全文获取类型
收费全文 | 716篇 |
免费 | 127篇 |
专业分类
843篇 |
出版年
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2016年 | 6篇 |
2015年 | 10篇 |
2014年 | 19篇 |
2013年 | 21篇 |
2012年 | 24篇 |
2011年 | 31篇 |
2010年 | 17篇 |
2009年 | 18篇 |
2008年 | 28篇 |
2007年 | 19篇 |
2006年 | 16篇 |
2005年 | 15篇 |
2004年 | 17篇 |
2003年 | 29篇 |
2002年 | 22篇 |
2001年 | 32篇 |
2000年 | 34篇 |
1999年 | 27篇 |
1998年 | 19篇 |
1997年 | 12篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 14篇 |
1992年 | 14篇 |
1991年 | 23篇 |
1990年 | 17篇 |
1989年 | 31篇 |
1988年 | 21篇 |
1987年 | 19篇 |
1986年 | 16篇 |
1985年 | 22篇 |
1984年 | 24篇 |
1983年 | 16篇 |
1982年 | 19篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 18篇 |
1978年 | 14篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1975年 | 13篇 |
1974年 | 19篇 |
1973年 | 9篇 |
1972年 | 6篇 |
1971年 | 3篇 |
1968年 | 7篇 |
排序方式: 共有843条查询结果,搜索用时 15 毫秒
151.
152.
Sune Pettersson 《Physiologia plantarum》1981,52(4):431-436
Passive fluxes of K+ (86 Rb) into roots of sunflower ( Helianthus annuus L. cv. Uniflorus) were determined at low K+ concentration (0.1 and 1.0 mM K+ ) in the ambient solution. Metabolic uptake of K+ was inhibited by 10−4 M 2,4-dinitrophenol (DNP). K+ (86 Rb) fluxes were studied both continuously and by time differentiation of uptake. In high K+ roots passive uptake was directly proportional to the K+ concentration of the uptake solution, indicating free diffusion. This assumption was supported by the fact that passive Rb+ uptake was not affected by high K+ concentrations. In low K+ roots the passive uptake of K+ was higher than in high K+ roots. The increase was possibly due to carrier-mediated K+ transport. As K+ effluxes were quantitatively similar to influxes, it is suggested that passive K+ fluxes represent exchange diffusion without relation to net K+ transport. 相似文献
153.
A. Parich H. Pettersson R. D. Josephs H. P. van Egmond R. Schothorst P. Brereton D. Chan R. Krska 《Mycotoxin Research》2005,21(1):7-10
Within an EC-funded project calibrants with certified concentrations of Deoxynivalenol (DON), 3-Acetyl-Deoxynivalenol (3-Ac-DON),
15-Acetyl-Deoxynivalenol (15-Ac-DON) and Nivalenol (NIV) in acetonitrile have been produced. So far the project has led to
improved isolation and purification of the solid toxins fromFusarium cultures. In addition, conditions for the production, ampouling and transport of the toxin solutions have been optimised.
Further investigations should lead to knowledge about storage conditions and internationally accepted molar absorption coefficients
for DON, 3-Ac-DON, 15-Ac-DON and NIV in acetonitrile. The intercomparison study which is currently carried out will also help
to support knowledge and experience exchange between laboratories in the field ofFusarium mycotoxin analysis. 相似文献
154.
Ing-Marie Viklund Pontus Aspenström Vannary Meas-Yedid Jolanta Kopec Daniel Ågren Gunter Schneider Mauro D'Amato Jean-Christophe Olivo-Marin Guy Tran Van Nhieu Sven Pettersson 《Experimental cell research》2009,315(6):1040-220
We have previously identified a new gene with sequence homology to the WASP-family of actin regulators denoted WAFL (WASP and FKBP-like). Here we report a possible biological function for WAFL, by demonstrating an association to early endosomes via its central coiled-coil domain. Further we show by functional and structural studies that WAFL is associated with both microtubules and the actin filament system, the two means of transport of early endosomes. In addition, WAFL interacts with WASP-interacting protein (WIP) and actin, thus linking WAFL to actin dynamics. The use of RNAi depletion of WAFL shows that WAFL-deficient cells display delayed transport of endosomal cargo. Our findings are compatible with a model whereby WAFL is involved in the transport of early endosomes at the level of transition between microfilament-based and microtubule-based movement. 相似文献
155.
Creation of new genes and functions is a central feature of evolution. Duplication of existing genes has long been assumed
to be the source of new genes, but the precise mechanism has remained unclear. One suggestion is that new genes are created
via temporary amplifications, which simultaneously increase both the selective advantage of weak, pre-existing secondary functions
and the target for optimizing mutations. This paper examines the amplification model by formalizing it into a mathematical
framework. This framework is used to perform stochastic (Monte Carlo) simulations. In addition, experimental data from Salmonella typhimurium LT2 are used to support the modelling, by providing estimates for parameter values. The results show that amplification of
tandem repeats is likely to contribute to creation of new genes in nature. 相似文献
156.
Alexander E. Kissler Nina Pettersson Andreas Frölich Stephan J. Sigrist Beat Suter 《Developmental neurobiology》2009,69(6):365-377
Cyclin‐dependent kinase 5 (Cdk5) functions in postmitotic neuronal cells and play roles in cell differentiation, cell migration, axonal guidance, and synaptic function. Here, we demonstrate that Drosophila cdk5 is dispensable for adult viability and fertility, a feature that allows us to study its physiological function in the whole animal model. For the adult, cdk5 is needed for proper locomotion and flight performance. Larvae lacking cdk5 in the presynaptic tissue display abnormal crawling motion, and their neuromuscular junctions (NMJ) are elongated and contain a higher number of boutons that are smaller. As a result of these two counteracting effects, the total synaptic area/NMJ is similar to wild type, leading to normal synaptic transmission, indicating that a compensatory mechanism is capable of correcting the problem caused by the lack of cdk5. futsch, the Drosophila MAP1B homolog, is also involved in NMJ morphogenesis, and analysis of the NMJ phenotype of the double mutant futschK68; cdk5? indicates that cdk5 is epistatic to futsch in this process. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 相似文献
157.
You Fu Pan Ing-Marie Viklund Heng Hang Tsai Sven Pettersson Ichiro N. Maruyama 《International journal of biological sciences》2010,6(2):163-171
Ulcerative colitis (UC) is one of the major forms of inflammatory bowel disease with unknown cause. A molecular marker, WAFL, has recently been found to be up-regulated in the inflamed colonic mucosa of UC patients. Towards understanding biological function of WAFL, we analyzed proteins interacting with WAFL in HEK-293 cells by immunoprecipitation and mass spectrometry. Among four proteins found to specifically interact with WAFL, both KIAA0196 and KIAA1033 bind to α-appendage of the adaptor protein complex 2 (AP2), which acts as an interaction hub for accessory proteins in endocytosis mediated by clathrin-coated vesicle (CCV). The specific interaction between WAFL and KIAA0196 was also confirmed in human colorectal carcinoma HCT-116 cells by co-immunoprecipitation with specific antibodies. Meta-analyses of the databases of expressed genes suggest that the three genes are co-expressed in many tissues and cell types, and that their molecular function may be classified in the category of ''membrane traffic protein''. Therefore, these results suggest that WAFL may play an important role in endocytosis and subsequent membrane trafficking by interacting with AP2 through KIAA0196 and KIAA1033. 相似文献
158.
159.
Root dynamics in a semi-natural grassland in relation to atmospheric carbon dioxide enrichment,soil water and shoot biomass 总被引:1,自引:0,他引:1
Sindhøj Erik Hansson Ann-Charlotte Andrén Olof Kätterer Thomas Marissink Mark Pettersson Roger 《Plant and Soil》2000,223(1-2):255-265
Plant responses to increasing atmospheric CO2 concentrations have been studied intensively. However, the effects of elevated CO2 on root dynamics, which is important for global carbon budgets as well as for nutrient cycling in ecosystems, has received
much less attention. We used minirhizotrons inside open-top chambers to study the effects of elevated atmospheric carbon dioxide
concentration on root dynamics in a nutrient-poor semi-natural grassland in central Sweden. We conducted our investigation
over three consecutive growing seasons during which three treatments were applied at the site: Elevated (≈ 700 μmol mol-1) and ambient (≈ 360 μmol mol-1) chamber levels of CO2 and a control, without a chamber. During 1997, a summer with two dry periods, the elevated treatment compared with ambient
had 25% greater mean root counts, 65% greater above-ground biomass and 15% greater soil moisture. The chambers seemed responsible
for changes in root dynamics, whereas the elevated CO2 treatment in general increased the absolute sum of root counts compared with the ambient chamber. In 1998, a wet growing
season, there were no significant differences in shoot biomass or root dynamics and both chamber treatments had lower soil
moisture than the control. We found that as seasonal dryness increased, the ratio of elevated – ambient shoot biomass production
increased while the root to shoot ratio decreased. We conclude that this grasslands response to elevated CO2 is dependent on seasonal weather conditions and that CO2 enrichment will most significantly increase production in such a grassland when under water stress.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
160.
Javier Martnez Jan Henriksson Maria Ridåker Ulf Pettersson Juan José Cazzulo 《FEMS microbiology letters》1998,159(1):35-39
Forty-eight cDNA clones obtained from different developmental stages of Trypanosoma cruzi and all encoding the C-terminal domain of the major cysteine proteinase (cruzipain) have been sequenced. A number of polymorphisms were detected, seven of them resulting in amino acid replacements. The predicted pI values of the corresponding gene products varied between 7.05 and 8.12. These changes in amino acid sequence, together with previously reported variations in carbohydrate composition at the only N-glycosylation site in the C-terminal domain, may account for most of the heterogeneities found in the mature enzyme. 相似文献