全文获取类型
收费全文 | 173篇 |
免费 | 10篇 |
国内免费 | 4篇 |
专业分类
化学 | 58篇 |
力学 | 36篇 |
综合类 | 2篇 |
数学 | 28篇 |
物理学 | 63篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 15篇 |
2013年 | 9篇 |
2012年 | 9篇 |
2011年 | 8篇 |
2010年 | 9篇 |
2009年 | 13篇 |
2008年 | 14篇 |
2007年 | 8篇 |
2006年 | 11篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 7篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1985年 | 1篇 |
1982年 | 2篇 |
排序方式: 共有187条查询结果,搜索用时 15 毫秒
11.
This work investigated the effect of infusion of a self-made ultrasound contrast agent with long persistence (named ZHIFUXIAN) on rat right ventricular pressure and made a preliminary evaluation on the relative safety of the novel microbubbles. Normal saline, SonoVue and ZHIFUXIAN were injected through caudal vein at the total volume of 0.5 ml for each injection. The right ventricular systolic pressure (RVSP) and end-diastolic pressure (RVEDP) were monitored and the changes of the pressure were compared with baseline readings. RVSP increased when saline, SonoVue or ZHIFUXIAN were injected, the greatest change being after SonoVue (about 2 mm Hg), but there was no statistical significance compared with baseline (P > 0.05). There was no significant difference in RVSP between saline, SonoVue and ZHIFUXIAN at any time point. Also, there was no significant difference in RVEDP between groups at each time point and between different time points in each group. The results indicate that the self-made microbubbles effect on right ventricular hemodynamics is equivalent to that of normal saline at the same volume needed for effective enhanced imaging, demonstrating that it does not produce changes in right ventricular blood pressure under the study conditions. Pathological examination also showed it had no obvious influence on lung, liver and kidney. 相似文献
12.
保险公司被允许将部分资金投入风险市场,这样保险公司经营的风险来自于未来实际发生索赔的不确定性和投资收益的不确定性。研究了由经典的Cramer-Lundberg模型与按照几何布朗运动股票价格变动的一个风险模型,获得了三种资产分配情况下股票价格波动对赤字发生概率下界的影响。 相似文献
13.
14.
15.
上池西外坡岩体稳定是十三陵抽水蓄能电站主要的地质工程问题之一,由于受到倾向池外的数条缓倾角断层以及不良的岩体结构控制,存在着滑动位移、变形失稳的可能性,电站的安全运行受到潜在的威胁。因此对西外坡岩体进行稳定分析,并进行补强处理是必要的。 相似文献
16.
J. Burgain J. Scher G. Francius F. Borges M. Corgneau A.M. Revol-Junelles C. Cailliez-Grimal C. Gaiani 《Advances in colloid and interface science》2014
This review gives an overview of the importance of interactions occurring in dairy matrices between Lactic Acid Bacteria and milk components. Dairy products are important sources of biological active compounds of particular relevance to human health. These compounds include immunoglobulins, whey proteins and peptides, polar lipids, and lactic acid bacteria including probiotics. A better understanding of interactions between bioactive components and their delivery matrix may successfully improve their transport to their target site of action. Pioneering research on probiotic lactic acid bacteria has mainly focused on their host effects. However, very little is known about their interaction with dairy ingredients. Such knowledge could contribute to designing new and more efficient dairy food, and to better understand relationships between milk constituents. The purpose of this review is first to provide an overview of the current knowledge about the biomolecules produced on bacterial surface and the composition of the dairy matter. In order to understand how bacteria interact with dairy molecules, adhesion mechanisms are subsequently reviewed with a special focus on the environmental conditions affecting bacterial adhesion. Methods dedicated to investigate the bacterial surface and to decipher interactions between bacteria and abiotic dairy components are also detailed. Finally, relevant industrial implications of these interactions are presented and discussed. 相似文献
17.
The falsification of a hybrid system aims at finding trajectories that violate a given safety property. This is a challenging problem, and the practical applicability of current falsification algorithms still suffers from their high time complexity. In contrast to falsification, verification algorithms aim at providing guarantees that no such trajectories exist. Recent symbolic reachability techniques are capable of efficiently computing linear constraints that enclose all trajectories of the system with reasonable precision. In this paper, we leverage the power of symbolic reachability algorithms to improve the scalability of falsification techniques. Recent approaches to falsification reduce the problem to a nonlinear optimization problem. We propose to reduce the search space of the optimization problem by adding linear state constraints obtained with a reachability algorithm. An empirical study of how varying abstractions during symbolic reachability analysis affect the performance of solving a falsification problem is presented. In addition, for solving a falsification problem, we propose an alternating minimization algorithm that solves a linear programming problem and a non-linear programming problem in alternation finitely many times. We showcase the efficacy of our algorithms on a number of standard hybrid systems benchmarks demonstrating the performance increase and number of falsifyable instances. 相似文献
18.
Diisopropyl fluorophosphate (DFP), a volatile highly toxic enzyme inhibitor, in buffer (pH 3, pH 5, pH 7, pH 9, pH 11, Hank’s,
Dulbecco’s, PBS, TBE, and HEPES) or water (10 mM), in DMF solution (200 mM), and bulk quantities can be degraded by adding
1M NaOH. The DFP was completely degraded, as determined by enzymatic assay, and the final reaction mixtures were not mutagenic. 相似文献
19.
20.
A company allocates a resource between safety effort and production. The government earns taxes on production. The disaster probability is modeled as a contest between the disaster magnitude and the two players’ safety efforts. The model illustrates that safety efforts are strategic substitutes and inverse U shaped in the disaster magnitude. The company’s safety effort increases, and the government’s safety effort decreases, in taxation. Taxation can ameliorate companies’ free riding on governments’ safety efforts. With sufficiently large production, the government prefers, and the company does not prefer, raising taxation above 0%. For the government, an upper limit usually exists above which taxation cannot be profitably increased. The model shows how both or no players exert safety efforts when the disaster magnitude is small and large respectively, and how they free ride on each other’s safety efforts when the disaster magnitude is intermediate. The company free rides when the unit production cost is low so that the large profits outweigh the negative impact of the disaster. With endogenized taxation determined by the government, the tax rate decreases in the disaster magnitude, the unit production cost, the government’s unit cost of safety effort, and how the company is negatively affected by the disaster. The tax rate increases in the company’s resource and how the government is negatively affected by the disaster. The tax rate is weakly U shaped in the company’s unit safety effort. The model is illustrated with numerical examples and with the oil spill disasters by BP in 2010 and by Exxon Valdez in 1989. 相似文献