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   13647篇
  免费   680篇
  国内免费   20篇
耳鼻咽喉   205篇
儿科学   393篇
妇产科学   321篇
基础医学   2107篇
口腔科学   449篇
临床医学   1198篇
内科学   2351篇
皮肤病学   295篇
神经病学   1246篇
特种医学   690篇
外国民族医学   5篇
外科学   1961篇
综合类   47篇
一般理论   6篇
预防医学   699篇
眼科学   424篇
药学   929篇
中国医学   24篇
肿瘤学   997篇
  2023年   75篇
  2022年   70篇
  2021年   164篇
  2020年   128篇
  2019年   194篇
  2018年   333篇
  2017年   263篇
  2016年   344篇
  2015年   311篇
  2014年   389篇
  2013年   496篇
  2012年   845篇
  2011年   755篇
  2010年   418篇
  2009年   358篇
  2008年   676篇
  2007年   662篇
  2006年   625篇
  2005年   617篇
  2004年   613篇
  2003年   548篇
  2002年   581篇
  2001年   388篇
  2000年   413篇
  1999年   363篇
  1998年   94篇
  1997年   63篇
  1996年   80篇
  1992年   174篇
  1991年   153篇
  1990年   169篇
  1989年   146篇
  1988年   155篇
  1987年   158篇
  1986年   158篇
  1985年   155篇
  1984年   111篇
  1983年   110篇
  1982年   69篇
  1981年   63篇
  1979年   144篇
  1978年   79篇
  1977年   82篇
  1975年   61篇
  1974年   74篇
  1973年   84篇
  1972年   70篇
  1971年   65篇
  1970年   72篇
  1968年   71篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Clinical follow-up was obtained in 96 patients with knee complaints but normal arthroscopic findings (mean observation time, 10 months). About one-third had no symptoms at follow-up; in another third there was improvement; in the remaining third there were unchanged or worsened symptoms, and a clinical re-examination indicated that alterations in the soft tissues around the knee might explain the worsening. However, 10 patients in the last group had not only significant worsening of the knee symptoms but also severe complaints in other regions of the body and a psychosomatic factor was suspected. Most of the patients with symptoms at follow-up had significant wasting of the quadriceps muscles. Energetic exercises seem important even in patients with normal arthroscopic findings.  相似文献   
42.
43.
Zusammenfassung Videofluorographie und Kinematographie gelten derzeit als Goldstandard für die Abkl?rung von Schluckst?rungen. Methodisch bedingt ist jedoch keine überlagerungsfreie Darstellung der anatomisch wichtigen Strukturen des Pharynx m?glich, so da? bei manchen St?rungen nicht unterschieden werden kann, ob diese pathoanatomisch oder funktionell-neurogen bedingt sind. Anhand von 3 Fallbeispielen wird dargelegt, ob und in welchem Umfang die Elektronenstrahlcomputertomographie mit ihrem hohen r?umlichen und zeitlichen Aufl?sungsverm?gen (Millisekundenbereich) diese Nachteile kompensiert. Es ist uns gelungen zu zeigen, da? die vollst?ndige und symmetrische nasopharyngeale Abdichtung durch den Passavantschen Wulst und den weichen Gaumen gew?hrleistet wird. Durch die EBT konnte die genaue anatomische Lokalisation und Ausbreitung eines lateralen hypopharyngealen Pouches dargestellt werden. Durch den Nachweis einer Kompression des oberen ?sophagussphinkters durch einen kleinen zervikalen Spondylophyten konnte eine scheinbar nur funktionell bedingte Dysfunktion weiter abgekl?rt werden. Diese Beispiele zeigen, da? die Elektronenstrahlcomputertomographie die sich funktionell ?ndernde Anatomie w?hrend des Schluckens in der Transversalschicht darstellen kann, und legen es nahe, ihre Wertigkeit auf der Basis systemischer interdisziplin?rer Untersuchungen zu evaluieren.   相似文献   
44.
45.
Longitudinal investigations of basal prolactin (PRL) and prolactin concentrations following thyrotopin-releasing hormone (TRH) stimulation (delta PRL) were conducted in 17 patients with major depressive disorder and healthy subjects. The patients were being treated with either clomipramine or maprotiline. Both basal and delta PRL increased significantly after clinical response during treatment with both drugs. However, these increases in basal and delta PRL were independent of each other. Surprisingly, elevations of basal PRL were significantly greater in responders than in nonresponders, whereas those in delta PRL showed no corresponding significant difference. These results suggest that the two drugs stimulate basal and delta PRL by different mechanisms. The increases in basal prolactin levels found in responders may possibly be due to weaker inhibition of prolactin due to "down-regulated" beta adrenergic receptors and/or enhanced activity of supersensitive serotonergic receptors. Neither basal PRL nor delta PRL proved to be a predictor of therapy response. The intraindividual retest reliabilities of both basal and delta PRL in healthy subjects was so good that a single blood sample would seem to be sufficient for investigating most issues involving PRL in psychiatric patients.  相似文献   
46.
The antiparkinsonian triperiden (1; as hydrochloride Norakin) is a mixture of the stereoisomers 1a and 1b. Their identification and separation by chromatographic methods or fractional crystallisation of the tartrates is described. By means of IR- und 13C-NMR spectral data structures of 1a and 1b are proposed. Under proton catalysis 1b racemizes to 1a. In acidic solution (heating in 0.1 mol.1-1 HCl or storage in gastric juice at 37 degrees C) hydrolysis of 1 takes place and four isomeric products were observed (Z1-Z4), which arise by cleavage of the cyclopropyl moiety. The main product Z2 was identified as the 2"-hydroxy derivative. The solid drug is stable at least for 5 years.  相似文献   
47.
The afferent thalamic connections to cortical fields important for control of head movement in space were analysed by intracortical retrograde tracer injections. The proprioceptive/vestibular area 3aV, the neck-trunk region of area 3a, receives two thirds of its thalamic projections from the oral and superior ventroposterior nucleus (VPO/VPS), which is considered as the proprioceptive relay of the ventroposterior complex (Kaas et al., J. Comp. Neurol. 226:211-240, 1984). The parieto-insular vestibular cortex (PIVC, area retroinsularis, Ri) receives its main thalamic input from posterior parts of the ventroposterior complex and from the medial pulvinar. Anatomical evidence is presented that the posterior region of the ventroposterior complex is a special compartment within this principal somatosensory relay complex. The parietotemporal association area T3, mainly involved in visual-optokinetic signal processing, receives a substantial input from the medial, the lateral, and the inferior pulvinar. Dual tracer experiments revealed that about 5% of the thalamic neurons projecting to 3aV were spatially intermingled with neurons projecting to areas PIVC or T3. This spatial intermingling was distributed over small but numerous, circumscribed thalamic regions, called "common patches," which were found mainly in the intralaminar nuclei, the posterior group of thalamic nuclei, and the caudal parts of the ventroposterior complex. The "common patches" may indicate a functional coupling of area 3aV with the PIVC or area T3 on the thalamic level. In control experiments thalamic projections to the granular insula Ig and the anterior part of area 7, two cerebral structures connected with the vestibular cortical areas, were studied. Some overlap in the thalamic relay structures projecting to these areas with those projecting to the vestibular cortices was found. A quantitative evaluation of thalamic regions projecting to different cortical structures was performed by constructing so-called "thalamograms." A scheme was developed that describes the afferent thalamic connections by which vestibular, visual-optokinetic, and proprioceptive signals reach the vestibular cortical areas PIVC and 3aV.  相似文献   
48.
By means of microelectrodes, the activity of single neurons (on-center, off-center ganglion cells, latency class I and class II neurons) was recorded from the optic tract of anesthetized cats. Eyeball deformation in total darkness led fairly consistently to an activation of the on-center ganglion cells, while off-center ganglion cells were inhibited. The latency and strength of this activation or inhibition seemed to be mainly dependent on the strength of eyeball indentation and the location of the neurons relative to the point of eyeball indentation. Some on-center neurons (mostly latency class I) also exhibited a short activation at "deformation off". For comparison, the responses of retinal ganglion cells to eyeball deformation in a hydrostatically open system and to a sudden increase in the intraocular pressure (closed system) are described. The neurophysiological data are explained by the assumption that eyeball indentation leads to a nonuniform tangential stretch of the retina, which exerts a locally variable depolarization of horizontal cells. This horizontal cell depolarization leads either directly or via a feedback loop through cone pedicles to a depolarization of on-bipolars and a hyperpolarization of off-bipolars. These effects determine in turn the responses seen at the ganglion cell level. It is emphasized that eyeball deformation can be used as an independent tool in transmitter studies of the retina.  相似文献   
49.
An unusual dermatophyte was isolated from the plantar scales of a human immunodeficiency virus-positive man with tinea pedis. Morphology, physiology, and molecular data provided evidence to support the new species Trichophyton eboreum. This dermatophyte is characterized by rapid growth on common mycological media, a flat powdery off-white colony, formation of clavate microconidia, smooth- and thin-walled cylindrical or club-shaped macroconidia with two to nine cells, the presence of hook-shaped hyphae, the production of cleistothecium-like structures and spiral hyphae in older cultures, positive hair perforation, the absence of pigmentation on potato glucose agar, the absence of a requirement for vitamins, a weak positive urease reaction, no growth at 37 degrees C, resistance to 5% NaCl, resistance to fluconazole, good growth on human epidermal keratin, and the production of various enzymes on different media by the API-ZYM test. More than 5% divergence from any known species of dermatophyte was revealed by sequence analysis of the internal transcribed spacer of the rRNA gene.  相似文献   
50.
Summary 1. By means of metal-filled micropipettes the action potentials of 4 different classes of optic nerve fibers were recorded in Rana esculenta. The relationship between the angular velocity of the stimuli and the neuronal response was determined.2. If an object smaller than the excitatory receptive field (ERF) was moved through the receptive field of the different classes of retinal units the response depended on the angular velocity, contrast and size of the stimulus. The response was measured as the average impulses frequency (R) during the traverse of the ERF. Between R and the angular velocity (v) the equation R=k·v c [impulses · sec–1] was found. The exponent c was 0.5 for class 1 neurons, 0.7 for class 2 neurons, and 0.95 for class 3 neurons. In class 4 neurons the response to large stimuli increased linearly with the increase of the angular velocity, while no systematic relationship between R and v was valid for small moving stimuli (<5°)3. If the contrast or the size of the stimuli was changed the exponent c was not changed; but k depended on both parameters and on the direction of the contrast against the background. The power function was no longer valid if stimuli considerably larger than the ERF were used. The exponent c was independent of the type of the movement (linear, non-linear, irregular movement); it was also independent of the direction of the motion.4. A model of the receptive field is demonstrated. In this model an RC-filter function within the bipolar cells is assumed. The bipolar cells with different filter function activate different classes of ganglion cells. Different time constants of the bandpass filter at the bipolar cell level are the main cause for the different exponents of the power function between angular velocity and neuronal response.  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