全文获取类型
收费全文 | 8987篇 |
免费 | 166篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 226篇 |
综合类 | 1篇 |
化学工业 | 2051篇 |
金属工艺 | 263篇 |
机械仪表 | 174篇 |
建筑科学 | 437篇 |
矿业工程 | 88篇 |
能源动力 | 254篇 |
轻工业 | 211篇 |
水利工程 | 49篇 |
石油天然气 | 45篇 |
武器工业 | 1篇 |
无线电 | 1731篇 |
一般工业技术 | 1304篇 |
冶金工业 | 1183篇 |
原子能技术 | 163篇 |
自动化技术 | 978篇 |
出版年
2021年 | 60篇 |
2016年 | 60篇 |
2015年 | 88篇 |
2014年 | 138篇 |
2013年 | 650篇 |
2012年 | 134篇 |
2011年 | 210篇 |
2010年 | 195篇 |
2009年 | 258篇 |
2008年 | 222篇 |
2007年 | 189篇 |
2006年 | 238篇 |
2005年 | 219篇 |
2004年 | 197篇 |
2003年 | 213篇 |
2002年 | 242篇 |
2001年 | 235篇 |
2000年 | 219篇 |
1999年 | 213篇 |
1998年 | 243篇 |
1997年 | 235篇 |
1996年 | 227篇 |
1995年 | 196篇 |
1994年 | 229篇 |
1993年 | 211篇 |
1992年 | 218篇 |
1991年 | 188篇 |
1990年 | 215篇 |
1989年 | 219篇 |
1988年 | 167篇 |
1987年 | 149篇 |
1986年 | 137篇 |
1985年 | 105篇 |
1984年 | 113篇 |
1983年 | 93篇 |
1982年 | 97篇 |
1981年 | 112篇 |
1980年 | 94篇 |
1979年 | 96篇 |
1978年 | 94篇 |
1977年 | 105篇 |
1976年 | 85篇 |
1975年 | 97篇 |
1974年 | 74篇 |
1973年 | 73篇 |
1972年 | 89篇 |
1971年 | 78篇 |
1970年 | 78篇 |
1969年 | 68篇 |
1965年 | 68篇 |
排序方式: 共有9159条查询结果,搜索用时 265 毫秒
961.
Dr. Yun Wang Dr. Shougang Hu Abdul M. Gabisi Jr. Joyce A. V. Er Arthur Pope Gayle Burstein Christopher L. Schardon Dr. Arturo J. Cardounel Dr. Suhendan Ekmekcioglu Dr. Walter Fast 《ChemMedChem》2014,9(4):792-797
Inhibitors of the human enzyme dimethylarginine dimethylaminohydrolase‐1 (DDAH‐1) can raise endogenous levels of asymmetric dimethylarginine (ADMA) and lead to a subsequent inhibition of nitric oxide synthesis. In this study, N5‐(1‐imino‐2‐chloroethyl)‐L ‐ornithine (Cl‐NIO) is shown to be a potent time‐ and concentration‐dependent inhibitor of purified human DDAH‐1 (KI=1.3±0.6 μM ; kinact=0.34±0.07 min?1), with >500‐fold selectivity against two arginine‐handling enzymes in the same pathway. An activity probe is used to measure the “in cell” IC50 value (6.6±0.2 μM ) for Cl‐NIO inhibition of DDAH‐1 artificially expressed within cultured HEK293T cells. A screen of diverse melanoma cell lines reveals that a striking 50/64 (78 %) of melanoma lines tested showed increased levels of DDAH‐1 relative to normal melanocyte control lines. Treatment of the melanoma A375 cell line with Cl‐NIO shows a subsequent decrease in cellular nitric oxide production. Cl‐NIO is a promising tool for the study of methylarginine‐mediated nitric oxide control and a potential therapeutic lead compound for other indications with elevated nitric oxide production, such as septic shock and idiopathic pulmonary fibrosis. 相似文献
962.
963.
964.
Sergio Francisco Santos José de Anchieta Rodrigues Gustavo Henrique Denzin Tonoli Alessandra Etuko Feuzicana de Souza Almeida Holmer Savastano Jr. 《Journal of Materials Science》2014,49(21):7497-7506
The effect of colloidal silica on the hydration reaction of the Portland cement system and its effect on the resulting mechanical properties are not completely understood. Silica nanoparticles can affect the behavior and performance of fiber–cement, such as the calcium–silicate–hydrate gel of the matrix and the fiber–matrix interface bonding. The main objective of this study is to evaluate the effects of various contents of colloidal silica (0, 1.5, 3, 5, and 10 % w/w) on the microstructure and mechanical performance of cement composites reinforced with cellulosic pulp. Fiber–cement composites with unbleached eucalyptus Kraft pulp as the micro-fiber reinforcement were produced by the slurry dewatering technique followed by pressing. The average values of the modulus of rupture of the fiber–cement decreased with increasing colloidal silica content. However, the pullout of the fibers increased significantly in the fiber–cement composites with additions between 3 and 10 % w/w of colloidal silica suspension, as indicated in the scanning electron microscopy images and by the improvement in the energy of fracture values. 相似文献
965.
G. Filippini C. R. Maliska M. Vaz Jr. 《International journal for numerical methods in engineering》2014,98(1):24-43
The literature shows an increasing number of works focused on investigating the behaviour of methods that uses concepts of control volumes in the solution of structural problems. In recent years, new approaches using unstructured meshes have been proposed, most of which addressing new applications and, to a lesser extent, the underling physical perspective. This paper presents a unified approach to the element‐based finite volume method and FEM‐Galerkin within the framework of the finite element space. Numerical examples highlight some accuracy issues associated with the element‐based finite volume method developed in this work. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
966.
Éva Bölcskei Géza Regdon Jr Tamás Sovány Dima Ghanam Klaus Knop Peter Kleinebudde 《Drug development and industrial pharmacy》2014,40(6):762-764
Introduction: The focus of this work was to produce matrix pellets made by extrusion/ spheronization using two types of equipment. The aim was to accomplish the laboratory-scale I process that has been already optimized and accepted with another type of equipment (laboratory-scale II).
Methods: A matrix pellet formulation consisting of MCC, Eudragit NE 30D and diclofenac sodium was used in the two types of equipment. Physico-chemical parameters and the dissolution profiles of the pellets in phosphate buffer pH 6.8 were compared.
Results: Pellets from both processes were similar in shape and tensile strength. They differed in particle size and dissolution profile. This may be contributed to different spheronization conditions. 相似文献
967.
T. Petrisor Jr. R. B. Mos M. Nasui M. S. Gabor A. Augieri G. Celentano D. De Felicis E. Bemporad L. Ciontea T. Petrisor 《Journal of Superconductivity and Novel Magnetism》2014,27(11):2493-2500
In the present paper, we analyze the role of in situ grown BaZrO3 (BZO) inclusions in YBa2Cu3O7?x (YBCO) thin films prepared by chemical solution deposition using a low fluorine coating solution, on the field angle dependence of the critical current density, J c (??), data using the vortex path model. In order to form a coherent picture on the BZO doping influence on the pinning properties of the YBCO matrix, detailed structural analyses performed by X-ray diffraction techniques and microstructural evaluation by transmission electron microscopy are also presented. The evaluation of different contributions to the overall, J c , permitted us to prove the effectiveness of the BZO inclusions acting as isotropic pinning centers, reflected in a uniform component of high relative value with respect to other components. For the studied 10 mol % BZO doping concentration, a threefold increase in the critical current density, J c , of the YBCO host is measured, in self-field at 77 K, corresponding to a value of J c =2.9MA/cm2, whereas a factor 10 is measured at 1 T (J c =0.35 MA/cm2). 相似文献
968.
J. M. A. Pinto J. C. F. Pujol C. A. Cimini Jr 《Fatigue & Fracture of Engineering Materials & Structures》2014,37(1):85-94
This paper introduces a numerical model to estimate fatigue life under step‐stress conditions, using the Weibull and lognormal distributions. The maximum likelihood method was used to estimate the free parameters of the distributions. The model was fitted to an experimental data on fatigue life in the specimens of steel SAE 8620, by using evolutionary computation to optimize the likelihood function. Results are reported on the values of the parameters and their confidence interval. Also, a validation of the model is discussed using analysis of residuals. 相似文献
969.
This study investigated the pollutant emission reduction and demand-side management potential of 16 photovoltaic (PV) systems installed across the US during 1993 and 1994. The US Environmental Protection Agency (EPA) and 11 electric power companies sponsored the project. This article presents results of analyses of each PV system's ability to offset power plant emissions of sulfur dioxide (SO2), nitrogen oxides (NOx), carbon dioxide (CO2) and particulates and to provide power during peak demand hours for the individual host buildings and peak load hours for the utility. The analyses indicate a very broad range in the systems' abilities to offset pollutant emissions, due to variation in the solar resource available and the emission rates of the participating utilities' load following generation plants. Each system's ability to reduce building peak demand was dependent on the correlation of that load to the available solar resource. Most systems operated in excess of 50% of their capacity during building peak load hours in the summer months, but well below that level during winter peak hours. Similarly, many systems operated above 50% of their capacity during utility peak load hours in the summer months, but at a very low level during winter peak hours. 相似文献
970.
An approximate generalized theoretical model is presented for the geometry and energy transfer of a solar thermal collector-central receiver system. Equations permit sizing the receiver, tower, and heliostat field. Cost functions correlate data from Department of Energy studies. Based on a set of assumed conditions, simplified, optimized sizing equations yield the minimum capital cost. The costs of the tower and central receiver will change with plant and equipment cost indices, while heliostat costs are expected to diminish as annual production increases. The heliostat cost is the major cost component even at lowest projected unit cost; therefore optimization tends toward minimum heliostat area. The model permits order-of-magnitude cost estimates to be made very quickly, compared to detailed simulation. 相似文献