全文获取类型
收费全文 | 250篇 |
免费 | 71篇 |
出版年
2023年 | 1篇 |
2021年 | 5篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 7篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 8篇 |
2011年 | 14篇 |
2010年 | 17篇 |
2009年 | 11篇 |
2008年 | 14篇 |
2007年 | 10篇 |
2006年 | 14篇 |
2005年 | 17篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 9篇 |
2001年 | 16篇 |
2000年 | 17篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有321条查询结果,搜索用时 31 毫秒
1.
Short peptide domains target proteins to plant vacuoles. 总被引:18,自引:0,他引:18
2.
3.
REINDERS J. E. A.; AS H. VAN; SCHAAFSMA T. J.; DE JAGER P. A.; SHERIFF D. W. 《Journal of experimental botany》1988,39(9):1199-1210
In this paper we demonstrate the study of plant water balanceby the non-invasive measurement of tissue water content andwater flow using proton nuclear magnetic resonance (NMR). Sapvelocity and flux were measured independently in the presenceof an excess of stationary tissue water. The instrumentationdescribed allows automated and unattended measurement of flow-and water content-variables in a well-defined region of theplant over periods of several days, with a time resolution betweensuccessive measurements of c. 5 s. Using this apparatus theeffect of changes in light intensity (day/night rhythm) andrelative humidity on stem tissue water content as well as onthe velocity and flux of xylem sap in the stem were investigatedin a cucumber plant. The results are in agreement with predictionsfrom a simple model for plant water balance, which is basedon water potential, flow rate and resistance to flow. As longas only transpiration is varied, flow rate and water content(or potential) are affected in opposite ways as demonstratedin this paper. In contrast, the model predicts that changesin uptake (resulting from changes in, for example, root resistance)will induce changes in water content and flow in the same direction.An experimental verification of this prediction is given ina subsequent paper, where, in addition, the NMR results arecompared to those obtained with a dendrometer. Key words: Water balance model, Cucumis sativus L., flow, water content, NMR, water balance measurement 相似文献
4.
Control of follicular epithelium development and vitelline envelope formation in the mosquito; role of juvenile hormone and 20-hydroxyecdysone 总被引:2,自引:0,他引:2
Using microsurgical manipulations, hormone applications, and transmission electron microscopy we have investigated the regulation of differentiation of the follicular epithelium and formation of the vitelline envelope (VE) in primary follicles in the ovary of the mosquito, Aedes aegypti. During the first 3 days after eclosion, the primary follicle grows, and cells of the follicular epithelium differentiate, their content of mitochondria, rough endoplasmic reticulum, and Golgi complexes increases significantly. Growth and differentiation of the follicular epithelium appear to be under the control of juvenile hormone (JH), because they are blocked by removal of corpora allata in newly closed adult females and can be restored by either implantation of corpora allata or application of JH III. In insects, including mosquitoes, VE is the first layer of the eggshell to be deposited. It is formed from the secretory products of the follicle cells and its deposition coincides with yolk accumulation by developing oocytes. Only follicle cells adjacent to the oocyte deposit VE. In decapitated females, given a blood meal by enema and injected with picogram doses of 20-hydroxyecdysone (20-HE), follicle cells synthesize the VE precursors and deposit morphologically normal VE, in contrast to saline injected controls which deposit no VE. We conclude that 20-HE, as well as factors originating from the blood meal and the oocyte, are required for the normal formation of VE in the mosquito follicles. 相似文献
5.
Localization of wheat-germ agglutinin in developing wheat embryos and those cultured in abscisic acid 总被引:1,自引:0,他引:1
The time course of appearance of wheat-germ agglutinin (WGA) in the various embryonic tissues during embryogenesis in Triticum aestivum L. was studied by sensitive immunofluorescence and peroxidase-antiperoxidase detection systems. The radicle, root cap and coleorhiza first accumulated WGA in early Stage II (8-10 d post-anthesis) prior to the main period of embryo growth, while WGA was found in the epiblast and coleoptile in early and late State III, respectively. Stage III is characterized by maximum embryo growth, followed by desiccation which occurs in Stage IV. When Stage-II embryos were precociously germinated in the absence of abscisic acid (ABA) no WGA was detected in the coleoptile and epiblast of the young seedlings. In the presence of ABA, Stage-II embryos did not germinate but WGA precociously accumulated in the coleoptile and epiblast. The levels and distribution of WGA in the resulting embryo resembled those in a fully mature, dry embryo (Stage V). Barley possesses a seed lectin similar to WGA, but it is never detected in coleoptiles. Some but not all of the barley cultivars tested were found to accumulate lectin in this organ of mature embryos when treated with ABA. Thus, ABA appears to be involved in the highly regulated temporal and spatial expression of WGA during embryogenesis in cereals.Abbreviations ABA
abscisic acid
- DIC
differential interference contrast
- PAP
peroxidase-antiperoxidase
- WGA
wheat-germ agglutinin 相似文献
6.
Interaction of a potential vacuolar targeting receptor with amino- and carboxyl-terminal targeting determinants. 总被引:21,自引:6,他引:15
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A protein of 80 kD from developing pea (Pisum sativum) cotyledons has previously been shown to exhibit characteristics of a vacuolar targeting receptor by means of its affinity for the amino-terminal vacuolar targeting sequence of proaleurain from barley (Hordeum vulgare). In this report we show that the same protein also binds to the amino-terminal targeting peptide of prosporamin from sweet potato (Ipomoea batatas) and to the carboxyl-terminal targeting determinant of pro-2S albumin from Brazil nut (Bertholletia excelsa). The receptor protein does not bind to the carboxyl-terminal propeptide (representing the targeting sequence) of barley lectin. The binding of the 80-kD protein to the sporamin determinant involves a motif (NPIR) that has been shown to be crucial for vacuolar targeting in vivo. The binding to the carboxyl-terminal targeting determinant of pro-2S albumin appears to involve the carboxyl-terminal propeptide and the adjacent five amino acids of the mature protein. The 80-kD protein does not bind to peptide sequences that have been shown to be incompetent in directing vacuolar targeting. 相似文献
7.
Wine vinegar is a product obtained from wine acidification which contains at least 5% by wt. of acetic acid, in general without any additives or colorings.
Aspects studied in this work include: the determination of the taste group thresholds (geometric mean of the individual best-estimate thresholds "BET") of two different acids (citric and acetic acids) in aqueous solution and spanish vinegars produced from table and sherry wines. The results obtained suggest that wine vinegar can be considered something more than just an acidulant agent.
In order to evaluate differences among wine vinegars, discriminant tests for twenty-five spanish vinegars (sherry, table and flavored vinegars) were applied. Six of the twelve attributes freely chosen by assessors allowed grouping of the spanish wine vinegars according to their sensory aspects. 相似文献
Aspects studied in this work include: the determination of the taste group thresholds (geometric mean of the individual best-estimate thresholds "BET") of two different acids (citric and acetic acids) in aqueous solution and spanish vinegars produced from table and sherry wines. The results obtained suggest that wine vinegar can be considered something more than just an acidulant agent.
In order to evaluate differences among wine vinegars, discriminant tests for twenty-five spanish vinegars (sherry, table and flavored vinegars) were applied. Six of the twelve attributes freely chosen by assessors allowed grouping of the spanish wine vinegars according to their sensory aspects. 相似文献
8.
The aspartic proteinase of barley is a vacuolar enzyme that processes probarley lectin in vitro. 总被引:8,自引:1,他引:7
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Previous work suggested that the aspartic proteinase from Hordeum vulgare (HvAP) would be a vacuolar protein in plant cells. Based on N-terminal sequencing we show that the in vitro-translated protein was translocated into the lumen of microsomal membranes, causing a concomitant removal of 25 amino acid residues from the protein. Vacuoles were purified from barley leaf protoplasts and were shown to contain all of the aspartic proteinase activity found in the protoplasts. This vacuolar localization of HvAP was confirmed with immunocytochemical electron microscopy using antibodies to HvAP in both barley leaf and root cells. In an attempt to discern a function for this protease, we investigated the ability of HvAP to process the C-terminal proregion of barley lectin (BL) in vitro. Prolectin (proBL), expressed in bacteria, was processed rapidly when HvAP was added. Using several means, we were able to determine that 13 amino acid residues at the C terminus of proBL were cleaved off, whereas the N terminus stayed intact during this incubation. Immunohistochemical electron microscopy showed that HvAP and BL are co-localized in the root cells of developing embryos and germinating seedlings. Thus, we propose that the vacuolar HvAP participates in processing the C terminus of BL. 相似文献
9.
Extensive Sequence Conservation Among Insect,Nematode, and Vertebrate Vitellogenins Reveals Ancient Common Ancestry 总被引:10,自引:0,他引:10
Jeng-Shong Chen Thomas W. Sappington Alexander S. Raikhel 《Journal of molecular evolution》1997,44(4):440-451
The eggs of most oviparous animals are provisioned with a class of protein called vitellogenin (Vg) which is stored as the
major component of yolk. Until recently, deduced amino acid sequences were available only from vertebrate and nematode Vgs,
which proved to be homologous. The sequences of several insect Vgs are now known, but early attempts at pairwise alignments
with vertebrate and nematode Vgs have been problematic, leading to conflicting conclusions about how closely insect Vgs are
related to the others. In this paper we demonstrate that insect Vg sequences can be confidently aligned with one another along
their entire lengths and with multiple vertebrate and nematode Vg sequences along most of their spans. Although divergence
is high, conservation among insect, vertebrate, and nematode Vg sequences is widespread with a preponderance of glycine, proline,
and cysteine residues among strictly conserved amino acids, establishing conclusively that Vgs from the three phyla are homologous.
Areas of least-certain alignment are primarily in and around insect and vertebrate polyserine domains which are not homologous.
Phylogenetic reconstructions of Vgs based on sequence identities indicate that the insect lineage is the most diverged and
that the mammalian serum protein, apolipoprotein B-100, arose from a Vg ancestor after the nematode/vertebrate divergence.
Received: 6 May 1996 / Accepted: 27 September 1996 相似文献
10.
When exponentially growing KB cells were deprived of arginine, cell multiplication ceased after 12 h but viability was maintained throughout the experimental period (42-48 h). Although tritiated thymidine ([(3)H]TdR) incorporation into acid-insoluble material declined to 5 percent of the initial rate, the fraction of cells engaged in DNA synthesis, determined by autoradiography, remained constant throughout the starvation period and approximately equal to the synthesizing fraction in exponentially growing controls (40 percent). Continous [(3)H]TdR-labeling indicated that 80 percent of the arginine-starved cells incorporated (3)H at some time during a 48-h deprivation period. Thus, some cells ceased DNA synthesis, whereas some initially nonsynthesizing cells initiated DNA synthesis during starvation. Flow microfluorometric profiles of distribution of cellular DNA contents at the end of the starvation period indicated that essentially no cells had a 4c or G2 complement. If arginine was restored after 30 h of starvation, cultures resumed active, largely asynchronous division after a 16-h lag. Autoradiographs of metaphase figures from cultures continuously labeled with [(3)H]TdR after restoration indicated that all cells in the culture underwent DNA synthesis before dividing. It was concluded that the majority of cells in arginine-starved cultures are arrested in neither a normal G1 nor G2. It is proposed that for an exponential culture, i.e. from most positions in the cell cycle, inhibition of cell growth after arginine with withdrawal centers on the ability of cells to complete replication of their DNA. 相似文献