全文获取类型
收费全文 | 281452篇 |
免费 | 29714篇 |
国内免费 | 10657篇 |
学科分类
工业技术 | 321823篇 |
出版年
2024年 | 976篇 |
2023年 | 3201篇 |
2022年 | 6267篇 |
2021年 | 8772篇 |
2020年 | 7703篇 |
2019年 | 8309篇 |
2018年 | 9511篇 |
2017年 | 10507篇 |
2016年 | 10389篇 |
2015年 | 11833篇 |
2014年 | 14348篇 |
2013年 | 17736篇 |
2012年 | 17220篇 |
2011年 | 17965篇 |
2010年 | 16441篇 |
2009年 | 16054篇 |
2008年 | 15625篇 |
2007年 | 14803篇 |
2006年 | 13845篇 |
2005年 | 11737篇 |
2004年 | 9490篇 |
2003年 | 9309篇 |
2002年 | 10088篇 |
2001年 | 9033篇 |
2000年 | 7125篇 |
1999年 | 5426篇 |
1998年 | 3757篇 |
1997年 | 3161篇 |
1996年 | 2783篇 |
1995年 | 2471篇 |
1994年 | 2037篇 |
1993年 | 1645篇 |
1992年 | 1544篇 |
1991年 | 1330篇 |
1990年 | 1289篇 |
1989年 | 1135篇 |
1988年 | 1032篇 |
1987年 | 935篇 |
1986年 | 815篇 |
1985年 | 778篇 |
1984年 | 748篇 |
1981年 | 690篇 |
1979年 | 757篇 |
1978年 | 786篇 |
1977年 | 753篇 |
1976年 | 771篇 |
1975年 | 719篇 |
1974年 | 726篇 |
1973年 | 726篇 |
1972年 | 710篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
设计了基于Web的3D模型浏览与交互系统,主要采用基于WebGL的第三方库Three.js来实现。该系统的建立主要包括场景的构建、场景的交互控制和模型的云存储。模型是场景构建的前提,用户可从外部导入所需模型或利用系统自带的简单模型进行模型的构建。场景交互技术主要包括模型的平移、旋转、缩放、拾取、剖切、3D动画模型的播放以及信息的显示等。模型的云存储是指用户可以通过登录账户将3D模型存储到服务器,日后需要时直接从服务器中加载即可。 相似文献
3.
4.
Hao Li Pengcheng Zhang Shengquan Yu Hongyu Yang Bin Tang Fuhai Li Shuren Zhang 《Ceramics International》2019,45(9):11639-11647
Mg2(Ti1-xSnx)O4 (x?=?0–1) ceramics were prepared through conventional solid-state method. This paper focused on the dependence of microwave dielectric properties on crystal structural characteristics via crystal structure refinement, Raman spectra study and complex chemical bond theory. XRD spectrums delineated the phase information of a spinel structure, and structural characteristic of these compositions were achieved with the help of Rietveld refinements. Raman spectrums were used to depict the correlations between vibrational phonon modes and dielectric properties. The variation of permittivity is ascribed to the Mg2(Ti1-xSnx)O4 average bond covalency. The relationship among the B-site octahedral bond energy, tetrahedral bond energy and temperature coefficient are discussed by defining on the change rate of bond energy and the contribution rate of octahedral bond energy. The quality factor is affected by systematic total lattice energy, and the research of XPS patterns illustrated that oxygen vacancies can be effectively restrained in rich oxygen sintering process. Obviously, the microwave dielectric properties of Mg2(Ti1-xSnx)O4 compounds were obtained (= 12.18, ?=?170,130?GHz, ?=??53.1?ppm/°C, x?=?0.2). 相似文献
5.
P. B. Lovyrev A. I. Lavrov V. A. Babkin A. N. Aminov S. M. Melekhin Yu. P. Kazantsev P. M. Korol’kov 《Metallurgist》2006,50(3-4):152-157
Specifications require that all the welds in 12-m-diam. decomposers with a capacity of 3600 m3 be subjected to high-temperature tempering before going into service in order to alleviate the stresses from the welding
operation. Specialists at the organizations VNIIPTkhimnefteapparatury and VNIImontazhspetsstroi have proposed out-of-furnace
volumetric (complete) of the assembled decomposer with the use of special heaters. The use of this heating method has shortened
assembly operations while providing the welds with a highquality heat treatment and reducing the stresses overall (including
welding stresses, stresses from assembly of the decomposer, etc.) The technology ensures uniform heating of the housing of
the decomposer and provides for close control over the process. The experience gained in heat-treating decomposers can also
be used in the construction of other containers that come into contact with corrosive media.
__________
Translated from Metallurg, No. 3, pp. 61–64, March, 2006. 相似文献
6.
N. I. Nikolaikin E. Yu. Barzilovich N. E. Nikolaikina 《Chemical and Petroleum Engineering》2006,42(5-6):332-338
The paper discusses optimal control of ecosystem state for observation of a generalized monotonically varying random parameter.
A model is proposed for the controlled vector random process, whose components are assigned acceptable ranges and the observations
are performed discretely.
__________
Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 6, pp. 40–44, June, 2006. 相似文献
7.
This study was undertaken to develop a modified atmosphere package to control microbial growth in ready‐to‐eat (RTE) products stored at ambient temperature. Ethanol and/or limonene associated with modified atmosphere (CO2 : O2 : N2 = 30% : 5% : 65%) was used to inhibit the growth of total air‐borne microorganisms and Escherichia coli in RTE products stored at 25°C. The results indicated that 0.05% ethanol vapour in the headspace was effective to inhibit the growth of air‐borne microorganisms and E. coli at 25°C for 72 h in a model study, and the effectiveness was related to ethanol content. Both 73 ppm limonene and 0.05% ethanol vapour enhanced the bacteriostatic effect of modified atmosphere in RTE sushi roll products, and no off‐flavour was detected using this formulated gas; however, no significant inhibitory effect was observed for RTE cold noodle products. This study concludes that combinations of carbon dioxide, ethanol or limonene vapours are effective to inhibit microbial growth in RTE food at ambient temperature, and the outcome may be due to the hurdle effect. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
8.
The basic methods of verifying continuous automatic belt weighers are described. A comparative analysis of these methods on the basis of experimental studies is made and ways of implementing the results in industry are recommended. 相似文献
9.
Yu. I. Golovin D. V. Lopatin R. K. Nikolaev A. V. Umrikhin 《Technical Physics Letters》2004,30(5):426-428
The effect of crystal orientation on the photogeneration of free charge carriers was studied for C60 single crystals in a weak magnetic field. The photoconductivity sharply depends on the orientation of magnetic field with
respect to the crystallographic directions, showing a 5–8% increase for seven axes of the C60 crystal. 相似文献
10.