全文获取类型
收费全文 | 11873篇 |
免费 | 620篇 |
国内免费 | 189篇 |
专业分类
耳鼻咽喉 | 81篇 |
儿科学 | 171篇 |
妇产科学 | 98篇 |
基础医学 | 1402篇 |
口腔科学 | 276篇 |
临床医学 | 2340篇 |
内科学 | 1178篇 |
皮肤病学 | 119篇 |
神经病学 | 553篇 |
特种医学 | 449篇 |
外科学 | 987篇 |
综合类 | 1475篇 |
预防医学 | 1640篇 |
眼科学 | 62篇 |
药学 | 1173篇 |
34篇 | |
中国医学 | 451篇 |
肿瘤学 | 193篇 |
出版年
2024年 | 24篇 |
2023年 | 171篇 |
2022年 | 484篇 |
2021年 | 604篇 |
2020年 | 460篇 |
2019年 | 316篇 |
2018年 | 318篇 |
2017年 | 352篇 |
2016年 | 325篇 |
2015年 | 405篇 |
2014年 | 758篇 |
2013年 | 862篇 |
2012年 | 739篇 |
2011年 | 821篇 |
2010年 | 629篇 |
2009年 | 486篇 |
2008年 | 523篇 |
2007年 | 460篇 |
2006年 | 405篇 |
2005年 | 362篇 |
2004年 | 305篇 |
2003年 | 274篇 |
2002年 | 246篇 |
2001年 | 192篇 |
2000年 | 158篇 |
1999年 | 132篇 |
1998年 | 151篇 |
1997年 | 136篇 |
1996年 | 152篇 |
1995年 | 143篇 |
1994年 | 96篇 |
1993年 | 94篇 |
1992年 | 102篇 |
1991年 | 88篇 |
1990年 | 69篇 |
1989年 | 63篇 |
1988年 | 68篇 |
1987年 | 64篇 |
1986年 | 52篇 |
1985年 | 82篇 |
1984年 | 84篇 |
1983年 | 52篇 |
1982年 | 59篇 |
1981年 | 56篇 |
1980年 | 40篇 |
1979年 | 61篇 |
1978年 | 37篇 |
1977年 | 35篇 |
1976年 | 40篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Abstract: The resolution of several structurally related synthetic peptides, derived from the loop 3 region of the activin βA–βD subunits, has been studied using capillary electrochromatography (CEC) with Hypersil n‐octadecylsilica as the sorbent. The results confirm that the CEC migration of these peptides can be varied in a charge‐state‐specific manner as the properties of the background electrolyte, such as pH, salt concentration and content of organic modifier, or temperature are systematically changed. Acidic peptides followed similar trends in retention behaviour, which was distinctly different to that shown by more basic peptides. The CEC separation of these peptides with the Hypersil n‐octadecyl‐silica involved distinguishable contributions from both electrophoretic mobility and chromatographic retention. Temperature effects were reflected as variations in both the electro‐osmotic flow and the electrophoretic mobility of the peptides. When the separation forces acting on the peptides were synergistic with the electro‐osmotic flow, as, for example, with the positively charged peptides at a particular pH and buffer electrolyte composition, their retention coefficient, κcec, decreased with increasing capillary temperature, whereas when the separation forces worked in opposite directions, as for example with negatively charged peptides, their κcec values increased slightly with increasing temperature. Moreover, when the content of organic modifier, acetonitrile, was sufficiently high, e.g. > 40% (v/v) and nonpolar interactions with the Hypersil n‐octadecyl‐silica sorbent were suppressed, mixtures of both the basic and acidic synthetic peptides could be baseline resolved under isocratic conditions by exploiting the mutual processes of electrophoretic mobility and electrostatic interaction. A linear relationship between the ln κcec values and the volume fractions, ψ, of the organic modifier over a limited range of ψ‐values, was established for the negatively charged peptides under these isocratic conditions. These findings thus provide useful guidelines in a more general context for the resolution and analysis of structurally related synthetic peptides using CEC methods. 相似文献
52.
53.
医学气象学与SARS流行的相关性研究 总被引:2,自引:0,他引:2
目的从医学气象学角度探讨SARS流行与气象因素的相关性。方法以SARS高发区广州、北京为例,通过网络、报刊等媒介获取两地在SARS流行前后的相关气象因子(日最高温度、日最低温度、相对湿度)及SARS疫情报告,运用EXCEL2000及相关矩阵法统计分析气象因子与SARS流行的关系,并从医学气象学角度对其相关性作出探讨。结果①SARS在12.8~23.5℃发病率最高,且与最高温度呈负相关。②SARS发病与最低温度呈负相关,高发前期有明显的降温过程。③广州的相对湿度较北京高,但与SARS的流行相关性不大。④2001年冬平均气温高于往年。结论①相对湿度较大有利于SARS的发生。②SARS发生于温热天气,气温波动有助于其流行。③气候异常变化是SARS发生的诱因。 相似文献
54.
55.
整个血液净化中心机房设备包括血液透析机、整套完整的水处理及相关辅助设备.在机房设计时应根据整套系统的工作原理及使用条件,制定对机房设计、电源配置、管路布局结构等方面的具体要求,并正确实施安装调试. 相似文献
56.
57.
58.
Banglin Xie Runsheng Guo Wen Liang Xiaowei Yang JiaQiang Xu Lijun Wan Wenye Yao Zhi Yi Niya Hu Bin Zhang 《Orthopaedic Surgery》2022,14(8):1703
ObjectiveTo study the epidemiological correlation and drug resistance of external factors of infection caused by open injury of limbs to pathogens.MethodsThis experiment is a retrospective study. We took the geographical location and climate of Nanchang, Jiangxi Province, China as the background, analyzed 2017 strains of pathogens from 1589 patients with limb trauma infection in a University Affiliated Hospital from 2012 to 2017. Patients were divided into three groups according to the type of incision: I, In‐hospital infection of clean limb incision, II, In‐hospital infection with open injury, III, Community infection with open injury of the limb. Groups II and Groups III were divided into six subgroups according to the causes of trauma, including: accidents from non‐motor vehicles, machinery, cutting/piercing, pedestrian injuries, struck by/against, pedal cycles, and other injuries. We found eight common pathogens of orthopedic infection, which were mainly divided into Gram‐positive bacteria (G+, mainly including Staphylococcus) and Gram‐negative bacteria (G‐, mainly Enterobacteriaceae). The relationship between main pathogens and damage mechanism, apparent temperature and relative humidity was discussed in this study. SPSS v22.0 was used for statistical analysis of the data. Friedman''s two‐way ANOVA was used to analyze the difference between the injury mechanism and incidence of pathogenic bacteria. Linear regression was used to determine the trend between the incidence of major pathogens and seasonal temperature and humidity. The level of significance was set as P < 0.05.ResultsThere was no significant difference in the distribution of pathogens between Groups II and Groups III (P>0.05). The drug resistance of Groups III was significantly higher than that of Groups II and Groups I. G+ bacteria were resistant to cephalosporin, ceftriaxone and other cephalosporins and erythromycin and other macrolides. They were sensitive to vancomycin and linezolid. G‐ were resistant to the first‐ and the second‐generation cephalosporins, including cefotetan and cefazolin, and ampicillin and other penicillins, while they were sensitive to third‐generation cephalosporins, such as ceftazidime, as well as to levofloxacin and other quinolones, meropenem, and other beta‐lactamases. The correlation between the injury mechanism and infection of pathogenic bacteria was not significant. The monthly average apparent temperature and relative humidity were correlated with the infection rate of pathogenic bacteria.ConclusionIn open injury of extremities, apparent temperature and relative humidity is an important risk factor for infection by pathogenic bacteria and the drug resistance of pathogenic bacteria in out‐of‐hospital infection was lower than that of hospital infection. 相似文献
59.
Wei Zhang Kaifeng Li Chengdong Zheng Han Sun Jiancun Pan Yuanyuan Li Ying Liu Wenqing Wang Mengnan Ju Yajun Xu Shilong Jiang 《Nutrients》2022,14(10)
The metabolomic profiles of Chinese human milk have been poorly documented. The objective of the study was to explore associations between human milk metabotypes, maternal adiposity, infant growth patterns, and risk of allergies. Two hundred mother–infant dyads from seven cities were randomly selected from the Chinese Human Milk Project (CHMP). Untargeted human milk metabolomic profiles were determined using HPLC-MS/MS. Two human milk metabotypes were identified using principal component analysis. Principal component (PC) 1 was characterized by high linoleic acid metabolites with low purine nucleosides and metabolites of glutamate and glutathione metabolism. PC 2 was characterized by high glycerophospholipids and sphingomyelins content. Higher PC1 scores were associated with slower infant growth rate and higher ambient temperature (p < 0.05). Higher PC 2 scores were related to higher maternal BMI and increased risk of infant allergies (p < 0.05). Future work is needed to understand the biologic mechanisms of these human milk metabotypes. 相似文献
60.
An analytical model was developed to determine the temperature of friction coupling, in which one element was made of a functionally graded material (FGM) and the other was homogeneous. First, for such a system, the boundary–value problem of heat conduction was formulated with consideration of the heat generation due to friction. Then, using the Laplace integral transform, an exact solution to this problem was obtained for uniform sliding, and braking with constant deceleration. A numerical analysis was performed for the selected friction pair consisting of the FGM (zircon dioxide + titanium alloy) and cast iron. It was established that the use of elements made of a FGM consisting of ZrO2 and Ti-6Al-4V can significantly reduce the maximum temperature achieved in the friction system. 相似文献