全文获取类型
收费全文 | 32106篇 |
免费 | 1491篇 |
国内免费 | 105篇 |
专业分类
耳鼻咽喉 | 372篇 |
儿科学 | 743篇 |
妇产科学 | 706篇 |
基础医学 | 4142篇 |
口腔科学 | 2176篇 |
临床医学 | 2494篇 |
内科学 | 7420篇 |
皮肤病学 | 665篇 |
神经病学 | 2285篇 |
特种医学 | 673篇 |
外科学 | 3985篇 |
综合类 | 161篇 |
一般理论 | 34篇 |
预防医学 | 3648篇 |
眼科学 | 455篇 |
药学 | 2218篇 |
中国医学 | 190篇 |
肿瘤学 | 1335篇 |
出版年
2023年 | 294篇 |
2022年 | 347篇 |
2021年 | 843篇 |
2020年 | 526篇 |
2019年 | 827篇 |
2018年 | 1290篇 |
2017年 | 782篇 |
2016年 | 835篇 |
2015年 | 1019篇 |
2014年 | 1149篇 |
2013年 | 1590篇 |
2012年 | 2593篇 |
2011年 | 2838篇 |
2010年 | 1441篇 |
2009年 | 974篇 |
2008年 | 2013篇 |
2007年 | 2082篇 |
2006年 | 1863篇 |
2005年 | 1804篇 |
2004年 | 1597篇 |
2003年 | 1441篇 |
2002年 | 1325篇 |
2001年 | 536篇 |
2000年 | 571篇 |
1999年 | 439篇 |
1998年 | 132篇 |
1997年 | 93篇 |
1996年 | 66篇 |
1995年 | 61篇 |
1994年 | 57篇 |
1993年 | 62篇 |
1992年 | 254篇 |
1991年 | 202篇 |
1990年 | 160篇 |
1989年 | 144篇 |
1988年 | 138篇 |
1987年 | 119篇 |
1986年 | 103篇 |
1985年 | 98篇 |
1984年 | 89篇 |
1983年 | 75篇 |
1979年 | 51篇 |
1977年 | 43篇 |
1976年 | 46篇 |
1975年 | 47篇 |
1974年 | 64篇 |
1971年 | 44篇 |
1970年 | 47篇 |
1968年 | 46篇 |
1967年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
41.
Marcos Barbosa-Ferreira Maria Lúcia Zaidan Dagli Paulo César Maiorka Silvana Lima Górniak 《Food and chemical toxicology》2005,43(4):497-503
Senna occidentalis (So) is a weed that grows in pastures along fences and in fields cultivated with cereals such as corn and soybean, and many reports have been showing intoxication with this plant in different animal species. It is also used in many medicinal purposes. The objective of the present study was to better evaluate the toxic effects of prolonged administration of So seeds to rats. Forty male Wistar rats were divided into four groups of 10 animals each, three of them respectively fed rations containing 1%, 2% and 4% So seeds, and the last one (control) fed commercial ration for a period of 2 weeks. Fourteen rats were also used in a pair-feeding (PF) experiment. The rats of the experimental groups showed lethargy, weakness, recumbency, depression and emaciation. Two rats of the 4% group and two of the PF group died during the experiment. Histopathological study showed fiber degenerations in the skeletal (Tibial, pectoral and diaphragm) and cardiac muscles. In the liver parenchyma, was observed vacuolar degeneration and, in the kidney, mild nefrosis in the proximal convoluted tubules. All of these alterations occurred in a dose-dependent fashion. Moderate to severe degeneration and spongiosis in the central nervous system, especially in cerebellum. Electron microscopy revealed mitochondrial lesions in all analyzed tissues. 相似文献
42.
43.
This study compared the frequency of factors and diseases that contribute to the risks of oral contraceptive use among current users and non-users of oral contraception in order to evaluate the users' awareness of factors associated with complications during oral contraceptive use. Data from 5317 current users and 8863 non-users in the state of São Paulo, Brazil, were collected using questionnaires requesting information on the following variables: use of oral contraceptives, age, weight, smoking status, and the presence or history of hypertension, diabetes, cardiopathies, painful varicose veins, and epilepsy. Half of the users had some risk factors, and 17.4% were at high risk of complications from oral contraceptive use. Risk factors and diseases which appeared to be poorly known by the population as increasing the risk of oral contraceptive use were smoking, hypertension and painful varicose veins. Only a small percentage of the population appeared to know that these diseases and factors could increase the risk of health problems during oral contraceptive use. The results suggest a lack of information among users and providers on factors which are associated with an increased risk of health problems during use of oral contraceptives.
Resumen Este estudio comparó la frecuencia de factores y enfermedades que contribuyen al riesgo de los anticonceptivos orales (AO) entre usuarias y no usuarias corrientes de anticonceptivos orales a fin de evaluar el grado de conocimiento entre las usuarias de los factores asociados con complicaciones durante el uso de AO. Se recopilaron datos de 5317 usuarias y 8863 no usuarias corrientes del Estado de S@o Paulo, Brasil, utilizando cuestionarios en los que se solicitabe información acerca de las siguientes variables: uso de AO, edad, peso, fumadora/no fumadora y la presencia o historia de hipertensión, diabetes, cardiopatías, várices dolorosas y epilepsia. La mitad de las usuarias tenían algunos factores de riesgo y el 17,4% de ellas corrían un alto riesgo de complicaciones por el uso de anticonceptivos orales. Los factores de riesgo y enfermedades que parecían ser poco conocidos por la población como tendientes a aumentar el riesgo del uso de anticonceptivos orales eran el fumar, la hipertensión y las várices dolorosas. Sólo un pequeño porcentaje de la población parecía saber que estas enfermedades y factores podían aumentar el riesgo de problemas de salud durante el uso de anticonceptivos orales. Los resultados sugieren una falta de información de las usuarias y proveedores con respecto a factores que están asociados con un riesgo mayor de problemas de salud durante el uso de anticonceptivos orales.
Resumé Pour évaluer dans quelle mesure les utilisatrices et non utilisatrices de contraceptifs oraux sont sensibilisées aux facteurs associés à des complications, cette étude a comparé la fréquence des facteurs et des maladies qui contribuent au risque que présente l'utilisation de ces contraceptifs. Dans l'Etat de Sao Paulo (Brésil), des données ont été recueillies auprès de 5317 utilisatrices et 8863 non utilisatrices, au moyen de questionnaires demandant des renseignements concernant les variables suivantes: utilisation de contraceptifs oraux, âge, poids, tabagisme, présence ou antécédents d'hypertension, diabète, cardiopathies, varices douloureuses et épilepsie. La moitié des utilisatrices présentaient certains facteurs de risque et 17,4% des facteurs de risque élevé de complications résultant de l'utilisation de contraceptifs oraux. Les facteurs de risque et les maladies dont la population semblait mal connaître l'effet d'augmentation des risques qu'entrîne l'ingestion de contraceptifs oraux étaient le tabagisme, l'hypertension et les varices douloureuses. Un faible pourcentage seulement de la population paraissait savoir que ces maladies et facteurs pouvaient accroître les risques de problèmes de santé durant l'utilisation des contraceptifs oraux. Les résultats suggèrent que les utilisatrices et les pourvoyeurs des services de contraception ne sont pas suffisamment informés des facteurs associés à un risque accru de problèmes de santé durant l'utilisation des contraceptifs oraux.相似文献
44.
S O'Núnáin N J Linker J F Sneddon N M Debbas A J Camm D E Ward 《British heart journal》1992,67(1):67-71
OBJECTIVE--To assess the effects of low energy ablation of the substrate for atrial flutter. DESIGN--Initial retrospective analysis of patients undergoing low energy ablation of the atrioventricular node for refractory atrial flutter (group 1) was followed by a prospective assessment of low energy ablation in the posterio-inferior right atrium for the same condition (group 2). SETTING--Tertiary referral centre for management of cardiac arrhythmias. PATIENTS--Seven men (aged 50-67 years) with refractory atrial flutter. INTERVENTIONS--Multiple (3-10) low energy DC shocks with a cumulative energy of 100-245 J in the region of the atrioventricular node in group 1 and 12-15 low energy DC shocks (cumulative energy 110-235 J) guided by the anatomical landmarks of the triangle of Koch and applied directly to the atrial wall. MAIN OUTCOME MEASURE--Freedom from recurrence of atrial flutter. RESULTS--In group 1 despite initial complete atrioventricular block in three patients, atrioventricular conduction had resumed in all by one month. All four, however, were in sinus rhythm at follow up six to 13 months later. Two of the three patients in group 2 were free of atrial flutter at follow up three to four months after ablation. CONCLUSION--Ablation of the atrial flutter substrate with low energy DC shocks is feasible. Precise electrophysiological mapping is not necessary. 相似文献
45.
46.
J K Sakurada A Maury W M Tamashiro P M Araújo I J Camargo H A Rangel 《Research in immunology》1992,143(2):157-164
To verify whether anti-Trypanosoma-cruzi-proteinase antibodies are able to play a role in the development of Chagas' disease, CBA/J and C57BL/6 mice were immunized with purified proteinase fractions: antibody production was studied and passive immunization experiments were carried out. No significant differences were observed in the titre, isotype composition and specificity of the antibodies produced by the mouse strains. Immune sera produced in one strain was able to protect mice of both strains, provided that the challenge did not exceed the number of parasites corresponding to 30-fold the LD50. The data presented suggest that anti-proteinase antibodies may play a role in immunoprotection. 相似文献
47.
Because of its numerous etiologies, foot dermatitis can be difficult to diagnose despite of thorough history and physical examination. The differential diagnoses are challenging and include allergic contact dermatitis, dyshidrosis, juvenile plantar dermatosis, atopic dermatitis, lichen planus.
Methods: In the Cutaneous Allergology Unit of the Department of Dermatovenereology of Pedro Hispano Hospital, between 1999 and 2003, 804 patients were observed with suspicion of contact dermatitis. In 9,3% there was a history of recurrent foot dermatitis. All these patients were patch tested with GPEDC standard and shoe series and shoe fragments.
Results: Twenty‐five patients revealed shoe contact dermatitis with positive reactions to the series tested, with an average age of 40 years. The dermatitis involved the dorsal aspect of the foot in 20 patients and the volar aspect in 8, the lateral aspects in 4, typically sparing the instep and flexural creases of the toes. The most common allergen were para‐tertiary‐butylphenol formaldehyde resin – PTBFR (12 patients‐48%), mercapto mix (7 patients‐28%), potassium dichromate (24%), mercaptobenzothiazole (24%).
Conclusions: The most common causes of shoe contact dermatitis were glues, followed by rubber components and chromated leather. As in other studies the most common allergen in shoe dermatitis in Portugal is PTBFR in neoprene adhesives. Rubber components (accelerators) were the second more frequent allergen in this study, probably a direct result of improved fixation of chrome and a change in footwear style and chrome sensitivity explains leather allergy. Other causes of foot contact dermatitis are iatrogenic complication, clothing (socks), cosmetics, adhesive tape and professional etiology. 相似文献
Methods: In the Cutaneous Allergology Unit of the Department of Dermatovenereology of Pedro Hispano Hospital, between 1999 and 2003, 804 patients were observed with suspicion of contact dermatitis. In 9,3% there was a history of recurrent foot dermatitis. All these patients were patch tested with GPEDC standard and shoe series and shoe fragments.
Results: Twenty‐five patients revealed shoe contact dermatitis with positive reactions to the series tested, with an average age of 40 years. The dermatitis involved the dorsal aspect of the foot in 20 patients and the volar aspect in 8, the lateral aspects in 4, typically sparing the instep and flexural creases of the toes. The most common allergen were para‐tertiary‐butylphenol formaldehyde resin – PTBFR (12 patients‐48%), mercapto mix (7 patients‐28%), potassium dichromate (24%), mercaptobenzothiazole (24%).
Conclusions: The most common causes of shoe contact dermatitis were glues, followed by rubber components and chromated leather. As in other studies the most common allergen in shoe dermatitis in Portugal is PTBFR in neoprene adhesives. Rubber components (accelerators) were the second more frequent allergen in this study, probably a direct result of improved fixation of chrome and a change in footwear style and chrome sensitivity explains leather allergy. Other causes of foot contact dermatitis are iatrogenic complication, clothing (socks), cosmetics, adhesive tape and professional etiology. 相似文献
48.
Luis Erik Clavería Jacinto Duarte Maria Dolores Sevillano Angel Pérez-Sempere Carmen Cabezas Fernanda Rodríguez Jesús de Pedro-Cuesta 《Movement disorders》2002,17(2):242-249
We assessed the prevalence of Parkinson's disease in Cantalejo, Spain. In 1994, we screened 1,579 persons (age > or = 40 years) using a high-sensitivity method. Cases fulfilling established clinical criteria were followed for a minimum of 3 years. Prevalences were compared with those from other door-to-door surveys. We detected 27 individuals with parkinsonism, 20 of whom had Parkinson's disease. The prevalence of Parkinson's disease increased with age and, when age-adjusted to European standards, was 9.01 per 1,000 (age 40 years and over; 10.78 in men and 5.23 in women). Of the 11 men, three were in Hoehn & Yahr grades III-IV, but six of the nine women were more severely affected. Overall, we found 18 newly diagnosed cases of parkinsonism, 13 of which were Parkinson's disease, and the majority of which were in men aged 80 years or older with a mean duration of illness of 5 years. Our prevalence figures are the highest reported, apparently because of the inclusion of several very elderly men. Parkinson's disease in Cantalejo is less severe in men than in women, particularly in those newly diagnosed. Despite the low numbers, the high prevalence and sex-related pattern are unexplained but they probably relate to the high sensitivity of the screening method. 相似文献
49.
The tetanic (tta; X.-52.6) mutation has been isolated on the basis of its sensitivity to extradoses of the normal Shaker gene complex (ShC) where the K+ channel la is encoded. The mutant shows up to threefold elevation of the membrane bound protein phosphatase type 1 (PP1) activity in body extracts, probably due to reduced levels of the PP1 specific inhibitor 2 (I-2). By contrast, PP1 activity in the head is only half of the normal value. In addition, tta fails to perform normally in a negative reinforcement olfactory paradigm. The functional relationships between phosphorylation, K+ currents, phosphatase activity and modulation of synaptic activity during learning and memory are discussed in the light of their possible genetic links. 相似文献
50.
Activins are members of the transforming growth factor-beta (TGFbeta) superfamily, which regulate cell differentiation processes. Here we report the first quantitative analysis of the expression of Activin/Inhibin ligands, type I and II receptors, as well as Smad proteins in fetal (E14-E16) and adult thymic subpopulations. Our data showed that Alk4, ActRIIA, ActRIIB, and Smads 2, 3, and 4, are expressed in fetal thymus (E14 > E15 > E16) and in thymocytes from adult mice (mostly in the double negative [DN] subpopulation). Ligand expression analysis showed that betaA, betaB, and alpha subunits were mainly detected in thymic stromal cells. Interestingly, alpha subunits were expressed at much higher levels compared to betaA and betaB subunits, demonstrating for the first time the potential role of Inhibins as important mediators during early T cell development. Our data indicate that Activin/Inhibin signaling could regulate the process of thymus organogenesis and early thymocyte differentiation, as it has been demonstrated for other members of the TGF-beta superfamily. 相似文献