine and nimodipine, despite their antiproliferative effects in the cells. Daily intraperitoneal administration of amlodipine (10 mg/kg) for 20 days into mice bearing A431 xenografts retarded tumor growth and prolonged the survival of mice. Our results suggest a potential antitumor action for amlodipine in vitro and in vivo, which may be in part mediated by inhibiting Ca(2+) influx evoked by the passive depletion of internal Ca(2+) stores and by PLC-linked agonist stimulation.  相似文献   
49.
A 35-year-old man was admitted because of significant hepatic dysfunction with mild splenomegaly and intra-abdominal lymphadenopathy of unknown cause. Infectious mononucleosis was suggested by subsequently detected high fever, pharyngotonsillitis and cervical lymphadenopathy, but IgM to Epstein-Barr virus (EBV) and cytomegalovirus (CMV) showed dual positivity. A definite diagnosis of EBV-induced infectious mononucleosis was established 3 months later on the basis of seroconversion to Epstein-Barr nuclear antigen (EBNA)-IgG positivity and reduced CMV-IgM titer with persistently negative CMV-IgG. This case highlights the initial diagnostic difficulties of EBV-induced infectious mononucleosis particularly in older patients, due to concomitant abnormal humoral immunity and unusual initial manifestations such as significant liver injury and extensive intra-abdominal lymphadenopathy.  相似文献   
50.
The catalase activities in blood and organs of the acatalasemic (C3H/AnLCs(b)Cs(b)) mouse of C3H strain are lower than those of the normal (C3H/AnLCs (a)Cs(a)) mouse. We examined the effects of prior low-dose (0.5 Gy) X-ray irradiation, which reduced the oxidative damage under carbon tetrachloride-induced hepatopathy in the acatalasemic or normal mice. The acatalasemic mice showed a significantly lower catalase activity and a significantly higher glutathione peroxidase activity compared with those in the normal mice. Moreover, low-dose irradiation increased the catalase activity in the acatalasemic mouse liver to a level similar to that of the normal mouse liver. Pathological examinations and analyses of blood glutamic oxaloacetic and glutamic pyruvic transaminase activity and lipid peroxide levels showed that carbon tetrachloride induced hepatopathy was inhibited by low-dose irradiation. These findings may indicate that the free radical reaction induced by the lack of catalase and the administration of carbon tetrachloride is more properly neutralized by high glutathione peroxidase activity and low-dose irradiation in the acatalasemic mouse liver.  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