全文获取类型
收费全文 | 6017篇 |
免费 | 30篇 |
国内免费 | 16篇 |
专业分类
系统科学 | 119篇 |
丛书文集 | 24篇 |
教育与普及 | 6篇 |
理论与方法论 | 60篇 |
现状及发展 | 3242篇 |
研究方法 | 344篇 |
综合类 | 2171篇 |
自然研究 | 97篇 |
出版年
2018年 | 58篇 |
2017年 | 50篇 |
2016年 | 62篇 |
2015年 | 42篇 |
2014年 | 49篇 |
2013年 | 51篇 |
2012年 | 153篇 |
2011年 | 234篇 |
2010年 | 80篇 |
2008年 | 154篇 |
2007年 | 140篇 |
2006年 | 153篇 |
2005年 | 155篇 |
2004年 | 174篇 |
2003年 | 131篇 |
2002年 | 125篇 |
2001年 | 145篇 |
2000年 | 130篇 |
1999年 | 98篇 |
1992年 | 103篇 |
1991年 | 67篇 |
1990年 | 71篇 |
1989年 | 53篇 |
1987年 | 70篇 |
1986年 | 63篇 |
1985年 | 76篇 |
1984年 | 84篇 |
1983年 | 42篇 |
1982年 | 62篇 |
1981年 | 43篇 |
1980年 | 76篇 |
1979年 | 178篇 |
1978年 | 129篇 |
1977年 | 171篇 |
1976年 | 73篇 |
1975年 | 90篇 |
1974年 | 192篇 |
1973年 | 162篇 |
1972年 | 175篇 |
1971年 | 153篇 |
1970年 | 200篇 |
1969年 | 195篇 |
1968年 | 181篇 |
1967年 | 187篇 |
1966年 | 178篇 |
1965年 | 129篇 |
1964年 | 46篇 |
1958年 | 58篇 |
1957年 | 46篇 |
1956年 | 44篇 |
排序方式: 共有6063条查询结果,搜索用时 34 毫秒
71.
Water mites Limnochares aquatica (L., 1758) during maintenance in the laboratory for a long period of time in constant conditions periodically produced certain whitish flocculent material consisting of long rigid unbranched tube-like threads 1.3 ± 0.3 µm in diameter crossing freely. These threads were studied using light-optical as well as transmission electron microscopical and scanning electron microscopical methods. Microbiological staining was also applied to the threads to exclude their bacterial or fungal origin. The thread wall is built of fine fibrils arranged at different angles to the long axis of threads that is reflected in a certain stratification of the wall. Threads are mostly hollow or may contain electron-dense homogeneous material. No cell components are present in the thread composition. Numerous dermal glands with their small slit-like orifice scattered throughout the mite body surface are thought to produce these threads. Most probably the thread formation is a reaction of mites to stress under laboratory conditions, and this is expected to be a type of defensive reaction. 相似文献
72.
73.
74.
近年来,旅游业已经成为很多地区拉动经济增长的重要产业之一。新疆具有浓郁的民族风情以及各种得天独厚的旅游资源,这为旅游业蓬勃发展提供了坚实基础。首先介绍了新疆旅游业的基本发展状况及趋势;其次,针对新疆2005-2017年的统计数据,运用Stata14.0软件对该数据进行多元回归,分析了旅游业对地区经济增长的贡献,并对新疆经济增长与旅游业之间的影响机制进行研究;最后根据实证分析得出的结论,提出了若干对策建议。 相似文献
75.
76.
Systemic Practice and Action Research - This paper explores the usefulness of rich pictures as a method in Systemic Lean Intervention (SLI) process. It combines Lean and Systems Thinking analytical... 相似文献
77.
78.
79.
Pau B. Esparza-Moltó Cristina Nuevo-Tapioles José M. Cuezva 《Cellular and molecular life sciences : CMLS》2017,74(12):2151-2166
The mitochondrial H+-ATP synthase is a primary hub of cellular homeostasis by providing the energy required to sustain cellular activity and regulating the production of signaling molecules that reprogram nuclear activity needed for adaption to changing cues. Herein, we summarize findings regarding the regulation of the activity of the H+-ATP synthase by its physiological inhibitor, the ATPase inhibitory factor 1 (IF1) and their functional role in cellular homeostasis. First, we outline the structure and the main molecular mechanisms that regulate the activity of the enzyme. Next, we describe the molecular biology of IF1 and summarize the regulation of IF1 expression and activity as an inhibitor of the H+-ATP synthase emphasizing the role of IF1 as a main driver of energy rewiring and cellular signaling in cancer. Findings in transgenic mice in vivo indicate that the overexpression of IF1 is sufficient to reprogram energy metabolism to an enhanced glycolysis and activate reactive oxygen species (ROS)-dependent signaling pathways that promote cell survival. These findings are placed in the context of mitohormesis, a program in which a mild mitochondrial stress triggers adaptive cytoprotective mechanisms that improve lifespan. In this regard, we emphasize the role played by the H+-ATP synthase in modulating signaling pathways that activate the mitohormetic response, namely ATP, ROS and target of rapamycin (TOR). Overall, we aim to highlight the relevant role of the H+-ATP synthase and of IF1 in cellular physiology and the need of additional studies to decipher their contributions to aging and age-related diseases. 相似文献
80.
Miguel Bernabé-Rubio Miguel A. Alonso 《Cellular and molecular life sciences : CMLS》2017,74(22):4077-4095
Primary cilia are solitary, microtubule-based protrusions of the cell surface that play fundamental roles as photosensors, mechanosensors and biochemical sensors. Primary cilia dysfunction results in a long list of developmental and degenerative disorders that combine to give rise to a large spectrum of human diseases affecting almost any major body organ. Depending on the cell type, primary ciliogenesis is initiated intracellularly, as in fibroblasts, or at the cell surface, as in renal polarized epithelial cells. In this review, we have focused on the routes of primary ciliogenesis placing particular emphasis on the recently described pathway in renal polarized epithelial cells by which the midbody remnant resulting from a previous cell division event enables the centrosome for initiation of primary cilium assembly. The protein machinery implicated in primary cilium formation in epithelial cells, including the machinery best known for its involvement in establishing cell polarity and polarized membrane trafficking, is also discussed. 相似文献