全文获取类型
收费全文 | 8675篇 |
免费 | 762篇 |
国内免费 | 204篇 |
出版年
2023年 | 46篇 |
2022年 | 142篇 |
2021年 | 209篇 |
2020年 | 154篇 |
2019年 | 205篇 |
2018年 | 265篇 |
2017年 | 211篇 |
2016年 | 338篇 |
2015年 | 472篇 |
2014年 | 569篇 |
2013年 | 613篇 |
2012年 | 808篇 |
2011年 | 672篇 |
2010年 | 478篇 |
2009年 | 391篇 |
2008年 | 544篇 |
2007年 | 532篇 |
2006年 | 488篇 |
2005年 | 399篇 |
2004年 | 384篇 |
2003年 | 360篇 |
2002年 | 262篇 |
2001年 | 165篇 |
2000年 | 124篇 |
1999年 | 88篇 |
1998年 | 63篇 |
1997年 | 46篇 |
1996年 | 36篇 |
1995年 | 34篇 |
1994年 | 32篇 |
1993年 | 13篇 |
1992年 | 44篇 |
1991年 | 34篇 |
1990年 | 33篇 |
1989年 | 32篇 |
1988年 | 32篇 |
1987年 | 20篇 |
1986年 | 26篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 23篇 |
1982年 | 16篇 |
1981年 | 20篇 |
1980年 | 11篇 |
1979年 | 13篇 |
1977年 | 15篇 |
1976年 | 12篇 |
1975年 | 11篇 |
1973年 | 12篇 |
1972年 | 12篇 |
排序方式: 共有9641条查询结果,搜索用时 15 毫秒
61.
Teng Man Zhu Zhi-Jian Yao Yongxiu Nair Venugopal Zhang Gai-Ping Luo Jun 《中国科学:生命科学英文版》2023,66(2):251-268
Science China Life Sciences - Over the past two decades, numerous non-coding RNAs (ncRNAs) have been identified in different biological systems including virology, especially in large DNA viruses... 相似文献
62.
Application of abscisic acid (ABA) brings about stomatal closure within 30 min in epidermal peels of Vicia faba . A number of phenolic compounds antagonise the effect of ABA. Derivatives of benzoic acid, cinnamic acid, coumarin and flavonoids have been studied in order to establish structure – activity relationship. Derivatives of benzoic acid reverse the ABA effects. Coumarin, esculetin and three hydro derivatives of cinnamic acid fail to show the anti-ABA activity. Thus, the presence of parahydroxyl group and double bond in the side chain is necessary for anti-ABA activity. 相似文献
63.
Complete larval development of Crangon hakodatei Rathbun isdescribed, based on material hatched in the laboratory fromovigerous females. The species has six zoeal stages and onepostlarval stage. The morphological characters of the larvaland postlarval stages are described with illustrative figuresand compared with those of two congeneric species. The zoealstages of C. hakodatei can be distinguished from those of otherCrangon species in the number of segments of the antennule peduncle,the number of setae on the antennal scale and basis of the maxillipeds,and the stages of appearance of pereiopods. The first zoealstage in the seven species of Crangon are compared and an annotatedkey for distinguishing them is also provided. 相似文献
64.
65.
Cucumber (Cucumis sativus L.) seedlings were grafted onto cucumber-(CG) or figleaf gourd- (FG, Cucurbita ficifolia Bouché)seedlings in order to determine the effect of solution temperature(12, 22, and 32°C) on the mineral composition of xylem sapand the plasma membrane K+-Mg++-ATPase activities of the roots.Low solution temperature (12°C) lowered the concentrationof NO3 and H2PO4 in xylem sap of CG plants butnot of FG plants. Concentrations of K+, Ca++ and Mg++ in xylemsap were less affected than anions by solution temperature.The plasma membrane of FG plants grown in 12°C solutiontemperature showed the highest K+- Mg++-ATPase activity at allATP concentrations up to 3 mM and at low reaction temperatureup to 12°C, indicating resistance of figleaf gourd to lowroot temperature. (Received December 27, 1994; Accepted March 10, 1995) 相似文献
66.
Identification of three genetic loci controlling leaf senescence in Arabidopsis thaliana 总被引:23,自引:3,他引:20
Sung Aeong Oh Joon-Hyun Park Gyu In Lee Kyung Hee Paek Soon Ki Park Hong Gil Nam 《The Plant journal : for cell and molecular biology》1997,12(3):527-535
Four mutants that show the delayed leaf senescence phenotype were isolated from Arabidopsis thaliana . Genetic analyses revealed that they are all monogenic recessive mutations and fall into three complementation groups, identifying three genetic loci controlling leaf senescence in Arabidopsis . Mutations in these loci cause delay in all senescence parameters examined, including chlorophyll content, photochemical efficiency of photosystem II, relative amount of the large subunit of Rubisco, and RNase and peroxidase activity. Delay of the senescence symptoms was observed during both age-dependent in planta senescence and dark-induced artificial senescence in all of the mutant plants. The results indicate that the three genes defined by the mutations are key genetic elements controlling functional leaf senescence and provide decisive genetic evidence that leaf senescence is a genetically programmed phenomenon controlled by several monogenic loci in Arabidopsis . The results further suggest that the three genes function at a common step of age-dependent and dark-induced senescence processes. It is further shown that one of the mutations is allelic to ein2-1 , an ethylene-insensitive mutation, confirming the role of ethylene signal transduction pathway in leaf senescence of Arabidopsis . 相似文献
67.
To understand the genetic regulation of vegetative to reproductive transition in higher plants, further characterization of the Arabidopsis mutant embryonic flower1, emf1, was conducted. Using three flowering symptoms, we showed that emf1 mutants could only grow reproductive and not rosette shoots under five different growth conditions. The mutant embryos did not produce the typical tunica–corpus shoot apical structures at the heart-, torpedo-, and mature stages. The divergent shoot apical development during mutant and wild-type embryogenesis indicated that the wild-type EMF1 gene was expressed in early embryogenesis. Mutations in the EMF1 gene affected the embryonic shoot apical development and caused the germinating embryo and regenerating callus to grow inflorescence, instead of rosette, shoots. Our results support the hypothesis that the EMF1 gene regulates the switch between vegetative and reproductive growth in Arabidopsis. 相似文献
68.
Callus cultures and cell suspension cultures derived from Ginkgo biloba L. leaves produced ginkgolidc B. In cell suspension cultures, the production reached a maximum by the 13th day of subculture and followed by a sharp decrease. The medium of Murashige and Skoog induced the highest ginkgolide B content in cultures while the medium of Schenk and Hildebrandt promoted cell growth. For the maximal production of ginkgolide B, cells were cultured in Murashige and Skoog medium modified to contain 1.0 mg/l of -naphthaleneacetic acid, 0.1 mg/1 of kinetin, 30 g/1 sucrose and 1.25 mM potassium phosphate with a molar ratio of ammonium to nitrate ions of 1 3.Abbreviations B5
Gamborg et al (1968) medium
- GKB
Ginkgolide B
- MS
Murashige and Skoog (1962) medium
- NAA
-naphthaleneacetic aicd
- SH
Schenk and Hildebrandt (1972) medium 相似文献
69.
Ergosterol, a membrane sterol found in fungi but not in plants, was used to estimate live mycelial biomass in ectomycorrhizae. Loblolly pine (Pinus taeda L.) seeds were sown in April 1993 and grown with standard nursery culture practices. Correlations between total seedling ergosterol and visual assessment of mycorrhizal colonization were high during July and August but low as ectomycorrhizal development continued into the growing season. Percentages of mycelial dry weight over lateral roots decreased from 9% in July to 2.5% in November because seedling lateral root dry weight accumulated faster than mycelial dry weight. Total ergosterol per seedling increased from July through February. As lateral root dry weight ceased to increase during winter months, ectomycorrhizal mycelia became the major carbohydrate sink of pine seedlings. No distinctive seasonal pattern of soil ergosterol content was observed. The impact of ectomycorrhizal fungi on plant carbohydrate source-sink dynamics can be quantitatively estimated with ergosterol analysis but not with conventional visual determination. 相似文献
70.
Man S. F.; Hulbert W.; Park D. S.; Thomson A. B.; Hogg J. C. 《Journal of applied physiology》1984,57(5):1338-1346