全文获取类型
收费全文 | 818篇 |
免费 | 48篇 |
国内免费 | 4篇 |
出版年
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 20篇 |
2017年 | 14篇 |
2016年 | 22篇 |
2015年 | 38篇 |
2014年 | 31篇 |
2013年 | 40篇 |
2012年 | 54篇 |
2011年 | 47篇 |
2010年 | 26篇 |
2009年 | 23篇 |
2008年 | 35篇 |
2007年 | 36篇 |
2006年 | 37篇 |
2005年 | 37篇 |
2004年 | 43篇 |
2003年 | 33篇 |
2002年 | 38篇 |
2001年 | 21篇 |
2000年 | 8篇 |
1999年 | 12篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 13篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1973年 | 10篇 |
1972年 | 5篇 |
1971年 | 7篇 |
1970年 | 8篇 |
1969年 | 8篇 |
1968年 | 4篇 |
1967年 | 7篇 |
1966年 | 7篇 |
1887年 | 4篇 |
排序方式: 共有870条查询结果,搜索用时 811 毫秒
101.
102.
Breakage of human chromosomes was studied in vitro by treating leukocyte cultures for 8 hours with tretamine, tepa, hempa, hemel, and apholate. The aziridines tretamine, tepa, and apholate effectively induced aberrations; the dimethylamino compounds, hemel and hempa, induced few. Tretamine, the most effective compound, induced aberrations in 78% of the cells; hempa, the least effective, induced aberrations in 14%, even at a 1000-fold greater molar concentration. Abberations occurred in 6% of control cells. The gaps and breaks were induced randomly among cells. 相似文献
103.
Waldemar G. Johanson Jr. Marina G. Kennedy Frederick J. Bonte 《Applied microbiology》1973,25(4):592-594
The suitability of technetium (99mTc), a gamma emitter, for labeling of Diplococcus pneumoniae in studies of lung bacterial clearance was examined. A killed bacterial slurry with high specific activity was obtained with a ferric ascorbate reducing system. Approximately 5.5% of radioactive counts dissociated from labeled bacteria in 6 h. Rats were exposed to a uniformly mixed aerosol of untagged, viable pneumococci and killed, 99mTc-tagged pneumococci. The aerodynamic behavior of labeled and unlabeled pneumococci was similar. Viable bacterial counts and radioactive counts were determined in lung homogenates at intervals following exposure, and rates of bacterial killing and disappearance of radioactive counts were plotted. Radioactive counts did not increase in the liver during the period of observation, suggesting that the decrease in lung radioactivity represents mucociliary clearance and not release of isotope to the systemic circulation. The use of 99mTc for bacterial labeling provides advantages of technical simplicity and personnel safety compared to the use of beta-emitting isotopes. 相似文献
104.
105.
Kaja Wierucka Sonia Siemianowska Marta Woźniak Katarzyna Jasnosz Magdalena Kieliszczyk Paulina Kozak 《Journal of applied animal welfare science : JAAWS》2016,19(1):62-72
Ethograms and time budgets are crucial for the behavioral assessment of nonhuman animals in zoos, and they serve as references for welfare research. This study was conducted to obtain detailed time budgets of trained Cape fur seals (Arctocephalus pusillus) in captivity, to evaluate variations of these patterns, and to determine whether abnormal behaviors had been displayed. Behavioral data for 3 Cape fur seals in the Wroclaw Zoo were collected, and more than 300 observation hours (during a 12-month period) per individual were analyzed. The studied animals exhibited a diversified repertoire of natural behaviors with apparent seasonal and daily patterns, and they did not present stereotypic behaviors. Significant differences of interaction rates between individuals suggest more frequent affiliative interactions among related animals. The absence of stereotypic behaviors, good health of individuals, and the presence of diversified natural behaviors indicated relatively good welfare of Cape fur seals kept in the Wroclaw Zoo. 相似文献
106.
107.
Ute Hoch Hans-Ulrich Humpf Peter Schreier Chantu R. Saha-Mller Waldemar Adam 《Chirality》1997,9(1):69-74
Allylic hydroperoxides are a class of compounds of versatile synthetic utility. Optically active diastereomeric hydroperoxy homoallylic alcohols and their corresponding diols are easily available through horseradish peroxidase (HRP)-catalyzed kinetic resolution of racemic hydroperoxides. Here we describe the assignment of the absolute configuration of the optically active products and substrates obtained after HRP-catalysis by the circular dichroism exciton chirality method. Moreover, the analytical-scale separation of the enantiomers based on multidimensional gas chromatography on chiral columns is presented. Since the enantiomeric elution order on the ciral columns was constituted, the absolute stereochemistry of optically active allylic diols can easily be deduced by their retention times on β-cyclodextrins. Chirality 9:69–74, 1997. © 1997 Wiley-Liss, Inc. 相似文献
108.
Monika Rakoczy-Trojanowska Paweł Krajewski Jan Bocianowski Małgorzata Schollenberger Wojciech Wakuliński Paweł Milczarski Piotr Masojć Małgorzata Targońska-Karasek Zofia Banaszak Katarzyna Banaszak Waldemar Brukwiński Wacław Orczyk Andrzej Kilian 《Plant Molecular Biology Reporter》2017,35(3):366-378
Rye is a crop with relatively high resistance to biotic and abiotic stresses. However, the resistance to brown rust (Puccinia recondita f. sp. secalis) and pre-harvest sprouting are still not satisfactory. High α-amylase activity is also among the main disadvantages of this species. Therefore, effective tools, e.g. molecular markers, allowing precise and environmentally independent selection of favourable alleles are desirable. In the present study, two kinds of association mapping—genome-wide association mapping (GWAM) based on sequences of DArTSeq markers and candidate gene association mapping (CGAM) based on sequences of ScBx genes—were chosen for development of molecular markers fulfilling these criteria. The analysed population consisted of 149 diverse inbred lines (DILs). Altogether, 67 and 11 single nucleotide polymorphisms (SNPs) identified in, respectively, GWAM and CGAM, were significantly associated with the investigated traits: 2 SNPs with resistance to brown rust, 71 SNPs with resistance to pre-harvest sprouting and 5 SNPs with α-amylase activity in the grain. Fifteen SNPs were stable across all environments. The highest number (13) of environmentally stable SNPs was associated with pre-harvest sprouting resistance. The test employing the Kompetitive Allele Specific PCR method proved the versatility of four markers identified in both GWAM and CGAM. 相似文献
109.
Microstructure and nanomechanical properties of single stalks from diatom Didymosphenia geminata and their change due to adsorption of selected metal ions
下载免费PDF全文
![点击此处可从《Journal of phycology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Izabela Zgłobicka Adrian Chlanda Michał Woźniak Maciej Łojkowski Robert Szoszkiewicz Marta Mazurkiewicz‐Pawlicka Wojciech Święszkowski Elżbieta Wyroba Krzysztof J. Kurzydłowski 《Journal of phycology》2017,53(4):880-888
We present topographical and nanomechanical characterization of single Didymosphenia geminata stalk. We compared the samples before and after adsorption of metal ions from freshwater samples. Transmission electron microscopy studies of single stalk cross‐sections have shown three distinct layers and an additional thin extra coat on the external layer (called “EL”). Using scanning electron microscopy and atomic force microscopy (AFM), we found that topography of single stalks after ionic adsorption differed significantly from topography of pristine stalks. AFM nanoindentation studies in ambient conditions yielded elastic moduli of 214 ± 170 MPa for pristine stalks and 294 ± 108 MPa for stalks after ionic adsorption. Statistical tests showed that those results were significantly different. We conducted only preliminary comparisons between ionic adsorption of several stalks in air and in water. While the stalks with ions were on average stiffer than the pristine stalks in air, they became more compliant than the pristine stalks in water. We also heated the stalks and detected EL softening at 50°C ± 15°C. AFM nanoindentation in air on the softened samples yielded elastic moduli of 26 ± 9 MPa for pristine samples and 43 ± 22 MPa for stalks with absorbed metal ions. Substantial decrease of the EL elastic moduli after heating was expected. Significantly different elastic moduli for the samples after ionic adsorption in both cases (i.e., for heated and nonheated samples), as well as behavior of the stalks immersed in water, point to permanent structural EL changes due to ions. 相似文献
110.
Ewa Langner Marta K. Lemieszek Jacek M. Kwiecień Grażyna Rajtar Wojciech Rzeski Waldemar A. Turski 《Neurochemical research》2017,42(3):838-845
Kynurenic acid (KYNA) is an end stage product of tryptophan metabolism with a variety of functions in the human body, both in the central nervous system (CNS) and in other organs. Although its activity in the human brain has been widely studied and effects on neural cells were emphasized, the effect of KYNA on oligodendroglial cells remains unknown. Present study aims at describing the activity of high concentration of KYNA in OLN-93 cells. The inhibition of OLN-93 oligodendrocytes viability by KYNA in a medium with reduced serum concentration has been demonstrated. Although decreased metabolic activity of KYNA treated OLN-93 cells was shown, the cells proliferation was not altered. KYNA treatment did not alter morphology as well as expression level of cell cycle and proliferation regulating proteins. Furthermore, glutamate receptor antagonists and agonists did not alter the inhibitory effect of KYNA on viability of OLN-93 oligodendrocytes. This study contributes to the elucidation of effects of KYNA on oligodendrocytes in vitro, yet further analyses are necessary to explain the mechanisms behind the damage and loss of myelin sheaths. 相似文献