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   35737篇
  免费   2205篇
  国内免费   157篇
耳鼻咽喉   367篇
儿科学   953篇
妇产科学   693篇
基础医学   5193篇
口腔科学   999篇
临床医学   3243篇
内科学   7987篇
皮肤病学   922篇
神经病学   4056篇
特种医学   1177篇
外国民族医学   3篇
外科学   3736篇
综合类   217篇
一般理论   16篇
预防医学   2619篇
眼科学   658篇
药学   2387篇
中国医学   107篇
肿瘤学   2766篇
  2023年   276篇
  2022年   570篇
  2021年   1033篇
  2020年   653篇
  2019年   913篇
  2018年   990篇
  2017年   744篇
  2016年   893篇
  2015年   1037篇
  2014年   1288篇
  2013年   1624篇
  2012年   2648篇
  2011年   2778篇
  2010年   1516篇
  2009年   1316篇
  2008年   2260篇
  2007年   2226篇
  2006年   2138篇
  2005年   2054篇
  2004年   1887篇
  2003年   1690篇
  2002年   1485篇
  2001年   596篇
  2000年   576篇
  1999年   523篇
  1998年   309篇
  1997年   270篇
  1996年   241篇
  1995年   197篇
  1994年   193篇
  1993年   144篇
  1992年   341篇
  1991年   282篇
  1990年   283篇
  1989年   225篇
  1988年   187篇
  1987年   179篇
  1986年   175篇
  1985年   166篇
  1984年   127篇
  1983年   94篇
  1982年   62篇
  1981年   59篇
  1980年   59篇
  1979年   99篇
  1977年   51篇
  1974年   52篇
  1973年   60篇
  1972年   72篇
  1971年   50篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Short or long term diabetes in female rats produced remarkable activation of aminopyrine N-demethylation, inhibition of oestrone and p-nitrophenol glucuronidation and no changes in morphine UDP-glucuronyltransferase activity in vitro. Km and Vmax for these reactions were determined. Insulin treatment partially antagonized diabetes activation of aminopyrine N-demethylation: it restored decreased UDP-glucuronyltransferase activities for oestrone and p-nitrophenol only in long term and short term diabetes, respectively. Insulin also markedly inhibited morphine glucuronidation. Triton X-100 also displayed a differential pattern of activation for the glucuronidation reactions in liver microsomes of diabetic rats. Results suggest that diabetes in female rats may increase the actual amount of enzyme protein for aminopyrine metabolism and to decrease that for oestrone and p-nitrophenol.  相似文献   
62.
Wilson's disease is a hereditary autosomal recessive disorder of copper metabolism. The corresponding gene locus has been localized on the long arm of chromosome 13. Three different clinical variants of the disease can be distinguished: hepato-cerebral, abdominal/hepatic, and central nervous type. The heterogeneity of symptoms can cause problems in differential diagnosis, especially when another concordant disorder can also explain the pathogenesis of symptoms. The case report of a young man who suffered from brainstem contusion demonstrates the possibilities of misinterpretation because presenting symptoms could be attributed either to traumatic brain injury followed by adjustment disorder or Wilson's disease. Clinical signs included leftsided hemiparesis, bilateral gaze direction nystagmus, marked dysarthria with consecutive pervasive mutism, choreo-athetoid movements, spasmodic torticollis and diplopia dependent on gaze direction. Slit lamp examination showed Kayser-Fleischer's corneal ring. EEG- and computer assisted tomography investigations revealed non-specific findings. The patient was treated with D-Penicillamine. Alternative treatment with oral zinc preparations is discussed.
Zusammenfassung Beim Morbus Wilson handelt es sich um eine autosomal rezessiv vererbte Störung des Kupferstoffwechsels. Der Genort konnte auf dem langen Arm des Chromosoms 13 lokalisiert werden. Klinisch können aufgrund ihrer Symptomatik drei Verlaufsformen (hepato-zerebraler, abdominalhepatischer und zerebraler Typ) unterschieden werden. Die Vielfalt der Symptome kann differentialdiagnostische Schwierigkeiten bereiten. Das Beispiel eines jungen Mannes mit einer traumatischen Hirnstammkontusion zeigt, wie die Diagnose der hepato-lentikulären Erkrankung dadurch erschwert wurde, daß die Pathogenese der Symptome durch die Hirnstammkontusion und darauf folgende Anpassungsstörungen erklärt worden war. Die Symptomatik bestand aus linksseitiger Hemiparese, lateralem Blickrichtungsnystagmus, Dysarthrie mit nachfolgendem universalem Mutismus, choreo-athetodischen Bewegungsstörungen, Torticollis spasmoidicus und blickrichtungsabhängigem Auftreten von Doppelbildern. Bei der Spaltlampenuntersuchung stellte sich der Kayser-Fleischer Ring dar. EEG- und computertomographische Untersuchungen erbrachten nur unspezifische Befunde. Die Behandlung erfolgte mit D-Penicillamin. Die alternative Behandlung mit oraler Gabe von Zinksalzen wird diskutiert.

Résumé La maladie de Wilson est une affection héréditaire autosomale recessive concernant le métabolisme cuivré. Le locus du gène a été situé sur le bras long du chromosome 13. Du point de vue clinique on distingue trois formes symptomatologiques: le type hepato-cérébral, hepato-abdominal et cérébral. La diversité des signes cliniques peut poser des problèmes de diagnostic différentiel, car d'autres affections peuvent se présenter avec cette même Symptomatologie. Nous rapportons ici l'exemple d'un homme jeune, porteur d'une maladie de Wilson et victime d'une contusion traumatique du tronc cérébral, dont les signes cliniques ainsi que les troubles du comportement pouvaient été autant rapportés à la contusion du tronc cérébral qu'à l'affection métabolique.La Symptomatologie comprenait une hemiparesie gauche, un nystagmus lateralisé, une dysarthrie avec mutisme secondaire universel, des mouvements choréo-athétosiques, un torticolis spasmodique et une diplopie dépendante de la direction du regard. L'examen à la lampe à fente permettait à mettre en evidence un anneau de Kayser Fleischer. L'EEG et le scanner cérébral ne montraient pas d'anomalies specifique.Le traitement a consisté en l'administration de D-Penicillamine. Traitment alternative avec les sels de zinc est discuté.
  相似文献   
63.
Between 1982 and 1988, 111 elderly women with breast cancer but without clinical involvement of the axillary lymph nodes underwent wide lumpectomy in a Day Hospital regimen at the National Cancer Institute of Milan. The patients ranged in age from 70 to 92 years (median, 79). An adjuvant treatment was carried out in all but 9 cases: tamoxifen only in 84 cases, tamoxifen plus radiotherapy in 6 cases, radiotherapy alone in 12 cases. The median duration of follow-up was 44 months (range, 30-109 months). Four patients (3.6%) were lost to follow-up. In the remaining 107 patients, 10 local-regional relapses (9.1%) and 7 distant metastases (6.5%) occurred. Six patients died from the disease, 14 from unrelated conditions. This retrospective study showed that selected elderly patients with breast cancers can be treated successfully under local anesthesia on an outpatient basis. The treatment guarantees local control of the disease, meets the favor of elderly women and consequently improves their quality of life.  相似文献   
64.
Five hundred six consecutive cases of ductal infiltrating carcinoma of the breast (T1-T2,N0,M0) were evaluated to define the frequency of peritumoral lymphatic invasion (PLI) and verify its possible prognostic significance. Histologically, PLI was characterized by the presence of neoplastic emboli within vascular lumina lined by recognizable endothelial cells, adjacent to but outside the margins of the carcinoma. In routine histopathologic assessment the frequency of PLI was 68% whereas in a randomly selected group of 234 reviewed cases the frequency rose to 20%. Patients with routinely evaluated PLI had a worse prognosis than those without PLI with reference both to disease-free survival (P = 0.0001) and total survival rates (P = 0.0001). The difference for local recurrences was prognostically highly significant (P = 0.0001) and also significant for the development of metastases (P = 0.0576). In the reviewed material the difference in prognosis between PLI-positive and PLI-negative cases was not confirmed for total survival whereas the significance for the disease-free interval persisted. The assessment of PLI, carried out following strict histopathologic criteria, appears to select a group of node-negative breast cancer patients who have an increased risk of recurrences and might benefit from a treatment different from that reserved for node-negative and PLI-negative patients.  相似文献   
65.
Summary Neoplastic invasion of the brain parenchyma results in a disruption of the ultrastructure of the blood vessel walls such that serum proteins extravasate into the surrounding tissue, resulting in cerebral edema. The structural changes involved are not well understood, since the pores through which serum constituents pass (permeability routes) in normal barrier vessels and in tumor vessels where the barrier is compromised, have not been extensively explored. In this study we investigate the ultrastructure of human brain microvessels in biopsied samples of control brain tissue and five glioblastoma multiforme tumors. Electron micrographs of a total of 78 vessels were analysed with computer assisted morphometry for ultrastructural evidence of permeability routes. Fenestrations in the endothelium were not seen. Pinocytotic vesicle number and arrangement did not differ significantly from that seen in control brain vessels. Interendothelial junctions with enlarged distensions (which may represent sections through transendothelial channels) were seen in some vessels from most tumors but not in control barrier vessels. In addition, large gaps in the endothelial layer were seen in less than two percent of tumor vessels. In conclusion, glioblastoma multiforme vessels in this study show subtle alterations in vessel morphology from that seen in controls. We suggest that the high vascular permeability and resultant brain edema seen in glioblastoma multiforme tumors is likely due to the presence of channels through interendothelial junctions, and rare but large breaks in the endothelial wall.  相似文献   
66.
We investigated non-rapid eye movement (non-REM) sleep in patients with newly diagnosed Parkinson's disease (PD) who had never previously received dopaminergic medication. There were no significant differences in the conventional sleep parameters between de novo patients with PD and a healthy control group, but the length of stage 1 sleep and the number of awakenings increased significantly upon administration of dopaminergic drugs. Analyzing the quantitative electroencephalogram (EEG), we observed a significant reduction in the low-delta frequency range and a nonsignificant increase in the sigma frequency range in de novo patients with PD. The dopaminergic medication also nonsignificantly reduced the low-delta and sigma frequencies, the latter to the level of the controls. Possible mechanisms that may account for the observed differences are discussed. It is suggested that Parkinson's disease as well as the application of dopaminergic drugs exerts a desynchronizing effect on the sleep EEG that is reflected in a disruption of sleep continuity.  相似文献   
67.
This study was performed to see whether or not protection of the endothelial cells contributes to the antithrombotic effects of heparin. New Zealand albino rabbits were subjected to jugular vein stasis by single caudal ligation for 2 h. Three treatments were given: saline (control group), heparin (0.2 mg/kg) 5 or 45 min before ligature of the vein. Groups of 6-8 animals were killed at 0, 5, 15, 30 and 120 min. The following parameters were determined: (1) involution and damage of the endothelial cells by scanning and transmission electron microscopy; (2) incidence and weight of thrombi in the lumens of the veins after 2 h stasis, and (3) effects of heparin on APTT and anti-Xa activity. In the control group, stasis caused a considerable involution of the endothelial cells in the first 30 min, followed by fibrin deposition and thrombus generation. Heparin strongly reduced the damage to the endothelial cells, with very evident protection of the cell membranes, and prevented thrombus generation: there were significant decreases in both incidence and weight of thrombi. These effects of heparin were evident both shortly after (maximal anticoagulant effect) and long after (no anticoagulant effect) pretreatment. We think that, under the experimental conditions we used, heparin prevented venous thrombosis at least partially by protection of the endothelial cells, through unknown mechanisms.  相似文献   
68.
The immunohistochemical occurrence of the neurotrophin (NT) proteins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-4 (NT-4), and neurotrophin-3 (NT-3) is shown in the pre-term newborn, infant, and adult human post-mortem cerebellum. The NT-like immunoreactive structures were unevenly distributed and showed regional differences among cerebellar lobules and folia. NGF-, NT-4-, and NT-3-positive neuronal perikarya were observed in all specimens examined. At variance with the other neurotrophins, the BDNF antiserum labelled neuronal cell bodies only in newborn life and infancy, as well as extensive nerve fibre systems, whose density increased with age. The NT-antibodies, tested by Western blot on human cerebellum homogenates, revealed immunoreactive bands corresponding to proteins of heterogenous molecular weight. The results obtained provide a first demonstration of the tissue localization of the NTs in the human cerebellum from perinatal to adult age, thus suggesting their involvement in the development, differentiation and maintenance of the cerebellar connectivity. Codistribution of the four NTs or sets of them was observed in cortical and deep nuclei neurons. Multiple trophic roles for NTs, encompassing the classic target-derived and local mechanisms of support, are envisaged as significant in development, differentiation, and maintenance of the human cerebellar connectivity.  相似文献   
69.
We have investigated the ontogeny of MHC class I, class II, CD45, and macrophage antigens in wholemounts of normal human fetal retina at 10–25 weeks gestation (WG) using monoclonal antibodies and immunogold histochemistry. MHC class I antigens were expressed on retinal vascular endothelial cells and provided a useful marker of vessel organization from 14–25 WG. Microglial cells expressed immunoreactivity to MHC class I, class II, and CD45 antigens from 10 WG (pre-vascularization) and macrophage S22 (Mac S22) antigen from 14 WG (post-vascularization), although none of the antigens tested were detected on neuronal or macroglial elements. Microglia expressing MHC, CD45, and macrophage antigens occurred in both ramified and rounded forms with no close correlation being observed between morphology and antigenicity. The numbers of immunoreactive cells labeled with each of the four markers increased steadily throughout gestation in all specimens studied. Equivalent numbers of microglia expressed MHC class I, class II, and CD45 antigens in retinae at similar gestational ages; however, our data indicate that microglia expressing Mac S22 antigen comprise approximately 40% or less of the population of MHC and CD45-immunoreactive cells during development. Topographical analyses suggest that MHC class I, class II, and CD45-positive microglia enter the retina from both the peripheral retinal margin and the optic disc from at least 10 WG; Mac S22-positive cells appear in association with the development of the retinal vasculature and enter the retina via the optic disc after 14 WG. © 1995 Wiley-Liss, Inc.  相似文献   
70.
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