全文获取类型
收费全文 | 1812篇 |
免费 | 154篇 |
出版年
2023年 | 14篇 |
2022年 | 7篇 |
2021年 | 16篇 |
2020年 | 17篇 |
2019年 | 8篇 |
2018年 | 53篇 |
2017年 | 41篇 |
2016年 | 72篇 |
2015年 | 101篇 |
2014年 | 124篇 |
2013年 | 173篇 |
2012年 | 146篇 |
2011年 | 131篇 |
2010年 | 76篇 |
2009年 | 58篇 |
2008年 | 95篇 |
2007年 | 73篇 |
2006年 | 73篇 |
2005年 | 74篇 |
2004年 | 64篇 |
2003年 | 56篇 |
2002年 | 55篇 |
2001年 | 38篇 |
2000年 | 57篇 |
1999年 | 25篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 16篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 13篇 |
1991年 | 8篇 |
1989年 | 10篇 |
1988年 | 12篇 |
1985年 | 11篇 |
1984年 | 13篇 |
1982年 | 12篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1973年 | 11篇 |
1971年 | 7篇 |
1969年 | 7篇 |
1966年 | 9篇 |
1965年 | 6篇 |
1963年 | 6篇 |
1960年 | 8篇 |
1958年 | 13篇 |
1957年 | 8篇 |
1956年 | 9篇 |
排序方式: 共有1966条查询结果,搜索用时 15 毫秒
1.
Antoni Pastor Magí Farré Montserrat Fitó Fernando Fernandez-Aranda Rafael de la Torre 《Journal of lipid research》2014,55(5):966-977
The analysis of peripheral endocannabinoids (ECs) is a good biomarker of the EC system. Their concentrations, from clinical studies, strongly depend on sample collection and time processing conditions taking place in clinical and laboratory settings. The analysis of 2-monoacylglycerols (MGs) (i.e., 2-arachidonoylglycerol or 2-oleoylglycerol) is a particularly challenging issue because of their ex vivo formation and chemical isomerization that occur after blood sample collection. We provide evidence that their ex vivo formation can be minimized by adding Orlistat, an enzymatic lipase inhibitor, to plasma. Taking into consideration the low cost of Orlistat, we recommend its addition to plasma collecting tubes while maintaining sample cold chain until storage. We have validated a method for the determination of the EC profile of a range of MGs and N-acylethanolamides in plasma that preserves the original isomer ratio of MGs. Nevertheless, the chemical isomerization of 2-MGs can only be avoided by an immediate processing and analysis of samples due to their instability during conservation. We believe that this new methodology can aid in the harmonization of the measurement of ECs and related compounds in clinical samples. 相似文献
2.
3.
Potential natural vegetation and pre‐anthropic pollen records on the Azores Islands in a Macaronesian context 下载免费PDF全文
This paper discusses the concept of potential natural vegetation (PNV) in the light of the pollen records available to date for the Macaronesian biogeographical region, with emphasis on the Azores Islands. The classical debate on the convenience or not of the PNV concept has been recently revived in the Canary Islands, where pollen records of pre‐anthropic vegetation seemed to strongly disagree with the existing PNV reconstructions. Contrastingly, more recent PNV model outputs from the Azores Islands show outstanding parallelisms with pre‐anthropic pollen records, at least in qualitative terms. We suggest the development of more detailed quantitative studies to compare these methodologies as an opportunity for improving the performance of both. PNV modelling may benefit by incorporating empirical data on past vegetation useful for calibration and validation purposes, whereas palynology may improve past reconstructions by minimizing interpretative biases linked to differential pollen production, dispersal and preservation. 相似文献
4.
The largest survey on the perception of synthetic biology-related disciplines (Porcar et al., 2019,EMBO Rep 20) recently revealed that the Spanish society does not have a very positive perception of the term synthetic biology. On the other hand, the terms biotechnology and even genetic engineering received relatively higher scores. The issue of nomenclature and perception is a classical one in science perception studies. Synthetic biologists have been debating their neologism (Synthetic Biology, from now on SB) for years. Even in a 2006 blog, Rob Carlson discussed the various labels for the new field, such as intentional biology, constructive biology, natural engineering, synthetic genomics and biological engineering. This diversity of names, along with the above mentioned negative public perception of the term synthetic biology, raises the question on whether the term itself is suitable or whether it could, in an extreme scenario, be replaced by another combining scientific consensus with public acceptance. 相似文献
5.
6.
Jan Kvíčala Václav Zamrazil Jarmila Čeřovská Jiří Bednář Jaroslav Janda 《Biological trace element research》1995,47(1-3):365-375
Blood serum selenium of 65 men and hair selenium of 77 men from three regions of the Czech Republic (CR) were analyzed by neutron activation analysis, and 202 samples of urine from the same populations were analyzed for Se by the fluorimetric method to assess selenium status of these regions. Low status (53 μg Se/L of serum and 0.29 μg Se/g lyophilized hair as means) and very low urine selenium (8.7 μg/L urine) were detected. By these data, the CR is among the countries with the lowest Se intake. A comparison of studied regions is presented. Moreover, values of serum zinc were within the reference range, but mild to moderate deficiency in the supply of iodine was detected. 相似文献
7.
Yveta Lhotáková Luká? Plí?til Alena Morávková Pavel Kubát Kamil Lang Jitka Forstová Ji?í Mosinger 《PloS one》2012,7(11)
Novel biomaterials based on hydrophilic polycaprolactone and polyurethane (Tecophilic®) nanofibers with an encapsulated 5,10,5,20-tetraphenylporphyrin photosensitizer were prepared by electrospinning. The doped nanofiber textiles efficiently photo-generate O2(1Δg), which oxidize external chemical and biological substrates/targets. Strong photo-virucidal effects toward non-enveloped polyomaviruses and enveloped baculoviruses were observed on the surface of these textiles. The photo-virucidal effect was confirmed by a decrease in virus infectivity. In contrast, no virucidal effect was detected in the absence of light and/or the encapsulated photosensitizer. 相似文献
8.
9.
10.
Hannibal T. Musarurwa Lerí Koegelenberg Nokwanda P. Makunga 《Journal of Plant Growth Regulation》2012,31(2):207-220
The effects of nitrogen, potassium, water stress, and phytohormones were studied using a Salvia stenophylla (Burch. ex Benth.) microplant system. In vitro regeneration was monitored and then followed with volatile secondary metabolite profiling
through headspace solid-phase microextraction gas chromatography. Plantlet growth was most prolific on half-strength Murashige
and Skoog medium without phytohormones. An increase in macronutrients supplied to the microplants enhanced accumulation of
the commercially important (−)-α-bisabolol, while no significant changes to the relative abundance of β-bisabolene, α-muurolene,
α-patchoulene, and D-limonene (among others) became apparent. Water-stressed plants, treated with sorbitol and polyethylene
glycol, had a lowered rooting capacity in vitro. Overall, as a plant production system, micropropagation did not have deleterious
effects on the biochemistry of S. stenophylla as no significant differences in metabolic profiles existed between conventional garden plants and in vitro propagules, regardless
of phytohormone treatment. We also show that nutrient manipulation can be used efficiently as a strategy for positively altering
secondary metabolism. This will ultimately benefit the domestication of this commercially important medicinal herb. 相似文献