全文获取类型
收费全文 | 20469篇 |
免费 | 1679篇 |
国内免费 | 54篇 |
专业分类
耳鼻咽喉 | 293篇 |
儿科学 | 665篇 |
妇产科学 | 458篇 |
基础医学 | 3083篇 |
口腔科学 | 288篇 |
临床医学 | 1959篇 |
内科学 | 3970篇 |
皮肤病学 | 303篇 |
神经病学 | 2039篇 |
特种医学 | 703篇 |
外科学 | 2726篇 |
综合类 | 631篇 |
现状与发展 | 1篇 |
一般理论 | 29篇 |
预防医学 | 1608篇 |
眼科学 | 553篇 |
药学 | 1377篇 |
中国医学 | 48篇 |
肿瘤学 | 1468篇 |
出版年
2022年 | 202篇 |
2021年 | 395篇 |
2020年 | 235篇 |
2019年 | 364篇 |
2018年 | 432篇 |
2017年 | 283篇 |
2016年 | 371篇 |
2015年 | 420篇 |
2014年 | 533篇 |
2013年 | 853篇 |
2012年 | 1210篇 |
2011年 | 1130篇 |
2010年 | 691篇 |
2009年 | 655篇 |
2008年 | 1094篇 |
2007年 | 1099篇 |
2006年 | 984篇 |
2005年 | 1072篇 |
2004年 | 1071篇 |
2003年 | 1008篇 |
2002年 | 929篇 |
2001年 | 406篇 |
2000年 | 419篇 |
1999年 | 365篇 |
1998年 | 241篇 |
1997年 | 181篇 |
1996年 | 192篇 |
1995年 | 187篇 |
1994年 | 151篇 |
1993年 | 173篇 |
1992年 | 290篇 |
1991年 | 261篇 |
1990年 | 279篇 |
1989年 | 270篇 |
1988年 | 242篇 |
1987年 | 237篇 |
1986年 | 223篇 |
1985年 | 250篇 |
1984年 | 190篇 |
1983年 | 159篇 |
1982年 | 163篇 |
1981年 | 165篇 |
1980年 | 151篇 |
1979年 | 140篇 |
1978年 | 107篇 |
1977年 | 108篇 |
1976年 | 131篇 |
1975年 | 118篇 |
1974年 | 139篇 |
1973年 | 107篇 |
排序方式: 共有10000条查询结果,搜索用时 703 毫秒
991.
992.
This cross-sectional study, carried out during July 1997-June 1998, evaluated the effects of prolonged breast-feeding and lactational amenorrhoea on bone mineral density (BMD) in 400 marginally-nourished Bangladeshi women aged 20-81 years. A bone densitometer was used for measuring BMD in the distal and ultra-distal end of radius and ulna. The results showed that the women who breastfed for 60 months or less had a higher mean BMD compared to those who breastfed for 61-120 months and for over 120 months. There was a significantly higher BMD in the women who had a shorter duration of lactational amenorrhoea compared to those having a longer duration of lactational amenorrhoea. BMD was significantly and negatively correlated with total duration of lactational amenorrhoea (slope -0.024, p<0.05) after controlling for parity, physical workload, and total duration of breast-feeding. The study concluded that there was a negative correlation between longer duration of breast-feeding and BMD, but it was not found when other factors were controlled in multivariate analysis. The duration of lactational amenorrhoea, which is a proxy indicator of breast-feeding, showed a negative correlation with BMD. It is recommended that all lactating women be given diet with adequate calcium to support breast-feeding for maintaining good nutrition of their bones. 相似文献
993.
Beck RW 《Current opinion in ophthalmology》2002,13(5):337-340
The Pediatric Eye Disease Investigator Group (PEDIG) is a network of university-based and community-based pediatric eye care practitioners that is conducting multiple clinical research studies. The group has conducted the Congenital Esotropia Observational Study, which assessed the early course of esotropia in infants, and the Amblyopia Treatment Studies, a series of randomized trials, the first of which compared atropine and patching for treatment of moderate amblyopia in children 3 to <7 years old. Herein, the results of these studies are summarized, and the current and future studies of the group are described. 相似文献
994.
Desogestrel (DG), a 19-nor progestin, is widely used in replacement therapy as a contraceptive steroidal hormone. Considering the importance of its partition coefficient parameter (log P = 5.68), a significant contributor to its action mechanism, interactions of the drug with blood-lipids had been investigated using phospholipid binding, fatty acid composition and peroxidation phenomena as the parameters under investigation to explain its pharmacodynamic behavior. From the present investigation, it was observed that lipid loss after incubation of whole blood with DG (80 ng/ml, effective contraceptive concentration in blood) for varying periods of time was accompanied with significant changes in fatty acid composition, which may be ascribed to binding affinity of DG with lipid constituents in blood that may have a role in the mediation of its therapeutic effect. Lipid peroxidation induction potential of DG has been quantitatively measured in the context of its toxicity. The results reveal that DG caused significant extent of lipid peroxidation. Ascorbic acid, an antioxidant, at equivalent human dose of 250 mg could significantly reduce DG-induced lipid peroxidation. 相似文献
995.
PURPOSE: To determine the reproducibility of anterior sclerokeratectomy using a portable nonelectric microkeratome-based device capable of harvesting the entire anterior corneal surface for lamellar transplantation. METHODS: A modified gas turbine-driven microkeratome (LSK One, Moria/Microtech, Doylestown, PA) with a redesigned head large enough to incorporate the whole human anterior corneal surface in a pass and was coupled to a manual vacuum pump. This instrument was tested on 25 fresh porcine globes divided into 2 groups (170-microm and 200-microm head). To assess cut reproducibility the physical dimensions (diameter and thickness) of the obtained lenticules were measured. RESULTS: The obtained lenticules were fairly circular (horizontal versus vertical diameters, p >0.2), with average diameters of 12.85 +/- 0.52 mm and 13.25 +/- 1.15 mm for the 170 and 200-microm heads, respectively. The average central lenticule thickness was 176.92 +/- 34.68 microm and 166.00 +/- 53.74 microm for the 170 and 200-microm heads, respectively. CONCLUSION: This new system presents an economical and portable alternative to electric-powered systems. In addition to being used by surgeons in the operating room, eye bank technicians in the field could theoretically use this system; including in developing countries where cost, availability of electricity, and portability are issues. 相似文献
996.
997.
998.
Snoeck R Andrei G Bodaghi B Lagneaux L Daelemans D de Clercq E Neyts J Schols D Naesens L Michelson S Bron D Otto MJ Bousseau A Nemecek C Roy C 《Antiviral research》2002,55(3):413-424
Human cytomegalovirus (HCMV) remains one of the major pathogens in immunocompromised patients (AIDS and transplants) and the main cause for congenital infections leading from slight cognitive defects up to severe mental retardation. The drugs that are currently available for the treatment of HCMV infections, i.e. ganciclovir, foscarnet and cidofovir, are all acting at the level of the viral DNA polymerase. Here we describe an entirely new molecule, the 2-chloro-3-pyridin-3-yl-5,6,7,8-tetrahydroindolizine-1-carboxamide (CMV423), that shows very potent in vitro activity against HCMV. CMV423 is highly active against HCMV reference strains and clinical isolates, but also against those strains, isolated from patients or emerging after in vitro selection, that are resistant to either ganciclovir, foscarnet or cidofovir. CMV423 also showed activity in two ex vivo models, that are both highly relevant for the pathophysiology of HCMV, the retinal pigment epithelial and the bone marrow stromal cell assays. Viral antigen expression analysis by flow cytometry, as well as time of addition experiments, confirmed that CMV423 acts on a step of the viral replicative cycle that precedes the DNA polymerase step and, most likely, coincides with the immediate early (IE) antigen synthesis. Finally, CMV423 combined with either ganciclovir, foscarnet or cidofovir in checkerboard experiments demonstrated a highly synergistic activity. 相似文献
999.
Priapism has been associated with many antipsychotic agents, including clozapine, risperidone, and olanzapine. This prolonged, usually painful, penile erection rarely results from the alpha-adrenergic blocking action of antipsychotics. A 22-year-old African-American man developed priapism during treatment with risperidone and, on a later occasion, during treatment with ziprasidone. The problem resolved only with substitution of other drugs for these antipsychotics. Certain patients may be more vulnerable than others to this adverse effect. Clinicians must be aware of such complications and use caution when prescribing these drugs. 相似文献
1000.
OBJECTIVE: To characterize the carotenoid content of selected components of the Mediterranean diet commonly eaten by Greek migrants to Melbourne, a population group maintaining a traditional dietary regimen, and who exhibit relatively high circulating carotenoid concentrations and low cardiovascular disease mortality. DESIGN AND SPECIMENS: Opportunistic sampling of wild (sow thistle, amaranth, purslane and dandelion, collected from roadsides and home gardens) and commercially available (chicory, endive) green leafy vegetables and figs in season. Foods were selected on the basis that they are commonly eaten by Greek migrants but not by Anglo-Celtic persons, and had not previously been well-characterized with respect to their carotenoid contents. Extra virgin, cold-pressed olive oil and 'extra light' olive oil were obtained from commercial sources. Specimens were extracted with tetrahydrofuran (or chloroform:methanol for olive oil) and carotenoid contents were quantified using HPLC with UV detection. Two to six specimens of greens and figs were analysed. Dietary intake was assessed by food frequency questionnaire. RESULTS: Wild green vegetables contained high concentrations of lutein (sow thistle>amaranth>purslane>dandelion) and beta-carotene (sow thistle>amaranth>purslane=dandelion). Sow thistle and amaranth contained lutein (15 and 13 mg/100 g, respectively) and beta-carotene (3.3 and 4.0 mg/100 g, respectively) at concentrations greater than that seen in the commercially available species of chicory and endive. Figs contained all major carotenoids appearing in plasma, albeit at low concentrations. Extra virgin cold-pressed olive oil contained substantial quantities of lutein and beta-carotene, but the more-refined 'extra light' olive oil did not. CONCLUSIONS: These components of the traditional Mediterranean diet contribute to the higher circulating concentrations of carotenoids in Greek migrants compared to Anglo-Celtic Australians. SPONSORSHIP: This study largely funded by the National Health and Medical Research Council of Australia (grant no. 974098). Extra virgin olive oil donated by Picuba Foods, Marrickville, NSW, Australia. 相似文献