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   9976篇
  免费   759篇
  国内免费   261篇
耳鼻咽喉   1464篇
儿科学   173篇
妇产科学   45篇
基础医学   863篇
口腔科学   1074篇
临床医学   1116篇
内科学   1714篇
皮肤病学   56篇
神经病学   788篇
特种医学   488篇
外科学   938篇
综合类   1252篇
预防医学   106篇
眼科学   173篇
药学   338篇
  6篇
中国医学   105篇
肿瘤学   297篇
  2024年   19篇
  2023年   151篇
  2022年   229篇
  2021年   356篇
  2020年   332篇
  2019年   342篇
  2018年   330篇
  2017年   347篇
  2016年   384篇
  2015年   368篇
  2014年   608篇
  2013年   591篇
  2012年   532篇
  2011年   590篇
  2010年   458篇
  2009年   464篇
  2008年   483篇
  2007年   517篇
  2006年   454篇
  2005年   428篇
  2004年   370篇
  2003年   287篇
  2002年   242篇
  2001年   224篇
  2000年   205篇
  1999年   183篇
  1998年   142篇
  1997年   150篇
  1996年   112篇
  1995年   120篇
  1994年   99篇
  1993年   96篇
  1992年   86篇
  1991年   73篇
  1990年   66篇
  1989年   77篇
  1988年   64篇
  1987年   59篇
  1986年   56篇
  1985年   60篇
  1984年   46篇
  1983年   36篇
  1982年   44篇
  1981年   34篇
  1980年   24篇
  1979年   18篇
  1978年   10篇
  1977年   11篇
  1976年   7篇
  1972年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The purpose of this study was to find out whether transesophageal pacing could be utilized for assessment of sinus node function in patients with sick sinus syndrome (SSS). In 17 patients with SSS (study group) we compared the results of sinus node tests obtained both in the basal state and after pharmacological autonomic blockade by endocavitary stimulation and, 24 hours later, by transesophageal pacing. In another group of 17 patients with SSS (control group), we compared the results obtained by two endocavitary studies. In "study group", sinus cycle length (SCL) and corrected sinus node recovery time (CSRT) did not show significant differences between the two studies both in the basal state and after autonomic blockade, whereas sinoatrial conduction time (SACT) was more prolonged during esophageal pacing (P less than 0.01). In "control group", sinus node measures did not show significant differences between the two studies. In the "study group," the following coefficients of correlation were obtained in the basal state; SCL, r = 0.65, CSRT, r = 0.57, SACT, r = 0.52 and after autonomic blockade: SCL, r = 0.95, CSRT, r = 0.62 and SACT, r = 0.53. In the basal state, the correlation for SCL and CSRT between the two studies was lower in the "study group" than in the "control group" (P less than 0.05), whereas after autonomic blockade the correlation for sinus node measures did not show significant differences between the two groups of patients. These data suggest that transesophageal study influences the autonomic tone regulating the sinus node; however, it is not responsible for important variations in sinus node measures.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
62.
In humans, electrical, bipolar, bilateral carotid sinus nerve stimulation (CSNS; impulse duration 0.35 ms) was applied, using frequencies between 10 and 110 Hz and voltages between individual thresholds and maximal amplitudes of stimulation. Ten anginal patients and two hypertensive patients were studied at an interval of up to 12 years after implantation of electrodes and a radiofrequency receiver for chronic therapeutic CSNS. In search of combinations of frequency and voltage of CSNS, eliciting largest ("optimal") depressor responses of blood pressure and heart rate in the individual patient, Rechenberg's evolution strategy was applied. This strategy simulates mutation and selection of biological evolution. In each patient and on each test stimulation, a value of quality was computed from actual heart rate and blood pressure values as a selection criterion for the strategy. Either responses to uninterrupted CSNS were investigated, while stimulation parameters were adjusted every 3 min, according to the strategy, or responses to 3 min of CSNS after a change in stimulation parameters were compared to intercalated 3-min control periods. In each patient, one or more combined settings of frequency and voltage elicited "optimal" responses. In principle, "optimal" CSNS frequencies ranged between 35 and 105 Hz with large interindividual differences. Due to chronic implantation of electrodes and technical features of radiofrequency transmitted stimulation energy, interindividually different voltages led to an optimal response to CSNS. Also according to the present results, the frequency of CSNS has to be determined individually. It is concluded that the evolution strategy was applied successfully, because voltage and frequency settings leading to "optimal" responses were found within 90-180 min, whereas intraindividual systematic investigations would not be feasible due to their necessarily very long duration. So far, only short-term responses have been evaluated. A broader use of the strategy in other applications is encouraged, as for example in pacemaker optimization and especially in functional electrostimulation.  相似文献   
63.
Rhinosinusitis is diagnosed frequently in clinical practice, but the term may in fact encompass a wide spectrum of diseases. Inflammation of the nasal and sinus mucosa can arise from various causes and lead to different sequelae. Moreover, the term rhinosinusitis is more accurate than sinusitis. Causes range from a viral infection leading to the common cold to an invasive, fungal infection. An accurate diagnosis is important because effective therapy is available if recognized early and if specific therapy is used. Importantly, there is a close relationship between upper and lower airway disease and each have unique structural and functional differences that make an understanding of rhinosinusitis important not only for upper airway disease, but also for the management of asthma. All too often, rhinosinusitis becomes chronic and this becomes a challenge because medical therapy may not be sufficient to control disease. Finally, we should note that the differential diagnosis of rhinosinusitis is extensive and physicians should place heavy emphasis not only on the history, but also on appropriate imaging studies. A normal exam does not rule out the possibility or rhinosinusitis. Finally, we should emphasize that effective treatment is dependent on the etiology of the symptoms but also dependent on whether it is acute or chronic.  相似文献   
64.
Tentorial sinus     
Summary The authors report a case of tentorial sinus draining the telencephalic and diencephalic tributaries of the basal vein. Dorsally the sinus joined the straight sinus and later the confluence of the sinuses. Attention should be paid to this normal variation whenever a transtentorial surgical approach is considered.
Sinus de la tenteAspect radiologique et anatomique, à propos d'un cas
Résumé Les auteurs rapportent un cas de sinus de la tente du cervelet drainant les affluents télencéphaliques et diencéphaliques de la veine basale. En arrière, le sinus rejoint le sinus droit puis le torcular. Une attention particulière pré-opératoire devrait être accordée à la mise en évidence de cette variété lorsqu'une approche transtentorielle est discutée.
  相似文献   
65.
对46例(92侧)12~40周胎儿标本的上颌窦,行冠状切,HE染色,光镜观察:(1)原始上颌窦在胚胎第20~22周由原始筛漏斗底部扩展而成,上颌窦位于钩突和中鼻道外侧壁的外侧,窦腔与眼眶之间的骨板最薄,且骨化较晚.(2)窦口位于上颌窦的顶部(壁),随胎龄增长,”钩突角”变小.向外下的筛漏斗渐近水平位.(3)出生时,上颌窦大小约3.0×5.0×6.5mm.窦内粘膜上皮细胞呈立方形或矮柱状,其纤毛稀疏,,固有膜增厚、疏松,内含极少量血管和腺体.结果表明:出生时,上颌窦虽已出现,但粘膜厚,窦腔小,且与眼眶的毗邻关系密切,上颌窦粘膜的组织结构与鼻腔粘膜的结构有所不同.  相似文献   
66.
Gaps and fragmentation of the superficial lymph node cortex are considered to provide intranodal shunt flow between the afferent and efferent vessels. Using serial sections of 205 nodes obtained from 27 donated cadavers more than 70 years of age, we examined the histological architecture of the abdominal and pelvic nodes in elderly Japanese. Secondary follicles were rare in the specimens. Cortex gaps were, to a greater or lesser degree, found in all nodes. We classified these nodes into three types according to how often the gap occurred. Type 1 nodes, with a relatively complete shield for the afferent lymph, were most frequently found in gastric nodes, whereas type 3 nodes, with numerous gaps, were often observed in the colic, para-aortic and pelvic nodes. The type 3 nodes showed a specific architecture characterized by a fragmented superficial cortex, three-dimensionally assembled cords and a common sinus between them. Primary follicles were located in the assembled cord structures as well as at the superficial cortex. Irrespective of the type, B and T lymphocyte areas were intermingled in the cortex-like areas. The present results reveal region-specific histological heterogeneity in aged human visceral nodes. Due to increased surface areas, the type 3 architecture seemed to accelerate systemic immunity rather than act as a local barrier in the para-aortic and pelvic nodes, which are located centrally along the lymphatic drainage routes. However, thick trabeculae often seemed to develop in the type 3 sinus to decrease nodal function with aging.  相似文献   
67.
Summary The present study was performed on axial and coronal CT scans of 100 patients, most of whom were affected by nasal polyposis. Five observers had to analyse the radiograms and answer a questionnaire including the following items: presence of a supraorbital recess; identification of anterior and posterior ethmoidal canals; dehiscences in the lamina papyracea; pneumatized middle turbinate; presence of a spheno-maxillary plate; presence of Haller's cells; presence of Onodi's cells; relationships of the optic canal; relationships of the internal carotid artery; relationships of the maxillary nerve; relationships of the vidian nerve; level difference between the ethmoid roof and nasal vault; depth of the sphenoethmoidal recess. The data obtained were compared with those drawn from anatomical studies. The fair agreement between them proves the value of CT as an alternative method for studying paranasal sinuses anatomy.
Anatomie radiologique des variations du labyrinthe ethmoïdal et du sinus sphénoïdal et leurs conséquences chirurgicales
Résumé Cette étude a été réalisée sur 100 patients dont la plupart présentait une polypose nasale étudiée en coupes T D M axiale et coronale. Cinq lecteurs ont revu les clichés et répondu au questionnaire suivant: présence d'un récessus supra orbitaire; identification des canaux ethmoïdaux antérieur et postérieur; déhiscence de la lame papyracée; pneumatisation du cornet moyen; présence d'un plateau sphéno maxillaire; présence de cellules de Haller; présence de cellules d'Onodi; rapports du canal optique; rapports de l'artère carotide interne; rapports du nerf maxillaire; rapports du nerf vidien; dénivelé entre le toit ethmoïdal et le toit nasal; profondeur du récessus sphéno-ethmoïdal. Les données obtenues ont été comparées avec celles provenant de travaux anatomiques. La concordance acceptable entre les deux démontre la valeur du scanner comme méthode d'étude alternative de l'anatomie des sinus para nasaux.
  相似文献   
68.
目的:探讨心肌梗死(心梗)患者窦性心律震荡检测的临床意义。方法:测定24小时动态心电监测的170例心梗患者和116例正常人室性早搏(室早)后的震荡初始(TO)和震荡斜率(TS)值及平均值,并进行对比分析。结果:心梗患者室早后的TO值明显高于对照组、鸭值明显低于对照组(P〈0.05和P〈0.01),TO和/或TS异常组死亡率明显高于TO和鸭均正常组(P〈0.001)。结论:心梗后患者窦性心律震荡现象减弱或消失时,其猝死的发生率增高,及时检测心梗患者室早后的TO和TS值,对发生猝死的高危患者的检出、危险度分层以及对其进行干预治疗都有重要的临床意义。  相似文献   
69.
We report two cases of acquired toxoplasmic lymphadenitis, one with toxoplasmic cysts and the organisms of Toxoplasma gondii and the other with the organisms only. These cysts and organisms were observed in paraffin-embedded sections, touch smears and ultrathin sections for electron microscopy. Touch smears were especially valuable for the quick and accurate diagnosis of toxoplasmic lymphadenitis. We also studied immature sinus histiocytosis (ISH) in these cases. The predominant cells of ISH were confirmed to be B lymphocytes immunohistochemically, the majority being positive for polyclonal surface IgM. ISH was observed in the perifollicular and paracortical areas surrounding post-capillary venules (PCV), whereas the sinuses were only partially involved.  相似文献   
70.
目的:报道1例偶然发现的右侧永久性三叉动脉形态、特点,并进行文献复习。方法:利用显微解剖对此例永久性三叉动脉的起源、走行、分支、分布、与后循环连接关系、以及相关动脉解剖特点等进行了研究。结果:此例永久性三叉动脉与脑膜垂体干共干起源于颈内动脉海绵窦段,于展神经外侧进入后颅窝,分支与基底动脉和小脑上动脉吻合,其终末支之一延续为同侧的小脑下后动脉,此动脉与三叉神经关系密切,分支分布于脑干和小脑。结论:永久性三叉动脉与后循环关系复杂,广泛参与正常脑组织供血。  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