全文获取类型
收费全文 | 187482篇 |
免费 | 2351篇 |
国内免费 | 1639篇 |
专业分类
电工技术 | 2709篇 |
综合类 | 2453篇 |
化学工业 | 22117篇 |
金属工艺 | 10207篇 |
机械仪表 | 6204篇 |
建筑科学 | 4283篇 |
矿业工程 | 723篇 |
能源动力 | 4131篇 |
轻工业 | 9729篇 |
水利工程 | 1977篇 |
石油天然气 | 1018篇 |
武器工业 | 15篇 |
无线电 | 25240篇 |
一般工业技术 | 38067篇 |
冶金工业 | 28104篇 |
原子能技术 | 1640篇 |
自动化技术 | 32855篇 |
出版年
2022年 | 474篇 |
2021年 | 726篇 |
2020年 | 545篇 |
2019年 | 698篇 |
2018年 | 15510篇 |
2017年 | 14395篇 |
2016年 | 11100篇 |
2015年 | 1564篇 |
2014年 | 1771篇 |
2013年 | 4972篇 |
2012年 | 5762篇 |
2011年 | 13259篇 |
2010年 | 11362篇 |
2009年 | 9299篇 |
2008年 | 10675篇 |
2007年 | 11840篇 |
2006年 | 3903篇 |
2005年 | 4587篇 |
2004年 | 4368篇 |
2003年 | 4240篇 |
2002年 | 3260篇 |
2001年 | 3094篇 |
2000年 | 2910篇 |
1999年 | 3160篇 |
1998年 | 9513篇 |
1997年 | 6203篇 |
1996年 | 4837篇 |
1995年 | 3195篇 |
1994年 | 2817篇 |
1993年 | 2761篇 |
1992年 | 1663篇 |
1991年 | 1635篇 |
1990年 | 1531篇 |
1989年 | 1341篇 |
1988年 | 1187篇 |
1987年 | 873篇 |
1986年 | 896篇 |
1985年 | 934篇 |
1984年 | 819篇 |
1983年 | 704篇 |
1982年 | 716篇 |
1981年 | 691篇 |
1980年 | 574篇 |
1979年 | 488篇 |
1978年 | 422篇 |
1977年 | 540篇 |
1976年 | 971篇 |
1975年 | 306篇 |
1974年 | 281篇 |
1973年 | 260篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Y. G. Wang H. Q. Ye K. H. Kuo X. J. Feng S. Z. Long G. L. Lao 《Journal of Materials Science》1991,26(23):6325-6330
The microstructures of unhydrated calcium aluminosulphate Ca4Al6SO16 and Ca3SrAl6SO16 have been studied by high-resolution electron microscopy (HREM). The results showed that twinning and twinned slabs could be introduced taking the [1 1 2] direction as the twin axis so that it seems to be coincident with the law of twinning formed in body-centred cubic structures. A previously reported superlattice with a repeat period twice that of the fundamental structure along the 〈1 1 0〉 direction has also been found in both matrix and twin variants. The close intergrowth of Ca3SrAl6SO16 and another phase, possibly Sr3Al2O6 existing as an inclusion between these two twin variants, was determined and clearly revealed by electron diffraction and HREM images. The coherent interphase boundaries and orientation relationship between them can also be deduced. 相似文献
82.
83.
84.
Jon T. Carter Paul E. Krajewski Ravi Verma 《JOM Journal of the Minerals, Metals and Materials Society》2008,60(11):77-81
The hot blow forming of magnesium sheet offers significant opportunity for forming complex, lightweight parts for automotive
applications. This paper characterizes the elevated-temperature formability of AZ31 magnesium sheet materials and the effect
of processing conditions on the performance of these materials. In addition, magnesium sheet application development at General
Motors Corporation is reviewed. 相似文献
85.
Toshihiko Hoshide Junpei Fujita 《Journal of Materials Engineering and Performance》2008,17(5):627-632
Strength of ground ceramics may be affected by residual stress as well as surface flaws induced by grinding. Strength prediction
for ground ceramics is convenient for mechanical design of ceramic components. In this article, a numerical procedure based
on fracture mechanics was proposed to estimate strength distribution of ground ceramics by considering grinding-induced residual
stress. Bending strength and residual stress of ground ceramics were measured for three grinding-conditions. By comparison
of simulated results with experimental ones, it was revealed that strength characteristics in experiments were well simulated
by using the proposed procedure. 相似文献
86.
The cooling and solidification of melted drops during their movement in an immiscible cooling medium is widely employed for granulation in the chemical industry, and a study of these processes to provides a basis for the design of the granulation tower height and the temperature of the cooling medium is reported. A physical model of the cooling and solidification of the drop is established and the numerical calculation is performed. The influences of the key factors in the solidification, i.e., Bi number, drop diameter, temperature of the cooling medium, etc. are presented. The cooling and solidification during wax granulation in a water‐cooling tower and during urea granulation in an air‐cooling tower (spraying tower) are described in detail. Characteristics of the solidification and temperature distribution within the particle at different times are shown. The model and calculations can be used for structure design of the granulation tower and optimization of the operation parameters. 相似文献
87.
88.
J.A. Bakken L. Barone D. Braun M. Caillat C. Dionisi C. Dor H. Elmamouni F. Ferroni G.L. Grazer J.T. He R. Herbiet B. Ille P. Lecomte E. Longo P.F. Loverre Y.S. Lu J.P. Martin U. Micke R.P. Mount P.A. Pirou H.-G. Sander D. Schmitz M. Schneegans D.P. Stickland R.L. Sumner K.L. Tung E. Valente M. Vivargent 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1985,228(2-3):294-302
A calorimeter of 25 bismuth germanate (BGO) crystals equipped with silicon photodiode readout has been tested at the CERN SPS in the energy range 1–50 GeV. The response for electrons has been shown to be linear in this energy range and the rms resolution obtained (
) is approximately 1%, for E > 4 GeV. The electron/pion separation was found to be better than 1:500 in the energy range 1–20 GeV. Data on lateral and longitudinal shower development were compared with the results of a Monte Carlo simulation using the SLAC-EGS program and found to be in good agreement. 相似文献
89.
Nitrification is a key step for reliable biological nitrogen removal. In order to enhance nitrification in the activated sludge (AS) process, membrane-attached biofilm (MAB) was incorporated in a conventional activated sludge tank. Simultaneous organic carbon removal and nitrification of the MAB incorporated activated sludge (AS + MAB) process was investigated with continuous wastewater treatment. The effluent TOC concentration of AS and the AS + MAB processes were about 6.3 mg/L and 7.9 mg/L, respectively. The TOC removal efficiency of both AS and AS + MAB were above 95% during the wastewater treatment, indicating excellent organic carbon removal performance in both processes. Little nitrification occurred in the AS process. On the contrary, successful nitrification was obtained with the AS + MAB process with nitrification efficiency of about 90%. The volumetric and surface nitrification rates were about 0.14 g/Ld and 6.5 g/m2d, respectively. The results clearly demonstrated that nitrification in the conventional AS process was boosted by MAB. Furthermore, the microfaunal population in the AS + MAB process was different from that in the AS process. The high concentration of rotifers in the AS + MAB process was expected to decrease the generation of excess sludge in the process. 相似文献
90.
A method for the rapid and quantitative determination of aflatoxin B1 from small quantities of liver, around 1-2 g, is described. The extraction procedure involves acidification to pH 2 of the aqueous liver homogenates, extraction with chloroform: acetone and HPLC-fluorimetric detection after derivatization with trifluoroacetic acid. Quantitative recovery of aflatoxin B1 from chick liver was achieved and detection at levels of 0.2-1 ppb was proved feasible. The aflatoxin B1 concentration in chick liver after oral administration is also shown. 相似文献