全文获取类型
收费全文 | 1464670篇 |
免费 | 117301篇 |
国内免费 | 3585篇 |
专业分类
耳鼻咽喉 | 18884篇 |
儿科学 | 48447篇 |
妇产科学 | 42433篇 |
基础医学 | 208718篇 |
口腔科学 | 38681篇 |
临床医学 | 131412篇 |
内科学 | 296239篇 |
皮肤病学 | 34524篇 |
神经病学 | 122628篇 |
特种医学 | 55048篇 |
外国民族医学 | 464篇 |
外科学 | 215188篇 |
综合类 | 33118篇 |
现状与发展 | 4篇 |
一般理论 | 527篇 |
预防医学 | 115147篇 |
眼科学 | 32355篇 |
药学 | 102746篇 |
1篇 | |
中国医学 | 3483篇 |
肿瘤学 | 85509篇 |
出版年
2021年 | 13145篇 |
2019年 | 13337篇 |
2018年 | 18446篇 |
2017年 | 14182篇 |
2016年 | 15910篇 |
2015年 | 17792篇 |
2014年 | 24905篇 |
2013年 | 36392篇 |
2012年 | 49675篇 |
2011年 | 52296篇 |
2010年 | 30504篇 |
2009年 | 29042篇 |
2008年 | 47660篇 |
2007年 | 50204篇 |
2006年 | 50493篇 |
2005年 | 48701篇 |
2004年 | 46355篇 |
2003年 | 44049篇 |
2002年 | 42336篇 |
2001年 | 73351篇 |
2000年 | 74842篇 |
1999年 | 61942篇 |
1998年 | 17371篇 |
1997年 | 15761篇 |
1996年 | 15814篇 |
1995年 | 15011篇 |
1994年 | 13592篇 |
1993年 | 12756篇 |
1992年 | 46044篇 |
1991年 | 43672篇 |
1990年 | 41645篇 |
1989年 | 39705篇 |
1988年 | 36350篇 |
1987年 | 35496篇 |
1986年 | 32998篇 |
1985年 | 31437篇 |
1984年 | 23976篇 |
1983年 | 20137篇 |
1982年 | 12330篇 |
1981年 | 10887篇 |
1979年 | 20768篇 |
1978年 | 14648篇 |
1977年 | 12156篇 |
1976年 | 11421篇 |
1975年 | 11656篇 |
1974年 | 14057篇 |
1973年 | 13600篇 |
1972年 | 12681篇 |
1971年 | 11523篇 |
1970年 | 10944篇 |
排序方式: 共有10000条查询结果,搜索用时 5 毫秒
921.
New weight guidelines for Americans: justified or injudicious? 总被引:1,自引:0,他引:1
W C Willett M Stampfer J Manson T VanItallie 《The American journal of clinical nutrition》1991,53(5):1102-1103
922.
Human immunodeficiency virus infection in disadvantaged adolescents. Findings from the US Job Corps 总被引:3,自引:0,他引:3
OBJECTIVE--To describe the human immunodeficiency virus (HIV) epidemic among socially and educationally disadvantaged young persons in the United States. DESIGN.-We analyzed demographic and geographic findings from the screening of Job Corps students for antibody to HIV. SETTING--The Job Corps is a federal training program for disadvantaged, out-of-school youth. POPULATION SCREENED--Residential students aged 16 to 21 years who entered the Job Corps from October 1987 through February 1990. MAIN OUTCOME MEASURE--Rates of observed HIV infection in entering students, stratified by demographic and geographic features. RESULTS--Of 137,209 Job Corps students screened, 488 were HIV seropositive (3.6 per 1000), a seroprevalence rate higher than that among military applicants of the same age. Overall seroprevalence was slightly higher in male (3.7 per 1000) than in female (3.2 per 1000) Job Corps students, but among those students aged 16 and 17 years, seroprevalence was higher among females (2.3 per 1000) than among males (1.5 per 1000) (P less than .05). For students aged 16 to 21 years, seroprevalence increased with year of age: 1.8 per 1000 per year for males and 0.7 per 1000 per year for females. Among those aged 21 years, HIV prevalence was 8.9 per 1000. For black and Hispanic students from large Northeastern cities, seroprevalence increased by 4.3 per 1000 per year of age and reached 24.8 per 1000 (one of 40) in students aged 21 years. However, among students from rural areas and small towns, HIV seroprevalence was disproportionately high in the Southeast. Compared with recently described US patients with the acquired immunodeficiency syndrome, HIV-infected students who entered the Job Corps were much more likely to be female. CONCLUSIONS--These findings show that disadvantaged, out-of-school adolescents are at high risk for HIV infection. The screening results identified surprisingly high seroprevalence in the southeastern United States and demonstrated a marked shift in the HIV epidemic to young women. Controlling the HIV epidemic among teenagers must include interventions that will reach adolescents early and outside of the formal educational system. 相似文献
923.
924.
The health care resource allocation debate. Defining our terms 总被引:1,自引:0,他引:1
The problem of health care distribution in the United States demands immediate action. Many different solutions have been proposed to slow rising health care costs and to improve access to care for the poor and uninsured. Debate among proponents of these various proposals might be advanced if a common language were adopted with regard to certain key terms instead of the various meanings currently assigned to these terms. For this reason, we propose and defend the following three definitions: (1) rationing is the societal toleration of inequitable access to health services acknowledged to be necessary by reference to necessary-care guidelines; (2) health care needs are desires for services that have been reasonably well demonstrated to provide significant net benefit for patients with specified clinical conditions; and (3) basic benefit plans are insurance packages that provide for all and only acknowledged health care needs, again by reference to appropriate clinical guidelines. 相似文献
925.
The effect of diaper type and overclothing on fecal contamination in day-care centers 总被引:2,自引:0,他引:2
Fecal coliform contamination of environmental surfaces and hands in the day-care center is common. This study evaluated the effect of two diaper types on fecal contamination. Ten rooms in four day-care centers containing 141 children were studied in a prospective, randomized, crossover study. A total of 2946 samples were cultured during the 9-week study. Fecal coliforms were isolated from 307 inanimate objects (15%), 73 toy balls (46%), and 131 hands (17%). The number of contaminated inanimate objects was significantly less in rooms where paper diapers were worn when compared with that in rooms where double cloth diapers with plastic overpants were worn and in rooms where clothes were worn over diapers. Inanimate object cultures had more contamination in rooms in which diarrhea had occurred. Containment of feces by overclothes and diaper type may be important in decreasing transmission of enteric pathogens in day-care environments. 相似文献
926.
C C Linnemann C Cannon M DeRonde B Lanphear 《Infection control and hospital epidemiology》1991,12(4):214-219
OBJECTIVE: To evaluate the effect of infection control programs on reported needlestick injuries in a general hospital. DESIGN: Surveillance of all reported needlestick injuries at the University of Cincinnati Hospital was maintained by the infection control department for five years, from 1985 through 1989. Data on individual workers were collected, tabulated on a monthly basis, and reviewed continually to monitor trends in injuries. During this time, the effects of each of three new infection control programs on reported injuries were evaluated sequentially. SETTING: A 700-bed general hospital that serves as the main teaching hospital of the University of Cincinnati. PARTICIPANTS: All employees of University Hospital who reported to personnel health for management of needlestick injuries. INTERVENTIONS: In 1986, an educational program to prevent injuries was initiated and continued throughout the surveillance period. In 1987, rigid sharps disposal containers were placed in all hospital rooms. In 1988, universal precautions were introduced with an intensive inservice. RESULTS: Surveillance identified 1,602 needlestick injuries (320/year) or 104/1,000/year. After the educational program began, reported injuries increased rather than decreased, and this was attributed to increased reporting. Subsequently, after installation of the new disposal containers, reported injuries returned to the levels seen prior to the educational program, but recapping injuries showed a significant decrease from 63/year to 30, or 20/1,000/year to 10. This decrease was observed in nurses but not in other healthcare workers. After universal precautions were instituted, total injuries increased slightly, but recapping injuries remained at 50% of the levels reported prior to the use of rigid sharps disposal containers. CONCLUSIONS: The three infection control programs failed to produce a major reduction in reported needlestick injuries, except for a decrease in recapping injuries associated with the placement of rigid sharps disposal containers in all patient rooms. These observations indicate that new approaches are needed to reduce needlestick injuries. 相似文献
927.
A Basile-Filho A C Campos S C Esteves S Bordin M Mantovani 《Nutrition (Burbank, Los Angeles County, Calif.)》1991,7(4):280-282
Several studies have reported that the heart is severely affected by chronic malnutrition. However, the influence of these alterations on cardiac function remains unclear. The aim of this study was to evaluate the effects of subacute starvation on the heart chronotropic response to a beta-adrenergic agonist (isoproterenol). Twelve rats were fed rat chow ad libitum or a 50%-restricted diet for 17 days. The rats were killed, the right atrium was isolated and incubated, and in vitro spontaneous cardiac contractions and frequency were registered. Cumulative doses of isoproterenol were added to the solution until maximal cardiac frequency was achieved. A deficit of 25% in the weight gain was observed in study rats compared with controls (92.6 +/- 10.2 vs. 113.8 +/- 19.2 g, p less than 0.05). Mean daily food intake was 4.8 +/- 0.1 and 9.8 +/- 0.5 g/day for semistarved and control rats, respectively. The in vitro cardiac frequency of the semistarved rats was similar to that of controls (290 +/- 15 and 305 +/- 23 beats/min, respectively, NS). However, when isoproterenol was added to the solution, maximal cardiac frequency of the semistarved rats (435 +/- 51 beats/min) was lower than that of control rats (508 +/- 34 beats/min, p less than 0.005). These findings suggest that subacute starvation may alter the cardiac response to beta-adrenergic agonists. 相似文献
928.
E W Richards M Abu Khaled C L Watkins C L Long 《Nutrition (Burbank, Los Angeles County, Calif.)》1991,7(5):344-346
Nuclear magnetic resonance (NMR) spectroscopy has been reported as an alternative method for quantitating deuterium oxide concentrations in the evaluation of total-body-water in humans. However, the presence of dissolved plasma proteins results in an underestimation of deuterium NMR (2H-NMR) intensity ratios, thereby causing an overestimation (5-6%) of total-body-water (TBW) values determined from nonsublimed patient plasma samples. We demonstrate that plasma samples must be corrected for the volume percentage of water in plasma. Correction of initial 2H-NMR intensity ratios with a factor of 0.93 results in intensity ratios comparable to those determined from plasma samples subjected to vacuum sublimation to remove all plasma solutes. 相似文献
929.
930.