全文获取类型
| 收费全文 | 1261篇 |
| 免费 | 8篇 |
| 国内免费 | 2篇 |
专业分类
| 教育 | 516篇 |
| 科学研究 | 592篇 |
| 各国文化 | 14篇 |
| 体育 | 51篇 |
| 文化理论 | 20篇 |
| 信息传播 | 78篇 |
出版年
| 2019年 | 18篇 |
| 2018年 | 25篇 |
| 2017年 | 13篇 |
| 2016年 | 9篇 |
| 2014年 | 23篇 |
| 2013年 | 237篇 |
| 2011年 | 15篇 |
| 2010年 | 12篇 |
| 2009年 | 14篇 |
| 2008年 | 14篇 |
| 2007年 | 9篇 |
| 2006年 | 12篇 |
| 2005年 | 18篇 |
| 2004年 | 18篇 |
| 2003年 | 12篇 |
| 2002年 | 9篇 |
| 2001年 | 13篇 |
| 2000年 | 11篇 |
| 1996年 | 12篇 |
| 1995年 | 10篇 |
| 1994年 | 9篇 |
| 1993年 | 15篇 |
| 1990年 | 13篇 |
| 1989年 | 8篇 |
| 1983年 | 8篇 |
| 1981年 | 12篇 |
| 1978年 | 16篇 |
| 1977年 | 10篇 |
| 1975年 | 7篇 |
| 1948年 | 13篇 |
| 1944年 | 7篇 |
| 1930年 | 20篇 |
| 1929年 | 28篇 |
| 1928年 | 33篇 |
| 1927年 | 32篇 |
| 1926年 | 30篇 |
| 1925年 | 52篇 |
| 1924年 | 33篇 |
| 1923年 | 34篇 |
| 1922年 | 11篇 |
| 1921年 | 15篇 |
| 1920年 | 28篇 |
| 1919年 | 13篇 |
| 1918年 | 12篇 |
| 1915年 | 8篇 |
| 1871年 | 7篇 |
| 1870年 | 7篇 |
| 1868年 | 15篇 |
| 1867年 | 9篇 |
| 1865年 | 7篇 |
排序方式： 共有1271条查询结果，搜索用时 15 毫秒
101.
102.
103.
104.
105.
106.
Sarah B. Rosenbach S. Henry Sherwood V. Paul Poteat Hirokazu Yoshikawa Jerel P. Calzo 《Psychology in the schools》2022,59(1):152-180
In a time of unprecedented polarization in the United States, particularly concerning immigration, schools are uniquely positioned to help students understand the consequences of drastic policy changes. Beyond formal settings such as social studies classes, extracurricular activities may be important for fostering discussions about sociohistorical and policy issues. Such discussions could serve to empower youth from marginalized populations and raise their critical consciousness. Yet the potential outcomes of discussions in these extracurricular settings have not been studied in depth. Using data collected in school-based Gender-and-Sexuality-Alliances (GSAs) throughout Massachusetts during the periods leading up to and following the 2016 US Presidential election, we examined whether discussions of immigration issues in GSAs were associated with greater empowerment and critical consciousness among 580 youth (M Age = 15.59, range = 10–20 years). Multilevel structural equation models showed that the frequency with which youth discussed immigration, relative to their fellow members, was positively associated with residualized change in perceived peer validation for members in general and with residualized change in hope for immigrant-origin members only. Contrary to our expectations, we did not find significant associations for critical consciousness. Findings suggest how groups addressing issues of equity and justice can promote members' empowerment. 相似文献
107.
Electric field-driven separation and purification techniques, such as isoelectric focusing (IEF) and isotachophoresis, generate heat in the system that can affect the performance of the separation process. In this study, a new mathematical model is presented for IEF that considers the temperature rise due to Joule heating. We used the model to study focusing phenomena and separation performance in a microchannel. A finite volume-based numerical technique is developed to study temperature-dependent IEF. Numerical simulation for narrow range IEF (6 < pH < 10) is performed in a straight microchannel for 100 ampholytes and two model proteins: staphylococcal nuclease and pancreatic ribonuclease. Separation results of the two proteins are obtained with and without considering the temperature rise due to Joule heating in the system for a nominal electric field of 100 V/cm. For the no Joule heating case, constant properties are used, while for the Joule heating case, temperature-dependent titration curves and thermo-physical properties are used. Our numerical results show that the temperature change due to Joule heating has a significant impact on the final focusing points of proteins, which can lower the separation performance considerably. In the absence of advection and any active cooling mechanism, the temperature increase is the highest at the mid-section of a microchannel. We also found that the maximum temperature in the system is a strong function of the ΔpK? value of the carrier ampholytes. Simulation results are also obtained for different values of applied electric fields in order to find the optimum working range considering the simulation time and buffer temperature. Moreover, the model is extended to study IEF in a straight microchip where pH is formed by supplying H+ and OH−, and the thermal analysis shows that the heat generation is negligible in ion supplied IEF. 相似文献
109.
110.
Access to government information in electronic form is essential to the realization of a civil society, democratization, and a rule of law. Freedom of information issues are centrally important in countries around the world, and the Internet's World Wide Web offers the potential to provide freedom of information at low cost. Achieving a sound information policy to promote open government requires constant vigilance by those who care about the goal. The greatest threat is state sponsored monopoly. State sponsored monopolies are inimical to open government and rule of law because they open the possibility of censorship, because they raise prices and increase cost, and because they deprive the public of new technology developments. Agencies should never seek to restrict redissemination or to prescribe prices at which information may be distributed to redisseminated. Copyright law may be interpreted to exclude the possibility of copyright in basic public information. Finally, the proposed database protection treaty now pending before the World Intellectual Property Organization should be opposed, unless drafters add a compulsory license provision to mandate multiple sources and channels for public information locked up by intellectual property and database rights. 相似文献