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   51992篇
  免费   3488篇
  国内免费   215篇
耳鼻咽喉   770篇
儿科学   1254篇
妇产科学   709篇
基础医学   6713篇
口腔科学   938篇
临床医学   5119篇
内科学   11050篇
皮肤病学   413篇
神经病学   5637篇
特种医学   2045篇
外国民族医学   1篇
外科学   7855篇
综合类   526篇
一般理论   86篇
预防医学   4182篇
眼科学   1127篇
药学   3671篇
中国医学   69篇
肿瘤学   3530篇
  2023年   245篇
  2022年   436篇
  2021年   1060篇
  2020年   603篇
  2019年   1015篇
  2018年   1256篇
  2017年   906篇
  2016年   984篇
  2015年   1140篇
  2014年   1687篇
  2013年   2303篇
  2012年   3611篇
  2011年   3751篇
  2010年   2094篇
  2009年   1736篇
  2008年   3393篇
  2007年   3603篇
  2006年   3482篇
  2005年   3525篇
  2004年   3255篇
  2003年   3066篇
  2002年   3000篇
  2001年   535篇
  2000年   445篇
  1999年   556篇
  1998年   625篇
  1997年   541篇
  1996年   443篇
  1995年   475篇
  1994年   349篇
  1993年   371篇
  1992年   343篇
  1991年   328篇
  1990年   308篇
  1989年   279篇
  1988年   240篇
  1987年   256篇
  1986年   237篇
  1985年   264篇
  1984年   293篇
  1983年   254篇
  1982年   311篇
  1981年   313篇
  1980年   257篇
  1979年   168篇
  1978年   172篇
  1977年   179篇
  1976年   145篇
  1975年   97篇
  1974年   85篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Our purposes were to determine the incidence of BK viruria, viremia or nephropathy with tacrolimus (FK506) versus cyclosporine (CyA) and whether intensive monitoring and discontinuation of mycophenolate (MMF) or azathioprine (AZA), upon detection of BK viremia, could prevent BK nephropathy. We randomized 200 adult renal transplant recipients to FK506 (n = 134) or CyA (n = 66). Urine and blood were collected weekly for 16 weeks and at months 5, 6, 9 and 12 and analyzed for BK by polymerase chain reaction (PCR). By 1 year, 70 patients (35%) developed viruria and 23 (11.5%) viremia; neither were affected independently by FK506, CyA, MMF or AZA. Viruria was highest with FK506-MMF (46%) and lowest with CyA-MMF (13%), p = 0.005. Viruria >/= 9.5 log(10) copies/mL was associated with a 3-fold increased risk of viremia and a 13-fold increased risk of sustained viremia. After reduction of immunosuppression, viremia resolved in 95%, without increased acute rejection, allograft dysfunction or graft loss. No BK nephropathy was observed. Choice of calcineurin inhibitor or adjuvant immunosuppression, independently, did not affect BK viruria or viremia. Viruria was highest with FK506-MMF and lowest with CyA-MMF. Monitoring and preemptive withdrawal of immunosuppression were associated with resolution of viremia and absence of BK nephropathy without acute rejection or graft loss.  相似文献   
52.
The assessment of the medical lethality and intent of suicide attempts has been considered an important area of research for those interested in suicide. The current study examined the usefulness of the Risk-Rescue Rating Scale with 109 adolescent suicide attempters and found a restricted range of variability, which, in turn, resulted in poor interrater reliability on a number of items. Results suggest that the Risk-Rescue Rating Scale is of limited usefulness with adolescents, and alternative approaches to assessing lethality and suicidal intent with this age group are discussed.  相似文献   
53.
PURPOSE: Epidermal growth factor receptor is expressed in pediatric malignant solid tumors. We conducted a phase I trial of gefitinib, an epidermal growth factor receptor tyrosine kinase inhibitor, in children with refractory solid tumors. PATIENTS AND METHODS: Gefitinib (150, 300, 400, or 500 mg/m2) was administered orally to cohorts of three to six patients once daily continuously until disease progression or significant toxicity. Pharmacokinetic studies were performed during course one (day 1 through 28). RESULTS: Of the 25 enrolled patients, 19 (median age, 15 years) were fully evaluable for toxicity and received 54 courses. Dose-limiting toxicity was rash in two patients treated with 500 mg/m2 and elevated ALT and AST in one patient treated with 400 mg/m2. The maximum-tolerated dose was 400 mg/m2/d. The most frequent non-dose-limiting toxicities were grade 1 or 2 dry skin, anemia, diarrhea, nausea, and vomiting. One patient with Ewing's sarcoma had a partial response. Disease stabilized for 8 to > or = 60 weeks in two patients with Wilms' tumor and two with brainstem glioma (one exophytic). At 400 mg/m2, the median peak gefitinib plasma concentration was 2.2 microg/mL (range, 1.2 to 3.6 microg/mL) and occurred at a median of 2.3 hours (range, 2.0 to 8.3 hours) after drug administration. The median apparent clearance and median half-life were 14.8 L/h/m2 (range, 3.8 to 24.8 L/h/m2) and 11.7 hours (range, 5.6 to 22.8 hours), respectively. Gefitinib systemic exposures were comparable with those associated with antitumor activity in adults. CONCLUSION: Oral gefitinib is well tolerated in children. Development of the drug in combination with cytotoxic chemotherapy will be pursued.  相似文献   
54.

Background  

Malaria, caused by the parasite Plasmodium falciparum, is a significant source of morbidity and mortality in southern Zambia. In the Mapanza Chiefdom, where transmission is seasonal, Anopheles arabiensis is the dominant malaria vector. The ability to predict larval habitats can help focus control measures.  相似文献   
55.
56.
57.
58.
Objective: To examine the effectiveness of needle and syringe programmes (NSPs) in preventing HIV transmission among injecting drug users (IDUs).Methods: An ecological study design was used to determine change in HIV prevalence among injecting drug users between cities with and without NSPs. Several data sources, such as electronic journal databases, surveillance reports, websites, and index review of relevant journals, were used to identify studies of HIV seroprevalence among IDUs, and presence of NSPs. The rate of change in HIV prevalence was estimated by regression analysis.Results: There were 778 years of data from 99 cities globally included in the analysis. HIV prevalence decreased by 18.6% per annum in cities that introduce NSPs, and increased by 8.1% in cities that had never introduced NSPs (mean difference −24.7% [95% CI: −43.8, 0.5%], P=0.06). The mean difference was –33% when comparison was weighted to one over the variance of the regression estimator (29% decrease in cities with NSPs and 5% increase in cities without NSPs, P<0.001). When analysis was restricted to cities with first HIV seroprevalence less than 10%, the average annual change in seroprevalence was 18% lower in cities with NSPs (P=0.03).Conclusions: Despite the inherent limitations within an ecological study design, the study provides additional evidence that NSPs reduce transmission of HIV infection. The rapid spread of HIV among IDU populations and increasing rates of injecting in many countries calls for scaling up of NSPs as well as other harm reduction strategies.  相似文献   
59.
OBJECTIVE: The objective of this study was to determine if temporomandibular joint (TMJ) samples positive for Chlamydia trachomatis have a greater presence of tumor necrosis factor-alpha (TNFalpha) or interleukin-6 (IL-6) when compared with Chlamydia-negative samples. STUDY DESIGN: Posterior bilaminar tissue samples removed during TMJ surgery from 70 patients were evaluated. Cryosections were stained using monoclonal antibody that identifies C. trachomatis. The presence of IL-6 and TNFalpha were evaluated by immunostaining in 15 samples positive and in 25 samples negative for the presence of C. trachomatis. RESULTS: Of the 70 TMJ samples, 32 (46%) were positive for C. trachomatis. In 15 samples positive for C. trachomatis, 10 (67%) were positive for TNFalpha and 7 (47%) for IL-6. In 25 samples negative for C. trachomatis, only 4 (16%) were positive for TNFalpha and only 2 (8%) for IL-6. Differences in C. trachomatis-positive samples versus negative were significant for both TNFalpha (P < .002) and IL-6 (P < .008). CONCLUSION: The presence of C. trachomatis in the TMJ is associated with a significantly increased presence of TNFalpha and IL-6.  相似文献   
60.
Background contextLumbar zygapophyseal joint (Z-joint) synovial cysts can cause low back pain (LBP), spinal stenosis, and lower extremity radiculopathy. In the literature, there are several minimally invasive techniques described with mixed results. Typical recommended treatment is surgical resection of the cyst. Currently, there is little information available concerning the efficacy and outcome with treatment of Z-joint synovial cyst by percutaneous, fluoroscopic, contrast-enhanced distention, and rupture.PurposeTo evaluate the therapeutic value and safety of Z-joint cyst rupture in symptomatic patients.Study design/settingRetrospective cohort study in an academic outpatient physiatric spine practice.Patient sampleThirty-two patients with moderate-to-severe LBP and leg pain (18 women and 14 men with an age range of 46–86 y; mean age, 66 y) with an average preprocedure symptom duration of 5 months. The patient's clinical symptoms correlated with magnetic resonance imaging studies documenting the presence of a synovial cyst at the corresponding level and side of symptoms. Patients had at least 6 months follow-up (range, 6–24).Outcome measuresNumerical Pain Rating Scale, Roland-Morris Disability Questionnaire, North American Spine Society four-point patient satisfaction survey, recurrence of synovial cyst requiring repeat rupture, and need for surgical intervention.MethodsPatients with symptomatic lumbar Z-joint synovial cyst were identified and their charts were reviewed. Patients included in the study either had symptomatic lumbar LBP or LBP with associated lower extremity radiculopathy. All patients in the study had magnetic resonance imaging's documenting Z-joint synovial cyst that corresponded with the patients' clinical symptoms. All patients received fluoroscopically guided, contrast-enhanced, percutaneous facet cyst distention and rupture followed by an intra-articular facet joint injection of 1 cc kenalog and 1 cc of 1% lidocaine. Seventeen of the patients also received a transforaminal epidural steroid injection just before facet cyst rupture. Telephone follow-up was conducted on all patients.ResultsExcellent long-term (average follow-up 1 y; range, 6–24 mo) pain relief was achieved in 23 (72%) of 32 patients undergoing facet cyst rupture. Twelve patients (37.5%) had synovial cyst recurrence and 11 chose to undergo repeat rupture, which resulted in 5 patients (45%) obtaining complete relief of symptoms and 6 patients (55%) requiring surgical intervention for cyst removal. Fisher exact test demonstrated that all patients who did not have a cyst recurrence were a success and obtained complete relief of symptoms (p<.0002). Patients who underwent a repeat rupture had a 50% chance of a successful outcome. There was no statistical significance between a successful outcome and level of facet cyst rupture, the presence of spondylolisthesis, sex, age, or having a transforaminal epidural steroid injection at the time of the procedure. Wilcoxon signed-rank test demonstrated that the difference in Numerical Pain Rating Scale and Roland-Morris Disability Questionnaire scores before and after the procedure was statistically significant (p<.0001). No complications were reported.ConclusionsFluoroscopic percutaneous Z-joint cyst rupture appears to be a safe and effective minimally invasive treatment option. This procedure should be considered before surgical intervention.  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