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   20660篇
  免费   1223篇
  国内免费   1050篇
耳鼻咽喉   139篇
儿科学   307篇
妇产科学   68篇
基础医学   2393篇
口腔科学   219篇
临床医学   2045篇
内科学   1118篇
皮肤病学   46篇
神经病学   1392篇
特种医学   1072篇
外国民族医学   3篇
外科学   7028篇
综合类   3507篇
预防医学   495篇
眼科学   460篇
药学   983篇
  16篇
中国医学   986篇
肿瘤学   656篇
  2024年   99篇
  2023年   420篇
  2022年   775篇
  2021年   963篇
  2020年   868篇
  2019年   618篇
  2018年   639篇
  2017年   716篇
  2016年   786篇
  2015年   745篇
  2014年   1592篇
  2013年   1457篇
  2012年   1273篇
  2011年   1339篇
  2010年   1066篇
  2009年   1086篇
  2008年   953篇
  2007年   1015篇
  2006年   909篇
  2005年   842篇
  2004年   713篇
  2003年   651篇
  2002年   479篇
  2001年   423篇
  2000年   377篇
  1999年   296篇
  1998年   241篇
  1997年   232篇
  1996年   198篇
  1995年   154篇
  1994年   145篇
  1993年   112篇
  1992年   103篇
  1991年   73篇
  1990年   55篇
  1989年   70篇
  1988年   59篇
  1987年   49篇
  1986年   42篇
  1985年   65篇
  1984年   35篇
  1983年   17篇
  1982年   39篇
  1981年   28篇
  1980年   20篇
  1979年   26篇
  1978年   28篇
  1977年   19篇
  1976年   10篇
  1973年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Day care is generally accepted in anterior segment eye-surgery. In the Rotterdam Eye Hospital this option was also considered for posterior segment surgery. We were interested in the opinion, of patients on this matter and therefore asked patients, who were admitted for posterior segment eye-surgery, to answer a questionnaire. The major question was: ‘If your physician had given his permission, do you think it would have been possible for you to go home on the evening after surgery?’. Other questions evaluated problems in organising assistance at home and transportation to the out-patient clinic as well as circumstances after the operation, such as pain, nausea, dizziness and anxiety. Eighty-one out of 87 patients responded: 56% answered ‘eyes’ and 44% ‘no’ to the major question. Relating the answer to the major question to medical data and to answers to the other questions, we found organizational problems at home and anxiety to have a statistical significant relation with a negative answer. Clinical factors like age, American Society of Anesthesiologists (ASA)-class, diabetes mellitus (including insulin-dependant), type of anesthesia, time of the day the surgery was finished, duration of surgery, pain, nausea or dizziness were not signficantly related. The number of patients involved in this study, however, is too small to draw conclusions on specific subgroups of patients.  相似文献   
82.
从1987年2月至1991年10月对24例诊断明确的椎动脉型颈椎病患者进行了双减压椎间融合术(BIFO)。其方法是在病变侧行横突前弓及钩椎关节骨赘切除,并行病椎椎间盘切除植骨融合。术后经1.5~5.2年随访,除2例恢复较慢外余皆在不同时间内康复,近远期效果满意。认为BIFO术式是既能去除椎动脉受压主要因素,又能稳定椎体,是一种新的有效的手术治疗方法。  相似文献   
83.

Background

The effect of the changes in the femoral posterior condylar offset (PCO) on anterior–posterior (AP) translation and internal–external (IE) rotation in cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty (TKA) remains unknown. The purpose of this study was to compare the kinematics in CR and PS TKA with respect to the difference in prosthetic design and PCO change through a computational simulation.

Methods

We developed three-dimensional finite element models with the different PCOs of ± 1, ± 2 and ± 3?mm in the posterior direction using CR and PS TKA. We performed the simulation with different PCOs under a deep knee bend condition and evaluated the kinematics for the AP and IE in CR and PS TKA.

Results

The more tibiofemoral (TF) translation in the posterior direction was found as PCO translated in posterior direction for both CR and PS TKA compared to the neutral position. However, the change of the AP translation with respect to the PCO change in CR TKA was greater than PS TKA. The more TF external rotation was found as PCO translated in the anterior direction for both CR and PS TKA compared to the neutral position. However, unlike the TF translation, the TF rotation was not influenced by the PCO change in both CR and PS TKA.

Conclusion

The PCO magnitude was influenced by a postoperative change in the kinematics in CR TKA although a relatively smaller effect was observed in PS TKA. Hence, surgeons should be aware of the PCO change, especially for CR TKA.  相似文献   
84.
The vascularization of the posterolateral area of the arm is supplied by the terminal branches of the deep brachial artery [middle collateral artery (MCA) and posterior radial collateral artery]. Their anatomy has been a field of confusion for a long time. An extended lateral arm flap, named the extreme lateral arm flap, supplied by these branches and dissected as a retrograde island flap has been proposed as an alternative for large compound defects of the distal forearm. We carried out an extensive anatomic study of the extreme lateral arm flap on 69 upper limbs: 54 fresh injected with colored latex, 10 embalmed and 5 radiographed after Micropaque injection. Two origin levels of the MCA were found: a proximal one (37%) above the radial groove, and a distal one (63%) at the level of the groove. The deep brachial artery always bifurcated after the origin of the MCA into a posterior radial collateral artery (PRCA) and anterior radial collateral artery (ARCA). Indeed in our dissections, after the origin of the MCA from the deep brachial artery, there was always a common trunk named the radial collateral artery (RCA) which bifurcated into the ARCA and PRCA. In all dissected arms we always found the MCA anastomosed in a transverse pattern with the inferior ulnar collateral artery (IUCA), contributing to the anastomotic circle of the elbow. This circle represents the unique vascularization source of the reverse extreme lateral arm flap.  相似文献   
85.
Paramyxoviruses of type 1 (PMV-l) isolated from pigeons were genetically analyzed. A part of the fusion and the matrix protein genes were amplified and sequenced, Typical amino acid sequences associated with virulence were determined at the fusion protein cleavage site in all PMV-1 isolates. All Slovene pigeon PMV-1 strains share high amino acid sequence similarity with other pigeon strains. In the phylogenetic tree, they are clustered together with pigeon PMV-1 isolates with moderate pathogenicity. Phylogenetic analysis obtained from the fusion and the matrix protein gene alignments showed the same branching order. Viruses circulating among pigeons were found to form quite unique lineage of virulent NDV strains.  相似文献   
86.
Polyclonal antiserum to an Escherichia coli-produced beta-galactosidase/E4 fusion protein of human papillomavirus type 6b (antiserum 256), and affinity purified HPV 11 anti-E4 antibodies were tested for reactivity in Western blots with bacterially expressed trpE/E4 fusion proteins of HPV types 6b, 11, 16, and 18. To further characterize the affinity purified anti-E4 antibodies, a dot-immunobinding assay was performed using overlapping synthetic HPV 11 E1E4 peptides as antigens. Protein extracts of condylomata acuminatum from 18 patients containing HPV type 6 or 11 DNA sequences were tested in Western blots using antiserum 256 or affinity purified HPV 11 anti-E4 antibodies. In the Western blots of the trpE proteins, antiserum 256 identified the HPV types 6b and 11 fusion proteins; the affinity purified HPV 11 anti-E4 antibodies identified only the HPV 11 fusion protein. In the dot-immunobinding assay, three HPV 11 peptides were recognized, each containing a shared 8 amino acid sequence that differs significantly from the corresponding sequences of HPV types 6b, 16, or 18. In the Western blots of protein extracts from 18 condylomata acuminatum samples shown to contain HPV types 6 or 11 DNA, putative E4 gene products were identified in six samples by antiserum 256. The affinity purified HPV 11 anti-E4 antibodies identified putative E4 gene products in one of these same six lesions, which was shown to contain HPV 11 sequences by the Southern blot method. All six samples containing E4 gene products were from women. Three of these women were pregnant, one had serum antibodies to the human immunodeficiency virus, and one was a renal transplant recipient receiving glucocorticoids.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
87.
Telomeres, besides their main role in the protection and maintenance of chromosome ends, have several other vital functions in the cell cycle. We studied their role in the achiasmatic meiosis of female Lepidoptera, insects with holokinetic chromosomes. By fluorescence in-situ hybridization (FISH) with the insect telomeric probe, (TTAGG) n , we mapped the distribution of telomeric and interstitial telomeric sequences (ITS) in female meiotic chromosomes of two species, Orgyia antiqua with a reduced chromosome number (2n=28) and Ephestia kuehniella mutants, possessing a radiation-induced chromosome fusion in the genome (2n=59). In addition to the strong typical telomeric signals, O. antiqua displayed weaker hybridization signals in interstitial sites of pachytene bivalents. The observed ITS most probably reflect remnants of chromosomal rearrangements and support the hypothesis that the Orgyia karyotype had arisen by multiple fusions of ancestral chromosomes. On the other hand, the absence of ITS in the chromosome fusion of Ephestia indicated the loss of telomeres before the two original chromosomes fused. When the telomeric probe was amplified by enzymatic reaction with tyramid, the number of ITS observed increased in Orgyia, and a few ITS were also observed in several chromosomes of Ephestia but not in the fused chromosome. This suggests that the genomes of both species also contain ITS other than those originating from chromosome fusions. The analysis of female meiotic prophase I revealed non-homologous associations of postpachytene bivalents mediated by telomeric DNA, which were not observed in the pachytene stage. Surprisingly, in early postpachytene nuclei the telomeric associations also involved ITS, whereas later postpachytene nuclei displayed chains of bivalents interconnected only by true telomeres. This finding favours a hypothesis that telomeric associations between bivalents play a role in chromosome segregation in the achiasmatic meiosis of female Lepidoptera. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
88.
Thyroglobulin (Tg) and thyroid peroxidase (TPO) are two antigens largely recognized by the sera from patients with autoimmune thyroid disease (AITD). Recently, the complete mapping of both antigens was established with rabbit polyclonal antibodies by the use of recombinant proteins expressed in prokaryotic vector. Several investigators have argued for the existence of a cross-reactivity of some hetero- and autologous antibodies versus these two proteins. In the present study, using rabbit polyclonal antibody, mouse polyclonal antibody and autoimmune antibody (aAb), we observed no common epitope on human Tg (hTg) and human TPO (hTPO).  相似文献   
89.
The epicondylar axis is a reliable reference to check the rotation of the femoral implant in total knee prostheses (TKPs). However, during the operation it seems easier to use the posterior condylar axis as a landmark. The angle between these two axes is called the posterior condylar angle (PCA). The aim of this study was to measure the PCA in arthritic knees to assess the reliability of the posterior condylar axis as a reference for the control of the rotation of the femoral implant and to look for correlation with other radiological measurements. This prospective study consisted of 103 arthritic knees (81 varus, 22 valgus) before a TKP had been done in 103 patients (75 women, 28 men). The assessment of the PCA was made by computed tomographic scanning (CT). The HKA, HKS and HKT angles were measured on the pangonogram. The posterior condylar axis was internally rotated with respect to the epicondylar axis. The average value for all the patients was 2.65° degrees with a range from 0° to 7°. The PCA was significantly increased in the valgus knees. There was no correlation between the angles on the pangonogram and the posterior condylar axis. While the preoperative assessment of the PCA by CT scanning is reliable, the results obtained indicate the marked variability in its value. If one wishes to use the posterior condylar axis as a guide for rotation, it is therefore necessary to assess the PCA for each patient using adjustable jigs according to the value obtained. No measurement on standard radiographs allowed an extrapolation of the value of the PCA, and CT scanning seems to be the preferable radiological examination.

Electronic Supplementary Material The french version of this article is available in the form of electronic supplementary material and can be obtained by using the Springer Link server located at
Etude tomodensitométrique de l'angle condylien postérieur dans les genoux arthrosiques. Intérêt dans le positionnement en rotation de l'implant fémoral dans les prothèses totales de genou
Résumé L'axe épicondylien est une référence fiable pour le contrôle de la rotation de l'implant fémoral dans les prothèses totales de genou (PTG). Mais, lors de l'intervention, il semble plus facile d'utiliser l'axe condylien postérieur comme repère. L'angle entre ses deux axes est appelé angle condylien postérieur (ACP). Le but de cette étude était de mesurer l'ACP dans les genoux arthrosiques, d'évaluer la fiabilité de l'axe condylien postérieur comme référence pour le réglage de la rotation de l'implant fémoral, de rechercher une corrélation avec d'autres mesures radiologiques. Une étude prospective comportant 103 genoux arthrosiques (81 varus et 22 valgus), avant PTG a été effectuée, chez 103 patients (75 femmes et 28 hommes). L'évaluation de l'ACP a été faite par examen tomodensitométrique (TDM). Les angles HKA, HKS et HKT ont été mesurés sur le pangonogramme. L'axe condylien postérieur était en rotation interne par rapport à l'axe épicondylien. La valeur moyenne pour tous les patients était de 2.65°, avec des valeurs de 0 à 7°. La valeur de l'angle CP augmentait avec une différence significative dans le groupe des genu valgum. Il n'y avait pas de corrélation entre les angles du pangonogramme et l'ACP. Si l'évaluation pré-opératoire de l'ACP par TDM est fiable, les résultats obtenus mettent en évidence une variabilité importante de sa valeur. Il faut donc, si l'on veut utiliser l'axe condylien postérieur comme repère de rotation, évaluer pour chaque patient l'ACP, et utiliser un ancillaire réglable reportant la valeur obtenue. Aucune mesure sur des radiographies standard ne permettant d'extrapoler la valeur de l'ACP, la TDM semble l'examen radiologique de choix.
  相似文献   
90.
The muntjacs (Muntiacus, Cervidae) are famous for their rapid and radical karyotypic diversification via repeated tandem chromosome fusions, constituting a paradigm for the studies of karyotypic evolution. Of the five muntjac species with defined karyotypes, three species (i.e. Muntiacus reevesi, 2n = 46; M. m. vaginalis, 2n = 6/7; and M. crinifrons, 2n = 8/9) have so far been investigated by a combined approach of comparative chromosome banding, chromosome painting and BAC mapping. The results demonstrated that extensive centromere–telomere fusions and a few centric fusions are the chromosomal mechanisms underlying the karyotypic evolution of muntjacs. Here we have applied the same approach to two additional muntjac species with less well-characterized karyotypes, M. feae (2n = 14♂) and M. gongshanensis (2n = 8♀). High-resolution G-banded karyotypes for M. feae and M. gongshanensis are provided. The integrated analysis of hybridization results led to the establishment of a high-resolution comparative map between M. reevesi, M. feae, and M. gongshanensis, proving that all tandem fusions underpinning the karyotypic evolution of these two muntjac species are also centromere–telomere fusions. Furthermore, the results have improved our understanding of the karyotypic relationships of extant muntjac species and provided compelling cytogenetic evidence that supports the view that M. crinifrons, M. feae, and M. gongshanensis should each be treated as a distinct species.  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