全文获取类型
收费全文 | 2791篇 |
免费 | 158篇 |
国内免费 | 34篇 |
专业分类
耳鼻咽喉 | 72篇 |
儿科学 | 99篇 |
妇产科学 | 57篇 |
基础医学 | 362篇 |
口腔科学 | 88篇 |
临床医学 | 208篇 |
内科学 | 723篇 |
皮肤病学 | 137篇 |
神经病学 | 140篇 |
特种医学 | 234篇 |
外科学 | 381篇 |
综合类 | 34篇 |
预防医学 | 202篇 |
眼科学 | 21篇 |
药学 | 107篇 |
中国医学 | 10篇 |
肿瘤学 | 108篇 |
出版年
2022年 | 16篇 |
2021年 | 51篇 |
2020年 | 30篇 |
2019年 | 39篇 |
2018年 | 59篇 |
2017年 | 42篇 |
2016年 | 44篇 |
2015年 | 56篇 |
2014年 | 54篇 |
2013年 | 130篇 |
2012年 | 104篇 |
2011年 | 112篇 |
2010年 | 122篇 |
2009年 | 112篇 |
2008年 | 100篇 |
2007年 | 114篇 |
2006年 | 96篇 |
2005年 | 101篇 |
2004年 | 82篇 |
2003年 | 81篇 |
2002年 | 75篇 |
2001年 | 72篇 |
2000年 | 80篇 |
1999年 | 62篇 |
1998年 | 98篇 |
1997年 | 83篇 |
1996年 | 86篇 |
1995年 | 54篇 |
1994年 | 66篇 |
1993年 | 56篇 |
1992年 | 36篇 |
1991年 | 43篇 |
1990年 | 35篇 |
1989年 | 54篇 |
1988年 | 53篇 |
1987年 | 40篇 |
1986年 | 33篇 |
1985年 | 32篇 |
1984年 | 31篇 |
1983年 | 16篇 |
1982年 | 23篇 |
1981年 | 19篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1978年 | 17篇 |
1977年 | 19篇 |
1976年 | 17篇 |
1975年 | 17篇 |
1973年 | 20篇 |
1972年 | 14篇 |
排序方式: 共有2983条查询结果,搜索用时 15 毫秒
91.
Background : Knowledge of the levels of inbreeding in the human population is interesting because it is one of the characteristics that conditions its genetic structure and has important genetic-medical repercussions in the descendants of marriages between close relatives. Galicia (north-west Spain) is a region with very special geographic, historic and social characteristics that makes it particularly interesting for consanguinity studies. Primary objective : The object of this investigation is the study of the levels of inbreeding and the structure of consanguinity in rural area of the Dioceses of Ourense (Galicia) during the period 1900-1979. Subjects and methods : In the study, data corresponding to 437 parishes, integrated in 80 municipalities of the rural area of the Dioceses of Ourense were analysed. In the period studied, of a total of 110 128 marriages, 9010 took place between biologically related individuals up to the level of second cousins. The rate of consanguinity and the average coefficient of inbreeding of the population, as well as the percentage of the different types of consanguineous marriages, were calculated. Main outcomes and results : The rate of consanguinity for the period 1900-1979 is 8.18% and the average coefficient of inbreeding is 3.0662 2 10 m 3. The most frequent type of consanguineous marriage is between second cousins (4.00% of all marriages). There is a notably high frequency of marriages of multiple relationships (0.52%) and the frequency of uncle-niece or aunt-nephew marriages is 0.16%. The average value of the M22/M33 ratio is 0.66 and during the 80 years studied, with regard to the temporal variation of the average coefficient of inbreeding, the annual values followed a polynomial curve with an inflection point in 1921. Conclusions : The highest values of consanguinity detected in Galicia, for the same period, were registered in the Dioceses of Ourense and the high rate of uncle-niece or aunt-nephew marriages habitual in this region was confirmed. The latter is explained by the important incidence in the Galician population of the migration to America at the end of the 19th and beginning of the 20th century. However, when the relative frequency of this type of marriage with respect to the total number of consanguineous marriages is calculated, it has relatively low values due to the high proportion of marriages between second cousins and marriages of multiple relationships, the highest in Galicia for an equal period of time. The rate of marriages between first cousins is also the highest in Galicia, confirming a phenomenon that appears to be common in the rural areas of the northern area of the Iberian Peninsula. 相似文献
92.
Dr. Töres Theorell M.D. Dr. Richard H. Rahe MC USNR 《Behavioral medicine (Washington, D.C.)》2013,39(3):18-24
Abstract Thirty-six men and women who experienced a documented myocardial infarction, half of whom ultimately died from their disease and half of whom survived over a six-year period, provided longitudinal recent life changes and ballistocardiographic data. The 18 patients who died from their coronary disease indicated a significant buildup in life changes which peaked approximately one year prior to death; their serial ballistocardiograms indicated a significant buildup in average force of contraction which was seen to peak approximately six months prior to death. The 18 post-infarction patients who survived the six-year follow-up showed neither a buildup in life change nor a buildup in the ballistocardiographic index of cardiac contraction force. These findings of a life change peak preceding ballistocardiographic evidence of an “overworked” heart are discussed in terms of their possible medical and psychophysiological significances. 相似文献
93.
AMJ van Wegberg RAF Evers JGM Burgerhof E van Dam M.R. Heiner-Fokkema MCH Janssen MC de Vries FJ van Spronsen 《Molecular genetics and metabolism》2021,132(1):49-55
BackgroundIn patients with phenylketonuria, stability of blood phenylalanine and tyrosine concentrations might influence brain chemistry and therefore patient outcome. This study prospectively investigated the effects of tetrahydrobiopterin (BH4), as a chaperone of phenylalanine hydroxylase on diurnal and day-to-day variations of blood phenylalanine and tyrosine concentrations.MethodsBlood phenylalanine and tyrosine were measured in dried blood spots (DBS) four times daily for 2 days (fasting, before lunch, before dinner, evening) and once daily (fasting) for 6 days in a randomized cross-over design with a period with BH4 and a period without BH4. The sequence was randomized. Eleven proven BH4 responsive PKU patients participated, 5 of them used protein substitutes during BH4 treatment. Natural protein intake and protein substitute dosing was adjusted during the period without BH4 in order to keep DBS phenylalanine levels within target range. Patients filled out a 3-day food diary during both study periods. Variations of DBS phenylalanine and Tyr were expressed in standard deviations (SD) and coefficient of variation (CV).ResultsBH4 treatment did not significantly influence day-to-day phenylalanine and tyrosine variations nor diurnal phenylalanine variations, but decreased diurnal tyrosine variations (median SD 17.6 μmol/l, median CV 21.3%, p = 0.01) compared to diet only (median SD 34.2 μmol/l, median CV 43.2%). Consequently, during BH4 treatment diurnal phenylalanine/tyrosine ratio variation was smaller, while fasting tyrosine levels tended to be higher.ConclusionBH4 did not impact phenylalanine variation but decreased diurnal tyrosine and phenylalanine/tyrosine ratio variations, possibly explained by less use of protein substitute and increased tyrosine synthesis. 相似文献
94.
95.
Randle C. Johnson M.D. Major USAF MC Michael H. Bleshman M.D. James W. DeFord M.D. 《Diseases of the colon and rectum》1978,21(7):510-513
Summary We have presented an unusual case of benign lymphoid hyperplasia, which manifested as a cecal deformity in a 15-year-old boy.
The clinical manifestation may have been related to partial occlusion of the appendiceal orifice. In future cases of benign
lymphoid hyperplasia, colonoscopy may be diagnostic, and if it is used for continuing observation, may avert unnecessary surgical
procedures in children and young adults. 相似文献
96.
LTC Lawrence F. Johnson MC USA LTC Tom R. Demeester MC USA MAJ Roger C. Haggitt MC USA 《Digestive diseases and sciences》1978,23(6):498-509
Exposure of the distal esophageal mucosa to acid gastric juice was quantitated by 24-hr pH monitoring in 100 individuals and was correlated with morphologic data derived from esophageal biopsies. The degree of acid exposure to the distal esophagus correlated directly with increases in both relative and absolute length of the subepithelial papillae and to relative basal zone hyperplasia. Both papillary length and basal zone hyperplasia decreased after antireflux surgery had reduced acid exposure to normal. Reflux in the recumbent position resulted in prolonged exposure of the mucosa to acid because of poor acid clearing from the esophagus. This caused longer papillae than did upright reflux, where there were more frequent reflux episodes, but with rapid acid clearance. The presence of a hiatal hernia was associated with longer papilae, lower DES pressure, increased reflux frequency, and prolonged recumbent acid clearance. Twenty-four hour pH monitoring correlated better with papillary length than did symptoms or other clinical measures of gastroesophageal reflux. 相似文献
97.
Platelet alpha-granule and plasma membrane share two new components: CD9 and PECAM-1 总被引:1,自引:2,他引:1
CD9 (p24) and PECAM1 (CD31) antigens are well-defined components of the platelet plasma membrane. Both are integral glycoproteins (GPs) implicated in the adhesive and aggregative properties of human platelets. In the present report, we have investigated their subcellular localization using immunoelectron microscopy. The monospecificity of the two polyclonal antibodies used was confirmed by immunoblotting. On normal resting platelets, immunolabeling for CD9 and PECAM1 was found lining the plasma membrane and the luminal face of the open canalicular system. Some labeling was also consistently found on the alpha-granule limiting membrane. This was confirmed by double labeling experiments in which fibrinogen and von Willebrand factor (vWF) were used as alpha-granule markers. CD9 and PECAM-1 were found lining the membrane of the same granules that contained fibrinogen and vWF in their matrix. CD9 and PECAM-1 thus appear to have an intracellular distribution identical to GPIIb-IIIa, a major aggregation platelet receptor. To rule out a cross-reactivity of the two polyclonal antibodies with GPIIb/IIIa, we studied PECAM1 and CD9 expression on the platelets from a patient with type I Glanzmann's thrombasthenia whose platelets are devoid of GPIIb/IIIa. The same pattern of labeling was observed for both antigens as for normal platelets. Normal platelets were further observed after stimulation by agonists that either fail to induce (ADP) or induce granule secretion (thrombin). After treatment with ADP, platelets changed shape and centralized their granules; the plasma membrane immunolabeling remained unchanged; and gold particles were still found decorating the periphery of the centralized alpha- granules. After thrombin treatment, alpha-granules fused with the platelet membrane and secretion occurred. A significant increase of labeling was then observed on the platelet surface. From these results we conclude that the alpha-granule membrane contains two additional receptors in common with the plasma membrane. This suggests that alpha- granule membrane receptors may originate from a dual mechanism: direct targeting from the Golgi complex in megakaryocytes (for alpha-granule- specific receptors such as P-selectin) or by endocytosis from the plasma membrane (for proteins distributed in the two compartments). 相似文献
98.
Analysis of exercise-induced R wave amplitude changes in detection of coronary artery disease in asymptomatic men with left bundle branch block 总被引:1,自引:0,他引:1
Gregory S. Uhl USAF MC Major J.Andrew C. Hopkirk MRCP RAF Squadron Leader 《The American journal of cardiology》1979,44(7):1247-1250
The exercise electrocardiograms of 44 asymptomatic men with acquired left bundle branch block were analyzed for changes in R wave amplitude. Results were correlated with findings on selective coronary angiography. There were two subgroups: 7 men with significant angiographic coronary artery disease (Group I) and 37 with normal coronary angiograms (Group II). Exercise induced an increase in R wave amplitude in all seven men with coronary artery disease but in only 10 of the 37 men without significant coronary artery disease. This criterion thus had a sensitivity of 100 percent but a poor specificity of 73 percent, a predictive value of 41 percent and an accuracy rate of 77 percent for the diagnosis of coronary artery disease. The greater the increase in R wave amplitude the greater was the likelihood of some degree of left ventricular dysfunction as measured by wall motion abnormalities and elevated left ventricular end-diastolic pressure. The increase in R wave amplitude with exercise appears to be a sensitive test in identifying coronary artery disease in asymptomatic men with acquired left bundle branch block. 相似文献
99.
Laura Villarreal‐Martínez Jaime García‐Chvez Berenice Snchez‐Jara Aida Mashenka Moreno‐Gonzlez Janet Soto‐Padilla Efraín Aquino‐Fernndez Rogelio Paredes‐Aguilera Karla Maldonado‐Silva Cecilia Rodríguez‐Castillejos Ana Itamar Gonzlez‐vila María Mora‐Torres Hector Manuel Tiznado‐García Natalia Elizabeth Padilla‐Durn Nuria Citlali Luna‐Silva Eric Israel Gutirrez‐Jurez Jorge Nemi‐Cueto Claudia Sofia Gmez‐Gonzlez Ricardo De Len‐Figueroa Adela Lpez‐Miranda Mirna Guadalupe Ríos‐Osuna Edna Liliana Tamez‐Gmez Elio Aarn Reyes‐Espinoza Irving Armando Domínguez‐Varela Gerardo Gonzlez‐Martínez Elias Adn Godoy‐Salinas 《Haemophilia》2020,26(2):290-297
100.
Silveira C. R. Varela Junior A. S. Corcini C. D. Soares S. L. Anciuti A. N. Kütter M. T. Martínez P. E. 《Ecotoxicology (London, England)》2019,28(8):913-922
Ecotoxicology - Bisphenol-A (BPA) is a potential endocrine disruptor besides being associated with oxidative damage in several vertebrate classes. In the present study we investigated oxidative... 相似文献