全文获取类型
收费全文 | 2937篇 |
免费 | 235篇 |
国内免费 | 313篇 |
专业分类
3485篇 |
出版年
2024年 | 7篇 |
2023年 | 57篇 |
2022年 | 127篇 |
2021年 | 170篇 |
2020年 | 126篇 |
2019年 | 131篇 |
2018年 | 166篇 |
2017年 | 97篇 |
2016年 | 137篇 |
2015年 | 194篇 |
2014年 | 220篇 |
2013年 | 218篇 |
2012年 | 264篇 |
2011年 | 251篇 |
2010年 | 162篇 |
2009年 | 127篇 |
2008年 | 165篇 |
2007年 | 156篇 |
2006年 | 124篇 |
2005年 | 85篇 |
2004年 | 87篇 |
2003年 | 50篇 |
2002年 | 73篇 |
2001年 | 45篇 |
2000年 | 31篇 |
1999年 | 41篇 |
1998年 | 32篇 |
1997年 | 30篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1994年 | 13篇 |
1993年 | 12篇 |
1992年 | 17篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1980年 | 1篇 |
排序方式: 共有3485条查询结果,搜索用时 0 毫秒
31.
32.
33.
34.
Ju Wen Sun Tiantian Lu Wenyi Smith Alhaji Osman Bao Yurong Adzraku Seyram Yao Qi Kunming Xu Kailin Qiao Jianlin Zeng Lingyu 《Molecular biology reports》2020,47(4):2735-2748
Molecular Biology Reports - Murine bone marrow-derived macrophages (M0) and M1- and M2-polarized macrophages are being widely used as a laboratory model for polarized macrophages related molecular... 相似文献
35.
Recently, the use of hybrid double network (DN) hydrogels has become prominent due to their enhanced mechanical properties, which has opened the door for new applications of these soft materials. Only a few of these gels have demonstrated both injectable and moldable capabilities. In this work, we report the mechanical properties, gauge factor (GF) values and demonstrate both the injectability and moldability of a gelatin/polyacrylamide DN hydrogel. We optimized several parameters, such as, gelatin to polyacrylamide ratio, reactant concentrations and metal ion concentration, to produce a gelatin/polyacrylamide hydrogel with superior mechanical properties. The highest water content gel was capable of withstanding strains of 5000% before failure. These gels were facilely injected into molds where they effectively changed shape and maintained similar properties prior to remolding. When 20 mM calcium was doped into a similar gel, a tensile strength of 1.71 MPa was achieved. Aside from improving the mechanical properties of the gels, both Ca2+ and Mg2+ also improved their conductivity, so they were tested for use as strain sensors. The sensitivity of the hydrogel strain sensors were measured using the GF. For the 20 mM Ca2+ hydrogel, these GF values ranged from 1.63 to 6.85 for strains of 100% to 2100% respectively. Additionally, the sensors showed good stability over continuous cyclic stretching, demonstrating their long term reliability for strain sensing. 相似文献
36.
Xing Pan Xiao-Jun Li Xi-Juan Liu Hui Yuan Jia-Fu Li Ying-Liang Duan Han-Qing Ye Ya-Ru Fu Guan-Hua Qiao Cong-Cong Wu Bo Yang Xiao-Hui Tian Kang-Hong Hu Ling-Feng Miao Xiao-Ling Chen Jun Zheng Simon Rayner Philip H. Schwartz William J. Britt Jiang Xu Min-Hua Luo 《Journal of virology》2013,87(20):10968-10979
Congenital human cytomegalovirus (HCMV) infection is the most frequent infectious cause of birth defects, primarily neurological disorders. Neural progenitor/stem cells (NPCs) are the major cell type in the subventricular zone and are susceptible to HCMV infection. In culture, the differentiation status of NPCs may change with passage, which in turn may alter susceptibility to virus infection. Previously, only early-passage (i.e., prior to passage 9) NPCs were studied and shown to be permissive to HCMV infection. In this study, NPC cultures derived at different gestational ages were evaluated after short (passages 3 to 6) and extended (passages 11 to 20) in vitro passages for biological and virological parameters (i.e., cell morphology, expression of NPC markers and HCMV receptors, viral entry efficiency, viral gene expression, virus-induced cytopathic effect, and release of infectious progeny). These parameters were not significantly influenced by the gestational age of the source tissues. However, extended-passage cultures showed evidence of initiation of differentiation, increased viral entry, and more efficient production of infectious progeny. These results confirm that NPCs are fully permissive for HCMV infection and that extended-passage NPCs initiate differentiation and are more permissive for HCMV infection. Later-passage NPCs being differentiated and more permissive for HCMV infection suggest that HCMV infection in fetal brain may cause more neural cell loss and give rise to severe neurological disabilities with advancing brain development. 相似文献
37.
Canwei Xia Jiayu Liu Per Alström Qiao Wu Yanyun Zhang 《Ethology : formerly Zeitschrift fur Tierpsychologie》2013,119(8):653-661
Soft songs have been detected in many songbirds, but in most species, research on soft songs has lagged behind studies of broadcast songs. In this study, we describe the acoustic features of a soft song in the brownish‐flanked bush warbler Cettia fortipes. Compared with the broadcast song, the warbler's soft song was characterized by a lower minimum frequency and longer duration, and it had a higher proportion of rapid frequency modulation notes. Using playback experiments, some in combination with mounted specimens, we found different responses to soft and broadcast songs, and we found that soft song can predict aggressive escalation (attack). We conclude that the soft song is an aggressive signal in this species. 相似文献
38.
Zheng Liu Ning Sun Shangjun Yang Yanhong Zhao Xiaoqin Wang Xingyu Hao Zhijun Qiao 《Biologia》2013,68(4):577-586
Compared with C3 plants, C4 plants possess a mechanism to concentrate CO2 around the ribulose-1,5-bisphosphate carboxylase/oxygenase in chloroplasts of bundle sheath cells so that the carboxylation reaction work at a much more efficient rate, thereby substantially eliminate the oxygenation reaction and the resulting photorespiration. It is observed that C4 photosynthesis is more efficient than C3 photosynthesis under conditions of low atmospheric CO2, heat, drought and salinity, suggesting that these factors are the important drivers to promote C4 evolution. Although C4 evolution took over 66 times independently, it is hypothesized that it shared the following evolutionary trajectory: 1) gene duplication followed by neofunctionalization; 2) anatomical and ultrastructral changes of leaf architecture to improve the hydraulic systems; 3) establishment of two-celled photorespiratory pump; 4) addition of transport system; 5) co-option of the duplicated genes into C4 pathway and adaptive changes of C4 enzymes. Based on our current understanding on C4 evolution, several strategies for engineering C4 rice have been proposed to increase both photosynthetic efficiency and yield significantly in order to avoid international food crisis in the future, especially in the developing countries. Here we summarize the latest progresses on the studies of C4 evolution and discuss the strategies to introduce two-celled C4 pathway into rice. 相似文献
39.
Qiao Sun Yiwu Yao Chunping Liu Hua Li Hequan Yao Xiaowen Xue Jinsong Liu Zhengchao Tu Sheng Jiang 《Bioorganic & medicinal chemistry letters》2013,23(11):3295-3299
We report the design, synthesis, and biological evaluation of a new series of HDAC1 inhibitors using click chemistry. Compound 17 bearing a phenyl ring at meta-position was identified to show much better selectivity for HDAC1 over HDAC7 than SAHA. The compond 17 also showed better in vitro anticancer activities against several cancer cell lines than that of SAHA. This work could serve as a foundation for further exploration of selective HDAC inhibitors using the compound 17 molecular scaffold. 相似文献
40.