全文获取类型
收费全文 | 11085篇 |
免费 | 1001篇 |
国内免费 | 1篇 |
专业分类
12087篇 |
出版年
2022年 | 109篇 |
2021年 | 197篇 |
2020年 | 113篇 |
2019年 | 150篇 |
2018年 | 195篇 |
2017年 | 155篇 |
2016年 | 271篇 |
2015年 | 498篇 |
2014年 | 540篇 |
2013年 | 614篇 |
2012年 | 841篇 |
2011年 | 764篇 |
2010年 | 511篇 |
2009年 | 466篇 |
2008年 | 697篇 |
2007年 | 652篇 |
2006年 | 596篇 |
2005年 | 606篇 |
2004年 | 590篇 |
2003年 | 572篇 |
2002年 | 506篇 |
2001年 | 112篇 |
2000年 | 90篇 |
1999年 | 101篇 |
1998年 | 170篇 |
1997年 | 121篇 |
1996年 | 120篇 |
1995年 | 110篇 |
1994年 | 94篇 |
1993年 | 71篇 |
1992年 | 85篇 |
1991年 | 69篇 |
1990年 | 75篇 |
1989年 | 58篇 |
1988年 | 73篇 |
1987年 | 47篇 |
1986年 | 61篇 |
1985年 | 69篇 |
1984年 | 80篇 |
1983年 | 59篇 |
1982年 | 60篇 |
1981年 | 72篇 |
1980年 | 56篇 |
1979年 | 54篇 |
1978年 | 53篇 |
1977年 | 47篇 |
1976年 | 38篇 |
1974年 | 40篇 |
1973年 | 42篇 |
1970年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
51.
Bacterial resistance to antimicrobial agents is a growing problem worldwide. Not only is issue compounded by the fact that there are fewer pharmaceutical companies conducting research to discover novel antimicrobials than in the past but development time lines have stretched so that a dozen years from discovery to the market is now the standard. Eleven antibacterial drugs in late stage clinical development are discussed. Whereas many of these may successfully deal with resistant strains of Gram-positive pathogens, there is very little in development to address the gorwing unmet medical need of multi-drug resistant Gram-negative infections. 相似文献
52.
The identification of angiogenic growth factors, such as vascular endothelial growth factor and fibroblast growth factor, has fueled interest in using such factors to induce therapeutic angiogenesis. The results of numerous animal studies and clinical trials have offered promise for new treatment strategies for various ischemic diseases. Increased understanding of the cellular and molecular biology of vessel growth has, however, prompted investigators and clinicians alike to reconsider the complexity of therapeutic angiogenesis. The realization that formation of a stable vessel is a complex, multistep process may provide useful insights into the design of the next generation of angiogenesis therapy. 相似文献
53.
Focal adhesion regulation of cell behavior 总被引:23,自引:0,他引:23
Focal adhesions lie at the convergence of integrin adhesion, signaling and the actin cytoskeleton. Cells modify focal adhesions in response to changes in the molecular composition, two-dimensional (2D) vs. three-dimensional (3D) structure, and physical forces present in their extracellular matrix environment. We consider here how cells use focal adhesions to regulate signaling complexes and integrin function. Furthermore, we examine how this regulation controls complex cellular behaviors in response to matrices of diverse physical and biochemical properties. One event regulated by the physical structure of the ECM is phosphorylation of focal adhesion kinase (FAK) at Y397, which couples FAK to several signaling pathways that regulate cell proliferation, survival, migration, and invasion. 相似文献
54.
55.
Luis Espinasa Carly Heintz Sylvie Rétaux Masato Yoshisawa François Agnès Patricia Ornelas-Garcia Robert Balogh-Robinson 《Journal of fish biology》2021,98(1):304-316
Animals evolve their sensory systems and foraging behaviours to adapt and colonize new and challenging habitats such as the dark cave environment. Vibration attraction behaviour (VAB) gives fish the ability to locate the source of a water disturbance in the darkness. VAB evolved in the blind Mexican cave tetra, Astyanax mexicanus. VAB is triggered in cavefish by vibration stimuli peaking at 35 Hz, which is within the main spectrum of water fluctuations produced by many prey crustaceans and insects. VAB has a genetic component and is correlated to an increased number of head mechanosensory neuromasts in the eye orbital region when compared to surface fish. Previous competitive prey capture assays have supported the advantage of VAB for foraging in the dark. Despite its putative adaptive function, VAB has been described as absent in some Astyanax cave populations (Tinaja and Molino) but present in others (Pachón, Piedras, Toro and Sabinos). Here we have tested the occurrence of VAB in the field and in multiple cave populations using a vibrating device in natural pools. Our results confirmed the presence of VAB in caves such as Pachón, Toro and Sabinos but showed that VAB is also present in the Tinaja and Molino cave populations, previously reported as VAB-negative in laboratory experiments. Thus, VAB is available throughout the range of hypogean A. mexicanus. However, and most notably, within a given cave the levels of VAB were highly variable among different pools. Fish at one pool may express no VAB, while fish at another nearby pool of the same cave may actively show VAB. While a variety of environmental conditions may foster this diversity, we found that individuals inhabiting pools with a high abundance of organic matter have reduced expression of VAB. In contrast, in pools with little organic debris where fish probably depend more on hunting than on scavenging, VAB is enhanced. Our results suggest that expression of VAB is a plastic trait whose variability can depend on local conditions. Such plasticity may be required within and among caves where high environmental variability between pools results in a diverse availability of food. 相似文献
56.
57.
58.
Travellers' malaria is an exciting topic. It is a field in flux with evolving options for chemoprophylaxis, self-diagnosis, self-treatment, risk/strategy analyses and surveillance. Ideologies vary and experts differ but debate is needed and can bring change. The launch of a new thematic series in the Malaria Journal -- " Travellers' malaria " -- creates an ideal forum to bring together research papers, reviews, opinion papers and commentaries, and will hopefully stimulate debate. 相似文献
59.
60.