全文获取类型
收费全文 | 800篇 |
免费 | 47篇 |
国内免费 | 2篇 |
专业分类
849篇 |
出版年
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 15篇 |
2014年 | 11篇 |
2013年 | 24篇 |
2012年 | 27篇 |
2011年 | 35篇 |
2010年 | 47篇 |
2009年 | 47篇 |
2008年 | 37篇 |
2007年 | 47篇 |
2006年 | 45篇 |
2005年 | 36篇 |
2004年 | 22篇 |
2003年 | 28篇 |
2002年 | 22篇 |
2001年 | 22篇 |
2000年 | 20篇 |
1999年 | 20篇 |
1998年 | 22篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 18篇 |
1994年 | 16篇 |
1993年 | 17篇 |
1992年 | 15篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 23篇 |
1988年 | 8篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1970年 | 3篇 |
排序方式: 共有849条查询结果,搜索用时 15 毫秒
91.
The effects of light and temperature on photosynthate partitioning in Antarctic freshwater phytoplankton 总被引:1,自引:0,他引:1
The effects of temperature and radiation flux on the partitioningof photosynthetically fixed carbon into four intracellulai metabolicpools was investigated for natural phytoplankton assemblagesfrom an Antarctic freshwater lake. At ambient temperature, proteinsynthesis was saturated at low photon flux densities (3040µmol m2 s1) and above this flux fixed carbonwas increasingly stored as lipid and polysaccharide. Increasingtemperature raised both the saturated rate of protein synthesisand the photon flux at which saturation occurred. There wasa corresponding decline in the accumulation of reserve products,particularly at low radiation fluxes. The consequences of thispattern of uptake for the phytoplankton is discussed. 相似文献
92.
Wu WL Burnett DA Caplen MA Domalski MS Bennett C Greenlee WJ Hawes BE O'Neill K Weig B Weston D Spar B Kowalski T 《Bioorganic & medicinal chemistry letters》2006,16(14):3674-3678
Biaryl urea lead compound 1 was discovered earlier in our MCH antagonist program. Novel benzimidazole analogues with increased chemical stability, devoid of the potential carcinogenic liability associated with a biarylamine moiety, were synthesized and evaluated to be potent MCH R1 antagonists. Two compounds in this series have demonstrated in vivo efficacy in a rodent obesity model. 相似文献
93.
94.
Kane, I.A. 2010: Turbulence, displacement, death and worms: a day in the life of a fluvial Carboniferous bivalve. Lethaia, Vol. 43, pp. 381–395. In the Pennsylvanian Rough Rock Flags and Rough Rock of northern England trace fossils attributed to the non‐marine bivalve Carbonicola are found. Carbonicola, recorded by Lockeia and associated trace fossils, lived a semi‐infaunal lifestyle and thus were influenced by both the sediment in which they were hosted, and the currents which supplied their nutrients and oxygen. A number of palaeocurrent indictors are commonly associated with Lockeia: (1) downstream inclination of vertical burrows; (2) palaeoflow‐parallel orientation of long axes; (3) steeper scouring and higher sediment surface on the upstream side; and (4) diffuse lamination downstream of the trace or more widespread downstream erosion. Semi‐infaunal, Carbonicola bivalves were partly exposed to the prevailing flow and acted as bed defects; flow separation and acceleration enhanced flow turbulence around the bivalve leading to erosion and the development of a variably developed fan‐shaped zone of scour immediately downstream. Disturbance and destabilization of sediment in this way may have affected bivalves immediately downstream, plausibly explaining the relatively regular spacing pattern of individual or clustered Lockeia, exposed on bedding planes and revealed by nearest neighbour analyses. Bivalves that did not survive high‐energy flow events were either trapped within the sediment, or transported downstream and deposited in lower energy environments within the otherwise high‐energy deposits of the Rough Rock. 相似文献
95.
We have synthesised the -subunit of the chick nicotinic acetylcholine receptor (nAChR) in stable, continuous insect (Spodoptera frugiperda) cell lines. A cDNA was integrated randomly into the insect cell genome under control of a baculovius immediate early gene promoter. Transformed cells were obtained by co-transfection of the insect cells with pIEK1.nAChR, encoding the -subunit cDNA, and pIEK1.neo, encoding the neomycin resistance gene. G-418-resistant clones were selected and expanded into continuous cell lines synthesising the chick nAChR -subunit. Using fluorescence microscopy and ligand binding studies we were able to demonstrate efficient membrane targeting of the receptor subunit in the insect cell plasma membrane. Stable insect cell lines may thus have significant advantages over transient baculovirus vectors for the synthesis and characterisation of heterologous receptor proteins.Abbreviations AcNPV
Autographa californica nuclear polyhedrosis virus
- BTX
-bungarotoxin
- BSA
bovine serum albumin
- FITC
Fluoroscein isothiocyanate
- G418
geneticin-418
- hpi
hours post-infection
-
ie-1
immediate early 1 gene
- nAChR
nicotinic acetylcholine receptor alpha subunit
- Sf
Spodoptera frugiperda
- tPA
tissue plasminogen activator 相似文献
96.
97.
BJØRN RØRSLETT IAN HAWES & ANNE-MAREE SCHWARZ 《The Plant journal : for cell and molecular biology》2004,37(2):441-454
1. Using sampling rates of 8–64 Hz we found clear indications of extensive and high frequency fluctuations of underwater photosynthetically active radiation (PAR) just below the surface (0.016–1.1 m) in some New Zealand water bodies. High variability and flashing occurred down to at least 3 m depth.
2. PAR variability increased under the influence of bright sunshine if wind roughening of the surface took place. Concomitantly, the average PAR levels declined by about 10%. However, even when the surface was shaded, high variability of PAR persisted.
3. Under a calm surface, PAR irradiance followed a log normal distribution. This occurred independently of the presence of direct sunlight. However, when the surface was roughened by wind in sunshine, PAR immediately switched to a Gumbel (extreme value type EV1) distribution.
4. Neither wave action nor wave focusing of incident irradiance would explain the wide range of PAR close to the water surface, although both factors add to the PAR variability.
5. The data indicate that transmittance through the surface is highly variable at the temporal and spatial scales studied, and that the irregularity of the air–water interface is instrumental in bringing about the observed fluctuations of PAR just below the surface. 相似文献
2. PAR variability increased under the influence of bright sunshine if wind roughening of the surface took place. Concomitantly, the average PAR levels declined by about 10%. However, even when the surface was shaded, high variability of PAR persisted.
3. Under a calm surface, PAR irradiance followed a log normal distribution. This occurred independently of the presence of direct sunlight. However, when the surface was roughened by wind in sunshine, PAR immediately switched to a Gumbel (extreme value type EV1) distribution.
4. Neither wave action nor wave focusing of incident irradiance would explain the wide range of PAR close to the water surface, although both factors add to the PAR variability.
5. The data indicate that transmittance through the surface is highly variable at the temporal and spatial scales studied, and that the irregularity of the air–water interface is instrumental in bringing about the observed fluctuations of PAR just below the surface. 相似文献
98.
Alexander JJ Umino Y Everhart D Chang B Min SH Li Q Timmers AM Hawes NL Pang JJ Barlow RB Hauswirth WW 《Nature medicine》2007,13(6):685-687
Loss of cone function in the central retina is a pivotal event in the development of severe vision impairment for many prevalent blinding diseases. Complete achromatopsia is a genetic defect resulting in cone vision loss in 1 in 30,000 individuals. Using adeno-associated virus (AAV) gene therapy, we show that it is possible to target cones and rescue both the cone-mediated electroretinogram response and visual acuity in the Gnat2 ( cpfl3 ) mouse model of achromatopsia. 相似文献
99.
100.