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   638篇
  免费   35篇
  国内免费   2篇
  2023年   10篇
  2022年   11篇
  2021年   32篇
  2020年   19篇
  2019年   18篇
  2018年   30篇
  2017年   23篇
  2016年   28篇
  2015年   31篇
  2014年   44篇
  2013年   43篇
  2012年   53篇
  2011年   38篇
  2010年   32篇
  2009年   20篇
  2008年   35篇
  2007年   25篇
  2006年   23篇
  2005年   22篇
  2004年   16篇
  2003年   12篇
  2002年   17篇
  2001年   2篇
  2000年   4篇
  1999年   6篇
  1998年   6篇
  1997年   3篇
  1996年   6篇
  1995年   5篇
  1994年   2篇
  1993年   6篇
  1992年   4篇
  1991年   3篇
  1990年   3篇
  1989年   2篇
  1987年   2篇
  1986年   3篇
  1985年   3篇
  1982年   2篇
  1980年   2篇
  1979年   2篇
  1976年   2篇
  1973年   3篇
  1972年   3篇
  1971年   2篇
  1970年   3篇
  1969年   3篇
  1962年   1篇
  1960年   2篇
  1955年   1篇
排序方式: 共有675条查询结果,搜索用时 375 毫秒
101.
International research is an essential means of reducing health disparities between and within countries and should do so as a matter of global justice. Research funders from high‐income countries have an obligation of justice to support health research in low and middle‐income countries (LMICs) that furthers such objectives. This paper investigates how their current funding schemes are designed to incentivise health systems research in LMICs that promotes health equity. Semi‐structured in‐depth interviews were performed with 16 grants officers working for 11 funders and organisations that support health systems research: the Alliance for Health Policy and Systems Research, Comic Relief, Doris Duke Foundation, European Commission, International Development Research Centre, Norwegian Agency for Development Cooperation, Research Council of Norway, Rockefeller Foundation, UK Department of International Development, UK Medical Research Council, and Wellcome Trust. Thematic analysis of the data demonstrates their funding schemes promote health systems research with (up to) five key features that advance health equity: being conducted with worst‐off populations, focusing on research topics that advance equitable health systems, having LMIC ownership of the research agenda, strengthening LMIC research capacity, and having an impact on health disparities. The different types of incentives that encouraged proposed projects to have these features are identified and classified by their strength (strong, moderate, weak). It is suggested that research funders ought to create and maintain funding schemes with strong incentives for the features identified above in order to more effectively help reduce global health disparities.  相似文献   
102.
Drying of garlic slices in thin-layer have been studied with Infrared (IR) at 0.075, 0.15, 0.225 and 0.3 W cm?2 radiation intensity and 0.75 and 1.25 m s?1 air flow velocity. The results showed increasing in drying rate and decreasing at the time of drying with decreasing air flow velocity and increasing IR radiation intensity. The effective moisture diffusivity (Deff) was obtained using Fick’s diffusion equation and its mean values ranged between 5.83×10?11 and 7.66×10?10 m2 s?1 for all investigated conditions. In addition, a third-order polynomial equation linking the effective moisture diffusivity and moisture content was found. Average activation energy increased with the decrease of IR radiation and increase of air flow velocity. Thirteen different mathematical models were verified with non-linear regression analysis for describing the garlic drying process. Modified Henderson and Pabis model presented the best prediction of the drying of garlic slices.  相似文献   
103.
104.
We examined whether lung inflammatory mediators are increased during exercise and whether pharmacological blockade can prevent exercise-induced arterial hypoxemia (EIAH) in young athletes. Seventeen healthy athletes (9 men, 8 women; age 23 +/- 3 yr) with varying degrees of EIAH completed maximal incremental treadmill exercise tests after administration of fexofenadine, zileuton, and nedocromil sodium or placebo in a randomized double-blind crossover study. Lung function, arterial blood gases, and inflammatory metabolites in plasma, urine, and induced sputum were assessed. Drug administration did not improve EIAH or gas exchange during exercise. At maximal exercise, oxygen saturation fell to 91.4 +/- 2.6% (drug trial) and 91.9 +/- 2.1% (placebo trial) and alveolar-arterial oxygen difference widened to 28.1 +/- 6.3 Torr (drug trial) and 29.3 +/- 5.7 Torr (placebo trial). Oxygen consumption, ventilation, and other exercise variables were similarly unaffected by drug treatment. Although plasma histamine increased with exercise, values did not differ between trials, and urinary leukotriene E(4) and 11beta-prostaglandin F(2alpha) levels were unchanged after exercise. Postexercise sputum revealed no significant changes in markers of inflammation. These results demonstrate that EIAH in young athletes is not attenuated with acute administration of drugs targeting histamine and bioactive lipids. We conclude that airway inflammation is of insufficient magnitude to cause impairments in gas exchange and does not appear to be linked to EIAH in healthy young athletes.  相似文献   
105.
106.
Drought is one of the key restraints to agricultural productivity worldwide and is expected to increase further. Drought stress accompanied by reduction in precipitation pose major challenges to future food safety. Strategies should be develop to enhance drought tolerance in crops like chickpea and wheat, in order to enhance their growth and yield. Drought tolerance strategies are costly and time consuming however, recent studies specify that plant growth promoting rhizobacteria (PGPR) and plant growth regulators (PGRs) can help plants to withstand under harsh environmental condition and enable plants to cope with drought stress. PGPR can act as biofertilizer and bioenhancer for different legumes and non-legumes. The use of PGPR and symbiotic microorganisms, may be valuable in developing strategies to assist water conservation in plants. The use of PGPR has been confirmed to be an ecologically sound way of enhancing crop yields by facilitating plant growth through direct or indirect mechanism. The mechanisms of PGPR for water conservation include secretion of exopolysaccharides, biofilm formation, alternation in phytohormone content, improvement in sugar concentration, enhancing availability of micro- and macronutrients and changes in plant functional traits. Similarly, plant growth regulators (PGRs) are specially noticed in actively growing tissues under stress conditions and have been associated in the control of cell division, embryogenesis, root formation, fruit development and ripening, and reactions to biotic and abiotic stresses and upholding water conservation status in plants. Previous studies also suggest that plant metabolites interact with plant physiology under stress condition and impart drought tolerance. Metabolites like, sugars, amino acids, organic acid and polyols play a key role in drought tolerance of crop plants grown under stress condition. It is concluded from the present study that PGRs in combination with PGPR consortium can be an effective formulation to promote plant growth and maintenance of plant turgidity under drought stress. This review is a compilation of the effect of drought stress on crop plants and described interactions between PGPR/PGRs and plant development, knowledge of water conservation and stress release strategies of PGPR and PGRs and the role of plant metabolites in drought tolerance of crop plants. This review also bridges the gaps that summarizes the mechanism of action of PGPR for drought tolerance of crop plants and sustainability of agriculture and applicability of these beneficial rhizobacteria in different agro-ecosystems under drought stress.  相似文献   
107.
Higher plant hydraulic conductivity (K plant) is vital for plant growth, especially under PEG-induced water deficit stress (PEG-IWDS). Leaf venation architecture is a key determinant of leaf hydraulic conductivity (K leaf) and K leaf is a major component of K plant across different plant species. However, there is little information about (1) varietal difference in leaf vein development in cereal crops, such as rice plants; (2) the effects of PEG-IWDS on leaf vein development; (3) the coordination between leaf venation architecture and K plant as well as K leaf under PEG-IWDS. In the present study, widely cultivated eight rice cultivars were grown hydroponically under well-watered condition (WWC) and PEG-IWDS, simulated by adding 15 % (w/v) PEG6000. Leaf venation architecture, including total longitudinal leaf vein number, leaf vein numbers per unit width (LVNW), vein thickness and leaf mass per area, as well as K plant and K leaf were measured to address above-mentioned questions. The results showed that leaf venation architecture exhibited significant varietal differences and PEG-IWDS significantly increased LVNW while decreased vein thickness. PEG-IWDS suppressed both K plant and K leaf but the decrease was much higher in K plant than K leaf. There was a significant and positive correlation observed between LVNW and K leaf under both WWC and PEG-IWDS but the correlation between LVNW and K plant was only significant under WWC. K leaf was significantly and positively correlated with K plant under WWC but not under PEG-IWDS. It is concluded that K leaf is a major determinant for K plant under WWC but not under PEG-IWDS; therefore, breeding or selecting rice cultivars with high LVNW can improve shoot water supplement under WWC but not under PEG-IWDS condition.  相似文献   
108.
109.
Neurochemical Research - At the present time, treatment of two most common degenerative disorders of elderly population i.e., Type 2 Diabetes Mellitus (T2DM) and Alzheimer’s disease (AD) is a...  相似文献   
110.
A rapid, sensitive, and simple method was developed to detect the sapstain fungi Ophiostoma piceae and O. quercus in stained wood. By using microwave heating for DNA extraction and PCR with internal transcribed spacer-derived-specific primers, detection was feasible within 4 h, even with DNA obtained from a single synnema. This method can easily be extended for the detection of other wood-inhabiting fungi.  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