首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   13353篇
  免费   22篇
  国内免费   11篇
教育   10062篇
科学研究   1346篇
各国文化   10篇
体育   738篇
综合类   2篇
文化理论   409篇
信息传播   819篇
  2023年   18篇
  2022年   44篇
  2021年   55篇
  2020年   61篇
  2019年   87篇
  2018年   2262篇
  2017年   2156篇
  2016年   1642篇
  2015年   163篇
  2014年   178篇
  2013年   341篇
  2012年   303篇
  2011年   765篇
  2010年   911篇
  2009年   491篇
  2008年   691篇
  2007年   1187篇
  2006年   139篇
  2005年   448篇
  2004年   484篇
  2003年   382篇
  2002年   167篇
  2001年   43篇
  2000年   46篇
  1999年   22篇
  1998年   29篇
  1997年   32篇
  1996年   11篇
  1995年   11篇
  1994年   12篇
  1993年   9篇
  1992年   12篇
  1991年   18篇
  1990年   15篇
  1989年   10篇
  1988年   8篇
  1987年   6篇
  1986年   9篇
  1985年   10篇
  1984年   11篇
  1983年   6篇
  1982年   5篇
  1981年   7篇
  1980年   6篇
  1979年   10篇
  1978年   5篇
  1977年   4篇
  1975年   11篇
  1974年   8篇
  1968年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
In this work a disposable, parallel microbioreactor (MBR) suitable for screening in batch or continuous mode is presented. The reactor consists of five parallel microchambers made of poly(dimethylsiloxane) bonded to a glass substrate. A grid structure is engraved on each chamber, allowing subsequent morphology imaging. Measurements are recorded over the entire cultivation period with constant parameters, namely, position and focus in the z-axis. The microdevice may be used for either parallel, uni- or multiparametric screening, and overcomes the drawback of gridless microwell plates which require expensive equipment such as an inverted microscope with an automatic stage. To validate the scalability from laboratory scale to microscale, and thus the cultivation protocol in the MBR, the germination of fungal spores (A. ochraceus) is evaluated for two different key magnitudes (pH and temperature) and compared to the results obtained from conventional laboratory scale systems (flasks and agar plates). Information on germination capacity with regard to interspecies' variability allows for optimization of industrial processes as optimal pH and temperature matched to the mesoscopic cultivation systems. The germination conditions therefore remain unaffected inside the MBR, while providing the following advantages: (i) dramatic reduction of medium consumption, (ii) submerged cultivation with constant oxygen supply, (iii) assured low cost and disposability, and (iv) possibility of a continuous cultivation mode.  相似文献   
972.
We examined differences in anthropometry and training between 64 Triple Iron ultra-triathletes competing over 11.4 km swimming, 540 km cycling, and 126.6 km running, and 71 Ironman triathletes competing over 3.8 km swimming, 180 km cycling, and 42.2 km running. The association of anthropometry and training with race time was investigated using multiple linear regression analysis. The Triple Iron ultra-triathletes were smaller (P < 0.05), had shorter limbs (P < 0.05), a higher body mass index (P < 0.05), and larger limb circumferences (P < 0.01) than the Ironman triathletes. The Triple Iron ultra-triathletes trained for more hours (P < 0.01) and covered more kilometres (P < 0.01), but speed in running during training was slower compared with the Ironman triathletes (P < 0.01). For Triple Iron ultra-triathletes, percent body fat (P = 0.022), training volume per week (P < 0.0001), and weekly kilometres in both cycling (P < 0.0001) and running (P < 0.0001) were related to race time. For Ironman triathletes, percent body fat (P < 0.0001), circumference of upper arm (P = 0.006), and speed in cycling training (P = 0.012) were associated with total race time. We conclude that both Triple Iron ultra-triathletes and Ironman triathletes appeared to profit from low body fat. Triple Iron ultra-triathletes relied more on training volume in cycling and running, whereas speed in cycling training was related to race time in Ironman triathletes.  相似文献   
973.

BISp-Informationen

BISp Informationen  相似文献   
974.

BISp-Informationen

Informationen des Bundesinstituts für Sportwissenschaft (BISp)  相似文献   
975.
976.
Clinicians request a large part of measurements of biological quantities that clinical laboratories perform for diagnostic, prognostic or diseases monitoring purposes. Thus, laboratories need to provide patient’s results as reliable as possible. Metrological concepts like measurement uncertainty and metrological traceability allow to know the accuracy of these results and guarantee their comparability over time and space. Such is the importance of these two parameters that the estimation of measurement uncertainty and the knowledge of metrological traceability is required for clinical laboratories accredited by ISO 15189:2012. Despite there are many publications or guidelines to estimate the measurement uncertainty in clinical laboratories, it is not entirely clear what information and which formulae they should use to calculate it. On the other hand, unfortunately, there are a small number of clinical laboratories that know and describe the metrological traceability of their results, even though they are aware of the lack of comparability that currently exists for patient’s results. Thus, to try to facilitate the task of clinical laboratories, this review aims to provide a proposal to estimate the measurement uncertainty. Also, different suggestions are shown to describe the metrological traceability. Measurement uncertainty estimation is partially based on the ISO/TS 20914:2019 guideline, and the metrological traceability described using the ISO 17511:2020. Different biological quantities routinely measured in clinical laboratories are used to exemplify the proposal and suggestions.  相似文献   
977.
978.
979.
This article explores the way in which the World Bank has worked effectively with China in higher education. It investigates whether or not the cooperation between the two has changed in line with their changing relationship. More specifically, it discusses whether the World Bank’s China agenda reflects the reform package of socio-institutional neoliberalism which the World Bank has tended to promote worldwide in the era of the Post-Washington Consensus, and how China’s higher education reform has been influenced by the agenda. The article argues that as China is transferring its role from that of a recipient country to that of a donor country, it is increasingly important to position itself as a global player. Other than mastering the game rules of the international community, China should also expand its influence within and through these major international organizations.  相似文献   
980.
The vapor-liquid equilibrium(VLE) properties for the binary and ternary mixtures of CH4,C2H4 and isoC4H10 are of great importance in the recovery of ethylene from mixture containing CH4 and C2H4 with iso-C4H10 as solvent.Hence,Gibbs ensemble Monte Carlo(GEMC) simulations were used to estimate vapor-liquid equilibrium for the binary and ternary mixtures of CH4,C2H4 and iso-C4H10 with the united atom potential NERD model.The selected simulation conditions are based on the experiment in the literature.The results of this work were shown to be in satisfactory agreement with available experimental data and predictions of Peng-Robinson equation of state.The structure of simulated liquid phase is also characterized by radial distribution function(RDF),which contributes to further understanding of the VLE curve of these systems.RDF is not sensitive to the pressure and temperature range.With the increase of pressure or the decrease of temperature,the molecules tend to gather together.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号