全文获取类型
收费全文 | 2420篇 |
免费 | 172篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 15篇 |
儿科学 | 112篇 |
妇产科学 | 30篇 |
基础医学 | 299篇 |
口腔科学 | 68篇 |
临床医学 | 224篇 |
内科学 | 444篇 |
皮肤病学 | 38篇 |
神经病学 | 251篇 |
特种医学 | 158篇 |
外科学 | 361篇 |
综合类 | 43篇 |
预防医学 | 224篇 |
眼科学 | 35篇 |
药学 | 148篇 |
肿瘤学 | 164篇 |
出版年
2021年 | 40篇 |
2020年 | 26篇 |
2018年 | 29篇 |
2017年 | 22篇 |
2016年 | 25篇 |
2015年 | 30篇 |
2014年 | 52篇 |
2013年 | 75篇 |
2012年 | 91篇 |
2011年 | 101篇 |
2010年 | 73篇 |
2009年 | 86篇 |
2008年 | 87篇 |
2007年 | 96篇 |
2006年 | 98篇 |
2005年 | 93篇 |
2004年 | 77篇 |
2003年 | 63篇 |
2002年 | 73篇 |
2001年 | 54篇 |
2000年 | 66篇 |
1999年 | 51篇 |
1998年 | 60篇 |
1997年 | 46篇 |
1996年 | 50篇 |
1995年 | 52篇 |
1994年 | 24篇 |
1993年 | 33篇 |
1992年 | 43篇 |
1991年 | 35篇 |
1990年 | 60篇 |
1989年 | 50篇 |
1988年 | 49篇 |
1987年 | 64篇 |
1986年 | 50篇 |
1985年 | 53篇 |
1984年 | 41篇 |
1983年 | 34篇 |
1982年 | 31篇 |
1980年 | 27篇 |
1979年 | 23篇 |
1977年 | 21篇 |
1975年 | 23篇 |
1974年 | 20篇 |
1973年 | 20篇 |
1972年 | 30篇 |
1971年 | 31篇 |
1970年 | 27篇 |
1969年 | 23篇 |
1968年 | 21篇 |
排序方式: 共有2614条查询结果,搜索用时 12 毫秒
11.
Exposure to cycad seed kernel is an etiologic factor for the western Pacific amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia complex (PDC). Traditionally processed cycad flours (n = 17) obtained from Chamorro residents of Guam and the adjacent island of Rota at risk for neurodegenerative disease were extracted and analyzed by high-performance liquid chromatography for content of beta-N-methylamino-L-alanine (BMAA) and methyl-azoxymethanol beta-D-glucoside (cycasin). Cycasin (detection limit: picomole) was present in concentrations of 0.004 to 75.93 micrograms/g (mean, 12.45 +/- 5.0 micrograms/g), and levels of BMAA (detection limit: subpicomole) ranged from 0.00 to 18.39 micrograms/g (mean, 5.44 +/- 1.56 micrograms/g). On average, cycasin content was approximately 10 times higher than that of BMAA. The largest concentrations of cycasin were found in samples from villages with a high reported prevalence of ALS/PDC. Ingestion of cycad-derived food would result in estimated human exposure to milligram amounts of cycasin per day. The cytotoxic properties of cycasin merit consideration in relation to the etiology of western Pacific ALS/PDC. 相似文献
12.
Grazyna Jasienska Anna Ziomkiewicz Inger Thune Susan F Lipson Peter T Ellison 《European journal of cancer prevention》2006,15(5):439-445
Variation in the risk of breast cancer observed among women and among populations may be explained by variation in lifetime exposure to estrogens. The suppressive effect of exercise on estradiol levels in women is well documented, but it is unknown whether habitual (i.e. typical daily) physical activity has a similar effect. Epidemiological data suggest that physical activity is one of the few modifiable factors capable of reducing the risk of breast cancer in women. We investigated whether variation in the amount of habitual activity corresponds to variation in estradiol levels in women of reproductive age. One hundred and thirty-nine regularly menstruating women 24-37 years of age collected daily saliva samples for one complete menstrual cycle and kept a daily log of physical activity. Saliva samples were analyzed for concentration of estradiol. We observed a negative relationship between habitual physical activity and salivary levels of estradiol. Mean estradiol was 21.1 pmol/l in the low, 17.9 pmol/l in the moderate and 16.6 pmol/l in the high activity group (all pairwise differences were statistically significant at P<0.009). A strong association exists between physical activity and levels of estradiol among women of reproductive age. A modern lifestyle, characterized by reduced physical activity, may therefore contribute to a rise in the levels of estradiol produced during menstrual cycles and thus to higher cumulative lifetime exposure to estradiol, resulting in a higher risk of breast cancer. 相似文献
13.
14.
A R Burgess B J Eastridge J W Young T S Ellison P S Ellison A Poka G H Bathon R J Brumback 《The Journal of trauma》1990,30(7):848-856
From January 1, 1985, to September 10, 1988, 210 consecutive patients with high-energy pelvic ring disruptions (exclusive of acetabular fractures) were admitted to a statewide referral center for adult multiple trauma. They were treated by one of four attending orthopaedic traumatologists per protocol as determined by their injury classification and hemodynamic status; the injury classification system was based on the vector of force involved and the quantification of disruption from that force, i.e., lateral compression, anteroposterior compression, vertical shear, and combined mechanical injury. Of the 210 patients, 162 had complete charts: 126 (78.0%) were admitted directly from the scene, 110 (67.9%) were injured in motor vehicle or motorcycle accidents, 25 (15.0%) were admitted in shock (blood pressure less than 90 mm Hg), the average Glasgow Coma Score was 13.2, and the average Injury Severity Score was 25.8. Treatment of the pelvic fracture included the following methods (alone or in combination): acute external fixation (45.0; 28.0%), open reduction/internal fixation (22; 13.5%), acute arterial embolization (11; 7.0%), and bedrest (68; 42.0%). Overall blood replacement averaged 5.9 units (lateral compression, 3.6 units; anteroposterior compression, 14.8 units; vertical shear, 9.2 units; combined mechanical, 8.5 units). Overall mortality was 8.6% (lateral compression, 7.0%; anteroposterior, 20.0%, vertical shear, 0%; combined mechanical, 18.0%). The cause of death was associated with the pelvic fracture in less than 50%; no patient with an isolated or vertical shear pelvic injury died. We conclude that the predictive value of our classification system (incorporating appreciation of the causative forces and resulting injury patterns) and our classification-based treatment protocols reduce the morbidity and mortality related to pelvic ring disruption. 相似文献
15.
16.
Polycystic kidney disease is an autosomal dominant disease that may be associated with cystic disease of the liver. In women, the cysts may develop early and be more troublesome than in men. Cystadenocarcinoma of the pancreas is uncommon, comprising 1% of primary pancreatic malignancies. This case report is the first to describe a familial association between polycystic kidney disease and cystadenocarcinoma of the pancreas and liver in the English medical literature. A patient with autosomal dominant polycystic kidney disease (ADPKD) and multiple hepatic cysts developed cystadenocarcinoma of the pancreas with multiple malignant liver cysts. The patient's mother, sister, and niece had ADPKD, and the patient's sister also died of pancreatic cystadenocarcinoma. We believe that the development of these two disease entities in which the primary pathology is cyst formation has a genetic association. (Gastroenterology 1997 Jun;112(6):2104-7) 相似文献
17.
G W Ellison L W Myers M R Mickey M C Graves W W Tourtellotte K Syndulko M I Holevoet-Howson C D Lerner M V Frane P Pettler-Jennings 《Neurology》1989,39(8):1018-1026
Ninety-eight patients with multiple sclerosis (MS) in the chronic progression phase entered a 3-year clinical trial to determine if azathioprine (AZ) alone or with adrenal cortical steroids stabilizes the course of MS. In group AM, the patients took AZ throughout and methylprednisolone (MP) for the first 36 weeks. Group AP received AZ and placebo instead of MP. Group PP took placebos for both drugs. We adjusted the AZ to maintain the total white blood cell count within 3,000 to 4,000/mm3; we gave the MP in a fixed dose "pulse" and alternate-day regimen. The "intent-to-treat" groups had no statistically significant differences in the rates of progression among the 3 treatments. Subgroup analysis suggests that patients in the AM group who completed treatment exactly according to protocol did statistically significantly better than the placebo recipients using the sum of Standard Neurological Examination scores, slightly better using the quantitative neuro-performance tests, but no better using Mickey's Illness Severity Scores or Kurtzke's Disability Status Scale. Also, the AZ-treated groups had half the relapse rate of the placebo-treated group. Adverse reactions to AZ accounted for most withdrawals. Hematologic and hepatic abnormalities were significantly associated with AZ, but serious non-MS abnormalities were uncommon and were equally distributed among the 3 groups. Addition of MP to the AZ slightly improved the efficacy of the treatment, but also increased the adverse effects. The benefits of AZ with or without steroids did not outweigh the risks, and therefore we do not recommend this treatment for patients with chronic progressive MS. 相似文献
18.
19.
Gansky SA Ellison JA Rudy D Bergert N Letendre MA Nelson L Kavanagh C Walsh MM 《Journal of Athletic Training》2005,40(2):76-87
Context: Athletes in the United States are at high risk for using spit (smokeless) tobacco (ST) and incurring its associated adverse health effects.Objective: To examine whether an athletic trainer-directed ST intervention could decrease initiation and promote cessation of ST use among male collegiate baseball athletes.Design: Stratified, cluster-randomized controlled trial.Setting: Fifty-two California colleges.Patients or Other Participant(s): A total of 883 subjects in 27 intervention colleges and 702 subjects in 25 control colleges participated, as did 48 certified athletic trainers.Intervention(s): For college athletic trainers and associated dental professionals, a 3-hour video conference, and for collegiate athletes, an oral cancer screening with feedback and brief counseling during the preseason health screenings, athletic trainer support for cessation, and a peer-led educational baseball team meeting.Main Outcome Measure(s): The subjects' ST use over 1 year was assessed by self-report. At the end of the study, the certified athletic trainers were mailed a survey assessing their tobacco use and perceptions and behavior related to tobacco control in the athletic environment. We used multivariable logistic regression models for clustered responses (generalized estimating equations) to test the difference between groups in ST-use initiation and cessation and to identify significant overall predictors of noninitiation and cessation of ST use.Results: Of the 1585 athletes recruited, 1248 (78.7%) were followed up at 12 months. In addition, 48 of the 52 athletic trainers (92%) responded to the 1-year follow-up survey. The ST-use initiation (incidence) was 5.1% in intervention colleges and 8.4% in control colleges (generalized estimating equation odds ratio = 0.58, 95% confidence interval = 0.35-0.99). Predictors of ST noninitiation were low lifetime tobacco and monthly alcohol use (odds ratio = 1.98, 95% confidence interval = 1.40- 2.82) and athletic trainers' report that the baseball coach supported ST-use prevention activities (odds ratio = 1.43, 95% confidence interval = 1.11-1.83). Although at 1 year, cessation of ST use was relatively high in both groups (36%), we noted no significant difference between the groups (odd ratio = 0.94, 95% confidence interval = 0.70-1.27).Conclusions: The intervention was significantly effective in preventing incident ST use but did not significantly increase cessation beyond that seen in the control group. The latter finding is inconsistent with previous studies and may be explained by spillover of the intervention to control colleges, other anti-tobacco activity in control colleges, and/or the small sample of dependent ST users enrolled in the study. 相似文献
20.