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   3096篇
  免费   222篇
  国内免费   13篇
耳鼻咽喉   43篇
儿科学   40篇
妇产科学   76篇
基础医学   465篇
口腔科学   49篇
临床医学   291篇
内科学   606篇
皮肤病学   72篇
神经病学   173篇
特种医学   153篇
外科学   557篇
综合类   38篇
一般理论   2篇
预防医学   193篇
眼科学   86篇
药学   179篇
中国医学   2篇
肿瘤学   306篇
  2024年   7篇
  2023年   29篇
  2022年   46篇
  2021年   105篇
  2020年   76篇
  2019年   112篇
  2018年   115篇
  2017年   74篇
  2016年   70篇
  2015年   108篇
  2014年   124篇
  2013年   192篇
  2012年   246篇
  2011年   253篇
  2010年   181篇
  2009年   134篇
  2008年   194篇
  2007年   189篇
  2006年   188篇
  2005年   177篇
  2004年   181篇
  2003年   153篇
  2002年   121篇
  2001年   17篇
  2000年   26篇
  1999年   29篇
  1998年   23篇
  1997年   17篇
  1996年   12篇
  1995年   17篇
  1994年   13篇
  1993年   17篇
  1992年   5篇
  1991年   11篇
  1990年   3篇
  1989年   3篇
  1988年   3篇
  1987年   5篇
  1986年   3篇
  1985年   10篇
  1984年   10篇
  1983年   8篇
  1982年   2篇
  1981年   5篇
  1980年   4篇
  1978年   3篇
  1976年   2篇
  1970年   1篇
  1969年   1篇
  1964年   3篇
排序方式: 共有3331条查询结果,搜索用时 15 毫秒
11.
In an attempt to recognize early stages of focal segmental glomerulosclerosis (FSGS) in patients with a clinical course suggesting a diagnosis other than minimal change disease (MCD) and normal histology, or minor, nondiagnostic changes on light microscopy (LM), we used a protocol for systematic and extensive electron microscopy (EM) examination of kidney biopsies obtained from such patients. By this method ultrastructural pathology was found in 8 patients. These changes were localized, involving only portions of single glomerular segments. The findings included mild to moderate increase of the mesangial matrix, focal wrinkling of the capillary basement membrane, and early obliteration of the normal architecture of individual capillary loops, as well as electron-dense deposits in a mesangial and subendothelial distribution. Of these 8 patients, 2 are at present in remission without therapy (in 1, following therapy with cyclophosphamide); 3 are in remission on steroid therapy; 1 developed massive proteinuria during pregnancy, after a spontaneous remission lasting almost 2 years; 1 patient advanced to terminal renal failure 3 1/2 years after biopsy; and 1 died of sepsis 1 month after biopsy. We believe that the ultrastructural changes found may represent early or mild FSGS and that the protocol described can add valuable information in clinically worrisome patients in whom renal histology appears normal.  相似文献   
12.
According to the reformulated learned helplessness model of depression, causal attributions are an important mediator of the effects on mood of positive and negative experiences. Adaptive attributions for negative events are assumed to be external, unstable, and specific. In the present study, subjects exposed to one of two attribution training procedures or a control condition made attributions for hypothetical events under neutral and adaptive instructional sets. Attributions were rated by subjects and coders blind to the purpose of the study. Results indicated that subjects' views of adaptive causal attributions were congruent with predictions from the learned helplessness model. The ratings of the objective coders indicated that subjects' attributions really did change in response to the adaptive instructions in the predicted direction. Implications of these results for the reformulated learned helplessness model and depression therapies that include an attribution retraining component are discussed.The authors would like to thank Dan Russell for his very helpful comments on earlier drafts of this paper.  相似文献   
13.
The effect of suppository bases on rabbit rectal mucosa was investigated using six triglyceride bases, polyethylene glycol, and a triglyceride base combined with monoglycerides or fatty acids and methyl esters of those acids. Rectal irritation was evaluated and scored according to defined pathological features. Pure triglycerides and a triglyceride to which a nonionic surfactant was added caused severe mucosal damage with ulceration and inflammation. Hyperemia was characteristic for irritation by polyethylene glycol suppositories. Mucosal damage by a pure triglyceride combined with monoglycerides or fatty acids and methyl esters of those acids was similar but statistically less pronounced than with all other bases.  相似文献   
14.
PURPOSE: To select one of two chemoradiotherapy regimens for locally advanced squamous cell carcinoma (SCC) of the head and neck as the experimental arm for the next Trans-Tasman Radiation Oncology Group phase III trial. PATIENTS AND METHODS: One hundred twenty-two previously untreated patients with stage III/IV SCC of the head and neck were randomized to receive definitive radiotherapy (70 Gy in 7 weeks) concurrently with either cisplatin (75 mg/m(2)) plus tirapazamine (290 mg/m(2)/d) on day 2 of weeks 1, 4, and 7, and tirapazamine alone (160 mg/m(2)/d) on days 1, 3, and 5 of weeks 2 and 3 (TPZ/CIS), or cisplatin (50 mg/m(2)) on day 1 and infusional fluorouracil (360 mg/m(2)/d) on days 1 through 5 of weeks 6 and 7 (chemoboost). RESULTS: Three-year failure-free survival rates were 55% with TPZ/CIS (95% CI, 39% to 70%) and 44% with chemoboost (95% CI, 30% to 60%; log-rank P = .16). Three-year locoregional failure-free rates were 84% in the TPZ/CIS arm (95% CI, 71% to 92%) and 66% in the chemoboost arm (95% CI, 51% to 79%; P = .069). More febrile neutropenia and grade 3 or 4 late mucous membrane toxicity were observed with TPZ/CIS, while acute skin radiation reaction was more severe and prolonged with chemoboost. Compliance with protocol treatment was satisfactory on both arms. CONCLUSION: Both regimens are feasible and are associated with significant but acceptable toxicity profiles in the cooperative group setting. Based on the promising efficacy seen in this trial, TPZ/CIS is being evaluated in a large phase III trial.  相似文献   
15.
Oxycodone undergoes N-demethylation to noroxycodone and O-demethylation to oxymorphone. The cytochrome P450 (P450) isoforms capable of mediating the oxidation of oxycodone to oxymorphone and noroxycodone were identified using a panel of recombinant human P450s. CYP3A4 and CYP3A5 displayed the highest activity for oxycodone N-demethylation; intrinsic clearance for CYP3A5 was slightly higher than that for CYP3A4. CYP2D6 had the highest activity for O-demethylation. Multienzyme, Michaelis-Menten kinetics were observed for both oxidative reactions in microsomes prepared from five human livers. Inhibition with ketoconazole showed that CYP3A is the high affinity enzyme for oxycodone N-demethylation; ketoconazole inhibited >90% of noroxycodone formation at low substrate concentrations. CYP3A-mediated noroxycodone formation exhibited a mean K(m) of 600 +/- 119 microM and a V(max) that ranged from 716 to 14523 pmol/mg/min. Contribution from the low affinity enzyme(s) did not exceed 8% of total intrinsic clearance for N-demethylation. Quinidine inhibition showed that CYP2D6 is the high affinity enzyme for O-demethylation with a mean K(m) of 130 +/- 33 microM and a V(max) that ranged from 89 to 356 pmol/mg/min. Activity of the low affinity enzyme(s) accounted for 10 to 26% of total intrinsic clearance for O-demethylation. On average, the total intrinsic clearance for noroxycodone formation was 8 times greater than that for oxymorphone formation across the five liver microsomal preparations (10.5 microl/min/mg versus 1.5 microl/min/mg). Experiments with human intestinal mucosal microsomes indicated lower N-demethylation activity (20-50%) compared with liver microsomes and negligible O-demethylation activity, which predict a minimal contribution of intestinal mucosa in the first-pass oxidative metabolism of oxycodone.  相似文献   
16.
17.
IntroductionWe aimed to determine the minimum cross-sectional ellipsoid area on magnetic resonance (MR) of intraprostatic nodules that best predicts for subsequent targeted biopsies revealing ≥ grade group (GG) 2 disease.MethodsForty-six patients previously diagnosed with GG 1 prostate adenocarcinoma who received cognitively fused, MR-guided, transperineal targeted biopsies in addition to six random biopsies were included in this analysis. A Youden cutpoint analysis was used to determine the ellipsoid area in the axial plane best predicting for ≥GG 2 disease within the targeted biopsy cores and logistic regression used to assess the result.ResultsMedian time from MR imaging to targeted biopsy was 2.4 (1.4–5.5) months. Forty of 46 (87%) patients had one nodule and 6/46 (13%) had two separate nodules on MR that received targeted biopsy. Of the 52 nodules, five (10%), 33 (63%), and 14 (27%) were Prostate Imaging-Reporting and Data System (PI-RADS) 3, 4, and 5, respectively. Thirteen (25%), six (12%), and 33 (64%) were in the anterior, medial, and posterior regions of the prostate, respectively. Median area was 0.72 (0.49–1.29) cm2 (average diameter 9.5 mm). Fifteen of 46 (33%) patients had ≥1 random biopsy and 20/52 (38%) nodules had ≥1 targeted biopsy revealing ≥GG 2 disease. The optimal area cutpoint was ≥0.7 cm2, with an area under the curve of 0.671 (0.510–0.832). On logistic regression, area ≥0.7 cm2 was solely predictive of targeted biopsy revealing ≥GG 2 disease (odds ratio 6.5, 1.3–32.4, p=0.022).ConclusionsNodule area ≥0.7 cm2 may predict for transperineal-based targeted biopsies being positive for ≥GG 2 disease when 1–2 cores are taken.  相似文献   
18.
Preface     
  相似文献   
19.
Considerable gender disparity exists in the incidence of HIV/AIDS in men, with men experiencing the largest burden of this epidemic. In addition, over six million men in the United States experience depressive disorders. HIV-infected men experience the three most common depressive disorders—major depression, dysthymia, and bipolar disorder. Comorbidity associated with the dual diagnosis of HIV infection and common depressive disorders in men is a critical men's health issue. This article's purpose is to increase health care professionals' awareness and knowledge regarding the significant impact of a dual diagnosis of HIV infection and depression on men's health.  相似文献   
20.
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