全文获取类型
收费全文 | 10781篇 |
免费 | 561篇 |
国内免费 | 25篇 |
专业分类
耳鼻咽喉 | 159篇 |
儿科学 | 302篇 |
妇产科学 | 288篇 |
基础医学 | 1293篇 |
口腔科学 | 237篇 |
临床医学 | 595篇 |
内科学 | 3011篇 |
皮肤病学 | 344篇 |
神经病学 | 751篇 |
特种医学 | 176篇 |
外科学 | 1570篇 |
综合类 | 113篇 |
一般理论 | 1篇 |
预防医学 | 1065篇 |
眼科学 | 223篇 |
药学 | 670篇 |
中国医学 | 65篇 |
肿瘤学 | 504篇 |
出版年
2023年 | 73篇 |
2022年 | 49篇 |
2021年 | 242篇 |
2020年 | 120篇 |
2019年 | 311篇 |
2018年 | 479篇 |
2017年 | 246篇 |
2016年 | 267篇 |
2015年 | 239篇 |
2014年 | 296篇 |
2013年 | 410篇 |
2012年 | 681篇 |
2011年 | 767篇 |
2010年 | 400篇 |
2009年 | 262篇 |
2008年 | 637篇 |
2007年 | 641篇 |
2006年 | 714篇 |
2005年 | 661篇 |
2004年 | 605篇 |
2003年 | 570篇 |
2002年 | 517篇 |
2001年 | 367篇 |
2000年 | 448篇 |
1999年 | 318篇 |
1998年 | 49篇 |
1997年 | 39篇 |
1996年 | 26篇 |
1995年 | 19篇 |
1994年 | 23篇 |
1993年 | 24篇 |
1992年 | 102篇 |
1991年 | 87篇 |
1990年 | 96篇 |
1989年 | 65篇 |
1988年 | 55篇 |
1987年 | 60篇 |
1986年 | 61篇 |
1985年 | 46篇 |
1984年 | 26篇 |
1983年 | 24篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1976年 | 14篇 |
1974年 | 13篇 |
1973年 | 16篇 |
1971年 | 22篇 |
1970年 | 16篇 |
1969年 | 19篇 |
1967年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
31.
32.
Melatonin is a pineal hormone that regulates the human cycle of sleep and wakefulness. Plasma melatonin levels were investigated in patients with obstructive sleep apnoea syndrome (OSAS). In total, 20 patients with OSAS and 11 healthy controls were studied. OSAS patients were tested twice: on the night of diagnostic polysomnography and the night of continuous positive airway pressure (CPAP) titration. Controls were tested on one occasion. Plasma melatonin levels were determined at 23:00 h (light period), at 02:00 h (dark period) and at 06:00 h (light period) in patients and control subjects using the radioimmunoassay method. The control subjects showed a nocturnal melatonin peak value at 02:00 h (70.6+/-14 pg.mL(-1)). However, this nocturnal melatonin peak was absent in the OSAS patients. The highest melatonin value was found in OSAS patients on the night of diagnosis, at 06:00 h (49.3+/-36.8 pg.mL(-1)). It was found that the melatonin level in OSAS patients at 06:00 h was significantly lower in the night of titration (35.6+/-37.9 pg.mL(-1)) than in the diagnosis night. However, the melatonin levels at either 23:00 h or 02:00 h in OSAS patients did not differ significantly when comparing levels in the night of diagnostic polysomnography (23:00 h: 31.6+/-29.8 pg.mL(-1); 02:00 h: 47.4+/-33.8 pg.mL(-1)) with levels in the night of CPAP titration (23:00 h: 20.2+/-10.3 pg.mL(-1); 02:00 h: 37.7+/-27.5 pg.mL(-1)). Patients with obstructive sleep apnoea syndrome have an abnormal melatonin secretion pattern. The absence of a nocturnal serum melatonin peak could be partially related to the difficulty that these patients have in achieving a normal sleep-wakefulness pattern. 相似文献
33.
Alfredo Avellaneda Fernández álvaro Pérez Martín Maravillas Izquierdo Martínez Mar Arruti Bustillo Francisco Javier Barbado Hernández Javier de la Cruz Labrado Rafael Díaz-Delgado Pe?as Eduardo Gutiérrez Rivas Cecilia Palacín Delgado José Ramón Ramón Giménez Javier Rivera Redondo 《Atencion primaria / Sociedad Espa?ola de Medicina de Familia y Comunitaria》2009,41(10):e1-e5
34.
Ofelia Dolores Hernández Ángel José Gutiérrez Dailos González‐Weller Gonzalo Lozano Enrique García Melón Carmen Rubio Arturo Hardisson 《Environmental toxicology》2010,25(3):227-233
This document shows the results obtained from a study on the concentration of toxic heavy metals in the internal tissue and exoskeleton of sea urchins, collected from their natural habitat. The levels of lead and cadmium were measured by Graphite Furnace Atomic Absorption Spectrometry. The mean concentrations of lead and cadmium in the internal tissue were 304.04 and 260.54 μg/kg respectively, whereas in the shell they were 185.02 and 142.48 μg/kg. We also performed a statistical analysis of the differences in the distribution of metals between their exoskeleton and their internal content, a correlation study of the metal content in internal tissue and shell and sampling areas, and a correlation study between the metal content and sample size. Since the sea urchin Diadema antillarum presents a wide range of variation in metal content, this study suggests that this species is an excellent bioindicator of heavy metal contamination. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010. 相似文献
35.
Spermatogenic function was studied in 10 patients, previously diagnosed as having primary hypothyroidism, in whom a state of hypothyroidism has been induced by discontinuation or a decrease in treatment with levothyroxine over at least one spermatogenic cycle. Most of the patients had fathered children before the study. When the results obtained in the hypothyroid state were compared with those from a group of 16 controls with proven fertility, slight anomalies were observed; these were characterized by a decrease in seminal volume (p less than 0.05), progressive forward motility (p less than 0.01), and the cumulative percentage of mobile forms (p less than 0.01). There were no anomalies in sperm density or in the percentage of spermatozoa with normal morphology. No alterations in circulating levels of testosterone and gonadotropins existed. Induction of hypothyroidism did not lead to seminal or hormonal modifications compared with the same patients in a situation of euthyroidism. Short-term postpuberal hypothyroidism did not cause seminal alterations sufficiently intense to induce male infertility. 相似文献
36.
37.
Reliability of a Core Competency Checklist Assessment in the Emergency Department: The Standardized Direct Observation Assessment Tool 总被引:2,自引:1,他引:1
38.
39.
Miguelina Hernández Héctor Scannone Héctor J Finol Maria E Pineda Irma Fernández Alba M Vargas María E Girón Irma Aguilar Alexis Rodríguez-Acosta 《Experimental and toxicologic pathology》2007,59(2):129-137
This study explored the toxic effects of crotoxin isolated from Crotalus durissus cumanensis venom on the ultrastructure of mice cardiac autonomic nervous system. Mice were intravenously injected with saline (control group) and crotoxin diluted in saline venom (study group) at a dose of 0.107 mg/kg mouse body weight. Samples from the inter-ventricular septum were prepared for electron microscopy after 6 h (G1), 12 h (G2), 24 h (G3) and 48 h (G4). The G1 group showed some cardiomyocyte with pleomorphic mitochondria. Capillary swollen walls, nerve cholinergic endings with depleted acetylcholine vesicles in their interior and other depletions were observed. A space completely lacking in contractile elements was noticed. The G2 group demonstrated a myelinic figure, a subsarcolemic region with few myofibrils and nervous cholinergic terminal with scarce vacuoles in their interior. The G3 group demonstrated a structure with a depleted axonic terminal, mitochondrias varying in size and enhanced electron density. In addition, muscular fibers with myofibrillar structure disorganization, a depleted nervous structure surrounded by a Schwann cell along with an abundance of natriuretic peptides, were seen. An amyelinic terminal with depleted Schwann cell and with scarce vesicles was also observed. Finally, axonic lysis with autophagic vacuoles in their interior and condensed mitochondria was observed in the G4 group. This work describes the first report of ultrastructural damage caused by crotoxin on mice cardiac autonomic nervous system. 相似文献
40.