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   20570篇
  免费   745篇
  国内免费   20篇
耳鼻咽喉   362篇
儿科学   658篇
妇产科学   448篇
基础医学   3298篇
口腔科学   430篇
临床医学   1476篇
内科学   3778篇
皮肤病学   767篇
神经病学   1848篇
特种医学   1100篇
外国民族医学   23篇
外科学   2971篇
综合类   63篇
一般理论   9篇
预防医学   1131篇
眼科学   349篇
药学   1612篇
中国医学   17篇
肿瘤学   995篇
  2021年   120篇
  2020年   108篇
  2019年   150篇
  2018年   306篇
  2017年   257篇
  2016年   366篇
  2015年   415篇
  2014年   391篇
  2013年   594篇
  2012年   911篇
  2011年   922篇
  2010年   510篇
  2009年   407篇
  2008年   817篇
  2007年   893篇
  2006年   915篇
  2005年   892篇
  2004年   828篇
  2003年   799篇
  2002年   784篇
  2001年   770篇
  2000年   871篇
  1999年   703篇
  1998年   202篇
  1997年   144篇
  1996年   130篇
  1995年   100篇
  1994年   97篇
  1992年   336篇
  1991年   361篇
  1990年   351篇
  1989年   310篇
  1988年   262篇
  1987年   268篇
  1986年   228篇
  1985年   234篇
  1984年   179篇
  1983年   116篇
  1982年   117篇
  1979年   194篇
  1978年   133篇
  1977年   120篇
  1975年   150篇
  1974年   133篇
  1973年   155篇
  1972年   143篇
  1971年   129篇
  1970年   130篇
  1969年   122篇
  1967年   119篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Ohne ZusammenfassungMit 3 TextabbildungenHerrn Prof. Dr. A. Hase in Verehrung gewidmet.  相似文献   
93.
We used acetylcholine and butyrylcholine to competitively inhibit the cleavage of acetylthiocholine or butyrylthiocholine in plaques and tangles of Alzheimer's disease. Butyrylcholine was much more effective than acetylcholine in reducing the histochemical reaction for acetylcholinesterase not only in neuronal fibers, but also in plaques and tangles. This is in keeping with biochemical data on acetylcholinesterase and supports the existence of true acetylcholinesterase activity within plaques and tangles. However, 2-4 times higher acetylcholine and buturylcholine concentrations were necessary to inhibit the plaque and tangle bound enzyme. Together with the previously reported different pH optima, this suggests that the plaque- and tangle-bound acetylcholinesterase may represent an altered form of this enzyme.  相似文献   
94.
Summary The clinical and morphological findings are described in 27 children with nephronophthisis. Seventeen children were considered as sporadic cases. In 10 familial cases the presumed mode of inheritance was autosomal recessive. The clinical picture was rather uniform: polyuria-polydipsia, hyposthenuria, anemia, growth retardation, and azotemia with progressive renal failure. Six patients presented with tapeto-retinal degeneration. In a further seven children other ocular changes were detected. Two female siblings showed additional non-renal manifestations: mental retardation, pulmonary emphysema, skeletal anomalies, and congenital hepatic fibrosis.Renal histology displayed a chronic sclerosing tubulo-interstitial nephropathy with extensive tubular atrophy and dedifferentiation. Medullary cysts were frequently found in end-stage kidneys. Immunofluorescence was either non-specific or completely negative. On electron microscopy, the tubular basement membrane changes predominated: thickening, lamellation, splitting, and deposition of microfibrils within the increased basement membrane substance. Detailed light- and electron microscopic findings were non-specific but the overall morphologic picture was characteristic and even diagnostic in conjunction with the clinical presentation.A recurrence of nephronophthisis in transplanted kidneys has not been observed.The pathogenesis of nephronophthisis is obscure but with respect to the morphologic findings a primary or secondary tubular basement membrane defect seems very likely.Our experience suggests that nephronophthisis is a frequent cause of chronic renal failure in children and commonly associated with non-renal abnormalities. To avoid the separation of different syndromes presenting with a uniform renal disease but various non-renal manifestations, we suggest that the term nephronopthisis complex be used.Presented in part at the 63th Annual Meeting of the German Society of Pathology, Stuttgart 1979  相似文献   
95.
Patients suffering from psychosomatic diseases in the strict sense of the term (asthma, ulcers, colitis etc.) have characteristic object relations which we call the 'relation blanche'. The present investigation aims at finding out whether similar features can be observed in patients suffering from early and late gestosis. The results indicate that there is a definite connection between gestosis and the group of strictly psychosomatic diseases, thus confirming our hypothesis that gestosis does not primarily represent a neurotic conflict situation nor a psychotic breakdown.  相似文献   
96.
Zusammenfassung Die Therapie idiopathischer Ödeme mit Diuretica ist problematisch, da sie die Symptome nicht beseitigt, sondern einen sekundären Hyperaldosteronismus induziert, der die Ödembildung unterhält. Die Beobachtung einer verminderten Dopaminausscheidung bei Patientinnen mit idiopathischen Ödemen läßt einen Behandlungsversuch mit dem oral wirksamen Dopaminagonisten Bromocriptin als sinnvoll erscheinen.Wir behandelten daher neun Patientinnen mit idiopathischen Ödemen mit typischer Symptomatik und mehrjähriger Anamnese mit 2 × 2,5 mg/die Bromocriptin (Pravidel®). Der Therapieerfolg wurde nach der Normalisierung der circadianen Gewichtsschwankungen und dem subjektiven Befinden beurteilt. Sieben Patientinnen zeigten einen guten, eine nur einen unsicheren Therapieerfolg, und eine Patientin brach die Therapie wegen Nausea ab.Vor und während Bromocriptinbehandlung sind Serumelektrolyte, Blutdruck, Plasmareninaktivität und Aldosteron normal. Bromocriptin normalisiert die circadianen Gewichtsschwankungen, ohne das morgendliche Körpergewicht zu senken. Die Ergebnisse der vorliegenden Pilotstudie legen nahe, daß Bromocriptin bei einigen Patientinnen mit idiopathischen Ödemen eine wirksame Alternative zur herkömmlichen diuretischen Therapie sein kann. Es bleibt offen, ob die Bromocriptinwirkung durch einen Dopaminmangel zu erklären ist, oder ob Bromocriptin eine rein symptomatische Behandlung darstellt.  相似文献   
97.
Growing evidence suggests that G‐proteins may be involved in pathogenesis and treatment of affective disorders. Several studies have reported altered levels and/or activities of stimulatory G‐proteins in depression. The aim of this study was to investigate whether a polymorphism in the stimulatory α subunit of G‐proteins (T/C point mutation in exon 5; ATT → ATC at codon 131) is associated with major depression or response to antidepressant treatment. Therefore, we performed a case‐control association study with 212 depressive patients and 137 healthy, unrelated controls. There was no evidence for an association between the investigated polymorphism in the Gαs gene and major depression, as well as to treatment response. The results of our study are in concordance with recently published findings which do not support the hypothesis that the gene for the stimulatory α subunit of G‐proteins is a major susceptibility factor in the pathophysiology of major depression. © 2002 Wiley‐Liss, Inc.  相似文献   
98.
It has been previously shown that S100A2 is down-regulated in tumor cells and can be considered a tumor suppressor. We have recently shown that this down-regulation can be observed particularly in epithelial tissue, where S100A2 expression decreases remarkably in tumors as compared with normal specimens. In the present paper we investigate whether S100A2 could play a tumor-suppressor role in certain epithelial tissues by acting at the cell migration level. To this end, we made use of five in vitro human head and neck squamous cell carcinoma lines in which we characterized S100A2 expression at both RNA and protein level. To characterize the influence of S100A2 on cell kinetic and cell motility features, we used two complementary approaches involving specific antisense oligonucleotides and the addition of S100A2 to the culture media. The different expression analyses gave a coherent demonstration of the fact that the FADU and the RPMI-2650 cell lines exhibit high and low levels of S100A2 expression, respectively. Antisense oligonucleotides (in FADU) and extracellular treatments (in RPMI) showed that, for these two models, S100A2 had a clear inhibitory influence on cell motility while modifying the cell kinetic parameters only slightly. These effects seem to be related, at least in part, to a modification in the polymerization/depolymerization dynamics of the actin microfilamentary cytoskeleton. Furthermore, we found evidence of the presence of the receptor for advanced glycation end-products (RAGE) in RPMI cells, which may act as a receptor for extracellular S100A2. The present study therefore presents experimentally based evidence showing that S100A2 could play a tumor-suppressor role in certain epithelial tissues by restraining cell migration features, at least in the case of head and neck squamous cell carcinomas.  相似文献   
99.
We examined the influence of various alginates on the redifferentiation of dedifferentiated articular chondrocytes in alginate bead culture under low (5%) and (21%) high oxygen supply. Isolated bovine articular chondrocytes were dedifferentiated and multiplied by 2-week monolayer culture under 21% oxygen. They were subcultured at a density of 10(7) cells/mL in six different commercially available sodium alginates (1.2%, w/v) and held under 21 or 5% oxygen for 3 weeks. Proliferation (DNA measurement on days 0 and 21 of culture), collagen type II production (immunocytochemistry and Western blotting), and [(3)H]proline and [(35)S]sulfate incorporation were monitored. Collagen type II production was significantly stronger under 5% oxygen compared with 21% oxygen in two alginates (three other alginates nearly reached the significance level). However, alginate-based differences proved not to be significant. [(3)H]Proline incorporation was not influenced by alginate but showed strong oxygen dependency (up to 3-fold higher under 5% oxygen). For [(35)S]sulfate incorporation oxygen dependency was even stronger (up to 8-fold higher under 5% oxygen) and significant alginate-dependent differences were found for several alginates. The effects of the different alginates did not correlate with their pH, viscosity, or guluronic:mannuronic acid ratio. Thus, the type of alginate and even more, the oxygen supply, influence the redifferentiation and matrix production of dedifferentiated bovine articular chondrocytes.  相似文献   
100.
Neuropsychological deficits were investigated with respect to regional distribution of cerebral atrophy as assessed by volumetric magnetic resonance imaging (MRI) in 50 patients with Alzheimer's dementia (AD; NINCDS-ADRDA criteria) and 20 healthy volunteers. When compared between groups, test performance of all investigated neuropsychological domains including declarative memory, language, praxia, psychomotor speed, as well as attention and concentration was significantly impaired. These deficits were differentially correlated with regional atrophic changes. In particular, volumes of the right amygdala-hippocampus complex correlated with declarative memory performance, whereas volumes of the left temporo-parietal regions correlated with performance in naming and praxia. Furthermore, left frontal lobe atrophy was associated with verbal fluency. Our data confirm the central role that medial temporal atrophy plays for declarative memory deficits in AD and indicate that additional changes in the parietal, temporal and frontal lobes are responsible for further neuropsychological deficits characteristic of this disorder.  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