全文获取类型
收费全文 | 419篇 |
免费 | 39篇 |
国内免费 | 1篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 21篇 |
2014年 | 16篇 |
2013年 | 28篇 |
2012年 | 39篇 |
2011年 | 30篇 |
2010年 | 12篇 |
2009年 | 15篇 |
2008年 | 23篇 |
2007年 | 13篇 |
2006年 | 15篇 |
2005年 | 20篇 |
2004年 | 19篇 |
2003年 | 10篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1977年 | 4篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1959年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有459条查询结果,搜索用时 15 毫秒
91.
Functional group substitutions of the branchpoint adenosine in a nuclear pre-mRNA and a group II intron. 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《RNA (New York, N.Y.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Splicing of nuclear mRNA precursors (pre-mRNAs) takes place in the spliceosome, a large and complex ribonucleoprotein. Nuclear pre-mRNA splicing and group II intron self-splicing occur by a chemically identical pathway involving recognition of a specific branchpoint adenosine and nucleophilic activation of its 2'-hydroxyl group. The chemical similarity between these two splicing reactions, as well as other considerations, have suggested that the catalytic core of the spliceosome and group II introns may be related. Here we test this hypothesis by analyzing splicing and RNA branch formation of a pre-mRNA and a group II intron in which the branchpoint adenosine was substituted with purine base analogues. We find that replacement of the branchpoint adenosine with either of two modified adenosine analogues or guanosine leads to remarkably similar patterns of splicing and RNA branch formation in the two systems. 相似文献
92.
The responses of Acacia nilotica L. var. cupriciformis to phosphorus application and inoculation with the indigenous consortium of arbuscular mycorrhizal
(AM) fungi were evaluated in a nursery experiment using soil from a marginal wasteland. A positive growth response to mycorrhizal
inoculation was observed at an Olsen-P level of 20 ppm in the presence of the natural population of AM fungi. There was growth
stimulation by either inoculation or additional P at the highest soil P of 40 ppm. Colonization was negatively correlated
to soil P but P content of both shoot and root were positively correlated. Inoculation with the indigenous AM consortium significantly
increased the uptake of P at all levels of applied P. Acacia is moderately dependent upon the AM symbiosis and exhibited a maximal mycorrhizal dependence (MD) of 18.25% at 20 ppm Olsen-P
level under the conditions studied. A sharp and considerable reduction in MD and dry matter yield observed at 40 ppm P suggests
that the external P requirement for maximal production of biomass was met at approximately 20 ppm Olsen-P.
Accepted: 25 June 1996 相似文献
93.
Arvind?Subramanian Vijayalaxmi?Gupta Sandipto?Sarkar Gargi?Maity Snigdha?BanerjeeEmail author Arnab?Ghosh LaCoiya?Harris Lane?K?Christenson WeiTing?Hung Ajay?Bansal Sushanta?K.?Banerjee
Exosomes, which act as biological cargo vessels, are cell-released, phospholipid-enclosed vesicles. In eukaryotic cells, exosomes carry and exchange biological materials or signals for the benefit or detriment to the cells. Thereby, we consider exosomes to be molecular Palkis (carriers). Although exosomes are currently one of the most popularly researched cellular entities, they have remained largely enigmatic and warrant continued investigation into their structure and functions. These membraned vesicles are between 30 and 150 nm in diameter and are actively secreted by all cell types. While initially considered cellular “trash bags,” recent years have revealed exosomes to be dynamic and multi-functional vesicles that may play a crucial role in cancer development, progression and metastasis. Thereby, they have the potential to be used in development of therapeutic modalities for cancer and other diseases. As more research studies emerge, it’s becoming evident that exosomes are released by cells with a purpose and are representatives of certain cell types and disease conditions. Hence, they may also be used as biomarkers for the detection of cancer initiation, progression and organotropic metastatic growth of cancer cells. This review will focus on the recent developments achieved in identifying the role of exosomes in cancer development and progression as well as therapeutic implications. The review will also discuss the pitfalls of methodologies used for the extraction of exosomes. 相似文献
94.
The isolation of Blastomyces dermatitidis in India is reported from the bronchial aspirate of a female asthmatic patient who had never travelled abroad. The patient was a resident of Rodhain, a small town in the District of Badaun (Uttar Pradesh), situated about 250 km south-east of Delhi. Apart from its demonstration by culture and direct microscopy of a bronchial aspirate, B. dermatitidis was seen microscopically on two occasions in KOH wet mounts and smears of sputum stained with periodic acid-Schiff's reagent. Anti-B. dermatitidis serum precipitins were shown by immunodiffusion in 3 of 4 serum samples from the patient. The identity of the fungus was based on its characteristic morphology in clinical specimens and in culture, conversion of the mold form to the yeast from in vitro and vice versa, and by verification of its pathogenicity in white mice. A detailed clinical and laboratory evaluation of the patient indicated that she had suffered from an episode of self-limited acute pulmonary blastomycosis that required no antifungal therapy. This is believed to be the first authentic report of the isolation of B. dermatitidis from clinical material in India. 相似文献
95.
Several yeasts, fungi and bacteria isolated from the rhizosphere of leguminous crops and soils of rock phosphate deposit area
were found to solubilize low-grade Mussorie rock phosphate. Of the several yeasts and fungi,Schawanniomyces occidentalis, Aspergillus awamori andPenicillium digitatum were better than others in rock phosphate solubilization. Among bacterial isolates from soils of rock phosphate deposits,
Gram-negative motile rods were more effective than Gram-negative non-motile rods in dissolving rock phoshates. The most efficient
bacteria were identified as strains ofPseudomonas striata. All the microorganisms acidified the liquid medium but there was no relationship between the rock phosphate dissolved and
the decrease in pH of the culture broth. 相似文献
96.
Fifty mouse monoclonal antibodies (mAb) specific for HLA class I epitopes were compared for their reactivity against two closely related nonhuman primate species, pigtailed macaques (Macaca nemestrina, Mn) and longtailed macaques (M. fascicularis, Mfl), which diverged from the hominoids 23–40 million years ago. An analysis of Nei's genetic identity (I) and distance (D) based on reactivity of all class I-specific mAb showed, as expected, that the macaques are more closely related to each other (1=0.959) than to man (I=0.782 for Mn and 0.859 for Mfl). However, there were clear differences in genetic similarity with respect to certain epitopes. Macaques were most different from each other and from man in expression of heterologous epitopes recognized by the mouse that are not polymorphic among humans. In contrast, the most polymorphic epitopes unique to single HLA alleles, so-called private epitopes, were present in all the species, and neither macaque species could be distinguished from humans, suggesting that certain class I private epitopes may be highly conserved in evolution.[/p]Abbreviations used in this paper D
Nei's index of genetic distance
- I
Nei's index of genetic identity
- mAb
monoclonal antibodies
- Mfl
Macaca fascicularis
- MHC
major histocompatibility complex
- Mn
Macaca nemestrina
- PF
phenotypic frequency 相似文献
97.
98.
H Quill A Gaur D Brown A J Infante R P Phipps 《Journal of immunology (Baltimore, Md. : 1950)》1989,143(7):2242-2247
Recent reports indicate that murine CD4+ Th1-type cloned T cells are insensitive to IL-1 because specific IL-1R are not detected on these cells and IL-1 does not modulate proliferative responses. However, we have determined that Th1 clones can respond to IL-1, because they function synergistically with IL-2 to induce granulocyte-macrophage-CSF secretion. This response to IL-1 plus IL-2 could be induced by IL-1 alpha or IL-1 beta and by membrane-bound IL-1 on macrophages. However, IL-1R could not be detected, and Th1 cells did not respond to IL-4 in the presence or absence of IL-1, as measured by either proliferation or granulocyte-macrophage-CSF production. Therefore, IL-1 functioned as a cofactor in Th1 cells stimulated with IL-2, but not with IL-4. A possible mechanism whereby IL-1 activates Th1 cells is discussed. 相似文献
99.
100.
Glycan fragmentation forms an integral part of the current research in glycomics. Creation of a database of glycan fragments and their masses for known glycan structures is an important step in the interpretation of mass spectra for the identification of unknown glycan structures. This paper introduces the concept of positional nomenclature, gives a systematic representation of glycan structure of any size, and hence develops a method for theoretically generating all possible first and second generation fragments resulting from glycosidic and cross ring cleavages. Matrix equations are developed for the calculation of theoretical masses. Algorithm is presented for iterative generation of all fragments and calculation of their masses. This method is applicable to glycan analytical techniques using MS, MS/MS, and multistage MS (MSn) with different ionization methods, derivatives, or ions used. The method is adaptable to computer program and has been verified for theoretical masses reported in literature. Rules for the theoretical validation of the fragments are presented. 相似文献