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   1391篇
  免费   78篇
  国内免费   11篇
耳鼻咽喉   1篇
儿科学   124篇
妇产科学   45篇
基础医学   105篇
口腔科学   38篇
临床医学   199篇
内科学   388篇
皮肤病学   18篇
神经病学   38篇
特种医学   231篇
外科学   93篇
综合类   45篇
预防医学   54篇
眼科学   8篇
药学   55篇
  1篇
肿瘤学   37篇
  2020年   7篇
  2019年   8篇
  2018年   15篇
  2017年   13篇
  2016年   14篇
  2015年   24篇
  2014年   28篇
  2013年   31篇
  2012年   39篇
  2011年   36篇
  2010年   46篇
  2009年   51篇
  2008年   40篇
  2007年   23篇
  2006年   34篇
  2005年   29篇
  2004年   25篇
  2003年   21篇
  2002年   30篇
  2001年   19篇
  2000年   18篇
  1999年   24篇
  1998年   87篇
  1997年   86篇
  1996年   91篇
  1995年   58篇
  1994年   56篇
  1993年   45篇
  1992年   27篇
  1991年   29篇
  1990年   15篇
  1989年   45篇
  1988年   32篇
  1987年   45篇
  1986年   26篇
  1985年   39篇
  1984年   28篇
  1983年   27篇
  1982年   18篇
  1981年   21篇
  1980年   10篇
  1979年   12篇
  1978年   11篇
  1977年   10篇
  1976年   13篇
  1975年   10篇
  1973年   9篇
  1971年   6篇
  1970年   6篇
  1968年   9篇
排序方式: 共有1480条查询结果,搜索用时 15 毫秒
31.
The major burden of preterm birth is in the developing world, where most of the increasing death and morbidity is secondary to infectious diseases such as malaria, HIV, tuberculosis, bacterial vaginosis and intestinal parasites. In some developing countries, the growth of medical care has outstripped the growth of preventive public health, with an associated increase in iatrogenic preterm births. In developed countries, more than one-third of preterm births are medically indicated because of conditions such as fulminating pre-eclampsia or severe intrauterine growth restriction. Neither of these conditions is currently preventable. One in five preterm births is associated with multiple pregnancy, and these have been greatly increased by assisted reproduction techniques. The use of tocolytics has proved disappointing perhaps because inflammation rather than spontaneous uterine activity is increasingly recognised as the final common pathway. Inappropriate antibiotics used late in pregnancy are ineffective and may have adverse effects. Currently, the most promising interventions are public health related and include reducing the transmission of communicable diseases, improvements in the management of diabetes and reduction in harmful behaviours such as smoking and drug abuse.  相似文献   
32.
Butyl benzyl phthalate (BBP) was administered in the diet at 0, 750, 3750, and 11,250 ppm ad libitum to 30 rats per sex per dose for two offspring generations, one litter/breeding pair/generation, through weaning of F2 litters. Adult F0 systemic toxicity and adult F1 systemic and reproductive toxicity were present at 11,250 ppm (750 mg/kg per day). At 11,250 ppm, there were reduced F1 and F2 male anogenital distance (AGD) and body weights/litter during lactation, delayed acquisition of puberty in F1 males and females, retention of nipples and areolae in F1 and F2 males, and male reproductive system malformations. At 3750 ppm (250 mg/kg per day), only reduced F1 and F2 offspring male AGD was present. There were no effects on parents or offspring at 750 ppm (50 mg/kg per day). The F1 parental systemic and reproductive toxicity no observable adverse effect level (NOAEL) was 3750 ppm. The offspring toxicity NOAEL was 3750 ppm. The offspring toxicity no observable effect level (NOEL) was 750 ppm, based on the presence of reduced AGD in F1 and F2 males at birth at 3750 ppm, but no effects on reproductive development, structures, or functions.  相似文献   
33.

Introduction

To use screening cardiac troponin (cTn) measurements and electrocardiograms (ECGs) to determine the incidence of elevated cTn and of myocardial infarction (MI) in patients admitted to the intensive care unit (ICU), and to assess whether these findings influence prognosis. This is a prospective screening study.

Materials and methods

We enrolled consecutive patients admitted to a general medical-surgical ICU over two months. All patients underwent systematic screening with cTn measurements and ECGs on ICU admission, then daily for the first week in ICU, alternate days for up to one month and weekly thereafter until ICU death or discharge, for a maximum of two months. Patients without these investigations ordered during routine clinical care underwent screening for study purposes but these results were unavailable to the ICU team. After the study, all ECGs were interpreted independently in duplicate for ischaemic changes meeting ESC/ACC criteria supporting a diagnosis of MI. Patients were classified as having MI (elevated cTn and ECG evidence supporting diagnosis of MI), elevated cTn only (no ECG evidence supporting diagnosis of MI), or no cTn elevation.

Results

One hundred and three patients were admitted to the ICU on 112 occasions. Overall, 37 patients (35.9 per cent) had an MI, 15 patients (14.6 per cent) had an elevated cTn only and 51 patients (49.5 per cent) had no cTn elevation. Patients with MI had longer duration of mechanical ventilation (p < 0.0001), longer ICU stay (p = 0.001), higher ICU mortality (p < 0.0001) and higher hospital mortality (p < 0.0001) compared with those with no cTn elevation. Patients with elevated cTn had higher hospital mortality (p = 0.001) than patients without cTn elevation. Elevated cTn was associated with increased hospital mortality (odds ratio 27.3, 95 per cent CI 1.7 – 449.4), after adjusting for APACHE II score, MI and advanced life support. The ICU team diagnosed 18 patients (17.5 per cent) as having MI on clinical grounds; four of these patients did not have MI by adjudication. Thus, screening detected an additional 23 MIs not diagnosed in practice, reflecting 62.2 per cent of MIs ultimately diagnosed. Patients with MI diagnosed by the ICU team had similar outcomes to patients with MI detected by screening alone.

Conclusion

Systematic screening detected elevated cTn measurements and MI in more patients than were found in routine practice. Elevated cTn was an independent predictor of hospital mortality. Further research is needed to evaluate whether screening and subsequent treatment of these patients reduces mortality.  相似文献   
34.
35.
Background As a result of the high prevalence, basal cell carcinoma (BCC) causes a significant and expensive health care problem. Objective In this study, we evaluate the proportional increase in BCC by histological subtype over the last two decades. Methods We retrospectively reviewed all primary histological confirmed BCCs diagnosed in the Maastricht University Medical Centre in The Netherlands in the years 1991, 1999 and 2007. Results An annual increase of the number of BCCs of 7% for both genders was shown. The age‐standardized incidence rates for BCC increased between 1991 and 2007 from 54.2 to 162.1 per 100 000 men and from 61.7 to 189.8 per 100 000 women. The proportion of superficial BCC increased significantly from 17.6% to 30.7%. Conclusion The incidence of BCC is continuing to increase this century. The observed shift to the superficial histological subtype, which can be treated non‐surgically, might reduce the workload in the busy dermatologists practice.  相似文献   
36.
37.
38.

Background

The effectiveness of diclofenac versus paracetamol in primary care patients with pain caused by knee osteoarthritis is unclear.

Aim

To assess the effectiveness of diclofenac compared with paracetamol over a period of 2, 4, and 12 weeks in patients with knee osteoarthritis.

Design and setting

Randomised controlled trial in general practice.

Method

There were 104 patients included in the study, they were aged ≥45 years consulting their GP with knee pain caused by knee osteoarthritis. Patients were randomly allocated to diclofenac (n = 52) or paracetamol (n = 52) for at least 2 weeks. Primary outcomes were daily knee pain severity, and knee pain and function measured with the Knee Injury and Osteoarthritis Outcome Score (KOOS).

Results

Over a period of 2- and 4-weeks follow-up, no significant difference in daily knee pain was found between the patient groups: estimated differences of 0.5 (95% CI = −0.2 to 1.3) and −0.2 (95% CI = −1.0 to 0.7), respectively. Over the 12-weeks follow-up, no significant differences were found between both groups for KOOS pain: estimated difference of −2.8 (95% CI = −10.7 to 5.1) and KOOS function of −2.7 (−10.6 to 5.0).

Conclusion

Over a period of 2- and 4-weeks follow-up no significant difference in daily measured knee pain severity was found between primary care patients with knee osteoarthritis taking paracetamol or diclofenac. Also, over a period of 12-weeks follow-up no significant differences were found regarding KOOS pain and KOOS function between both groups. Patients more frequently reported minor adverse events after taking diclofenac (64%) than paracetamol (46%).  相似文献   
39.
Shami  PJ; Weinberg  JB 《Blood》1996,87(3):977-982
Nitric oxide (NO) is a reactive molecule with numerous physiologic and pathophysiologic roles affecting the nervous, cardiovascular, and immune systems. In previous work, we have demonstrated that NO inhibits the growth and induces the monocytic differentiation of cells of the HL- 60 cell line. We have also demonstrated that NO inhibits the growth of acute nonlymphocytic leukemia cells freshly isolated from untreated patients and increases monocytic differentiation antigens in some. In the present work, we studied the effect of NO on the growth and differentiation of normal human bone marrow cells in vitro. Mononuclear cells isolated from human bone marrow were cultured in semisolid media and treated with the NO-donating agents sodium nitroprusside (SNP) or S- nitroso-acetyl penicillamine (SNAP) (0.25 to 1 mmol/L). Both agents decreased colony-forming unit-erythroid (CFU-E) and colony-forming unit- granulocyte macrophage (CFU-GM) formation by 34% to 100%. When CD34+ cells were examined, we noted that these cells responded to SNP and SNAP differently than did the mononuclear cells. At a concentration range of 0.25 to 1 mmol/L, SNP inhibited the growth of CFU-E by 30% to 75%. However, at the same concentration range, SNP increased the number of CFU-GM by up to 94%. At concentrations of 0.25 to 1 mmol/L, SNAP inhibited the growth of CFU-E by 33% to 100%. At a concentration of 0.25 mmol/L, SNAP did not affect CFU-GM. At higher concentrations, SNAP inhibited the growth of CFU-GM. Although SNP increased intracellular levels of cGMP in bone marrow cells, increasing cGMP in cells by addition of 8-Br-cGMP (a membrane permeable cGMP analogue) did not reproduce the observed NO effects on bone marrow colonies. These results demonstrate that NO can influence the growth and differentiation of normal human bone marrow cells. NO (generated in the bone marrow microenvironment) may play an important role modulating the growth and differentiation of bone marrow cells in vivo.  相似文献   
40.
OBJECTIVE: To examine whether promoter polymorphisms associated with variation in interleukin-10 (IL-10) production are relevant to the development of rheumatoid arthritis (RA) or Felty's syndrome (FS). METHODS: DNA was obtained from 44 FS patients, 117 RA patients and 295 controls. The promoter region between -533 and - 1120 was amplified by polymerase chain reaction, and polymorphisms detected by restriction enzyme digest or sequence-specific oligonucleotide probing. RESULTS: We found no significant difference in allele or haplotype frequencies between the groups. CONCLUSION: There is no association between FS or RA and these recently identified IL-10 promoter polymorphisms. Other genetic or environmental factors could explain the alterations in IL-10 levels seen in these conditions.   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