全文获取类型
收费全文 | 745253篇 |
免费 | 318232篇 |
国内免费 | 57927篇 |
专业分类
耳鼻咽喉 | 7709篇 |
儿科学 | 12868篇 |
妇产科学 | 5180篇 |
基础医学 | 116992篇 |
口腔科学 | 12544篇 |
临床医学 | 116772篇 |
内科学 | 133582篇 |
皮肤病学 | 10698篇 |
神经病学 | 32423篇 |
特种医学 | 28003篇 |
外国民族医学 | 3篇 |
外科学 | 81901篇 |
综合类 | 192539篇 |
现状与发展 | 134篇 |
一般理论 | 5篇 |
预防医学 | 103939篇 |
眼科学 | 24239篇 |
药学 | 118999篇 |
865篇 | |
中国医学 | 86140篇 |
肿瘤学 | 35877篇 |
出版年
2023年 | 8747篇 |
2022年 | 19657篇 |
2021年 | 24160篇 |
2020年 | 23514篇 |
2019年 | 19587篇 |
2018年 | 20743篇 |
2017年 | 25277篇 |
2016年 | 20667篇 |
2015年 | 30221篇 |
2014年 | 36525篇 |
2013年 | 43325篇 |
2012年 | 58011篇 |
2011年 | 62698篇 |
2010年 | 61135篇 |
2009年 | 65181篇 |
2008年 | 53869篇 |
2007年 | 48549篇 |
2006年 | 43364篇 |
2005年 | 35898篇 |
2004年 | 28661篇 |
2003年 | 24361篇 |
2002年 | 21018篇 |
2001年 | 22276篇 |
2000年 | 15052篇 |
1999年 | 15085篇 |
1998年 | 14237篇 |
1997年 | 14039篇 |
1996年 | 15150篇 |
1995年 | 15280篇 |
1994年 | 15025篇 |
1993年 | 13681篇 |
1992年 | 12848篇 |
1991年 | 12214篇 |
1990年 | 11175篇 |
1989年 | 11017篇 |
1988年 | 10569篇 |
1987年 | 9908篇 |
1986年 | 9412篇 |
1985年 | 8480篇 |
1984年 | 6543篇 |
1983年 | 6558篇 |
1982年 | 7618篇 |
1981年 | 7144篇 |
1980年 | 6813篇 |
1979年 | 6642篇 |
1978年 | 5820篇 |
1977年 | 6126篇 |
1976年 | 5747篇 |
1975年 | 5483篇 |
1974年 | 5034篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Palytoxin, a highly toxic natural product isolated from zoanthids of the genus Palythoa, is accumulated by a wide range of fishes and marine invertebrates used as food in the Indo-Pacific. It is responsible for many incidents of human morbidity and mortality. The toxin is a potent smooth muscle spasmogen. The cause of the contraction of smooth muscle is unclear, but recent work strongly suggests that it is primarily initiated by the release of neurotransmitters from the motor innervation of the smooth muscle. We show here that palytoxin caused the swelling of the muscle cells and some internal organelles of the anococcygeus muscle of the rat, but no substantial structural damage to the tissue. Axons and Schwann cells were also swollen but the most dramatic feature was the depletion of synaptic vesicles from putative release sites in the axons. Some axons were physically damaged following exposure to the toxin, but this was relatively uncommon (<10% of all axons studied). In the majority of axons there was no damage to nerve terminal membranes, but there was damage to mitochondria. The depletion of vesicles involved all types – clear, dense-cored, large and small. Our observations and pharmacological data gathered elsewhere, provide a neuropathological basis for the spasmogenic activity of palytoxin. 相似文献
83.
The value of ultrasound in the diagnosis of a large rapidly growing thyroid mass was assessed in a study of 42 patients with a large (> 3 cm) rapidly growing (< two months) solitary mass. Haemorrhage into a thyroid nodule was present in 31 patients and thyroid malignancy in 11. Ultrasound of haemorrhage into a thyroid nodule revealed a large cystic mass in all 31 patients containing internal debris (22), septations (three), or a combination of both (six). The malignant causes of a large rapidly growing mass were lymphoma (two), anaplastic carcinoma (four) and metastasis (five). Ultrasound of these thyroid malignancies revealed a mass with a smooth, well-defined margin and strikingly low homogeneous echogenicity in all cases. Patients with thyroid metastases had evidence of widespread metastatic disease elsewhere. Lymphoma was differentiated from anaplastic carcinoma on fine-needle aspiration cytology or surgical biopsy. Ultrasound was of value in differentiating between a benign haemorrhagic nodule and a malignant tumour. The various malignant tumours had similar appearances, however, and could not be distinguished on ultrasound. 相似文献
84.
85.
Emergency physicians and sexual involvement with patients: an Ontario survey 总被引:2,自引:1,他引:1 下载免费PDF全文
OBJECTIVE: To describe Ontario emergency physicians' knowledge of colleagues' sexual involvement with patients and former patients, their own personal experience of such involvement, and their attitudes toward postvisit relationships. DESIGN: Mailed survey. SETTING: Ontario. PARTICIPANTS: Emergency physicians practising in Ontario. RESULTS: Of 974 eligible mailed surveys, 599 (61.5%) were returned. Of these respondents, 52 (8.7%) reported being aware of a colleague in emergency practice who had been sexually involved with a patient or former patient. When describing their own behaviour, 37 respondents (6.2%) reported sexual involvement with a former patient. However, of this group, only 9 (25.0%) had met the patient in an emergency department. Thus, of the total number of respondents, only 1.5% (9/599) reported sexual involvement arising out of an emergency department visit. Most respondents (82.4%) agreed that it is inappropriate behaviour to ask a patient for a date after an emergency assessment and before the patient's departure, and 66.4% felt that it is inappropriate to contact the patient after discharge. However, only 10.6% believed it to be unacceptable to request a social meeting after encountering a patient previously cared for in the emergency department in a nonprofessional setting. Most respondents (96.5%) did not believe that sexual involvement could ever be therapeutic for the patient. However, only 66% felt that it was always an abuse of power and 62.4% supported zero tolerance of all sexual involvement between physicians and patients. CONCLUSIONS: Vague regulatory guidelines currently in place have failed to dispel confusion regarding what is acceptable social behaviour for physicians providing emergency care. Our results support the need for clarification, and suggest a basis for guidelines that would be acceptable to the emergency medical community: that an emergency visit should not form the basis for the initiation of personal or sexual relationships, yet neither should it preclude their development in nonmedical settings. 相似文献
86.
87.
Transplacental IgG Subclass Concentrations in Pregnancies at Risk of Haemolytic Disease of the Newborn 总被引:5,自引:0,他引:5
A. Lubenko Marcela Contreras C.H. Rodeck U. Nicolini Julia Savage and H. Chana 《Vox sanguinis》1994,67(3):291-298
The relationship of haemolytic disease of the newborn (HDN) to the transplacental passage of the four IgG subclasses was assessed at varous gestational ages by comparing the maternal and fetal IgG subclass concentrations in 34 pregnancies at risk of HDN with those in 30 pregnancies not at risk. Higher maternal and fetal IgG1 levels were attained in pregnancies at risk of HDN than in pregnancies not at risk. In contrast, a slight decrease in maternal IgG2 and IgG4 levels occurred in pregnancies at risk of HDN, as compared with a slight rise in maternal IgG2 and IgG4 levels in pregnancies not at risk of HDN. Changes in fetal IgG2 and 4 concentrations in either type of pregnancy were very similar, showing only slight increases between the 19th and 34th week of gestation. A slight decrease in maternal IgG3 occurred in both types of pregnancy. In contrast, higher and fairly steady levels of fetal IgG3 were observed in fetuses not at risk of HDN throughout gestation, when compared with those in 'at risk' pregnancies. However, the statistical reliability of these results is not clear since only small numbers of samples were tested and because wide variations in IgG concentrations were observed. The IgG subclass concentrations in 50 paired maternal and cord blood samples were also measured and revealed that IgG1 levels were substantially higher in cord rather than maternal blood; cord and maternal IgG2, 3 and 4 levels, on the other hand, were fairly similar. 相似文献
88.
Nasal masks for domiciliary positive pressure ventilation: patient usage and complications. 总被引:2,自引:1,他引:1 下载免费PDF全文
BACKGROUND--Nasal mask discomfort is a major factor in compliance with treatment by nasal intermittent positive pressure ventilation (NIPPV) and nasal continuous positive airway pressure (CPAP). METHODS--A study of skin complications resulting from mask usage, with particular reference to predisposing factors, was carried out in 66 patients by means of a postal questionnaire. An effective means of managing ulceration at the nasal bridge while continuing therapy is described. RESULTS--Some disruption of treatment due solely to mask discomfort was experienced by 35 patients (53%), consisting of broken skin or open sores in 11 cases (17%). CONCLUSIONS-Although complications resulting from nasal mask usage are common, early identification of patients at risk of developing such complications and appropriate intervention will result in improved patient compliance. 相似文献
89.
F W Fraunfelder F T Fraunfelder D R Illingworth 《The British journal of ophthalmology》1995,79(1):54-56
In a retrospective survey of patients taking medication for hyperlipidaemia, those taking niacin (nicotinic acid) were more likely (p < 0.05) to report sicca syndromes, blurred vision, eyelid oedema, and macular oedema compared with those who never took niacin. Additionally, 7% of those taking niacin discontinued the drug owing to adverse ocular side effects, while none of the other lipid lowering agents were found to cause these side effects (p = 0.016). Data from spontaneous reporting systems support a possible association of decreased vision, cystoid macular oedema, sicca-like symptoms, discoloration of the eyelids with or without periorbital or eyelid oedema, proptosis, loss of eyebrow or eyelashes, and superficial punctate keratitis with the use of niacin in high doses. Decreased vision may be marked, and if the drug is not discontinued, may progress to cystoid macular oedema. All ocular side effects listed above are reversible if the association with niacin is recognised and the drug is discontinued; both the incidence and severity of the ocular side effects seem to be dose dependent. 相似文献
90.
目的 检测亚硒酸钠是否能够削弱或解除顺铂对植物血球凝激素(PHA)刺激的人体外周血淋巴细胞的增殖抑制。方法 用顺铂和亚硒酸钠单独或联合处理PHA刺激的人体外周血淋巴细胞,顺铂(0.05,0.20,0.50mg/L)在细胞培养24h时加入,亚硒酸钠(0.05mg/L)在不同处理中分别在细胞培养开始时加入或与顺铂同时加入;培养72h后检测转化淋巴细胞的有丝分裂指数。结果0.05mg/L亚硒酸钠在培养开始时加入,PHA刺激转化的淋巴细胞有丝分裂指数较对照增长42.8%(P<0.05),与顺铂同时加入,有丝分裂指数增长13.7%(P>0.05)。0.05与0.20mg/L顺铂处理细胞,有丝分裂指数未发生显性改变,当顺铂剂量为0.50mg/L时,细胞有丝分裂指数较对照降低54.5%(P<0.001)。亚硒酸钠预处理细胞可以解除0.50mg/L顺铂所致的细胞增殖抑制,使有丝分裂指数恢复正常,但亚硒酸钠与顺铂同时加入时,被顺铂抑制的有丝分裂指数只能部分提高。结论0.05mg/L亚硒酸钠单独作用于淋巴细胞可直接促进细胞增殖,与顺铂联合处理细胞时,可降低顺铂毒性,拮抗顺铂的抗增殖作用。亚硒酸钠在细胞培养开始时加入培养体系效果更佳。 相似文献