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   6188篇
  免费   503篇
  国内免费   139篇
耳鼻咽喉   86篇
儿科学   148篇
妇产科学   121篇
基础医学   845篇
口腔科学   196篇
临床医学   567篇
内科学   1124篇
皮肤病学   106篇
神经病学   392篇
特种医学   199篇
外国民族医学   1篇
外科学   816篇
综合类   349篇
现状与发展   1篇
一般理论   1篇
预防医学   419篇
眼科学   149篇
药学   492篇
  1篇
中国医学   86篇
肿瘤学   731篇
  2024年   11篇
  2023年   95篇
  2022年   260篇
  2021年   303篇
  2020年   192篇
  2019年   250篇
  2018年   260篇
  2017年   208篇
  2016年   222篇
  2015年   251篇
  2014年   306篇
  2013年   343篇
  2012年   443篇
  2011年   472篇
  2010年   255篇
  2009年   220篇
  2008年   313篇
  2007年   320篇
  2006年   295篇
  2005年   321篇
  2004年   243篇
  2003年   207篇
  2002年   188篇
  2001年   106篇
  2000年   95篇
  1999年   82篇
  1998年   46篇
  1997年   54篇
  1996年   39篇
  1995年   30篇
  1994年   29篇
  1993年   27篇
  1992年   48篇
  1991年   48篇
  1990年   30篇
  1989年   25篇
  1988年   30篇
  1987年   24篇
  1986年   22篇
  1985年   15篇
  1984年   8篇
  1982年   5篇
  1981年   5篇
  1979年   7篇
  1976年   4篇
  1974年   5篇
  1972年   8篇
  1970年   8篇
  1969年   8篇
  1939年   4篇
排序方式: 共有6830条查询结果,搜索用时 0 毫秒
1.
Mammalian fatty acid synthase (FASE) overexpression has been shown in a number of human malignancies including colonic adenocarcinoma. Since FASE synthesizes only saturated fatty acids, we hypothesized that cancer cells have a greater proportion of long-chain saturated fatty acids. We studied and found an unequivocal increase in saturated C18 fatty acid (stearic acid) in colonic adenocarcinoma compared to adjacent normal colonic mucosa. The increase is even more striking when measured as a ratio of stearic acid to the unsaturated C18 fatty acids (oleic acid and linoleic acid). This change in fatty acid composition of the cancer cells should significantly alter their physical and biological properties. The increase in relative proportion of saturated fatty acids should make the cancer cells more susceptible to cryodamage and measurement of fatty acid composition of cancer cells may help individualize the temperature for cryotherapy. Also, the lipid alterations may affect the structure and functions of lipid rafts, which may enable the cancer cells to affect signaling mechanisms such as those involved in cell growth and apoptosis. Dietary or therapeutic interventions targeting lipid rafts may thus be an option for cancer treatment.  相似文献   
2.
Xanthogranulomatous orchitis is an extremely rare inflammatory non-neoplastic destructive lesion of the testis. We report a 44-year-old man who presented with right scrotal swelling and two discharging sinuses. Testicular tumor markers were normal. Scrotal ultrasound showed heterogeneous testicular areas and irregular margin of the tunica. Surgical exploration revealed infected, unhealthy testicular tissue with necrosis and tumor-like lesion. Orchidectomy was done and histopathology showed xanthogranulomatous orchitis.  相似文献   
3.
Early catch-up growth and subsequent overweight are suggested to be associated with later cardiovascular diseases and later type II diabetes. However, the impact of early catch-up growth and childhood overweight on the development of asthma has been less studied, particularly in children born with very low birth weight (VLBW). A birth cohort of 74 VLBW children (birth weight < or = 1500 g) was followed from birth and investigated on asthma at 12 yr of age. Early rapid weight gain was in one way defined as an increase of weight > or =1 standard deviation score (SDS) at 6 months of corrected postnatal age. Current overweight was defined by body mass index (BMI) exceeding 21.2 and 21.7 kg/m(2), respectively, for boys and girls at 12 yr of age. Current asthma was diagnosed by a pediatrician, according to asthma ever in combination with a positive response to hypertonic saline bronchial provocation test and/or wheeze at physical examination at 12 yr old. Being overweight at 12 yr of age was associated with an increased risk for current asthma in the VLBW children [crude odds ratio (OR): 5.5, 95% confidence interval (CI): 1.3-22.2]. After adjustment for early weight gain and neonatal risk, the OR of overweight increased nearly three times (adjusted OR: 15.3, 95% CI: 2.5-90.6). Early rapid weight gain seemed to be inversely associated with current asthma (adjusted OR: 0.49 for an increase of weight equal to 1 SDS, 95% CI: 0.23-1.02, p = 0.06). In addition, early rapid weight gain was inversely associated with the magnitude of bronchial responsiveness at 12 yr (coefficient -1.15, p < 0.01). There was a strong and positive association between overweight and asthma at 12 yr of age in the VLBW children. This strong association had been reduced by early rapid weight gain, possibly via the reduction of bronchial responsiveness.  相似文献   
4.
Bacterial and fungal peritonitis is associated with a high riskof morbidity and mortality in patients undergoing continuousambulatory peritoneal dialysis (CAPD). Impaired cellular hostdefence in the peritoneal cavity underlies this risk. Two granulocyteinhibitory proteins with a molecular weight of 28000 dalton(GIP I) and about 9500 dalton (GIP II) with homology to light-chainproteins and beta respectively, were isolated from peritonealdialysis effluents. In vitro, both granulocyte inhibitory proteinsinhibit PMNL glucose uptake, phagocytosis and intracellularkilling of bacteria. The IC50 of GIP I or GIP II required forinhibition of half-maximal FMLP-induced or PMA-stimulated PMNLfunction was found to be in the nanomolar range, suggestingvery specific inhibition. These data may explain, at least inpart, defective local cellular host defence in CAPD patients.  相似文献   
5.
6.
目的 :探讨ATP敏感性K+ 通道 (KATP)开放剂吡那地尔 (pinacidil,Pin)对缺氧缺糖再复氧损伤大鼠大脑皮层神经细胞的保护作用。方法 :体外培养大鼠大脑皮层神经细胞 ,细胞培养至 10d ,建立神经细胞缺氧缺糖损伤模型 ,观察Pin及KATP阻断剂格列苯脲对缺氧缺糖不同时间 ,再复氧 2 4h后细胞死亡率、丙二醛 (MDA)含量、超氧化物歧化酶 (SOD)活力的影响。结果 :缺氧缺糖、再复氧后大鼠的神经细胞死亡率均显著升高、MDA生成增多、SOD的活力下降 ,Pin干预后 ,细胞死亡率下降、MDA生成减少、SOD的活力升高 ;格列苯脲能拮抗Pin这种保护作用。结论 :Pin对缺氧缺糖损伤神经细胞具有保护作用 ,并与拮抗氧自由基有关  相似文献   
7.
The Magnum system, initially designed for coronary angioplasty (PTCA) of chronic total occlusion, consists of a balloon catheter and a solid steel 0.021 inch (0.53 mm) steerable and removable wire with a soft and moldable distal portion, tipped with a 1 mm olive. To evaluate its performance in routine PTCA, 200 unselected consecutive patients were randomized to two equal groups, i.e., group Magnum (100 patients, 115 vessels) and group Standard (100 patients, 118 vessels) including 18 and 21 patients with chronic total occlusions, respectively. Randomization was performed by the sealed envelope system in the catheterization laboratory and crossover of system was imposed if it was not possible to place a balloon correctly within 20 min of fluoroscopy time. There were no significant differences between groups concerning clinical and angiographic baseline characteristics, size of initial balloons (3.0±0.3 mm in both groups), fluoroscopy time to cross the lesion with the wire (Magnum: 4±5, Standard: 5±6 min), total fluoroscopy time (Magnum: 11 ± 9, Standard: 12±12 min), and need for crossover (Magnum: 10%, Standard: 16%). Success rates per lesion were comparable with 90% in group Magnum and 84% in group Standard, as were the complications with one inhospital death in group Standard, occurring three weeks after PTCA and stent implantation. There was no emergency operation. Six patients per group had myocardial infarction of whom two in group Magnum and one in group Standard developed a Q-wave. The following variables were significantly in favor of the Magnum system compared with the Standard system: success rate in nontotal lesions (97% versus 90%) crossover success in total occlusions (0 vs. 33%), fluoroscopy time to cross the lesion with the balloon once the wire was in place (1 ± 2 vs. 2 ± 4 min), and use of a single versus 1.2±0.5 wires per lesion. The only advantage of the Standard systems was the more common use of 7 French guiding catheters (Magnum: 40%, Standard: 53%, p = 0.09). The Magnum system compares favorably with standard systems for routine PTCA. The robust design of the Magnum wire does not impair ease of placement and safety but saves material and facilitates balloon advancement across the lesion.  相似文献   
8.
BACKGROUND AND PURPOSE: Helical tomotherapy can eliminate the need for junction lines. The goal of this study is to evaluate tomotherapy in the delivery of CSA radiation and measurement of plan quality using physical parameters in comparing conventional (CSA-RT) and helical tomotherapy (CSA-TOMO) plans. PATIENTS AND METHODS: CSA-TOMO and CSA-RT plans were created for dosimetric comparison. Integral dose values were calculated. The ratios D50% (dose received by 50% of the organ at risk's volume) and D10% (dose received by 10% of the organ at risk's volume) were calculated representing large volumes and small volumes of organs at risk receiving significant dose. RESULTS: When considering D50% and D10%, CSA-TOMO has a dosimetric advantage over CSA-RT for most organs at risk. The body integral dose was higher for the CSA-TOMO plan by approximately 6.5%. CONCLUSIONS: Tomotherapy is a feasible alternative for treatment of CSA. Analysis shows that tomotherapy improves dose ratios over conventional radiation for most organs at risk. The impact of a small increase in whole body integral dose is unknown. Long-term follow-up will be needed to answer this question as others have argued of the possibility of increased risk of secondary malignancies due to delivery of radiotherapy with IMRT.  相似文献   
9.
Summary:  Purpose: Temporal lobe epilepsy (TLE) is probably more difficult to recognize in children than in adults. In fact, ictal symptoms in children are less stereotyped and less obvious, and the neuropathological substrate is more heterogeneous than in adults. The aim of this study is to examine the relationships between etiology, age at onset and electroclinical findings in 77 children with TLE, 32 of whom were surgically treated.
Methods: Electroclinical study including video-EEG recording of seizures in 77 children with TLE. The investigation focused on the first five initial ictal symptoms.
Results: Age at onset was less than 3 years in 39 cases, between 3 and 6 years in 17 cases and older than 6 years in 21 cases. Auras also occurred in younger children but were more common after the age of 6 years. A peculiar initial ictal semiology consisted in staring with arrest, lip cyanosis, and very slight oral automatisms. In some cases, EEG recordings documented seizures starting independently on both temporal lobes. Based on electroclinical and neuroradiological features, we recognized three subgroups: symptomatic TLE due to cortical malformations or nonevolutive tumors, TLE with mesial temporal sclerosis, and cryptogenic TLE.
Conclusions: A correct electroclinical and neuroradiological approach allows in several cases early recognition of TLE even when onset is earlier than the age of 6 years. A correct definition of the localization relies primarily on video-EEG recording of the seizures, possibly repeated during follow up in cases lacking obvious neuroradiological correlation.  相似文献   
10.
OBJECTIVE: The determination of the plasma aldosterone (PAC) to the plasma renin concentration (PRC) ratio is an accepted screening tool for primary hyperaldosteronism (PHyperA). DESIGN: To assess the diagnostic significance of this ratio for other disorders of the renin-aldosterone-system (RAS), we examined 60 patients with different adrenal diseases, 32 patients with essential hypertension and 76 normotensive healthy volunteers. The aldosterone (pmol/L) and renin (mU/L) concentrations were measured in one plasma sample by an automated chemiluminescence assay (Nichols Advantage). RESULTS: Patients with PHyperA (n=31) had a PAC/PRC ratio between 105 and 2328 and could be distinguished without overlap from the essential hypertension group (ratio: range 2.7-49) and normal healthy volunteers (ratio: range 0.9-71). Fourteen patients with primary hypoaldosteronism showed low PAC/PRC ratios (range 0.21-0.98) and low PAC values (range: 42-100). Seven patients with secondary hypoaldosteronism had normal PAC/PRC ratios (range 2.8-23.2) and low PAC values (range: 42-116). Eight patients with secondary hyperaldosteronism had normal PAC/PRC ratios (range 7.8-67.9) and elevated PAC values (range: 803-2917). The graphic presentation of these data allowed the differentiation of all major disorders of the RAS. CONCLUSIONS: The measurement of PAC/PRC ratios using this automated system provides a sensitive and rapid screening method for PHyperA. Moreover, the measurement of both the PAC and the PAC/PRC ratio allows differentiation of other disorders of the RAS.  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