全文获取类型
收费全文 | 763篇 |
免费 | 26篇 |
国内免费 | 88篇 |
专业分类
877篇 |
出版年
2024年 | 3篇 |
2023年 | 9篇 |
2022年 | 17篇 |
2021年 | 9篇 |
2020年 | 11篇 |
2019年 | 13篇 |
2018年 | 15篇 |
2017年 | 20篇 |
2016年 | 14篇 |
2015年 | 17篇 |
2014年 | 41篇 |
2013年 | 20篇 |
2012年 | 26篇 |
2011年 | 20篇 |
2010年 | 19篇 |
2009年 | 47篇 |
2008年 | 50篇 |
2007年 | 44篇 |
2006年 | 48篇 |
2005年 | 44篇 |
2004年 | 38篇 |
2003年 | 32篇 |
2002年 | 19篇 |
2001年 | 17篇 |
2000年 | 23篇 |
1999年 | 27篇 |
1998年 | 28篇 |
1997年 | 15篇 |
1996年 | 23篇 |
1995年 | 9篇 |
1994年 | 17篇 |
1993年 | 22篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有877条查询结果,搜索用时 9 毫秒
51.
In order to clearly establish the properties of the enzymes responsible for hexose phosphorylation we have undertaken the
separation and characterization of these enzymes present in tomato fruit (Martinez-Barajas and Randall 1996). This report
describes the partial purification and characterization of glucokinase (EC. 2.7.1.1) from young green tomato fruit. The procedure
yielded a 360-fold enrichment of glucokinase. Tomato fruit glucokinase is a monomer with a molecular mass of 53 kDa. Glucokinase
activity was optimal between pH 7.5 and 8.5, preferred ATP as the phosphate donor (K
m = 0.223 mM) and exhibited low activity with GTP or UTP. The tomato fruit glucokinase showed highest affinity for glucose
(K
m = 65 μM). Activity observed with glucose was 4-fold greater than with mannose and 50-fold greater than with fructose. The tomato
fruit glucokinase was sensitive to product inhibition by ADP (K
i = 36 μM). Little inhibition was observed with glucose 6-phosphate (up to 15 mM) at pH 8.0; however, at pH 7.0 glucokinase
activity was inhibited 30–50% by physiological concentrations of glucose 6-phosphate.
Received: 4 October 1997 / Accepted: 10 January 1998 相似文献
52.
R. Socias i Company 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(5):588-601
The large size and the long generation time of fruit trees generally reduce the possibilities of obtaining genetic information
on the transmission and heritability of useful agronomic traits in these species. However, from breeding work carried out
with fruit trees, an important amount of data is now available, although large differences are apparent among the different
species. There is not much information known about almond compared to what is available on other Prunus fruit species, but more data have been accumulated on it than on most of the other nut trees, thus making almond special
among all the temperate fruit and nut species. Only five qualitative traits have been described in almond, with an additional
two also possibly qualitative. Heritabilities have been estimated for an important number of quantitative traits, mainly phenological
times and fruit characters. Important information is available on molecular markers, including enzymes, RFLPs, RAPDs and other
recently developed markers. Linkages, however, have only been established among molecular markers, allowing accurate genetic
maps to be built but not yet enabling agronomical characters to be located in these maps, probably because the latter have
not been sufficiently studied. The effectiveness of the application of genetic maps in plant breeding will depend on the accuracy
of the study of different agronomic traits and their expression, implying more field work and recognition of this work. Ultimately,
any new fruit cultivar has to be grown in the field and has to allow the grower to make a profit.
Received: 1 June 1997 / Accepted: 1 September 1997 相似文献
53.
54.
Unlike most pollinators, yucca moths are active pollinators of their host plants. Females lay their eggs in the flowers they pollinate, and their larvae feed solely on the resulting seeds. Previous evidence suggests that the yucca moth Tegeticula maculata avoids self-pollinating their host Yucca whipplei . Other yucca moths may self-pollinate more frequently. When pollinating, yucca moths are also reported to fly large distances between plants, bypassing neighbouring plants in the process. We experimentally verify the suggestion of Pellmyr et al . that yucca is more likely to retain fruits from self-pollination if overall fruit set is low. Thus, selection on moths to avoid self-pollinating should be density dependent. We found no evidence that mating with close neighbours resulted in inbreeding depression, thus the moth's long-distance flights between plants are yet to be explained. 相似文献
55.
1. Insect oral secretions are important for the induction of a number of plant responses, but the relative role of mechanical damage in the induction of these responses is often not well understood. Damage from the frugivore Heliothis subflexa, a specialist on Physalis species, causes herbivore‐induced fruit abscission. In this field study, we examined the separate and combined effects of mechanical damage and H. subflexa oral secretions on Physalis fruit abscission. 2. To determine the relative role of mechanical and chemical factors, the following treatments were administered to fruit: (1) three levels of mechanical damage, (2) natural herbivore damage by control larvae and by larvae surgically treated to inhibit saliva secretion, and (3) injection of H.subflexa oral secretions and a water control. Abscission of mechanically damaged fruit with and without the addition of oral secretions was also compared. 3. Mechanical damage was sufficient to cause fruit abscission, and the addition of oral secretions to mechanically damaged fruit did not cause an increase in fruit abscission. Normal caterpillars and those treated to inhibit saliva secretion caused similar abscission rates. 4. Though most studies examining the effects of insect oral secretions on induced plant responses find these chemical stimuli to be important or essential, the results of the present study showed that oral secretions are not necessary for fruit abscission. Future work is needed to determine the relative importance of mechanical damage in herbivore‐induced plant responses in other systems. 相似文献
56.
Vishwas A. Bapat Prabodh K. Trivedi Antara Ghosh Vidhu A. Sane Thumballi R. Ganapathi Pravendra Nath 《Biotechnology advances》2010
Development and ripening in fruit is a unique phase in the life cycle of higher plants which encompasses several stages progressively such as fruit development, its maturation, ripening and finally senescence. During ripening phase, several physiological and biochemical changes take place through differential expression of various genes that are developmentally regulated. Expression and/or suppression of these genes contribute to various changes in the fruit that make it visually attractive and edible. However, in fleshy fruit massive losses accrue during post harvest handling of the fruit which may run into billions of dollars worldwide. This encouraged scientists to look for various ways to save these losses. Genetic engineering appears to be the most promising and cost effective means to prevent these losses. Most fleshy fruit ripen in the presence of ethylene and once ripening has been initiated proceeds uncontrollably. Ethylene evokes several responses during ripening through a signaling cascade and thousands of genes participate which not only sets in ripening but also responsible for its spoilage. Slowing down post ripening process in fleshy fruit has been the major focus of ripening-related research. In this review article, various developments that have taken place in the last decade with respect to identifying and altering the function of ripening-related genes have been described. Role of ethylene and ethylene-responsive genes in ripening of fleshy fruit is also included. Taking clues from the studies in tomato as a model fruit, few case studies are reviewed. 相似文献
57.
Monitoring ethylene is crucial in regulating post-harvest life of fruits. The concept of nitric oxide (NO) involvement in antagonizing ethylene is new. NO mediated physiologies casted through regulation of plant hormones are widely reported during developmental and stress chemistry having no direct link with ripening. Research in NO biology and understanding its interplay with other signal molecules in ripening fruits suggest ways of achieving greater synergies with NO applications. Experiments focused at convincingly demonstrating the involvement of NO in altering ripening-related ethylene profile of fruits, would help develop new processes for shelf life extension. This issue being the central theme of this review, the putative mechanisms of NO intricacies with other primary and secondary signals are hypothesized. The advantage of eliciting NO endogenously may open up various biotechnological opportunities for its precise delivery into the target tissues. 相似文献
58.
60.
The populations of native male adult oriental fruit fly Dacus dorsalis (Hendel ) and artocarpus fruit fly D. umbrosus (F.) in two selected site (BU and SD) were estimated weekly by the capture-recapture technique using live traps baited with methyl eugenol. In BU where many varieties of fruit trees were grown, the estimated population densities of D. dorsalis were between 980 and 3100 male flies per ha between May and July, 1984. During the same period, in SD where there were fewer number and varieties of fruit trees, the estimated population densities were between 300 and 1000 flies per ha. The estimated population densities of D. umbrosus over the same period were between 570 and 1290 flies per ha in BU; and between 5 and 95 flies per ha in SD. Of a total 6828 marked D. dorsalis flies released only one fly (released 6 weeks earlier in BU) was caught in a different site. 相似文献