全文获取类型
收费全文 | 3164篇 |
免费 | 315篇 |
出版年
2021年 | 43篇 |
2019年 | 36篇 |
2018年 | 43篇 |
2017年 | 33篇 |
2016年 | 36篇 |
2015年 | 94篇 |
2014年 | 120篇 |
2013年 | 146篇 |
2012年 | 160篇 |
2011年 | 143篇 |
2010年 | 103篇 |
2009年 | 81篇 |
2008年 | 136篇 |
2007年 | 120篇 |
2006年 | 112篇 |
2005年 | 110篇 |
2004年 | 95篇 |
2003年 | 102篇 |
2002年 | 96篇 |
2001年 | 108篇 |
2000年 | 110篇 |
1999年 | 105篇 |
1998年 | 52篇 |
1997年 | 34篇 |
1996年 | 39篇 |
1995年 | 34篇 |
1994年 | 43篇 |
1993年 | 29篇 |
1992年 | 55篇 |
1991年 | 55篇 |
1990年 | 64篇 |
1989年 | 64篇 |
1988年 | 57篇 |
1987年 | 50篇 |
1986年 | 54篇 |
1985年 | 54篇 |
1984年 | 42篇 |
1983年 | 27篇 |
1982年 | 35篇 |
1980年 | 28篇 |
1979年 | 28篇 |
1978年 | 39篇 |
1976年 | 34篇 |
1975年 | 36篇 |
1974年 | 31篇 |
1973年 | 29篇 |
1972年 | 31篇 |
1971年 | 36篇 |
1970年 | 29篇 |
1969年 | 34篇 |
排序方式: 共有3479条查询结果,搜索用时 125 毫秒
191.
Muhl Marco Berger Markus Finkbeiner Matthias 《The International Journal of Life Cycle Assessment》2019,24(9):1701-1714
The International Journal of Life Cycle Assessment - Weighting as an optional step in life cycle impact assessment (LCIA) has recently gained momentum through increased policy requirements in the... 相似文献
192.
193.
Patrick T. Rohner Jeannine Roy Martin A. Schfer Wolf U. Blanckenhorn David Berger 《Journal of evolutionary biology》2019,32(5):463-475
Although genetic and plastic responses are sometimes considered as unrelated processes, their phenotypic effects may often align because genetic adaptation is expected to mirror phenotypic plasticity if adaptive, but run counter to it when maladaptive. Because the magnitude and direction of this alignment has further consequences for both the tempo and mode of adaptation, they are relevant for predicting an organisms’ reaction to environmental change. To better understand the interplay between phenotypic plasticity and genetic change in mediating adaptive phenotypic variation to climate variability, we here quantified genetic latitudinal variation and thermal plasticity in wing loading and wing shape in two closely related and widespread sepsid flies. Common garden rearing of 16 geographical populations reared across multiple temperatures revealed that wing loading decreases with latitude in both species. This pattern could be driven by selection for increased dispersal capacity in the cold. However, although allometry, sexual dimorphism, thermal plasticity and latitudinal differentiation in wing shape all show similar patterns in the two species, the relationship between the plastic and genetic responses differed between them. Although latitudinal differentiation (south to north) mirrored thermal plasticity (hot to cold) in Sepsis punctum, there was no relationship in Sepsis fulgens. While this suggests that thermal plasticity may have helped to mediate local adaptation in S. punctum, it also demonstrates that genetic wing shape differentiation and its relation to thermal plasticity may be complex and idiosyncratic, even among ecologically similar and closely related species. Hence, genetic responses can, but do not necessarily, align with phenotypic plasticity induced by changing environmental selection pressures. 相似文献
194.
195.
An early investigation at the Biosphere-2 Laboratory, an artificial ecosystem in the Arizona desert, had shown that the flavonoid content of cacti grown in glass-filtered solar light was lower than of cacti grown in normal solar light. This was attributed to the absence of ultraviolet (UV) radiation, which is required for flavonoid biosynthesis. In this study, two species of Opuntia cacti were grown in solar and UV-depleted light, and their flavonol contents of different tissues were determined by HPLC. O. wilcoxii, previously raised in the absence of UV light, was exposed to normal solar light. The flavonol content of young O. wilcoxii pads was 28-fold higher when grown in solar light as compared to UV-depleted light. The flavonol contents of mature outer tissues were only slightly higher. O. violacea, previously raised in solar light, was also maintained in the same UV-depleted artificial ecosystem. The flavonol content after hydrolysis of outer tissues was similar, whether grown in solar light or UV-depleted light. We attribute these responses to different biosynthetic and metabolic rates of young vs. mature plant tissues; slow-growing mature tissues neither produce nor metabolize compounds as quickly as immature tissues. These findings indicate that artificial ecosystems can influence the production of natural products in cultivated plants. 相似文献
196.
Berger Andreas Valant-Vetschera Karin Schinnerl Johann Brecker Lothar 《Phytochemistry Reviews》2022,21(3):915-939
Phytochemistry Reviews - The species-rich genus Palicourea (Rubiaceae: Palicoureeae) is source of an intriguing diversity of alkaloids derived from tryptamine and its precursor tryptophan. So far... 相似文献
197.
Berger Andreas Valant-Vetschera Karin Schinnerl Johann Brecker Lothar 《Phytochemistry Reviews》2022,21(3):941-986
Phytochemistry Reviews - Tribes Palicoureeae and Psychotrieae (Rubiaceae, Gentianales) are complex and speciose sister groups with a pantropical distribution. Since the initial studies on... 相似文献
198.
199.
200.
Mary S. Pampusch Hadia M. Abdelaal Emily K. Cartwright Jhomary S. Molden Brianna C. Davey Jordan D. Sauve Emily N. Sevcik Aaron K. Rendahl Eva G. Rakasz Elizabeth Connick Edward A. Berger Pamela J. Skinner 《PLoS pathogens》2022,18(2)
During chronic human immunodeficiency virus (HIV) or simian immunodeficiency virus (SIV) infection prior to AIDS progression, the vast majority of viral replication is concentrated within B cell follicles of secondary lymphoid tissues. We investigated whether infusion of T cells expressing an SIV-specific chimeric antigen receptor (CAR) and the follicular homing receptor, CXCR5, could successfully kill viral-RNA+ cells in targeted lymphoid follicles in SIV-infected rhesus macaques. In this study, CD4 and CD8 T cells from rhesus macaques were genetically modified to express antiviral CAR and CXCR5 moieties (generating CAR/CXCR5-T cells) and autologously infused into a chronically infected animal. At 2 days post-treatment, the CAR/CXCR5-T cells were located primarily in spleen and lymph nodes both inside and outside of lymphoid follicles. Few CAR/CXCR5-T cells were detected in the ileum, rectum, and lung, and no cells were detected in the bone marrow, liver, or brain. Within follicles, CAR/CXCR5-T cells were found in direct contact with SIV-viral RNA+ cells. We next infused CAR/CXCR5-T cells into ART-suppressed SIV-infected rhesus macaques, in which the animals were released from ART at the time of infusion. These CAR/CXCR5-T cells replicated in vivo within both the extrafollicular and follicular regions of lymph nodes and accumulated within lymphoid follicles. CAR/CXR5-T cell concentrations in follicles peaked during the first week post-infusion but declined to undetectable levels after 2 to 4 weeks. Overall, CAR/CXCR5-T cell-treated animals maintained lower viral loads and follicular viral RNA levels than untreated control animals, and no outstanding adverse reactions were noted. These findings indicate that CAR/CXCR5-T cell treatment is safe and holds promise as a future treatment for the durable remission of HIV. 相似文献