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   16071篇
  免费   795篇
  国内免费   57篇
耳鼻咽喉   232篇
儿科学   437篇
妇产科学   338篇
基础医学   2614篇
口腔科学   386篇
临床医学   1420篇
内科学   3079篇
皮肤病学   385篇
神经病学   1673篇
特种医学   871篇
外国民族医学   3篇
外科学   2137篇
综合类   69篇
一般理论   4篇
预防医学   786篇
眼科学   370篇
药学   1025篇
中国医学   92篇
肿瘤学   1002篇
  2023年   67篇
  2022年   136篇
  2021年   245篇
  2020年   172篇
  2019年   244篇
  2018年   308篇
  2017年   213篇
  2016年   317篇
  2015年   392篇
  2014年   490篇
  2013年   608篇
  2012年   936篇
  2011年   942篇
  2010年   616篇
  2009年   618篇
  2008年   875篇
  2007年   894篇
  2006年   976篇
  2005年   942篇
  2004年   911篇
  2003年   880篇
  2002年   769篇
  2001年   228篇
  2000年   193篇
  1999年   198篇
  1998年   228篇
  1997年   147篇
  1996年   110篇
  1995年   116篇
  1994年   107篇
  1993年   86篇
  1992年   105篇
  1991年   84篇
  1990年   85篇
  1989年   77篇
  1988年   91篇
  1987年   87篇
  1986年   67篇
  1985年   84篇
  1984年   72篇
  1983年   70篇
  1982年   56篇
  1980年   49篇
  1979年   53篇
  1978年   61篇
  1977年   50篇
  1954年   48篇
  1932年   46篇
  1930年   50篇
  1929年   52篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
This study examines the correlation between development of expressed emotion (EE) in relatives and course of illness of 99 DSM-III schizophrenic patients. Patients whose relatives were high EE at baseline and at the 2nd CFI approximately 20 months later had a poor prognosis at the very outset of the study and an unfavourable course of illness. They had a higher rehospitalisation rate, more symptoms, lower psychosocial assessment, and a poorer 2-year and even 8-year outcome. Patients from families with a fluctuating EE or a consistently low EE had better courses. Expessed emotion is therefore a valid predictor not only of symptomatic relapses, but also of other important aspects of schizophrenia. The connection between EE index and course of illness seerns not to be simply reactive or causal, but complex and non-uniform.  相似文献   
22.
23.
Conclusions With adaptation and implementation of these concepts, current problems with today's anesthesia workstations can be overcome. The problems of information management and workstation layout will be of less significance.  相似文献   
24.
Summary In the hope of finding a treatable condition, the need for rapid diagnosis in HIV-seropositive patients with brain lesions is apparent. In order to evaluate the efficacy of stereotactic brain biopsy in AIDS patients, we retrospectively studied 25 HIV-infected patients undergoing stereotactic biopsy. Brain lesions were identified with gadolinium-enhanced MRI and/or contrastCT. Brain biopsy was performed using the system of Riechert. From 8 up to 15 small tissue samples from one or two targets were obtained in every patient. The biopsy material was examined cytologically, histologically (including electron microscopy), immunohistochemically and, in part, by animal test and polymerase chain reaction (PCR). A definite diagnosis was achieved in 92%. Diagnosis included primary central nervous system lymphoma (PCNSL) (10), toxoplasmosis (10), progressive multifocal leukoencephalopathy (2) and one case of co-existing toxoplasmosis and cytomegalovirus infection. Two biopsies were non-diagnostic. All PCNSLs showed polymorphic B-cell populations of high malignancy; accurate classification according to the Kiel classification was not possible. In 3 lymphomas Epstein-Barr nuclear antigen (EBNA) 2-mRNA could be detected by PCR and confirmed immunohistochemically by EBNA 2 expression. In 6 cases autopsy confirmed the biopsy diagnosis. Conventional histology was not sufficiently decisive for toxoplasmosis and progressive multifocal leukoencephalopathy, so that immunohistochemistry and animal tests became very important for a final diagnosis. With the help of different morphological and molecular biological techniques stereotactic brain biopsy appears to be an effective method in the diagnosis of HIV-associated brain lesions. In view of the marked radio- and chemosensitivity of PCNSLs it is mandatory to establish an early and accurate histological diagnosis for adequate treatment.  相似文献   
25.
BACKGROUND: The isolated perfused canine kidney has been established as a valid model for conducting both renal physiology and transplantation research. This model is of particular importance for developing new strategies to improve graft function after renal transplantation. In the present study, a newly developed method using isolated haemoperfused porcine kidneys was adapted for use in canine kidneys. In contrast to haemoperfusion, synthetic perfusion media can be standardized and can prevent the initiation of blood-mediated reperfusion reactions. Thus, an additional aim was to determine whether blood could be replaced by synthetic cell-free perfusion solutions. METHODS: Canine kidneys (n = 30) were harvested from donors euthanized in veterinary practices for causes unrelated to the present study. The kidneys were isolated and perfused with autologous blood or cell-free synthetic electrolyte buffer (Tyrode solution). During perfusion, we monitored renal perfusate flow (RPF), glomerular filtration rate (GFR), electrolyte and glucose reabsorption, oxygen consumption and urine concentration. RESULTS: Changes in perfusion medium did not affect the RPF. In contrast, GFR, urine concentration and oxygen consumption were significantly higher, whereas fractional excretion of sodium and glucose were significantly lower in blood- than in Tyrode-perfused kidneys. CONCLUSIONS: This system offers a simple model for studying whole-organ functional alterations after acute renal ischaemia. Renal function indicators were below values reported during in vivo physiological conditions. These functions were better conserved when kidneys were perfused with autologous blood than with Tyrode.  相似文献   
26.
The reduction of NBT to formazan has been suggested as an indicator of the reduction potential of biological systems. An increase in the amount of reduced formazan reflects the activation of the hexose monophosphate shunt of phagocytes cultivated in vitro, as a result of cellular stimulation by chemical or biological factors, or during phagocytosis. This phenomenon has been widely used for the determination of activated phagocytes by different methods. However, the technical limitations of these methods have not been evaluated carefully. In the investigations presented here threesolvents for formazan, pyridine, dioxane and dimethylformamide, have been tested for their suitability as extraction agents. For each solvent the optimal wavelength for photometric evaluation has been determined and dose relation curves between dissolved formazan and OD have been established. Several factors (time, temperature, pH, contamination with water or acid) affecting the dissolving properties and stability of formazan in different solvents have been investigated. With the solvents tested, dioxane proved to be the most suitable agent for extracting NBF. Thus, a methodology for the quantitative evaluation of NBT has been established. This method can be used for the identification of activators as well as of inhibitors of the phagocyte system.  相似文献   
27.
Lüthen F  Lange R  Becker P  Rychly J  Beck U  Nebe JG 《Biomaterials》2005,26(15):2423-2440
Mechanisms of cell adhesion and extracellular matrix formation are primary processes in the interaction with the material surface of an implant which are controlled by integrin receptors. The aim of our study was to find out whether beta1- and beta3-integrins of osteoblastic cells sense the surface topography of titanium, and if structural alterations of integrin adhesions were involved in the organization of fibronectin. Pure titanium surfaces were modified by polishing (P), machining (NT), blasting with glass spheres (GB), and blasting with corundum particles (CB) resulting in increasing roughness. Confocal microscopic investigations revealed fibrillar adhesions of beta1- and alpha5-integrins on P, NT, and GB, but on CB with its sharp edges these integrin subunits did not form fibrillar adhesions. beta3 generally appeared in focal adhesions. We observed aligned fibrillar structures of fibronectin on NT not only on the basal site but interestingly, also on the apical cell surface. In contrast, on CB, fibronectin appeared apically clustered. We suggest that this alignment of fibronectin fibrils depends on the directed actin cytoskeleton and in particular, on the capability of the beta1-integrins to form fibrillar adhesions, which is affected by the surface roughness of titanium.  相似文献   
28.
29.
Microdeletion syndromes are commonly transmitted as dominant traits and are frequently associated with variably expressed pleiotropic phenotypes. Nonlethal homozygous microdeletions, on the other hand, are very rare. Here, we delineate the fifth and so far largest homozygous microdeletion in nonmalignancies of approximately 400 kb on chromosome 4q11-q12 in a large consanguineous East-Anatolian family with six affected patients. The deleted region contains the beta-sarcoglycan gene (SGCB), the predicted gene SPATA18 (spermatogenesis associated 18 homolog) and several expressed sequence tags. Patients presented with a severe and progressive Duchenne-like muscular dystrophy phenotype, a combination of hyperlaxity and joint contractures, chest pain, palpitations, and dyspnea.  相似文献   
30.
Ohne ZusammenfassungMit 15 Textabbildungen.Das Bedürfnis nach Stützung schwächerer Gedanken durch stärkere wird auchKausalitäts bedürfnis genannt und ist die Haupttriebfeder aller naturwissenschaftlichenErklärungen. Ernst Mach.Nach einem auf der 89. Versammlung deutscher Naturforscher und Ärzte in Düsseldorf im September 1926 gehaltenen Vortrage. Vgl. auch Fortschritte d. naturwissenschaftl. Forschung, herausgeg. vonE. Abderhalden, Bd. XII, H. 4.  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