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   38467篇
  免费   3168篇
  国内免费   82篇
耳鼻咽喉   471篇
儿科学   1147篇
妇产科学   907篇
基础医学   5186篇
口腔科学   706篇
临床医学   4097篇
内科学   6987篇
皮肤病学   499篇
神经病学   3885篇
特种医学   1150篇
外科学   5093篇
综合类   1167篇
现状与发展   1篇
一般理论   51篇
预防医学   3604篇
眼科学   1011篇
药学   2812篇
中国医学   55篇
肿瘤学   2888篇
  2022年   364篇
  2021年   643篇
  2020年   407篇
  2019年   601篇
  2018年   751篇
  2017年   512篇
  2016年   649篇
  2015年   724篇
  2014年   931篇
  2013年   1476篇
  2012年   2119篇
  2011年   2022篇
  2010年   1183篇
  2009年   1107篇
  2008年   1895篇
  2007年   1973篇
  2006年   1787篇
  2005年   1864篇
  2004年   1875篇
  2003年   1731篇
  2002年   1665篇
  2001年   959篇
  2000年   920篇
  1999年   839篇
  1998年   474篇
  1997年   357篇
  1996年   384篇
  1995年   370篇
  1994年   302篇
  1993年   329篇
  1992年   632篇
  1991年   602篇
  1990年   649篇
  1989年   603篇
  1988年   575篇
  1987年   542篇
  1986年   540篇
  1985年   517篇
  1984年   411篇
  1983年   330篇
  1982年   283篇
  1981年   271篇
  1980年   238篇
  1979年   349篇
  1978年   248篇
  1977年   229篇
  1976年   239篇
  1975年   244篇
  1974年   293篇
  1973年   226篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Renal and urological anomalies in Down syndrome (DS) have received little attention compared with the nephrourological findings described in other chromosomal abnormalities. Renal hypoplasia, hydroureteronephrosis, ureterovesical and ureteropelvic junction obstruction, and vesicoureteral reflux, but not posterior urethral valves, have been associated with DS. We report the occurrence of posterior urethral valves in three male infants with DS at a single institution. All had multiple urological procedures for correction or palliation of obstruction. Children with DS may have an increased risk for developing posterior urethral valves and obstructive uropathy. Furthermore, they may also develop chronic renal failure secondary to posterior urethral valves. Therefore, we suggests that infants with DS be screened with ultrasonography for renal and urological abnormalities early in life and, if abnormal, a contrast voiding cystourethrogram be performed to rule out posterior urethral valves or other bladder or urethral abnormalities. A review of the renal and urological anomalies in DS reported in the literature since 1960 is presented.  相似文献   
62.
63.
Coronary heart disease is the leading cause of death in New Zealand. Death rates are higher among the Maori than the European population but rates have been declining in both groups over recent years. The occurrence of coronary heart disease among the Pacific Island population in New Zealand is unknown. Data from the National Health Statistics Centre (NHSC) and the Auckland coronary or stroke (ARCOS) study were used to describe the occurrence of coronary heart diseases among Pacific Island people. Age standardised mortality rates show that coronary heart disease is an important cause of death among Pacific Island men. Death rates have declined between 1973-77 and 1978-82 but this trend did not continue among men in the 1983-86 period. Age standardised mortality rates from coronary heart disease from the ARCOS data are 175/100,000 and 52/100,000 for Pacific Island men and women compared with 325/100,000 and 141/100,000 for Maori men and women. Age standardised rates for European men and women are 154/100,000 and 36/100,000 respectively.  相似文献   
64.
65.
OBJECTIVE: Given the associated risk of general anesthesia in elderly patients with cardiovascular disease, the authors set out to determine the feasibility of transcanal cochlear implantation under local anesthesia with monitored anesthesia care. METHODS: A 70-year-old man with a history of coronary artery bypass grafting, diabetes mellitus, and an American Society of Anesthesiologists Class III cardiac status underwent cochlear implantation under local with monitored anesthesia care. RESULT: With the described technique and regimen of intravenous remifentanil and dexmedetomidine, the patient tolerated the 60-minute procedure without tachycardia, hyper- or hypotension, or cardiac ischemia. CONCLUSION: Cochlear implantation using the pericanal electrode technique performed under local anesthesia with monitored anesthesia care is possible in patients at risk for undergoing general anesthesia for cochlear implantation.  相似文献   
66.
67.
Background: The Bullard laryngoscope is useful for the management of a variety of airway management scenarios. Without the aid of a video system, teaching laryngoscopy skills occurs with indirect feedback to the instructor. The purpose of this study was to determine if use of a video system would quicken the process of learning the Bullard laryngoscope or improve the performance (speed or success) of its use.

Methods: Thirty-six anesthesia providers with no previous Bullard laryngoscope experience were randomly divided into two groups: initial training (first 15 intubations) with looking directly through the eyepiece (n = 20), or with the display of the scope on a video monitor (n = 16). The subjects each then performed 15 Bullard intubations by looking directly through the eyepiece.

Results: There was not an overall significant difference in laryngoscopy or intubation times between the groups. When only the first 15 intubations were considered, the laryngoscopy time was shorter in the video group (26 +/- 24) than in the nonvideo group (32 +/- 34;P < 0.04). In the first 15 patients, there were fewer single attempts at intubation (67.9%vs. 80.3%;P < 0.002) and more failed intubations (17.2%vs. 6.0%;P < 0.0001) in the nonvideo group.  相似文献   

68.
The neuronal and glial cell composition of the rat visual cortex (area 17) has been determined quantitatively using stereological techniques. The volume numerical densities (number of cells per mm3 of cortex) of neurons and of the principal glial cell types (astroglia, oligodendroglia, and microglia) were calculated from tangential semithin resin sections spaced at regular intervals 50 micron apart throughout the entire depth of the visual cortex. From measurements of cortical and laminar thickness the separate volume numerical densities of neurons and glial cells were derived for each lamina in the cortex. In addition, the absolute numbers of cells in each lamina under 1 mm2 of cortical surface were calculated. The mean cortical volume numerical density of neurons was 60,020 +/- 3840/mm3 (mean +/- SEM; n = 8), and 49,040 +/- 2610/mm3 for the combined glial cell types. Astroglia, oligodendroglia, and microglia were present in a ratio of 6:3:1 respectively. It was determined from neuronal and glial somatic volume estimates that the somata of these cells occupied approximately 13.5% of unit cortical volume, with 81.3% of the unit volume being occupied by cortical neuropil. Using previously published reports that described the laminar composition of neurons in terms of the relative proportions of pyramidal and non-pyramidal cells, the laminar volume numerical densities for these neuronal categories have been derived. In addition, it has been estimated that under 1 mm2 of cortical surface there are 79,500 pyramidal and 7790 non-pyramidal neurons distributed throughout layers 1-6 of the rat visual cortex.  相似文献   
69.
Effects of antidepressant medication on sexual function: a controlled study   总被引:3,自引:0,他引:3  
There has been little systematic study of the types of sexual dysfunction produced by antidepressant medication or of the frequency with which this type of adverse effect occurs. The authors report results of a double-blind study in which the effects of imipramine, phenelzine, and placebo on specific aspects of sexual function were assessed in depressed outpatients before and after 6 weeks of treatment. Both active treatments were associated with a high incidence of adverse changes in sexual function and produced significantly more adverse effects on sexual function than placebo. Orgasm and ejaculation were impaired to a greater extent than erection. Adverse sexual function changes secondary to antidepressant medication occurred frequently in both men and women, although men reported a higher incidence. Antidepressant-related sexual dysfunction may be of clinical importance for medication compliance in view of current recommendations that antidepressants be administered for longer periods as maintenance therapy or for prophylaxis.  相似文献   
70.
The glycosaminoglycan layer of bladder has been proposed to play a crucial role in protecting the bladder from harmful substances in urine. Rats were partially cystectomized to determine whether bladder glycosaminoglycans are routinely eluted from the bladder surface in detectable quantities. Cystectomy produced no detectable qualitative or quantitative changes in excreted GAG thereby showing that most urinary glycosaminoglycan originates in the kidney and not from the bladder. Damaging the glycosaminoglycan layer by a dilute acid wash, however, leads to a consistent decrease in the output of urinary GAG which recovers to normal at the same rate as the layer regenerates. This suggests that the newly exposed sites tightly bind urinary GAG. We suggest that such binding may be a component of the normal physiological defense mechanism of the bladder. The bladder glycosaminoglycan layer was isolated, dilute acid being used to elute ionically-bound material and brief trypsinization to elute intercalated proteoglycans from the luminal surface. The GAG from the luminal surface, which was present at a density of one chain per 50 nm.2 of bladder surface, was quite different in composition from that isolated from the whole bladder.  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