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   5191篇
  免费   284篇
  国内免费   116篇
耳鼻咽喉   76篇
儿科学   104篇
妇产科学   71篇
基础医学   706篇
口腔科学   258篇
临床医学   420篇
内科学   656篇
皮肤病学   71篇
神经病学   459篇
特种医学   208篇
外科学   699篇
综合类   562篇
预防医学   331篇
眼科学   133篇
药学   397篇
中国医学   220篇
肿瘤学   220篇
  2024年   13篇
  2023年   91篇
  2022年   145篇
  2021年   221篇
  2020年   137篇
  2019年   137篇
  2018年   156篇
  2017年   160篇
  2016年   155篇
  2015年   142篇
  2014年   286篇
  2013年   334篇
  2012年   265篇
  2011年   257篇
  2010年   200篇
  2009年   207篇
  2008年   212篇
  2007年   195篇
  2006年   192篇
  2005年   141篇
  2004年   160篇
  2003年   127篇
  2002年   99篇
  2001年   104篇
  2000年   77篇
  1999年   89篇
  1998年   84篇
  1997年   82篇
  1996年   49篇
  1995年   57篇
  1994年   51篇
  1993年   67篇
  1992年   67篇
  1991年   51篇
  1990年   66篇
  1989年   58篇
  1988年   59篇
  1987年   44篇
  1986年   39篇
  1985年   77篇
  1984年   71篇
  1983年   36篇
  1982年   58篇
  1981年   55篇
  1980年   50篇
  1979年   36篇
  1978年   30篇
  1977年   25篇
  1976年   30篇
  1975年   15篇
排序方式: 共有5591条查询结果,搜索用时 0 毫秒
41.
We performed an anatomic study of the right atrioventricular valve in children under one year of age using a conservative method of dissection of the heart valve. The main aspects studied were the number of cusps and their morphometric characteristics, such as the width of the base and the depth of the cusps. Other parameters studied were the number of papillary muscles, number of tendinous cords, and diameter of the fibrous ring and the last one were divided in three regions, anterior, posterior and septal for localization of cusps. Our results showed that the number of cusps varied from two to four. Three cusps was the commonest finding and the fourth cusp, if present, was classified as anterolateral in location. The anterior and septal cusps had bases bigger than those of the posterior and anterolateral cusps; the septal cusp was deeper than the others; and the number of tendinous cords was greater for the anterior and septal cusps than for the posterior and anterolateral cusps. In addition, the posterior region showed great variability: in 35.7% it was occupied by undeveloped valve tissue and the posterior valve in these cases was located anteriorly.  相似文献   
42.
目的:探讨相关解剖定位标志在经单鼻孔-蝶窦入路垂体腺瘤显微外科手术中的应用。方法:62例垂体腺瘤经单鼻孔-蝶窦入路显微手术,术中根据蝶嵴、蝶窦开口、蝶窦中隔、鞍底隆凸等解剖标志进行定位。结果:蝶嵴是术中确认手术入路中线的可靠标志,蝶窦开口是蝶窦前壁的重要标志,鞍底隆凸可作为蝶窦腔内鞍底定位标志。62例术中依靠相关解剖标志,均准确定位蝶窦及鞍底,未出现偏差。肿瘤全切除52例,次全切除5例,大部分切除4例。1例部分切除,无死亡病例。结论:熟悉相关解剖标志,有助于该术式的准确定位,从而安全实施手术。  相似文献   
43.
Summary The postmortem stability of cell antigens has hardly been studied. Using monoclonal antibodies (mabs) we examined the postmortem detectability of lymphocyte surface antigens in different lymphoid organs by comparing two sensitive, immunohistological staining procedures.To quantify the probable degree of autolysis of the tissues a score system was applied by taking into consideration the postmortem age as well as the core temperature of the corpses.The antigens examined generally proved to be very resistant to autolytic influences. Differences were found when comparing different mabs and with regard to the type of lymphoid tissue. The loss of immunohistological reactions was most extensive in the spleen whereas tonsils showed almost no qualitative alterations in staining patterns. Reactivity of mabs with postmortem tissues decreased in the following order: Dako CD22 and anti-Leu 4, anti-Leu 3a, anti-Leu 7, Dako T8. The mabs anti-Leu 7 and Dako-T8 frequently failed to demonstrate their respective antigens but no correlation between the loss of staining and the degree of autolytic decomposition (our score) could be detected.In general, postmortem tissues as well as tissues shock frozen after delay are suitable for qualitative immunohistology of those cells characterized by the mabs applied.The APAAP-method proved unequivocally to be the superior staining technique.  相似文献   
44.
Summary The angular points are the ligamentous and tendinous structures that reinforce the posteromedial and posterolateral capsule of the knee and share in fixation of the posterior horns of the menisci. They are often damaged in acute injuries and this is usually associated with ruptures of the cruciate and collateral ligaments and may add to the degree of laxity. We describe the normal appearance of these structures in terms of the sectional anatomy, correlated with the lesional appearances of complete and incomplete ruptures and associated meniscal detachments as shown by clinical testing and arthrotomy findings.
IRM des points d'angle du genou : bases anatomiques et applications aux genoux traumatiques
Résumé Les points d'angle sont des structures ligamentaires et tendineuses qui renforcent la capsule postéro-médiale et postéro-latérale et participent à la fixation des cornes postérieures des ménisques. Leurs lésions, fréquentes au cours des traumatismes aigus, sont généralement associées à des ruptures des ligaments croisés et des ligaments collatéraux et peuvent être source d'une aggravation de la laxité. Nous rapportons, en corrélation avec l'anatomie en coupe, l'aspect normal de ces structures, et en corrélation avec les données de l'arthrotomie et du testing les aspects lésionnels observés au cours des traumatismes : ruptures complètes, incomplètes et désinsertions méniscales associées.
  相似文献   
45.
Despite the frequent use of fine‐needle aspiration, core biopsy and surgery, postoperative spindle cell nodule (PSCN) is a rare pathological complication that may be diagnostically treacherous. Presented herein is the case of a 52‐year‐old woman who developed a 7 mm mammary nodular lesion 66 days after removal of an area of columnar cell hyperplasia involving cellular and architectural atypia, performed with the Mammotome Breast Biopsy System. The lesion was highly cellular and composed of intersecting fascicles of plump spindle cells with blunt‐ended elongated nuclei and nucleoli easily visible. Interspersed mononuclear cells and hemosiderin‐laden macrophages were evident. PSCN is a reactive, benign myofibroblastic proliferation. Differential diagnosis includes benign and malignant spindle cell lesions of the breast. Recognition of this reactive lesion will avoid overdiagnosis of spindle cell malignant tumor. Attention to clinicopathological and histological features should result in accurate recognition of this lesion.  相似文献   
46.
ABSTRACT  The technique for gavage administration to rat nurslings was improved to allow determination of the direct effects of chemical substances in the nurslings. Rat neonates were treated with distilled water from postnatal day 1 through 20 using this technique. The viability of neonates during the administration period was comparable to that of untreated neonates. No adverse effects of this technique on the development of neonates were found, and no histological alterations of the esophagus or pharynx. Therefore, we conclude that use of our improved gavage administration method will contribute to ensuring successful neonatal development and thus allowing accurate assessment of the toxicological effects of test compounds on rat nurslings.  相似文献   
47.
Seasonal changes in blood plasma biochemistry of siraz Capoeta capoeta umbla were determined throughout 1 year. In the present study, while the highest values for glucose and globulin were found in winter, the values for increased activities of total protein, albumin, calcium, sodium levels, albumin/globulin ratio, lactate dehydrogenase, and alkaline phosphatase were determined in summer. We determined that blood biochemistry values of siraz, which were positively affected by water temperature and pH, except glucose and globulin. Glucose and globulin were negatively affected by water temperature and pH. Consequently, it was concluded that the seasons are key factors when blood parameters are used as biomarkers for environmental alterations. It is difficult to define the most important factors affecting seasonal changes of blood biochemistry in fish.  相似文献   
48.
胸部体表导纳变化与胸腔中血管导纳变化的关系   总被引:1,自引:1,他引:1  
目的:探讨胸部体表导纳变化与胸腔中血管导纳变化的关系。方法:根据导纳与阻抗互为倒数的关系,导出胸部体表导纳变化公式,并用模型实验证明。结果:单根血管在胸部体表引起的导纳变化与血管本身的导纳变化和基础导纳的比值成正比,与血管的长度和胸部体表两检测电极之间的基础导纳成正比,与血管到两检测电极连线的距离成反比;多根血管在胸部体表共同引起的导纳变化等于各血管单独在胸部体表产生的导纳变化的代数和,即在电导纳图测量中导纳变化遵从标量迭加原理。结论:本文结果可为心导纳图的波形重建奠定理论基础。  相似文献   
49.
Summary We set out to demonstrate whether changes in plasma volume, haematocrit and some important blood constituents occurred after swimming 100 m and 800 m, as well as monitoring the duration of these changes. We measured exercise-induced changes in concentration of plasma constituents in eight subjects, and determined the expected effects of haemoconcentration on these constituents. We also investigated the different biochemical responses occurring after maximal exercise (100 m), as compared to submaximal exercise (800 m). The haematocrit increased significantly after the 100 m swim and to a lesser extent after the 800-m swim, returning to basal levels within 30 min. The plasma volume decreased by 16% on completion of the 100 m and by 8% on completion of the 800 m. The blood lactate concentration increased 15-fold and 10-fold after the 100-m and 800-m swims respectively. The plasma potassium concentration increased significantly immediately on completion of the 100-m swim, then decreased significantly at 2 1/2 and 5 min post-exercise, returning to near-basal values at 30 min. The potassium concentration measured after the 800-m event did not differ significantly from basal levels, however the measured concentrations were significantly lower than the concentrations expected on the basis of haemoconcentration. The plasma sodium concentrations measured after both 100-m and 800-m swims were significantly increased. However, calculations correcting for haemoconcentration showed significant losses in toal circulating sodium. Our study demonstrates marked changes in plasma volume and certain blood constituents after maximal intensity swimming, and less marked changes after submaximal exercise. We also demonstrated the importance of taking the effects of haemoconcentration into account when evaluating changes in concentration of plasma constituents.  相似文献   
50.
Summary Investigation of the behaviour of the renal Juxtaglomerular apparatus in 19 patients with malignant hypertension has shown that in kidneys fixed immediately after operation the Juxtaglomerular granulation index is twice as high as in autopsy kidneys. The formation of renin by the epitheloid cells begins with the appearance of osmiophilic substances in the region of the endoplasmic reticulum. The first stages of granule formation are small rhomboid particles in the Golgi cisternes, which aggregate to form bigger round or polymorphic granules in the Golgi area.In pathological conditions the substances synthesized may be set free and become active locally as a result of fibrinoid necrosis of the vascular wall. The rate of production is increased firstly by forcing rhe production of active agents in the preexistent epitheloid cells, secondly by transformation of the so-called bivalent cells and finally, by cell division.In accelerated hypertension the production of renin also takes place in nephrons whose glomeruli, tubules and macula densa, are damaged. There is a correlation between blood pressure elevation and the Juxtaglomerular granulation index.
Zusammenfassung Untersuchungen über das Verhalten des juxtaglomerulären Zellkomplexes der Niere bei 19 Patienten mit maligner Hypertonie haben folgendes ergeben: In operativ gewonnenen und sofort fixierten Nieren ist der juxtaglomeruläre Granulationsindex doppelt so hoch wie in Nieren aus dem Sektionsgut. Die Reninbildung der epitheloiden Zellen beginnt mit dem Auftreten osmiophiler Substanzen im Bereich des endoplasmatischen Reticulums. Kleine rhomboide Gebilde in Golgizisternen sind Vorstufen von reifen Sekretgranula, die sich im Golgifeld zu größeren runden oder vielgestaltigen Sekrettropfen zusammenlagern.Unter pathologischen Bedingungen können infolge fibrinoider Gefäß- wandnekrosen Sekretsubstanzen lokal frei und lokal wirksam werden. Vermehrte Arbeitsleistung erfolgt zunächst durch Forcierung der Sekretproduktion in den präexistenten epitheloiden Zellen, sodann durch Transformierung sogenannter bivalenter Zellen und schließlich durch Zellneubildungen.Reninproduktion findet bei akzelerierter Hypertonie auch in solchen Nephronen statt, deren Glomerula und Tubuli samt Macula densa strukturell geschädigt sind. Es besteht eine Korrelation zwischen Höhe des Blutdruckes und Höhe des Granulationsindex.
  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