全文获取类型
收费全文 | 2230篇 |
免费 | 197篇 |
出版年
2023年 | 12篇 |
2022年 | 29篇 |
2021年 | 46篇 |
2020年 | 25篇 |
2019年 | 28篇 |
2018年 | 32篇 |
2017年 | 43篇 |
2016年 | 62篇 |
2015年 | 88篇 |
2014年 | 107篇 |
2013年 | 124篇 |
2012年 | 165篇 |
2011年 | 151篇 |
2010年 | 95篇 |
2009年 | 82篇 |
2008年 | 118篇 |
2007年 | 111篇 |
2006年 | 109篇 |
2005年 | 116篇 |
2004年 | 123篇 |
2003年 | 92篇 |
2002年 | 92篇 |
2001年 | 32篇 |
2000年 | 24篇 |
1999年 | 43篇 |
1998年 | 31篇 |
1997年 | 20篇 |
1996年 | 30篇 |
1995年 | 37篇 |
1994年 | 22篇 |
1993年 | 15篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 19篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 20篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1977年 | 12篇 |
1973年 | 11篇 |
1972年 | 11篇 |
1971年 | 10篇 |
1968年 | 9篇 |
1959年 | 8篇 |
排序方式: 共有2427条查询结果,搜索用时 31 毫秒
991.
992.
993.
Lisheng Dai Kevin Chen Brenda Youngren Julia Kulina Acong Yang Zhengyu Guo Jin Li Peng Yu Shuo Gu 《Nucleic acids research》2016,44(21):10454-10466
RNase III enzyme Drosha interacts with DGCR8 to form the Microprocessor, initiating canonical microRNA (miRNA) maturation in the nucleus. Here, we re-evaluated where Drosha functions in cells using Drosha and/or DGCR8 knock out (KO) cells and cleavage reporters. Interestingly, a truncated Drosha mutant located exclusively in the cytoplasm cleaved pri-miRNA effectively in a DGCR8-dependent manner. In addition, we demonstrated that in vitro generated pri-miRNAs when transfected into cells could be processed to mature miRNAs in the cytoplasm. These results indicate the existence of cytoplasmic Drosha (c-Drosha) activity. Although a subset of endogenous pri-miRNAs become enriched in the cytoplasm of Drosha KO cells, it remains unclear whether pri-miRNA processing is the main function of c-Drosha. We identified two novel in-frame Drosha isoforms generated by alternative splicing in both HEK293T and HeLa cells. One isoform loses the putative nuclear localization signal, generating c-Drosha. Further analysis indicated that the c-Drosha isoform is abundant in multiple cell lines, dramatically variable among different human tissues and upregulated in multiple tumors, suggesting that c-Drosha plays a unique role in gene regulation. Our results reveal a new layer of regulation on the miRNA pathway and provide novel insights into the ever-evolving functions of Drosha. 相似文献
994.
Onoriode Coast Alistair J. Murdoch Richard H. Ellis Fiona R. Hay Krishna S.V. Jagadish 《Plant, cell & environment》2016,39(1):26-37
Resilience of rice cropping systems to potential global climate change will partly depend on the temperature tolerance of pollen germination (PG) and tube growth (PTG). Pollen germination of high temperature‐susceptible Oryza glaberrima Steud. (cv. CG14) and Oryza sativa L. ssp. indica (cv. IR64) and high temperature‐tolerant O. sativa ssp. aus (cv. N22), was assessed on a 5.6–45.4 °C temperature gradient system. Mean maximum PG was 85% at 27 °C with 1488 μm PTG at 25 °C. The hypothesis that in each pollen grain, the minimum temperature requirements (Tn) and maximum temperature limits (Tx) for germination operate independently was accepted by comparing multiplicative and subtractive probability models. The maximum temperature limit for PG in 50% of grains (Tx(50)) was the lowest (29.8 °C) in IR64 compared with CG14 (34.3 °C) and N22 (35.6 °C). Standard deviation (sx) of Tx was also low in IR64 (2.3 °C) suggesting that the mechanism of IR64's susceptibility to high temperatures may relate to PG. Optimum germination temperatures and thermal times for 1 mm PTG were not linked to tolerating high temperatures at anthesis. However, the parameters Tx(50) and sx in the germination model define new pragmatic criteria for successful and resilient PG, preferable to the more traditional cardinal (maximum and minimum) temperatures. 相似文献
995.
Meghan J. Skaer Thomason Christopher D. McCort Michael D. Netherland Brenda J. Grewell 《Wetlands Ecology and Management》2018,26(5):751-762
Rivers are vulnerable to biological invasion due to hydrologic connectivity, which facilitates post-entry movement of aquatic plant propagules by water currents. Ecological and watershed factors may influence spatial and temporal dispersal patterns. Field-based data on dispersal could improve risk assessment models and management responses. Ludwigia hexapetala, an invasive emergent macrophyte, provides a case study for understanding dispersal patterns throughout a watershed. The species spreads via hydrochory and is increasingly imposing detrimental ecological and economic impacts within watersheds of the United States and Europe. We investigated morphology of shoot fragments and their dispersal in the Russian River watershed of California, capturing shoot fragments of L. hexapetala during repeated summer surveys at five locations in the river and quantifying their morphological traits that predict establishment success. Highly variable capture counts suggest the importance of pulse disturbance events in local dispersal of L. hexapetala. Unexpectedly, dispersing propagule pressure was nonlinear, with more shoot fragments captured in the middle rather than lower river. Captured fragments in the middle river were twice the length of fragments captured in the lower river and bore 83% more stem nodes, characteristics associated with greater establishment success. Our results support development of spatially targeted management, outreach, and prevention efforts that could lead to decreased propagule pressure in the watershed. 相似文献
996.
Nathaskia Silva Pereira Brenda Rodrigues Ramires Ferreira Emerson Machado de Carvalho Cláudia Roberta Damiani 《Journal of applied phycology》2018,30(4):2347-2358
Schomburgkia crispa Lindley (Orchidaceae) is an epiphytic species found in gallery forests and dry vegetation in the Brazilian Cerrado. It is typically unable to germinate or exhibits low germination because of dependency on mycorrhizal associations. In vitro cultivation techniques have helped circumvent difficulties involved in propagation from seeds. Alternative media and organic biostimulant substances that reduce costs and promote satisfactory in vitro growth are constantly sought. This study evaluated in vitro multiplication and rooting of S. crispa in a modified culture medium containing extract of the microalga Chlorella sorokiniana. We analyzed supplementation of WPM (Woody Plant Medium) with microalgae suspended in NPK medium, or as the supernatant resulting from the centrifugation of a culture in NPK medium. The extracts were added to WPM instead of distilled water. The compounds 6-benzylaminopurine (BAP) and indolebutyric acid (IBA) were used as reference in the in vitro multiplication and rooting of S. crispa, respectively. Both growth regulators were tested at 0, 2.5, and 5.0 mg L?1. During in vitro multiplication of S. crispa, WPM supplemented with 5.0 mg L?1 BAP favored the formation of more sprouts, whereas WPM containing 2.5 mg L?1 IBA supplemented with microalgae extract stimulated in vitro rooting. Schomburgkia crispa explants cultivated in medium supplemented with microalgae suspension or the supernatant of C. sorokiniana showed growth similar to explants cultivated in WPM alone. Therefore, it is possible to use the microalga C. sorokiniana as a supplement and/or alternative to WPM for the in vitro cultivation of S. crispa. 相似文献
997.
Assessment of the interaction between the flux‐signaling metabolite fructose‐1,6‐bisphosphate and the bacterial transcription factors CggR and Cra
下载免费PDF全文
![点击此处可从《Molecular microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
998.
Triethyllead Inhibits γ-Aminobutyric Acid Binding to Uptake Sites in Synaptosomal Membranes 总被引:2,自引:2,他引:0
Triethyllead (TEL), the active metabolite of tetraethyllead, was shown previously to inhibit selectively high-affinity Na+-dependent uptake of gamma-aminobutyric acid (GABA) into cerebrocortical synaptosomes. Such inhibition was not related to the Na+ gradient, Na+,K+-ATPase activity, [Cl-], or energy charge. We report here that TEL inhibits GABA binding to the presynaptic transporter involved in Na+-dependent uptake. Scatchard plot analysis of Na+-dependent [3H]GABA binding to a highly purified synaptic plasma membrane preparation revealed that 25 microM TEL reduced the Bmax by 44%, leaving the KD unchanged. This binding was reversible and predominantly involved membrane uptake sites, as characterized by pharmacological specificity to GABA ligands. Approximately 85% of specific GABA binding was considered membrane uptake site binding, as indicated by sensitivity to nipecotic acid and diaminobutyric acid, with relative insensitivity to muscimol, bicuculline methiodide, baclofen, and beta-alanine. With respect to previous data, these finding suggest that TEL inhibits Na+-sensitive high-affinity GABA uptake by interfering with GABA binding to its presynaptic transporter. 相似文献
999.
1000.