首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1905篇
  免费   159篇
  国内免费   13篇
耳鼻咽喉   6篇
儿科学   56篇
妇产科学   25篇
基础医学   257篇
口腔科学   28篇
临床医学   191篇
内科学   599篇
皮肤病学   8篇
神经病学   96篇
特种医学   112篇
外科学   265篇
综合类   53篇
一般理论   1篇
预防医学   202篇
眼科学   11篇
药学   101篇
肿瘤学   66篇
  2022年   18篇
  2021年   29篇
  2020年   19篇
  2019年   22篇
  2018年   22篇
  2017年   37篇
  2016年   39篇
  2015年   37篇
  2014年   32篇
  2013年   76篇
  2012年   70篇
  2011年   86篇
  2010年   42篇
  2009年   45篇
  2008年   64篇
  2007年   89篇
  2006年   88篇
  2005年   81篇
  2004年   72篇
  2003年   73篇
  2002年   77篇
  2001年   62篇
  2000年   72篇
  1999年   55篇
  1998年   28篇
  1997年   38篇
  1996年   32篇
  1995年   35篇
  1994年   30篇
  1993年   15篇
  1992年   59篇
  1991年   33篇
  1990年   35篇
  1989年   39篇
  1988年   38篇
  1987年   36篇
  1986年   38篇
  1985年   31篇
  1984年   32篇
  1983年   17篇
  1982年   16篇
  1981年   13篇
  1979年   19篇
  1978年   17篇
  1976年   16篇
  1975年   12篇
  1974年   16篇
  1973年   14篇
  1970年   15篇
  1968年   10篇
排序方式: 共有2077条查询结果,搜索用时 15 毫秒
51.
Objective: To investigate the appropriateness of hospitalization as the time to elicit patients’ medical care preferences, the authors evaluated the capability of seriously ill patients to participate in decision making early in hospitalization and their decision making capacity two weeks before hospital entry. Design: Cross-sectional study with retrospective evaluation of preadmission decision making capacity. Setting: Five acute care teaching hospitals. Patients: Four thousand three hundred one acutely ill hospitalized adults meeting predetermined severity of illness criteria in nine specific disease categories. Measurements: Surrogate decision makers’ estimates of the prior mental capacities of patients unable to be interviewed early in hospitalization about care preferences due to intubation, coma, or cognitive impairment. Comparison of the demographics, degrees of sickness at admission, and outcomes of interviewable vs noninterviewable patients. Main results: Forty percent of the patients were not interviewable concerning preferences. Of these, 83% could have participated in treatment decisions two weeks prior to hospitalization. The patients who were not interviewable were more acutely ill, had less chronic disease, and were more likely to die during hospitalization than the interviewable patients. Conclusions: Many acutely ill patients likely to die in the hospital lost their ability to make medical care decisions around the time of hospital admission. Preferences for care and advance directives should be discussed in the outpatient setting or very early in hospital admission. Presented at the annual meeting of the Society of General Internal Medicine, April 29–May 1, 1992, Washington, DC. Funding for SUPPORT is provided by the Robert Wood Johnson Foundation.  相似文献   
52.
BACKGROUND: Current HIV treatment guidelines recommend delaying antiretroviral therapy for nonadherent patients, which some fear may disproportionately affect certain populations and contribute to disparities in care. OBJECTIVES: To examine the relationship of physician's attitude toward prescribing protease inhibitors (PIs) to nonadherent patients with disparities in PI use and with health outcomes. DESIGN: Prospective cohort study. PATIENTS AND SETTING: A national probability sample of HIV-infected adults in the United States and their health care providers was surveyed between January 1996 and January 1998. We analyzed data on 1717 patients eligible for PI treatment and the 367 providers who cared for them. MEASUREMENTS: Providers' attitude toward prescribing PIs to nonadherent patients, time until patients' first receipt of PIs, mortality, and physical health status. MAIN RESULTS: Eighty-nine percent of providers agreed that patient adherence is important in their decision to prescribe PIs (Selective) while 11% disagreed (Nonselective). Patients who had a Selective provider received PIs later than those with a Nonselective provider (P =.05). Adjusting for patient demographics and health characteristics and provider demographics, HIV knowledge, and experience, Latinos, women, and poor patients received PIs later if their provider had a Selective attitude but as soon as others if their provider had a Nonselective attitude. African-American patients received PIs later than whites, irrespective of their providers' prescribing attitude. Patients with Selective providers had similar odds of mortality than those with Nonselective providers (odds ratio, 1.1; 95% confidence interval, 0.6 to 2.0), but had slightly worse adjusted physical health status at follow-up (49.1 vs 50.4, respectively; P =.04), after controlling for baseline physical health status and other patient and provider covariates. CONCLUSIONS: Most providers consider patient adherence an important factor in their decision to prescribe PIs. This attitude appears to account for the relatively later use of PI treatment among Latinos, women, and the poor. Given the rising HIV infection rates among minorities, women, and the poor, further investigation of this treatment strategy and its impact on HIV resistance and outcomes is warranted.  相似文献   
53.

BACKGROUND

Little is known about how providers communicate recommendations when scientific uncertainty exists.

OBJECTIVES

To compare provider recommendations to those in the scientific literature, with a focus on whether uncertainty was communicated.

DESIGN

Qualitative (inductive systematic content analysis) and quantitative analysis of previously collected audio-recorded provider–patient office visits.

PARTICIPANTS

Sixty-one providers and a socio-economically diverse convenience sample of 603 of their patients from outpatient community- and academic-based primary care, integrative medicine, and complementary and alternative medicine provider offices in Southern California.

MAIN MEASURES

Comparison of provider information-giving about vitamin D to professional guidelines and scientific information for which conflicting recommendations or insufficient scientific evidence exists; certainty with which information was conveyed.

RESULTS

Ninety-two (15.3 %) of 603 visit discussions touched upon issues related to vitamin D testing, management and benefits. Vitamin D deficiency screening was discussed with 23 (25 %) patients, the definition of vitamin D deficiency with 21 (22.8 %), the optimal range for vitamin D levels with 26 (28.3 %), vitamin D supplementation dosing with 50 (54.3 %), and benefits of supplementation with 46 (50 %). For each of the professional guidelines/scientific information examined, providers conveyed information that deviated from professional guidelines and the existing scientific evidence. Of 166 statements made about vitamin D in this study, providers conveyed 160 (96.4 %) with certainty, without mention of any equivocal or contradictory evidence in the scientific literature. No uncertainty was mentioned when vitamin D dosing was discussed, even when recommended dosing was higher than guideline recommendations.

CONCLUSIONS AND RELEVANCE

Providers convey the vast majority of information and recommendations about vitamin D with certainty, even though the scientific literature contains inconsistent recommendations and declarations of inadequate evidence. Not communicating uncertainty blurs the contrast between evidence-based recommendations and those without evidence. Providers should explore best practices for involving patients in decision-making by acknowledging the uncertainty behind their recommendations.
  相似文献   
54.
55.
Activity of lactosyl ceramide beta-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23) was found to be extremely low in enzyme preparations from liver, brain, and cultured skin fibroblasts from patients with Krabbe's disease. Leukocytes from one set of parents had enzyme levels approximately half those measured in control leukocytes. The low activity observed for this galactolipid hydrolase is the fourth enzymatic deficiency noted for this genetic disease. Beta-galactosidase activity toward galactocerebroside, psychosine, and monogalactosyl diglyceride is also low in patients with Krabbe's disease. Other lysosomal enzymes measured were found to be in the normal range. This enzymatic defect may provide a better explanation for the pathological and chemical findings previously reported for this syndrome.  相似文献   
56.
Five cardiology centers conducted open-label prospective trials of meobentine sulfate, an intravenously and orally available analog of bethanidine, to assess its potential for treatment of recurrent, drug refractory ventricular tachycardia (VT) or fibrillation (VF), and complex ventricular arrhythmias. The study population comprised 26 patients (mean age, 61 years); 18 were men. Coronary artery disease was present in 15, cardiomyopathy in six, and valvular heart disease in three. Patients presented with both VT and VF (seven), sustained VT alone (12), or frequent ventricular ectopy (PVCs) and nonsustained VT (seven). Of the 26 patients, 5 were enrolled in antiarrhythmic studies (chronic PVC suppression) and 21 were enrolled in programmed electrical stimulation (PES) studies. Two of five in the chronic PVC study showed greater than 75% arrhythmia suppression. Among 21 patients in PES studies, there were eight intravenous (16 mg/kg) and 19 oral trials (400 to 1000 mg every 6 hours, 3 days/dose interval). Five of 22 patients showed efficacy at repeat PES study (neither VT nor VF), one showed partial efficacy, and four were not restudied because of clinical arrhythmia (three) and/or adverse effects (two). Overall, three patients (12%) were continued on the drug for an extended period of time. Adverse experience included hypotension in 50% and gastrointestinal effects (nausea, vomiting, or diarrhea) in 56% (oral trials only). Adverse reactions led to drug discontinuation in six and dosage reduction in eight patients. Thus, meobentine may prevent induction of VT or VF or reduce frequency of complex PVCs in selected patients refractory to other antiarrhythmic agents, but the response rate is relatively low. Symptomatic hypotension or gastrointestinal adverse effects are common and may limit utility of meobentine as a chronic oral antiarrhythmic agent.  相似文献   
57.
The short-term effect of the mechanical lesion of the organum vasculosum of the lamina terminalis (OVLT) was investigated in 4-day cycling female rats. The lesions were performed on the 2nd day of diestrus, and the animals were killed by decapitation 30 h after the lesion. Serum LH, FSH and prolactin and hypothalamic LH-RH content of 3 different parts of the hypothalamus were determined with radioimmunoassay. OVLT lesion caused a significant increase in the LH-RH content of the mid-basal hypothalamus and in serum prolactin levels and a decrease in LH and FSH serum levels. The results support the view that the OVLT may play a role in the control of pituitary gonadotrophic hormone secretion.  相似文献   
58.
Subject  Anal incontinence is a well-known and feared complication following surgery involving the anal sphincter, particularly if partial transection of the sphincter is part of the surgical procedure. Methods  The literature was reviewed to evaluate the risk of postoperative incontinence following anal dilatation, lateral sphincterotomy, surgery for haemorrhoidal disease and anal fistula. Results  Various degrees of anal incontinence are reported with frequencies as follows: anal dilatation 0–50%, lateral sphincterotomy 0–45%, haemorrhoidal surgery 0–28%, lay open technique of anal fistula 0–64% and plastic repair of fistula 0–43%. Results vary considerably depending on what definition of “incontinence” was applied. The most important risk factors for postoperative incontinence are female sex, advanced age, previous anorectal interventions, childbirth and type of anal surgery (sphincter division). Sphincter lesions have been reported following procedures as minimal as exploration of the anal canal via speculum. Conclusions  Continence disorders after anal surgery are not uncommon and the result of the additive effect of various factors. Certain risk factors should be considered before choosing the operative procedure. Since options for surgical repair of postoperative incontinence disorders are limited, careful indications and minimal trauma to the anal sphincter are mandatory in anal surgery.  相似文献   
59.
60.
GM2 gangliosidosis is a fatal lysosomal storage disease caused by a deficiency of β-hexosaminidase (EC 3.2.1.52). There are two major isoforms of the enzyme: hexosaminidase A composed of an α and a β subunit (encoded by HEXA and HEXB genes, respectively); and, hexosaminidase B composed of two β subunits. Hexosaminidase A requires an activator protein encoded by GM2A to catabolize GM2 ganglioside, but even in the absence of the activator protein, it can hydrolyze the synthetic substrates commonly used to assess enzyme activity. GM2 gangliosidosis has been reported in Japanese Chin dogs, and we identified the disease in two related Japanese Chin dogs based on clinical signs, histopathology and elevated brain GM2 gangliosides. As in previous reports, we found normal or elevated hexosaminidase activity when measured with the synthetic substrates. This suggested that the canine disease is analogous to human AB variant of GM2 gangliosidosis, which results from mutations in GM2A. However, only common neutral single nucleotide polymorphisms were found upon sequence analysis of the canine ortholog of GM2A from the affected Japanese Chins. When the same DNA samples were used to sequence HEXA, we identified a homozygous HEXA:c967G>A transition which predicts a p.E323K substitution. The glutamyl moiety at 323 is known to make an essential contribution to the active site of hexosaminidase A, and none of the 128 normal Japanese Chins and 92 normal dogs of other breeds that we tested was homozygous for HEXA:c967A. Thus it appears that the HEXA:c967G>A transition is responsible for the GM2 gangliosidosis in Japanese Chins.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号