全文获取类型
收费全文 | 4613篇 |
免费 | 361篇 |
国内免费 | 18篇 |
专业分类
耳鼻咽喉 | 21篇 |
儿科学 | 168篇 |
妇产科学 | 137篇 |
基础医学 | 719篇 |
口腔科学 | 40篇 |
临床医学 | 600篇 |
内科学 | 940篇 |
皮肤病学 | 101篇 |
神经病学 | 494篇 |
特种医学 | 81篇 |
外科学 | 418篇 |
综合类 | 18篇 |
一般理论 | 3篇 |
预防医学 | 510篇 |
眼科学 | 111篇 |
药学 | 276篇 |
1篇 | |
中国医学 | 2篇 |
肿瘤学 | 352篇 |
出版年
2023年 | 59篇 |
2022年 | 50篇 |
2021年 | 217篇 |
2020年 | 118篇 |
2019年 | 161篇 |
2018年 | 199篇 |
2017年 | 151篇 |
2016年 | 130篇 |
2015年 | 193篇 |
2014年 | 249篇 |
2013年 | 295篇 |
2012年 | 356篇 |
2011年 | 393篇 |
2010年 | 213篇 |
2009年 | 154篇 |
2008年 | 297篇 |
2007年 | 276篇 |
2006年 | 279篇 |
2005年 | 233篇 |
2004年 | 225篇 |
2003年 | 182篇 |
2002年 | 146篇 |
2001年 | 30篇 |
2000年 | 12篇 |
1999年 | 21篇 |
1998年 | 32篇 |
1997年 | 25篇 |
1996年 | 26篇 |
1995年 | 22篇 |
1994年 | 28篇 |
1993年 | 21篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1980年 | 9篇 |
1975年 | 5篇 |
1974年 | 13篇 |
1973年 | 6篇 |
1971年 | 7篇 |
1970年 | 4篇 |
1968年 | 4篇 |
1964年 | 4篇 |
排序方式: 共有4992条查询结果,搜索用时 15 毫秒
41.
42.
43.
Local environmental signals regulate the growth and development of both normal and malignant breast epithelium. Members of the insulin-like growth factor (IGF) family likely influence both of these processes. The localization of IGF2 to stroma specifically surrounding malignant breast epithelium indicates that this growth factor may play a critical role in the genesis or maintenance of this transformed phenotype. Recent studies have sought to understand the mechanism by which IGF2 expressing fibroblasts are localized to the periphery of malignant breast cancer cells. In addition, the consequences of the expression of IGF-signaling components likely expand beyond their direct effects on mitogenesis. Indirect effects predominantly associated with the IGF2 receptor could also influence the invasive potential of breast tumor cells. 相似文献
44.
45.
Diana Martinez Allegra Broft Richard W Foltin Mark Slifstein Dah-Ren Hwang Yiyun Huang Audrey Perez W Gordon Frankle Thomas Cooper Herbert D Kleber Marian W Fischman Marc Laruelle W Gordon Frankel 《Neuropsychopharmacology》2004,29(6):1190-1202
Striatal dopamine D2 receptors have been implicated in the neurobiology of cocaine addiction. Previous imaging studies showed reduced striatal D2 receptor availability in chronic cocaine abusers, and animal studies suggested that low D2 receptor availability promotes cocaine self-administration. Here, D2 receptor availability was assessed with positron emission tomography (PET) and [11C]raclopride in the limbic, associative, and sensori-motor subdivisions of the striatum in 17 recently detoxified chronic cocaine-dependent (CCD) subjects and 17 matched healthy control (HC) subjects. In addition, the relationship between regional D2 receptor availability and behavioral measures obtained in cocaine self-administration sessions was investigated in CCD subjects. [11C]Raclopride binding potential was significantly reduced by 15.2% in the limbic striatum, 15.0% in the associative striatum, and 17.1% in the sensori-motor striatum in CCD subjects compared to HC subjects. In CCD subjects, no relationship was detected between D2 availability in striatal regions and either the positive effects of smoked cocaine or the choice of cocaine over an alternative reinforcer (money) following a priming dose of cocaine (a laboratory model of relapse). Thus, this study confirms previous reports of a modest decrease in D2 receptor availability in CCD subjects, and establishes that this decrease is generalized throughout the striatum. However, this study failed to demonstrate a relationship between D2 receptor availability and cocaine-induced cocaine-taking behavior. Additional research is warranted to unravel potential neurobiological traits that might confer vulnerability to relapse in detoxified CCD subjects. 相似文献
46.
47.
Audrey Laporte 《Substance use & misuse》2013,48(4):511-531
Meta-analysis is applied to aggregate-level studies that model the demand for cigarettes using static, myopic, or rational addiction frameworks in an attempt to synthesize key findings in the literature and to identify determinants of the variation in reported price elasticity estimates across studies. The results suggest that the rational addiction framework produces statistically similar estimates to the static framework but that studies that use the myopic framework tend to report more elastic price effects. Studies that applied panel data techniques or controlled for cross-border smuggling reported more elastic price elasticity estimates, whereas the use of instrumental variable techniques and time trends or time dummy variables produced less elastic estimates. The finding that myopic models produce different estimates than either of the other two model frameworks underscores that careful attention must be given to time series properties of the data. 相似文献
48.
49.
Eric Parent Marie Archambault Audrey Charlebois Jocelyn Bernier-Lachance 《Avian pathology》2017,46(2):138-149
Necrotic enteritis (NE) is a major problem in antibiotic-free (ABF) chicken flocks and specific strains of Clostridium perfringens are known to induce NE. The objective of this study was to develop a chicken intestinal ligated loop model in order to compare the virulence of various C. perfringens strains recovered from consecutive ABF flocks with and without NE. Intestinal loops were surgically prepared in 10 anaesthetized specific-pathogen-free chickens and alternately inoculated with C. perfringens isolates or brain heart infusion (BHI) media. Histological lesion scoring was performed for each loop. All strains from NE-affected flocks induced histological lesions compatible with NE whereas inoculation of loops with a commensal C. perfringens strain or BHI did not. Among inoculated strains, CP0994 (netB-positive and cpb2-positive) and CP-2003-1256 (netB-positive) demonstrated mean histological lesion scores significantly higher (P?0.01) than those obtained with a commensal strain or BHI whereas strain CP1073 (netB-negative and cpb2-positive) induced intestinal lesions without significantly higher scores. In loops where villi were colonized by Gram-positive rods, significantly higher (P?0.01) mean histological lesion scores were observed. This result supports the hypothesis that colonization of the intestinal mucosa by C. perfringens is a critical step in the pathogenesis of NE. Finally, we demonstrated the importance of controlling virulent C. perfringens strains in ABF chicken flocks as a highly virulent strain can be present in consecutive flocks with NE and possibly affect multiple flocks. 相似文献
50.