全文获取类型
收费全文 | 3130篇 |
免费 | 262篇 |
国内免费 | 4篇 |
出版年
2023年 | 21篇 |
2022年 | 41篇 |
2021年 | 106篇 |
2020年 | 52篇 |
2019年 | 71篇 |
2018年 | 81篇 |
2017年 | 58篇 |
2016年 | 98篇 |
2015年 | 183篇 |
2014年 | 203篇 |
2013年 | 233篇 |
2012年 | 240篇 |
2011年 | 243篇 |
2010年 | 166篇 |
2009年 | 123篇 |
2008年 | 182篇 |
2007年 | 173篇 |
2006年 | 149篇 |
2005年 | 147篇 |
2004年 | 145篇 |
2003年 | 121篇 |
2002年 | 91篇 |
2001年 | 25篇 |
2000年 | 17篇 |
1999年 | 21篇 |
1998年 | 28篇 |
1997年 | 20篇 |
1996年 | 11篇 |
1995年 | 20篇 |
1994年 | 21篇 |
1993年 | 26篇 |
1992年 | 19篇 |
1991年 | 18篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1976年 | 10篇 |
1974年 | 11篇 |
1973年 | 11篇 |
1972年 | 7篇 |
排序方式: 共有3396条查询结果,搜索用时 93 毫秒
1.
2.
Abstract The natural product cyanobacterin has been shown to be toxic to most cyanobacteria at a concentration of approx. 5 μM. We demonstrate here that cyanobacterin will also inhibit the growth of most eukaryotic algae at a similar concentration. Some algae, such as Euglena gracilis , are resistant because they are able to maintain themselves by heterotrophic nutrition. Others, such as Chlamydomonas reinhardtii , can apparently induce a detoxification mechanism to maintain photosynthesis in the presence of low concentrations of the inhibitor. Non-photosynthetic microorganisms are not affected by cyanobacterin. 相似文献
3.
Danielle E. Haulsee Dewayne A. Fox Matthew W. Breece Tonya M. Clauss Matthew J. Oliver 《PloS one》2016,11(2)
We developed a long-term tagging method that can be used to understand species assemblages and social groupings associated with large marine fishes such as the Sand Tiger shark Carcharias taurus. We deployed internally implanted archival VEMCO Mobile Transceivers (VMTs; VEMCO Ltd. Nova Scotia, Canada) in 20 adult Sand Tigers, of which two tags were successfully recovered (10%). The recovered VMTs recorded 29,646 and 44,210 detections of telemetered animals respectively. To our knowledge, this is the first study to demonstrate a method for long-term (~ 1 year) archival acoustic transceiver tag implantation, retention, and recovery in a highly migratory marine fish. Results show low presumed mortality (n = 1, 5%), high VMT retention, and that non-lethal recovery after almost a year at liberty can be achieved for archival acoustic transceivers. This method can be applied to study the social interactions and behavioral ecology of large marine fishes. 相似文献
4.
5.
6.
Frank H. Gleason Steve K. Schmidt Agostina V. Marano 《Extremophiles : life under extreme conditions》2010,14(5):417-425
Zoosporic true fungi are thought to be ubiquitous in many ecosystems, especially in cool, moist soils and freshwater habitats
which are rich in organic matter. However, some of the habitats where these fungi are found may periodically experience extreme
conditions, such as soils in extremely dry, hot and cold climates, acidic and alkaline soils, polluted rivers, anaerobic soil
and water, saline soil and water, periglacial soils, oligotrophic soils, tree canopies and hydrothermal vents. It is clear
that many ecotypes of zoosporic true fungi have indeed adapted to extreme or stressful environmental conditions. This conclusion
is supported by studies in both the field and in the laboratory. Therefore, in our opinion, at least some true zoosporic fungi
can be considered to be extremophiles. 相似文献
7.
8.
9.
Danielle L. Laval-Martin Isabelle A. Carr Saverio J. Barbera Leland N. Edmunds 《Chronobiology international》1990,7(2):99-105
-We have previously shown that NAD kinase and NADP phosphatase activities display circadian rhythms, in the soluble (SN) and membrane-bound (P) fractions of crude extracts of the achlorophyllous ZC mutant of the phytoflagellate Euglena gracilis (which displays circadian rhythmicity of cell division). We determined if changes in the affinity of NADP phosphatase and NAD kinase for their substrates, NADP+ and NAD+, were occurring by calculating the ratios 100(velocity found in Km conditions/velocity found in saturating conditions). The rationale was that if the affinity remained unchanged according to circadian time (CI), these values should always equal 50, independently of any changes in enzyme quantity; values greater than 50 should indicate increases in enzyme affinity, and values less than 50 decreases in affinity. Our results indicated that these values calculated for NADP phosphatase exhibited a complex pattern of rhythmicity, while those for NAD kinase displayed circadian variations strongly correlated with the rhythms in enzyme activity. The curves showed troughs at CT 00-04 both in dividing and nondividing cells and peaks at CT 18-20 or at CT 08-14 in cells sampled, respectively, from a dividing or a stationary culture. Such variations are indicative of changes in the kinetic properties of the enzyme, which may reflect modifications in its affinity either for effectors (such as Ca2+-calmodulin) or for its substrate, NAD+. This may be due to (i) the expression of different isoenzymes at different CTs; (ii) different posttranslational modifications of the enzyme; or (iii) concentrations of effectors varying in a circadian manner. 相似文献
10.
A simple procedure is described for the determination of the photosensitizing potency of drugs, using three leukemic cell lines, two of lymphocytic origin, L1210 and P388 and one of erythroid type, Friend-745. The procedure allows one to investigate several aspects of the photosensitization properties of tested compounds such as cellular localization and direct (trypan blue exclusion) or delayed (clonogenicity) photomediated toxicities.The method was assessed using crude hematoporphyrin derivative (HPD) as well as dihematoporphyrin ether (DHE) or commercially available Photofrin II. Results were compared to those obtained with normal cells, e.g spleen lymphocytes and erythropoietic stem cells (CFU-e), and discussed in the light of the relative response of normal versus transformed cells.Abbreviations DHE
Dihematoporphyrin Ether
- FCS
Fetal Calf Serum
- HPD
Hematoporphyrin Derivative
- PDT
Photodynamic Therapy 相似文献