全文获取类型
收费全文 | 9020篇 |
免费 | 727篇 |
国内免费 | 255篇 |
出版年
2023年 | 59篇 |
2022年 | 82篇 |
2021年 | 275篇 |
2020年 | 182篇 |
2019年 | 228篇 |
2018年 | 295篇 |
2017年 | 203篇 |
2016年 | 307篇 |
2015年 | 469篇 |
2014年 | 565篇 |
2013年 | 635篇 |
2012年 | 761篇 |
2011年 | 684篇 |
2010年 | 403篇 |
2009年 | 370篇 |
2008年 | 479篇 |
2007年 | 389篇 |
2006年 | 417篇 |
2005年 | 328篇 |
2004年 | 315篇 |
2003年 | 318篇 |
2002年 | 292篇 |
2001年 | 180篇 |
2000年 | 189篇 |
1999年 | 172篇 |
1998年 | 80篇 |
1997年 | 73篇 |
1996年 | 62篇 |
1995年 | 64篇 |
1994年 | 63篇 |
1993年 | 53篇 |
1992年 | 92篇 |
1991年 | 82篇 |
1990年 | 76篇 |
1989年 | 63篇 |
1988年 | 47篇 |
1987年 | 49篇 |
1986年 | 40篇 |
1985年 | 34篇 |
1984年 | 41篇 |
1983年 | 33篇 |
1982年 | 23篇 |
1980年 | 26篇 |
1979年 | 31篇 |
1978年 | 26篇 |
1977年 | 26篇 |
1975年 | 39篇 |
1974年 | 33篇 |
1973年 | 37篇 |
1972年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Genome‐wide detection of CNVs associated with beak deformity in chickens using high‐density 600K SNP arrays 下载免费PDF全文
H. Bai Y. Sun N. Liu Y. Liu F. Xue Y. Li S. Xu A. Ni J. Ye Y. Chen J. Chen 《Animal genetics》2018,49(3):226-236
Beak deformity (crossed beaks) is found in several indigenous chicken breeds including Beijing‐You studied here. Birds with deformed beaks have reduced feed intake and poor production performance. Recently, copy number variation (CNV) has been examined in many species and is recognized as a source of genetic variation, especially for disease phenotypes. In this study, to unravel the genetic mechanisms underlying beak deformity, we performed genome‐wide CNV detection using Affymetrix chicken high‐density 600K data on 48 deformed‐beak and 48 normal birds using penncnv . As a result, two and eight CNV regions (CNVRs) covering 0.32 and 2.45 Mb respectively on autosomes were identified in deformed‐beak and normal birds respectively. Further RT‐qPCR studies validated nine of the 10 CNVRs. The ratios of six CNVRs were significantly different between deformed‐beak and normal birds (P < 0.01). Within these six regions, three and 21 known genes were identified in deformed‐beak and normal birds respectively. Bioinformatics analysis showed that these genes were enriched in six GO terms and one KEGG pathway. Five candidate genes in the CNVRs were further validated using RT‐qPCR. The expression of LRIG2 (leucine rich repeats and immunoglobulin like domains 2) was lower in birds with deformed beaks (P < 0.01). Therefore, the LRIG2 gene could be considered a key factor in view of its known functions and its potential roles in beak deformity. Overall, our results will be helpful for future investigations of the genomic structural variations underlying beak deformity in chickens. 相似文献
12.
Modelling species distributions has been widely used to understand present and future potential distributions of species, and can provide adaptation and mitigation information as references for conservation and management under climate change. However, various methods of data splitting to develop and validate functions of the models do not get enough attention, which may mislead the interpretation of predicted results. We used the Taiwanese endemic birds to test the influences of temporal independence of datasets on model performance and prediction. Training and testing data were considered to be independent if they were collected during different survey periods (1993–2004 and 2009–2010). The results indicated no significant differences of six model performance measures (AUC, kappa, TSS, accuracy, sensitivity, and specificity) among the combinations of training and testing datasets. Both species- and grid cell-based assessments differed significantly between predictions by the annual and pooled training data. We also found an average of 85.8% similarity for species presences and absences in different survey periods. The remaining dissimilarity was mostly caused by species observed in the late survey period but not in the early one. The method of data splitting, yielding training and testing data, is critical for resulting model species distributions. Even if similar model performance exists, different methods can lead to different species distributional maps. More attention needs to be given to this issue, especially when amplifying these models to project species distributions in a changing world. 相似文献
13.
In the present study, we addressed the question of whether treatment with mannitol, an osmotic diuretic, affects astrogliovascular responses to status epilepticus (SE). In saline-treated animals, astrocytes exhibited reactive astrogliosis in the CA1-3 regions 2-4 days after SE. In the mannitol-treated animals, a large astroglial empty zone was observed in the CA1 region 2 days after SE. This astroglial loss was unrelated to vasogenic edema formation. There was no difference in SE-induced neuronal loss between saline- and mannitol-treated animals. Furthermore, mannitol treatment did not affect astroglial loss and vasogenic edema formation in the dentate gyrus and the piriform cortex. These findings suggest that mannitol treatment induces selective astroglial loss in the CA1 region independent of vasogenic edema formation following SE. These findings support the hypothesis that the susceptibility of astrocytes to SE is most likely due to the distinctive heterogeneity of astrocytes independent of hemodynamics. [BMB Reports 2015; 48(9): 507-512] 相似文献
14.
Shi Fenghua Tan Muxiu Mo Qiaocheng Chen Xiaoying Zhao Yimin Guo Xiaoyun Jiang Ni 《Journal of plant biochemistry and biotechnology.》2020,29(3):528-538
Journal of Plant Biochemistry and Biotechnology - The dried buds of Lonicera hypoglauca Miq. have antipyretic, antidotal and anti-inflammatory properties and as Flos lonicerae are widely used in... 相似文献
15.
Two new beta-xylosyl derivatives of ginsenoside Re, 20(S)-protopanaxatriol 6-O-alpha-L-rhamnopyranosyl-(1 --> 2)-[beta-D-xylopyranosyl-(1 --> 4)]-beta-D-glucopyranosyl-20-O-beta-D-glucopyranoside and 20(S)-protopanaxatriol 6-O-alpha-L-rhamnopyranosyl-(1 --> 2)-[beta-D-xylopyranosyl-(1 --> 6)]-beta-D-glucopyranosyl-20-O-beta-D-glucopyranoside, were respectively synthesized from p-nitrophenyl beta-D-xylopyranoside and phenyl beta-D-xylopyranoside as donors and ginsenoside Re as the acceptor in 25% acetone and acetonitrile by a cellulase preparation from Trichoderma viride and a beta-galactosidase preparation from Aspergillus oryzae. The latter enzyme preparation also catalyzed the hydrolysis of ginsenoside Re to the minor saponin, ginsenoside Rg2. 相似文献
16.
17.
Curt Koßwig 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1932,4(1):22-32
Ohne Zusammenfassung 相似文献
18.
19.
20.
Purification and Characterization of Cytosolic NADP Specific Isocitrate Dehydrogenase from Pisum sativum 总被引:2,自引:2,他引:0
Cytosolic NADP-specific isocitrate dehydrogenase was isolated from leaves of Pisum sativum. The purified enzyme was obtained by ammonium sulfate fractionation, ion exchange, affinity, and gel filtration chromatography. The purification procedure yields greater than 50% of the total enzyme activity originally present in the crude extract. The enzyme has a native molecular weight of 90 kilodaltons and is resolved into two catalytically active bands by isoelectric focusing. Purified NADP-isocitrate dehydrogenase exhibited Km values of 23 micromolar for dl-isocitrate and 10 micromolar for NADP, and displayed optimum activity at pH 8.5 with both Mg2+ and Mn2+. 相似文献