全文获取类型
收费全文 | 443篇 |
免费 | 30篇 |
专业分类
473篇 |
出版年
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 6篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2015年 | 10篇 |
2014年 | 12篇 |
2013年 | 20篇 |
2012年 | 22篇 |
2011年 | 36篇 |
2010年 | 13篇 |
2009年 | 14篇 |
2008年 | 26篇 |
2007年 | 32篇 |
2006年 | 28篇 |
2005年 | 17篇 |
2004年 | 29篇 |
2003年 | 14篇 |
2002年 | 18篇 |
2001年 | 16篇 |
2000年 | 11篇 |
1999年 | 13篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1995年 | 4篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 6篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 8篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1965年 | 5篇 |
1962年 | 1篇 |
1960年 | 4篇 |
1959年 | 1篇 |
排序方式: 共有473条查询结果,搜索用时 0 毫秒
461.
Fatty acid composition in photosynthetic products of natural phytoplankton population in Lake Biwa, Japan 总被引:1,自引:0,他引:1
Hama Takeo; Matsunaga Katsuji; Handa Nobuhiko; Takahashi Mikio 《Journal of plankton research》1992,14(8):1055-1065
Fatty acid composition of phytoplankton photosynthetic productswas determined by a 13C tracer and gas chromatography-mass spectrometry(13C-GC-MS) method from August 1985 to June 1986 in Lake Biwa,Japan. The total fatty acid production rate varied from 2.8to 10.9 µg C l1 day1 at the water surfaceand accounted for 9.130% of photosynthetic productionof particulate organic carbon. A high contribution of fattyacid to the particulate organic carbon production rate was noticedduring winter time, and an increase in the fatty acid contributionresulted in an increase in the C/N value in the photosyntheticproducts. The fatty acid composition varied throughout the year,mainly depending on the seasonal change in the dominant phytoplanktonspecies. The contribution of polyunsaturated fatty acids tototal fatty acids was low during the summer period, probablydue to nitrogen limitation of phytoplankton growth. 相似文献
462.
Hama Takeo; Matsunaga Katsuji; Handa Nobuhiko; Takahashi Mikio 《Journal of plankton research》1990,12(1):133-147
The seasonal and vertical changes in photosynthetic productswere determined in Lake Biwa, which is the largest lake in Japan,by combined 13C and gas chromatography-mass spectrometry (13C-GC-MS).The temperature dependence of the production rates differedamong organic compounds. The seasonal change in the proteinspecific production rate (SPR) showed a strong temperature dependence,indicating that photoplankton growth rate was primarily governedby water temperature. In August and September, low protein SPRwas, however, observed, probably due to low inorganic nitrogenconcentration. Nitrogen deficiency in the late stagnation periodwas also suggested by high C:N ratios both in paniculate matterand photosynthetic products. The glucose SPR did not show anysignificant correlation with water temperature, irradiance andinorganic nitrogen concentration. Highly variable glucose SPRmight be due to high turnover of glucose, and vertical mixingin the mixed surface layer may be one of the most importantfactors causing variability of glucose SPR. 相似文献
463.
464.
465.
Hama Takeo; Matsunaga Katsuji; Handa Nobuhiko; Takahashi Mikio 《Journal of plankton research》1990,12(1):125-131
The production rate of participate nitrogen (PN) in Lake Biwafrom March to June 1986 was calculated by monthly measurementsof the proteinaceous nitrogen production rates. The newproduction rate was estimated from the decrease in nitrate inthe euphotic zone; during this period (91 days) it was estimatedas 93 mg atoms m2, and accounted for 20% of the totalPN production (460 mg atoms m2). This implies that {smalltilde}80% of the PN produced might be recycled in the euphoticzone. The increase in PN in the euphotic zone during this period(27 mg atoms m2) accounted for 5.9% of the totalPN production. This indicates that the remaining 14% of PN producedin the euphotic zone was vertically transported. Sediment trapexperiments at 30 m depth indicate that 8.1% of the PN producedin the euphotic zone was measured as downward flux at 30 m depthduring the stagnation period. Decompositional loss of PN between12.5 (bottom of the euphotic zone) and 30 m depth was estimatedas 17 mg atoms m2. This was calculated on the basis ofaccumulation of ammonium, which accounted for 3.7% of the totalPN production. The flux from the euphotic zone thus accountedfor 12% of the total PN production, suggestingthe validity of the production model. 相似文献
466.
S Asada Y Kasuya H Hama T Masaki K Goto 《Biochemical and biophysical research communications》1999,260(2):441-445
MBP kinase detection assay revealed that acidic FGF (aFGF) augmented MBP kinase activity in a dose-dependent manner in astrocytes (AC). The molar potency of this action of aFGF in dibutyryl cyclic AMP (DBcAMP)-treated AC was significantly higher than that in quiescent AC. Consistently, the molar potency of accumulation of p21(ras)-GTP by aFGF was significantly higher in DBcAMP-treated AC than in quiescent AC. However, binding study showed that B(max) and K(D) for [(125)I]aFGF in DBcAMP-treated AC were quite similar to those in quiescent AC. Furthermore, the expression levels of Grb2, SOS, and p21(ras) were not changed by treatment of AC with DBcAMP. These results suggest that cytodifferentiation potentiates the p21(ras)/Erk signaling pathway in AC in response to aFGF without changing the expression levels of signaling molecules mediating from the FGF receptor to p21(ras). 相似文献
467.
468.
Naruyuki Maruoka Bunta Watanabe Daigo Ando Masahiro Miyashita Tatsuo Kurihara Hideki Hokazono 《Bioscience, biotechnology, and biochemistry》2020,84(8):1696-1705
ABSTRACT Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by pruritic and eczematous skin lesions. The skin of AD patients is generally in a dried condition. Therefore, it is important for AD patients to manage skin moisturization. In this study, we examined the effects of orally administered fermented barley extract P (FBEP), which is prepared from a supernatant of barley shochu distillery by-product, on stratum corneum (SC) hydration and transepidermal water loss (TEWL) in AD-like lesions induced in hairless mice using 2,4,6-trinitrochlorobenzene. Oral administration of FBEP increased SC hydration and decreased TEWL in the dorsal skin of this mouse model. Further fractionation of FBEP showed that a pyroglutamyl pentapeptide, pEQPFP comprising all -L-form amino acids, is responsible for these activities. These results suggested that this pyroglutamyl pentapeptide may serve as a modality for the treatment of AD. 相似文献
469.
470.
Fatty acid composition of particulate matter and photosynthetic products in subarctic and subtropical Pacific 总被引:3,自引:0,他引:3
The fatty acid composition of lipid materials in particulate matter and
photosynthetic products was determined using 13C gas
chromatography-mass spectrometry methodology in the subarctic and
subtropical Pacific. Polyunsaturated fatty acids (PUFA) were measured as
one of the major constituents of particulate and photosynthetically
produced lipids in the subarctic Pacific. In the subtropical Pacific, on
the other hand, a quite simple fatty acid composition was found, consisting
mainly of saturated fatty acids (SFA) and monounsaturated fatty acids
(MUFA); the production rate of PUFA could not be determined due to the low
concentration in the subtropical area. The relationship between the fatty
acid composition of particulate lipids and photosynthetically produced
lipids indicated that PUFA observed in particulate lipids were mainly
associated with phytoplankton. Non-living lipids, on the other hand, could
be mainly constituted by SFA, due to the lability of PUFA to degradation.
The difference in the contribution of phytoplankton lipids to particulate
lipids is considered as an important factor affecting the difference in the
fatty acid composition of particulate lipids between subarctic and
subtropical Pacific.
相似文献