全文获取类型
收费全文 | 110559篇 |
免费 | 8459篇 |
国内免费 | 6976篇 |
专业分类
125994篇 |
出版年
2024年 | 215篇 |
2023年 | 1452篇 |
2022年 | 3239篇 |
2021年 | 5480篇 |
2020年 | 3577篇 |
2019年 | 4375篇 |
2018年 | 4354篇 |
2017年 | 3233篇 |
2016年 | 4602篇 |
2015年 | 6678篇 |
2014年 | 7866篇 |
2013年 | 8314篇 |
2012年 | 9962篇 |
2011年 | 8870篇 |
2010年 | 5445篇 |
2009年 | 4748篇 |
2008年 | 5591篇 |
2007年 | 4925篇 |
2006年 | 4371篇 |
2005年 | 3332篇 |
2004年 | 2933篇 |
2003年 | 2535篇 |
2002年 | 2205篇 |
2001年 | 2001篇 |
2000年 | 1860篇 |
1999年 | 1841篇 |
1998年 | 1017篇 |
1997年 | 1137篇 |
1996年 | 1018篇 |
1995年 | 919篇 |
1994年 | 942篇 |
1993年 | 666篇 |
1992年 | 994篇 |
1991年 | 838篇 |
1990年 | 613篇 |
1989年 | 559篇 |
1988年 | 487篇 |
1987年 | 411篇 |
1986年 | 388篇 |
1985年 | 390篇 |
1984年 | 211篇 |
1983年 | 197篇 |
1982年 | 137篇 |
1981年 | 114篇 |
1980年 | 107篇 |
1979年 | 115篇 |
1978年 | 78篇 |
1977年 | 60篇 |
1974年 | 74篇 |
1972年 | 62篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Gang Tang Li-wei Qian Gao-feng Wei Hong-sheng Wang 《Computer methods in biomechanics and biomedical engineering》2013,16(3):275-283
Muscle force estimation (MFE) has become more and more important in exploring principles of pathological movement, studying functions of artificial muscles, making surgery plan for artificial joint replacement, improving the biomechanical effects of treatments and so on. At present, existing software are complex for professionals, so we have developed a new software named as concise MFE (CMFE). CMFE which provides us a platform to analyse muscle force in various actions includes two MFE methods (static optimisation method and electromyographic-based method). Common features between these two methods have been found and used to improve CMFE. A case studying the major muscles of lower limb of a healthy subject walking at normal speed has been presented. The results are well explained from the effect of the motion produced by muscles during movement. The development of this software can improve the accuracy of the motion simulations and can provide a more extensive and deeper insight in to muscle study. 相似文献
992.
993.
994.
Wei Bao Lei Jin Hai-jing Fu Yong-nian Shen Gui-xia Lu Huan Mei Xin-zhi Cao Hong-sheng Wang Wei-da Liu 《PloS one》2013,8(6)
Background
In recent years, the fungal infectious disease zygomycosis has increased in incidence worldwide, especially among the immunodeficient population. Despite the rates of zygomycosis-related death and deformation being very high, the mechanism(s) by which the fungal pathogens cause these severe manifestations remain unknown.Methods
Using the associated Rhizomucor variabilis species, which can selectively induce cutaneous zygomycosis in otherwise healthy individuals, we investigated the host mechanisms of infection-related responses, including cytokine and chemokine expression as well as contributions of particular T cell subsets. siRNA specifically targeting IL-22,IL-17 and IFN-γ were used to down-regulate expression of those molecules.Results
In mouse models of infection, IL-22 was implicated in development of Rhizomucor spp.-induced skin lesions. In cultured human peripheral blood monocytes, R. pusilluscan, which is often found in immunodeficient patients, induced the production of IL-22, while R. variabilis did not. Moreover, Rhizomucor spp.-induced secretion of Il-22 from CCR6+CCR4+CCR10+ cells was down-regulated by knockdown of IL-22 related signaling receptors, RORC and ARH.Conclusion
Our data strongly suggest that avoidance of IL-22 may be one mechanism by which mucor species produce morbidity and mortality in infected individuals. 相似文献995.
Xiaolu Qu Hua Zhang Yurong Xie Juan Wang Naizhi Chen Shanjin Huang 《The Plant cell》2013,25(5):1803-1817
Apical actin filaments are crucial for pollen tube tip growth. However, the specific dynamic changes and regulatory mechanisms associated with actin filaments in the apical region remain largely unknown. Here, we have investigated the quantitative dynamic parameters that underlie actin filament growth and disappearance in the apical regions of pollen tubes and identified villin as the major player that drives rapid turnover of actin filaments in this region. Downregulation of Arabidopsis thaliana VILLIN2 (VLN2) and VLN5 led to accumulation of actin filaments at the pollen tube apex. Careful analysis of single filament dynamics showed that the severing frequency significantly decreased, and the lifetime significantly increased in vln2 vln5 pollen tubes. These results indicate that villin-mediated severing is critical for turnover and departure of actin filaments originating in the apical region. Consequently, the construction of actin collars was affected in vln2 vln5 pollen tubes. In addition to the decrease in severing frequency, actin filaments also became wavy and buckled in the apical cytoplasm of vln2 vln5 pollen tubes. These results suggest that villin confers rigidity upon actin filaments. Furthermore, an observed decrease in skewness of actin filaments in the subapical region of vln2 vln5 pollen tubes suggests that villin-mediated bundling activity may also play a role in the construction of actin collars. Thus, our data suggest that villins promote actin turnover at pollen tube tips and facilitate the construction of actin collars. 相似文献
996.
Granulocyte colony-stimulating factor (G-CSF) induces stem cells to mobilize to the injury site, which have beneficial effect on tissue repair. The aim of this study was to investigate the effect of G-CSF on the thin endometrium in rat models. In the present study, rats with thin endometrium were divided into 4 groups (experimental group I: administrated with G-CSF (40 µg/kg/d) 4–6 hours post-modeling; control group I: administrated with saline 4–6 hours post-modeling; experimental group II: administrated with G-CSF (40 µg/kg/d) 12 days post-modeling; control group II: administrated with saline 12 days post-modeling. The agentia was given once daily and last for 5 days. Endometrial morphology was analyzed by Hematoxylin-Eosin staining, and the regeneration of endometrial cells was evaluated by immunohistochemistry and western-blot with cytokeratin and vimentin. We found that endometrial thickness and morphology presented a significant difference between experimental groups and control groups. No matter when we start with G-CSF, there was a significantly thicker endometrium and stronger expression of cytokeratin/vimintin in the experimental groups compared with the control groups (P<0.01). There were significant thicker endometrial lining and stronger expression of cytokeratin/vimintin in experimental group I than that of experimental group II (P<0.05), but there was no difference in the endometrial lining and the expression of cytokeratin/vimintin between the two control groups (P>0.05). In conclusion, G-CSF can promote the regeneration of endometrial cells in animal research, especially when the G-CSF was administrated earlier. 相似文献
997.
Yan Zhang De-ying Zhang Yan-fang Zhao Jin Wang Juan-wen He Jinyong Luo 《BMB reports》2013,46(2):107-112
Although BMP6 is highly capable of inducing osteogenic differentiation of mesenchymal progenitor cells (MPCs), the molecular mechanism involved remains to be fully elucidated. Using dominant negative (dn) mutant form of type I and type II TGFβ receptors, we demonstrated that three dn-type I receptors (dnALK2, dnALK3, dnALK6), and three dn-type II receptors (dnBMPRII, dnActRII, dnActRIIB), effectively diminished BMP6-induced osteogenic differentiation of MPCs. These findings suggested that ALK2, ALK3, ALK6, BMPRII, ActRII and ActRIIB are essential for BMP6-induced osteogenic differentiation of MPCs. However, MPCs in this study do not express ActRIIB. Moreover, RNA interference of ALK2, ALK3, ALK6, BMPRII and ActRII inhibited BMP6-induced osteogenic differentiation in MPCs. Our results strongly suggested that BMP6-induced osteogenic differentiation of MPCs is mediated by its functional TGFβ receptors including ALK2, ALK3, ALK6, BMPRII, and ActRII. [BMB Reports 2013; 46(2): 107-112] 相似文献
998.
Mutagenicity and polycyclic aromatic hydrocarbon content of fumes from heated cooking oils produced in Taiwan 总被引:6,自引:0,他引:6
Tai-An Chiang Pei-Fen Wu Li-Fang Wang Huei Lee Chien-Hung Lee Ying-Chin Ko 《Mutation research》1997,381(2):1443-161
According to epidemiologic studies, exposure of women to fumes from cooking oils appears to be an important risk factor for lung cancer. Fume samples from three different commercial cooking oils frequently used in Taiwan were collected and analyzed for mutagenicity in the Salmonella/microsome assay. Polycyclic aromatic hydrocarbons were extracted from the samples and identified by HPLC chromatography. Extracts from three cooking oil fumes were found to be mutagenic in the presence of S9 mix. All samples contained dibenz[a,h]anthracene (DB[a,h]A) and benz[a]anthracene (B[a]A). Concentration of DB[a,h]A and B[a]A were 1.9 and 2.2 μg/m3 in fumes from lard oil, 2.1 and 2.3 μg/m3 in soybean oil, 1.8 and 1.3 μg/m3 in peanut oil, respectively. Benzo[a]pyrene (B[a]P) was identified in fume samples of soybean and peanut oil, in concentrations of 19.6 and 18.3 μg/m3, in this order. These results provide experimental evidence and support the findings of epidemiologic observations, in which women exposed to the emitted fumes of cooking oils are at increased risk of contracting lung cancer. 相似文献
999.
1000.