全文获取类型
收费全文 | 2232篇 |
免费 | 186篇 |
国内免费 | 140篇 |
出版年
2024年 | 4篇 |
2023年 | 27篇 |
2022年 | 69篇 |
2021年 | 127篇 |
2020年 | 72篇 |
2019年 | 78篇 |
2018年 | 91篇 |
2017年 | 77篇 |
2016年 | 99篇 |
2015年 | 159篇 |
2014年 | 156篇 |
2013年 | 176篇 |
2012年 | 214篇 |
2011年 | 205篇 |
2010年 | 111篇 |
2009年 | 92篇 |
2008年 | 105篇 |
2007年 | 80篇 |
2006年 | 71篇 |
2005年 | 56篇 |
2004年 | 44篇 |
2003年 | 42篇 |
2002年 | 47篇 |
2001年 | 33篇 |
2000年 | 32篇 |
1999年 | 42篇 |
1998年 | 16篇 |
1997年 | 21篇 |
1996年 | 15篇 |
1995年 | 13篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 15篇 |
1990年 | 19篇 |
1989年 | 9篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 9篇 |
1974年 | 6篇 |
1973年 | 3篇 |
1970年 | 5篇 |
排序方式: 共有2558条查询结果,搜索用时 15 毫秒
101.
Yue Liu Songhua Xu Xiuli Lian Yang Su Yuhuan Zhong Ruimin Lv 《Cell cycle (Georgetown, Tex.)》2019,18(4):437-451
Zygotic genome activation (ZGA) is one of the most critical events at the beginning of mammalian preimplantation embryo development (PED). The mechanisms underlying mouse ZGA remain unclear although it has been widely studied. In the present study, we identified that tricho-rhino-phalangeal syndrome 1 (TRPS1), an atypical GATA family member, is an important factor for ZGA in mouse PED. We found that the Trps1 mRNA level peaked at the one-cell stage while TRPS1 protein did so at the two/four-cell stage. Knockdown of Trps1 by the microinjection of Trps1 siRNA reduced the developmental rate of mouse preimplantation embryos by approximately 30%, and increased the expression of ZGA marker genes MuERV-L and Zscan4d via suppressing the expression of major histone markers H3K4me3 and H3K27me3. Furthermore, Trps1 knockdown decreased the expression of Sox2 but increased Oct4 expression. We conclude that TRPS1 may be indispensable for zygotic genome activation during mouse PED. 相似文献
102.
103.
104.
Teng Liu Min Lu Binguo Chen Qinsong Zhong Jingyu Li Honghui He Hua Mao Hui Ma 《Journal of biophotonics》2019,12(12)
Recently, the incidence of inflammatory bowel diseases, especially the Crohn's disease (CD) and gastrointestinal luminal tuberculosis (ITB), has grown rapidly worldwide. Currently there is no general gold standard to distinguish between CD and ITB tissues, which both have tuberculosis and surrounding fibrous structures. Mueller matrix imaging technique is suitable for describing the location, density and distribution behavior of such fibrous structures. In this study, we apply the Mueller matrix microscopic imaging to the CD and ITB tissue samples. The 2D Mueller matrix images of the CD and ITB tissue slices are measured using the Mueller matrix microscope developed in our previous study, then the Mueller matrix polar decomposition and Mueller matrix transformation parameters are calculated. To evaluate the distribution features of the fibrous structures surrounding the tuberculosis areas more quantitatively and precisely, we analyze the retardance related Mueller matrix derived parameters, which show clear different distribution behaviors between the CD and ITB tissues, using the Tamura image processing method. It is demonstrated that the Mueller matrix derived parameters can reveal the structural features of tuberculosis areas and be used as quantitative indicators to distinguish between CD and ITB tissues, which may be useful for the clinical diagnosis. 相似文献
105.
106.
107.
108.
Shear stress is an important biomechanical parameter in regulating human mesenchymal stem cell (hMSC) construct development. In this study, the biomechanical characteristics of hMSCs within highly porous 3-D poly (ethylene terephthalate) (PET) matrices in a perfusion bioreactor system were analyzed for two flow rates of 0.1 and 1.5 mL/min, respectively over a 20-day culture period. A 1.4 times higher proliferation rate, higher CFU-F formation, and more fibronectin and HSP-47 secretion at day 20 were observed at the flow rate of 0.1 mL/min compared to those at the flow rate of 1.5 mL/min. The higher flow rate of 1.5 mL/min upregulated osteogenic differentiation potential at day 20 as measured by the expression of alkaline phosphatase activity and calcium deposition in the matrix after 14 days osteogenic induction, consistent with those reported in literatures. Mathematical modeling indicated that shear stress existed in the range of 1 x 10(-5) to 1 x 10(-4) Pa in the constructs up to a depth of 70 microm due to flow penetration in the porous constructs. Analysis of oxygen transport in the constructs for the two flow rates yielded oxygen levels significantly higher than those at which cell growth and metabolism are affected (Jiang et al., 1996). This indicates that differences in convective transport have no significant influence on cell growth and metabolism for the range of flow rates studied. These results demonstrate that shear stress is an important microenvironment parameter that regulates hMSC construct development at a range significantly lower than those reported previously in the perfusion system. 相似文献
109.
Endostatin,a C-terminal fragment of collagen 18a,inhibits the growth of established tumorsand metastases in vivo by inhibiting angiogenesis.However,the purification procedures required for large-scale production and the attendant cost of these processes,together with the low effectiveness in clinicaltests,suggest that alternative delivery methods might be required for efficient therapeutic use of endostatin.In the present study,we transfected Chinese hamster ovary(CHO)cells with a human endostatin geneexpression vector and encapsulated the CHO cells in alginate-poly-L-lysine microcapsules.The release ofbiologically active endostatin was confirmed using the chicken chorioallantoic membrane assay.The encap-sulated endostatin-expressing CHO cells can inhibit the growth of primary tumors in a subcutaneous B 16tumor model when injected into the abdominal cavity of mouse.These results widen the clinical applicationof the microencapsulated cell endostatin delivery system in cancer treatment. 相似文献
110.
Food Biophysics - Egg yolk granule is the sedimentary protein fraction of egg yolk. Granules are supramolecular assembly of high-density lipoprotein and phosvitin driven by Ca2+ bridges. Despite... 相似文献