全文获取类型
收费全文 | 1625篇 |
免费 | 9篇 |
国内免费 | 33篇 |
专业分类
教育 | 1145篇 |
科学研究 | 148篇 |
各国文化 | 41篇 |
体育 | 88篇 |
综合类 | 73篇 |
文化理论 | 8篇 |
信息传播 | 164篇 |
出版年
2023年 | 16篇 |
2022年 | 16篇 |
2021年 | 20篇 |
2020年 | 56篇 |
2019年 | 61篇 |
2018年 | 99篇 |
2017年 | 124篇 |
2016年 | 102篇 |
2015年 | 67篇 |
2014年 | 111篇 |
2013年 | 339篇 |
2012年 | 116篇 |
2011年 | 63篇 |
2010年 | 68篇 |
2009年 | 40篇 |
2008年 | 47篇 |
2007年 | 53篇 |
2006年 | 49篇 |
2005年 | 46篇 |
2004年 | 28篇 |
2003年 | 33篇 |
2002年 | 25篇 |
2001年 | 21篇 |
2000年 | 12篇 |
1999年 | 15篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有1667条查询结果,搜索用时 15 毫秒
61.
Bhupendra Pal Singh Shailendra Dwivedi Urmila Dhakad Ramesh Chandra Murthy Vimal Kumar Choubey Apul Goel Satya Narayan Sankhwar 《Indian journal of clinical biochemistry : IJCB》2016,31(1):50-56
Deficiency or excess of certain trace elements has been considered as risk factor for prostate cancer. This study was aimed to detect differential changes and mutual correlations of selected trace elements in prostate cancer tissue versus benign prostatic hyperplasia tissue. Zinc, copper, iron, calcium and selenium were analysed in histologically proven 15 prostate cancer tissues and 15 benign prostatic hyperplasia tissues using atomic absorption spectrophotometer. Unpaired two tailed t test/Mann–Whitney U test and Pearson correlation coefficient were used to compare the level of trace elements, elemental ratios and their interrelations. As compared to benign prostatic tissue, malignant prostatic tissue had significantly lower selenium (p = 0.038) and zinc (p = 0.043) concentrations, a lower zinc/iron ratio (p = 0.04) and positive correlation of selenium with zinc (r = 0.71, p = 0.02) and iron (r = 0.76, p = 0.009). Considerably divergent interrelationship of elements and elemental ratios in prostate cancer versus benign prostatic hyperplasia was noted. Understanding of differential elemental changes and their interdependence may be useful in defining the complex metabolic alterations in prostate carcinogenesis with potential for development of element based newer diagnostic, preventive and therapeutic strategies. Further studies may be needed to elucidate this complex relationship between trace elements and prostate carcinogenesis. 相似文献
62.
滨海地区盐渍土壤对Cd2+的吸附行为 总被引:1,自引:0,他引:1
为评价Cd2+对上海临港新城滨海地区盐渍土壤的影响,通过研究探讨该土壤对Cd2+的吸附行为及吸附机理.结果表明:Cd2+在上海临港新城滨海盐渍土壤中的吸附行为符合Langmuir等温吸附曲线;pH值对土壤中Cd2+的吸附量有明显影响,当pH值介于4~9时吸附量随pH值的增大而急剧增大,当pH值继续增大时吸附量下降并趋于平缓;电解质氯化钠可显著抑制土壤对Cd2+的吸附,随着氯化钠浓度的增大,吸附量先急剧下降,随后趋于平缓;温度升高有利于土壤对Cd2+的吸附,说明上海临港新城滨海盐渍土壤对外源Cd2+的缓冲能力以及土壤中Cd2+的迁移性和活性具有季节性差异. 相似文献
63.
ABSTRACTThis study aimed to investigate the influence of foot strike patterns on the behaviour of the triceps surae muscle-tendon unit, including the Achilles tendon whose length nearly corresponds to force of the triceps surae, and the medial gastrocnemius muscle (MG) during running. Seven male volunteers ran with forefoot and rearfoot strikes at 10, 14 and 18 km h?1 on a treadmill. The MG fascicle length was measured using ultrasonography. The in vivo length of the curved Achilles tendon was quantified by combining ultrasonography with optical motion capture of reflective markers on the right lower limb and an ultrasound probe. The forefoot strike resulted in a significantly shorter MG fascicle length at the initial contact, at Achilles tendon peak elongation, and at toe-off, than the rearfoot strike. The Achilles tendon length at initial contact was greater during the forefoot strike than during the rearfoot strike at 18 km h?1, while its peak elongation was not significantly different during forefoot and rearfoot running. These results indicate that the MG, with a shorter length during forefoot running, manages to address demands for a similar peak force of the triceps surae than during rearfoot running. 相似文献
64.
建立了加强后的金属拱型波纹屋盖模型,利用ANSYS有限元分析软件对加强后的波纹拱进行了荷载作用下几何非线性有限元分析,并与原波纹拱进行了变形与应力的比较。计算结果表明,加强后的波纹拱对约束结构位移变形有较好的效果,且提高了结构的承载能力,这一结论为该结构进行抗风、抗雪等设计提供了有益参考。 相似文献
65.
David T. Hansen 《课程研究杂志》2013,45(6):729-735
In reflections on the Manner in Teaching Project, I focus on four themes: why teaching is an intellectual and moral endeavour; the significance of the school context for understanding the moral dimensions of teaching; the uses and limitations of moral theory in research on teaching; and the centrality of the person in the role of teacher. The 'Manner in Teaching Project' sheds useful light on these themes, including how to examine them systematically. 相似文献
66.
以首钢厂区附近小区域为研究区,采样分析表层土壤Cd、Cu、Pb、Cr、Zn、Ni、Mn、Fe的含量.描述性统计表明:Cd、Pb、Zn、Cu含量受人类活动影响较大;Cd、Cu、Zn存在污染问题,Cd污染最为严重.进一步应用主成分分析、相关分析,并使用GIS工具进行地统计分析,发现8种金属可由3个中等空间自相关的主成分(PCs)反映:PC1包括了与交通及机动车辆关系密切的Cd、Cu、Pb、Cr、Zn;PC2包括了主要来源于首钢厂区的Cr、Mn、Fe;PC3仅有Ni,分布是随成土过程形成的.总体而言,研究区土壤重金属污染来源于交通和机动车辆,需密切关注其对环境的危害及人群的潜在健康风险.本研究对该区域土壤污染风险评价和土地利用规划等起到一定指导作用. 相似文献
67.
This is one of X commentaries on Wu’s ‘Interpretation, autonomy, and transformation: Chinese pedagogic discourse in a cross-cultural perspective’ (JCS, 43(5), 569-590). It highlights the paper’s demystification of Western pedagogic discourse and recovery of the meaning of Chinese traditional pedagogic discourse as a response to the long-lasting debates on the Chinese–Western/traditional–modern dichotomies seen in China’s modernization. However, the paper overlooks the complexity of Chinese pedagogic discourse: it over-emphasizes the formal or linguistic dimension of pedagogic discourse, and presumes the dichotomy of Chinese–Western discourses and the discontinuity of traditional–modern cultures. After elaborating the ends, substances, methods, and teacher roles found in Chinese pedagogic discourses, this study argues that contemporary pedagogic discourses are essentially inhabited in indigenous traditions, and actively entangled with Western discourse. The meaning of Confucian traditional pedagogy should not (and cannot) be ‘recovered’ from the past, but be ‘found’ in the present. 相似文献
68.
The present study explores Greek parents’ views on parental educational involvement and its impact on adolescent scholastic and social development. Specifically, aspects of parental involvement such as the achieved objectives of current parent–school communication, the psychological climate dominating teacher–parent interactions and parents’ suggestions for improvement of current policies and practices are examined. Four hundred and seventy‐five parents participated in the study. Findings showed that family–school communication is believed to be insufficient in Greece, despite the fact that parents tend to: (1) regard their cooperation with teachers as determinative of adolescent academic and psychosocial development; (2) consider teachers to be friendly and caring; and (3) believe that secondary school provides some opportunities for constructive parental involvement. These paradoxes are discussed and explained as a result of radical changes in current social and educational values, principles and objectives. 相似文献
69.
为进一步研究野桑蚕多酚氧化酶的作用机理奠定基础,利用分光光度计检测了金属离子和几种抑制剂对野桑蚕(Bombyx mandarina)多酚氧化酶活性的影响,结果表明:槲皮素和硫脲对该酶的抑制浓度(IC50)分别为0.086 mmol/L和0.092μmol/L,Cu2+对该酶有强烈的抑制作用,而Zn2+、Ca2+和Mg2+有激活作用. 相似文献
70.
冯桂荣 《唐山师范学院学报》2001,23(5):27-30
简述了近十年来用过渡金属配合物(如钯、铜、镍、锆、铁、钛)作催化剂,通过格氏试剂反应进行立体选择性合成的方法和原理。 相似文献