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   58621篇
  免费   4096篇
  国内免费   176篇
耳鼻咽喉   532篇
儿科学   1650篇
妇产科学   1099篇
基础医学   7654篇
口腔科学   1050篇
临床医学   6424篇
内科学   11122篇
皮肤病学   853篇
神经病学   4910篇
特种医学   2375篇
外科学   9608篇
综合类   820篇
一般理论   57篇
预防医学   5696篇
眼科学   1306篇
药学   4128篇
  1篇
中国医学   55篇
肿瘤学   3553篇
  2023年   364篇
  2022年   475篇
  2021年   1195篇
  2020年   719篇
  2019年   1149篇
  2018年   1358篇
  2017年   1001篇
  2016年   1065篇
  2015年   1288篇
  2014年   1876篇
  2013年   2596篇
  2012年   3846篇
  2011年   3915篇
  2010年   2182篇
  2009年   1959篇
  2008年   3420篇
  2007年   3687篇
  2006年   3584篇
  2005年   3461篇
  2004年   3208篇
  2003年   3039篇
  2002年   2871篇
  2001年   896篇
  2000年   847篇
  1999年   859篇
  1998年   743篇
  1997年   602篇
  1996年   584篇
  1995年   577篇
  1994年   504篇
  1993年   440篇
  1992年   557篇
  1991年   507篇
  1990年   517篇
  1989年   498篇
  1988年   460篇
  1987年   404篇
  1986年   410篇
  1985年   452篇
  1984年   382篇
  1983年   310篇
  1982年   275篇
  1981年   247篇
  1980年   228篇
  1979年   247篇
  1978年   240篇
  1977年   193篇
  1976年   195篇
  1974年   210篇
  1973年   195篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
BACKGROUND AND PURPOSE: Viable tumor in a neck dissection specimen is important in predicting prognosis and directing treatment. Our purpose was to clarify the importance of size changes of regional metastases from head and neck squamous cell carcinoma on CT scans obtained before and after radiation therapy (RT) as a predictor of pathologic outcome. METHODS: Thirty-seven heminecks in 34 patients who underwent pre-RT CT, RT, post-RT CT, and post-RT neck dissection were reviewed. Thirteen hemineck specimens were pathologically positive. Decrease ratios of the largest axial dimension of the lymph nodes between the pre- and post-RT CT studies were calculated. RESULTS: Six of 37 heminecks had a decrease ratio greater than 50%. These yielded negative specimens after planned neck dissection. In two of 37 heminecks, the largest axial dimension of the largest node increased between studies, resulting in negative decrease ratio. One (decrease ratio, -20%) had a positive specimen, and the other (decrease ratio, -3%) had a negative specimen. No interval change in size in the largest node was noted in one of the 37 heminecks; its specimen was positive. Average decrease ratios were 41.2% (range, -3% to 62%) in the negative specimen group (n = 24) and 27.2% (range, -20% to 50%) in the positive specimen group (n = 13). Univariate analysis revealed that the decrease ratio was not a significant predictor of a positive surgical specimen (P =.154). CONCLUSION: Heminecks in which the decrease ratio was greater than 50% tended to have a negative surgical specimen. However, this trend was not statistically significant.  相似文献   
992.
PURPOSE: To characterize the impact of prolonged work, underfeeding, and sleep deprivation (i.e., sustained operations; SUSOPS) on physical and occupational related performance during military operational stress. METHODS: Ten male soldiers were tested on days 1 (D1), 3 (D3), and 4 (D4) of a control and an experimental week that included prolonged physical work (total daily energy expenditure approximately 4,500 kcal x d(-1)), underfeeding (approximately 1,600 kcal x d(-1)), and sleep deprivation (approximately 2 h x d(-1)). Body composition was measured with dual-energy x-ray absorptiometry (DEXA). Ballistic power was assessed by 30 repetitive squat jumps and bench-press throws. Military-relevant occupational performance was evaluated with a 10-min box lift, obstacle course, grenade throw, rifle marksmanship, and a 25-min wall-build task. RESULTS: Fat-free mass (-2.3%) and fat mass (-7.3%) declined (P 相似文献   
993.
994.
This paper reports findings from the carer component of the Gwynedd Dementia Study. It is based on carer interviews, using quantitative and qualitative data. It confirms earlier findings that carers for people with dementia are typically female and older than other carers, although it notes that caring husbands are amongst the oldest carers. The problems that are most common are those that cause psychological stress to carers. Carers were found to receive both help and appreciation from their families and to perceive neighbours to be helpful if needed. In Gwynedd, as elsewhere, levels of formal service inputs are low, but most of the carers appeared to receive the services they needed. Problems are primarily associated with crisis support and long-term care is accepted reluctantly. It is suggested that community care dementia specialists could play a supporting role for carers.  相似文献   
995.
The Parent-Infant Relationship Global Assessment Scale (PIRGAS; Zero to Three, 1994) provides a continuously distributed scale of infant-parent relationship adaptation, raging from 'well-adapted' to 'dangerously impaired'. The present study examines the predictive validity of the PIRGAS in a high-risk sample by coding relationship adaptation level from a single sample of 10 min of unstructured free play between mothers and their 20-month-old infants and examining its relationship to subsequent interaction with mothers and behavior problems at 24 months. Relationship adaptation assessed reliably from observations of only 10 min of free play between mothers and their infants at 20 months of age using PIRGAS predicted subsequent mother- infant interaction in a laboratory based problem-solving paradigm (Crowell procedure) at 24 months and internalizing symptomatology of Child Behavior Checklist at age 24 months. These results contribute to the predictive validity of the PIRGAS as a measure of mother-infant relationship adaptation.  相似文献   
996.
BACKGROUND: Finding a dose of an antipsychotic for maintenance therapy that is both safe and effective can be difficult because clinicians are unable to titrate dose against clinical response in patients who are already stable. Therapeutic monitoring of antipsychotic plasma levels has the potential for helping clinicians in dosage selection. With this in mind, we evaluated the usefulness of monitoring fluphenazine plasma levels for patients with schizophrenia who were receiving maintenance treatment with fluphenazine decanoate. METHOD: Thirty-one patients with schizophrenia were randomly assigned to low, medium, or high (0.1-0.3, 0.3-0.6, 0.6-1.0 ng/ml) plasma levels of fluphenazine. The dose of fluphenazine decanoate was adjusted in order to maintain patients in their assigned range. Side effects, psychopathology, and psychotic exacerbations were measured during the year following randomization. RESULTS: All of the psychotic exacerbations occurred during the first eight weeks following randomization, before patients had adequate time to reach their plasma level assignments. We did not find a relationship between plasma levels of fluphenazine and clinical outcomes or side effects. CONCLUSION: Our results do not provide support for the usefulness of monitoring fluphenazine plasma levels for patients receiving fluphenazine decanoate.  相似文献   
997.
Bilateral human fetal striatal transplantation in Huntington's disease   总被引:5,自引:0,他引:5  
BACKGROUND: Transplanted striatal cells have been demonstrated to survive, grow, establish afferent and efferent connections, and improve behavioral signs in animal models of Huntington's disease (HD). OBJECTIVE: To evaluate feasibility and safety and to provide preliminary information regarding the efficacy of bilateral human fetal striatal transplantation in HD. METHODS: Seven symptomatic patients with genetically confirmed HD underwent bilateral stereotactic transplantation of two to eight fetal striata per side in two staged procedures. Tissue was dissected from the lateral half of the lateral ventricular eminence of donors 8 to 9 weeks postconception. Subjects received cyclosporine for 6 months. RESULTS: Three subjects developed subdural hemorrhages (SDHs) and two required surgical drainage. One subject died 18 months after surgery from probable cardiac arrhythmia secondary to severe atherosclerotic cardiac disease. Autopsy demonstrated clearly demarcated grafts of typical developing striatal morphology, with host-derived dopaminergic fibers extending into the grafts and no evidence of immune rejection. Other adverse events were generally mild and transient. Mean Unified HD Rating Scale (UHDRS) motor scores were 32.9 plus minus 6.2 at baseline and 29.7 plus minus 7.5 12 months after surgery (p = 0.24). Post-hoc analysis, excluding one subject who experienced cognitive and motor deterioration after the development of symptomatic bilateral SDHs, found that UHDRS motor scores were 33.8 plus minus 6.2 at baseline and 27.5 plus minus 5.2 at 12 months (p = 0.03). CONCLUSIONS: Transplantation of human fetal striatal cells is feasible and survival of transplanted cells was demonstrated. Patients with moderately advanced HD are at risk for SDH after transplantation surgery.  相似文献   
998.
PURPOSE: We report the synthesis of a mucin-related O-linked glycopeptide, alpha-N-acetylgalactosamine-O-serine/threonine (Tn), which is highly simplistic in its structure and can induce a relevant humoral response when given in a trimer or clustered (c) formation. We tested for an antitumor effect, in the form of a change in the posttreatment versus pretreatment prostate-specific antigen (PSA) slopes, that might serve as a surrogate for effectiveness of vaccines in delaying the time to radiographic progression. METHODS: We compared the antibody response to immunization with two conjugates, Tn(c)-keyhole limpet hemocyanin (KLH) and Tn(c)-palmitic acid (PAM) with the saponin immunologic adjuvant QS21, in a phase I clinical trial in patients with biochemically relapsed prostate cancer. Patients received Tn(c)-KLH vaccine containing either 3, 7, or 15 microg of Tn(c) per vaccination. Ten patients received 100 microg of Tn(c)-PAM. QS21 was included in all vaccines. Five vaccinations were administered subcutaneously during 26 weeks with an additional booster vaccine at week 50. RESULTS: Tn(c), when given with the carrier molecule KLH and QS21, stimulated the production of high-titer immunoglobulin M (IgM) and IgG antibodies. Inferior antibody responses were seen with T(c)-PAM. There was no evidence of enhanced immunogenicity with increasing doses of vaccine. An antitumor effect in the form of a decline in posttreatment versus pretreatment PSA slopes was also observed. CONCLUSION: A safe synthetic conjugate vaccine in a trimer formation was developed that can break immunologic tolerance by inducing specific humoral responses. It seemed to affect the biochemical progression of the disease as determined by a change in PSA log slope.  相似文献   
999.
The presence of contrast enhancement in a brain tumor is often regarded as a sign of malignancy. The authors identified 314 patients with malignant and low-grade supratentorial glial neoplasms in an unselected population, 58 of which lacked contrast enhancement on preoperative neuroimaging. Nonenhancing gliomas were malignant in approximately one third of cases, especially in older patients. Histologic confirmation of the diagnosis is therefore important in all patients suspected of harboring a primary glial neoplasm.  相似文献   
1000.
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