全文获取类型
收费全文 | 1022篇 |
免费 | 72篇 |
国内免费 | 118篇 |
专业分类
化学 | 996篇 |
晶体学 | 14篇 |
力学 | 17篇 |
综合类 | 34篇 |
数学 | 3篇 |
物理学 | 148篇 |
出版年
2024年 | 5篇 |
2023年 | 21篇 |
2022年 | 69篇 |
2021年 | 46篇 |
2020年 | 47篇 |
2019年 | 31篇 |
2018年 | 31篇 |
2017年 | 41篇 |
2016年 | 45篇 |
2015年 | 41篇 |
2014年 | 33篇 |
2013年 | 54篇 |
2012年 | 56篇 |
2011年 | 64篇 |
2010年 | 49篇 |
2009年 | 36篇 |
2008年 | 51篇 |
2007年 | 50篇 |
2006年 | 52篇 |
2005年 | 59篇 |
2004年 | 41篇 |
2003年 | 32篇 |
2002年 | 65篇 |
2001年 | 38篇 |
2000年 | 20篇 |
1999年 | 22篇 |
1998年 | 19篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有1212条查询结果,搜索用时 31 毫秒
1.
Sergio Ayala‐Mar Javier Donoso‐Quezada Roberto C. Gallo‐Villanueva Victor H. Perez‐Gonzalez Jos Gonzlez‐Valdez 《Electrophoresis》2019,40(23-24):3036-3049
Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome‐based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed. 相似文献
2.
Maria Benedetta Fadda Nicoletta Curreli Raffaello Pompei Antonio Rescigno Augusto Rinaldi Enrico Sanjust 《Applied biochemistry and biotechnology》1994,44(3):263-270
A highly active thermostable β-glucosidase was purified to homogeneity from a strain ofTrichoderma sp. The enzyme was an extracellular glycoprotein and showed hydrolytic activity toward several β-glucosides.
Cellobiose was found to be the substrate of choice for this enzyme. This finding could suggest future technological applications
of the purified protein. 相似文献
3.
根据Taura综合征病毒(TSV)基因组,设计特异性引物,从感染病毒组织中提取组织总RNA后扩增,分别将3个主要结构蛋白基因VP1、VP2和VP3克隆到pGEM TEasyVector.与表达载体连接后,导入大肠杆菌中诱导表达,并纯化目的蛋白.诱导表达的融合蛋白分子量分别为54.2×103、43×103和57.1×103,在变性条件下过柱纯化VP1和VP2,一次可以纯化10mg以上纯度较高的蛋白. 相似文献
4.
Shiyue Fang 《Tetrahedron letters》2004,45(43):7987-7990
A reversible biotinylation phosphoramidite was synthesized and incorporated onto the 5′-end of an oligoribonucleotide on a solid phase synthesizer. After cleavage and deprotection, the crude synthetic oligomer mixture was incubated with NeutrAvidin® coated microspheres, and the failure sequences removed by washing with a buffer followed by treating the microspheres with tetrabutylammonium fluoride to give a high quality unmodified full-length oligoribonucleotide. 相似文献
5.
采用浮床黑麦草(Lolium multi florum)对畜禽养殖富营养水体氨氮的净化效应及动态过程进行了研究.结果表明:浮床黑麦草对富营养水体中的氨氮具有明显的净化效果.当覆盖率30%时,对氨氮的去除率最高可达到95.89%.对其去除水体氨氮的动态过程拟合表明符合三次方程曲线.该研究为冬季陆生植物修复富营养水体提供重要依据. 相似文献
6.
The ability to recover and purify natural and recombinant proteins, and the costs of doing so remain a major task in introducing
the potential products of biotechnology. The bases for separation range from specific binding onto tailored reagents to solubility
and partitioning behavior governed by a mixed bag of size, charge, and hydrophobicity. In most cases, a combination of methods
is used in sequence, and improvements in the selectivity at an early stage can enhance the effectiveness of subsequent (and
usually more costly) steps. Genetic engineering provides a means of improving the selectivity within the context of existing
separation methods.
By this strategy, improvements in selectivity are sought by bestowing a distinctive property on the protein of interest. The
primary sequence of amino acids is altered, such that the protein can be selectively removed from other components of the
multicomponent mixture in which such products are commonly found. In this article, the range of these “distinctive properties”
and their pairing with various separation methods will be reviewed. Specific examples from our work, in which a distinctive
charge is provided via a polypeptide “purification” fusion tail, will be discussed. Separation methods we have used with these
fusion proteins are precipitation, two-phase aqueous extraction, reversed micellar extraction, and ion exchange using both
resins and membranes. 相似文献
7.
Shiyao Li Chuntian Wu Huiwen Cheng Hengqiang Li Beilu Li 《Reaction Kinetics and Catalysis Letters》1998,65(2):293-300
The high-temperature durability of cordierite honeycomb Rh-free three-way catalysts (TWC) containing additives has been studied
by calcining catalysts at various temperatures in the interval of 600≈1100°C. The three-way performances of these catalysts
were evaluated for the reaction of carbon monoxide(CO), hydrocarbon(HC) and nitrogen oxides(NOx) at given conditions by using
a fixed bed reactor. The results show that after Rh-free TWC are thermally aged in air at 1100°C for 5h and 950°C for 104
h, the TWC still have better three-way activity compared with Rh-containing TWC. 相似文献
8.
采用一步种子溶胀聚合法制备了颗粒呈单分散的交联聚甲基丙烯酸环氧丙南树脂,对其环氧基的组成比进行了表征,并以氨基葡萄糖为配基,首次制备了纯化粗品伴刀豆球蛋白-A(Ⅲ)(Con-A,Ⅲ)的聚合物基质的高效亲合色谱柱。配基在树脂上的键合量为8.2mg/g,对纯化后的Con-A(Ⅲ)的吸附量为13.4mg/g。使用该亲合色谱介质成功地从粗品Con-A中快速纯化了Con-A,电泳分析显示为一个主要的谱带,纯度从15%提高到95%。 相似文献
9.
Protein tyrosine nitration is a post-translational modification that occurs under conditions of oxidative stress and may play a role in the pathogenesis of diseases such as asthma. Through their ability to generate reactive oxygen species in macrophages and epithelial cells, particulate pollutants, such as diesel exhaust particles (DEPs), may lead to a worsening of the asthmatic condition. In this study, we looked for evidence of oxidative modification of proteins in RAW 264.7 cell line treated with DEP chemicals. We show that the induction of oxidative stress is accompanied by 53 newly expressed proteins which are suppressed by a thiol antioxidant, N-acetylcysteine. These include antioxidant enzymes, pro-inflammatory components, and products of intermediary metabolism. In addition, inducible nitric oxide synthase (iNOS) was identified as a biologically relevant oxidative stress protein that is induced concurrent with increased NO production and protein tyrosine-nitration in DEP-exposed RAW 264.7 cells. Utilizing two-dimensional gel electrophoresis, anti-nitrotyrosine immunoblotting, and mass spectrometry led to the identification of an additional ten nitrotyrosine modified proteins, including oxidative stress proteins involved in intermediary metabolism (e.g., GAPDH and enolase), antioxidant defense (e.g., MnSOD) and inhibition of proteosomal activity (e.g., Hsp 90alpha). These oxidative proteins may serve as markers for oxidative stress generation in vivo. 相似文献
10.
A polyaluminum chloride (PAC) sample was prepared using a slow alkaline titration method. The Bio-Gel P-100 gel column chromatographic
technique was used to separate and characterize the various forms of aluminum present in the prepared PAC solution. The effluents
from a gel column were monitored using online chemical method: Al-Ferron timed complexation spectrophotometry and by 27Al nuclear magnetic resonance (NMR) spectroscopy. Effects of different experimental conditions such as eluent flow rate, ionic
strength and pH on separation of Al13 were investigated. Experimental results indicated that molecule size exclusion was not the only parameter affecting the column
chromatographic separation efficiency of Al13 but molecule charge as well. Reducing the eluent flow rate, increasing the ionic strength and suitable pH resulted in increase
in the separation efficiency. Experimental results clearly indicated that by varying the experimental conditions, it is possible
to produce pure Al13 species using a gel column chromatographic technique. 相似文献