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   1358篇
  免费   66篇
  国内免费   6篇
耳鼻咽喉   11篇
儿科学   38篇
妇产科学   29篇
基础医学   154篇
口腔科学   72篇
临床医学   131篇
内科学   262篇
皮肤病学   22篇
神经病学   67篇
特种医学   34篇
外科学   284篇
综合类   41篇
预防医学   56篇
眼科学   52篇
药学   98篇
中国医学   5篇
肿瘤学   74篇
  2023年   17篇
  2022年   35篇
  2021年   71篇
  2020年   40篇
  2019年   39篇
  2018年   32篇
  2017年   27篇
  2016年   31篇
  2015年   49篇
  2014年   56篇
  2013年   70篇
  2012年   101篇
  2011年   85篇
  2010年   43篇
  2009年   44篇
  2008年   65篇
  2007年   77篇
  2006年   71篇
  2005年   75篇
  2004年   50篇
  2003年   47篇
  2002年   53篇
  2001年   27篇
  2000年   35篇
  1999年   30篇
  1998年   8篇
  1997年   9篇
  1996年   8篇
  1995年   6篇
  1994年   4篇
  1992年   7篇
  1991年   11篇
  1990年   17篇
  1989年   4篇
  1988年   7篇
  1987年   13篇
  1986年   7篇
  1985年   4篇
  1984年   6篇
  1980年   3篇
  1979年   5篇
  1978年   4篇
  1977年   2篇
  1976年   2篇
  1975年   4篇
  1974年   5篇
  1972年   4篇
  1970年   3篇
  1969年   2篇
  1968年   2篇
排序方式: 共有1430条查询结果,搜索用时 15 毫秒
1.
Purpose:Since the declaration of the lockdown due to COVID-19, the usage of digital devices has gone up across the globe, resulting in a challenge for the visual systems of all ages. The purpose of this study is to assess the impact of the lockdown on digital device usage, and consequently, the ocular surface health implications and circadian rhythm abnormalities related to digital eye strain.Methods:An open online survey was sent through various social media platforms and was open for a period of 2 weeks.Results:A total of 407 usable responses were obtained; the average age of respondents was 27.4 years. Typically, 93.6% of respondents reported an increase in their screen time since the lockdown was declared. The average increase in digital device usage was calculated at about 4.8 ± 2.8 h per day. The total usage per day was found to be 8.65 ± 3.74 hours. Sleep disturbances have been reported by 62.4% of people. Typically, 95.8% of respondents had experienced at least one symptom related to digital device usage, and 56.5% said that the frequency and intensity of these symptoms increased since the lockdown was declared.Conclusion:The study highlighted the drastic increase in use of digital devices after the initiation of the COVID-19 lockdown, and along with it, the slow deterioration of ocular health across all age groups. Awareness about prevention of digital eye strain should be stressed, and going forward, measures to bring these adverse effects to a minimum should be explored.  相似文献   
2.
3.
BACKGROUND: The effect of mitral valve morphology (MVM) on the long-term results of mitral balloon valvuloplasty (MBV) is not well established. The aim of the study was to evaluate the impact of MVM on long-term outcome of MBV. METHODS: Five hundred and eighteen consecutive patients (mean age, 31+/-11 years) who underwent successful MBV were followed up for 0.5-16.5 (mean, 6+/-4.5) years. Patients were divided into two groups according to their mitral echo score (MES) before MBV: group A (n=340; MES8). RESULTS: We report the immediate and long-term clinical and echocardiographic results of the above-mentioned 518 consecutive patients. The mitral valve area was significantly larger in group A than in group B, both immediately after MBV (2.0+/-0.3 vs. 1.82+/-0.3 cm2, respectively; P<0.0001) and also at the last follow-up (1.8+/-0.33 vs. 1.5+/-0.33 cm2, respectively; P<0.0001). Restenosis occurred in 38/340 (11%) in group A vs. 73/178 (41%) in group B (P<0.0001). Actuarial freedom from restenosis at 5, 10, 15 years were 92+/-2%, 85+/-3%, 65+/-6% for group A vs. 72+/-4%, 44+/-5%, 9+/-6% for group B (P<0.001). Event-free survival rates at 5, 10, 15 years for group A were 93+/-1%, 88+/-2%, 66+/-6% vs. 82+/-3%, 59+/-6%, 8+/-7% for group B (P<0.0001). Stepwise Cox multivariate regression analysis identified MES, preprocedure functional class, and postprocedure mitral valve area相似文献   
4.
Hereditary thrombophilia is caused by various inherited disorders. Most lead to a familial tendency to recurrent venous, not arterial, thrombosis, usually at a young age, and with spontaneous onset. Most of the genetic defects known today affect the function of natural anticoagulant pathways, in particular, the protein C system. In this study, 602 (265 female, 337 male) patients with suspected thrombosis, arterial or venous, were referred to King Hussein Medical Center in Amman, Jordan. The prevalence of hereditary deficiencies of antithrombin (AT), protein S (PS), and protein C (PC) were studied over a seven-year period (1993-2000). Activated protein C (APC-R) resistance subjects were studied over four years (1996-2000). The mean age was 30 years in females and 42 years in males. A diagnosis was established in 22.4% (n = 135) of the subjects (20.3% venous, 2.1% arterial). Protein C deficiency was found in 3.8%, protein S deficiency in 2.3% and antithrombin deficiency in 1.4% of our sample group. An APC-R problem was seen in 23.0% (n = 89) of the surveyed population. Out of the APC-R patients, 75.0% had the DNA analysis of a factor V Leiden mutation present. Of the subjects found to have the mutation 87.0% were heterozygous and 13.0% were homozygous. These results confirm that APC-R, as a result of factor V Leiden mutation, is the most prevalent cause of thrombosis, and thrombophilia is related to venous, not arterial, thrombosis.  相似文献   
5.
Newly hatched White Leghorn male chicks were used in this study. Different doses of T3 (O.1 or 1 ppm) or TRH (1 or 5 ppm) were administered in the feed for an 8-week period. Chicken growth hormone (cGH) (10 μg/kg BW) was injected (i.v.) into a different group of chicks twice daily for 1 week starting at 7 weeks of age. A different group received both T3 (0.1 and 1 ppm) and cGH. Serum concentrations of T4, T3 and GH, antibody production against sheep red blood cells (SRBC) and Brucella Abortus (BA), and in vitro proliferative response of both T- and B-lymphocytes to mitogenic stimulation were measured. Supplementation of T3 (1 ppm) significantly lowered T4 and increased T3 concentrations. No effect of any hormone treatment on antibody production was observed. T3 supplementation and cGH injection alone or with T3 (0.1 ppm) significantly increased blastogenic response of lymphocytes to either Con-A or LPS mitogenic stimulation. It was concluded that T3 and GH are involved in lymphocyte activity of chickens.  相似文献   
6.
OBJECTIVE: To evaluate beta-endorphin secretion in euprolactinemic cases of luteal phase defect (LPD). DESIGN: Serial blood samples from the 18th to the 26th day of the menstrual cycle were assayed for beta-endorphin, progesterone (P), estradiol (E2), and prolactin (PRL) in cases of LPD and controls. Diagnosis of LPD was based on determinations of serum P and premenstrual endometrial biopsy. SETTING: From Cairo University Hospitals. PATIENT, PARTICIPANTS: Twenty-six women with LPD and 8 normal fertile women (controls) were chosen. INTERVENTIONS: None. MAIN OUTCOME MEASURES: beta-Endorphin, P, E2, and PRL concentrations were determined by the corresponding 125I radioimmunoassay. RESULTS: Plasma beta-endorphin level in cases of LPD varied from 2.58 to 9.14 pmol/L, whereas the level of controls varied from 2.41 to 5.57 pmol/L. The mean value of plasma beta-endorphin in cases of LPD was significantly higher than that of controls by 146% (P less than 0.0005). In spite of the significant decrease of serum P in cases of LPD, serum E2 level did not differ significantly from that of controls. CONCLUSION: The possible sources of beta-endorphin rise and its implication in the etiology of LPD are explained.  相似文献   
7.
Heat-shock protein synthesis by human polymorphonuclear cells   总被引:4,自引:0,他引:4  
Mature human neutrophils from peripheral blood are known to be capable of limited protein biosynthetic activity. We now show that these cells are inducible for heat-shock protein synthesis when placed in short-term culture. Synthesis of hsp70 and hsp85 as well as the response to various temperatures and the time course of induction were typical for mammalian cell systems. This heat-shock response was blocked by actinomycin D added before heat exposure. This demonstration that hsp genes can be activated by heat exposure of terminally differentiated neutrophils supports the hypothesis that gene activation can serve a physiological role in these cells and opens up the possibility that synthesis of other gene products is similarly inducible.  相似文献   
8.
Acute, noninfectious, eosinophilic pneumonia with respiratory failure has been described in adults. This new form of eosinophilic lung disease differs from the previously described types of eosinophilic pneumonia. Patients with this entity develop rapid progressive respiratory failure, which seems to respond to corticosteroid therapy. Eosinophilia in lung biopsy specimen, or in bronchoalveolar lavage fluid seems to be a common denominator. We present the first pediatric case of this new, distinct form of eosinophilic lung disease and review the pertinent literature.  相似文献   
9.
10.
In a retrospective study of 35 patients (29 men, 6 women) with primary non-Hodgkin's lymphomas of the gastrointestinal tract, 13 of the tumours were located in the stomach, 21 in the small bowel and one in the colon. Various radiological findings were detected, and the majority of tumours (23) had high grade histology. Three patients had immunoproliferative small intestinal disease. Only tumours in stages I and II were included in the study, and the majority (25) were in stage IIA. All patients except one had undergone resection of the neoplasm. This was followed by combined chemotherapy in 25 patients, and chemotherapy followed by radiotherapy in three cases. There were two (5.7%) hospital mortalities. Two- and 5-year survival rates were better in those patients with low stage and low grade tumours. The overall 5-year survival rate was 38%.  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