全文获取类型
收费全文 | 3875篇 |
免费 | 117篇 |
国内免费 | 169篇 |
专业分类
4161篇 |
出版年
2024年 | 4篇 |
2023年 | 59篇 |
2022年 | 76篇 |
2021年 | 76篇 |
2020年 | 71篇 |
2019年 | 81篇 |
2018年 | 49篇 |
2017年 | 47篇 |
2016年 | 58篇 |
2015年 | 89篇 |
2014年 | 209篇 |
2013年 | 258篇 |
2012年 | 195篇 |
2011年 | 156篇 |
2010年 | 122篇 |
2009年 | 155篇 |
2008年 | 189篇 |
2007年 | 152篇 |
2006年 | 163篇 |
2005年 | 141篇 |
2004年 | 146篇 |
2003年 | 140篇 |
2002年 | 136篇 |
2001年 | 99篇 |
2000年 | 87篇 |
1999年 | 73篇 |
1998年 | 101篇 |
1997年 | 77篇 |
1996年 | 86篇 |
1995年 | 98篇 |
1994年 | 98篇 |
1993年 | 79篇 |
1992年 | 59篇 |
1991年 | 71篇 |
1990年 | 72篇 |
1989年 | 43篇 |
1988年 | 44篇 |
1987年 | 43篇 |
1986年 | 23篇 |
1985年 | 49篇 |
1984年 | 41篇 |
1983年 | 28篇 |
1982年 | 41篇 |
1981年 | 21篇 |
1980年 | 19篇 |
1979年 | 13篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 2篇 |
排序方式: 共有4161条查询结果,搜索用时 0 毫秒
131.
获取全长cDNA若干方法的比较 总被引:2,自引:0,他引:2
生物技术突飞猛进大大提高了人类认识自身及与人类息息相关的生命现象的能力。近几年内 ,人类 [1,2 ]、模式生物拟南芥 ( Arabidopsis thaliana) [3 5]及水稻的基因组测序 [6,7]的草图相继完成 ,给人类又提出了新的挑战 :如何鉴定这些序列的功能及如何解析生命现象的基因本质 ,这是一个更加庞大而又极富挑战性的课题 ,正促使一门新的学科即功能基因组学 ( Functional genomics)的产生与蓬勃发展。不论功能基因组学多么深奥 ,其认识基因功能的基本前提是获取可能有相关功能的基因之全长编码序列。其中 ,全长 c DNA序列的获取是正确地注释基… 相似文献
132.
133.
There have been few studies on the detection of direct nitric oxide (NO) production and interferon-gamma (IFN-gamma) in vivo without using animal cell culture. We questioned whether NO and IFN-gamma could be produced at the site of infection. The peritoneal cavity of mice was used as the local infection model. NO and IFN-gamma in abdominal washings from these mice were measured directly at various times after injection of Fusobacterium nucleatum, a gram-negative rod periodontal pathogen. The mice were divided into three groups: those treated with live bacteria (LB), those treated with heat-killed bacteria (HKB) and those untreated: normal (N). These mice were compared on the basis of cell filtration, NO and IFN-gamma production by injection of live bacteria (LFn) or heat-killed bacteria (HKFn). In the LB group, the total cell number increased corresponding to an increase in neutrophils after injection of both LFn and HKFn. A low level of NO was constantly produced in abdominal washings, but a significant amount of NO was synthesized in the LB group only 12 hr to 24 hr after injection of LFn. At the same time iNOS enzyme activity and iNOS mRNA expression were detected. IFN-gamma, which may contribute to enhance NO production, was also secreted at a high level from peritoneal exudate cells (PEC) at 12 hr and 24 hr in the LB group by stimulation of LFn. At 12 hr and 24 hr, iNOS positive cells in the LB group by infection of LFn were identified and shown to contain mostly macrophages. These findings indicate that live bacteria play important roles in NO production by macrophages. It is suggested that NO may contribute to the inflammatory response during F. nucleatum infection in periodontitis. 相似文献
134.
135.
AtLa1 protein initiates IRES‐dependent translation of WUSCHEL mRNA and regulates the stem cell homeostasis of Arabidopsis in response to environmental hazards 下载免费PDF全文
136.
137.
Weidner Stanisław Każarnowicz Marta Frączek Ewa Amarowicz Ryszard Karamać Magdalena 《Acta Physiologiae Plantarum》2006,28(6):627-634
Some posttranslational processes that occur in embryos of germinating triticale caryopses treated with different concentrations
of abscisic acid (ABA) were examined. ABA increased the ratio of cytoskeleton-bound polysomes in the total population of polysomes
and depressed the share of free and membrane-bound polysomes. Using exogenous RNase, stability of the total polysomal population
as well as each polysomal fraction was investigated. The total extractable polysomes isolated from embryonic tissues of germinating
triticale caryopses treated with ABA were more stable than the polysomes isolated from the control sample caryopses. The contribution
of the polysomes that were not digested by RNase was increased by higher concentrations of ABA applied during germination.
At high concentrations of ABA (50, 100 μM), the quantitative contribution of polysomes in the total ribosomal fraction was
almost 100% of the amount of polysomes before digestion and the modifications observed consisted mainly of the shift of the
so-called heavy polysomes towards light polysomes, containing a few ribosomes. Within each polysomal population, cytoskeleton-bound
polysomes (CBP and CMBP) were the most stable, which may imply that the bonds between polysomes and these protein filaments,
created in all eukaryotic cells increased their stability. It is assumed that mRNAs are stabilised or destabilised by interaction
of proteins with their various sequences. A plant hormone may depress or elevate the quantities of these proteins, thus regulating
the stability of different mRNAs. The results confirm the multi-faceted mechanism of ABA-induced response, where one of the
constituents is the effect of ABA on the stability of mRNAs molecules. The co-ordinated regulation of mRNAs synthesis and
their stability provide plants with improved adaptability. 相似文献
138.
Rudolf Werner Todd Miller Roobik Azarnia Gerhard Dahl 《The Journal of membrane biology》1985,87(3):253-268
Summary mRNA from estrogen-stimulated rat myometrium, a tissue known to upregulate cell-cell channels in response to this hormone, was microinjected intoXenopus laevis oocytes. The oocytes had been freed from covering layers of follicle cells and vitelline to allow direct cell membrane interactions when paired. About 4 hours after the mRNA injection, paired oocytes become electrically coupled. This coupling was due to the presence of typical cell-cell channels characterized by size-limited intercellular tracer flux, the presence of gap junctions at the oocyte-oocyte interface, and the reversible uncoupling that occurred in the presence of carbon dioxide. The induction of new cell-cell channels in the oocyte membrane was observed against a zero background or a low level of endogenous coupling, depending on the maturation stage of the oocytes. The time course of development of cell-cell coupling after the microinjection of mRNA was determined. The mRNA capable of inducing cell-cell coupling was confined to an intermediate size class when fractionated on a sucrose gradient. 相似文献
139.
We present a novel method using flow cytometry–fluorescence in situ hybridization (flow–FISH) to detect specific messenger RNA (mRNA) in suspended cells using locked nucleic acid (LNA)-modified oligonucleotide probes. β-Actin mRNA was targeted in whole A549 epithelial cells by hybridization with a biotinylated, LNA-modified probe. The LNA bound to β-actin was then stained using phycoerythrin-conjugated streptavidin and detected by flow cytometry. Shifts in fluorescence signal intensity between the β-actin LNA probe and a biotinylated, nonspecific control LNA were used to determine optimal conditions for this type of flow–FISH. Multiple conditions for permeabilization and hybridization were tested, and it was found that conditions using 3 μg/ml of proteinase K for permeabilization and 90 min hybridization at 60 °C with buffer containing 50% formamide allow cells containing the LNA-bound mRNA to be detected and differentiated from the control LNA with high confidence (< 14% overlap between curves). This combined method, called LNA flow–FISH, can be used for detection and quantification of other RNA species as well as for telomerase measurement and detection. 相似文献
140.