全文获取类型
收费全文 | 81092篇 |
免费 | 7829篇 |
国内免费 | 4688篇 |
专业分类
电工技术 | 5336篇 |
技术理论 | 5篇 |
综合类 | 6414篇 |
化学工业 | 13048篇 |
金属工艺 | 4350篇 |
机械仪表 | 4841篇 |
建筑科学 | 7482篇 |
矿业工程 | 2305篇 |
能源动力 | 2414篇 |
轻工业 | 6493篇 |
水利工程 | 1565篇 |
石油天然气 | 3909篇 |
武器工业 | 586篇 |
无线电 | 9630篇 |
一般工业技术 | 9134篇 |
冶金工业 | 3328篇 |
原子能技术 | 1088篇 |
自动化技术 | 11681篇 |
出版年
2024年 | 417篇 |
2023年 | 1518篇 |
2022年 | 2653篇 |
2021年 | 3652篇 |
2020年 | 2740篇 |
2019年 | 2485篇 |
2018年 | 2582篇 |
2017年 | 2835篇 |
2016年 | 2473篇 |
2015年 | 3313篇 |
2014年 | 4070篇 |
2013年 | 4714篇 |
2012年 | 5088篇 |
2011年 | 5337篇 |
2010年 | 4997篇 |
2009年 | 4650篇 |
2008年 | 4458篇 |
2007年 | 4187篇 |
2006年 | 4066篇 |
2005年 | 3383篇 |
2004年 | 2705篇 |
2003年 | 3160篇 |
2002年 | 4023篇 |
2001年 | 3411篇 |
2000年 | 2102篇 |
1999年 | 1825篇 |
1998年 | 1148篇 |
1997年 | 1054篇 |
1996年 | 1030篇 |
1995年 | 825篇 |
1994年 | 682篇 |
1993年 | 456篇 |
1992年 | 376篇 |
1991年 | 241篇 |
1990年 | 195篇 |
1989年 | 162篇 |
1988年 | 132篇 |
1987年 | 80篇 |
1986年 | 73篇 |
1985年 | 55篇 |
1984年 | 36篇 |
1983年 | 28篇 |
1982年 | 20篇 |
1981年 | 17篇 |
1980年 | 23篇 |
1979年 | 15篇 |
1962年 | 42篇 |
1961年 | 39篇 |
1960年 | 16篇 |
1959年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
A semi-Markov model is constructed that describes an arbitrarily structured multicomponent technological system and takes
into account its calendar maintenance. Using an aggregation algorithm, approximate values of stationary reliability characteristics
and an optimal term of maintenance work are determined for the system.
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 69–86, March–April 2006. 相似文献
152.
153.
Ye Yuan Yanfang Li Cameron B.D. Relue P. 《IEEE journal of selected topics in quantum electronics》2007,13(6):1671-1679
In this study, we wanted to see if fluorescence anisotropy could be used to detect changes in metabolism in cells with significant light scattering and absorption properties. Fluorescence anisotropy measurements of nicotinamide adenine dinucleotide (NADH) were performed with human melanocytes and melanoma cell lines. To demonstrate the feasibility of using fluorescence anisotropy for detecting metabolic changes, the electron transport chain was blocked using rotenone, inducing an accumulation of intracellular NADH. Total fluorescence increased in all cells as a result of rotenone treatment. Fluorescence anisotropy decreased in the rotenone-treated cells relative to the controls, suggesting an increased ratio of free to protein-bound NADH in the treated cells. In general, the fluorescence anisotropy of the melanocytes was significantly higher than that of the melanoma cell lines. Reflectance spectroscopy showed that the differences in fluorescence anisotropy between the cell types were not due to differences in scattering and absorption properties. Intrinsic cellular NADH fluorescence was experimentally extracted by ratioing polarized fluorescence to polarized reflectance. NADH binding, measured as the ratio of fluorescence intensity at 430 and 465 nm, showed more protein-bound NADH in the melanocytes than in the melanoma cells, consistent with the fluorescence anisotropy measurements. 相似文献
154.
155.
湖北省田关水利工程管理处自来水厂(简称田关水厂),位于潜江市城区西郊,坐落在东荆河与田关河交汇处,是湖北省潜江市的最大乡镇水厂.现日供水规模为1.5t。田关水厂按“一次性规划,分三期实施”的原则进行设计,现已完成二期工程建设。田关水厂多年良好运行经验表明.从供水服务区需求出发.设计出适合经济社会发展和与当地资源环境条件相协调的水厂,是水厂长期高效运营的关键。 相似文献
156.
Understanding how the structure of the unit-cell affects the cryogenic performance of a Si power Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is an important step toward optimizing of the device for cryogenic operations. In this paper, numerical simulations of the Si power Double Diffused MOSFET’ (DMOS) are performed at room temperature and cryogenic temperatures. Physically based models for temperature dependent silicon properties are employed in the simulations. The performances of power DMOS’ with various unit-cell structures are compared at both room temperature and low temperatures. The effect of the cell structure on the on-resistance and breakdown voltage of the device are analyzed. The simulation results suggest that the device optimized for room temperature operation can be further optimized at cryogenic temperatures. 相似文献
157.
This paper presents a new method for the direct and accurate evaluation of strongly singular integrals in the sense of Cauchy principal values and weakly singular integrals over quadratic boundary elements in three-dimensional stress analysis and quadratic internal cells in two-dimensional elastoplastic analysis by the boundary element method. A quadratic triangle polar co-ordinate transformation technique is applied to reduce the order of singularity of the singular integrals. Next, a form of Stokes' theorem is introduced in order to remove the singularity in the Cauchy principal value integrals; therefore, the evaluation of these integrals can be carried out by standard Gaussian quadrature. Numerical examples of 2-D elastoplastic problems and a 3-D elastic problem show the effectiveness and efficiency of the method. 相似文献
158.
159.
本文导出了线性波浪作用于上部可渗透的直立刚性圆柱体上的水动力的解析解。在线性有势流的假定下,用特征函数展开方法求出了内部和外部流场的解。给出了不同波浪要素及结构尺寸参数下的数值结果。由结果可知,提高可渗透性可以有效消减波幅。 相似文献
160.
A coupled-mode equation for anisotropic waveguide systems of arbitrary cross section and general dielectric distribution is derived. Numerical results comparing the exact calculations to those of the method of Hardy et al. (Opt. Lett., vol.11, 742-4, 1986) show that the same accuracy can be obtained not only for TE, but also for TM mode coupling in the case of anisotropic waveguides, and the improved coupled-mode theory is applicable to the situation when moderately strong coupling occurs under the condition where the edge-to-edge separation of two coupled guides D 2 is about 0.1 μm 相似文献