全文获取类型
收费全文 | 54184篇 |
免费 | 17408篇 |
国内免费 | 3042篇 |
专业分类
74634篇 |
出版年
2024年 | 108篇 |
2023年 | 461篇 |
2022年 | 1135篇 |
2021年 | 2120篇 |
2020年 | 3194篇 |
2019年 | 4963篇 |
2018年 | 5023篇 |
2017年 | 4981篇 |
2016年 | 5374篇 |
2015年 | 5742篇 |
2014年 | 5869篇 |
2013年 | 6439篇 |
2012年 | 4493篇 |
2011年 | 3880篇 |
2010年 | 4540篇 |
2009年 | 3148篇 |
2008年 | 2225篇 |
2007年 | 1622篇 |
2006年 | 1355篇 |
2005年 | 1261篇 |
2004年 | 1090篇 |
2003年 | 940篇 |
2002年 | 803篇 |
2001年 | 672篇 |
2000年 | 569篇 |
1999年 | 535篇 |
1998年 | 305篇 |
1997年 | 250篇 |
1996年 | 212篇 |
1995年 | 192篇 |
1994年 | 201篇 |
1993年 | 140篇 |
1992年 | 161篇 |
1991年 | 147篇 |
1990年 | 83篇 |
1989年 | 91篇 |
1988年 | 61篇 |
1987年 | 51篇 |
1986年 | 39篇 |
1985年 | 49篇 |
1984年 | 31篇 |
1983年 | 24篇 |
1982年 | 16篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1972年 | 2篇 |
1950年 | 4篇 |
1873年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
Han ZM Chen DY Li JS Sun QY Wan QH Kou ZH Rao G Lei L Liu ZH Fang SG 《Molecular reproduction and development》2004,67(2):207-214
Adult somatic cell cloned calves were produced by somatic cell nuclear transfer prepared by fusion of cultured ear fibroblast from a Holstein cow into enucleated oocytes of Luxi Yellow cow. In order to determinate the source of mitochondrial DNA of cloned calves, we designed the breed-specific PCR primers by aligning the known D-loop sequences of Bos taurus and analyzed the displacement loop sequences of five live cloned calves by breed-specific primers PCR. The results demonstrated that mtDNA originated from Holstein breed and that from Luxi breed co-exist in all five live calves. 相似文献
992.
阔叶树的叶形曲线方程:—适于叶面积计算的数学模型 总被引:3,自引:0,他引:3
树木的叶形可以看作一个平面几何图形。这种几何图形可用解析方程给予表达,我们把这种解析方程称为叶形曲线方程。由于叶形是一个左右对称,而上下不对称的图形,也就是说叶的最宽处绝大多数不在叶的中部,少数在 相似文献
993.
小麦原胚对外源大分子与不透膜物质的摄入 总被引:5,自引:0,他引:5
为检验小麦原胚基端特定位点上的外连丝型胞间连丝和开放孔道在摄取外源物质上的作用,以不透膜的阳离子铁蛋白(cationized ferritin)和萤黄(lucifer yellow CH )为示踪物,对其吸入与传布动态进行了荧光与电子显微镜观察。结果表明,这两种物质确可以以非跨膜运输的方式沿着原胚基端的特定通道进入原胚细胞。 相似文献
994.
995.
996.
Gao YY Zhang DF Li H Liu R Zhuang ZH Li QF Wang SY Peng XX 《Journal of proteome research》2007,6(11):4321-4329
Elevated creatine kinase (CK) in the circulation was generally regarded to be a passive release from muscle damage. We utilized proteomic methodologies to characterize amphioxus humoral fluid APPs in response to caudal trauma, and found several spots of CK alterations with up-regulation and pI shift. Its amount and enzyme activity showed a dynamic pattern of APP in humoral fluid accompanied with a reduction in enzyme activity of muscle, whereas there was no significant difference in CK amount of muscle and the other tissues and in CK enzyme activity of the other tissues between different time points of sample collection following caudal trauma. In addition, CK phosphorylation regulation during injury was not achieved by monoclonal antibodies separately against phosphothreonine, phosphotyrosine, and phosphoserine. These results suggested that the CK elevation of humoral fluid might be from muscle, being an active response to caudal trauma rather than a passive release from muscle damage. Therefore, CK ability in response to caudal trauma should be highly concerned. 相似文献
997.
Kais Z Barsky SH Mathsyaraja H Zha A Ransburgh DJ He G Pilarski RT Shapiro CL Huang K Parvin JD 《Molecular cancer research : MCR》2011,9(8):1091-1099
To find genes and proteins that collaborate with BRCA1 or BRCA2 in the pathogenesis of breast cancer, we used an informatics approach and found a candidate BRCA interactor, KIAA0101, to function like BRCA1 in exerting a powerful control over centrosome number. The effect of KIAA0101 on centrosomes is likely direct, as its depletion does not affect the cell cycle, KIAA0101 localizes to regions coincident with the centrosomes, and KIAA0101 binds to BRCA1. We analyzed whether KIAA0101 protein is overexpressed in breast cancer tumor samples in tissue microarrays, and we found that overexpression of KIAA0101 correlated with positive Ki67 staining, a biomarker associated with increased disease severity. Furthermore, overexpression of the KIAA0101 gene in breast tumors was found to be associated with significantly decreased survival time. This study identifies KIAA0101 as a protein important for breast tumorigenesis, and as this factor has been reported as a UV repair factor, it may link the UV damage response to centrosome control. 相似文献
998.
999.
Liu P Overman RG Yates NL Alam SM Vandergrift N Chen Y Graw F Freel SA Kappes JC Ochsenbauer C Montefiori DC Gao F Perelson AS Cohen MS Haynes BF Tomaras GD 《Journal of virology》2011,85(21):11196-11207
Understanding the interactions between human immunodeficiency virus type 1 (HIV-1) virions and antibodies (Ab) produced during acute HIV-1 infection (AHI) is critical for defining antibody antiviral capabilities. Antibodies that bind virions may prevent transmission by neutralization of virus or mechanically prevent HIV-1 migration through mucosal layers. In this study, we quantified circulating HIV-1 virion-immune complexes (ICs), present in approximately 90% of AHI subjects, and compared the levels and antibody specificity to those in chronic infection. Circulating HIV-1 virions coated with IgG (immune complexes) were in significantly lower levels relative to the viral load in acute infection than in chronic HIV-1 infection. The specificities of the antibodies in the immune complexes differed between acute and chronic infection (anti-gp41 Ab in acute infection and anti-gp120 in chronic infection), potentially suggesting different roles in immunopathogenesis for complexes arising at different stages of infection. We also determined the ability of circulating IgG from AHI to bind infectious versus noninfectious virions. Similar to a nonneutralizing anti-gp41 monoclonal antibody (MAb), purified plasma IgG from acute HIV-1 subjects bound both infectious and noninfectious virions. This was in contrast to the neutralizing antibody 2G12 MAb that bound predominantly infectious virions. Moreover, the initial antibody response captured acute HIV-1 virions without selection for different HIV-1 envelope sequences. In total, this study demonstrates that the composition of immune complexes are dynamic over the course of HIV-1 infection and are comprised initially of antibodies that nonselectively opsonize both infectious and noninfectious virions, likely contributing to the lack of efficacy of the antibody response during acute infection. 相似文献
1000.