全文获取类型
收费全文 | 2748篇 |
免费 | 216篇 |
国内免费 | 10篇 |
专业分类
耳鼻咽喉 | 21篇 |
儿科学 | 171篇 |
妇产科学 | 23篇 |
基础医学 | 276篇 |
口腔科学 | 92篇 |
临床医学 | 252篇 |
内科学 | 599篇 |
皮肤病学 | 44篇 |
神经病学 | 114篇 |
特种医学 | 327篇 |
外科学 | 322篇 |
综合类 | 95篇 |
预防医学 | 309篇 |
眼科学 | 58篇 |
药学 | 150篇 |
中国医学 | 10篇 |
肿瘤学 | 111篇 |
出版年
2021年 | 29篇 |
2020年 | 19篇 |
2019年 | 27篇 |
2018年 | 32篇 |
2017年 | 30篇 |
2016年 | 23篇 |
2015年 | 48篇 |
2014年 | 65篇 |
2013年 | 110篇 |
2012年 | 99篇 |
2011年 | 115篇 |
2010年 | 96篇 |
2009年 | 105篇 |
2008年 | 101篇 |
2007年 | 117篇 |
2006年 | 95篇 |
2005年 | 97篇 |
2004年 | 77篇 |
2003年 | 69篇 |
2002年 | 87篇 |
2001年 | 67篇 |
2000年 | 57篇 |
1999年 | 66篇 |
1998年 | 95篇 |
1997年 | 73篇 |
1996年 | 81篇 |
1995年 | 63篇 |
1994年 | 64篇 |
1993年 | 58篇 |
1992年 | 53篇 |
1991年 | 44篇 |
1990年 | 64篇 |
1989年 | 74篇 |
1988年 | 56篇 |
1987年 | 76篇 |
1986年 | 68篇 |
1985年 | 62篇 |
1984年 | 35篇 |
1983年 | 38篇 |
1982年 | 34篇 |
1981年 | 38篇 |
1980年 | 21篇 |
1979年 | 30篇 |
1978年 | 29篇 |
1977年 | 29篇 |
1976年 | 26篇 |
1975年 | 28篇 |
1974年 | 13篇 |
1973年 | 12篇 |
1971年 | 10篇 |
排序方式: 共有2974条查询结果,搜索用时 31 毫秒
1.
2.
Fertility in Persons with Epilepsy: 1935–1974 总被引:18,自引:17,他引:1
Data from the Rochester-Olmsted County Medical Records Linkage Project were utilized to assess fertility in persons with epilepsy. Population age-specific reproduction rates for Rochester residents for the years 1935-1974 were estimated using the number of live births from the Minnesota Department of Health Statistics and Vital Statistics of the U.S. for comparison with rates in affected persons. Overall, fertility rates were significantly reduced to 80% of expected for affected males and 85% for affected females. Individuals with partial seizures (simple and complex) were disadvantaged, whereas those with generalized onset were not. During the last 20 years of the study period, males were more disadvantaged than females. The male-female difference was greatest during the time of low population fertility (after 1965). Male deficits were more marked after diagnosis; female deficits were more marked before diagnosis. Differences in the proportion of ever-married person-years between the sexes only partially explain the observed differences. 相似文献
3.
D Webber I P Braidman W R Robertson D C Anderson 《Journal of bone and mineral research》1989,4(6):809-815
Tartrate-resistant acid phosphatase activity (TRAPase) is widely used as a cytochemical marker to distinguish osteoclasts from macrophages and other related cell types. The degree of tartrate resistance, however, may depend on which reaction methods, tissues, or species are used. To investigate this further, we have measured the amount of cytochemical reaction product by microdensitometry. We compared osteoclast acid phosphatase (APase) activity in fresh frozen sections of neonatal rat calvaria using two different reaction methods; one is commonly employed for qualitative histochemistry and includes alpha naphthyl phosphate as substrate, simultaneous coupling to the chromagen Fast Garnet, and a 30-minute reaction time (method A). The other may be used to measure enzyme reaction rates in cells in situ and employs conditions suitable for initial velocity kinetics, namely naphthol-ASBI phosphate as substrate, post coupling to Fast Garnet, and a 2-minute reaction time. Although enzyme reaction rates differed greatly between the two methods, significant inhibition of APase activity by tartrate was observed in calvarial osteoclasts (69% and 59% with methods A and B, respectively), osteoblasts, and spleen macrophages. Using method B, mouse calvarial osteoclasts had similar APase activity to that seen in the rat. Tartrate produced little inhibition in these mouse cells, in contrast to the observations made with rat tissue, but murine spleen macrophages were significantly tartrate sensitive (40% inhibition with tartrate). On this basis, conclusions regarding the cell specificity of TRAPase should be treated cautiously. 相似文献
4.
School-Based Cardiovascular Health Promotion: The Child and Adolescent Trial for Cardiovascular Health (CATCH) 总被引:7,自引:0,他引:7
Cheryl L. Perry PhD Elaine J. Stone PhD MPH FASHA Guy S. Parcel PhD FASHA R. Curtis Ellison MD Philip R. Nader MD FASHA Larry S. Webber PhD Russell V. Luepker MD MS 《The Journal of school health》1990,60(8):406-413
The Child and Adolescent Trial for Cardiovascular Health (CATCH) is a multisite intervention research study that builds on significant progress made in school health education research in the 1980s. The study has three phases: Phase I deals with study design, intervention, and measurement development, Phase II involves the main trial in 96 schools in four states, and Phase III focuses on analysis. The intervention program targets third-fifth grade students and focuses on multiple cardiovascular health behaviors, including eating habits, physical activity, and cigarette smoking. Classroom curricula, school environmental change, and family involvement programs are developed for each grade level and behavioral focus. This paper describes Phase II of CATCH with a rationale for cardiovascular health promotion with youth. The process of change that appears to be necessary for school-based health promotion and that will be tested in CATCH are presented as a framework to guide these efforts. 相似文献
5.
Hao Wu Colin Webber Carmen Otero Fuentes Robert Bensen Karen Beattie Jonathan D Adachi Xiaoming Xie Farhang Jabbari David R Levy 《Journal l'Association canadienne des radiologistes》2007,58(3):167-175
OBJECTIVES: 1) To assess, with a peripheral magnetic resonance imaging system (pMRI), the prevalence of bony and soft tissue abnormalities in the knee joints of normal subjects, osteoarthritis (OA) patients, and individuals who have suffered an anterior cruciate ligament (ACL) rupture; and 2) to compare the prevalence among groups. METHODS: Magnetic resonance (MR) images of 28 healthy, 32 OA, and 26 ACL damaged knees were acquired with a 1.0-T pMRI system. Two radiologists graded the presence and severity of 9 MR image features: cartilage degeneration, osteophytes, subchondral cyst, bone marrow edema, meniscal abnormality, ligament integrity, loose bodies, popliteal cysts, and joint effusion. RESULTS: Ten of 28 healthy (35.7%), 24 of 26 ACL (92.3%), and all OA knees (100%) showed prevalent cartilage defects; 5 healthy (17.9%), 20 ACL (76.9%), and all OA knees (100%) had osteophytes; and 9 normal (32.1%), 21 ACL (80.8%), and 29 OA knees (90.6%) had meniscal abnormalities. One-half of the knees in the OA group (16 of 32, 50%) had subchondral cysts, and almost one-half had bone marrow edema (15 of 32, 46.9%). These features were not common in the ACL group (7.7%, and 11.5%, respectively) and were not observed in healthy knees. The OA group had the most severe cartilage defects, osteophytes, bone marrow edema, subchondral cysts, and meniscal abnormalities; the ACL group showed more severe cartilage defects, osteophytes, and meniscal abnormalities than did normal subjects. CONCLUSION: The results suggest that knees that have sustained ACL damage have OA-like reatures; most subjects (19 of 26, 73.1%) could be identified as in the early stage of OA. The prominent abnormalities present in ACL-damaged knees are cartilage defects, osteophytes, and meniscal abnormalities. 相似文献
6.
7.
BACKGROUND: We reviewed the publication record of all protocols submitted to the Capital District Health Authority Research Ethics Board (REB) in Halifax, Nova Scotia, for the period 1995-1996. Because of a heightened awareness of the issue, we hypothesized that there would be less publication bias (a failure to report negative results) and a higher publication rate from completed studies, than previously reported. METHODS: Closed studies were identified from the REB database. Publications were identified by the investigators, requests from sponsors, and a literature review. For each publication, we identified authors, title, journal, number of subjects enrolled, and whether or not the publication was a report of a randomized clinical trial. Comparisons were done using a Student's t test, the Chi-square statistic, or Fisher's exact test as appropriate. RESULTS: From the database of closed studies, 106 remained unpublished, while completed investigations resulted in 84 publications (44% publication rate). The median time to publication was 32.5 months. Publication of statistically significant results occurred in 71/84 trials. Publication of protocols submitted by departments ranged from 91% (anesthesia; 10/11) to 25% [nursing; 2/8 (P<0.05)]. Trials investigating new drugs in Phase 3 or 4 studies were more likely to be published than trials investigating agents in Phase 1 or 2 (P<0.05), and were less likely to be published if sponsored by a pharmaceutical company (P<0.05). CONCLUSIONS: Publication bias continues to be a problem, particularly for early phase investigative studies. Our results suggest that a different approach is required to reduce publication bias. The role that REBs and peer-reviewed journals might play requires further exploration. 相似文献
8.
目的 探讨创伤后迟发性脑肿胀的临床特点、发病机制与治疗。方法 回顾性分析1998年1月~2005年6月年收治的17例迟发性脑肿胀患者的临床特点和救治情况。结果 所有颅脑损伤患者采用保守治疗后均有好转,但于伤后5-10d出现恶化,CT复查有脑肿胀,经加强综合脱水等治疗后16例治愈,1例死亡。结论 迟发性脑肿胀好发于对冲性额、颞叶挫裂伤伴明显蛛网膜下腔出血、硬膜下薄层血肿及早期CT有脑肿胀者。其发病机制可能与创伤后的迟发性脑血管痉挛、微循环障碍、静脉回流障碍及甘露醇作用下降等因素有关。此类患者病情隐蔽性强,应加强观察、积极行CT复查,如能早期明确诊断,保守治疗多数效果良好。 相似文献
9.
The actions of methacholine, phenylephrine, salbutamol and histamine on mucus secretion from the ferret in-vitro trachea 总被引:3,自引:0,他引:3
Methacholine, phenylephrine and histamine produced highly significant and salbutamol significant increases in the rate of mucus secretion from the ferret trachea. Methacholine, phenylephrine and histamine all produced highly significant increases in the rate of output of lysozyme, but the concentration of lysozyme in the mucus was significantly increased only by phenylephrine. Salbutamol produced no significant change in the output of lysozyme, and the concentration of lysozyme in the mucus was significantly decreased. It is concluded that methacholine, phenylephrine and histamine are potent stimulators of serous cell secretion whereas salbutamol has only a weak secretory action on these cells. Methacholine, histamine and salbutamol probably stimulate secretion from mucous cells as well as from serous cells. The increase in the concentration of lysozyme produced by phenylephrine may be due to stimulation of a fluid reabsorption mechanism. 相似文献
10.
Retrorenal colon: implications for percutaneous diskectomy 总被引:1,自引:0,他引:1
It has been recommended that computed tomography (CT) with the patient prone be performed in every patient undergoing percutaneous diskectomy; this would enable detection of a retrorenal location of the colon, which could interfere with the percutaneous procedure. In this evaluation of 346 prone CT studies, only one patient (0.29%) was found to have retrorenal or retropsoas bowel that would have been perforated at diskectomy. Because of this extremely low prevalence, the performance of prone CT in every patient undergoing percutaneous lumbar diskectomy is not believed to be necessary. 相似文献