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   260篇
  免费   11篇
  国内免费   18篇
化学   101篇
力学   40篇
综合类   1篇
数学   53篇
物理学   94篇
  2024年   2篇
  2023年   1篇
  2022年   4篇
  2021年   8篇
  2020年   6篇
  2019年   6篇
  2018年   8篇
  2017年   11篇
  2016年   9篇
  2015年   11篇
  2014年   21篇
  2013年   16篇
  2012年   10篇
  2011年   17篇
  2010年   12篇
  2009年   21篇
  2008年   22篇
  2007年   16篇
  2006年   12篇
  2005年   9篇
  2004年   10篇
  2003年   10篇
  2002年   2篇
  2001年   1篇
  2000年   3篇
  1999年   3篇
  1998年   5篇
  1997年   5篇
  1996年   4篇
  1995年   2篇
  1994年   4篇
  1993年   1篇
  1992年   2篇
  1991年   2篇
  1990年   4篇
  1989年   7篇
  1988年   1篇
  1987年   1篇
排序方式: 共有289条查询结果,搜索用时 0 毫秒
31.
用参麦汤合葡萄糖酸锌片治疗复发性口疮102例,经过3个月治疗,观察到该药能有效地改善临床症状,降低复发率,明显地提高体内锌的水平,与维生素类对照组比较,疗效有显著性差异(P<0.01)。  相似文献   
32.
Combined heat and power (CHP) production is universally accepted as one of the most energy-efficient technologies to produce energy with lower fuel consumption and fewer emissions. In CHP technology, heat and power generation follow a joint characteristic. Traditional CHP production is usually applied in backpressure plants, where the joint characteristic can often be represented by a convex model. Advanced CHP production technologies such as backpressure plants with condensing and auxiliary cooling options, gas turbines, and combined gas and steam cycles may require non-convex models. Cost-efficient operation of a CHP system can be planned using an optimization model based on forecasts for heat load and power price. A long-term planning model decomposes into thousands of single-period models, which can be formulated in the convex case as linear programming (LP) problems, and in the non-convex case as mixed integer programming (MIP) problems.  相似文献   
33.
This experimental research was focused on the investigation of the heat transfer augmentation by various turbulator inserts in gas-heated channels. The work was conducted directly in a convective part of a two fire-tube boiler. The flue ducts were positioned vertically and horizontally for various design applications. Twisted-tape insert (with the twist ratio y=4.12), the straight-tape insert, and the combined turbulator insert (the internal twisted tape with the twist ratio of 180° y=2.16 and an external tape, which spirally winded on an internal tape, with longitudinal pitch H360°=110 mm and the relative height of a tape (rib) e/D0=0.098;0.2) were investigated. The working fluids were the combustion products of light oil fuel and wood pellets. In addition, the experiments were conducted in the two fire-tube boiler without any inserts. Despite of relatively large data scattering obtained in these experiments some qualitative and quantitative conclusions were drawn.  相似文献   
34.
《Comptes Rendus Chimie》2015,18(1):32-38
Pesticides’ biorecalcitrance can be related to the presence of a complex aromatic chains or of specific bonds, such as halogenated bonds, which are the most widespread. In order to treat this pollution at its source, namely in the case of highly concentrated solutions, selective processes, such as electrochemical processes, can appear especially relevant to avoid the possible generation of toxic degradation products and to improve biodegradability in view of a subsequent biological mineralization. 2,4-D was found to be electroactive in oxidation, but not in reduction, and the absence of hydroxyl radicals formation during the electrochemical step was demonstrated, showing that the pretreatment can be considered as a “direct” electrochemical process instead of an advanced electrochemical oxidation process. The presence of several degradation products in the oxidized effluent showed that the pretreatment was not as selective as expected. However, the relevance of the proposed combined process was confirmed since the overall mineralization yield was close to 93%.  相似文献   
35.
Direct administration of drugs and genes to the lungs by pulmonary delivery offers a potential effective therapy for lung cancers.In this study,combined doxorubicin(DOX)and Bcl2 siRNA was employed for cancer therapy using polyethylenimine(PEI)as the carrier of Bcl2 siRNA.Most of the DOX and siRNA possessed high cellular uptake efficiency in B16F10 cells,which was proved by FCM and CLSM analysis. Real-time PCR showed that PEI/Bcl2 siRNA exhibited high gene silencing efficiency with 70% Bcl2 mRNA being knocked down.The combination of DOX and siRNA could enhance the cell proliferation inhibition and the cell apoptosis against B16F10 cells compared to free DOX or PEI/Bcl2 siRNA.Furthermore,the biodistribution of DOX and siRNA via pulmonary administration was studied in mice with B16F10 metastatic lung cancer.The results showed that most of the DOX and siRNA were accumulated in lungs and lasted at least for 3 days,which suggested that combined DOX and siRNA by pulmonary administration may have high anti-tumor effects for metastatic lung cancer treatment in vivo.  相似文献   
36.
In the present study, an attempt has been made to model and analyze a combined footing supporting column, which is to be constructed on very soft soil. In view of small bearing capacity and very large deflections, foundations are constructed after improving the original ground. Here, the ground has been improved by providing the stone columns in the soft soil and on top of this improved ground; a granular fill layer has been placed just below the footing. The footing has been modeled as a beam having finite flexural rigidity. Granular fill layer, soft soil and stone columns have been represented by Pasternak shear layer, Kelvin–Voigt body and the Winkler springs, respectively. Nonlinear behavior of these has been considered by means of hyperbolic constitutive relationships. Governing differential equations for response of the system have been derived and presented in non-dimensional form. These equations have been solved using appropriate boundary conditions by means of an iterative Gauss Elimination technique.  相似文献   
37.
Recently non-proportional deformation has received increased attention from researchers working in the area of experimental and computational modeling of metal deformation. However, most of them are numerical in nature with limited experimental data available, making it further difficult to model non-proportional deformation. In the present work, two-stage uniaxial tests, along with uniaxial cyclic and biaxial tests for different stress ratios, have been performed to evaluate deformation behavior of ultra-low carbon high strength automotive steel. Behaviors like cross-effect and hardening stagnation, which are attributed to the evolution of complex dislocation structures, were observed in this steel. It was also noticed that this steel exhibits tension-compression asymmetry. As for constitutive modeling, a modified asymmetric yield function is proposed to be used with a combined isotropic-kinematic hardening model. Also methods to account for the hardening stagnation during reverse loading and the cross-effect during two-stage deformation are proposed. The resulting constitutive model showed reasonably good agreement with experimental results.  相似文献   
38.
As the blade must have precise size and accurate shape, three-dimensional profile measurement of the blade is very important. In this paper, three-dimensional profile measurement method of the blade based on surface structured light is proposed. A new phase unwrapping method is also proposed. This encoding method combined coding fringe pattern with the four-step phase-shifting method, the coding information is embedded into the phase, which can be used to determine fringe order for absolute phase retrieval. The encoding method is simple and easy to implement, so the phase unwrapping of the blade can be quickly perform. The experimental and simulation results show that the method can achieve a high precision, high speed and low cost three-dimensional profile measurement of the blade.  相似文献   
39.
In this paper, photoelasticity combined with phase shifting technology is used to obtain stress distribution within the stress concentration zone. Both the optical enlarged unwrapping technology and the combined path shear difference technology are provided for evaluating the local stress information. By means of a phase shifting photoelastic experiment of a diametric-compressed disc, the stress components surrounding the local loading zone are determined. The results show not only a good improvement compared with conventional photoelastic analysis but also a good agreement with theoretical data.  相似文献   
40.
An operator splitting method combining finite difference method and finite element method is proposed in this paper by using boundary-fitted coordinate system. The governing equation is split into advection and diffusion equations and solved by finite difference method using boundary-fitted coordinate system and finite element method respectively. An example for which analytic solution is available is used to verified the proposed methods and the agreement is very good. Numerical results show that it is very efficient.  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