全文获取类型
收费全文 | 2010篇 |
免费 | 180篇 |
国内免费 | 49篇 |
出版年
2024年 | 3篇 |
2023年 | 50篇 |
2022年 | 54篇 |
2021年 | 78篇 |
2020年 | 66篇 |
2019年 | 78篇 |
2018年 | 88篇 |
2017年 | 60篇 |
2016年 | 68篇 |
2015年 | 79篇 |
2014年 | 148篇 |
2013年 | 131篇 |
2012年 | 83篇 |
2011年 | 110篇 |
2010年 | 117篇 |
2009年 | 115篇 |
2008年 | 111篇 |
2007年 | 101篇 |
2006年 | 81篇 |
2005年 | 71篇 |
2004年 | 70篇 |
2003年 | 59篇 |
2002年 | 64篇 |
2001年 | 38篇 |
2000年 | 39篇 |
1999年 | 22篇 |
1998年 | 30篇 |
1997年 | 23篇 |
1996年 | 21篇 |
1995年 | 20篇 |
1994年 | 16篇 |
1993年 | 16篇 |
1992年 | 14篇 |
1991年 | 19篇 |
1990年 | 13篇 |
1989年 | 6篇 |
1988年 | 14篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有2239条查询结果,搜索用时 15 毫秒
81.
Spermatogenesis is a highly ordered developmental program that produces haploid male germ cells. The study of male germ cell development in the mouse has provided unique perspectives into the molecular mechanisms that control cell development and differentiation in mammals, including tissue‐specific gene regulatory programs. An intrinsic challenge in spermatogenesis research is the heterogeneity of germ and somatic cell types present in the testis. Techniques to separate and isolate distinct mouse spermatogenic cell types have great potential to shed light on molecular mechanisms controlling mammalian cell development, while also providing new insights into cellular events important for human reproductive health. Here, we detail a versatile strategy that combines Cre‐lox technology to fluorescently label germ cells, with flow cytometry to discriminate and isolate germ cells in different stages of development for cellular and molecular analyses. 相似文献
82.
83.
84.
85.
86.
87.
Variance in reproductive success is a major determinant of the degree of genetic drift in a population. While many plants and animals exhibit high variance in their number of progeny, far less is known about these distributions for microorganisms. Here, we used a strain barcoding approach to quantify variability in offspring number among replicate bacterial populations and developed a Bayesian method to infer the distribution of descendants from this variability. We applied our approach to measure the offspring distributions for five strains of bacteria from the genus Streptomyces after germination and growth in a homogenous laboratory environment. The distributions of descendants were heavy‐tailed, with a few cells effectively ‘winning the jackpot’ to become a disproportionately large fraction of the population. This extreme variability in reproductive success largely traced back to initial populations of spores stochastically exiting dormancy, which provided early‐germinating spores with an exponential advantage. In simulations with multiple dormancy cycles, heavy‐tailed distributions of descendants decreased the effective population size by many orders of magnitude and led to allele dynamics differing substantially from classical population genetics models with matching effective population size. Collectively, these results demonstrate that extreme variability in reproductive success can occur even in growth conditions that are far more homogeneous than the natural environment. Thus, extreme variability in reproductive success might be an important factor shaping microbial population dynamics with implications for predicting the fate of beneficial mutations, interpreting sequence variability within populations and explaining variability in infection outcomes across patients. 相似文献
88.
Guofeng Yang Yanqin Ju Shangfeng Liu Shouliang Zhao 《Cell biology international》2019,43(11):1276-1285
NG2+ cells have been proven to differentiate into odontoblasts in vivo, and their contribution to odontoblasts is significantly increased, especially after tooth injury. However, their characteristics in vitro, especially under an inflammatory environment, are still not fully understood. Therefore, this study aimed to explore their proliferation, migration, and odontoblastic differentiation ability after treatment with lipopolysaccharide (LPS) in vitro. In our study, NG2 + cells were isolated from the human dental pulp by magnetic‐activated cell sorting, and these isolated cells were proven to be NG2 + by immunostaining. When compared with human dental pulp cells (hDPCs), the NG2 + cells showed no significant differences in cell migration with or without LPS incubation, but their proliferative ability was weaker. When treated with LPS, NG2 + cells expressed elevated levels of pro‐inflammatory cytokines including interleukin‐1β (IL‐1β), IL‐6, IL‐8, and tumor necrosis factor‐α, and among these, the expression of IL‐1β and IL‐6 were higher than that of hDPCs. Their multipotent differentiation potential was confirmed by the induction of odontoblastic and adipogenic differentiation, and LPS increased their odontoblastic differentiation capacity. In the odontoblastic differentiation process, Wnt5a, BMP2, and BMP7 mRNA were increased, while the canonical Wnt‐related genes were decreased. In conclusion, the LPS stimulation promotes the migration, proliferative, and odontoblastic differentiation ability of NG2 + cells from the human dental pulp in vitro, and bone morphogenetic protein and the noncanonical Wnt pathway may be involved in their odontoblastic differentiation. These results indicated their special roles in tooth injury repair and potential application in pulp regeneration. 相似文献
89.
90.