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   554篇
  免费   23篇
  国内免费   19篇
耳鼻咽喉   3篇
儿科学   26篇
妇产科学   10篇
基础医学   52篇
口腔科学   11篇
临床医学   69篇
内科学   153篇
皮肤病学   9篇
神经病学   32篇
特种医学   52篇
外科学   83篇
综合类   22篇
预防医学   25篇
眼科学   3篇
药学   32篇
肿瘤学   14篇
  2018年   7篇
  2017年   5篇
  2016年   8篇
  2015年   20篇
  2014年   20篇
  2013年   18篇
  2012年   12篇
  2011年   9篇
  2010年   34篇
  2009年   21篇
  2008年   9篇
  2007年   19篇
  2006年   6篇
  2005年   9篇
  2004年   7篇
  2003年   7篇
  2002年   9篇
  2001年   8篇
  2000年   10篇
  1999年   9篇
  1998年   29篇
  1997年   18篇
  1996年   25篇
  1995年   12篇
  1994年   12篇
  1993年   15篇
  1992年   5篇
  1991年   12篇
  1990年   6篇
  1989年   15篇
  1988年   14篇
  1987年   8篇
  1986年   6篇
  1985年   7篇
  1983年   4篇
  1982年   7篇
  1980年   6篇
  1976年   3篇
  1975年   3篇
  1972年   3篇
  1962年   3篇
  1959年   15篇
  1958年   16篇
  1957年   14篇
  1956年   10篇
  1955年   15篇
  1954年   19篇
  1952年   5篇
  1949年   3篇
  1948年   4篇
排序方式: 共有596条查询结果,搜索用时 0 毫秒
1.
Eighteen men (mean age 27, range 18-30 years) treated for Hodgkin's disease with 6-8 courses of MVPP (Mustine, Vinblastine, Procarbazine and Prednisolone) have had Leydig cell function assessed by their steroidogenic responses to stimulation by a single bolus dose of HCG (1000 units intramuscularly). Normal age-matched men (n = 16) acted as controls. Baseline immunoreactive FSH was markedly raised in the patients (mean 18.1 +/- SD 6.9 vs 2.0 +/- 1.5 IU/l, P less than 0.0001) reflecting damage to the germinal epithelium. Immunoreactive LH was also greater in patients (10.3 +/- 3.9 IU/l) than in controls (3.9 +/- 1.9 IU/l, P less than 0.0001). There were no differences between the baseline testosterone, androstenedione, oestradiol, oestrone and sex hormone binding globulin (SHBG) concentrations. The testosterone/SHBG ratios were similar in the two groups and there was no correlation between baseline LH and testosterone concentrations or testosterone/SHBG ratios. Testosterone, androstenedione, oestradiol and oestrone secretion in response to HCG stimulation were similar at 24 h and 96 h in both groups. In order to explain the paradox of elevated immunoreactive LH in the face of normal testicular steroidogenesis in such patients, LH biological activity (B) as well as LH immunoreactivity (I) and FSH and testosterone were estimated in a second similar group of patients (n = 17, mean age 27, range 17-43 years) and in a further age-matched control group (n = 17). Bioactive and immunoreactive LH levels were significantly increased (P less than 0.005 and P less than 0.001, respectively) in the patient group.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
2.
Membrane flow within the myelin sheath in IDPN neuropathy   总被引:1,自引:0,他引:1  
This report describes some aspects of beta,beta'-iminodipropionitrile (IDPN) neuropathy in rats as observed by ultrastructural methods and X-ray diffraction. Light microscopy shows gross swelling of the axons in proximal lumbar spinal roots 8 days after intraperitoneal injection of IDPN. Mean axon cross-sectional area and mean axon perimeter increased to 280% and 160% of their control values, respectively. At the same time, myelin membrane packing was not visibly disturbed. In addition, X-ray diffraction patterns, recorded under physiological conditions, demonstrate that the myelin lipid bilayer thickness and widths of the aqueous spaces between bilayers did not change. Related observations are made on posterior tibial nerve (PNS myelin) and ventral spinal cord (CNS myelin). The various observations together are interpreted in terms of a fluid myelin membrane. It is proposed that the myelin membrane flows during axon swelling even though normal membrane-membrane contacts are maintained within the sheath. Membrane flow and slippage between membranes are explained in terms of a molecular model of the myelin multilayer.  相似文献   
3.
Elevated blood pressure is an important risk factor for renal-, cerebro- and cardiovascular diseases. We used an efficient discordant sib-pair ascertainment scheme to investigate the impact of the distal end of the long arm of human chromosome 5 (chromosomal region 5q31.1-qter) containing genes for the alpha1B and beta2 adrenergic receptors and the dopamine receptor type 1A on variation of systolic blood pressure in young Caucasians. We measured eight highly polymorphic markers spanning this positional candidate gene-rich region in 427 individuals from 55 three-generation pedigrees containing 69 discordant sibling pairs, and calculated multipoint identity by descent (MIBD) probabilities. The results of genetic linkage and association tests indicate that the region between markers D5S2093 and D5S462 is significantly linked to one or more polymorphic genes influencing interindividual variation in systolic blood pressure levels. Since the alpha1B adrenergic receptor and dopamine receptor type 1A genes are located close to these markers, these data suggest that genetic variation in one or both of these G protein-coupled receptors, which participate in the control of vascular tone, plays an important role in influencing interindividual variation in systolic blood pressure levels.   相似文献   
4.
This study evaluated the outcome of 33 children with asthma-like symptoms without objective evidence of asthma, and the role of certain factors in predicting the development of clinical asthma in these children. Data on symptom histories, lung functions (flow-volume spirometry, free running test and methacholine inhalation challenge test) and atopic sensitization (skin prick tests and markers of eosinophilic inflammation) were collected twice with an interval of 2 y, and the diagnoses were re-evaluated after the follow-up period. Based on the results, it was concluded that one-third of the children with prolonged or recurrent lower airway symptoms, such as cough or wheeze, either have mild asthma or will develop asthma in the near future. Children who had a significant response [≥ 10% fall in forced expiratory volume in 1 s (FEV1)] in the free running test formed a risk group for active asthma, whereas other baseline characteristics seemed not to predict the outcome.  相似文献   
5.
To determine the effects of animal and artificial surfactants on cerebral haemodynamics, 20 premature babies receiving mechanical ventilation were randomized to receive Curosurf or Exosurf surfactant. Anterior cerebral artery blood flow velocity (CABFV) was measured using Doppler ultrasound before and up to 2 h after treatment. Following animal surfactant there was a rapid reduction in CABFV (median -36%, range -43% to +8%, p < 0:01), whereas artificial surfactant resulted in a slower rise which was less marked (median +20%, range -7% to +62%, p < 0:05). There were no significant changes in blood pressure. Two hours after administration, the oxygenation index (OI) improved significantly only in babies receiving animal surfactant. In this group there was a significant association between the change in CABFV at 1 min and the change in OI at 2 h ( r = 0:66, p < 0:05). Animal surfactant produces rapid improvements in ventilation which are associated with marked alterations in cerebral haemodynamics.  相似文献   
6.
The current disparity of viable organs and patients in need of a transplant has been an impetus for innovative measures. Live donor renal transplantation offers significant advantages compared with cadaveric donor transplantation: increased graft and patient survival, diminution in incidence of delayed graft function, acute tubular necrosis (ATN), and reduction in waiting time. Notwithstanding these gains live donors continue to be underutilized and account for only approximately one quarter of all renal transplants performed in the United States. It has been felt that inherent disincentives to live donation have slowed its growth. These include degree and duration of postoperative pain and convalescence, child care concerns, cosmetic concerns, and time until return to full activities and employment. In an attempt to curtail the disincentives to live donation, laparoscopic live donation (laparoscopic donor nephrectomy; LDN) was developed. The purpose of this study was to compare the results of our first 25 laparoscopic nephrectomies (performed over a 10-month period from September 1998 through July 1999) with the previous 25 standard open donor nephrectomies (ODNs) completed over the past 3 years. We conducted a retrospective review of all donor nephrectomies and recipient pairs performed over the past 3 years. End points included sex, operative time, length of stay, immediate and long-term renal function, and willingness to donate. There were no differences in demographics of the ODN versus the LDN group. The average length of stay was 2.48+/-0.72 days for the LDN versus 4.08+/-0.28 days for the ODN. ODN and LDN have comparable short- and long-term function with no delayed graft function and no complications. Growth of living donor transplant has increased from 16 per cent of all kidney transplants performed in 1995 to 23 per cent in 1999. We conclude that LDN is a viable alternative to the standard donor operation. LDN has had a positive impact on the donor pool by minimizing disincentives to live donation. With the initiation of our laparoscopic program the number of LDNs has increased. Presently the live donor pool is the most viable alternative to significantly increase the number of kidneys for transplantation.  相似文献   
7.
8.
Labial adhesions are usually seen in early childhood or in the postmenopausal years, but this clinical entity is rarely seen in the reproductive years. We report a case of labial adhesion with acute urinary retention secondary to Bartholin's abscess in a reproductive‐aged woman with normal menstrual periods. We emphasize the possible occurrence of labial adhesion following Bartholin's abscess in the reproductive years with normal estrogen levels.  相似文献   
9.
Atrioesophageal Fistula After Cryoballoon PV Isolation . The risk of atrioesophageal fistula after cryoballoon pulmonary vein isolation is thought to be much lower than after radiofrequency ablation, seeing that no data exist on this complication so far. We report for the first time on the occurrence of an atrioesophageal fistula 4 weeks after cryoballoon ablation at the site of the left inferior pulmonary vein. We suggest that even when using cryothermal ablation technique, an imaging modality to assess the proximity of esophagus and left atrium should be routinely performed to avoid this fatal complication. (J Cardiovasc Electrophysiol, Vol. 23, pp. 1254–1257, November 2012)  相似文献   
10.
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