全文获取类型
收费全文 | 12541篇 |
免费 | 1051篇 |
国内免费 | 426篇 |
出版年
2023年 | 102篇 |
2022年 | 281篇 |
2021年 | 459篇 |
2020年 | 301篇 |
2019年 | 326篇 |
2018年 | 385篇 |
2017年 | 310篇 |
2016年 | 454篇 |
2015年 | 715篇 |
2014年 | 782篇 |
2013年 | 918篇 |
2012年 | 1081篇 |
2011年 | 992篇 |
2010年 | 598篇 |
2009年 | 459篇 |
2008年 | 660篇 |
2007年 | 564篇 |
2006年 | 567篇 |
2005年 | 439篇 |
2004年 | 384篇 |
2003年 | 331篇 |
2002年 | 323篇 |
2001年 | 261篇 |
2000年 | 263篇 |
1999年 | 198篇 |
1998年 | 108篇 |
1997年 | 106篇 |
1996年 | 105篇 |
1995年 | 89篇 |
1994年 | 86篇 |
1993年 | 62篇 |
1992年 | 125篇 |
1991年 | 96篇 |
1990年 | 110篇 |
1989年 | 97篇 |
1988年 | 76篇 |
1987年 | 88篇 |
1986年 | 68篇 |
1985年 | 66篇 |
1984年 | 49篇 |
1983年 | 39篇 |
1982年 | 38篇 |
1981年 | 26篇 |
1980年 | 39篇 |
1979年 | 51篇 |
1978年 | 31篇 |
1977年 | 33篇 |
1975年 | 34篇 |
1973年 | 32篇 |
1970年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Background
Meiotic prophase is a critical stage in sexual reproduction. Aberrant chromosome recombination during this stage is a leading cause of human miscarriages and birth defects. However, due to the experimental intractability of mammalian gonads, only a very limited number of meiotic genes have been characterized. Here we aim to identify novel meiotic genes important in human reproduction through computational mining of cross-species and cross-sex time-series expression data from budding yeast, mouse postnatal testis, mouse embryonic ovary, and human fetal ovary. 相似文献12.
13.
Hyperthermic treatment at 43 degrees C suppressed the growth of Ehrlich ascites tumor (EAT) cells in vitro. Incubation of EAT cells at 43 degrees C for as little as 1.5 h totally abolished the transplantability of the tumor. At the same time, the rate of cellular glucose uptake, the density of glucose transporter on the cells as well as the extent of thymidine, uridine and leucine incorporation were significantly reduced. 相似文献
14.
15.
16.
17.
18.
Carles Grau Romuald Ginhoux Alejandro Riera Thanh Lam Nguyen Hubert Chauvat Michel Berg Julià L. Amengual Alvaro Pascual-Leone Giulio Ruffini 《PloS one》2014,9(8)
Human sensory and motor systems provide the natural means for the exchange of information between individuals, and, hence, the basis for human civilization. The recent development of brain-computer interfaces (BCI) has provided an important element for the creation of brain-to-brain communication systems, and precise brain stimulation techniques are now available for the realization of non-invasive computer-brain interfaces (CBI). These technologies, BCI and CBI, can be combined to realize the vision of non-invasive, computer-mediated brain-to-brain (B2B) communication between subjects (hyperinteraction). Here we demonstrate the conscious transmission of information between human brains through the intact scalp and without intervention of motor or peripheral sensory systems. Pseudo-random binary streams encoding words were transmitted between the minds of emitter and receiver subjects separated by great distances, representing the realization of the first human brain-to-brain interface. In a series of experiments, we established internet-mediated B2B communication by combining a BCI based on voluntary motor imagery-controlled electroencephalographic (EEG) changes with a CBI inducing the conscious perception of phosphenes (light flashes) through neuronavigated, robotized transcranial magnetic stimulation (TMS), with special care taken to block sensory (tactile, visual or auditory) cues. Our results provide a critical proof-of-principle demonstration for the development of conscious B2B communication technologies. More fully developed, related implementations will open new research venues in cognitive, social and clinical neuroscience and the scientific study of consciousness. We envision that hyperinteraction technologies will eventually have a profound impact on the social structure of our civilization and raise important ethical issues. 相似文献
19.
To overcome the high energy-consuming process of microalgae drying, a two-step lipase catalysis technique for the preparation of biodiesel from microalgae lipid of Chlorella spp. was developed. In the first step, free fatty acids (FAAs) and triacylglycerols (TAGs) are released after cell disruption and extracted, while the TAGs were hydrolysed by free lipase in aqueous phase. In the second step, FAAs were esterified with ethanol in the catalysis of free suspended lipase. The maximum rate of hydrolysis and esterification was 93.6% and 91.3%, respectively. The effects of reaction parameters, such as reaction time, enzyme amount, water content and molar ratio of lipid to ethanol on hydrolysis or esterification, were investigated. The results indicated that two-step reaction process (hydrolyse esterify) for biodiesel production were feasible. 相似文献
20.