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   760篇
  免费   39篇
  国内免费   14篇
儿科学   52篇
妇产科学   13篇
基础医学   100篇
口腔科学   17篇
临床医学   128篇
内科学   103篇
皮肤病学   10篇
神经病学   33篇
特种医学   192篇
外科学   32篇
综合类   32篇
预防医学   28篇
眼科学   2篇
药学   43篇
肿瘤学   28篇
  2023年   2篇
  2021年   7篇
  2020年   4篇
  2019年   5篇
  2018年   6篇
  2017年   5篇
  2016年   8篇
  2015年   14篇
  2014年   20篇
  2013年   19篇
  2012年   14篇
  2011年   16篇
  2010年   19篇
  2009年   24篇
  2008年   12篇
  2007年   28篇
  2006年   17篇
  2005年   24篇
  2004年   10篇
  2003年   13篇
  2002年   5篇
  2001年   10篇
  2000年   9篇
  1999年   23篇
  1998年   39篇
  1997年   48篇
  1996年   38篇
  1995年   39篇
  1994年   23篇
  1993年   27篇
  1992年   15篇
  1991年   19篇
  1990年   18篇
  1989年   13篇
  1988年   24篇
  1987年   23篇
  1986年   21篇
  1985年   18篇
  1984年   9篇
  1983年   8篇
  1982年   18篇
  1981年   12篇
  1980年   22篇
  1979年   4篇
  1978年   12篇
  1977年   22篇
  1976年   12篇
  1975年   8篇
  1974年   2篇
  1963年   2篇
排序方式: 共有813条查询结果,搜索用时 15 毫秒
71.
72.
Mycobacterial Infections After Renal Transplantation   总被引:5,自引:0,他引:5  
Mycobacterial infections occurred in 11 of 633 (1.7 per cent)recipients of successful renal transplants. There were no casesof tuberculosis in patients receiving chemoprophylaxis, butamongst those who did not receive prophylaxis disease occurredin six of the 27 (22 per cent) high-risk patients. The majorcause of morbidity during treatment was renal allograft rejection,largely due to reduction in immunosuppressive drug therapy.  相似文献   
73.
Objective To investigate which factors predict return to work (RTW) after 3 and 6 months in employees sick-listed due to minor mental disorders. Methods Seventy GPs recruited 194 subjects at the start of sick leave due to minor mental disorders. At baseline (T0), 3 and 6 months later (T1 and T2, respectively), subjects received a questionnaire and were interviewed by telephone. Using multivariate logistic regression analyses, we developed three prediction models to predict RTW at T1 and T2. Results The RTW rates were 38% after 3 months (T1) and 61% after 6 months (T2). The main negative predictors of RTW at T1 were: (a) a duration of the problems of more than 3 months before sick leave; and (b) somatisation. The main negative predictors of RTW at T2 were: (a) a duration of the problems of more than 3 months before sick leave; (b) more than 3 weeks of sick leave before inclusion in the study; and (c) anxiety. The main negative predictors of RTW at T2 for those who had not resumed work at T1 were: (a) more than 3 weeks of sick leave before inclusion in the study; and (b) depression at T1. The predictive power of the models was moderate with AUC-values between 0.695 and 0.763. Conclusions The main predictors of RTW were associated with the severity of the problems. A long duration of the problems before the occurrence of sick leave and a long duration of sick leave before seeking help predict a relatively small probability to RTW within 3–6 months. High baseline somatisation and anxiety, and high depression after 3 months make the prospect even worse. Since these predictors are readily assessable with just a few questions and a symptom questionnaire, this opens the opportunity to select high-risk employees for a targeted intervention to prevent long-term absenteeism.  相似文献   
74.
Mid-trimester loss--appraisal of a screening protocol   总被引:1,自引:0,他引:1  
The main causes for mid-trimester loss are known. There is likely to be overlap with those of first trimester loss, but the proportions may be different. We wished to perform an aetiological survey in a large population of patients with a history of recurrent miscarriage, for possible explanations for their second trimester miscarriages. Database analysis of 636 patients attending a UK University Teaching Hospital dedicated miscarriage clinic between 1991 and 1996 revealed a 25% prevalence (n = 158) for second trimester miscarriage. Results from an investigative screening protocol were positive in 50% of cases: 33% (n = 52) tested positive for antiphospholipid syndrome (APS); 8% (n = 13) fulfilled strict criteria for cervical incompetence; there was a 4% prevalence of uterine anomaly; 3% for infection (n = 5) and 2% of patients (n = 3) proved to be hypothyroid. Importantly, dual pathology was found in 5% of patients with a history of second trimester miscarriage. As idiopathic mid-trimester loss is a diagnosis by exclusion, a high index of suspicion is required, as are modern diagnostic techniques.   相似文献   
75.
76.
Breast MR imaging with loop-gap resonators   总被引:1,自引:0,他引:1  
Hornak  JP; Szumowski  J; Rubens  D; Janus  J; Bryant  RG 《Radiology》1986,161(3):832-834
Breast images obtained at 1.5 T using a loop-gap resonator pair as both the excitation and detection device are presented. The efficiency of this approach is high, as judged by the low level of radio frequency (RF) power required to obtain a 90 degree pulse and the uniformity of the RF field within the resonator pair. A modification of the pair geometry provides for reasonable observation of the tissues through the chest wall and laterally to the axillae.  相似文献   
77.
78.
79.
80.
Minimizing the geometric surface area of pacing electrodes increases impedance and reduces the current drain during stimulation, provided that voltage (pulse-width) thresholds remain unchanged. This may be feasible by coating the electrode surface to increase the capacity of the electrode tissue interface and to diminish polarization. Ten unipolar, tined leads with a surface area of 1.3 mm2 and a “fractal” coating of Iridium (Biotronik SD-V137) were implanted in the ventricle, and electrogram amplitude (unfiltered), slew-rate, pacing threshold (0.5 ms), and impedance (2.5 V; 0.5 ms) were measured by the 5311 PSA (Medtronic). On days 0, 2, 5, 10, 28, 90, 180, 360 postimplant, sensing threshold (up to 7.0 mV, measuring range 1–14 mV on day 360 only) and the strength duration curve (0.5–4.0 V; 0.03–1.5 ms; steps: 0.5 V; 0.01 ms, respectively) were determined, the minimum charge delivered per pulse (charge threshold), and the impedance were taken from pacemaker telemetry (Intermedics 294–03). Data were compared with those of an earlier series of 20 unipolar, tined TIR-leads (Biotronik) with a surface area of 10 mm2 and a “fractal” coating of titanium nitride. With the model SD-V137 versus TIR, intraoperative electrogram amplitudes were 15.1 ± 6.1 versus 14.4 ± 3.9 mV(NS), slew rates 3.45 ± 1.57 versus 1.94 ± 1.06 V/s (P < 0. 05), pacing thresholds 0.16 ± 0.05 versus 0.52 ± 0.15 V (P < 0.01) and impedance measurements 1,136 ±175 versus 441 ± 73 Ω (P < 0.0001), respectively. During follow-up, sensing thresholds were the same with both leads. Differences in pulse width thresholds lost its significance on day 28 but resumed on day 360 (SD-V137: 0.08 ± 0.04 ms; TIR: 0.16 ± 0.06 ms at 2.5 V; P < 0.01). With an electrode surface of 1.3 mm2, charge per pulse and impedance consistently differed from control, beingO.15 ± 0.15 versus 0. 66 ± 0. 20 μC (P < 0.001) and 1,344 ± 376 versus 538 ± 79 Ω, respectively, one year after implantation (P < 0.0001). In summary, “fractally” coated small surface electrodes do not compromise sensing; by more than doubling impedance against controls they offer pacing thresholds (mainly in terms of charge) that are significantly lower than with the reference electrode.  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