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   85953篇
  免费   7455篇
  国内免费   4262篇
耳鼻咽喉   830篇
儿科学   1096篇
妇产科学   1153篇
基础医学   11731篇
口腔科学   2007篇
临床医学   9479篇
内科学   14336篇
皮肤病学   1333篇
神经病学   5616篇
特种医学   3604篇
外国民族医学   39篇
外科学   10199篇
综合类   10093篇
现状与发展   7篇
一般理论   10篇
预防医学   5308篇
眼科学   2234篇
药学   8367篇
  44篇
中国医学   3059篇
肿瘤学   7125篇
  2024年   152篇
  2023年   884篇
  2022年   2389篇
  2021年   3309篇
  2020年   2172篇
  2019年   2186篇
  2018年   2590篇
  2017年   2175篇
  2016年   2292篇
  2015年   3179篇
  2014年   3970篇
  2013年   3869篇
  2012年   5932篇
  2011年   6042篇
  2010年   3834篇
  2009年   3160篇
  2008年   4377篇
  2007年   4343篇
  2006年   4007篇
  2005年   3565篇
  2004年   2754篇
  2003年   2522篇
  2002年   2186篇
  2001年   3446篇
  2000年   3381篇
  1999年   2950篇
  1998年   1302篇
  1997年   1130篇
  1996年   854篇
  1995年   726篇
  1994年   608篇
  1993年   478篇
  1992年   1330篇
  1991年   1139篇
  1990年   1005篇
  1989年   1058篇
  1988年   942篇
  1987年   865篇
  1986年   787篇
  1985年   691篇
  1984年   431篇
  1983年   362篇
  1982年   198篇
  1981年   161篇
  1980年   130篇
  1979年   220篇
  1978年   94篇
  1973年   104篇
  1972年   95篇
  1971年   103篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Background: The aggressive surgical approach to patients suspected of having acute appendicitis for fear of perforation, and the inaccuracy of available diagnostic methods lead to an unacceptably high negative appendicectomy rate, especially in young women, in whom gynecological disorders frequently mimic appendicitis. Our objectives were to determine the value of diagnostic laparoscopy in women of child-bearing age to reduce the number of negative laparotomies and establish the correct diagnosis to allow prompt and appropriate treatment. Methods: 161 consecutive adult female patients under 50 years of age with a clinical diagnosis of acute appendicitis underwent diagnostic laparoscopy prior to the planned appendicectomy. If an inflamed appendix was found, appendicectomy was usually done through a muscle-splitting McBurney incision. Other diagnoses were treated accordingly. A normal appendix was not removed. Results were compared to a group of 42 similar patients in whom the laparoscopy was omitted for various reasons, to 23 postmenopausal women, and to all 137 male adults, directly operated by the McBurney approach. Results: After laparoscopy, 55% of the patients required appendicectomy for appendicitis while in 23% a gynecological diagnosis was made in spite of previous examination by a gynecologist. Fourteen percent had a negative laparoscopy. There were no false-negative results. The negative appendicectomy rate after laparoscopy was 5% due to two false positives and eight laparoscopy failures. In the group of fertile females who escaped laparoscopy the negative appendicectomy rate was 38%. The respective rates for postmenopausal women and men were 4% and 8%. Conclusions: All women of child-bearing age suspected of having acute appendicitis should undergo diagnostic laparoscopy prior to the planned appendicectomy, regardless of the certainty of the preoperative diagnosis. This is currently the only way to reduce the negative appendicectomy rate and establish a correct diagnosis allowing prompt and appropriate treatment. In male patients and postmenopausal women one may proceed directly to emergency appendicectomy.  相似文献   
122.
初步分析了11例外伤性截瘫合并耳聋患者,指出外伤性截瘫多有慢性肾功能不全、肾性贫血等并发症。这些并发症对耳聋的发生有一定的影响,但长时间或反复使用耳毒性药物是一个不可忽视的重要因素。作者对此提出了预防耳聋的一些具体措施,可供临床参考或借鉴。  相似文献   
123.
白细胞介素—2新的功能位点及其中枢镇痛作用   总被引:2,自引:0,他引:2  
白细胞介素-2(IL-2)不仅是重要的免疫调节因子,而且还具有重要的中枢调节作用。本实验以钾离子透入引起大鼠甩尾反应为指标,发现侧脑室注射IL—2能显著提高动物痛阈,并能被纳洛酮所阻断,表示IL-2的中枢镇痛作用可能与阿片受体有关。利用基因定位突变技术获得的无免疫活性IL-2实查体仍具有中枢镇痛作用,表明IL—2分子上发挥镇痛和免疫调节作用的功能位点是相互独立的。纳洛酮能够阻断IL—2的中枢镇痛作用,而不能影响IL—2增殖CTLL-2细胞的作用,提示IL-2发挥镇痛和免疫调节作用可能通过不同的受体途径。IL-2分子中第45位Tyr残基突变为Val后,虽仍保留了免疫活性,但丧失了镇痛功能,表示45位Tyr残基是IL—2发挥中枢镇痛功能的关键残基之一。我们推测IL—2的镇痛功能位点可能在IL—2分子中第45位Tyr残基附近区域。  相似文献   
124.
The distribution of 12 different binding sites for acetylcholine, L-glutamate, GABA, 5-hydroxytryptamine, dopamine and noradrenaline was measured with quantitative receptor autoradiography in four regions of the rat basal forebrain (medial septal nucleus including vertical and horizontal limbs of the diagonal band of Broca, magnocellular preoptic nucleus, substantia innominata and basal nucleus of Meynert, ventral pallidum). L-Glutamate binding sites represent the largest portion of the analysed receptors in all regions, followed by muscarinic2, 5-hydroxytryptamine1 and GABAA receptors. Muscarinic1, dopamine1, dopamine2 and 5-hydroxytryptamine2 receptors and alpha 1-, alpha 1A- and alpha 1B-adrenoceptors represent the minor receptor populations. The largest portion of the dopamine receptors is represented by the dopamine1 subtype, and the alpha 1B subtype dominates the alpha 1-adrenoceptor group. A heterogeneity of the distribution patterns of the different receptors throughout the basal forebrain regions is found. A comparison of the patterns shows that alpha 1-adrenoceptors have a similar regional distribution to that of the muscarinic2 receptors, but both receptor types have reciprocal distributions compared with the 5-hydroxytryptamine1 receptors. The results indicate that one transmitter may exert different effects in the basal forebrain regions depending on the densities of the respective receptor subtypes. Moreover, similar or reciprocal distribution patterns of some, but not all, analysed receptors point to a non-random association (co-distribution) of the different transmitter systems in the basal forebrain regions.  相似文献   
125.
The Robert Wood Johnson Commission on Medical Education focused on evidence that, in the midst of the genetic revolution in medicine, medical students all too often are not engaged by the science component of their education. Medical education is being driven by social as well as these intellectual forces to make fundamental changes. In the USA, the rich array of scientific talent can be used more effectively, and there is a new significance for the behavioural, social, probabilistic, and information sciences. The Report discusses the general changes under way in the USA and includes examples from the eight schools in the Robert Wood Johnson Foundation's Preparing Physicians for the Future: A Program in Medical Education .
Another report explores the reasons why the general changes under way in North American medical education are difficult to bring about. Educating Medical Students is the report of the Assessing Change in Medical Education: The Road to Implementation (ACME-TRI) project of the Association of American Medical Colleges. This project, funded by the Charles E. Culpeper Foundation, explored the recurring problems in medical students' education that have been reported from the 1930s. The ACME-TRI report documents that most medical schools have not solved these recurring problems, summarizes the schools' views of the barriers to solving these problems, and identifies strategies to assist schools in overcoming or minimizing the barriers they have identified.
Together, the Robert Wood Johnson Commission report and the ACME-TRI report provide a context in which to consider the complex issues facing medical education in the 21st century.  相似文献   
126.
Q X Chen  R K Wong 《Brain research》1992,582(2):232-236
Tetraethylammonium (TEA) effects on K currents were examined on either side of the membrane of hippocampal CA1 neurons by means of whole-cell voltage-clamp recording and intracellular perfusion. Recording media contained ion channel blockers to allow the selective activation of voltage-dependent K currents which consisted of a rapidly decaying component (A-current) and a delayed component. Voltage protocols were applied to separate the A-current from the delayed component. Results show that 10 mM extracellular TEA suppressed 50 +/- 11% (S.D., n = 4) of the delayed current at different levels of depolarization but had little effect on the A-current. In contrast 10 mM TEA applied by intracellular perfusion suppressed the A-current by 42 +/- 10% (S.D., n = 4) in addition to inhibiting the delayed currently 55 +/- 15% (S.D., n = 4). Both the intracellular and extracellular actions of TEA on K currents showed no voltage- nor time-dependency. The results suggest that voltage-dependent transient current (A-current) is mediated through a separate group of ionic channels distinct from those that sustained the delayed current. Furthermore, the asymmetrical effects of intracellular and extracellular TEA on the transient current are similar to those described for the A-current in molluscan neurons. This observation supports the notion that the structure of the ion channel mediating the A-current is closely conserved across different species.  相似文献   
127.
128.
OBJECTIVE: We wished to determine whether patients with transsphenoidal pituitary herniation were at risk of developing pituitary failure. DESIGN: We followed up hypothalamic-pituitary function annually in patients with midfacial anomalies and pituitary herniation. PATIENTS: Two patients who had transsphenoidal pituitary herniation and midfacial anomalies were included and the literature was reviewed. RESULTS: Both patients became gonadotrophin, TSH and growth hormone-deficient despite neurosurgical repair. CONCLUSION: We conclude that the early diagnosis and neurosurgical repair of transsphenoidal pituitary herniation may prevent central nervous system infection and rhinorrhoea. Surgical repair may not prevent pituitary failure as was evident in both of our cases. Periodic evaluation of the hypothalamic-pituitary axis is essential to determine whether early hormonal replacement therapy is necessary.  相似文献   
129.
本文对从事京剧打击乐的55人(110耳)进行了听力调查及动态观察。利用图表进行对比分析,发现110耳中高频听力损伤89耳,占81%;语频听力损伤32耳,占29.1%;其中伴有高频耳鸣78耳,占70.9%。动态观察30人(60耳),均为永久性听阈阈移。高频听力损伤最早出现的频率是4kHz,并见典型“V”谷,符合噪声性聋的诊断。  相似文献   
130.
d,l-Norephedrine (phenylpropanolamine) which is both a demethylated analogue and a metabolite of d,l-ephedrine, is a reputed anorectic agent. In the present study the proposed most active isomer of this mixture, l-norephedrine has been assessed as a peripherally acting thermogenic agent in the isolated perfused rat hindlimb. l-Norephedrine produced a dose-dependent increase in oxygen uptake and perfusion pressure and increased lactate production. Whereas propranolol potentiated the increase in oxygen uptake and perfusion pressure produced by l-norephedrine, prazosin significantly and nitroprusside totally inhibited both of these changes. Nitroprusside also completely inhibited the increase in lactate production. We conclude that norephedrine has a hitherto unrecognized peripheral thermogenic activity in the perfused rat hindlimb resulting from its interaction with alpha 1 adrenergic receptors that control vasoconstriction in this tissue.  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