全文获取类型
收费全文 | 734357篇 |
免费 | 10085篇 |
国内免费 | 2361篇 |
专业分类
电工技术 | 13602篇 |
综合类 | 623篇 |
化学工业 | 110781篇 |
金属工艺 | 27390篇 |
机械仪表 | 22709篇 |
建筑科学 | 18003篇 |
矿业工程 | 2892篇 |
能源动力 | 20227篇 |
轻工业 | 63376篇 |
水利工程 | 6776篇 |
石油天然气 | 9391篇 |
武器工业 | 31篇 |
无线电 | 91255篇 |
一般工业技术 | 142299篇 |
冶金工业 | 138370篇 |
原子能技术 | 13472篇 |
自动化技术 | 65606篇 |
出版年
2021年 | 5975篇 |
2020年 | 4413篇 |
2019年 | 5688篇 |
2018年 | 9365篇 |
2017年 | 9441篇 |
2016年 | 10162篇 |
2015年 | 7053篇 |
2014年 | 11490篇 |
2013年 | 35533篇 |
2012年 | 19151篇 |
2011年 | 26608篇 |
2010年 | 20792篇 |
2009年 | 23668篇 |
2008年 | 24640篇 |
2007年 | 24650篇 |
2006年 | 22152篇 |
2005年 | 20087篇 |
2004年 | 19389篇 |
2003年 | 19038篇 |
2002年 | 18284篇 |
2001年 | 18157篇 |
2000年 | 17002篇 |
1999年 | 17941篇 |
1998年 | 43280篇 |
1997年 | 30878篇 |
1996年 | 24003篇 |
1995年 | 18328篇 |
1994年 | 16328篇 |
1993年 | 16034篇 |
1992年 | 11788篇 |
1991年 | 11177篇 |
1990年 | 10868篇 |
1989年 | 10326篇 |
1988年 | 9934篇 |
1987年 | 8554篇 |
1986年 | 8429篇 |
1985年 | 9903篇 |
1984年 | 9218篇 |
1983年 | 8141篇 |
1982年 | 7546篇 |
1981年 | 7588篇 |
1980年 | 7092篇 |
1979年 | 6887篇 |
1978年 | 6625篇 |
1977年 | 7805篇 |
1976年 | 10363篇 |
1975年 | 5617篇 |
1974年 | 5342篇 |
1973年 | 5300篇 |
1972年 | 4365篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
A mass spectrometric technique combined with a double Knudsen cell was used to determine the antimony and copper activities
in the Cu-Sb binary system at 1373 K and in the two-melt composition range of the Cu−S−Sb ternary system at 1423 K. The antimony
and copper activities were calculated based on the intensity ration of the gaseous Sb and Cu species, over the unknown and
known activity samples, respectively. γ
Sb
o
were found to be 1.1×10−2 in molten copper at 1373 K, and 1.8×10−2 and 0.44 in a copper-rich phase and in a matter phase, of the Cu−S−Sb ternary system at 1423 K, respectively. These values
indicate, that antimony can be removed during the matte smelting and slagging stage of the copper smelting process. Interaction
parameters of antimony in molten copper slagging stage of the copper smelting process. Interaction parameters of antimony
in molten copper at 1423 K were calculated and found to be 10.7, −5.4, and 6.3 for ε
Sb
Sb
· ρSb
Sb, and ε
Sb
S
, respectively.
M. HINO, formerly Visiting Scientist at the University of Toronto 相似文献
962.
A new time domain reflectometry algorithm is presented. It is intended for identification of the impedance profile of the non-uniform lossless transmission line. Experimental results are presented to illustrate the validity of this new technique. 相似文献
963.
Self-Adapting Linear Algebra Algorithms and Software 总被引:2,自引:0,他引:2
Demmel J. Dongarra J. Eijkhout V. Fuentes E. Petitet A. Vuduc R. Whaley R.C. Yelick K. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2005,93(2):293-312
One of the main obstacles to the efficient solution of scientific problems is the problem of tuning software, both to the available architecture and to the user problem at hand. We describe approaches for obtaining tuned high-performance kernels and for automatically choosing suitable algorithms. Specifically, we describe the generation of dense and sparse Basic Linear Algebra Subprograms (BLAS) kernels, and the selection of linear solver algorithms. However, the ideas presented here extend beyond these areas, which can be considered proof of concept. 相似文献
964.
The article established the regularities of change of the physicomechanical characteristics and strength of glass textolites in single and repeated thermal loading. It shows that under multiple loading the intense loss of strength of the investigated materials is due to increased porosity on account of the large number of microcracks appearing in the structure. A correlation is obtained between the elastic and strength characteristics and porosity in dependence on the temperature of multiple heating which in the first approximation is described by a polynomial of second degree with respect to temperature, multiplied by the reciprocal of porosity.Translated from Problemy Prochnosti, No. 6, pp. 53–58, June, 1991. 相似文献
965.
P.O. Fanger B.M. Ipsen G. Langkilde B.W. Olessen N.K. Christensen S. Tanabe 《Energy and Buildings》1985,8(3):225-236
Groups of 32 and 16 subjects of both sexes were exposed in an environmental chamber to radiant asymmetry caused by a cool wall, a warm wall, and a cool ceiling. Each subject was tested individually while seated and clothed at 0.6 clo. During each 3.5-hour experiment the subject was exposed to six radiant temperature asymmetries. He was asked whether and where he experienced any local cool or warm sensation, and whether it was felt to be uncomfortable. During the entire experiment he was kept thermally neutral by changing the air temperature according to his wishes.For cool walls, warm walls, and cool ceilings curves have been established showing the percentage of dissatisfied subjects as a function of the radiant asymmetry. Radiant asymmetry at a warm wall caused less discomfort than a cool wall. A cool ceiling caused less discomfort than a warm ceiling. Accepting that 5% of the subjects may feel uncomfortable. a radiant temperature asymmetry of 10°C is allowable at a cool wall, 23°C at a warm wall, and 14°C under a cool ceiling. A previous study showed that 4°C is allowable under a warm ceiling. Radiant asymmetry had no significant impact on the operative temperatures preferred by the subjects. No significant differences were observed between the responses of men and women exposed to radiant asymmetry. 相似文献
966.
Ruthenium colloidal particles prepared by the decomposition of a ruthenium acid sulfite complex increased the electrochemical reduction of benzene from 45% to 60% at room temperature and 10 psig of hydrogen. The reduction was carried out in a 21 mole % ethanol - 79 mole % hexamethylphosporamide. The significant increase in the percent of benzene reduced was accompanied by an apparent current efficiency of 98%. Comparison with analogous experiments employing colloidal platinum particles indicates that the above increase in benzene reduction can be attributed to direct catalytic hydrogenation by the ruthenium. 相似文献
967.
Cationic thermal motions in the MPS3 have been related to substitution abilities in this layer family. They have also been correlated to the crystal field stabilization energy. These considerations explain why some MPS3 materials may or may not undergo a low temperature substitution intercalation reaction. From interatomic distances comparisons, the bond between (PS3) groups in the anionic (P2S6)4? octahedra, is found to be easily stretched upon cation substitution. Cationic radii follows the expected variation according to their high spin configuration in octahedral sulfur environment. 相似文献
968.
Tested the ability of 4 adult male Sprague-Dawley rats to use odors in discrimination among littermates living as a group. Ss were trained in a Y-maze to discriminate the presence of a littermate from its absence. Results from transfer of training in 3 subsequent testing periods indicated that the animals were capable of distinguishing among individuals when relatedness and familiarity were held constant, that this ability was not due to training, and that performance was based solely on odor cues. Results suggest that laboratory rats exhibit odor sensitivities conmensurate with very complex social processes. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
969.
In a direct-conversion transmitter system, the nonideal transfer characteristics of practical analog subsystems can have significant adverse effects on the performance of the transmitter system. While a significant body of research exists on correcting static errors (including gain imbalance, phase errors, and DC offsets) in the analog subsystems, relatively little attention has been paid to the impact of nonideal frequency-dependent characteristics in the analog reconstruction filters that are employed in direct-conversion structures. This paper presents a new computationally efficient and numerically robust method for automatic digital compensation for nonideal frequency-dependent characteristics in the signal reconstruction filters of a quadrature (IQ) modulator structure. The new compensation technique is used in conjunction with existing compensation approaches that compensate for static errors. 相似文献
970.
In the problem of estimating the angles of arrival to a uniform linear array, we present an efficient method to compute Maximum Likelihood (ML) estimations, based on the Modified Variable Projection (MVP) algorithm. In contrast to methods like Iterative Quadratical Maximum Likelihood (IQML) or the Iterative Method of Direction Estimation (IMODE), it is not based on a polynomial parameterization but on directly exploiting the Vandermonde structure through analytical tools like the Fast Fourier Transform (FFT), the geometric series summation formula, and Horner's synthetic division. The computational burden of the proposed method is significantly smaller than the burden of IMODE and of the Relaxation (RELAX) algorithm. Besides, it is shown that the computation of the ML estimation can be divided in a preliminary step in which a few FFTs are computed and an iterative step with a complexity that is independent of the array size. 相似文献