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   21417篇
  免费   2431篇
  国内免费   47篇
耳鼻咽喉   207篇
儿科学   728篇
妇产科学   548篇
基础医学   3192篇
口腔科学   573篇
临床医学   2456篇
内科学   3591篇
皮肤病学   340篇
神经病学   1579篇
特种医学   842篇
外国民族医学   3篇
外科学   2828篇
综合类   505篇
一般理论   25篇
预防医学   2561篇
眼科学   366篇
药学   1782篇
中国医学   92篇
肿瘤学   1677篇
  2021年   229篇
  2020年   185篇
  2019年   252篇
  2018年   361篇
  2017年   220篇
  2016年   254篇
  2015年   311篇
  2014年   427篇
  2013年   612篇
  2012年   901篇
  2011年   936篇
  2010年   527篇
  2009年   498篇
  2008年   837篇
  2007年   911篇
  2006年   966篇
  2005年   930篇
  2004年   874篇
  2003年   848篇
  2002年   838篇
  2001年   814篇
  2000年   824篇
  1999年   734篇
  1998年   327篇
  1997年   277篇
  1996年   298篇
  1995年   275篇
  1994年   245篇
  1993年   217篇
  1992年   579篇
  1991年   501篇
  1990年   500篇
  1989年   454篇
  1988年   435篇
  1987年   440篇
  1986年   427篇
  1985年   384篇
  1984年   312篇
  1983年   252篇
  1982年   200篇
  1981年   189篇
  1980年   176篇
  1979年   280篇
  1978年   216篇
  1977年   176篇
  1976年   160篇
  1975年   172篇
  1974年   195篇
  1973年   187篇
  1972年   191篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
OBJECTIVE: To investigate the relationship between health locus of control (HLOC), distress, and protease inhibitor (PI) utilization in gay/bisexual men in all stages of HIV illness. METHOD: A total of 173 men participating in a longitudinal study of the psychological effects of HIV illness were administered a number of psychological distress measures and the HLOC scale. The association between the HLOC subscales, distress, and PI utilization was evaluated. RESULTS: In addition to physical symptoms, the attribution of health status to chance or fate significantly predicted depressive symptoms, feelings of hopelessness, and recent life stress. Results also demonstrated a significant relationship between strong, positive beliefs in doctors and other health care professionals and PI utilization. CONCLUSION: The results of this study point to a strong association between beliefs that health status is related to chance or fate and distress. In addition, beliefs in physicians and other health care providers appear to contribute to decisions to initiate PI therapy.  相似文献   
992.
Prevalence of celiac antibodies in children with neurologic disorders   总被引:1,自引:0,他引:1  
Neurologic complications are a recognized but unusual manifestation of celiac disease (CD) in adults and children. The use of antigliadin and antiendomysial antibodies in screening has revealed the frequency of CD among symptom-free individuals to be high. Recently, a high frequency (57%) of antigliadin antibodies was demonstrated in adult patients with neurologic dysfunctions of unknown cause. We investigated the yield of screening for CD in children with common neurologic disorders. One hundred sixty-seven children, 1-16 years of age, were included in the study: 41 with migraine headaches, 39 with attention-deficit disorder with or without hyperactivity, 36 with epileptic disorders, and 51 with hypotonia and motor abnormalities. Positive IgG antigliadin antibodies were evident in 22 children (13%) in the study group compared with three children (9%) in the control group. However, in all children, negative IgA and endomysial antibodies were observed; thus duodenal biopsies were not performed. Contrary to studies performed in adults, these results did not demonstrate any relationship between common neurologic disorders without a specific diagnosis during childhood and CD. Thus screening for CD does not need to be routinely included in the diagnostic evaluation of children with these disorders.  相似文献   
993.
Breast cancer patients often receive both paclitaxel and zoledronic acid as part of their treatment, and these drugs are reported to have synergistic effects on the induction of apoptosis of breast cancer cells in vitro. We have found that the synergistic interaction is drug sequence dependent, with maximal levels of apoptosis achieved when cells are treated with paclitaxel followed by zoledronic acid, as opposed to the reverse sequence or simultaneous treatment. The synergistic interaction persists at clinically relevant concentrations and incubation periods. We report that the sequential treatment is associated with cell cycle changes and depends on breast cancer cell characteristics, with hormone independence, mutated p53 status and presence of BRCA1 gene being associated with higher levels of apoptosis. Finally, we have found that the synergistic induction of apoptosis is via zoledronic acid-mediated inhibition of the mevalonate pathway.  相似文献   
994.
PURPOSE: In this study, the differential gene expression changes following radiation-induced DNA damage in healthy cells from BRCA1/BRCA1 mutation carriers have been compared with controls using high-density microarray technology. We aimed to establish if BRCA1/BRCA2 mutation carriers could be distinguished from noncarriers based on expression profiling of normal cells. EXPERIMENTAL DESIGN: Short-term primary fibroblast cultures were established from skin biopsies from 10 BRCA1 and 10 BRCA2 mutation carriers and 10 controls, all of whom had previously had breast cancer. The cells were subjected to 15 Gy ionizing irradiation to induce DNA damage. RNA was extracted from all cell cultures, preirradiation and at 1 hour postirradiation. For expression profiling, 15 K spotted cDNA microarrays manufactured by the Cancer Research UK DNA Microarray Facility were used. Statistical feature selection was used with a support vector machine (SVM) classifier to determine the best feature set for predicting BRCA1 or BRCA2 heterozygous genotype. To investigate prediction accuracy, a nonprobabilistic classifier (SVM) and a probabilistic Gaussian process classifier were used. RESULTS: In the task of distinguishing BRCA1 and BRCA2 mutation carriers from noncarriers and from each other following radiation-induced DNA damage, the SVM achieved 90%, and the Gaussian process classifier achieved 100% accuracy. This effect could not be achieved without irradiation. In addition, the SVM identified a set of BRCA genotype predictor genes. CONCLUSIONS: We conclude that after irradiation-induced DNA damage, BRCA1 and BRCA2 mutation carrier cells have a distinctive expression phenotype, and this may have a future role in predicting genotypes, with application to clinical detection and classification of mutations.  相似文献   
995.
Previous studies have identified low patient accrual in large-scale cancer clinical trials, particularly for underrepresented groups, such as ethnic minorities, females, and patients >65 years. As there have been few studies examining participation in cancer genetics epidemiologic research, our objective was to identify clinical and demographic factors predicting enrollment in these studies. A total of 1,111 patients diagnosed with colorectal cancer presenting to a gastrointestinal oncology clinic were approached to enroll in a study investigating the role of the MSH6 gene in familial colorectal cancer. Patient consent was sought for providing a blood specimen for DNA analysis and review of medical records/tumor specimens and contacting family members to confirm the family history of cancer. Seven predictor variables for enrollment (age, sex, ethnicity, family history of colorectal cancer in a first-degree relative, presence of children, insurance type, and type of visit) were analyzed using logistic regression analysis to determine the effect on decision to enroll. Of 1,111 patients approached, 696 (62.6%) enrolled in the study. Of these approached individuals, 4.2% were of nonwhite ethnicity and 33.5% were age > or =65 years. Patients of white ethnicity [odds ratio (OR), 2.10; P = 0.018], males (OR, 1.47; P = 0.002), those ages < or =65 years (OR, 1.42; P = 0.009), and those with a first-degree relative with colorectal cancer (OR, 1.57; P = 0.005) were significantly more likely to enroll. Fewer than 4% of all participants denied permission for the study researchers to access information from medical records or to be recontacted by researchers to discuss the enrollment of additional family members. Our data suggest that, once subjects decided to enroll, the majority (88%) was comfortable with consenting to all study components, including the creation of cell lines and future recontact. Low participation rates for ethnic minorities, females, and elderly patients are similar for both cancer genetics and clinical trial studies.  相似文献   
996.
Attention-deficit hyperactivity disorder (ADHD) is the most common behavior disorder among children; methylphenidate is a drug frequently prescribed for the control of its symptoms. One of the potential side effects of methylphenidate that concerns parents is its impact on the growth of children, since the mechanism by which methylphenidate might influence growth is not known. As linear growth is associated with an increase in bone mineral density and turnover, this study was undertaken to evaluate bone mineral density by dual photon absorptiometry and bone turnover by measuring serum bone-specific alkaline phosphatase and the urinary deoxypyridinoline excretion rate in children treated with methylphenidate for 1 to 2 years as compared to a control group. There were no significant differences in bone mineral density at either the lumbar spine or femoral neck in the study group (0.662 +/- 0.04 and 0.735 +/- 0.07 g/cm2, respectively) as compared to the controls (0.675 +/- 0.05 g/cm2 and 0.734 +/- 0.07 g/cm2, respectively). Furthermore, there were no significant differences in serum bone-specific alkaline phosphatase in the study group (58 +/- 22 U/L) as compared to the control children (71 +/- 34 U/L) or in urinary deoxypyridinoline in the study group (34 +/- 38 nM/mM), as compared to the control group (27 +/- 12 nM/mM). In conclusion, our data do not support a significant effect of methylphenidate on bone mineral density turnover in children when used for 1 to 2 years.  相似文献   
997.
Pigtail catheter drain in the treatment of empyema thoracis.   总被引:1,自引:0,他引:1  
We compared the outcome of children with empyema managed either through thoracotomy with pleural debridment, conventional stiff chest drain, or pigtail chest drain. Compared to conventional drain, children who received either thoracotomy or pigtail catheters had a significantly decreased period of drain in situ, were afebrile earlier, were clinically improved earlier, and were discharged earlier.  相似文献   
998.
Neurofibromatosis type 1 and sporadic optic gliomas.   总被引:2,自引:0,他引:2  
AIMS: To compare the natural history of sporadic optic glioma with those associated with neurofibromatosis type 1 (NF1). METHODS: Optic glioma cases were identified using both the Manchester Children's Tumour Registry (CTR) and the North West Regional NF1 Database (NF1DB), with detailed information on natural history available from the former (in 34 of 36 cases identified). RESULTS: A total of 52 cases over a period of 41 years were identified. From the 34 whose natural history was known, almost all (n = 31) were symptomatic, with mean ages of presentation of 4.5 and 5.1 years for NF1 and sporadic cases respectively. The majority (n = 22) presented with visual impairment, seven of whom were blind in at least one eye. Sporadic cases were over twice as likely as NF1 to have visual impairment. Recurrence occurred in 12 patients. Fewer NF1 patients died as a direct result of their optic glioma, but overall mortality and 5 and 10 year survival rates between the two groups were similar. All five primary (non-metastatic) second central nervous system (CNS) tumours occurred in NF1 cases, two of these following radiotherapy. CONCLUSIONS: Symptomatic sporadic optic gliomas presented with impaired vision more frequently and were more aggressive than NF1 optic gliomas. Only optic glioma cases with NF1 were at risk of developing a second CNS tumour. Aggressive treatment of sporadic optic gliomas and early surveillance of NF1 optic gliomas may be required. The use of radiotherapy in these children requires further clarification.  相似文献   
999.
Studies investigating the relationship between the use of inflectional morphology and speech-perception abilities in children with SLI traditionally have employed synthetic speech stimuli. The purpose of this study was to replicate the findings reported in Leonard, McGregor, and Allen (1992) with an older group of children with SLI and to determine if the pattern of deficits seen for synthetic speech extends to perception of natural speech stimuli. The speech-perception abilities of 27 children between the ages of 6;11 and 8;11 (15 SLI and 12 NL) were compared using natural and synthetic versions of the [das]-[daS], [dabiba]-[dabuba], and [i]-[u] contrast pairs originally used in Leonard et al. The findings reported by Leonard et al. were replicated with synthetic speech but not for the natural speech. Use of inflectional morphology in obligatory contexts by the children with SLI was not significantly correlated with their perception abilities for any of the natural or synthetic speech-contrast pairs. Further, although both groups' ability to maintain the target contrast in memory declined over the span of the trials for all target contrasts for both natural and synthetic speech, the rate of decline did not differ significantly between the SLI and NL groups. Findings are discussed with respect to possible deficits in linking phonological representations to grammatical representations in children with SLI.  相似文献   
1000.
Background: When implemented in several common surgical procedures, clinical pathways have been reported to reduce costs and resource utilization, while maintaining or improving patient care. However, there is little data to support their use in more complex surgery. The objective of this study was to determine the effects of clinical pathway implementation in patients undergoing elective pancreaticoduodenectomy (PD) on cost and resource utilization.Methods: Outcome data from before and after the development of a clinical pathway were analyzed. The clinical pathway standardized the preoperative outpatient care, critical care, and postoperative floor care of patients who underwent PD. An independent department determined total costs for each patient, which included all hospital and physician costs, in a blinded review. Outcomes that were examined included perioperative mortality, postoperative morbidity, length of stay, readmissions, and postoperative clinic visits.Results: From January, 1996 to December, 1998, 148 consecutive patients underwent PD or total pancreatectomy; 68 before pathway development (PrePath) and 80 after pathway implementation (PostPath). There were no significant differences in patient demographics, comorbid conditions, underlying diagnosis, or use of neoadjuvant therapy between the two groups. Mean total costs were significantly reduced in PostPath patients compared with PrePath patients ($36,627 vs. $47,515; P = .003). Similarly, mean length of hospital stay was also significantly reduced in PostPath patients (13.5 vs. 16.4 days; P = .001). The total cost differences could not be attributed solely to differences in room and board costs. Cost and length-of-stay differences remained when outliers were excluded from the analysis. Despite these findings, there were no significant differences between PrePath and PostPath patients in terms of perioperative mortality (3% vs. 1%), readmissions within 1 month of discharge (15% vs. 11%), or mean number of clinic visits within 90 days of discharge (3.3 vs. 3.4 visits).Conclusions: The establishment of a clinical pathway for PD patients dramatically reduced costs and resource utilization without any apparent detrimental effect on quality of patient care. These findings support the implementation of clinical pathways for PD patients, as well as investigation into pathway care for other complex surgical procedures.  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