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   4520篇
  免费   228篇
  国内免费   30篇
耳鼻咽喉   65篇
儿科学   362篇
妇产科学   78篇
基础医学   363篇
口腔科学   145篇
临床医学   290篇
内科学   1399篇
皮肤病学   69篇
神经病学   275篇
特种医学   111篇
外科学   669篇
综合类   80篇
一般理论   1篇
预防医学   116篇
眼科学   157篇
药学   325篇
中国医学   19篇
肿瘤学   254篇
  2024年   5篇
  2023年   44篇
  2022年   103篇
  2021年   185篇
  2020年   119篇
  2019年   171篇
  2018年   231篇
  2017年   130篇
  2016年   186篇
  2015年   147篇
  2014年   223篇
  2013年   267篇
  2012年   375篇
  2011年   384篇
  2010年   227篇
  2009年   173篇
  2008年   284篇
  2007年   305篇
  2006年   282篇
  2005年   204篇
  2004年   207篇
  2003年   159篇
  2002年   136篇
  2001年   29篇
  2000年   22篇
  1999年   17篇
  1998年   21篇
  1997年   16篇
  1996年   16篇
  1995年   14篇
  1994年   14篇
  1993年   7篇
  1992年   10篇
  1991年   6篇
  1990年   4篇
  1989年   10篇
  1988年   7篇
  1987年   2篇
  1986年   4篇
  1984年   5篇
  1983年   2篇
  1981年   4篇
  1980年   3篇
  1978年   3篇
  1977年   3篇
  1976年   2篇
  1973年   2篇
  1971年   2篇
  1968年   1篇
  1954年   1篇
排序方式: 共有4778条查询结果,搜索用时 15 毫秒
21.
Cyclic ADP-ribose (cADPR) mobilizes calcium from intracellular stores and contributes to agonist-induced intracellular calcium elevation in airway smooth muscle (ASM). In this study we determined the functional role of CD38/cADPR signaling in the regulation of airway tone using CD38 deficient (cd38(-/-)) mice. The responsiveness to different doses of methacholine, as determined by changes in lung resistance and dynamic compliance, was significantly (P < or = 0.05) lower in cd38(-/-) mice compared with wild-type controls. To determine the mechanism responsible for the reduced responsiveness, we measured the intracellular calcium responses to contractile agonists in ASM cells. In ASM cells isolated from cd38(-/-) mice, the intracellular calcium responses to acetylcholine and endothelin-1 were significantly lower than in controls. Pretreatment of ASM cells with a cADPR antagonist resulted in attenuated intracellular calcium responses to endothelin-1 in cells isolated from wild-type mice, but not in those isolated from the cd38(-/-) mice. Very low cADPR levels and no detectable ADP-ribosyl cyclase activity were observed in lung tissue from cd38(-/-) mice, suggesting that CD38 is a critical source for cADPR synthesis. The results of the present study demonstrate that CD38/cADPR contributes to airway smooth muscle tone and responsiveness through its effects on agonist-induced elevation of intracellular calcium in ASM cells.  相似文献   
22.
23.
A 22-year-old male, referred to us as a case of multi-drug resistant tuberculosis was diagnosed as allergic bronchopulmonary aspergillosis (ABPA) after serological and computed tomography confirmation. He was initiated on oral as well as inhaled corticosteroids along with nasal corticosteroid spray for his nasal complaints. One year subsequently, he developed a nasal septal perforation. Biopsy taken from the site did not reveal any granulomatous or atrophic changes and cultures of the biopsy did not yield any organism. The septal defect, repaired surgically by Hazeltine's method healed completely within 6 weeks. There have been anecdotal reports of septal perforation in patients with rhinitis on intranasal corticosteroids but hitherto not in patients with ABPA. A periodic examination of the nasal septum should be undertaken in patients with ABPA and rhinitis on long term inhaled oral and intranasal corticosteroids along with oral corticosteroids.  相似文献   
24.
Linear microcracks and diffuse damage (staining over a broad region) are two types of microscopic damage known to occur in vivo in human vertebral trabecular bone. These damage types might be associated with vertebral failure. Using microcomputed tomography and finite element analysis for specimens of cancellous bone, we estimated the stresses in the trabeculae of human vertebral tissue for inferosuperior loading. Microdamage was quantified histologically. The density of in vivo linear microcracks was, but the diffuse damage area was not, related to the estimates of von Mises stress distribution in the tissue. In vivo linear microcrack density increased with increasing coefficient of variation of the trabecular von Mises stress and with increasing average trabecular von Mises stress generated per superoinferior apparent axial stress. Nonlinear increase in linear crack density, similar to the increase of the coefficient of variation of trabecular shear stresses, with decreasing bone stiffness and bone volume fraction suggests that damage may accumulate rather rapidly in diseases associated with low bone density due to the dramatic increase of shear stresses in the tissue. © 2003 Biomedical Engineering Society. PAC2003: 8719Rr, 8719Xx, 8759Ls, 8759Fm, 8710+e  相似文献   
25.
The genetic diagnosis of Gaucher disease by molecular methods is complicated by the existence of a highly homologous transcribed pseudogene (96% identity) that is found in close proximity to the true gene on chromosome 1q21. In addition, the pseudogene sequence can mimic disease-causing mutations in the true gene. Selective polymerase chain reaction (PCR) amplification of the true gene can be accomplished in extracted DNA from fresh-frozen samples by designing oligonucleotide primers to hybridize to defined regions that are not present in the pseudogene. This standard molecular approach, which entails amplification of relatively long segments of intact DNA, is not feasible in archival, paraffin-embedded, solid-tissue specimens in which the negative effects of chemical fixation result in DNA strand scission and breakdown of nucleic acid. A novel approach, specifically created for use with archival, fixative-treated tissue specimens, was developed for detection and characterization of common mutations of Gaucher disease. Three separate robust PCR reactions were formulated, 2 for selective amplification of portions of only the true gene exons 2 and 9, with a third reaction targeting exon 10, wherein both the true and pseudogene were coamplified. In the latter, DNA sequencing was used to determine the presence of true and pseudogene allele content in addition to identification of base sequence alterations. This method, requiring a single, 4-microm-thick histologic section, was successfully applied to archival paraffin block tissue specimens that had been in storage for up to 75 years. It was capable of accurately genotyping common Gaucher disease mutations as well as discovering a novel mutation and genetic polymorphism. We recommend our approach when only fixative-treated tis sue is available for molecular genotyping.  相似文献   
26.
Remodeling of the chromatin network plays an important role regulating embryonic development as well as differentiation. The SWI/SNF complex is an ATP-dependent chromatin-remodeling complex. It consists of several proteins, including an ATPase subunit, either Brg1 or Brm. Two subunits of this complex, Baf53a and Baf45, have been previously identified as being neural progenitor-specific. In this study, we show that Baf60c, another important part of this large complex, acts in a similar neural progenitor-specific manner. We show that during development Baf60c is expressed in neural progenitors in human retinas as well as mouse retina, cortex and spinal cord. Baf60c expression is lost during neural differentiation and its overexpression keeps the progenitors in a proliferative state through its interaction with the Notch pathway. Finally, we show that Baf60c is re-expressed in the Müller glial cells that re-enter the cell cycle after neurotoxic damage.  相似文献   
27.
28.
Summary Cyto- and myeloarchitectonic investigation of the temporal operculum and the exposed superior temporal gyrus was combined with a connection study of the projection fibers of the pertinent areas in the rhesus monkey.A belt-like organization of the auditory region with a koniocortex core (corresponding to AI) surrounded by belt areas was revealed. This organization principally resembled that of the auditory region of the cat (Rose and Woolsey, 1949; Woolsey, 1961) and that of other sensory regions (Sanides, 1972; Sanides and Krishnamurti, 1967). The belt is composed of one prokoniocortex area (proA, corresponding to AII) in parinsular location and of a caudal (paAc), lateral (paAlt) and rostral (paAr) parakoniocortex area. The latter has a particular character. It was found to be the target of thalamic projections of the caudalmost portion of GMpc. In contrast to the other parakonio areas it does not receive associations of the koniocortex.The belt areas, including the prokoniocortex, are ipsilaterally and transcallosally interconnected as in the somatic sensory (Jones and Powell, 1969a, b; Pandya and Kuypers, 1969; Pandya and Vignolo, 1969) and visual regions (Myers, 1962; Kuypers et al., 1965; Karol and Pandya, 1971).The koniocortex core is formed by two areas, Kam and Kalt, corresponding to the architectonic organization hitherto only known in man. The medial area (Kam) has a large number of homotopical callosal projections except at its medial border (to proA). The lateral area receives less callosal fibers, particularly most of its lateral portion is devoid of terminations. Since the belt areas are rich in callosal projections the supratemporal plane shows a pattern of three stripes of callosal terminations with two intermittent stripes void of terminations.While the projections of the koniocortex into the belt areas terminate prevalently in layer IV, the parakoniocortex sends fibers only into layers I and II of the koniocortex. This corresponds to results in somatic sensory (Pandya and McKenna, unpublished observations) and visual regions (Kuypers et al., 1965; Sanides and Vitzthum, 1965b; Spatz, personal communication).In contrast to other sensory regions the auditory koniocortex receives its exceptionally dense, homotopic callosal connections in the whole outer stratum with emphasis on layer III, as opposed to layer IV in the somatic sensory region.  相似文献   
29.
30.
AimsTo evaluate vitamin D3 levels in patients who presented with increased musculo-skeletal pain after release of lockdown period when compared to pre-lockdown status.IntroductionDuring this COVID pandemic, many countries have implemented lockdown measures and people have to work from home and many students and workers have to restrict themselves to home. During this period, their outdoor activities were limited. After the partial release of this lockdown many of them started to have some kind of physical activity and started experiencing body pains. We evaluated such patients for vitamin D3 levels and symptoms of fibromyalgia.MethodsThis is a retrospective analysis of patients from age group 18–60 presented to outpatient department or on telephonic consultation after partial release of lockdown. All patients who had mild back ache before lockdown and had symptoms exaggerated during this lockdown release were included. All patients were investigated for vitamin D3, PTH, thyroid profile, liver functional and kidney functional tests.ResultsOut of 120 patients presented to us in a period of 3 months, 31 patients had increased symptoms when compared to pre-lockdown status. 20 out of 31 patients had low vitamin D3 levels. 14 patients also developed symptoms of fibromyalgia.ConclusionThere might be many reasons for increased pain during lockdown, but we focussed specially only on vitamin D3 because of its association with increased symptoms of COVID-19. This is a gentle reminder to test for vitamin D3 levels and supplement if found deficient.Supplementary InformationThe online version contains supplementary material available at 10.1007/s43465-021-00376-8.  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