全文获取类型
收费全文 | 3436篇 |
免费 | 243篇 |
国内免费 | 10篇 |
专业分类
耳鼻咽喉 | 13篇 |
儿科学 | 126篇 |
妇产科学 | 64篇 |
基础医学 | 492篇 |
口腔科学 | 65篇 |
临床医学 | 489篇 |
内科学 | 571篇 |
皮肤病学 | 55篇 |
神经病学 | 350篇 |
特种医学 | 263篇 |
外国民族医学 | 1篇 |
外科学 | 336篇 |
综合类 | 41篇 |
一般理论 | 2篇 |
预防医学 | 386篇 |
眼科学 | 44篇 |
药学 | 214篇 |
中国医学 | 2篇 |
肿瘤学 | 175篇 |
出版年
2023年 | 23篇 |
2022年 | 43篇 |
2021年 | 84篇 |
2020年 | 65篇 |
2019年 | 75篇 |
2018年 | 93篇 |
2017年 | 71篇 |
2016年 | 72篇 |
2015年 | 90篇 |
2014年 | 108篇 |
2013年 | 157篇 |
2012年 | 243篇 |
2011年 | 261篇 |
2010年 | 135篇 |
2009年 | 128篇 |
2008年 | 220篇 |
2007年 | 201篇 |
2006年 | 200篇 |
2005年 | 208篇 |
2004年 | 199篇 |
2003年 | 188篇 |
2002年 | 197篇 |
2001年 | 50篇 |
2000年 | 32篇 |
1999年 | 43篇 |
1998年 | 39篇 |
1997年 | 41篇 |
1996年 | 27篇 |
1995年 | 25篇 |
1994年 | 28篇 |
1993年 | 27篇 |
1992年 | 33篇 |
1991年 | 32篇 |
1990年 | 27篇 |
1989年 | 17篇 |
1988年 | 24篇 |
1987年 | 19篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 15篇 |
1983年 | 19篇 |
1981年 | 9篇 |
1978年 | 10篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 8篇 |
1972年 | 8篇 |
1968年 | 7篇 |
1966年 | 5篇 |
排序方式: 共有3689条查询结果,搜索用时 15 毫秒
31.
Research has yet to verify whether children with greater problems, in more restrictive settings such as inpatient units actually receive more protective interventions such as seclusions/restraints than children in less intrusive settings who should have less need. Despite many strong and conflicting opinions about how these interventions should be used, very little is actually known about when and how seclusions/restraints are in fact used. It is unclear what professions use seclusions/restraints most, in what settings, for which children, how consistently, and with what outcomes. The present research found significant variability in use across the continuum of care which could not be attributed to the severity of children's problems or to the restrictiveness of the setting. The two most similar settings differed the most in their use of these procedures. Patterns of utilization are difficult to explain and are a cause for concern because they suggest possible inconsistencies and use which does not depend upon client needs. Use was significantly but only weakly predicted by age and gender of children with younger males being more likely to receive these interventions. The finding that child and youth care workers in the settings studied were the professionals most likely by far to use these procedures, indicates needs for increased worker involvement in both quality assurance and supportive activities that explore potential for burnout and injury associated with high use. 相似文献
32.
Butts K Pauly JM Daniel BL Kee S Norbash AM 《Journal of magnetic resonance imaging : JMRI》1999,9(4):586-595
Several methods were investigated to improve the depiction of biopsy needles in radiofrequency (RF)-refocused magnetic resonance imaging. Distortion correction is performed by the use of view angle tilting (VAT): a gradient is employed on the slice-select axis during readout. Needle conspicuity is increased by offsetting the gradient echo from the spin echo and by inverting the 90 degrees RF pulse slice-select gradient. VAT effectively re-registers in-plane shifts. Since this method changes the projection angle through the slice, some structures appear blurred, while other structures appear sharper. VAT does not correct errors in slice selection. Offsetting the spin echo from the gradient echo increases needle conspicuity but can result in a shift in the apparent location of the needle. Inverting the 90 degrees slice-select gradient effectively increases the needle conspicuity with no shift in the needle location. These methods provide an easy and interactive means to manipulate needle artifacts but should be used cautiously. 相似文献
33.
Association of dialyzer reuse and hospitalization rates among hemodialysis patients in the US 总被引:1,自引:0,他引:1
Feldman HI Bilker WB Hackett M Simmons CW Holmes JH Pauly MV Escarce JJ 《American journal of nephrology》1999,19(6):641-648
OBJECTIVES: To determine if reuse of hemodialyzers is associated with higher rates of hospitalization and their resulting costs among end-stage renal disease (ESRD) patients. METHODS: Noncurrent cohort study of hospitalization rates among 27,264 ESRD patients beginning hemodialysis in the United States in 1986 and 1987. RESULTS: Dialysis in free-standing facilities reprocessing dialyzers was associated with a greater rate of hospitalization than in facilities not reprocessing (relative rate (RR) = 1.08, 95% confidence interval (CI), 1.02-1.14). This higher rate of hospitalization was observed with dialyzer reuse using peracetic/acetic acids (RR = 1.11, CI 1. 04-1.18) and formaldehyde (RR = 1.07, CI 1.00-1.14), but not glutaraldehyde (p = 0.97). There was no difference among hospitalization rates in hospital-based facilities reprocessing dialyzers with any sterilant and those not reprocessing. Hospitalization for causes other than vascular access morbidity in free-standing facilities reusing dialyzers with formaldehyde was not different from hospitalization in facilities not reusing. However, reuse with peracetic/acetic acids was associated with higher rates of hospitalization than formaldehyde (RR = 1.08, CI 1.03-1.15). CONCLUSIONS: Dialysis in free-standing facilities reprocessing dialyzers with peracetic/acetic acids or formaldehyde was associated with greater hospitalization than dialysis without dialyzer reprocessing. This greater hospitalization accounts for a large increment in inpatient stays in the USA. These findings raise important concerns about potentially avoidable morbidity among hemodialysis patients. Copyright Copyright 1999 S. Karger AG, Basel 相似文献
34.
OBJECTIVE: To measure serum leptin concentrations in women with anorexia nervosa (AN) and to identify independent predictors of leptin levels, thereby allowing hormone levels to be modeled using regression analysis. METHODS: A cross-sectional study of 15 AN inpatients and 16 healthy control subjects. Age, height, weight, percent body fat, total caloric intake, fat intake, and fasting plasma leptin levels were recorded. Stepwise forward regression analysis was carried out to identify predictors of leptin levels. RESULTS: Circulating leptin concentrations in AN were 3.5+/-0.5 versus 7.6+/-1.2 ng/ml in control subjects. Percent body fat correlated best with leptin levels in anorexic and control subjects (r =.63; p =.0002), with caloric intake showing only a moderate correlation (r = .47; p = .008). Only percent body fat was a significant predictor of plasma leptin levels in our regression model. DISCUSSION: Leptin levels are proportionately lower in AN as compared to healthy controls. It appears that physiological regulation of plasma levels with respect to percent body fat is maintained in individuals with little body fat. 相似文献
35.
Although the majority of insured Americans receive their health insurance through their employers, some depend on the individual health insurance market. However, with increased criticism of the lack of choice in group coverage and various proposals including subsidies or tax credits to decrease the number of uninsured, the individual market may start to play a larger role. In this paper we conclude that although efficient large-group insurance will appropriately continue to exist, the individual market appears to be improving, in both administrative cost and protection against high premiums associated with high risk. For diverse workers now in small groups with little plan choice, the individual market might become a reasonable alternative. 相似文献
36.
Effects of continuous oral nicotine administration on brain nicotinic receptors and responsiveness to nicotine in C57Bl/6 mice 总被引:4,自引:4,他引:0
The route of drug delivery is an important consideration in studies that evaluate the long-term biobehavioral adaptations
that occur in response to chronic drug administration. Continuous infusions (intravenous or subcutaneous) or intermittent
intraperitoneal (or subcutaneous) injections are the most commonly utilized routes of chronic drug delivery in these studies.
The purpose of the present study was to determine the effects of chronic oral nicotine exposure on sensitivity to nicotine
and brain nicotinic cholinergic receptors in female C57Bl/6 mice. Mice were randomized to different treatment groups that
received 2% saccharin, containing 0–200 μg/ml nicotine (free base). In preliminary experiments, radiotelemetry devices were
implanted in the mice; consumption of the nicotine-containing drinking solution caused a significant increase in home-cage
nocturnal (but not diurnal) activity and also altered circadian alterations in body temperature. Oral nicotine exposure resulted
in dose-related elevations in plasma levels of cotinine, a primary nicotine metabolite. Continuous exposure (30 days) to oral
nicotine (200 μg/ml) resulted in the expression of significant tolerance to the locomotor depressant and hypothermic actions
of acute nicotine challenge. This tolerance was accompanied by a significant increase in brain nicotinic receptor number assessed
by quantitative autoradiography using [3H]-cytisine (α4 nAChr) and [125I]-α-bungarotoxin (α7 nAChr) as radioligands. These results suggest that chronic oral nicotine delivery to female C57Bl/6
mice results in behavioral and biochemical changes that resemble changes that occur following other routes of chronic nicotine
delivery.
Received: 30 January 1998 / Final version: 25 June 1998 相似文献
37.
Paul Kinnaert Olivier Pradier Bernadette Bournonville Claude Habrant Michel Goldman Nancy Van Geertruyden 《Transplant international》1996,9(4):386-391
Anti-CD3 antibodies induce a quick and profound depletion of peripheral blood mononuclear cells (PBMCs) that is not well understood. We studied the effect of OKT3, a mouse monoclonal antibody againts the human CD3 complex, on the in vitro adhesion of human PBMCs to monolayers of fresh and fixed human umbilical vein endothelial cells (HUVECs). OKT3 induced an increased adhesiveness of PBMCs. This phenomenon was blocked with anti-CD18 antibodies, indicating the participation of 2 integrins. As this increased adhesiveness could explain the lymphopenia by adhesion of PBMCs to endothelial cells and their sequestration in some peripheral vascular beds, we studied the effect of anti-CD18 antibodies in vivo on mice injected with 145/2C11, a hamster monoclonal antibody against murine CD3. Mice treated with 145/2C11 presented with a transient granulocytopenia and a sustained reduction in PBMCs. A monoclonal anti-CD18 antibody prevented the granulocytopenia but had no effect the drop in PBMCs. Consequently, the in vivo depletion of PBMCs after administration of an anti-CD3 monoclonal antibody involves CD18-independent mechanisms, while the transient drop in polymorphonuclear cells appears to be CD18-dependent. 相似文献
38.
39.
40.
Objectives: Evaluate the age-dependency of ciliary beat frequency (CBF) in biopsies after ciliogenesis in culture. Study Design: Retrospective analysis of CBF and ciliary ultrastructure in biopsies and after ciliogenesis from 203 individuals, aged 3 months to 74 years. Methods: All patients with successful culture were included. Ciliogenesis was obtained using the sequential monolayer-suspension culture technique for dissociated nasal epithelial cells. CBF was measured using computerized microscope photometry. Secondary ultrastructural abnormalities were evaluated in transmission electron microscopy. Results: There was no correlation between age and CBF, in either the biopsies (7.0 ± 2.6 Hz; n = 113) or after ciliogenesis in culture (8.1 ± 1.3 Hz; n = 203). Even in individuals older than 70 years, CBF was normal in bioptic material (6.7 ± 1.7 Hz) and after ciliogenesis in culture (7.9 ± 1.0 Hz). Also, in individuals less than 1 year of age CBF was normal in biopsies as well as after ciliogenesis. CBF correlated inversely with the percentage of secondary ultrastructural abnormalities in the biopsies as seen with transmission electron microscopy: 8.1 ± 1.8 Hz when ciliary ultrastructure was normal and 3.5 ± 3.3 Hz in cases of severe secondary ciliary dyskinesia. After ciliogenesis in culture, ciliary ultra-structure was always normal, as was CBF. Conclusion: CBF is age independent but correlates with secondary ultrastructural abnormalities. CBF after ciliogenesis in culture is the intrinsic one. 相似文献