全文获取类型
收费全文 | 64110篇 |
免费 | 4503篇 |
国内免费 | 213篇 |
专业分类
耳鼻咽喉 | 799篇 |
儿科学 | 1410篇 |
妇产科学 | 843篇 |
基础医学 | 8154篇 |
口腔科学 | 954篇 |
临床医学 | 6815篇 |
内科学 | 13873篇 |
皮肤病学 | 789篇 |
神经病学 | 6403篇 |
特种医学 | 2187篇 |
外国民族医学 | 5篇 |
外科学 | 11495篇 |
综合类 | 625篇 |
一般理论 | 47篇 |
预防医学 | 4370篇 |
眼科学 | 1232篇 |
药学 | 4406篇 |
中国医学 | 71篇 |
肿瘤学 | 4348篇 |
出版年
2024年 | 64篇 |
2023年 | 499篇 |
2022年 | 870篇 |
2021年 | 2008篇 |
2020年 | 1211篇 |
2019年 | 1797篇 |
2018年 | 2187篇 |
2017年 | 1533篇 |
2016年 | 1633篇 |
2015年 | 1875篇 |
2014年 | 2703篇 |
2013年 | 3364篇 |
2012年 | 5253篇 |
2011年 | 5449篇 |
2010年 | 2928篇 |
2009年 | 2690篇 |
2008年 | 4384篇 |
2007年 | 4478篇 |
2006年 | 4265篇 |
2005年 | 4068篇 |
2004年 | 3630篇 |
2003年 | 3466篇 |
2002年 | 3090篇 |
2001年 | 421篇 |
2000年 | 315篇 |
1999年 | 389篇 |
1998年 | 615篇 |
1997年 | 481篇 |
1996年 | 379篇 |
1995年 | 326篇 |
1994年 | 288篇 |
1993年 | 269篇 |
1992年 | 199篇 |
1991年 | 159篇 |
1990年 | 128篇 |
1989年 | 110篇 |
1988年 | 114篇 |
1987年 | 96篇 |
1986年 | 90篇 |
1985年 | 81篇 |
1984年 | 118篇 |
1983年 | 97篇 |
1982年 | 108篇 |
1981年 | 99篇 |
1980年 | 112篇 |
1979年 | 46篇 |
1978年 | 47篇 |
1977年 | 45篇 |
1976年 | 33篇 |
1974年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Laura R. Saslow Shannon McCoy Ilmo van der Löwe Brandon Cosley Arbi Vartan Christopher Oveis Dacher Keltner Judith T. Moskowitz Elissa S. Epel 《Psychophysiology》2014,51(3):257-266
What can a speech reveal about someone's state? We tested the idea that greater stress reactivity would relate to lower linguistic cognitive complexity while speaking. In Study 1, we tested whether heart rate and emotional stress reactivity to a stressful discussion would relate to lower linguistic complexity. In Studies 2 and 3, we tested whether a greater cortisol response to a standardized stressful task including a speech (Trier Social Stress Test) would be linked to speaking with less linguistic complexity during the task. We found evidence that measures of stress responsivity (emotional and physiological) and chronic stress are tied to variability in the cognitive complexity of speech. Taken together, these results provide evidence that our individual experiences of stress or “stress signatures”—how our body and mind react to stress both in the moment and over the longer term—are linked to how complex our speech under stress. 相似文献
992.
993.
994.
Raja Azman David F. Lappin Alexandrea MacPherson Marcello Riggio Douglas Robertson Penny Hodge Gordon Ramage Shauna Culshaw Philip M. Preshaw John Taylor Christopher Nile 《Inflammation research》2014,63(12):1001-1012
Objective
IL-17A is implicated in periodontitis pathogenesis. The roles of IL-17B–IL-17F and IL-17A/F are unknown. This study aimed to determine clinical associations between IL-17 family cytokines and periodontitis and to investigate the biological roles of IL-17A and IL-17E using in vitro model systems.Materials and methods
Samples from 97 patients with periodontitis and 77 healthy volunteers were used in the study. Serum, saliva and gingival crevicular fluid (GCF) levels of IL-17 family cytokines were measured by ELISA. Oral keratinocytes were stimulated with a P. gingivalis biofilm, or IL-17A, in the presence and absence of IL-17E and the expression of IL-8 and CXCL5 were investigated by ELISA and real-time-PCR. NF-κB phosphorylation in similar experiments was also measured using a cell-based ELISA.Results
Serum, saliva and GCF IL-17A levels were higher in periodontitis patients and correlated positively with clinical parameters of attachment loss, pocket depth and bleeding on probing. Serum IL-17E levels were lower in periodontitis patients and the serum IL-17A:IL-17E ratio correlated positively with clinical parameters. In vitro, IL-17E inhibited Porphyromonas gingivalis and IL-17A induced expression of chemokines by reducing phosphorylation of the NF-κB p65 subunit.Conclusions
Serum IL-17A:IL-17E may be a marker of disease severity. IL-17E may have opposing roles to IL-17A in periodontitis pathogenesis. IL-17E can negatively regulate IL-17A and periodontal pathogen induced expression of chemokines by oral keratinocytes. 相似文献995.
996.
Khezrian Mina McNeil Christopher J. Myint Phyo K. Murray Alison D. 《International journal of clinical pharmacy》2019,41(1):251-257
International Journal of Clinical Pharmacy - Background Polypharmacy is a growing health concern for older adults and is associated with poorer clinical outcome. Objective This study aim is to... 相似文献
997.
998.
999.
1000.
Christopher P. McKay 《Proceedings of the National Academy of Sciences of the United States of America》2014,111(35):12628-12633
The requirements for life on Earth, its elemental composition, and its environmental limits provide a way to assess the habitability of exoplanets. Temperature is key both because of its influence on liquid water and because it can be directly estimated from orbital and climate models of exoplanetary systems. Life can grow and reproduce at temperatures as low as −15 °C, and as high as 122 °C. Studies of life in extreme deserts show that on a dry world, even a small amount of rain, fog, snow, and even atmospheric humidity can be adequate for photosynthetic production producing a small but detectable microbial community. Life is able to use light at levels less than 10−5 of the solar flux at Earth. UV or ionizing radiation can be tolerated by many microorganisms at very high levels and is unlikely to be life limiting on an exoplanet. Biologically available nitrogen may limit habitability. Levels of O2 over a few percent on an exoplanet would be consistent with the presence of multicellular organisms and high levels of O2 on Earth-like worlds indicate oxygenic photosynthesis. Other factors such as pH and salinity are likely to vary and not limit life over an entire planet or moon.The list of exoplanets is increasing rapidly with a diversity of masses, orbital distances, and star types. The long list motivates us to consider which of these worlds could support life and what type of life could live there. The only approach to answering these questions is based on observations of life on Earth. Compared with astronomical targets, life on Earth is easily studied and our knowledge of it is extensive––but it is not complete. The most important area in which we lack knowledge about life on Earth is its origin. We have no consensus theory for the origin of life nor do we know the timing or location (1). What we do know about life on Earth is what it is made of, and we know its ecological requirements and limits. Thus, it is not surprising that most of the discussions related to life on exoplanets focus on the requirements for life rather than its origin. In this paper we follow this same approach but later return briefly to the question of the origin of life. 相似文献