全文获取类型
收费全文 | 108004篇 |
免费 | 8382篇 |
国内免费 | 9024篇 |
专业分类
125410篇 |
出版年
2024年 | 240篇 |
2023年 | 1417篇 |
2022年 | 3260篇 |
2021年 | 5511篇 |
2020年 | 3777篇 |
2019年 | 4679篇 |
2018年 | 4428篇 |
2017年 | 3238篇 |
2016年 | 4591篇 |
2015年 | 6676篇 |
2014年 | 7844篇 |
2013年 | 8296篇 |
2012年 | 9978篇 |
2011年 | 8974篇 |
2010年 | 5545篇 |
2009年 | 4970篇 |
2008年 | 5710篇 |
2007年 | 5130篇 |
2006年 | 4454篇 |
2005年 | 3491篇 |
2004年 | 2968篇 |
2003年 | 2719篇 |
2002年 | 2272篇 |
2001年 | 1866篇 |
2000年 | 1694篇 |
1999年 | 1669篇 |
1998年 | 1035篇 |
1997年 | 1001篇 |
1996年 | 941篇 |
1995年 | 821篇 |
1994年 | 787篇 |
1993年 | 617篇 |
1992年 | 818篇 |
1991年 | 617篇 |
1990年 | 466篇 |
1989年 | 443篇 |
1988年 | 354篇 |
1987年 | 344篇 |
1986年 | 266篇 |
1985年 | 286篇 |
1984年 | 156篇 |
1983年 | 161篇 |
1982年 | 99篇 |
1981年 | 85篇 |
1980年 | 60篇 |
1979年 | 77篇 |
1977年 | 59篇 |
1975年 | 56篇 |
1974年 | 52篇 |
1973年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Circadian rhythms play a crucial role in the health and survival of organisms. However, little is known concerning how intrinsic and extrinsic factors affect animal daily rhythms in the field, especially in nocturnal animals. Here, we investigated the first emergence, mid‐emergence, and return times of Vespertilio sinensis, and also integrated environmental conditions (temperature, humidity, and light intensity) and biotic factors (reproductive status and predation risk) to determine causes of variation in the activity rhythms of the bats. We found that variation in the first emergence time, the mid‐emergence time, and the final return time were distinct. The results demonstrated that the emergence and return times of bats were affected by light intensity, reproductive status, and predation risk in a relatively complex pattern. Light intensity had the greatest contribution to activity rhythms. Moreover, we first investigated the effects of actual predators on the activity rhythms of bats; the results showed that the mid‐emergence time of bats was earlier as predators were hunting, but the final return time was later when predators were present. Finally, our results also highlighted the importance of higher energy demands during the lactation in bats to variation in activity rhythms. These results improve our understanding of the patterns and causes of variation in activity rhythms in bats and other nocturnal animals. 相似文献
993.
Yudan Zhao Yongwu Yang Min Liu Xuening Qin Xiran Yu Huimin Zhao Xiaoyun Li Wei Li 《PLoS neglected tropical diseases》2022,16(4)
Giardia duodenalis, the causative agent of giardiasis, is among the most important causes of waterborne diarrheal diseases around the world. Giardia infection may persist over extended periods with intestinal inflammation, although minimal. Cyclooxygenase (COX)-2 is well known as an important inducer of inflammatory response, while the role it played in noninvasive Giardia infection remains elusive. Here we investigated the regulatory function of COX-2 in Giardia-induced pro-inflammatory response and defense-related nitric oxide (NO) generation in macrophage-like cell line, and identified the potential regulators. We initially found that Giardia challenge induced up-regulation of IL-1β, IL-6, TNF-α, prostaglandin (PG) E2, and COX-2 in macrophages, and pretreatment of the cells with COX-2 inhibitor NS398 reduced expressions of those pro-inflammatory factors. It was also observed that COX-2 inhibition could attenuate the up-regulated NO release and inducible NO synthase (iNOS) expression induced by Giardia. We further confirmed that Giardia-induced COX-2 up-regulation was mediated by the phosphorylation of p38 and ERK1/2 MAPKs and NF-κB. In addition, inhibition of reactive oxygen species (ROS) by NAC was shown to repress Giardia-induced activation of MAPK/NF-κB signaling, up-regulation of COX-2 and iNOS, increased levels of PGE2 and NO release, and up-expressions of IL-1β, IL-6, and TNF-α. Collectively, in this study, we revealed a critical role of COX-2 in modulating pro-inflammatory response and defense-related NO production in Giardia-macrophage interactions, and this process was evident to be controlled by ROS-dependent activation of MAPK/NF-κB signaling. The results can deepen our knowledge of anti-Giardia inflammatory response and host defense mechanisms. 相似文献
994.
995.
Kang Wang Shuling You Hesheng Hu Xiaolu Li Jie Yin Yugen Shi Lei Qi Pingjiang Li Yuepeng Zhao Suhua Yan 《Journal of cellular and molecular medicine》2022,26(10):2959
Sympathetic activation after myocardial infarction (MI) leads to ventricular arrhythmias (VAs), which can result in sudden cardiac death (SCD). The toll‐like receptor 4 (TLR4)/myeloid differentiation primary response 88 (MyD88)/nuclear factor‐kappa B (NF‐kB) axis within the hypothalamic paraventricular nucleus (PVN), a cardiac‐neural sympathetic nerve centre, plays an important role in causing VAs. An MI rat model and a PVN‐TLR4 knockdown model were constructed. The levels of protein were detected by Western blotting and immunofluorescence, and localizations were visualized by multiple immunofluorescence staining. Central and peripheral sympathetic activation was visualized by immunohistochemistry for c‐fos protein, renal sympathetic nerve activity (RSNA) measurement, heart rate variability (HRV) analysis and norepinephrine (NE) level detection in serum and myocardial tissue measured by ELISA. The arrhythmia scores were measured by programmed electrical stimulation (PES), and cardiac function was detected by the pressure–volume loop (P‐V loop). The levels of TLR4 and MyD88 and the nuclear translocation of NF‐kB within the PVN were increased after MI, while sympathetic activation and arrhythmia scores were increased and cardiac function was decreased. However, inhibition of TLR4 significantly reversed these conditions. PVN‐mediated sympathetic activation via the TLR4/MyD88/NF‐kB axis ultimately leads to the development of VAs after MI. 相似文献
996.
Soomin Lee Zheng Li Dehua Meng Qinming Fei Libo Jiang Tengfei Fu Ze Wang Shuhao Liu Jian Zhang 《Acta biochimica et biophysica Sinica》2021,(11):1516-1526
Vascularization is an important early indicator of osteogenesis involving biomaterials.Bone repair and new bone formation are associated with extensive neovascu... 相似文献
997.
目的:探讨苓桂术甘汤联合电针风池供血穴治疗椎基底动脉供血不足(VBI)性眩晕的临床疗效.方法:选择2017年11月-2019年8月我院收治的VBI性眩晕患者145例为研究对象,采用随机数字表法分成联合组(75例)和对照组(70例).在基础治疗的前提下,联合组采用苓桂术甘汤联合电针风池供血穴治疗,对照组采用西比灵治疗.比... 相似文献
998.
Xiang Liu Jun Tao Yueyi Yao Ping Yang Juhui Wang Mali YU Jianhong Hou Ying Zhang Li Gui 《Acta biochimica et biophysica Sinica》2021,(11):1495-1504
Resveratrol (RSV) could promote osteogenic activity,but its clinical application has been hampered in view of its poor bioavailability.Therefore,it is desirable... 相似文献
999.
1000.
Mu Yang Shujin Li Wenjing Liu Xiao Li Yunqi He Yeming Yang Kuanxiang Sun Lin Zhang Wanli Tian Lixin Duan Huafu Chen Dezhong Yao Zhenglin Yang Xianjun Zhu 《中国科学:生命科学英文版》2021,(11):1868-1883
The endoplasmic reticulum (ER) membrane protein complex (EMC) regulates the synthesis and quality control of membrane proteins with multiple transmembrane domai... 相似文献