全文获取类型
收费全文 | 21023篇 |
免费 | 1949篇 |
国内免费 | 1431篇 |
专业分类
24403篇 |
出版年
2023年 | 254篇 |
2022年 | 563篇 |
2021年 | 946篇 |
2020年 | 624篇 |
2019年 | 718篇 |
2018年 | 769篇 |
2017年 | 582篇 |
2016年 | 764篇 |
2015年 | 1253篇 |
2014年 | 1381篇 |
2013年 | 1510篇 |
2012年 | 1749篇 |
2011年 | 1674篇 |
2010年 | 1081篇 |
2009年 | 915篇 |
2008年 | 1002篇 |
2007年 | 971篇 |
2006年 | 878篇 |
2005年 | 776篇 |
2004年 | 700篇 |
2003年 | 626篇 |
2002年 | 585篇 |
2001年 | 437篇 |
2000年 | 445篇 |
1999年 | 398篇 |
1998年 | 192篇 |
1997年 | 179篇 |
1996年 | 172篇 |
1995年 | 135篇 |
1994年 | 159篇 |
1993年 | 104篇 |
1992年 | 186篇 |
1991年 | 178篇 |
1990年 | 141篇 |
1989年 | 130篇 |
1988年 | 107篇 |
1987年 | 113篇 |
1986年 | 105篇 |
1985年 | 119篇 |
1984年 | 63篇 |
1983年 | 65篇 |
1982年 | 59篇 |
1981年 | 47篇 |
1980年 | 44篇 |
1979年 | 64篇 |
1978年 | 54篇 |
1977年 | 55篇 |
1976年 | 39篇 |
1975年 | 40篇 |
1974年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
茄子是重要的园艺作物,也是茄科植物中种植最广泛的蔬菜之一。茄子果实相关农艺性状是一种复杂的数量性状,传统育种选育效率低、周期长。高通量测序技术与生物信息学技术的快速发展,使得全基因组关联分析(genome-wide association study, GWAS)在解析茄子果实相关复杂农艺性状的遗传规律方面展现出巨大的应用前景。本文对全基因组关联分析在茄子的果形、果色等果实相关农艺性状中的研究进展进行了综述;针对茄子数量性状遗传研究中普遍存在的“丢失遗传力”(missing heritability)问题,从4个GWAS策略在茄子果实相关农艺性状研究中的应用热点出发,提出了未来茄子GWAS的发展对策;并结合当前茄子遗传改良的实践需求,展望了GWAS策略在茄子分子育种领域的广阔应用前景。本文为今后利用GWAS解析各种茄子果实相关性状的遗传基础以及选育符合消费者需求的果实材料提供了理论依据和参考。 相似文献
43.
44.
Ennian Li Kai Wang Bei Zhang Siqi Guo Senhao Xiao Qi Pan Xiaowan Wang Weiying Chen Yunshan Wu Hesong Xu Xiangqian Kong Cheng Luo Shijie Chen Bo Liu 《Journal of enzyme inhibition and medicinal chemistry》2022,37(1):1537
The DNA methyltransferases (DNMTs) were found in mammals to maintain DNA methylation. Among them, DNMT1 was the first identified, and it is an attractive target for tumour chemotherapy. DC_05 and DC_517 have been reported in our previous work, which is non-nucleoside DNMT1 inhibitor with low micromolar IC50 values and significant selectivity towards other S-adenosyl-L-methionine (SAM)-dependent protein methyltransferases. In this study, through a process of similarity-based analog searching, a series of DNMT1 inhibitors were designed, synthesized, and evaluated as anticancer agents. SAR studies were conducted based on enzymatic assays. And most of the compounds showed strong inhibitory activity on human DNMT1, especially WK-23 displayed a good inhibitory effect on human DNMT1 with an IC50 value of 5.0 µM. Importantly, the pharmacokinetic (PK) profile of WK-23 was obtained with quite satisfying oral bioavailability and elimination half-life. Taken together, WK-23 is worth developing as DNMT1-selective therapy for the treatment of malignant tumour. 相似文献
45.
High-resolution finite element models with tissue strength asymmetry accurately predict failure of trabecular bone 总被引:13,自引:0,他引:13
The ability to predict trabecular failure using microstructure-based computational models would greatly facilitate study of trabecular structure–function relations, multiaxial strength, and tissue remodeling. We hypothesized that high-resolution finite element models of trabecular bone that include cortical-like strength asymmetry at the tissue level, could predict apparent level failure of trabecular bone for multiple loading modes. A bilinear constitutive model with asymmetric tissue yield strains in tension and compression was applied to simulate failure in high-resolution finite element models of seven bovine tibial specimens. Tissue modulus was reduced by 95% when tissue principal strains exceeded the tissue yield strains. Linear models were first calibrated for effective tissue modulus against specimen-specific experimental measures of apparent modulus, producing effective tissue moduli of (mean±S.D.) 18.7±3.4 GPa. Next, a parameter study was performed on a single specimen to estimate the tissue level tensile and compressive yield strains. These values, 0.60% strain in tension and 1.01% strain in compression, were then used in non-linear analyses of all seven specimens to predict failure for apparent tensile, compressive, and shear loading. When compared to apparent yield properties previously measured for the same type of bone, the model predictions of both the stresses and strains at failure were not statistically different for any loading case (p>0.15). Use of symmetric tissue strengths could not match the experimental data. These findings establish that, once effective tissue modulus is calibrated and uniform but asymmetric tissue failure strains are used, the resulting models can capture the apparent strength behavior to an outstanding level of accuracy. As such, these computational models have reached a level of fidelity that qualifies them as surrogates for destructive mechanical testing of real specimens. 相似文献
46.
47.
48.
49.
Brome mosaic virus, good for an RNA virologist's basic needs 总被引:3,自引:0,他引:3
50.