首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   202435篇
  免费   19248篇
  国内免费   11789篇
耳鼻咽喉   1582篇
儿科学   2669篇
妇产科学   2534篇
基础医学   28050篇
口腔科学   3522篇
临床医学   24156篇
内科学   29312篇
皮肤病学   2249篇
神经病学   9749篇
特种医学   7384篇
外国民族医学   96篇
外科学   20793篇
综合类   32401篇
现状与发展   44篇
一般理论   28篇
预防医学   13939篇
眼科学   4888篇
药学   22771篇
  172篇
中国医学   11156篇
肿瘤学   15977篇
  2024年   2092篇
  2023年   3091篇
  2022年   7636篇
  2021年   9914篇
  2020年   7364篇
  2019年   6467篇
  2018年   6833篇
  2017年   6245篇
  2016年   6000篇
  2015年   8570篇
  2014年   10686篇
  2013年   10518篇
  2012年   14762篇
  2011年   15696篇
  2010年   10781篇
  2009年   8762篇
  2008年   10892篇
  2007年   10947篇
  2006年   10029篇
  2005年   9144篇
  2004年   7219篇
  2003年   6912篇
  2002年   6028篇
  2001年   5010篇
  2000年   4482篇
  1999年   4011篇
  1998年   2400篇
  1997年   2529篇
  1996年   1859篇
  1995年   1699篇
  1994年   1532篇
  1993年   1062篇
  1992年   1458篇
  1991年   1285篇
  1990年   1162篇
  1989年   1056篇
  1988年   917篇
  1987年   819篇
  1986年   730篇
  1985年   578篇
  1984年   484篇
  1983年   385篇
  1982年   325篇
  1981年   302篇
  1980年   237篇
  1979年   268篇
  1978年   229篇
  1977年   238篇
  1976年   219篇
  1974年   192篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
991.
992.
We investigated potential sources of infection for 6 confirmed influenza A (H5N1) patients who resided in urban areas of People's Republic of China. None had known exposure to sick poultry or poultry that died from illness, but all had visited wet poultry markets before illness.  相似文献   
993.
Large magnetic field-induced strains can be achieved in modulated martensite for Ni-Mn-In alloys; however, the metastability of the modulated martensite imposes serious constraints on the ability of these alloys to serve as promising sensor and actuator materials. The phase stability, magnetic properties, and electronic structure of the modulated martensite in the Ni2Mn1.5In0.5 alloy are systematically investigated. Results show that the 6M and 5M martensites are metastable and will eventually transform to the NM martensite with the lowest total energy in the Ni2Mn1.5In0.5 alloy. The physical properties of the incommensurate 7M modulated martensite (7M–IC) and nanotwinned 7M martensite (7M(52¯)2) are also calculated. The austenite (A) and 7M(52¯)2 phases are ferromagnetic (FM), whereas the 5M, 6M, and NM martensites are ferrimagnetic (FIM), and the FM coexists with the FIM state in the 7M–IC martensite. The calculated electronic structure demonstrates that the splitting of Jahn–Teller effect and the strong Ni–Mn bonding interaction lead to the enhancement of structural stability.  相似文献   
994.
水环境中粪便污染的微生物溯源技术及研究进展   总被引:1,自引:0,他引:1  
人畜粪便是造成水体病原菌污染的主要因素之一,快速、正确地判别水体污染的来源对保障饮用水及环境水体安全尤为重要。近年来,利用微生物进行水体病原菌污染的溯源分析已成为国际上的研究热点。该文简要介绍微生物溯源技术的基本原理,着重阐述了该技术的方法学,并进一步提出了微生物溯源技术与应用结合的未来研究方向,以期为同领域专家学者提供参考,促进微生物溯源技术在我国的应用。  相似文献   
995.
996.
The increase in solar ultraviolet radiation (UVR) that reaches the Earth’s surface should make us reflect on the need to develop new approaches in protecting the skin from UVR exposure. The present study aims to evaluate the photoprotective and antiaging efficacy of a red orange extract (100 mg/day) in both Asian and Caucasian subjects. A randomized, double-blind, controlled study was carried out in 110 Asian and Caucasian subjects. Product efficacy was measured as follows: (1) the photoprotective effect was measured by the minimal erythema dose (MED) assessment; (2) the efficacy in decreasing the UVA+B-induced skin redness was measured by colorimetry; (3) the antioxidant efficacy was measured by the ferric-reducing antioxidant power (FRAP) and the malondialdehyde (MDA) assay; and (4) skin moisturization, skin elasticity, skin radiance, the intensity of melanin staining, transepidermal water loss (TEWL), and wrinkles were measured to assess the antiaging efficacy. The intake of the product for 56 days was effective in improving the skin reaction to UV exposure; in increasing the skin antioxidant capacity as well as in decreasing UVA-induced lipid peroxidation; in increasing the skin moisturization, skin elasticity, and skin radiance; and in decreasing TEWL, the intensity of melanin staining inside dark spots, and wrinkle depth. Our results suggest that the test product is effective in counteracting both the harmful effects of UVR exposure and aging signs.  相似文献   
997.
This paper analyses the characteristics of the mechanical behavior of a trussed steel and concrete box beam under bending conditions based on the structural stressing state theory and the numerical shape function method. Firstly, the parametric generalized strain energy density was introduced to characterize the structural stressing state of trussed steel stud concrete box girders, and the strain energy density sum was plotted. Then the Mann-Kendall criterion was used to discriminate the leap point of the curve change and to redefine the structural failure load. By analyzing the strain and displacement, the existence of a sudden change in the structural response during the load-bearing process was again demonstrated. Afterwards, the numerical shape function method was used to extend the strain data, and further in-depth analyses of strain/stress fields and internal forces were carried out to show in detail the working characteristics of each under load. Through an in-depth analysis from different angles, the rationality of updating the failure load was verified. Finally, the effects of different structure parameters on the evolution of the structural stresses of the members were analyzed in a transversal comparison. The analysis results of the stress state of a steel-concrete truss structure reveal the working behavior characteristics of a steel-concrete truss structure from a new angle, which provides a reference for the design of a steel-concrete truss structure in the future.  相似文献   
998.
To determine the relationship of coxsackievirus A16 (CA16) to prototype CA16-G10, we conducted a phylogenetic analysis of circulating CA16 strains in China. Complex recombinant forms of CA16-related viruses involving multiple human enteroviruses, subgroup A (CA4, CA16, and enterovirus 71), are prevalent among patients with hand, foot, and mouth disease.  相似文献   
999.
Precise evaluation for flexural ultimate capacity of bridges which are subjected to the collision of over-height trucks is essential for making decisions on corresponding maintenance, strengthening or replacement. When the span of a cross-line continuous bridge with a double-box girder was hit by an overly high vehicle, the concrete floor of one girder was severely damaged, and part of the prestressed strands and reinforcements in the girder were broken. After the double-box girder was removed and separated into two single box girders, the ultimate flexural capacity of both box girders was studied by destructive tests, and a comparison was made between the damaged and undamaged girders. Moreover, finite element analysis was conducted to simulate the failure process. The results show that the flexural bearing capacity of the damaged box girder decreased by 33%, but it was still 1.07 times greater than the design bearing capacity, which basically meets the design requirements. Also, the damaged box girder showed a desirable serviceable limit state for three-axle vehicles and five-axle vehicles, but showed an undesirable serviceable limit state for six-axle vehicles. This study shows that repairing or strengthening the damaged span may be better than demolishing and rebuilding the whole superstructure bridge.  相似文献   
1000.
湖州市食品中单增李斯特菌的污染状况调查   总被引:1,自引:1,他引:1  
目的:了解湖州市食品中单增李斯特菌的污染状况。方法:按国标方法,采用进口显色培养基,对食品进行单增李斯特菌的分离、生化鉴定。结果:281份样品中共检出22株,污染率为7.83%。其中冷冻/藏鸡肉中污染率最高,为25.00%。结论:湖州市食品中单增李斯特菌的污染比较严重,应加强对生肉制品等的监督管理,以防食源性疾病的发生。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号