全文获取类型
收费全文 | 6867篇 |
免费 | 620篇 |
国内免费 | 69篇 |
专业分类
7556篇 |
出版年
2024年 | 9篇 |
2023年 | 58篇 |
2022年 | 99篇 |
2021年 | 195篇 |
2020年 | 129篇 |
2019年 | 180篇 |
2018年 | 190篇 |
2017年 | 201篇 |
2016年 | 241篇 |
2015年 | 414篇 |
2014年 | 402篇 |
2013年 | 521篇 |
2012年 | 608篇 |
2011年 | 555篇 |
2010年 | 399篇 |
2009年 | 350篇 |
2008年 | 419篇 |
2007年 | 361篇 |
2006年 | 326篇 |
2005年 | 279篇 |
2004年 | 299篇 |
2003年 | 217篇 |
2002年 | 228篇 |
2001年 | 69篇 |
2000年 | 45篇 |
1999年 | 51篇 |
1998年 | 48篇 |
1997年 | 45篇 |
1996年 | 37篇 |
1995年 | 37篇 |
1994年 | 34篇 |
1993年 | 40篇 |
1992年 | 30篇 |
1991年 | 30篇 |
1990年 | 36篇 |
1989年 | 32篇 |
1988年 | 19篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 27篇 |
1984年 | 29篇 |
1983年 | 18篇 |
1982年 | 25篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 12篇 |
排序方式: 共有7556条查询结果,搜索用时 0 毫秒
101.
102.
Joseph Khoory Jessica Estanislau Abdallah Elkhal Asmae Lazaar Mark I. Melhorn Abigail Brodsky Ben Illigens Itaru Hamachi Yasutaka Kurishita Alexander R. Ivanov Sergey Shevkoplyas Nathan I. Shapiro Ionita C. Ghiran 《PloS one》2016,11(1)
Acute, inflammatory conditions associated with dysregulated complement activation are characterized by significant increases in blood concentration of reactive oxygen species (ROS) and ATP. The mechanisms by which these molecules arise are not fully understood. In this study, using luminometric- and fluorescence-based methods, we show that ligation of glycophorin A (GPA) on human red blood cells (RBCs) results in a 2.1-fold, NADPH-oxidase-dependent increase in intracellular ROS that, in turn, trigger multiple downstream cascades leading to caspase-3 activation, ATP release, and increased band 3 phosphorylation. Functionally, using 2D microchannels to assess membrane deformability, GPS-ligated RBCs travel 33% slower than control RBCs, and lipid mobility was hindered by 10% using fluorescence recovery after photobleaching (FRAP). These outcomes were preventable by pretreating RBCs with cell-permeable ROS scavenger glutathione monoethyl ester (GSH-ME). Our results obtained in vitro using anti-GPA antibodies were validated using complement-altered RBCs isolated from control and septic patients. Our results suggest that during inflammatory conditions, circulating RBCs significantly contribute to capillary flow dysfunctions, and constitute an important but overlooked source of intravascular ROS and ATP, both critical mediators responsible for endothelial cell activation, microcirculation impairment, platelet activation, as well as long-term dysregulated adaptive and innate immune responses. 相似文献
103.
Social carry‐over effects underpin trans‐seasonally linked structure in a wild bird population 下载免费PDF全文
Spatial structure underpins numerous population processes by determining the environment individuals' experience and which other individuals they encounter. Yet, how the social landscape influences individuals' spatial decisions remains largely unexplored. Wild great tits (Parus major) form freely moving winter flocks, but choose a single location to establish a breeding territory over the spring. We demonstrate that individuals' winter social associations carry‐over into their subsequent spatial decisions, as individuals breed nearer to those they were most associated with during winter. Further, they also form territory boundaries with their closest winter associates, irrespective of breeding distance. These findings were consistent across years, and among all demographic classes, suggesting that such social carry‐over effects may be general. Thus, prior social structure can shape the spatial proximity, and fine‐scale arrangement, of breeding individuals. In this way, social networks can influence a wide range of processes linked to individuals' breeding locations, including other social interactions themselves. 相似文献
104.
Hachem A. Lamti Philippe Gorce Mohamed Moncef Ben Khelifa Adel M. Alimi 《Computer methods in biomechanics and biomedical engineering》2016,19(16):1749-1759
The goal of this study is to investigate the influence of mental fatigue on the event related potential P300 features (maximum pick, minimum amplitude, latency and period) during virtual wheelchair navigation. For this purpose, an experimental environment was set up based on customizable environmental parameters (luminosity, number of obstacles and obstacles velocities). A correlation study between P300 and fatigue ratings was conducted. Finally, the best correlated features supplied three classification algorithms which are MLP (Multi Layer Perceptron), Linear Discriminate Analysis and Support Vector Machine. The results showed that the maximum feature over visual and temporal regions as well as period feature over frontal, fronto-central and visual regions were correlated with mental fatigue levels. In the other hand, minimum amplitude and latency features didn’t show any correlation. Among classification techniques, MLP showed the best performance although the differences between classification techniques are minimal. Those findings can help us in order to design suitable mental fatigue based wheelchair control. 相似文献
105.
106.
S Ben Khedir D Moalla N Jardak M Mzid Z Sahnoun T Rebai 《Biotechnic & histochemistry》2016,91(7):480-491
We investigated the efficacy of Pistacia lentiscus fruit oil (PLFO) for protecting human skin from damage due to oxidative stress. PLFO contains natural antioxidants including polyphenols, sterols and tocopherols. We compared the antioxidant potential of PLFO with extra virgin olive oil (EVOO). Explants of healthy adult human skin were grown in culture with either PLFO or EVOO before adding hydrogen peroxide (H2O2). We also used cultured skin explants to investigate the effects of PLFO on lipid oxidation and depletion of endogenous antioxidant defense enzymes including glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) one day after 2 h exposure to H2O2. We found that PLFO scavenged radicals and protected skin against oxidative injury. PLFO exhibited greater antioxidant and free radical scavenging activity than EVOO. Skin explants treated with PLFO inhibited H2O2 induced MDA formation by inhibition of lipid oxidation. In addition, the oil inhibited H2O2 induced depletion of antioxidant defense enzymes including GPx, SOD and CAT. We found that treatment with PLFO repaired skin damage owing to its antioxidant properties. 相似文献
107.
Sheila Ommeh Wei Zhang Ali Zohaib Jing Chen Huajun Zhang Ben Hu Xing-Yi Ge Xing-Lou Yang Moses Masika Vincent Obanda Yun Luo Shan Li Cecilia Waruhiu Bei Li Yan Zhu Desterio Ouma Vincent Odendo Lin-Fa Wang Danielle E. Anderson Jacqueline Lichoti Erick Mungube Francis Gakuya Peng Zhou Kisa-Juma Ngeiywa Bing Yan Bernard Agwanda Zheng-Li Shi 《中国病毒学》2019,34(1):115-115
108.
109.
110.