全文获取类型
收费全文 | 2696篇 |
免费 | 206篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 86篇 |
妇产科学 | 103篇 |
基础医学 | 290篇 |
口腔科学 | 39篇 |
临床医学 | 234篇 |
内科学 | 731篇 |
皮肤病学 | 36篇 |
神经病学 | 153篇 |
特种医学 | 305篇 |
外科学 | 178篇 |
综合类 | 68篇 |
一般理论 | 3篇 |
预防医学 | 243篇 |
眼科学 | 25篇 |
药学 | 118篇 |
1篇 | |
肿瘤学 | 309篇 |
出版年
2021年 | 34篇 |
2020年 | 16篇 |
2019年 | 35篇 |
2018年 | 42篇 |
2017年 | 25篇 |
2016年 | 30篇 |
2015年 | 39篇 |
2014年 | 53篇 |
2013年 | 61篇 |
2012年 | 124篇 |
2011年 | 143篇 |
2010年 | 63篇 |
2009年 | 59篇 |
2008年 | 124篇 |
2007年 | 140篇 |
2006年 | 109篇 |
2005年 | 98篇 |
2004年 | 95篇 |
2003年 | 91篇 |
2002年 | 76篇 |
2001年 | 76篇 |
2000年 | 65篇 |
1999年 | 69篇 |
1998年 | 54篇 |
1997年 | 51篇 |
1996年 | 35篇 |
1995年 | 35篇 |
1994年 | 34篇 |
1993年 | 46篇 |
1992年 | 61篇 |
1991年 | 58篇 |
1990年 | 63篇 |
1989年 | 66篇 |
1988年 | 63篇 |
1987年 | 89篇 |
1986年 | 73篇 |
1985年 | 60篇 |
1984年 | 51篇 |
1983年 | 47篇 |
1982年 | 29篇 |
1981年 | 27篇 |
1980年 | 25篇 |
1979年 | 22篇 |
1978年 | 22篇 |
1977年 | 21篇 |
1976年 | 19篇 |
1975年 | 14篇 |
1974年 | 27篇 |
1973年 | 21篇 |
1972年 | 13篇 |
排序方式: 共有2924条查询结果,搜索用时 15 毫秒
41.
G B Habib J Heibig S A Forman B G Brown R Roberts M L Terrin R Bolli 《Circulation》1991,83(3):739-746
BACKGROUND. The influence of coronary collateral vessels on infarct size in humans remains controversial, partly because no previous study has examined the impact of collaterals present at the onset of acute myocardial infarction on infarct size. METHODS AND RESULTS. The present study used the data base of the Thrombolysis in Myocardial Infarction (TIMI) Phase I trial to correlate the presence or absence of angiographically documented collaterals in the initial hours of myocardial infarct evolution with the size of the infarct as assessed by serial measurements of serum creatine kinase (CK). To avoid the confounding effects of reperfusion on enzymatic estimates of infarct size, this report is limited to those 125 patients who failed to recanalize at 90 minutes after administration of tissue plasminogen activator or streptokinase. Patients with angiographically documented collaterals (group A, n = 51) had significantly lower values of peak serum CK than patients without collaterals (group B, n = 74) (1,877 +/- 216 versus 2,661 +/- 212 IU/l, respectively [mean +/- SEM], p = 0.004). Similarly, CK-derived infarct size estimates were significantly lower in group A than in group B (20.6 +/- 2.5 versus 31.4 +/- 2.8 CK gram equivalents, p = 0.001). The infarct size observed in patients with collaterals was less for anterior infarctions as well as for infarctions of other locations; thus, the beneficial effects of collaterals were independent of the site of the infarct. In 65 of the 125 patients who failed to reperfuse, left ventricular ejection fraction (LVEF) was assessed by contrast ventriculography both at initial cardiac catheterization (before thrombolytic therapy) and at hospital discharge. Among the patients who had both studies, global LVEF tended to increase from pretreatment to hospital discharge in group A (from 50.6 +/- 1.8% to 53.4 +/- 1.8%, p = 0.10) but decreased in group B patients (from 50.3 +/- 1.8% to 47.8 +/- 1.7%, p = 0.02). At hospital discharge, global LVEF was greater in patients with coronary collaterals (53.5 +/- 1.7% versus 49.6 +/- 1.7%, p = 0.01). CONCLUSIONS. The results demonstrate that, in patients in whom thrombolytic therapy fails to induce reperfusion, the presence of coronary collateral vessels at the onset of myocardial infarction is associated with limitation of infarct size as assessed enzymatically and with improved ventricular function on discharge as assessed by LVEF. 相似文献
42.
Incidence, predictors at admission, and impact of worsening renal function among patients hospitalized with heart failure 总被引:10,自引:0,他引:10
Forman DE Butler J Wang Y Abraham WT O'Connor CM Gottlieb SS Loh E Massie BM Rich MW Stevenson LW Young JB Krumholz HM 《Journal of the American College of Cardiology》2004,43(1):61-67
OBJECTIVES: The goal of this study was to determine the prevalence of worsening renal function (WRF) among hospitalized heart failure (HF) patients, clinical predictors of WRF, and hospital outcomes associated with WRF. BACKGROUND: Impaired renal function is associated with poor outcomes among chronic HF patients. METHODS: Chart reviews were performed on 1,004 consecutive patients admitted for a primary diagnosis of HF from 11 geographically diverse hospitals. Cox regression model analysis was used to identify independent predictors for WRF, defined as a rise in serum creatinine of >0.3 mg/dl (26.5 micromol/l). Bivariate analysis was used to determine associations of development of WRF with outcomes (in-hospital death, in-hospital complications, and length of stay). RESULTS: Among 1,004 HF patients studied, WRF developed in 27%. In the majority of cases, WRF occurred within three days of admission. History of HF or diabetes mellitus, admission creatinine > or =1.5 mg/dl (132.6 micromol/l), and systolic blood pressure >160 mm Hg were independently associated with higher risk of WRF. A point score based on these characteristics and their relative risk ratios predicted those at risk for WRF. Hospital deaths (adjusted risk ratio [ARR] 7.5; 95% confidence intervals [CI] 2.9, 19.3), complications (ARR 2.1; CI 1.5, 3.0), and length of hospitalizations >10 days (ARR 3.2, CI 2.2, 4.9) were greater among patients with WRF. CONCLUSIONS: Worsening renal function occurs frequently among hospitalized HF patients and is associated with significantly worse outcomes. Clinical characteristics available at hospital admission can be used to identify patients at increased risk for developing WRF. 相似文献
43.
The efficacy of proton pump inhibitors in nonulcer dyspepsia: a systematic review and economic analysis 总被引:10,自引:0,他引:10
BACKGROUND AND AIMS: The evidence that proton pump inhibitor (PPI) therapy affects symptoms of nonulcer dyspepsia is conflicting. We conducted a systematic review to evaluate whether PPI therapy had any effect in nonulcer dyspepsia and constructed a health economic model to assess the cost-effectiveness of this approach. METHODS: Electronic searches were performed using the Cochrane Controlled Trials Register, MEDLINE, EMBASE, CINAHL, and SIGLE until September 2002. Dyspepsia outcomes were dichotomized into cured/improved versus same/worse. Results were incorporated into a Markov model comparing health service costs and benefits of PPI with antacid therapy over 1 year. RESULTS: Eight trials were identified that compared PPI therapy with placebo in 3293 patients. The relative risk of remaining dyspeptic with PPI therapy versus placebo was .86 (95% confidence interval, .78-.95; P = .003, random-effects model) with a number needed to treat of 9 (95% confidence interval, 5-25). There was statistically significant heterogeneity between trials (heterogeneity chi(2) = 30.05; df = 7; P < .001). The PPI strategy would cost an extra US dollar 278/month free from dyspepsia if the drug cost US dollar 90/month. If a generic price of US dollar 19.99 is used, then a PPI strategy costs an extra US dollar 57/month free from dyspepsia. A third-party payer would be 95% certain that PPI therapy would be cost-effective, provided they were willing to pay US dollar 94/month free from dyspepsia. CONCLUSIONS: PPI therapy may be a cost-effective therapy in nonulcer dyspepsia, provided generic prices are used. 相似文献
44.
The association between hepatitis C infection and survival after orthotopic liver transplantation 总被引:36,自引:0,他引:36
BACKGROUND & AIMS: The effect of hepatitis C viral (HCV) infection on patient and allograft survival after orthotopic liver transplantation is controversial. Hepatitis C recurrence after transplant is inevitable, but studies to date have not found a survival difference between recipients with and without HCV. METHODS: Using data from the United Network for Organ Sharing, we performed a retrospective cohort study of 11,036 patients who underwent 11,791 liver transplants between 1992 and 1998. The hazard rates of patient and allograft survival for patients who were HCV-positive as compared with patients who were HCV-negative were assessed by proportional-hazards analysis, with adjustment for potential confounding variables, including donor, recipient, and transplant center characteristics. RESULTS: Liver transplantation in HCV-positive recipients was associated with an increased rate of death (hazard ratio, 1.23; 95% confidence interval [CI], 1.12-1.35) and allograft failure (hazard ratio, 1.30; 95% CI, 1.21-1.39), as compared with transplantation in HCV-negative recipients. This reduction in survival persisted after adjusting for potential confounders. There was an interaction between HCV and sex (P < 0.001) with the effect of HCV on survival being most pronounced in female recipients (patient survival hazard ratio, 1.56; 95% CI, 1.35-1.81; allograft survival hazard ratio, 1.51; 95% CI, 1.34-1.70). CONCLUSIONS: HCV infection significantly impairs patient and allograft survival after liver transplantation. 相似文献
45.
Stacy Schantz Wilkins PhD Rebecca J. Melrose PhD Katherine S. Hall PhD Erin Blanchard MS Steven C. Castle MD Teresa Kopp PT MBA Leslie I. Katzel MD PhD Alice Holder MHS PT Neil Alexander MD Michelle K.S. McDonald BA OT Arti Tayade MD CMD HMDC Daniel E. Forman MD Lauren M. Abbate MD PhD Rebekah Harris PT DPT PhDc Willy M. Valencia MD Miriam C. Morey PhD Cathy C. Lee MD 《Journal of the American Geriatrics Society》2021,69(4):1045-1050
46.
Activation and expansion in culture with rIL-2 of peripheral blood (PB) and/or bone marrow (BM) specimens derived from children with ALL and ANLL, with active disease (AP) and in remission were studied (RP). Baseline NK cytolytic activity from AP was found to be depressed, whereas RP-derived cells had normal NK activity, as assayed against K562 targets. Culture in rIL-2 significantly enhanced the NK activity of both AP- and RP-derived cells and generated LAK activity, as assayed by 4-hour 51Cr release, against NK-resistant Raji cell line and against fresh, allogeneic, and autologous tumor cells. Lytic activity against fresh, cryopreserved leukemia blasts was of lower than that found against cell lines. In three patients higher lytic activity against autologous than against allogeneic blasts was demonstrated. Expansion in culture with rIL-2 varied from twofold to 120-fold. rIL-2 activation and expansion was better in RP than in AP. The predominant phenotype of activated cells, as determined by flow cytometry, was [mean % (SD)]: CD3- = 54 (12), CD8+ = 55 (17), and NKH1+ = 26 (7). The consistently high level of CD8+ cells was accompanied by very low levels of CD4+ cells: mean = 11% (14). Double-marker analysis showed mean of 33% (10) for CD3+/NKH1+ cells and mean = 32 (11) for CD8+/NKH1+ cells, implying that these populations were overlapping. Kinetics of expression of cell surface markers during 2 to 3 weeks in culture showed that CD8+ and NKH1+ enrichment occurred during the first week and lasted for up to 4 weeks, whereas CD4+ expression decreased after the second week. A significant decrease in the expression of IL-2 receptors (CD25) was observed from the second week of culture. This study shows the feasibility of in vitro generation of killer cells from PB and BM of pediatric leukemia patients. 相似文献
47.
Patricia Schram Sion K. Harris Shari Van Hook Sara Forman Enrico Mezzacappa Roman Pavlyuk 《Substance Abuse》2015,36(3):332-338
Background: Screening, brief intervention, and referral to treatment (SBIRT) is recommended as part of routine health care for adolescents as well as adults. In an effort to promote universal SBIRT, the Substance Abuse and Mental Health Services Administration awarded funding to residency programs to develop and implement SBIRT education and training. Our project focused on creating scientifically based, developmentally appropriate strategies and teaching materials for the adolescent age range. This paper describes curriculum development and implementation and presents evaluation data. Methods: Pediatric and child psychiatry residents were trained. The training consisted of 4 activities: (1) case-based teaching modules, (2) role-play of motivational interviewing and brief interventions, (3) mock interviews with trained adolescents, and (4) supervised “hands-on” screening and brief interventions. Main outcome measures included trainee satisfaction, and SBIRT knowledge, perceived self-efficacy, and self- and observer report of use of the SBIRT algorithm. Results: Among 150 total participants completing the SBIRT training modules, nearly all (92.3%) were satisfied/very satisfied with the training modules. Knowledge accuracy immediately post training was high, but declined significantly by the end of the first residency year, with little change across subsequent years of residency. Confidence ratings also declined over time. Use of the SBIRT algorithm during the Adolescent Medicine rotation was high according to trainee self- and faculty observer report. Conclusions: We found evidence of training satisfaction, increased confidence in talking to adolescents about substance use, and widespread use of recommended practices immediately following training. Use of a highly structured algorithm to guide practice, and simple, highly structured brief interventions was a successful training approach, as residents self-reported accurate use of the SBIRT algorithm immediately after training. Knowledge and self-confidence declined over time. It is possible that “booster” sessions and ongoing opportunities to review materials could help residents retain knowledge and skills. 相似文献
48.
The prognostic importance of different definitions of worsening renal function in congestive heart failure 总被引:13,自引:0,他引:13
Gottlieb SS Abraham W Butler J Forman DE Loh E Massie BM O'connor CM Rich MW Stevenson LW Young J Krumholz HM 《Journal of cardiac failure》2002,8(3):136-141
BACKGROUND: Worsening renal function in patients hospitalized for heart failure portends a poor prognosis. However, criteria used to define worsening renal function are arbitrary, and the implications of different definitions remain unclear. We therefore compared the prognostic importance of various definitions of worsening renal function in 1,002 patients hospitalized for congestive heart failure (CHF). METHODS AND RESULTS: The patient population was 49% female, aged 67 +/- 15 years. Twenty-three percent had a prior history of renal failure, 73% had known depressed ejection fraction, and 63% had known CHF. On admission to the hospital, 47% were receiving ACE inhibitors, 22% beta-blockers, 70% diuretics and 6% NAID's. 72% developed increased serum creatinine during the hospitalization, with 20% developing an increase of > or = 0.5 mg/dL. Worsening renal function predicted both in-hospital mortality and length of stay > 10 days. Even an increased creatinine of 0.1 mg/dL was associated with worse outcome. Sensitivity for death decreased from 92% to 65% as the threshold for increased creatinine was raised from 0.1 to 0.5 mg/dL, with specificity increasing from 28% to 81%. At a threshold of a 0.3 mg/dL increase, sensitivity was 81% and specificity was 62% for death and 64% and 65% for length of stay >10 days. Adding a requirement of final creatinine of > or = 1.5 mg/dL improved specificity. CONCLUSIONS: This analysis demonstrates that any detectable decrease in renal function is associated with increased mortality and prolonged hospital stay. This suggests that therapeutic interventions which improve renal function might be beneficial. 相似文献
49.
In 16 African Americans (blacks, 14 men, 2 women) with average admission mean arterial pressure (MAP, mm Hg) 99.9+/-3.5 (mean+/-SEM), we investigated whether NaCl-induced renal vasoconstriction attends salt sensitivity and, if so, whether supplemental KHCO3 ameliorates both conditions. Throughout a 3-week period under controlled metabolic conditions, all subjects ate diets containing 15 mmol NaCl and 30 mmol potassium (K+) (per 70 kg body wt [BW] per day). Throughout weeks 2 and 3, NaCl was loaded to 250 mmol/d; throughout week 3, dietary K+ was supplemented to 170 mmol/d (KHCO3). On the last day of each study week, we measured renal blood flow (RBF) and glomerular filtration rate (GFR) using renal clearances of PAH and inulin. Ten subjects were salt sensitive (SS) (DeltaMAP >+5%) and 6 salt resistant (SR). In NaCl-loaded SS but not SR subjects, RBF (mL/min/1.73 m2) decreased from 920+/-75 to 828+/-46 (P<0.05); filtration fraction (FF, %) increased from 19. 4+/- to 21.4 (P<0.001); and renal vascular resistance (RVR) (10(3)xmm Hg/[mL/min]) increased from 101+/-8 to 131+/-10 (P<0.001). In all subjects combined, DeltaMAP varied inversely with DeltaRBF (r =-0.57, P=0.02) and directly with DeltaRVR (r = 0.65, P=0.006) and DeltaFF (r = 0.59, P=0.03), but not with MAP before NaCl loading. When supplemental KHCO3 abolished the pressor effect of NaCl in SS subjects, RBF was unaffected but GFR and FF decreased. The results show that in marginally K+-deficient blacks (1) NaCl-induced renal vasoconstrictive dysfunction attends salt sensitivity; (2) the dysfunction varies in extent directly with the NaCl-induced increase in blood pressure (BP); and (3) is complexly affected by supplemented KHCO3, GFR and FF decreasing but RBF not changing. In blacks, NaCl-induced renal vasoconstriction may be a pathogenetic event in salt sensitivity. 相似文献
50.
Kikuchi S Crabtree JE Forman D Kurosawa M 《The American journal of gastroenterology》1999,94(12):3455-3459
OBJECTIVE: We assessed the association between infection with CagA-positive and -negative Helicobacter pylori and the risk of gastric cancer in young adults. METHODS: CagA IgG antibodies were measured in sera of subjects participating in a case-control study in Japan. The study subjects were 103 gastric cancer patients <40 yr of age, 100 inpatients with benign diseases, and 101 screenees younger than age 43 yr. RESULTS: Compared with the H. pylori-negative/CagA-negative (H. pylori-/CagA-) group, both the H. pylori-positive/CagA-negative (H. pylori+/CagA-) group and the H. pylori-positive/CagA-positive (H. pylori+/CagA+) groups showed elevated odds ratios for intestinal-type, diffuse-type, early, advanced, proximal, and distal gastric cancers. All the relationships were significant except for the H. pylori+/CagA- group in relation to proximal cancer. The overall odds ratios (95% confidence intervals) for gastric cancer in the H. pylori+/CagA- and the H. pylori+/CagA+ groups were 15.0 (6.4, 35.2) and 14.6 (6.7, 31.9), respectively. Between these two groups, no significant difference was observed in risks for intestinal-type, diffuse-type, early, advanced, proximal, or distal gastric cancer. CONCLUSIONS: In those <40 yr of age, it is concluded that both CagA-positive and CagA-negative H. pylori infections are related to risks of intestinal-type, diffuse-type, early, advanced, and distal gastric cancers. 相似文献