全文获取类型
收费全文 | 3640篇 |
免费 | 328篇 |
国内免费 | 40篇 |
专业分类
耳鼻咽喉 | 43篇 |
儿科学 | 129篇 |
妇产科学 | 118篇 |
基础医学 | 394篇 |
口腔科学 | 97篇 |
临床医学 | 393篇 |
内科学 | 785篇 |
皮肤病学 | 126篇 |
神经病学 | 197篇 |
特种医学 | 260篇 |
外科学 | 402篇 |
综合类 | 113篇 |
一般理论 | 2篇 |
预防医学 | 334篇 |
眼科学 | 198篇 |
药学 | 268篇 |
中国医学 | 3篇 |
肿瘤学 | 146篇 |
出版年
2021年 | 39篇 |
2020年 | 22篇 |
2019年 | 42篇 |
2018年 | 37篇 |
2017年 | 38篇 |
2016年 | 38篇 |
2015年 | 60篇 |
2014年 | 70篇 |
2013年 | 147篇 |
2012年 | 131篇 |
2011年 | 150篇 |
2010年 | 119篇 |
2009年 | 126篇 |
2008年 | 134篇 |
2007年 | 132篇 |
2006年 | 141篇 |
2005年 | 118篇 |
2004年 | 116篇 |
2003年 | 84篇 |
2002年 | 106篇 |
2001年 | 87篇 |
2000年 | 89篇 |
1999年 | 96篇 |
1998年 | 100篇 |
1997年 | 105篇 |
1996年 | 101篇 |
1995年 | 68篇 |
1994年 | 88篇 |
1993年 | 67篇 |
1992年 | 66篇 |
1991年 | 59篇 |
1990年 | 54篇 |
1989年 | 85篇 |
1988年 | 74篇 |
1987年 | 66篇 |
1986年 | 73篇 |
1985年 | 86篇 |
1984年 | 59篇 |
1983年 | 32篇 |
1982年 | 43篇 |
1981年 | 37篇 |
1980年 | 26篇 |
1979年 | 54篇 |
1978年 | 36篇 |
1977年 | 31篇 |
1976年 | 25篇 |
1974年 | 21篇 |
1973年 | 32篇 |
1972年 | 34篇 |
1969年 | 24篇 |
排序方式: 共有4008条查询结果,搜索用时 578 毫秒
81.
PC NG KW SO TF FOK MC YAM MY WONG W WONG 《Journal of paediatrics and child health》1997,33(4):324-328
Objectives: A prospective study comparing the efficiacy and side-effects of oral sulindac with intravenous indomethacin in clinically stable preterm infants (<1750 g) requiring non-invasive closure of haemodynamically significant patent ductus arteriosus.
Methodology: As maturity and birthweight are the two major determinants of ductal closure, infants were matched as closely as possible for these parameters. An eligible patient was first assigned to the sulindac group and a subsequent patient with similar gestational age (± 1 week) and birthweight (±100 g) to the previously recruited infant would automatically receive indomethacin. A total of eight infants were enrolled in each group.
Results: The ductus arteriosus was successfully closed in all eight infants receiving indomethacin, and in seven of eight infants receiving sulindac. No significant differences were found with regards to the ductal size between the two groups at diagnosis or on each of the consecutive days of treatment ( P >0.25). More renal adverse effects were encountered in the indomethacin group. Significant differences in changes from baseline value for urine output, plasma sodium, urea and creatinine concentrations were noted at 24, 48 and 72 h after commencement of treatment between the two groups ( P <0.05). All the parameters returned to normal or pre-treatment levels 48 h after stopping therapy. Unexpectedly, severe gastrointestinal complications were encountered in the sulindac group.
Conclusions: Sulindac is capable of promoting ductal constriction in clinically stable preterm infants without compromising the renal function. The spectrum of gastrointestinal complications observed in sulindac treated infants were similar to those described for indomethacin. The use of sulindac for ductal closure in the preterm infant should remain experimental. 相似文献
Methodology: As maturity and birthweight are the two major determinants of ductal closure, infants were matched as closely as possible for these parameters. An eligible patient was first assigned to the sulindac group and a subsequent patient with similar gestational age (± 1 week) and birthweight (±100 g) to the previously recruited infant would automatically receive indomethacin. A total of eight infants were enrolled in each group.
Results: The ductus arteriosus was successfully closed in all eight infants receiving indomethacin, and in seven of eight infants receiving sulindac. No significant differences were found with regards to the ductal size between the two groups at diagnosis or on each of the consecutive days of treatment ( P >0.25). More renal adverse effects were encountered in the indomethacin group. Significant differences in changes from baseline value for urine output, plasma sodium, urea and creatinine concentrations were noted at 24, 48 and 72 h after commencement of treatment between the two groups ( P <0.05). All the parameters returned to normal or pre-treatment levels 48 h after stopping therapy. Unexpectedly, severe gastrointestinal complications were encountered in the sulindac group.
Conclusions: Sulindac is capable of promoting ductal constriction in clinically stable preterm infants without compromising the renal function. The spectrum of gastrointestinal complications observed in sulindac treated infants were similar to those described for indomethacin. The use of sulindac for ductal closure in the preterm infant should remain experimental. 相似文献
82.
83.
Aberrant crypt focus promotion and glucose intolerance: correlation in the rat across diets differing in fat, n-3 fatty acids and energy 总被引:1,自引:0,他引:1
Koohestani N; Chia MC; Pham NA; Tran TT; Minkin S; Wolever TM; Bruce WR 《Carcinogenesis》1998,19(9):1679-1684
McKeown-Eyssen (Cancer Epidemiol. Biomarkers Prevent., 3, 687-695, 1994)
and Giovannucci (Cancer Causes Control, 6, 164-179, 1995), noting the
striking similarity in lifestyle risk factors for colorectal cancer and
insulin resistance, proposed that the hyperinsulinemia, glycemia and
hypertriglyceridemia associated with insulin resistance promotes colon
cancer. To compare the effect of diet on colon cancer promotion and insulin
resistance in the F344 rat, we assessed the effect of fat, n-3 fatty acids
and energy in pairwise comparisons on average size of aberrant crypt foci
(ACF) and on glucose intolerance in the same animals in a single
experiment. Diets high in fat and energy increased and diets with increased
n-3 fatty acids and calorie restriction decreased both ACF growth and
glucose intolerance compared with control diets. The measures of promotion
of colon cancer and insulin resistance were strongly correlated (n = 98, r
= 0.67, P < 0.001). In addition, both were highly correlated with daily
energy intake (r = 0.62 and 0.66) and were also correlated with basal
(post-prandial) insulin, glucose and triglycerides (r = 0.31-0.53, P <
0.01). We concluded that ACF growth and glucose intolerance are correlated
for a wide range of diets and that increased circulating energy (glucose
and triglycerides) may lead to both colon cancer promotion and insulin
resistance.
相似文献
84.
Bolontrade MF; Stern MC; Binder RL; Zenklusen JC; Gimenez-Conti IB; Conti CJ 《Carcinogenesis》1998,19(12):2107-2113
In this study we have analyzed the vascular response induced in the two-
stage carcinogenesis model in SENCAR mice. The role of angiogenesis has not
been explored in this model, which is the paradigm of multistage
carcinogenesis and a model for neoplastic lesions derived from exophytic
premalignant lesions (e.g. colon carcinoma, bladder papilloma). We
investigated if angiogenesis is involved in the formation of papillomas and
in the progression from papilloma to carcinoma. To this end we analyzed the
vasculature of normal and hyperplastic skin, focal epidermal hyperplasias
that are precursors of papillomas, papillomas at different stages and
squamous cell carcinomas. We also analyzed the vascularization of
papillomas induced in two strains of mice that differ in their
susceptibility to malignant progression. We show here that angiogenesis is
turned on in the earliest stages of papilloma formation. In late stages,
regardless of state of progression, the predominant response is an increase
in the size of blood vessels. Thus, in the SENCAR mouse model,
representative of exophytic tumors, the angiogenesis switch is a very early
event, probably mechanistically related to the development of the primarily
exophytic lesions. Therefore, the density of blood vessels cannot be used
as a predictor of malignant progression in this model.
相似文献
85.
86.
Recombinant human interleukin-11 prevents mucosal atrophy and bowel shortening in the defunctionalized intestine 总被引:6,自引:0,他引:6
Dickinson EC Tuncer R Nadler EP Koltuksuz U Boyle P Alber SM Watkins SC Ford HR 《Journal of pediatric surgery》2000,35(7):1079-1083
BACKGROUND: Mucosal atrophy and bowel shortening are the hallmark of proximal intestinal diversion for extensive necrotizing enterocolitis (NEC) or Thiry-Vella fistulas (TVF), in which the ends of a defunctionalized loop of intestine are exteriorized as stomas. Recombinant human interleukin-11 (rhIL-11) is a pleiotropic cytokine that promotes epithelial regeneration and enhances adaptation after bowel resection. The authors hypothesized that rhIL-11 may prevent mucosal atrophy and bowel shortening in rats with TVF METHODS: After creation of ileal TVF, Sprague-Dawley rats were selected randomly to receive either rhIL-11 or equal volume of 0.1% bovine serum albumin (BSA) subcutaneously daily. On day 14, the TVF were excised and examined morphologically. Enterocyte apoptosis was measured using the TUNEL assay. Mucosal DNA and protein content were measured. RESULTS: Administration of rhIL-11 resulted in a significantly greater weight gain and less shortening of TVF than BSA treatment. TVF from the rhIL-11-treated group showed evidence of hyperplasia and hypertrophy and increased crypt to villus ratio. The BSA group had substantial mucosal atrophy. There was a qualitative decrease in the incidence of apoptosis in the rhIL-11 group. CONCLUSIONS: Recombinant human IL-11 prevents mucosal atrophy and shortening of defunctionalized intestinal loops. It may help reduce the incidence of short gut syndrome in infants with extensive NEC. 相似文献
87.
Lower rates of emergency department injury visits among Latino children in the USA: no association with health insurance. 下载免费PDF全文
BACKGROUND AND OBJECTIVE: Latino children have lower rates of injury visits to emergency departments (EDs) than non-Latino white and African American children. This study tests the hypothesis that this difference reflects health insurance status. DESIGN: Secondary analysis. Patients/ SETTING: Children under 19 years of age visiting EDs in the USA, sampled in the National Hospital Ambulatory Medical Care Survey of EDs (NHAMCS-ED) from 1997 to 2001. MAIN OUTCOME MEASURES: Rates of ED injury visits; ED injury visit rates by race/ethnicity stratified by health insurance and adjusted for other covariates; subtypes of injury visits; and procedures and hospital admissions by race/ethnicity. RESULTS: Injuries accounted for >56 million, or 40.5%, of total ED visits among pediatric patients. Injury visits occurred at lower rates for Latino children (9.9 per 100 person years) than non-Latino white and African American children (16.2 and 18.3, respectively), although total ED visit rates were similar. Regardless of health insurance status, Latino children had lower rates of injury visits than non-Latino white and African American children. Latino children had lower rates of the three major subtypes of injury visits (sports, accidental falls, struck by/between objects). Latino children had similar rates of procedures and hospital admissions to non-Latino white children. CONCLUSIONS: Irrespective of their insurance status, Latino children have lower rates of ED injury visits in the USA than non-Latino white children. Possible reasons for this difference include different healthcare seeking behavior or different injury patterns by race/ethnicity, but not differences in health insurance status or barriers to accessing ED care. 相似文献
88.
Tamara D Simon Stephanie Phibbs L Miriam Dickinson Allison Kempe John F Steiner Arthur J Davidson Simon J Hambidge 《Ambulatory Pediatrics》2006,6(6):318-325
OBJECTIVE: To describe clinician delivery of injury prevention anticipatory guidance and injury visits in a birth cohort, and to describe the association of injury prevention anticipatory guidance with subsequent injury visits. METHODS: We performed a prospective cohort study of 2610 infants born from July 1, 1998 to June 30, 1999, at an urban safety-net hospital and seen subsequently for well child care (WCC, visits = 10558) and/or injury by 16 months of age. Injury guidance was defined as the proportion of recommended injury prevention anticipatory guidance items delivered to those expected, given the WCC visits the child attended. The outcome was a first injury visit to a clinic, emergency department, or hospital. RESULTS: The injury prevention items most discussed were car seats (84%-95% of all WCC visits) and rolling over at the 2-month WCC visit (80%). Other items were addressed at 36%-69% of visits. A total of 1931 (74%) of children received > or = 50% expected injury guidance. A total of 277 children (11%) had an injury visit, primarily for minor injuries. In unadjusted analysis, children receiving < 25% expected injury guidance were more likely to have a subsequent injury visit (unadjusted odds ratio 6.2; 95% confidence interval [95% CI] 3.2-9.7). In adjusted analysis, children who received < 25% and 25%-49% expected injury guidance were more likely to have a subsequent injury visits (adjusted odds ratio [AOR] 6.6; 95% CI 3.8-11.2; and AOR 2.9, 95% CI 2.0-4.3, respectively). CONCLUSIONS: Disadvantaged children whose families received less injury guidance than other children in their cohort were more likely to have a subsequent injury visit. Further studies are needed to determine whether increased injury prevention counseling reduces injury visits. 相似文献
89.
BACKGROUND: The mechanisms by which the inhalational general anesthetics isoflurane and xenon exert their effects are unknown. Moreover, there have been surprisingly few quantitative studies of the effects of these agents on central synapses, with virtually no information available regarding the actions of xenon. METHODS: The actions of isoflurane and xenon on gamma-aminobutyric acid-mediated (GABAergic) and glutamatergic synapses were investigated using voltage-clamp techniques on autaptic cultures of rat hippocampal neurons, a preparation that avoids the confounding effects of complex neuronal networks. RESULTS: Isoflurane exerts its greatest effects on GABAergic synapses, causing a marked increase in total charge transfer (by approximately 70% at minimum alveolar concentration) through the inhibitory postsynaptic current. This effect is entirely mediated by an increase in the slow component of the inhibitory postsynaptic current. At glutamatergic synapses, isoflurane has smaller effects, but it nonetheless significantly reduces the total charge transfer (by approximately 30% at minimum alveolar concentration) through the excitatory postsynaptic current, with the N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptor-mediated components being roughly equally sensitive. Xenon has no measurable effect on GABAergic inhibitory postsynaptic currents or on currents evoked by exogenous application of GABA, but it substantially inhibits total charge transfer (by approximately 60% at minimum alveolar concentration) through the excitatory postsynaptic current. Xenon selectively inhibits the NMDA receptor-mediated component of the current but has little effect on the AMPA/kainate receptor-mediated component. CONCLUSIONS: For both isoflurane and xenon, the most important targets appear to be postsynaptic. The authors' results show that isoflurane and xenon have very different effects on GABAergic and glutamatergic synaptic transmission, and this may account for their differing pharmacologic profiles. 相似文献
90.
Stereoselective loss of righting reflex in rats by isoflurane 总被引:8,自引:0,他引:8
BACKGROUND: Although it is accepted widely that optically active intravenous general anesthetics produce stereoselective effects in animals, the situation regarding volatile agents is confused. Conventional studies with scarce isoflurane enantiomers have been limited to small numbers of animals and produced conflicting results. By injecting these volatile enantiomers intravenously, however, it is possible to study large numbers of animals and obtain reliable results that can help to identify the molecular targets for isoflurane. METHODS: Pure isoflurane enantiomers were administered intravenously to rats after solubilization in a lipid emulsion. The ability of each enantiomer to produce a loss of righting reflex was determined as a function of dose, and quantal dose-response curves were constructed. In addition, sleep times were recorded with each enantiomer. Chiral gas chromatography was used to measure relative enantiomer concentrations in the brains of rats injected with racemic isoflurane. RESULTS: The S(+)-enantiomer was 40 +/- 8% more potent than the R(-)-enantiomer at producing a loss of righting reflex. The S(+)-enantiomer induced longer sleep times (by about 50%) than did the R(-)-enantiomer. Rats anesthetized by a dose of racemic isoflurane sufficient to achieve a half-maximal effect had essentially identical brain concentrations of the two enantiomers. CONCLUSIONS: The S(+)-enantiomer of the general anesthetic isoflurane is significantly (P < 0.001) more potent than the R(-)-enantiomer at causing a loss of righting reflex in rats. This confirms the view that isoflurane acts by binding to chiral sites. The observed degree of stereoselectivity provides a useful guide for ascertaining from in vitro experiments which molecular targets are most likely to play major roles in the loss of righting reflex caused by isoflurane. 相似文献