全文获取类型
收费全文 | 126698篇 |
免费 | 5109篇 |
国内免费 | 2411篇 |
专业分类
电工技术 | 3277篇 |
技术理论 | 2篇 |
综合类 | 4776篇 |
化学工业 | 18920篇 |
金属工艺 | 7308篇 |
机械仪表 | 5887篇 |
建筑科学 | 5179篇 |
矿业工程 | 1857篇 |
能源动力 | 2367篇 |
轻工业 | 6398篇 |
水利工程 | 1922篇 |
石油天然气 | 2842篇 |
武器工业 | 343篇 |
无线电 | 14620篇 |
一般工业技术 | 22034篇 |
冶金工业 | 5023篇 |
原子能技术 | 752篇 |
自动化技术 | 30711篇 |
出版年
2024年 | 200篇 |
2023年 | 862篇 |
2022年 | 1518篇 |
2021年 | 2176篇 |
2020年 | 1569篇 |
2019年 | 1477篇 |
2018年 | 15747篇 |
2017年 | 14758篇 |
2016年 | 11285篇 |
2015年 | 2503篇 |
2014年 | 2498篇 |
2013年 | 2893篇 |
2012年 | 5886篇 |
2011年 | 12437篇 |
2010年 | 10656篇 |
2009年 | 7915篇 |
2008年 | 9137篇 |
2007年 | 9930篇 |
2006年 | 2434篇 |
2005年 | 3069篇 |
2004年 | 2472篇 |
2003年 | 2378篇 |
2002年 | 1656篇 |
2001年 | 1083篇 |
2000年 | 1132篇 |
1999年 | 1049篇 |
1998年 | 888篇 |
1997年 | 743篇 |
1996年 | 682篇 |
1995年 | 533篇 |
1994年 | 425篇 |
1993年 | 284篇 |
1992年 | 244篇 |
1991年 | 224篇 |
1990年 | 170篇 |
1989年 | 155篇 |
1988年 | 110篇 |
1987年 | 85篇 |
1986年 | 55篇 |
1985年 | 49篇 |
1983年 | 37篇 |
1968年 | 43篇 |
1966年 | 43篇 |
1965年 | 44篇 |
1959年 | 36篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
981.
The hydrodynamic and gas mixing characteristics have been determined in a FCC regenerator (0.48 m I.D.x3.4 m high) with FCC
particles. Solids holdup in the dense bed decreases with increasing gas velocity, but it increases in the freeboard region.
The bubble/void fraction increases with an increase along the bed height at a given gas velocity and increases with increasing
gas velocity at a constant bed height. Backmixed tracer gas at the wall region is higher than that at the center region of
the bed. The gas backmixing coefficient decreases with increasing gas velocity. 相似文献
982.
本文用无液接电势电池:Na-ISE(或K-ISE)|(NaCl(mA),KCl(mB),H2O|Cl-ISE同时测定了298.15K,溶液离子强度I:0.1、0.5、1.0、1.5、2.0和2.5mol/kg时,钠电极与氯电极组成的电池和钾电极与氯电极组成的电池的可逆电势值,根据Nernst方程分别求出NaCl-KCl-H2O体系中,NaCl和KCl的平均活度系数。用Pitzer方程拟合两套实验数据,求出两套基本一致的Pitzer混合参数θNa-K和。将混合参数代回Pitzer方程,分别求出另一组分的平均活度系数,计算值与实验值比较,标准偏差分别为:0.0081(NaCl)和0.0073(KCl)。 相似文献
983.
建立基于WEB的教材评价体系,可以及时有效地收集到学生、教师、专家对教材科学的评价意见,并且可以自动生成教材综合评级,为以后的教材编写和教材选取提供科学可靠的重要依据。本文为实现高效、科学、规范、准确的高校教材评价设计开发了一个简易高效的基于WEB的平台,系统基于MVC架构,采用JSP进行功能实现,数据库采用MySQL实现,WEB容器采用TomCat实现。设计中按逻辑划分为:模型(Model)、视图(View)、控制(Control)三个层次。 相似文献
984.
Karl D. Hammond Geoffrey A. Tompsett Scott M. Auerbach W. Curtis Conner 《Journal of Porous Materials》2007,14(4):409-416
We present a non-destructive, reusable apparatus with which to measure physical adsorption isotherms of intact porous membranes.
We developed a two-piece sample container to make reliable sorption measurements of porous membranes, the properties of which
may differ from those of powders due to crystal intergrowth. This novel system employs a resealable container that can be
immersed in a cryogenic bath, into which tubular, planar, or other porous membranes and films may be placed. Detailed sorption
isotherms, including high-resolution adsorption in the low pressure (micropore-filling) region, are shown for MFI-type zeolite
membranes grown on two types and configurations of α-alumina support. 相似文献
985.
抗rHu-IFN-αMcAb亲和常数的测定 总被引:1,自引:0,他引:1
采用ELISA间接法检测抗原-抗体反应系统中游离抗体量的方法,对本实验室制备的5系抗rHu-IFN-αMcAb进行了亲和力测定,获得比较准确的McAb亲和常数。 相似文献
986.
We construct constitutive relations for friction stress, slide stress and collision stress of cohesionless granular flows. We propose that the friction stress and slide stress could be neglected when τc/τe < 0.02, where τc represents the interval time experienced by a given particle between two consecutive binary collisions and τe the particle relaxation time. We applied these constitutive relations to a simulation of solid-liquid flow in an inclined chute and found the simulation results agree with experimental data. 相似文献
987.
针对安徽氯碱化工集团保险粉精馏系统存在的问题进行分析,采取控制措施,将亚硫酸钠加以回收,降低蒸汽消耗,使精馏塔工作状况趋于正常。 相似文献
988.
Guimes Rodrigues Filho Leandra Cardoso Toledo Daniel Alves Cerqueira Rosana Maria Nascimento de Assunção Carla da Silva Meireles Harumi Otaguro Sizue Ota Rogero Ademar Benévolo Lugão 《Polymer Bulletin》2007,59(1):73-81
Summary In this article, cellulose acetate produced through the homogeneous acetylation of sugar cane bagasse cellulose was used to
produce membranes, using poly(ethyleneglycol) 600 (PEG 600) as an admixture. The membranes were characterized using water
flux measurements (Payne’s cup), differential scanning calorimetry (DSC) and neutral red uptake (cytotoxicity). The results
showed that PEG 600 acts as a crystallinity inductor and/or pore former in the cellulose acetate matrix. The induction of
crystallinity is important for this system since it had not been reported on the literature yet. The results also demonstrated
that the studied membranes present a nontoxic behavior. 相似文献
989.
The copolymerization of carbazole (CZ) and 3‐methylthiophene (3MeT) was successfully performed electrochemically in freshly distilled boron trifluoride diethyl etherate by direct anodic oxidation of the monomer mixtures, although the oxidation potentials of CZ and 3MeT were quite different. The electrochemical properties of the copolymers were studied with cyclic voltammetry. The influence of the applied polymerization potential on the synthesis of the copolymers was investigated. The higher potential favored the incorporation of 3MeT units into the copolymers. The insertion of 3MeT units into polycarbazole (PCZ) was helpful in improving the conductivity of PCZ. The novel copolymers had the advantages of both PCZ and poly(3‐methylthiophene), that is, good redox activity, good thermal stability, and high conductivity. The structure and morphology of the copolymers were investigated with ultraviolet–visible, infrared spectroscopy, thermal analysis, and scanning electron microscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1877–1885, 2006 相似文献
990.
Sykes EC Han P Kandel SA Kelly KF McCarty GS Weiss PS 《Accounts of chemical research》2003,36(12):945-953
Adsorbate interactions and reactions on metal surfaces have been investigated using scanning tunneling microscopy. The manners in which adsorbates perturb the surface electronic structure in their vicinity are discussed. The effects these perturbations have on other molecules are shown to be important in overlayer growth. Interactions of molecules with surface steps are addressed, and each molecule's electron affinity is shown to dictate its adsorption sites at step edges. Standing waves emanating from steps are demonstrated to effect transient molecular adsorption up to 40 A away from the step edge. Halobenzene derivatives are used to demonstrate how the surface is important in aligning reactive intermediates. 相似文献