全文获取类型
收费全文 | 1773篇 |
免费 | 215篇 |
国内免费 | 65篇 |
出版年
2023年 | 36篇 |
2022年 | 45篇 |
2021年 | 61篇 |
2020年 | 76篇 |
2019年 | 74篇 |
2018年 | 65篇 |
2017年 | 49篇 |
2016年 | 90篇 |
2015年 | 89篇 |
2014年 | 94篇 |
2013年 | 122篇 |
2012年 | 80篇 |
2011年 | 73篇 |
2010年 | 77篇 |
2009年 | 79篇 |
2008年 | 66篇 |
2007年 | 68篇 |
2006年 | 83篇 |
2005年 | 67篇 |
2004年 | 57篇 |
2003年 | 74篇 |
2002年 | 59篇 |
2001年 | 62篇 |
2000年 | 43篇 |
1999年 | 41篇 |
1998年 | 31篇 |
1997年 | 33篇 |
1996年 | 36篇 |
1995年 | 29篇 |
1994年 | 20篇 |
1993年 | 31篇 |
1992年 | 25篇 |
1991年 | 19篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 8篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1950年 | 2篇 |
排序方式: 共有2053条查询结果,搜索用时 15 毫秒
1.
Kentaro M. Tanaka Aya Takahashi Naoyuki Fuse Toshiyuki Takano-Shimizu-Kouno 《Genetics》2014,197(2):739-742
Cell death is a mechanism utilized by organisms to eliminate excess cells during development. Here, we describe a novel regulator of caspase-independent cell death, Mabiki (Mabi), that is involved in the repair of the head patterning defects caused by extra copies of bicoid in Drosophila melanogaster. Mabiki functions together with caspase-dependent cell death mechanisms to provide robustness during development. 相似文献
2.
Florian Villegas Daphné Lehalle Daniela Mayer Melanie Rittirsch Michael B. Stadler Marietta Zinner Daniel Olivieri Pierre Vabres Laurence Duplomb-Jego Eveline S.J.M. De Bont Yannis Duffourd Floor Duijkers Magali Avila David Geneviève Nada Houcinat Thibaud Jouan Paul Kuentz Klaske D. Lichtenbelt Joerg Betschinger 《Cell Stem Cell》2019,24(2):257-270.e8
3.
The consequences of early developmental conditions for performance in later life are now subjected to convergent interest from many different biological sub-disciplines. However, striking data, largely from the biomedical literature, show that environmental effects experienced even before conception can be transmissible to subsequent generations. Here, we review the growing evidence from natural systems for these cross-generational effects of early life conditions, showing that they can be generated by diverse environmental stressors, affect offspring in many ways and can be transmitted directly or indirectly by both parental lines for several generations. In doing so, we emphasize why early life might be so sensitive to the transmission of environmentally induced effects across generations. We also summarize recent theoretical advancements within the field of developmental plasticity, and discuss how parents might assemble different ‘internal’ and ‘external’ cues, even from the earliest stages of life, to instruct their investment decisions in offspring. In doing so, we provide a preliminary framework within the context of adaptive plasticity for understanding inter-generational phenomena that arise from early life conditions. 相似文献
4.
The ability of most higher plants to withstand freezing can be enhanced by cold acclimation, although the freezing tolerance of plant tissues is also affected by their developmental stage. In addition, low temperature has pleiotropic effects on many plant developmental processes such as vernalization. The interaction between plant development and low temperature implies that some genes are regulated by both environmental factors and developmental cues. Although a number of cold-inducible genes from plants have been identified, information concerning their regulation during plant development is limited. In order to understand their developmental regulation and obtain possible clues as to function, the promoters of kin1 and cor6.6, two cold- and abscisic acid (ABA)-regulated genes from Arabidopsis thaliana, were fused to the -glucuronidase (GUS)-coding sequence and the resulting constructs were used to transform tobacco and A. thaliana. Transgenic plants with either the kin1 or cor6.6 promoter showed strong GUS expression in pollen, developing seeds, trichomes and, most interestingly, in guard cells. During pollen development, maximum GUS activity was found in mature pollen. In contrast, the maximum GUS activity during seed development was during early embryogenesis. These patterns of expression distinguish kin1 and cor6.6 from related lea genes which are strongly expressed during late embryogenesis. There was no major qualitative difference in patterns of GUS expression between kin1 and cor6.6 promoters and the results were similar for transgenic tobacco and Arabidopsis. Considering the results described, as well as those in an accompanying paper Wang et al., 1995, Plant Mol Biol 28: 605–617 (this issue), we suggest that osmotic potential might be a major factor in regulating the expression of kin1 and cor6.6 during several developmental processes. The implication of the results for possible function of the gene products is discussed. 相似文献
5.
6.
7.
8.
The distribution of morphological structures was studied in wings of the banded agrion (Calopteryx splendens Harr.) from different intrapopulation groups. Dragon flies of odd years of emergence are characterized by a more stable pattern of ontogenetic processes according to the mean total number of venation defects. The sharply increased level of radiation in summer 1986, which coincided with the flight of dragon-flies, could have caused hereditary defects expressed in a sequence of generations of even years of emergence. Apparently, most alternative features of wing venation in dragon-flies can be considered as markers of stability of the ontogenetic processes, which reflect, to a great extent, genotypic features of the organisms in a population. A possible mechanism has been described, which explains the proposed topological model of formation of the venation defects of different types. The increase in mean frequencies of defects can suggest an enhanced development over the aberrant epigenetic trajectories, which may lead to the elimination of these organisms under the influence of various agents, i.e., to the stabilizing selection in a population. The results obtained suggest that defects of venation arise on the stochastic basis and their frequency increases upon destabilization of ontogenetic processes not only by the environmental factors, but also by genetic stress. Venation defects can be successfully used in population biomonitoring. 相似文献
9.
The grape leafhopper Empoasca vitis (Homoptera: Cicadellidae) is regarded as a major insect pest in many European grapevine growing areas, with an increasing importance realized in recent years maybe as a result of climatic change. Both larvae and adults feed on the phloem vessels of the leaves, causing characteristic symptoms also referred to as hopperburn. Phenology of adult leafhoppers was monitored in one vineyard in three successive years and indicated that immigration of a few hibernated E. vitis individuals into vineyards might take place already quite early in the year depending on winter temperatures and starts to progress in substantial numbers right at grapevine bud burst. In addition, these monitoring studies have shown that there are several other leafhopper species occurring on grapevine plants besides E. vitis, such as the rose leafhopper Edwardsiana rosae (Homoptera: Cicadellidae). Here, we report on the development of larval instars of both leafhopper species, E. vitis and E. rosae on grapevine leaves under different temperature regimes in the laboratory. Shortest larval developmental time was observed at night temperatures of 13–15°C and day temperatures of 23–25°C, which was in agreement with predicted optimal temperatures for both species. At the temperature regime of 20°C night and 30°C day temperature, either no egg hatch was observed or early development of first‐instar larvae was not successful for both species. These results suggest that warm (18°C) nights and moderately warm (28°C) days are representing the upper thermal threshold for development of both E. vitis and E. rosae embryonic stages on grapevine leaves, questioning current assumptions of an increasing importance of E. vitis as a grapevine pest under future climate change. 相似文献
10.
D. M. Marinkovi 《Journal of Zoological Systematics and Evolutionary Research》1999,37(3):113-120
Among 400 Drosophila melanogaster flies individually analysed for nine gene–enzyme systems, a total of 160 different genotypes were found: 78 were repeatedly observed in two to 22 individuals, and 82 appeared only once. An increase in the frequency of rare alleles could be observed in such groups of genotypes that were less frequent. Among 24 most frequent genotypes (in 189 individuals) only four different combinations of five third-chromosomal genes are present, and 12 different combinations of three second-chromosomal genes. Among 82 unique genotypes these combinations were much more versatile: 29 at the third, 22 at the second, and three at the first chromosomes. The proportion of heterozygotes was increasing from most frequent toward unique genotypes (1.5–2.1 ± 0.1), primarily due to heterozygosity in five third-chromosomal loci (0.4–1.1 ± 0.06). When the number of genotypes in 100, 200, 300 and 400 sampled flies was extrapolated to larger samples, it became clear that this increase has an asymptotic character. It must be assumed that for our nine-loci model a total of approximately 200–220 different genotypes may exist in a population of a few thousands individuals, which means that adaptive variation for such a complex gene–enzyme system must be very much limited. 相似文献