全文获取类型
收费全文 | 523篇 |
免费 | 30篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 11篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 12篇 |
2016年 | 18篇 |
2015年 | 26篇 |
2014年 | 30篇 |
2013年 | 35篇 |
2012年 | 40篇 |
2011年 | 33篇 |
2010年 | 20篇 |
2009年 | 24篇 |
2008年 | 35篇 |
2007年 | 35篇 |
2006年 | 34篇 |
2005年 | 25篇 |
2004年 | 33篇 |
2003年 | 35篇 |
2002年 | 28篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 8篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有553条查询结果,搜索用时 109 毫秒
151.
Ti (Tumor inducing) plasmids in Agrobacterium tumefaciens can transfer their T-DNA region into dicotyledonous plants, in which the expression of T-DNA genes causes plant tumors and the production of bacterial nutrients, e.g., opines such as nopaline. Naturally occurring Ti plasmids (pTi) are difficult to cure by conventional curing methods because of their high stability. Here, we developed a novel curing method based on plasmid incompatibility. For this, a curing plasmid, pMGTrep1, was newly constructed and subsequently introduced into A. tumefaciens strains harboring pTi by conjugation with Escherichia coli harboring pMGTrep1. The conjugation yielded 32-99% nopaline non-utilizing agrobacterial transconjugants in which pMGTrep1 replaced pTi due to incompatibility. Then, pMGTrep1-less derivatives of the transconjugants are easily selected in the presence of sucrose because pMGTrep1 contains a sucrose-sensitive sacB gene. This efficient method is directly applicable for curing plasmids with the same incompatibility group and shoud also applicable to other types of plasmids in Agrobacterium groups, including A. rhizogenes, by replacing the rep gene region of the curing plasmid with that of the corresponding incompatibility. 相似文献
152.
Spontaneous muscle action potentials fail to develop without fetal-type acetylcholine receptors 总被引:6,自引:0,他引:6
下载免费PDF全文
![点击此处可从《EMBO reports》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In mammals, two combinations of muscle nicotinic acetylcholine receptors (AChRs) are used: α2βγδ (γ-AChR) or α2βδ (-AChR). After birth, γ-AChRs are replaced by -AChRs (γ/-switch). The two receptors have different conductances and open times. During perinatal period, the long open time γ-AChRs generate random myofiber action potentials from uniquantal miniature end-plate potentials (mEPPs). -AChRs are suitable for strong adult muscle activities. Since the effect of the γ/-switch on neuromuscular development was unclear, despite the many differences in channel characteristics, we carried out this study to generate γ-subunit-deficient mice. Homozygotes born alive survived for 2 days in a stable condition, and were able to move their forelimbs. Endplate AChRs included -subunits, and muscle fibers had multiple neuromuscular junctions. Both pre- and postsynapses were abnormal and spontaneous action potentials generated from mEPPs were totally absent. Results suggest a requirement for γ-AChRs in mediating synaptically-induced action potential activity critical for neuromuscular development. 相似文献
153.
To determine the effects of high temperature on the number of alveolar macrophages (AMs) in bronchoalveolar lavage (BAL) fluid in rats, F344 rats were housed in environment chambers at 23 degrees C, 30 degrees C or 35 degrees C for up to 14 days. The number of AMs in the BAL fluid was significantly decreased in rats housed at 35 degrees C on days 7 and 14, compared to the control group housed at 23 degrees C. The total protein content and lactate dehydrogenase activity did not change at high temperatures in BAL supernatant, indicating that there was no increase in alveolar/capillary barrier permeability or lung cellular injury. The results might suggest that high temperature (35 degrees C) affects the pulmonary defense mechanism. 相似文献
154.
Yoshiro Okano Takeshi Miyata Katsunori Iwasaki Kazuo Takahama Taizo Hitoshi Yoshitoshi Kasé Isamu Matsumoto Toshihiro Shinka 《Analytical biochemistry》1981,115(2):254-259
A specific and sensitive method for analysis of brain pyrrolidine, a volatile amine with potent synaptotropic actions on the peripheral and central nervous systems, was devised. The method involves the isolation of volatile amines by steam distillation and the qualification and quantification of pyrrolidine by gas chromatography/mass spectrometry () including a selected ion monitoring technique with deuterium-labeled pyrrolidine as an internal standard. The lower limit of quantification for the method was 2 pmol, and the mean concentration of pyrrolidine in the rat whole brain was determined to be 95 pmol/g of tissue. 相似文献
155.
Avirulent Avian Influenza Virus as a Vaccine Strain against a Potential Human Pandemic 总被引:8,自引:0,他引:8
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ayato Takada Noritaka Kuboki Katsunori Okazaki Ai Ninomiya Hiroko Tanaka Hiroichi Ozaki Shigeyuki Itamura Hidekazu Nishimura Masayoshi Enami Masato Tashiro Kennedy F. Shortridge Hiroshi Kida 《Journal of virology》1999,73(10):8303-8307
In the influenza H5N1 virus incident in Hong Kong in 1997, viruses that are closely related to H5N1 viruses initially isolated in a severe outbreak of avian influenza in chickens were isolated from humans, signaling the possibility of an incipient pandemic. However, it was not possible to prepare a vaccine against the virus in the conventional embryonated egg system because of the lethality of the virus for chicken embryos and the high level of biosafety therefore required for vaccine production. Alternative approaches, including an avirulent H5N4 virus isolated from a migratory duck as a surrogate virus, H5N1 virus as a reassortant with avian virus H3N1 and an avirulent recombinant H5N1 virus generated by reverse genetics, have been explored. All vaccines were formalin inactivated. Intraperitoneal immunization of mice with each of vaccines elicited the production of hemagglutination-inhibiting and virus-neutralizing antibodies, while intranasal vaccination without adjuvant induced both mucosal and systemic antibody responses that protected the mice from lethal H5N1 virus challenge. Surveillance of birds and animals, particularly aquatic birds, for viruses to provide vaccine strains, especially surrogate viruses, for a future pandemic is stressed. 相似文献
156.
157.
158.
Enomoto H Kohata K Nakayama M Yamaguchi Y Ichimura K 《Journal of plant physiology》2004,161(8):977-980
2-C-methyl-D-erythritol, a soluble carbohydrate that is not ubiquitously found in higher plants, was detected in the ethanol extract from Phlox subulata petals and isolated using HPLC. The isolated compound was identified by 1H-NMR, 13C-NMR and Cl-MS spectra. 2-C-methyl-D-erythritol was a major soluble carbohydrate in petals, leaves and stems. In petals, the concentration of 2-C-methyl-D-erythritol markedly increased during flower development and opening and was similar in concentration to glucose, a ubiquitous metabolic sugar. This suggests that 2-C-methyl-D-erythritol may contribute to flower opening in association with glucose in the P. subulata. 相似文献
159.
Arbuscular mycorrhizal colonization of the dominant plant species in primary successional volcanic deserts on the Southeast slope of Mount Fuji 总被引:3,自引:0,他引:3
Arbuscular mycorrhizal (AM) colonization was observed on four plant species in primary successional volcanic deserts on the Southeast slope of Mount Fuji. The AM colonization of the dominant species, Polygonum cuspidatum, contradicts the conclusion that Polygonaceae are often regarded as being non-mycorrhizal species. The secondary dominant species, Polygonum weyrichii var. alpinum, formed no mycorrhizas. The roots of Cirsium purpuratum, Clematis stans and Campanula punctata ssp. hondoensis, showed a higher percentage of AM colonization than P. cuspidatum. AM colonization and spore density in the rhizosphere soil of P. cuspidatum significantly decreased as elevation increased. AM colonization in roots of Cirsium purpuratum and Clematis stans also tended to decrease with increased altitudes. Cirsium purpuratum and Campanula punctata ssp. hondoensis formed single structural types of Arum- and Paris-type, respectively, whereas P. cuspidatum and Clematis stans formed both Arum- and Paris-type morphologies. 相似文献
160.
Snake venoms contain a number of heterodimeric C-type lectin-like proteins (CLPs) that interact specifically with components of the haemostatic system. EMS16 from the venom of Echis multisquamatus binds to the collagen receptor, integrin alpha2beta1, also known as glycoprotein (GP) Ia/IIa, and specifically inhibits collagen binding. Here we report the crystal structure of EMS16 in complex with recombinant integrin alpha2-I domain that plays a central role in collagen binding. The structure of the complex at 1.9 Angstrom resolution reveals that the collagen-binding site of the alpha2-I domain is covered completely by the bound EMS16. This blockage by EMS16 appears to spatially inhibit collagen binding to the alpha2-I domain. The bound alpha2-I domain adopts a closed conformation, which is seen in the absence of ligand, suggesting that EMS16 stabilizes a closed conformation corresponding to the less active structure of the alpha2-I domain. EMS16 does not directly bind to the manganese ion and residues of the metal ion-dependent adhesion site (MIDAS) of the alpha2-I domain, suggesting that EMS16 may have the potential to bind specifically to the alpha2-I domain in a metal ion-independent fashion. 相似文献