全文获取类型
收费全文 | 368篇 |
免费 | 15篇 |
国内免费 | 2篇 |
专业分类
385篇 |
出版年
2022年 | 4篇 |
2021年 | 2篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 13篇 |
2014年 | 19篇 |
2013年 | 17篇 |
2012年 | 33篇 |
2011年 | 24篇 |
2010年 | 21篇 |
2009年 | 19篇 |
2008年 | 25篇 |
2007年 | 21篇 |
2006年 | 37篇 |
2005年 | 15篇 |
2004年 | 15篇 |
2003年 | 15篇 |
2002年 | 15篇 |
2001年 | 11篇 |
2000年 | 15篇 |
1999年 | 7篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有385条查询结果,搜索用时 15 毫秒
81.
A procedure for the regeneration of fertile transgenic Chinese cabbage (Brassica campestris ssp. pekinensis cv. Spring Flavor) is presented in this report. The protocol is based on infection of cotyledon explants of 5-d-old seedlings with an Agrobacterium tumefaciens strain LBA4404 carrying a disarmed binary vector pTOK/BKS-1. The T-DNA region of this binary vector contains the nopaline synthase/neomycin phosphotransferase II (nptII) chimeric gene for kanamycin resistance and the cauliflower mosaic virus 35S/coat protein gene of tobacco mosaic virus L (TMV-L) chimeric gene. After co-cultivation for 48 h, the cotyledonary petioles were placed on shoot induction media containing 15 mg/L kanamycin sulfate. Shoot induction was continued for 3–4 weeks, then subcultured once and after 2 weeks the shoots were transferred to root induction medium. After 1 week 8 putatively transformed plantlets from 200 cotyledon explants were obtained and transferred to greenhouse. Six of them grew to maturity, produced normal flowers and set seeds. Polymerase chain reaction and Southern blot hybridization analyses confirmed the introduction of the T-DNA into the Chinese cabbage genome. Further, Western blot analysis using polyclonal TMV antiserum showed most of the regenerants (5 out of 6) expressed TMV coat protein gene. Stable inheritance of the inserted clone was investigated in the next generation. 相似文献
82.
Zusammenfassung In histochemischen Untersuchungen an der Mamma von Ratten soll die Beeinflussung der Enzymaktivität durch Östrogene und Progesteron demonstriert werden. Die Untersuchungen wurden an 40 weiblichen juvenilen und kastrierten Albinoratten durchgeführt, von denen die 1. Gruppe Follikelhormon (Progynon, 5 /d), die 2. Gruppe Corpus luteum-Hormon (Proluton, 1 mg/d) erhielten. Neben Kontrolltieren gleichen Alters wurden die Brustdrüsen unbehandelter infantiler Tiere untersucht. Am 3., 5., 10. und 20. Tag nach Injektionsbeginn wurden die Tiere getötet und die Brustdrüsen histologisch sowie enzymhistochemisch durch den Nachweis von alkalischer Phosphatase (Azofarbstoff und Schwermetallsimultanmethode), Glukose-6-Phosphatase, Adenosintriphosphatase, 5-Nukleotidase, Glukose-6-Phosphat-Dehydrogenase, Succinodehydrogenase und Laktatdehydrogenase aufgearbeitet.Es wurde festgestellt, daß unter dem Einfluß der Behandlung mit Geschlechtshormonen ein Anstieg der Enzymaktivität einsetzt, wobei Östrogen eine dominierende Bedeutung hat. Diese zeigt sich vor allem in den ersten 5 Tagen, während danach eine gewisse Gleichförmigkeit in der Intensität dieser Reaktion eintritt. Die Ergebnisse lassen sich dem Wandel der Zellstruktur unter gleichartigen hormonalen Einflüssen zuordnen und sind damit Ausdruck hormonal induzierter Stoffwechselleistungen.
Herrn Prof. Dr. Karl-Heinz Bässler, Physiolog.-chem. Institut der Universität Mainz, sei für sachkundige Beratung in biochemischen Fragen vielmals gedankt. 相似文献
Histochemical enzymepattern of the mammary gland during the experimental influence of sex hormones
Summary The influence of estrogene und progesterone on the activity of enzymes is to be demonstrated by histochemical examinations of the mammary gland of rats. The examinations were made with 40 female juvenile and castrated albino rats of which the 1st group was given follicle-hormone (progynon, 5 /d), the 2nd group corpus-luteum-hormone (proluton, 1 mg/d). Besides control animals of the same age the mammary glands of untreated infantile animals were examined. On the 3rd, 5th, 10th, and 20th day after the beginning of the injections the animals were killed and the mammary glands were treated histologically as well as enzymehistochemically by examining their reaction to alcaline phosphatase, glucose-6-phosphatase, adenosine triphosphatase, 5-nucleotidase, glucose-6-phosphatase-dehydrogenase, succinic dehydrogenase, and lactic dehydrogenase.We found that under the influence of sex hormones the activity of enzymes increased and that estrogene had a dominating importance. This importance could be demonstrated during the first five days, while later these reactions showed a certain balance in their intensity. The results correspond to the change of the cellstructure under similar hormonal influences and thus are results of hormonally induced changes of metabolism.
Herrn Prof. Dr. Karl-Heinz Bässler, Physiolog.-chem. Institut der Universität Mainz, sei für sachkundige Beratung in biochemischen Fragen vielmals gedankt. 相似文献
83.
The effects of 1-naphthaleneacetic acid and N6-benzyladenine on the growth of Cymbidium forrestii rhizomes in vitro 总被引:2,自引:0,他引:2
An Asiatic orchid, Cymbidium forrestii, was clonally propagated using seed-derived rhizomes as explants. The rhizomes were cultured and proliferated on Murashige and Skoog medium supplemented with various growth substances. Auxins stimulated rhizome growth by increasing branching and fresh weight of the explant, with 1-naphthaleneacetic acid (NAA) being the most effective auxin. All auxins tested suppressed normal shoot formation. The apical meristem of the rhizome reacted to exogenously applied auxin by reducing the cytoplasmic zone of the apical meristem and causing meristem derivatives to rapidly differentiate into vacuolated parenchyma cells. Leaf formation and development was retarded in the presence of auxin. Cytokinins generally reduced rhizome growth and the number of branches, but benzyladenine (BA) can induce shoot formation in vitro. BA induced the cytoplasmic zone of the apical meristem to enlarge and enhanced leaf development. A 5% (w/v) sucrose concentration was most effective in shoot induction when combined with 5 mg1-1 BA. Activated charcoal promoted rhizome growth; however, shoot formation was inhibited. 相似文献
84.
Kee Yoeup Paek Stephen F. Chandler Trevor A. Thorpe 《Plant Cell, Tissue and Organ Culture》1987,9(2):159-165
Shoot cultures were established from seedling shoot tips of Raphanus sativus var. longipinnatus Bailey cv. Gungjung, (Japanese radish) cultured on a Murashige-Skoog medium supplemented with ca. 4.5–135 M kinetin or N6-benzyladenine. The latter cytokinin supported overall better growth, and 22.2 M was adopted for maintenance of established cultures. The nitrate: ammonium levels in the medium proved optimal for growth and shoot proliferation and both these parameters were significantly increased by addition of adenine sulfate or sodium phosphate. Rooting of excised shoots was achieved on auxin containing medium. Indole-3-butyric acid (ca. 5 or 10 M) also enhanced shoot growth. Plants were easily established in soil, appeared morphologically normal, and flowered. 相似文献
85.
The increasing global demand for biomass of medicinal plant resources reflects the issues and crisis created by diminishing renewable resources and increasing consumer populations. Moreover, diverse usage of plants and reduced land for cultivation in the world accelerated the deficiency of plant resources. In addition, the preparation of safety of plant based medicine whips up demand for biomass of valuable medicinal plants. As one of alternative approach to upswing the productivity of plant-based pharmaceutical compounds, automation of adventitious root culture system in air-lift bioreactor was adopted to produce cosmic amount of root biomass along with enriched diverse bioactive molecules. In this review, various physiological, engineering parameters, and selection of proper cultivation strategy (fed-batch, two-stage etc.) affecting the biomass production and secondary metabolite accumulation have been discussed. In addition, advances in adventitious root cultures including factors for process scale-up as well as recent research aimed at maximizing automation of the bioreactor production processes are also highlighted. Examples of the scale-up of cultures of adventitious roots of Morinda citrifolia, Echinacea purpurea and angustifolia, Hypericum perforatum and Panax ginseng by applying 20L to 10,000L bioreactors in our lab were demonstrated with a view of commercial application. 相似文献
86.
Post-translational modifications (PTMs) play key roles in the regulation of biological functions of proteins. Although some progress has been made in identifying several PTMs using existing approaches involving a combination of affinity-based enrichment and mass spectrometric analysis, comprehensive identification of PTMs remains a challenging problem in proteomics because of the dynamic complexities of PTMs in vivo and their low abundance. We describe here a strategy for rapid, efficient, and comprehensive identification of PTMs occurring in biological processes in vivo. It involves a selectively excluded mass screening analysis (SEMSA) of unmodified peptides during liquid chromatography-electrospray ionization-quadrupole-time-of-flight tandem mass spectrometry (LC-ESI-q-TOF MS/MS) through replicated runs of a purified protein on two-dimensional gel. A precursor ion list of unmodified peptides with high mass intensities was obtained during the initial run followed by exclusion of these unmodified peptides in subsequent runs. The exclusion list can grow as long as replicate runs are iteratively performed. This enables the identifications of modified peptides with precursor ions of low intensities by MS/MS sequencing. Application of this approach in combination with the PTM search algorithm MODi to GAPDH protein in vivo modified by oxidative stress provides information on multiple protein modifications (19 types of modification on 42 sites) with >92% peptide coverage and the additional potential for finding novel modifications, such as transformation of Cys to Ser. On the basis of the information of precursor ion m/z, quantitative analysis of PTM was performed for identifying molecular changes in heterogeneous protein populations. Our results show that PTMs in mammalian systems in vivo are more complicated and heterogeneous than previously reported. We believe that this strategy has significant potential because it permits systematic characterization of multiple PTMs in functional proteomics. 相似文献
87.
CONSTITUTIVE PHOTOMORPHOGENIC 1 promotes seed germination by destabilizing RGA-LIKE 2 in Arabidopsis
Byoung-Doo Lee Yehyun Yim Esther Caibano Suk-Hwan Kim Marta García-Len Vicente Rubio Sandra Fonseca Nam-Chon Paek 《Plant physiology》2022,189(3):1662
Under favorable moisture, temperature, and light conditions, gibberellin (GA) biosynthesis is induced and triggers seed germination. A major mechanism by which GA promotes seed germination is by promoting the degradation of the DELLA protein RGA-LIKE 2 (RGL2), a major repressor of germination in Arabidopsis (Arabidopsis thaliana) seeds. Analysis of seed germination phenotypes of constitutive photomorphogenic 1 (cop1) mutants and complemented COP1-OX/cop1-4 lines in response to GA and paclobutrazol (PAC) suggested a positive role for COP1 in seed germination and a relation with GA signaling. cop1-4 mutant seeds showed PAC hypersensitivity, but transformation with a COP1 overexpression construct rendered them PAC insensitive, with a phenotype similar to that of rgl2 mutant (rgl2-SK54) seeds. Furthermore, cop1-4 rgl2-SK54 double mutants showed a PAC-insensitive germination phenotype like that of rgl2-SK54, identifying COP1 as an upstream negative regulator of RGL2. COP1 interacted directly with RGL2, and in vivo this interaction was strongly enhanced by SUPPRESSOR OF PHYA-105 1. COP1 directly ubiquitinated RGL2 to promote its degradation. Moreover, GA stabilized COP1 with consequent RGL2 destabilization. By uncovering this COP1–RGL2 regulatory module, we reveal a mechanism whereby COP1 positively regulates seed germination and controls the expression of germination-promoting genes.A master regulator of photomorphogenesis positively regulates germination in Arabidopsis seeds by directly ubiquitinating and promoting the degradation of a key repressor of seed germination. 相似文献
88.
We have investigated the complex formation between an immobilized monoclonal antibody and antigens that differ in size about 50-fold. As a model system, we used an iodinated progesterone derivative and a progesterone-horseradish peroxidase conjugate as tracer and a monoclonal antibody as binding protein. The antibody was immobilized by four different methods: physical adsorption, chemical binding, and binding via protein G in the absence or presence of a protective protein (gelatin). These investigations have shown that the performance of competitive immunoassays is determined by a combination of factors: (a) the relative size of the analyte and the tracer, (b) the antibody density on the solid matrix, (c) the method of immobilization of the antibody, and (d) the binding constants between antibody-analyte and antibody-tracer. All of these interactions have to be considered in designing an optimal immunoassay. The smaller antigen can form a 3- to 35-fold higher maximal complex density than the larger antigen. Dose-response curves are less affected by the size of the tracer than by the binding constant with the antibody. A large enzyme tracer with a relatively low binding constant can, therefore, provide a more sensitive assay. On the other hand, the increase in complex density achieved with a smaller tracer yields a higher signal that in turn can provide a better signal-to-noise ratio in highly sensitive competitive solid-phase immunoassays. We have suggested a model for antibody immobilization that accounts for the interdependence of tracer size, complex formation, and antibody density. The methods described can be used to design and optimize immunoassays of predefined performance characteristics. The results are particularly useful for converting radioimmunoassays to enzyme immunoassays. 相似文献
89.
Soon Lim Yun-Hee Kim Sun-Hyung Kim Suk-Yoon Kwon Haeng-Soon Lee Jin-Seog Kim Kwang-Yun Cho Kee-Yoeup Paek Sang-Soo Kwak 《Molecular breeding : new strategies in plant improvement》2007,19(3):227-239
Oxidative stress is one of the major factors causing injury to plants exposed to environmental stress. Transgenic sweetpotato
[Ipomoea batatas (L.) Lam. cv. Yulmi] plants with an enhanced tolerance to multiple environmental stresses were developed by expressing the
genes of both CuZn superoxide dismutase (CuZnSOD) and ascorbate peroxidase (APX) under the control of an oxidative stress-inducible
SWPA2 promoter in the chloroplasts of sweetpotato plants (referred to as SSA plants). SSA plants were successfully generated by
the particle bombardment method and confirmed by PCR analysis. When leaf discs of SSA plants were subjected to 5 μM methyl viologen (MV), they showed approximately 45% less damage than non-transformed (NT) plants. When 200 μM MV was sprayed onto the whole plants, SSA plants showed a significant reduction in visible damage compared to leaves of NT
plants, which were almost destroyed. The expression of the introduced CuZnSOD and APX genes in leaves of SSA plants following
MV treatment was significantly induced, thereby reflecting increased levels of SOD and APX in the chloroplasts. APX activity
in chloroplast fractions isolated from SSA plants was approximately 15-fold higher than that in their counterparts from NT
plants. SSA plants treated with a chilling stress consisting of 4°C for 24 h exhibited an attenuated decrease in photosynthetic
activity (Fv/Fm) relative to NT plants; furthermore, after 12 h of recovery following chilling, the Fv/Fm of SSA plants almost
fully recovered to the initial levels, whereas NT plants remained at a lower level of Fv/Fm activity. These results suggest
that SSA plants would be a useful plant crop for commercial cultivation under unfavorable growth conditions. In addition,
the manipulation of the antioxidative mechanism in chloroplasts can be applied to the development of various other transgenic
crops with an increased tolerance to multiple environmental stresses. 相似文献
90.
Min-Wha?Jeon Mohammad ?Babar?Ali Eun-Joo?Hahn Kee-Yoeup?PaekEmail author 《Plant Growth Regulation》2005,45(2):139-147
Micropropagated plantlets are fragile and often lack sufficient vigour to survive the acclimatization shock during transplantation to the soil. Effects of photosynthetic photon flux densities (PPFDs) on growth, photosynthesis and anatomy of micropropagated Doritaenopsis were studied after 4 months of acclimatization in a greenhouse at 25 °C. The plantlets were transferred to three different PPFDs for four months, i.e. low light (175), intermediate light (270) and high light (450 mol m–2 s–1). For most of the growth parameters measured i.e. leaf length, leaf area, leaf width, fresh weight, dry weight, chlorophyll (Chl) a/b ratio, were greater for the intermediate light levels after 4 months of acclimatization. The only exception was leaf thickness, which was increased more under high light levels. Results showed that the survival of Doritaenopsis plantlets was greatest (90%) in low light and intermediate light (89%) compared with only (73%) at high light. However, at low light levels, pigment concentrations (chlorophyll a, b and total chlorophyll) were higher. Net CO2 assimilation (A), stomatal conductance (g) and transpiration (E) were higher in plantlets grown at high level PPFD than at low after 4 months of acclimatization. Photosynthetic efficiency (Fv/Fm) decreased insignificantly; only at mid day for the high light treatment whereas leaf temperature and stomatal closure increased compared to low light. Scanning electron microscopic (SEM) images of leaves from acclimatized plantlets showed an increase in wax formation for the high light grown plantlets compared to those at low light. Microscopic analysis of acclimatized root sections showed highly developed multiseriate-velamen layers and higher root cell activity; while shoots had larger leaf air spaces than those of in vitro grown plantlets. These results suggest that physiological acclimation occurs at the intermediate PPFD (270 mol m–2 s–1) in Doritaenopsis compared to treatment at the high light level. 相似文献