全文获取类型
收费全文 | 2658篇 |
免费 | 344篇 |
国内免费 | 268篇 |
出版年
2024年 | 4篇 |
2023年 | 69篇 |
2022年 | 63篇 |
2021年 | 119篇 |
2020年 | 128篇 |
2019年 | 161篇 |
2018年 | 131篇 |
2017年 | 97篇 |
2016年 | 98篇 |
2015年 | 125篇 |
2014年 | 188篇 |
2013年 | 190篇 |
2012年 | 153篇 |
2011年 | 142篇 |
2010年 | 102篇 |
2009年 | 122篇 |
2008年 | 125篇 |
2007年 | 109篇 |
2006年 | 108篇 |
2005年 | 93篇 |
2004年 | 87篇 |
2003年 | 73篇 |
2002年 | 54篇 |
2001年 | 46篇 |
2000年 | 52篇 |
1999年 | 51篇 |
1998年 | 47篇 |
1997年 | 44篇 |
1996年 | 33篇 |
1995年 | 55篇 |
1994年 | 41篇 |
1993年 | 29篇 |
1992年 | 35篇 |
1991年 | 33篇 |
1990年 | 21篇 |
1989年 | 24篇 |
1988年 | 37篇 |
1987年 | 21篇 |
1986年 | 23篇 |
1985年 | 32篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 20篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有3270条查询结果,搜索用时 31 毫秒
1.
The equine leucocyte antigen (ELA) types and the clinical diagnosis for equine sarcoid and summer dermatitis were evaluated in 2026 horses representing five breeds. Data were analysed in unrelated animals and in family material. In the case of equine sarcoid, a strong association was observed between the ELA class II DW13 antigen and its effect on Swiss (cP < 0·001), French (cP < 0·0001) and Irish (cP < 0·01) Warmblood horses. The class I antigen A3 occurred more frequently in sarcoid-affected French horses (cP < 0·001). These results confirm our earlier findings (Gerber et al. 1988). Among Freiberger horses, which lack the ELA DW13 and A3 specificities, a breed-specific class I antigen, ABe108, displayed an increased frequency (cP < 0·05) in the affected group. Among Arabian horses, a tendency for increased frequency of the A1 antigen was observed in the affected animals, but the number of affected horses is too small for statistical significance. The Mendelian segregation in diseased half-siblings by ELA DW13 heterozygous stallions showed a strong association (P < 0·0001) between the inherited DW13 antigen and susceptibility to the sarcoid effect. In the case of summer dermatitis, previously published data (Marti et al. 1992) have been extended. The ELA types in four multiple-case families, founded by the same stallion, were analysed for an association with the effect of sarcoid. Eight out of nine ELA-typed affected offspring inherited the paternal haplotype A15, DW23 in contrast to nonaffected offspring where three out of 12 displayed these antigens (P < 0·005). Moreover, the ELA haplotypes of 11 out of 12 informative affected half-siblings sired by another stallion inherited the paternal haplotype A3, W12, DW23 (P < 0·05). Our findings demonstrate statistically significant associations between certain ELA antigens and two equine diseases. It is still unknown if the major histocompatibility complex (MHC) molecules themselves or another linked gene(s) play a role in the pathogenesis of these conditions. 相似文献
2.
Investigating structure and temporal scale in social organizations using identified individuals 总被引:7,自引:1,他引:6
Studies of individually identified animals can produce substantialdata sets containing information on the structure and temporalscale of social organizations. However, methods of analyzingsuch data are not well established. Important features of asocial organization are revealed by plotting the rate of persistenceof the associations between pairs of individuals over a rangeof time lags (lagged association rate). The consistency of long-termrelationships can be characterized using the rate of associationof pairs of individuals between their first and last observedassociations (intermediate association rate). A hierarchicalseries of models featuring exponentially decaying lagged associationrates may be fitted to these data. This technique retrievedthe essential parameters of five simulated social organizationsand, when used on real data, portrayed the essential featuresof the patterns of temporal change in relationships betweenanimals. The method should be especially useful for analyzingfissionfusion societies containing 1010, 000 individuallyidentifiable animals. 相似文献
3.
Hamzeh A. Lafi Luma Al-Banna Monther T. Sadder Hussein M. Migdadi 《Saudi Journal of Biological Sciences》2016,23(1):108-114
Phenotypic diversity of five Jordanian populations of cyst nematodes, Heterodera spp. collected from five regions from Jordan (Ar-Ramtha, Madaba, Dana, Al-Karak, and Jerash) was investigated. Soil samples were collected from one representative field in each region. Morphological and morphometrical characteristics revealed that Heterodera latipons is dominated in cereal fields at Ar-Ramtha, Madaba, Dana and Al-Karak regions and Heterodera schachtii in Jerash. Cysts populations from all cereal fields had bifenestrate vulval cone and a strong underbridge. Wherever, cysts of the cabbage population had ambifenestrate vulval cone with long vulval slit. The bullae were absent in Ar-Ramtha, Madaba and Dana populations, but present in Al-Karak and Jerash. Based on 12 morphometrical characters, the first three functions in canonical discriminant analysis accounted 99.3% of the total variation. Distance from dorsal gland duct opening to stylet base, underbridge length, a = L/W (body length/midbody width) and length of hyaline tail tip had strong and significant contributions in the first function. While the second function was strongly influenced by length of hyaline tail, fenestral length, fenestral width and tail length. However, the third canonical discriminate function was found to be influenced by stylet length, fenestral length, a = L/W (body length/midbody width) and underbridge width. The graphical representation of the distribution of the samples showed that the first canonical discriminant function clearly separated H. schachtii from Jerash from other populations. Whereas, H. latipons collected from Madaba and Dana were clearly separated in the second function. The results indicated that differences at morphological and morphometrical levels revealed diverse populations of Heterodera spp. in Jordan. 相似文献
4.
Tams Kszegi 《Luminescence》1991,6(3):153-157
We have previously shown that the protein binding of intracellular ATP could be examined by monitoring the ATP release kinetics from Triton X-100 and Brij 58 nonionic detergent permeabilized cells. We have now analysed the protein binding of ATP in an isotonic medium using intact and partially ATP depleted Brij 58 treated human erythrocytes. The effects of Triton X-100 below the critical micelle concentration (CMC) was studied in normal and tumorous tissue culture cells and human red blood cells. Our results showed that the protein association of ATP was altered in the partially ATP depleted erythrocytes. Below the CMC value, but above a critical level Triton X-100 treatment was effective in mobilizing the intracellular ATP in both cell types. The ATP release curves were sigmoidal and an ‘all or none’ type of response was observed, especially in erythrocytes. The use of Triton X-100 (< CMC) delays the detergent-induced cell decomposition time thus providing a new approach to investigating the physical state of intracellular ATP. 相似文献
5.
《Current biology : CB》2020,30(12):2260-2274.e6
6.
Understanding the mechanisms of resilience of coral reefs to anthropogenic stressors is a critical step toward mitigating their current global decline. Coral–bacteria associations are fundamental to reef health and disease, but direct observations of these interactions remain largely unexplored. Here, we use novel technology, high-speed laser scanning confocal microscopy on live coral (Pocillopora damicornis), to test the hypothesis that corals exert control over the abundance of their associated bacterial communities by releasing (‘shedding'') bacteria from their surface, and that this mechanism can counteract bacterial growth stimulated by organic inputs. We also test the hypothesis that the coral pathogen Vibrio coralliilyticus can evade such a defense mechanism. This first report of direct observation with high-speed confocal microscopy of living coral and its associated bacterial community revealed a layer (3.3–146.8 μm thick) on the coral surface where bacteria were concentrated. The results of two independent experiments showed that the bacterial abundance in this layer was not sensitive to enrichment (5 mg l−1 peptone), and that coral fragments exposed to enrichment released significantly more bacteria from their surfaces than control corals (P<0.01; 35.9±1.4 × 105 cells cm−2 coral versus 1.3±0.5 × 105 cells cm−2 coral). Our results provide direct support to the hypothesis that shedding bacteria may be an important mechanism by which coral-associated bacterial abundances are regulated under organic matter stress. Additionally, the novel ability to watch this ecological behavior in real-time at the microscale opens an unexplored avenue for mechanistic studies of coral–microbe interactions. 相似文献
7.
Nicotiana
tabacum shows unilateral pollen-pistil incongruity with N. rustica. If N. tabacum is pollinated with N. rustica, growth of the pollen tube is arrested in the middle of the style, and abundant callose deposition, tube swelling and tube
winding are observed. An attempt was made to clarify the genomic factors responsible for this pollen-pistil incongruity. N. tabacum was pollinated with N. paniculata or N. undulata, progenitors of amphidiploid N. rustica. When pollinated with N. undulata, growth of the pollen tube was arrested in the middle of the style and showed abnormal morphology similar to that with N. rustica, but when pollinated with N. paniculata the pollen tube reached near the base of the style and was almost normal in appearance. These observations suggest that the
factors responsible for the pollen tube abnormality of N. rustica are derived from the N. undulata genome.We also used N. sylvestris, N. glutinosa and N. otophora as pistilar parents and N. rustica or its progenitors as pollen parents to examine the genomic factors of the pistilate parents. The pollen tube features of
these three species in the pistils of N. sylvestris were similar to those in the pistil of N. tabacum.
Received: 25 October 1999 / Revision accepted: 2 February 2000 相似文献
8.
N. Cuñado J. L. Santos 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(6):1080-1086
Chromosomal pairing of the three diploid hybrids Aegilops uniaristata × Ae. tauschii (ND), Ae. umbellulata × Ae. tauschii (UD) and Ae. comosa × Ae. uniaristata (MN), and a triploid hybrid Ae. cylindrica × Ae. caudata (DCC), was analyzed by electron microscopy in surface-spread-prophase-I nuclei and compared with light-microscopic observations
of metaphase-I cells after C-banding and fluorescence in situhybridization. All hybrids showed extensive synapsis and complex
multivalents in which up to 14 chromosomes were involved. In the diploid hybrids most metaphase-I chromosomal associations
were between homoeologs, their frequencies being dependent on the relationship between the donor genomes. Despite the different
overall bound-arm frequencies displayed by ND and MN hybrids at metaphase-I, chromosomes bearing rDNA sequences showed similar
mean cell chromosomal association frequencies. In the triploid hybrid preferential associations involving C genomes were predominant.
These observations are discussed in relation to the mechanism of diploidization showed by allotetraploid Aegilops species.
Received: 13 January 1999 / Accepted: 12 March 1999 相似文献
9.
Syunro Utida 《Population Ecology》1952,1(1):166-172
Contributions from the Entomological Laboratory, Kyoto University, No. 110. 相似文献
10.
X. Y. Li C. M. Han Y. Wang H. Z. Liu Z. F. Wu Q. H. Gao S. H. Zhao 《Animal genetics》2010,41(5):537-540
RIG-1 signalling is responsible for the detection of cytoplasmic viral RNA molecules. DEXH (Asp-Glu-X-His) box polypeptide 58 (encoded by DHX58) is a negative regulator of the RIG-1 signalling pathway. In human, the DHX58 gene can be upregulated and can inhibit the RIG-1 signalling pathway during viral infection. In this study, porcine DHX58 gene expression patterns were studied. According to our results, the porcine DHX58 gene was upregulated not only by the stimulation of Poly I:C but also by the stimulation of 1ipopolysaccharides (LPS). One polymorphism (g.4919G>C), detected in the ninth intron, was significantly associated with some blood parameters including the red cell distribution width of 1-day-old pigs and white blood cell counts, lymphocyte absolute counts, and platelet distribution width of 17-day-old pigs (P < 0.05). Moreover, the individuals with the genotype GG have a significantly higher mean white blood cell count than individuals with genotype CC or GC (P < 0.05). Our study indicates that DHX58 is an important gene that is associated with the immune response in swine. 相似文献