全文获取类型
收费全文 | 2358629篇 |
免费 | 169811篇 |
国内免费 | 4889篇 |
专业分类
耳鼻咽喉 | 31832篇 |
儿科学 | 73408篇 |
妇产科学 | 63612篇 |
基础医学 | 335255篇 |
口腔科学 | 70165篇 |
临床医学 | 211239篇 |
内科学 | 459043篇 |
皮肤病学 | 52328篇 |
神经病学 | 183172篇 |
特种医学 | 89578篇 |
外国民族医学 | 319篇 |
外科学 | 362979篇 |
综合类 | 52835篇 |
现状与发展 | 6篇 |
一般理论 | 736篇 |
预防医学 | 171005篇 |
眼科学 | 56269篇 |
药学 | 175840篇 |
10篇 | |
中国医学 | 5971篇 |
肿瘤学 | 137727篇 |
出版年
2019年 | 17946篇 |
2018年 | 26206篇 |
2017年 | 20074篇 |
2016年 | 22133篇 |
2015年 | 25359篇 |
2014年 | 34863篇 |
2013年 | 50868篇 |
2012年 | 70341篇 |
2011年 | 73957篇 |
2010年 | 43888篇 |
2009年 | 41217篇 |
2008年 | 69522篇 |
2007年 | 73625篇 |
2006年 | 74463篇 |
2005年 | 71153篇 |
2004年 | 68752篇 |
2003年 | 65374篇 |
2002年 | 63290篇 |
2001年 | 125508篇 |
2000年 | 128597篇 |
1999年 | 106601篇 |
1998年 | 27322篇 |
1997年 | 23879篇 |
1996年 | 23980篇 |
1995年 | 22907篇 |
1994年 | 21001篇 |
1993年 | 19431篇 |
1992年 | 80888篇 |
1991年 | 77889篇 |
1990年 | 75030篇 |
1989年 | 72441篇 |
1988年 | 65924篇 |
1987年 | 64311篇 |
1986年 | 60552篇 |
1985年 | 57559篇 |
1984年 | 42016篇 |
1983年 | 35773篇 |
1982年 | 19686篇 |
1979年 | 37286篇 |
1978年 | 25600篇 |
1977年 | 21805篇 |
1976年 | 19973篇 |
1975年 | 21309篇 |
1974年 | 25843篇 |
1973年 | 24741篇 |
1972年 | 23136篇 |
1971年 | 21562篇 |
1970年 | 20239篇 |
1969年 | 18925篇 |
1968年 | 17517篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
981.
982.
983.
984.
AIM: To undertake a systematic review of the diagnostic performance of clinical examination, sample acquisition and sample analysis in infected foot ulcers in diabetes. METHODS: Nineteen electronic databases plus other sources were searched. To be included, studies had to fulfil the following criteria: (i) compare a method of clinical assessment, sample collection or sample analysis with a reference standard; (ii) recruit diabetic individuals with foot ulcers; (ii) present 2 x 2 diagnostic data. Studies were critically appraised using a 12-item checklist. RESULTS: Three eligible studies were identified, one each on clinical examination, sample collection and sample analysis. For all three, study groups were heterogeneous with respect to wound type and a small proportion of participants had foot ulcers due to diabetes. No studies identified an optimum reference standard. Other methodological problems included non-blind interpretation of tests and the time lag between index and reference tests. Individual signs or symptoms of infection did not prove to be useful tests when assessed against punch biopsy as the reference standard. The wound swab did not perform well when assessed against tissue biopsy. Semiquantitative analysis of wound swab might be a useful alternative to quantitative analysis. The limitations of these findings and their impact on recommendations from relevant clinical guidelines are discussed. CONCLUSION: Given the importance of this topic, it is surprising that only three eligible studies were identified. It was not possible to describe the optimal methods of diagnosing infection in diabetic patients with foot ulceration from the evidence identified in this systematic review. 相似文献
985.
986.
987.
G. B. Slepchenko L. S. Anisimova V. F. Slipchenko E. V. Mikheeva N. P. Pikula 《Pharmaceutical Chemistry Journal》2005,39(3):166-168
Rapid voltammetric procedures for the determination of water-soluble vitamins C, B1, and B2, fat-soluble vitamin E (α-tocopherol acetate), and quercetin in bioactive food additives have been developed. The systematic error (i.e., correctness) of the proposed procedures was evaluated using certified reference materials and the additive recovery tests, which gave the following limiting metrological characteristics: relative error, 25 %; reproducibility, 28 %; convergence, 22 %. The full analysis time (with sample preparation) did not exceed 2 hours. Voltammetric determinations under optimum conditions can be performed in the automated regime controlled by a computer according to the specially developed software.__________Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 39, No. 3, pp. 54 – 56, March, 2005. 相似文献
988.
R Tootla G Kotru M A Connolly M S Duggal K J Toumba 《European journal of paediatric dentistry》2005,6(3):139-143
AIM: The purpose of this pilot study was to identify the subsurface enamel demineralising potential of two possible acidogenic lactose-based powders and their corresponding generic pump inhalers. METHODS: Ten healthy non-asthmatic adults participated in a 5- leg randomised crossover study including a 10% sucrose control. A twice-daily 400 microg dose of inhaler was applied in vitro to a demineralised enamel slab on the buccal flange of a mandibular removable appliance before in situ placement for 14 days each. Lesion parameters were determined using transverse microradiography and digitised image analysis. RESULTS: Minimal demineralisation occurred with sucrose, both pump and one powder inhaler. The remaining powder was associated with remineralisation (p = 0.29). Overall, mean lesion depth increased (p = 0.12). CONCLUSION: Asthma inhalers failed to demonstrate a significant acidogenic/cariogenic effect. 相似文献
989.
Lawrence S Prince Heather I Dieperink Victor O Okoh German A Fierro-Perez Roger L Lallone 《Developmental dynamics》2005,233(2):553-561
We tested the hypothesis that innate immune signaling in utero could disrupt the structural development of the fetal lung, contributing to the pathogenesis of bronchopulmonary dysplasia. Injection of Escherichia coli lipopolysaccharide (LPS) into the amniotic fluid of E15 BALB/cJ mice increased the luminal volume density of fetal mouse lungs at embryonic day (E) 17 and E18. LPS also increased luminal volume and decreased distal lung branching in fetal mouse lung explants. This effect required NF-kappaB activation and functional Toll-Like Receptor 4. Airway branching may require fibronectin-dependent epithelial-mesenchymal interactions, representing a potential target for innate immune signaling. Anti-fibronectin antibodies and LPS both blocked distal lung branching. By immunofluorescence, fibronectin localized to the clefts between newly formed airways but was restricted to peripheral mesenchymal cells in LPS-exposed explants. These data suggest that LPS may alter the expression pattern of mesenchymal fibronectin, potentially disrupting epithelial-mesenchymal interactions and inhibiting distal airway branching and alveolarization. This mechanism may link innate immune signaling with defects in structural development of the fetal lung. 相似文献
990.
A T Lee 《Aviation, space, and environmental medicine》1991,62(2):158-161
In-flight encounters with hazardous weather represent one of the most significant safety issues in civil aviation operations. Aircrew judgment is often cited as the probable cause of incidents and accidents involving weather, although lack of information is also a factor. The present study examines how information, presented at different times and in different forms, affects the awareness and decision-making behavior of aircrews in a flight simulation study of a recent microburst/windshear incident. In order to examine the influence of enhanced information transfer on aircrew behavior, intracrew communications and approach-to-land decisions were evaluated with conventional ATC communications and with automated cockpit alerting and display of weather information. Results of the study revealed that aircrews provided only with conventional ATC transmissions of weather information had difficulty discriminating conditions conducive to microburst events from less hazardous windshear events. Improved situation awareness for microburst events was found when ground-based convective weather information was provided in real time to aircrews. Avoidance decision-making was found to be less efficient with conventional ATC alert transmissions when compared to the performance of crews provided with a visual display of microburst events. The importance of information transfer on aircrew situation awareness and decision-making in hazardous weather avoidance is discussed. 相似文献