全文获取类型
收费全文 | 137827篇 |
免费 | 3611篇 |
国内免费 | 894篇 |
专业分类
142332篇 |
出版年
2024年 | 52篇 |
2023年 | 176篇 |
2022年 | 566篇 |
2021年 | 914篇 |
2020年 | 569篇 |
2019年 | 683篇 |
2018年 | 12547篇 |
2017年 | 11259篇 |
2016年 | 8705篇 |
2015年 | 2881篇 |
2014年 | 2929篇 |
2013年 | 3253篇 |
2012年 | 7999篇 |
2011年 | 16202篇 |
2010年 | 14059篇 |
2009年 | 10137篇 |
2008年 | 12556篇 |
2007年 | 13979篇 |
2006年 | 2783篇 |
2005年 | 2847篇 |
2004年 | 3100篇 |
2003年 | 2866篇 |
2002年 | 2374篇 |
2001年 | 1552篇 |
2000年 | 1384篇 |
1999年 | 1012篇 |
1998年 | 400篇 |
1997年 | 359篇 |
1996年 | 254篇 |
1995年 | 209篇 |
1994年 | 212篇 |
1993年 | 201篇 |
1992年 | 346篇 |
1991年 | 332篇 |
1990年 | 273篇 |
1989年 | 233篇 |
1988年 | 190篇 |
1987年 | 176篇 |
1986年 | 131篇 |
1985年 | 105篇 |
1984年 | 85篇 |
1983年 | 101篇 |
1982年 | 65篇 |
1981年 | 53篇 |
1980年 | 55篇 |
1979年 | 69篇 |
1978年 | 51篇 |
1974年 | 63篇 |
1972年 | 278篇 |
1971年 | 308篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
Sudhasri Mohanty Jonghan Kim Latha P. Ganesan Gary S. Phillips John M. Robinson Clark L. Anderson 《PloS one》2013,8(7)
FcRn, a non-classical MHCI molecule, transports IgG from mother to young and regulates the rate of IgG degradation throughout life. Brambell proposed a mechanism that unified these two functions, saying that IgG was pinocytosed nonspecifically by the cell into an FcRn-expressing endosome, where, at low pH, it bound to FcRn and was exocytosed. This theory was immediately challenged by claims that FcRn specificity for ligand could be conferred at the cell surface in neonatal jejunum. Assessing Brambell''s hypothesis we found abundant nonspecifically endocytosed IgG present in the cytoplasm of FcRn−/− enterocytes. Further, IgG was present in the intercellular clefts and the cores of FcRn+/+ but not FcRn−/− jejunum. FcRn specificity for ligand could be determined within the cell. 相似文献
973.
Yi Yoonjung Fichtel Claudia Kim Erick Choe Jae C. 《International journal of primatology》2020,41(2):363-381
International Journal of Primatology - Agonistic intergroup interactions can cause individual costs such as physical injuries, increased physiological stress, and disrupted intragroup social... 相似文献
974.
Lee Yun-Ah Kim Se-Hong Kim Ha-Na Song Sang-Wook 《Biological trace element research》2020,193(2):311-318
Biological Trace Element Research - Obesity is a risk factor for metabolic syndrome, dyslipidemia, hypertension, insulin resistance, type 2 diabetes mellitus, and cardiovascular disease. However,... 相似文献
975.
976.
AbstractThis study aimed to evaluate the effects of tea extracts on oral biofilm colonization depending on steeping temperature. S. mutans and S. sobrinus were cultured and treated with green or black tea extracts prepared under different steeping conditions. Biofilm formation, glucosyltransferase (GTF) levels, bacterial growth, and acidogenicity were evaluated. Biofilms were also assessed by gas chromatography-mass spectrometry and confocal laser scanning microscopy. All extracts with hot steeping showed higher inhibitory effects on biofilm formation and cell viability and lower GTF levels compared with those with cold steeping (p?<?0.05). Hot steeping significantly reduced bacterial growth (p?<?0.05) and maintained the pH. Catechins were only identified from hot steeping extracts. Within the limits of this study, extracts with cold steeping showed lower inhibitory effects on oral biofilms. The different effects between steeping extracts may be attributed to the difference in catechins released from tea extracts under the different steep conditions. 相似文献
977.
978.
979.
Linggai Cao Hao Wu He Zhang Quan Zhao Xue Yin Dongran Zheng Chuanwang Li Min-Jun Kim Pyol Kim Zheyong Xue Yu Wang Yuhua Li 《Biotechnology and bioengineering》2020,117(6):1615-1627
The rare ginsenosides are recognized as the functionalized molecules after the oral administration of Panax ginseng and its products. The sources of rare ginsenosides are extremely limited because of low ginsenoside contents in wild plants, hindering their application in functional foods and drugs. We developed an effective combinatorial biotechnology approach including tissue culture, immobilization, and hydrolyzation methods. Rh2 and nine other rare ginsenosides were produced by methyl jasmonate-induced culture of adventitious roots in a 10 L bioreactor associated with enzymatic hydrolysis using six β-glycosidases and their combination with yields ranging from 5.54 to 32.66 mg L−1. The yield of Rh2 was furthermore increased by 7% by using immobilized BglPm and Bgp1 in optimized pH and temperature conditions, with the highest yield reaching 51.17 mg L−1 (17.06% of protopanaxadiol-type ginsenosides mixture). Our combinatorial biotechnology method provides a highly efficient approach to acquiring diverse rare ginsenosides, replacing direct extraction from Panax plants, and can also be used to supplement yeast cell factories. 相似文献
980.
Priyanka Kushwaha Soohyun Kim Gabrielle E. Foxa Megan N. Michalski Bart O. Williams Ryan E. Tomlinson Ryan C. Riddle 《Journal of cellular physiology》2020,235(10):6673-6683
The activation of the Wnt/β-catenin signaling pathway is critical for skeletal development but surprisingly little is known about the requirements for the specific frizzled (Fzd) receptors that recognize Wnt ligands. To define the contributions of individual Fzd proteins to osteoblast function, we profiled the expression of all 10 mammalian receptors during calvarial osteoblast differentiation. Expression of Fzd4 was highly upregulated during in vitro differentiation and therefore targeted for further study. Mice lacking Fzd4 in mature osteoblasts had normal cortical bone structure but reduced cortical tissue mineral density and also exhibited an impairment in the femoral trabecular bone acquisition that was secondary to a defect in the mineralization process. Consistent with this observation, matrix mineralization, markers of osteoblastic differentiation, and the ability of Wnt3a to stimulate the accumulation of β-catenin were reduced in cultures of calvarial osteoblasts deficient for Fzd4. Interestingly, Fzd4-deficient osteoblasts exhibited an increase in the expression of Fzd8 both in vitro and in vivo, which suggests that the two receptors may exhibit overlapping functions. Indeed, ablating a single Fzd8 allele in osteoblast-specific Fzd4 mutants produced a more severe effect on bone acquisition. Taken together, our data indicate that Fzd4 is required for normal bone development and mineralization despite compensation from Fzd8. 相似文献