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   1775篇
  免费   94篇
  国内免费   57篇
耳鼻咽喉   8篇
儿科学   101篇
妇产科学   39篇
基础医学   213篇
口腔科学   42篇
临床医学   214篇
内科学   418篇
皮肤病学   57篇
神经病学   42篇
特种医学   304篇
外国民族医学   1篇
外科学   170篇
综合类   28篇
一般理论   2篇
预防医学   79篇
眼科学   31篇
药学   89篇
中国医学   4篇
肿瘤学   84篇
  2021年   23篇
  2020年   13篇
  2019年   19篇
  2018年   29篇
  2017年   15篇
  2016年   16篇
  2015年   26篇
  2014年   32篇
  2013年   66篇
  2012年   49篇
  2011年   51篇
  2010年   54篇
  2009年   67篇
  2008年   34篇
  2007年   81篇
  2006年   39篇
  2005年   41篇
  2004年   31篇
  2003年   33篇
  2002年   36篇
  2001年   25篇
  2000年   31篇
  1999年   36篇
  1998年   78篇
  1997年   84篇
  1996年   107篇
  1995年   63篇
  1994年   62篇
  1993年   53篇
  1992年   36篇
  1991年   22篇
  1990年   34篇
  1989年   57篇
  1988年   44篇
  1987年   44篇
  1986年   56篇
  1985年   54篇
  1984年   21篇
  1983年   22篇
  1982年   18篇
  1981年   12篇
  1980年   14篇
  1979年   23篇
  1978年   22篇
  1977年   15篇
  1976年   20篇
  1975年   16篇
  1974年   7篇
  1973年   8篇
  1897年   12篇
排序方式: 共有1926条查询结果,搜索用时 187 毫秒
21.
22.
23.
In a human in-vitro fertilization (IVF) programme, the effect of co- culture of embryos with human fibroblasts was evaluated with respect to pregnancy rate and embryo development. Patients were included in the study after giving informed written consent. The IVF treatments were randomly assigned by stratification of both age (<36 versus > or =36 years) and previous IVF attempts (yes versus no). After fertilization was established, the zygotes were transferred to a 4-well dish with or without fibroblasts and cultured for 2 days. On the third day after ovum pick-up (OPU), cell number and quality [5 (good) to 1 (poor)] of the embryos were scored and a maximum of three embryos was transferred. Supernumerary embryos of good quality were cryopreserved. The design of this study was a group sequential trial with the objective of detecting differences between pregnancy rates following IVF with conventional incubation or incubation in co-culture with fibroblasts. This design included one evaluation at half-way data collection. In the study, 148 patients had an OPU, of whom 77 were allocated to the co-culture group. There was no statistically significant difference in pregnancy rate, cell number and embryo quality between the two groups. The ongoing pregnancy rate per embryo transfer was 27% in co-culture and 30% in the conventional culture group. The implantation rates per transferred embryo were 17 and 18% respectively. Using a multivariate logistic regression model for the probability of ongoing pregnancies, the odds ratio of co-culture, adjusted for age and previous IVF attempts, was not statistically significant. In conclusion, co-culture with human fibroblasts does not contribute to an improvement of embryo quality nor to a higher pregnancy rate after IVF in an unselected group of patients.   相似文献   
24.
Summary The anatomic constraints imposed on a total artificial heart (TAH) require specific anatomic studies. A thoracic anatomic study was performed with a scanning device equipped with three-dimensional (3-D) reconstruction software on 15 male patients, between the ages of 41 to 63 years (52 ± 6 years). All were candidates for heart transplantation. The 3-D reconstructions of the cardiovascular structures obtained from surgical anatomy data specific to TAH implantation allowed a volumetric measurement of these structures. A modeling diagram of these structures permitted reproducible quantitative measurements of the 35 geometrical parameters which characterized shape, orientation, and position of these structures within the thorax. Most of the measured parameters were characterized by low variability (coefficient of variation from 10 to 25%).
Modélisation tridimensionnelle de l'anatomie du cur et des gros vaisseaux
Résumé Les contraintes anatomiques imposées au cur artificiel total (CAT) nécessitent des études anatomiques spécifiques. Une étude anatomique thoracique a été réalisée avec un scanner doté d'un logiciel de reconstruction tridimensionnelle (3-D) chez 15 patients, tous de sexe masculin, agés de 41 à 63 ans (52 ± 6 ans), et candidats à une transplantation cardiaque. Les reconstructions 3-D des structures cardio-vasculaires réalisées selon les données de l'anatomie chirurgicale propre à l'implantation du CAT ont permis la mesure volumétrique de ces structures. Un schéma de modélisation de ces structures a permis des mesures quantitatives reproductibles de 35 paramètres géométriques caractéristiques de la forme, de l'orientation, de la position de ces structures dans le thorax. Les résultats de ces mesures ont pu être exprimés en termes statistiques. La plupart des paramètres mesurés étaient caractérisés par une faible variabilité (coefficients de variations de 10 à 25%).
  相似文献   
25.
The persistence of Cytomegalovirus (CMV) with alteration of cell surface expression in certain tissues may initiate the tissue destruction that leads to the clinical manifestations of Sjogren's Syndrome. Salivary gland and lacrimal gland ductal cells are immunologically attacked due to CMV antigenic expression. The destruction of these ducts leads to xerostomia and keratonconjunctivitis sicca, the hallmarks of Sjogren's Syndrome.  相似文献   
26.
Summary The angular points are the ligamentous and tendinous structures that reinforce the posteromedial and posterolateral capsule of the knee and share in fixation of the posterior horns of the menisci. They are often damaged in acute injuries and this is usually associated with ruptures of the cruciate and collateral ligaments and may add to the degree of laxity. We describe the normal appearance of these structures in terms of the sectional anatomy, correlated with the lesional appearances of complete and incomplete ruptures and associated meniscal detachments as shown by clinical testing and arthrotomy findings.
IRM des points d'angle du genou : bases anatomiques et applications aux genoux traumatiques
Résumé Les points d'angle sont des structures ligamentaires et tendineuses qui renforcent la capsule postéro-médiale et postéro-latérale et participent à la fixation des cornes postérieures des ménisques. Leurs lésions, fréquentes au cours des traumatismes aigus, sont généralement associées à des ruptures des ligaments croisés et des ligaments collatéraux et peuvent être source d'une aggravation de la laxité. Nous rapportons, en corrélation avec l'anatomie en coupe, l'aspect normal de ces structures, et en corrélation avec les données de l'arthrotomie et du testing les aspects lésionnels observés au cours des traumatismes : ruptures complètes, incomplètes et désinsertions méniscales associées.
  相似文献   
27.
28.
Summary The artery of the sino-atrial node was studied in 100 normal human hearts after injection of each coronary artery with coloured gelatine containing a radiopaque substance. The hearts belonged to 69 males and 31 females, being 64 Caucasians and 36 non-Caucasians (Negroes and Mulattoes) whose age ranged from 7 to 80 years. Since the individuals had committed suicide or were victims of accidents, their hearts, after pathologists' evaluation, were considered normal. The sinoatrial node of the normal human heart is supplied by the right coronary artery more frequently (58%±4.9% of the cases) than by the left (42%±4.9). The right anterior medial atrial artery, originating from the right coronary at the level of the medial third of the right anterior quadrant of the atrial dome, is most frequently (50%±5) responsible for the blood supply of the sinoatrial node. Among the branches of the left coronary artery, the left anterior medial atrial artery, originating at the level of the medial third of the left. anterior quadrant of the atrial cupola, was the most frequent blood supplier (25%±4.3) of the sinoatrial node. The origin of the artery of the sinoatrial node from the proximal portion or trunk of the left coronary artery was less frequent (12%±3.2) than the origin from the circumflex artery (30%±4.5). Neither sex nor race influenced the variations of the origin of the sino-atrial node.
Variations d'origine de l'artère du noeud sinu-atrial du coeur humain normal
Résumé L'a. du noeud sinu-atrial a été étudiée sur 100 coeurs humains normaux après injection de chaque a. coronaire à la gélatine colorée additionnée d'une substance radio-opaque. Les coeurs provenaient de 69 hommes et 31 femmes, 64 caucasiens et 36 non caucasiens (nègres et mulâtres) âgés de 7 à 80 ans. Ces sujets étant décédés par suicide ou des suites d'accidents, leurs coeurs ont été considérés comme normaux après examen anatomo-pathologique. Le noeud sinu-atrial du coeur humain est vascularisé par l'a. coronaire droite plus fréquemment (58 %±4,9) que par l'a. coronaire gauche (42 %±4). L'a. atriale antéro-médiale droite, issue de l'a. coronaire droite au niveau du tiers médial du quadrant antérieur droit du dôme atrial est l'artère la plus fréquemment en cause (50 %±5) dans la vascularisation du noeud sinuatrial. Parmi les branches de l'a. coronaire gauche, l'a. atriale antéro-médiale gauche, née au niveau du tiers médial du quadrant antérieur gauche du dôme atrial, était la branche la plus fréquemment en cause (25 %±4,3) dans la vascularisation du noeud sinu-atrial. La naissance de l'a. du noeud sinu-atrial à partir de la partie proximale ou du tronc de l'a. coronaire gauche était moins fréquente (12 %±3,2) que son origine à partir du rameau circonflexe (30 %±4,5). Les variations d'origine de l'a. du noeud sinu-atrial n'apparaissaient pas influencées par le sexe ou la race.
  相似文献   
29.
The authors describe a simplified method for the measurement of free thyroxine based on the affinity of Sephadex gel for thyroxine. Radiolabeled thyroxine added to diluted serum is adsorbed by the gel proportionally to the free thyroxine concentration of the sample. The concentration of binding proteins present in the sample does not affect the adsorption of free thyroxine on the gel. The adsorbed thyroxine is separated by centrifugation and filtration using a rigid filter. Calibration is made against the equilibrium dialysis method. The intra (CV of 4.9 p. cent, 6.1 p. cent, 10.2 p. cent for concentrations of free thyroxine of 14.1, 27.1 and 67.6 pmol/l respectively) and interassay (CV of 5.3 p. cent, 8.2 p. cent, 9.2 p. cent at 9.4, 23.0 and 83.1 pmol/l respectively) imprecisions are comparable to equilibrium dialysis. The results obtained with this method show a good correlation with those of a two-step radioimmunoassay for patients without non-thyroidal diseases or pregnancy (r2 = 0.85, n = 50). The reference range (mean +/- two standard deviations) determined in 108 euthyroid adults is 10.3 to 21.9 pmol/l. Results obtained for hypothyroid patients (7.7 +/- 2.3 pmol/l, mean +/- one standard deviation, n = 26), hyperthyroid patients (47.4 +/- 22.9 pmol/l, n = 32), patients with non-thyroidal illnesses (18.7 +/- 4.9 pmol/l, n = 35) and pregnant women (10.8 +/- 1.7 pmol/l, n = 20) are in good agreement with those reported using equilibrium dialysis or ultrafiltration. Our method offers an alternative to more tedious techniques of free thyroxine determination in the hospitalized population for which the use of analog methods has been criticized.  相似文献   
30.
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