全文获取类型
收费全文 | 19692篇 |
免费 | 2391篇 |
国内免费 | 1438篇 |
专业分类
电工技术 | 2586篇 |
综合类 | 2629篇 |
化学工业 | 1958篇 |
金属工艺 | 700篇 |
机械仪表 | 1511篇 |
建筑科学 | 1529篇 |
矿业工程 | 525篇 |
能源动力 | 643篇 |
轻工业 | 808篇 |
水利工程 | 444篇 |
石油天然气 | 1454篇 |
武器工业 | 279篇 |
无线电 | 1804篇 |
一般工业技术 | 1754篇 |
冶金工业 | 532篇 |
原子能技术 | 179篇 |
自动化技术 | 4186篇 |
出版年
2024年 | 92篇 |
2023年 | 249篇 |
2022年 | 532篇 |
2021年 | 621篇 |
2020年 | 663篇 |
2019年 | 521篇 |
2018年 | 506篇 |
2017年 | 638篇 |
2016年 | 727篇 |
2015年 | 816篇 |
2014年 | 1266篇 |
2013年 | 1289篇 |
2012年 | 1534篇 |
2011年 | 1568篇 |
2010年 | 1185篇 |
2009年 | 1235篇 |
2008年 | 1140篇 |
2007年 | 1344篇 |
2006年 | 1153篇 |
2005年 | 982篇 |
2004年 | 837篇 |
2003年 | 729篇 |
2002年 | 660篇 |
2001年 | 542篇 |
2000年 | 488篇 |
1999年 | 362篇 |
1998年 | 308篇 |
1997年 | 278篇 |
1996年 | 226篇 |
1995年 | 197篇 |
1994年 | 177篇 |
1993年 | 139篇 |
1992年 | 124篇 |
1991年 | 77篇 |
1990年 | 64篇 |
1989年 | 69篇 |
1988年 | 45篇 |
1987年 | 22篇 |
1986年 | 20篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 19篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1976年 | 3篇 |
1959年 | 2篇 |
1957年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Alfalfa juice was extracted from plants during the graving phases of the first and second crops. The alfalfa juice was dried and solute concentrations were measured periodically during the process using freezing point depression (FPD) as an indicator. Solute/solvent weight ratios were calculated from the freezing point depression of fresh unconcentrated 'uice extracted from both firsc and second crops. At the time of harvest, tie FPD was a function of this ratio. The first and second crops behaved distinctively different during the drying process, with the second having a larger soluce concentration and a greater FPD at a given moisture content. The appearance of preci itate during the drying process and the general1 large FPD makes this materiay a questionable product for drying vitg low temperature processes. 相似文献
92.
Ariosto B. Jorge Gabriel O. Ribeiro Timothy S. Fisher 《International journal for numerical methods in engineering》2003,56(1):117-144
This work presents two new error estimation approaches for the BEM applied to 2D potential problems. The first approach involves a local error estimator based on a gradient recovery procedure in which the error function is generated from differences between smoothed and non‐smoothed rates of change of boundary variables in the local tangential direction. The second approach involves the external problem formulation and gives both local and global measures of error, depending on a choice of the external evaluation point. These approaches are post‐processing procedures. Both estimators show consistency with mesh refinement and give similar qualitative results. The error estimator using the gradient recovery approach is more general, as this formulation does not rely on an ‘optimal’ choice of an external parameter. This work presents also the use of a local error estimator in an adaptive mesh refinement procedure. This r‐refinement approach is based on the minimization of the standard deviation of the local error estimate. A non‐linear programming procedure using a feasible‐point method is employed using Lagrange multipliers and a set of active constraints. The optimization procedure produces finer meshes close to a singularity and results that are consistent with the problem physics. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
93.
94.
T. Bag 《Information Sciences》2006,176(19):2910-2931
In this paper, definitions of strongly fuzzy convergent sequence, l-fuzzy weakly convergent sequence and l-fuzzy weakly compact set are given in a fuzzy normed linear space. The concepts of fuzzy normal structure, fuzzy non-expansive mapping, uniformly convex fuzzy normed linear space are introduced and fixed point theorems for fuzzy non-expansive mappings are proved. 相似文献
95.
黄化字 《南方冶金学院学报》2005,26(6):55-59
给出了射影几何中关于二阶曲线渐近线的几个等价定义,并探讨了根据不同 定义的二阶曲线渐近线的应用. 相似文献
96.
97.
Baudilio Coto Carmen Martos Jos L. Pea Juan J. Espada María D. Robustillo 《Fuel》2008,87(10-11):2090-2094
Wax precipitation is one of the most important flow assurance problems. Unfortunately, experimental data are very scarce to confirm existing models for prediction of such precipitation problem. This work reports a new experimental method. Multistage fractional wax precipitation was carried out by decreasing the temperature of crude oil. No solvent dilution was used, so the effect of solvent on temperature wax precipitation was avoided. The reproducibility of the method was tested with comparable results. The precipitation curve and the wax appearance temperature were obtained for two crude oils with different chemical nature using the reported method. 相似文献
98.
DGPS在可控震源施工中的应用 总被引:1,自引:1,他引:0
在可控震源施工中,采用DGPS(差分全球卫星定位系统)实施实时点位监控,对保证施工质量、提高生产效率起着积极的作用。本文主要介绍PELTON ADVANCE Ⅲ GPS系统的安装和使用情况。 相似文献
99.
100.
油煤浆的管道输送特性与管路设计原则 总被引:2,自引:0,他引:2
宋新南 《石油学报(石油加工)》2003,19(2):94-100
通过理论分析和管道实验,探讨了油煤浆在工业管道输送中的流变特性、流动状态和阻力特性,得出了油煤浆的物性参数、表观参数、管道阻力参数的测定值和计算公式,并在此基础上探讨了油煤浆管道输送的设计原则,为油煤浆管路的设计提供基础数据、计算方法和一般原则。 相似文献