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   1633篇
  免费   170篇
  国内免费   13篇
耳鼻咽喉   57篇
儿科学   57篇
妇产科学   29篇
基础医学   195篇
口腔科学   43篇
临床医学   194篇
内科学   308篇
皮肤病学   12篇
神经病学   105篇
特种医学   111篇
外科学   284篇
综合类   31篇
预防医学   150篇
眼科学   16篇
药学   105篇
中国医学   2篇
肿瘤学   117篇
  2021年   21篇
  2019年   16篇
  2018年   15篇
  2016年   20篇
  2015年   27篇
  2014年   16篇
  2013年   36篇
  2012年   62篇
  2011年   63篇
  2010年   42篇
  2009年   40篇
  2008年   49篇
  2007年   68篇
  2006年   67篇
  2005年   60篇
  2004年   64篇
  2003年   65篇
  2002年   43篇
  2001年   45篇
  2000年   69篇
  1999年   43篇
  1998年   34篇
  1997年   23篇
  1996年   21篇
  1995年   27篇
  1994年   37篇
  1993年   22篇
  1992年   48篇
  1991年   35篇
  1990年   38篇
  1989年   41篇
  1988年   39篇
  1987年   42篇
  1986年   39篇
  1985年   31篇
  1984年   26篇
  1983年   27篇
  1982年   17篇
  1981年   22篇
  1979年   23篇
  1978年   26篇
  1977年   18篇
  1976年   30篇
  1975年   14篇
  1974年   19篇
  1973年   19篇
  1972年   13篇
  1970年   15篇
  1969年   16篇
  1968年   14篇
排序方式: 共有1816条查询结果,搜索用时 15 毫秒
1.
Digestive Diseases and Sciences -  相似文献   
2.
Using the SF-12 to measure physical and mental functioning, the authors examine the intra-individual changes in health-related quality of life (HRQOL) 6 months post-discharge for depressed older adults. In addition, they examine three sets of predictors that might influence these changes. The sample of depressed older adults was recruited from an inpatient geropsychiatry unit. Although their physical and mental health scores on the SF-12 were lower than comparable norms, the sample showed an average increase in their mental functioning but a decrease in the physical functioning over the 6 months. Negative life-events were significant predictors of people who reported no change in their mental health functioning and decreases in their physical health functioning. Interestingly, those who experienced positive life events were more likely to report declines and younger participants were more likely to report no change in their physical functioning. The findings indicate that the effects of depression on HRQOL can have enduring effects on a sample of previously hospitalized older adults. The significance of life event changes might signify the importance of taking into account non-traditional areas of medical interventions. Further, the findings indicate the usefulness of the SF-12 quantifying HRQOL outcomes.  相似文献   
3.
Some 50% of human cancers are associated with mutations in the core domain of the tumor suppressor p53. Many mutations are thought just to destabilize the protein. To assess this and the possibility of rescue, we have set up a system to analyze the stability of the core domain and its mutants. The use of differential scanning calorimetry or spectroscopy to measure its melting temperature leads to irreversible denaturation and aggregation and so is useful as only a qualitative guide to stability. There are excellent two-state denaturation curves on the addition of urea that may be analyzed quantitatively. One Zn2+ ion remains tightly bound in the holo-form of p53 throughout the denaturation curve. The stability of wild type is 6.0 kcal (1 kcal = 4.18 kJ)/mol at 25°C and 9.8 kcal/mol at 10°C. The oncogenic mutants R175H, C242S, R248Q, R249S, and R273H are destabilized by 3.0, 2.9, 1.9, 1.9, and 0.4 kcal/mol, respectively. Under certain denaturing conditions, the wild-type domain forms an aggregate that is relatively highly fluorescent at 340 nm on excitation at 280 nm. The destabilized mutants give this fluorescence under milder denaturation conditions.  相似文献   
4.
The purpose of this study was to examine the levels of anxiety of mothers with children in pediatric intensive care units with different types of visitation policies, both structured and individualized Forty subjects were obtained from two children's hospitals A comparative research design was used Data showed that mothers who experienced individualized visitation had significantly lower anxiety scores (p < 005) than mothers who experienced structured visitation Findings also revealed that mothers viewed their child's illness as less severe when individualized visitation was permitted as opposed to structured visitation.  相似文献   
5.
6.
The records of 150 consecutive patients undergoing thoracoabdominal aortic replacement from 1980 to 1991 were retrospectively reviewed. There were 89 men and 61 women; mean age was 67.8 years (range: 33 to 88 years). Since June 1989, a multimodality prospective perioperative protocol was used to reduce the risk of spinal cord dysfunction. Ischemia is minimized by complete intercostal reimplantation whenever possible, cerebrospinal fluid drainage, and maintenance of proximal hypertension during cross-clamping. Spinal cord metabolism is reduced by moderate hypothermia, high-dose barbiturates, and avoidance of hyperglycemia. Reperfusion injury is minimized by the use of mannitol, steroids, and calcium channel blockers. Ninety-seven percent of patients survived long enough for evaluation of their neurologic function. Spinal cord dysfunction was reduced from 6 of 108 (6%) in the preprotocol group to 0 of 42 in the protocol group (0%) (p less than 0.01). The overall 30-day operative mortality was not significantly different between the groups (9% versus 12%, p = NS). A multimodality protocol appears to be effective in reducing the risk of spinal cord injury during thoracoabdominal aortic replacement.  相似文献   
7.
目的 探索LDH实验检测细胞活力的可行性。方法 原代培养骨髓细胞和软骨细胞,用LDH实验测定上述两组细胞的活力,并与镜下活体观察到细胞的生长状况相比较。与目前比较成熟的测定细胞活力的MTS实验的测得的值相比较。结果 LDH实验对上述两组细胞的活力的测定结果与镜下活体观察到的结果相符合。与MTS实验的测得的结果经统计学处理无显著差异。结论 LDH实验可用于细胞活力的直接测定,而对活细胞的生存、繁殖无影响。  相似文献   
8.
Over recent years, Bradford has had a consistently high perinatal mortality rate (PNMR), especially amongst its Asian population, 66% of whom originate from Pakistan. There is a high incidence of consanguineous marriages reported among Pakistani and Muslim couples. Often, this observation is used to explain their higher PNMR and congenital malformation rates. The factors affecting birth outcome in Pakistani women are complex and interrelated. Socioeconomic, genetic, biological and environmental factors all contribute to adverse birth outcome. In addition, these are complicated by discrimination, communication barriers and culture blaming. The aim of this paper is to challenge midwives and other health professionals to reconsider the overwhelming emphasis placed on consanguinity as a factor affecting birth outcome, and to recognise the impact and interplay of other confounding variables.  相似文献   
9.
OBJECTIVE: Depression after hip fracture surgery is prevalent and associated with increased mortality rates and impaired functional recovery. The incidence of new-onset depressive symptoms in patients initially not depressed after hip fracture surgery and their relationship with functional recovery is unknown. METHODS: A cohort of 139 nondepressed elderly patients (>60 years) hospitalized for hip fracture surgery were followed up for six months. Clinically significant depressive symptoms were defined as a score of 7 or more on the 15-item Geriatric Depression Scale. RESULTS: The authors found a cumulative incidence rate of 20.5% adjusted for dropouts. Multiple Cox-regression analyses yielded the presence of subthreshold symptoms of depression, anxiety, pain, and cognitive impairment at baseline, the premorbid level of mobility, and a history of (treated) depression as risk factors for incident depression (p <0.05). A forward, conditional procedure identified postoperative pain (hazard ratio [HR] = 1.32, 95% confidence interval [CI]: 1.14-1.53, Wald chi(2) = 13.57, df = 1, p <0.001) and baseline anxiety (HR = 1.25, 95% CI: 1.08-1.44, Wald chi(2) = 8.86, df = 1, p = 0.003) as the strongest independent risk factors. Incident depression was associated with a less favorable outcome at 3 months follow-up. CONCLUSION: This exploratory study identified two treatable baseline characteristics that predicted incident depression in nondepressed patients after hip-fracture surgery.  相似文献   
10.
Adult rat urothelial cells were transformed in vitro following treatment with a single dose of N-methyl-N-nitrosourea (MNU) or MNU treatment followed by promotion with sodium saccharin. This in vitro transformation process involves multiple steps: slow-growing 'pre-neoplastic' epithelial foci are induced 70-100 days after MNU treatment and from such foci rapidly proliferating immortal cell lines were established, some of which became tumorigenic after a further latent period. A series of epithelial cell lines and a single fibroblast cell line established in this way were analysed for the presence of transforming genes by DNA transfection into NIH3T3 cells. None of the epithelial cell lines induced foci in a focus formation assay. The single non-epithelial line induced foci and was found to contain an activated c-Ki-ras gene with a G----A transition in codon 12. To assay for the possible presence of transforming genes which were not active in a focus formation assay, two of the epithelial lines were analysed further by co-transfection with a dominant selectable marker, followed by selection and inoculation into nude mice. No tumours were induced within the latent period for tumour production by control cells transfected with NIH3T3 cell DNA (40-60 days). These results suggest that there is cell type specificity for oncogene activation during in vitro rat bladder transformation initiated by a single carcinogen and that ras gene activation is not a necessary step in urothelial transformation in vitro.  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