全文获取类型
收费全文 | 6359篇 |
免费 | 533篇 |
国内免费 | 5篇 |
出版年
2023年 | 25篇 |
2022年 | 17篇 |
2021年 | 101篇 |
2020年 | 73篇 |
2019年 | 82篇 |
2018年 | 103篇 |
2017年 | 126篇 |
2016年 | 162篇 |
2015年 | 281篇 |
2014年 | 389篇 |
2013年 | 433篇 |
2012年 | 555篇 |
2011年 | 487篇 |
2010年 | 322篇 |
2009年 | 286篇 |
2008年 | 337篇 |
2007年 | 371篇 |
2006年 | 350篇 |
2005年 | 331篇 |
2004年 | 302篇 |
2003年 | 298篇 |
2002年 | 289篇 |
2001年 | 65篇 |
2000年 | 58篇 |
1999年 | 62篇 |
1998年 | 77篇 |
1997年 | 56篇 |
1996年 | 55篇 |
1995年 | 45篇 |
1994年 | 56篇 |
1993年 | 47篇 |
1992年 | 72篇 |
1991年 | 44篇 |
1990年 | 45篇 |
1989年 | 42篇 |
1988年 | 28篇 |
1987年 | 35篇 |
1986年 | 18篇 |
1985年 | 27篇 |
1984年 | 40篇 |
1983年 | 33篇 |
1982年 | 29篇 |
1981年 | 33篇 |
1980年 | 17篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1976年 | 17篇 |
1975年 | 15篇 |
1974年 | 23篇 |
1972年 | 18篇 |
排序方式: 共有6897条查询结果,搜索用时 171 毫秒
981.
982.
Thomas Arn Hansen Helena Fridholm Tobias Guldberg Fr?slev Kristín Rós Kjartansdóttir Eske Willerslev Lars Peter Nielsen Anders Johannes Hansen 《PloS one》2015,10(11)
Rattus norvegicus (R. norvegicus) are ubiquitous and their presence has several effects on the human populations in our urban areas on a global scale. Both historically and presently, this close interaction has facilitated the dissemination of many pathogens to humans, making screening for potentially zoonotic and emerging viruses in rats highly relevant. We have investigated faecal samples from R. norvegicus collected from urban areas using a protocol based on metagenomic enrichment of circular DNA genomes and subsequent sequencing. We found a new type of papillomavirus, with a L1 region 82% identical to that of the known R. norvegicus Papillomavirus 2. Additionally, we found 20 different circular replication associated protein (Rep)-encoding single stranded DNA (CRESS-DNA) virus-like genomes, one of which has homology to the replication-associated gene of Beak and feather disease virus. Papillomaviruses are a group of viruses known for their carcinogenic potential, and although they are known to infect several different vertebrates, they are mainly studied and characterised in humans. CRESS-DNA viruses are found in many different environments and tissue types. Both papillomaviruses and CRESS-DNA viruses are known to have pathogenic potential and screening for novel and known viruses in R. norvegicus could help identify viruses with pathogenic potential. 相似文献
983.
984.
985.
Teresa Sadras Mickaël Martin Kohei Kume Mark E. Robinson Supraja Saravanakumar Gal Lenz Zhengshan Chen Joo Y. Song Tanya Siddiqi Laura Oksa Anne Marie Knapp Jevon Cutler Kadriye Nehir Cosgun Lars Klemm Veronika Ecker Janet Winchester Dana Ghergus Pauline Soulas-Sprauel Markus Müschen 《Molecular cell》2021,81(10):2094-2111.e9
986.
Kristina Wallenius Tobias Kroon Therese Hagstedt Lars Löfgren Maria Sörhede-Winzell Jeremie Boucher Daniel Lindén Nicholas D. Oakes 《Journal of lipid research》2022,63(3):100176
Sodium-glucose cotransporter 2 (SGLT2) inhibitors have been shown to increase ketone bodies in patients with type 2 diabetes; however, the underlying mechanisms have not been fully elucidated. Here we examined the effect of the SGLT2 inhibitor dapagliflozin (1 mg/kg/day, formulated in a water, PEG400, ethanol, propylene glycol solution, 4 weeks) on lipid metabolism in obese Zucker rats. Fasting FFA metabolism was assessed in the anesthetized state using a [9,10-3H(N)]-palmitic acid tracer by estimating rates of plasma FFA appearance (Ra), whole-body FFA oxidation (Rox), and nonoxidative disposal (Rst). In the liver, clearance (Kβ-ox) and flux (Rβ-ox) of FFA into β-oxidation were estimated using [9,10-3H]-(R)-bromopalmitate/[U-14C]palmitate tracers. As expected, dapagliflozin induced glycosuria and a robust antidiabetic effect; treatment reduced fasting plasma glucose and insulin, lowered glycated hemoglobin, and increased pancreatic insulin content compared with vehicle controls. Dapagliflozin also increased plasma FFA, Ra, Rox, and Rst with enhanced channeling toward oxidation versus storage. In the liver, there was also enhanced channeling of FFA to β-oxidation, with increased Kβ-ox, Rβ-ox and tissue acetyl-CoA, compared with controls. Finally, dapagliflozin increased hepatic HMG-CoA and plasma β-hydroxybutyrate, consistent with a specific enhancement of ketogenesis. Since ketogenesis has not been directly measured, we cannot exclude an additional contribution of impaired ketone body clearance to the ketosis. In conclusion, this study provides evidence that the dapagliflozin-induced increase in plasma ketone bodies is driven by the combined action of FFA mobilization from adipose tissue and diversion of hepatic FFA toward β-oxidation. 相似文献
987.
Evaluation of methods for extraction of bacteria from soil 总被引:8,自引:0,他引:8
Abstract Several methods for dispersion of soil were tested for possible use in procedures for extraction of bacteria. Physical cell damage on cells and efficiency in extraction of indigenous cells from soil, were investigated. Cell damage by the dispersion methods was investigated by measuring the physical cell integrity and viability of pure cultures of Escherichia coli and Bacillus subtilis , as well as soil bacteria extracted from soil, when dispersed in slurries of γ-sterilized soil. Separation of bacteria and soil particles on the basis of buoyant density was conducted with the nonionic density gradient medium Nycodenz. When slurries of γ-sterilized soil with added pure cultured cells were centrifuged (10000 × g ) over cushions of Nycodenz (1.3 g ml−1 ), practically all the added cells were recovered in a layer on top of the cushion. This proves that a reversible attachment and cosedimentation is not an important phenomenon in this procedure. The efficiency of the different dispersion methods for the extraction of indigenous soil bacteria, was assessed after separation of dislodged and attached soil bacteria. This separation was done either on the basis of sedimentation rate by low speed centrifugation, or buoyant density by Nycodenz density gradient centrifugation. The physical dispersion by ultrasonic treatment and chemical dispersion by the use of a chelating agent together with a detergent, were inferior to physical dispersion either by Waring blender (for large volumes) or a rotating rubber pestle treatment (for smaller volumes). The physical dispersion did not appear to be destructive to the cells tested. 相似文献
988.
These experiments were conducted to help elucidate the mechanism for the impaired fetal development occurring during maternal hypothyroidism. The disposition of glucose was measured using glucose-1-14C. Maternal hypothyroidism depressed glucose utilization in thematernal-fetal system. Maternal net glycogen synthesis from the labeled glucose was impaired. However, while the fetal glycogen storage system may be capable of at least relatively normal glycogen synthesis, abnormally low levels of glycogen were measured. If, as the data suggest, enzymatic deficiencies do not exist, the low liver glycogen might be a result of the inability of the maternal-placental system to provide adequate substrate to the fetus. 相似文献
989.
The expression of the genes for two types of myrosinase (EC 3.2.3.1), designated MA and MB, during embryo and seedling development was investigated in Sinapis alba L. by in-situ and RNA slot-blot analyses. The expression of MA and MB genes followed similar temporal profiles during embryogenesis, but MB mRNA was present in considerably higher amounts than MA mRNA. In the embryo, both MA and MB genes are activated in cotyledons and axis. The MB genes are preferentially expressed in the cotyledons whereas MA genes are preferentially expressed in the axis. In the developing seedling, MA mRNA was not present in the organs investigated. By contrast, MB mRNA was found in appreciable amounts in hypocotyls, cotyledons and developing leaves. The MB genes seem to be activated preferentially in tissues undergoing rapid cell division and — or cell expansion.Abbreviations DAP
days after pollination
- MA, MB
A type, B type myrosinases in Sinapis alba
Anna-Stina Höglund (Uppsala Genetic Center) is gratefully acknowledged for valuable discussion, Anders Gobl (Department of Immunology, Uppsala University) for kindly advice with the labeling of probes and Qingzhu Zhai (Department of Pharmaceutical Biosciences, Uppsala University) for help with seed harvest. This work was supported by grants from the Swedish Research Council for Forestry and Agriculture. 相似文献
990.
Mertz Christoffer Krarup Sara Jensen Cecilie D. Lindholm Sandy E. H. Kjær Christina Pinborg Lars H. Bak Lasse K. 《Neurochemical research》2020,45(6):1247-1255
Neurochemical Research - Epilepsy is one of the most common chronic neurological conditions. Today, close to 30 different medications to prevent epileptic seizures are in use; yet, far from all... 相似文献