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   3314篇
  免费   203篇
  国内免费   6篇
耳鼻咽喉   13篇
儿科学   170篇
妇产科学   58篇
基础医学   353篇
口腔科学   120篇
临床医学   322篇
内科学   588篇
皮肤病学   51篇
神经病学   343篇
特种医学   305篇
外国民族医学   3篇
外科学   229篇
综合类   55篇
一般理论   1篇
预防医学   260篇
眼科学   100篇
药学   188篇
中国医学   1篇
肿瘤学   363篇
  2021年   22篇
  2019年   23篇
  2018年   34篇
  2017年   21篇
  2016年   30篇
  2015年   36篇
  2014年   52篇
  2013年   78篇
  2012年   84篇
  2011年   103篇
  2010年   84篇
  2009年   84篇
  2008年   160篇
  2007年   143篇
  2006年   157篇
  2005年   141篇
  2004年   127篇
  2003年   131篇
  2002年   105篇
  2001年   97篇
  2000年   110篇
  1999年   96篇
  1998年   53篇
  1997年   67篇
  1996年   67篇
  1995年   49篇
  1994年   40篇
  1993年   65篇
  1992年   81篇
  1991年   77篇
  1990年   87篇
  1989年   84篇
  1988年   67篇
  1987年   71篇
  1986年   83篇
  1985年   65篇
  1984年   70篇
  1983年   50篇
  1982年   45篇
  1981年   29篇
  1980年   41篇
  1979年   57篇
  1978年   35篇
  1977年   28篇
  1976年   25篇
  1975年   30篇
  1973年   26篇
  1972年   23篇
  1970年   20篇
  1969年   27篇
排序方式: 共有3523条查询结果,搜索用时 15 毫秒
71.
Albright AL  Sposto R  Holmes E  Zeltzer PM  Finlay JL  Wisoff JH  Berger MS  Packer RJ  Pollack IF 《Neurosurgery》2000,47(4):879-85; discussion 885-7
OBJECTIVE: This study was performed to evaluate the association between the type of neurosurgeon (general or pediatric) and either the extent of tumor removal or the frequency of complications in children undergoing malignant brain tumor resections. METHODS: Data were analyzed from three recent Children's Cancer Group studies: two on medulloblastomas/primitive neuroectodermal tumors and one on malignant gliomas. Neurosurgeons were classified as general neurosurgeons, as designated pediatric neurosurgeons in their institutions, or as members of the American Society of Pediatric Neurosurgeons (ASPN), which requires pediatric neurosurgical experience and practice standards. RESULTS: Data forms from 732 children were analyzed; 485 were from children with medulloblastomas/primitive neuroectodermal tumors, and 247 were from children with malignant gliomas. Operations were performed by 269 neurosurgeons, including 213 general neurosurgeons, 29 designated pediatric neurosurgeons, and 27 ASPN members. The mean number of operations per surgeon was 1.8, 4.9, and 7.6 for general neurosurgeons, designated pediatric neurosurgeons, and ASPN members, respectively. There was a significant relationship between the extent of tumor resection or the amount of residual tumor and the type of neurosurgeon. Designated pediatric neurosurgeons and ASPN members were more likely to remove more than 90% of the tumor and to leave less than 1.5 cc of residual tumor than were general neurosurgeons (P<0.05). In these studies, the probability of extensive tumor removal correlated with the number of operations the neurosurgeon performed (P<0.01). Neurological complications occurred in the following proportion of cases: general neurosurgeons, 23%; designated pediatric neurosurgeons, 32%; and ASPN members, 18%. CONCLUSION: Pediatric neurosurgeons are more likely than general neurosurgeons to extensively remove malignant pediatric brain tumors. In these tumors, extent of removal has been demonstrated to influence survival.  相似文献   
72.
 目的 研究Ewing’s肉瘤细胞系 (RM 82 )X 射线外照射后肿瘤坏死因子 (TNF α)和转化生长因子 (TGF β)mRNA表达水平的变化 ,探讨X 射线诱导内源性TNF α和TGF β产生的可能性及意义。 方法 应用实时荧光RT PCR ,检测接受不同剂量X 线照射 (2Gy ,5Gy ,10Gy ,2 0Gy ,30Gy ,4 0Gy)和受照后不同时间 (1h ,3h ,6h ,12h ,2 4h ,4 8h ,72h)。TNF α和TGF βmRNA表达水平的变化。 结果 RM 82细胞TNF αmRNA表达水平较外照射前显著升高。一方面受照后TNF αmRNA表达逐渐升高 ,照射剂量达 4 0Gy时TNF αmRNA表达水平达高峰 ,为正常对照组的 10 8倍 ;另一方面 ,照射后 3h后TNF αmRNA表达逐渐升高 ,6h达高峰 ,为正常对照组的 18倍。相反 ,TGF βmRNA表达水平X 射线照射前后无显著变化。结论 Ewing’s肉瘤细胞系 (RM 82 )接受X 线照射后TNF αmRNA表达明显升高 ,且呈现时间、剂量依赖性。放射治疗可诱导Ewing’s肉瘤细胞系 (RM 82...  相似文献   
73.
74.
Higher fat and energy intakes confer a survival advantage in cystic fibrosis (CF). There is a need to develop effective nutrition programmes that ensure optimal energy intake in CF.

Methodology:


A cross-sectional measurement of clinical characteristics and energy and fat intakes in patients attending the CF outpatients clinic of the John Hunter Hospital, Newcastle was undertaken. Twenty-nine subjects, mean age 12 years (range 4.3–20.2), completed weighed food records to determine the contribution of fat to the percentage of the recommended energy intake obtained and to document use of pancreatic enzyme replacement therapy.

Results:


Diets with a high percentage of energy derived from fat did not guarantee that individuals with CF met their energy requirements. Subjects with total fat intakes of 100 g per day or greater, however, achieved in excess of 110% recommended daily intake (RDI) for energy. Up to 47% of subjects consumed more pancreatic enzyme replacement capsules than shown to give maximum effectiveness.

Conclusion:


Setting a 100 g daily fat target is a realistic way of ensuring high energy intakes in CF. Fat ready reckoners would identify the fat content of food and prescribe specific numbers of pancreatic enzyme replacement capsules to be consumed with each meal or food item.  相似文献   
75.
Radiation therapy in the management of desmoid tumors   总被引:4,自引:0,他引:4  
Purpose: To evaluate the outcome of patients with extra-mesenteric desmoid tumors treated with radiation therapy, with or without surgery.

Methods and Materials: The outcome for 75 patients receiving radiation for desmoid tumor with or without complete gross resection between 1965 and 1994 was retrospectively reviewed utilizing univariate and multivariate statistical methods.

Results: With a median follow-up of 7.5 years, the overall freedom from relapse was 78% and 75% at 5 and 10 years, respectively. Of the total, 23 patients received radiation for gross disease because it was not resectable. Of these 23 patients, 7 sustained local recurrence, yielding a 31% actuarial relapse rate at 5 years. Radiation dose was the only significant determinant of disease control in this group. A dose of 50 Gy was associated with a 60% relapse rate, whereas higher doses yielded a 23% relapse rate (p < 0.05). The other 52 patients received radiation in conjunction with gross total resection of tumor. The 5- and 10-year relapse rates were 18% and 23%, respectively. No factor correlated significantly with disease outcome. There was no evidence that radiation doses exceeding 50 Gy improved outcome. Positive resection margins were not significantly deleterious in this group of irradiated patients. For all 75 patients, there was no evidence that radiation margins exceeding 5 cm beyond the tumor or surgical field improved local-regional control. Ultimately, 72 of the 75 patients were rendered disease-free, but 3 required extensive surgery (amputation, hemipelvectomy) to achieve this status. Significant radiation complications were seen in 13 patients. Radiation dose correlated with the incidence of complications. Doses of 56 Gy or less produced a 5% 15-year complication rate, compared to a 30% incidence with higher doses (p < 0.05).

Conclusions: Radiation is an effective modality for desmoid tumors, either alone or as an adjuvant to resection. For patients with negative resection margins, postoperative radiation is not recommended. Patients with positive margins should almost always receive 50 Gy of postoperative radiation. Unresectable tumors should be irradiated to a dose of approximately 56 Gy, with a 75% expectation of local control.  相似文献   

76.
77.
78.
79.
Purpose: To evaluate the feasibility and acceptability of a protocol determining the relationship between emergency team response (ETR) during childbirth and acute stress disorder (ASD) and post-traumatic stress disorder (PTSD) symptoms.

Methods: In a prospective, observational, cohort design, women experiencing ETR during childbirth were approached and recruited on postpartum day-1 and followed for six weeks. Demographics, obstetric and birth characteristics, ASD scores and PTSD scores (by Impact of Events Scale, IES and PCL-civilian) were recorded. Recruitment and retention rates were recorded, and scores were compared to women who did not experience ETR.

Results: Three hundred sixty-nine were approached and 249 were enrolled (67.5% recruitment rate). One hundred twenty-five completed all procedures (50.2% retention). Twenty experienced ETR (3.5% event rate), 12 enrolled (60.0% recruitment rate) and 8 completed the study (66.7% retention). The ETR group had higher PCL and IES scores (PCL: ETR median 12, non-ETR median 2, p?=?.08; IES: ETR median 22.5, non-ETR median 20, p?=?.08). ASD scores were similar between groups.

Conclusions: Methodology investigating the link between ETR and postpartum psychological distress is feasible and acceptable. A relationship between ETR and PTSD symptoms appears to exist, with ETR being associated with higher PTSD scores compared to non-ETR childbirths. Methods that incorporate awareness of the unique concerns of vulnerable populations are needed.  相似文献   
80.
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