全文获取类型
收费全文 | 38006篇 |
免费 | 2121篇 |
国内免费 | 58篇 |
专业分类
电工技术 | 247篇 |
综合类 | 126篇 |
化学工业 | 9103篇 |
金属工艺 | 691篇 |
机械仪表 | 762篇 |
建筑科学 | 1182篇 |
矿业工程 | 90篇 |
能源动力 | 1032篇 |
轻工业 | 7532篇 |
水利工程 | 378篇 |
石油天然气 | 236篇 |
武器工业 | 2篇 |
无线电 | 1642篇 |
一般工业技术 | 5699篇 |
冶金工业 | 5991篇 |
原子能技术 | 181篇 |
自动化技术 | 5291篇 |
出版年
2024年 | 77篇 |
2023年 | 375篇 |
2022年 | 907篇 |
2021年 | 1360篇 |
2020年 | 938篇 |
2019年 | 1027篇 |
2018年 | 1496篇 |
2017年 | 1493篇 |
2016年 | 1585篇 |
2015年 | 1156篇 |
2014年 | 1584篇 |
2013年 | 3040篇 |
2012年 | 2526篇 |
2011年 | 2492篇 |
2010年 | 1957篇 |
2009年 | 1790篇 |
2008年 | 1682篇 |
2007年 | 1470篇 |
2006年 | 1092篇 |
2005年 | 910篇 |
2004年 | 808篇 |
2003年 | 812篇 |
2002年 | 639篇 |
2001年 | 507篇 |
2000年 | 421篇 |
1999年 | 472篇 |
1998年 | 2154篇 |
1997年 | 1394篇 |
1996年 | 900篇 |
1995年 | 507篇 |
1994年 | 405篇 |
1993年 | 389篇 |
1992年 | 149篇 |
1991年 | 109篇 |
1990年 | 90篇 |
1989年 | 100篇 |
1988年 | 114篇 |
1987年 | 109篇 |
1986年 | 80篇 |
1985年 | 95篇 |
1984年 | 82篇 |
1983年 | 53篇 |
1982年 | 52篇 |
1981年 | 73篇 |
1980年 | 78篇 |
1978年 | 43篇 |
1977年 | 117篇 |
1976年 | 226篇 |
1975年 | 38篇 |
1973年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
M Fernández J Cao MD Vázquez-Illanes JI Ramos-Martínez JA Villamarín 《Canadian Metallurgical Quarterly》1994,33(2):355-363
Phosphofructokinase purified from mantle tissue of the sea mussel Mytilus galloprovincialis, was phosphorylated "in vitro" by the catalytic subunit of cyclic AMP-dependent protein kinase. The incorporation of phosphate gave rise to an activation of the enzyme by increasing its affinity for fructose-6-phosphate, by decreasing its sensitivity to the inhibition by ATP and by enhancing the effect of allosteric activators (5'-AMP and fructose-2,6-bisphosphate). In addition, the effects of phosphorylation on the catalytic activity are pH-dependent. 相似文献
92.
A novel complex formed by ruthenium (III) and the sequestering ligand 1,2-propylenediaminetetraacetic acid (PDTA) has been synthetized and characterized. The structure of the monomeric compound, studied by X-ray diffraction , shows an almost symmetric octahedral geometry around the metal ion, with two chlorine atoms in a cis conformation. The antitumour activity against a variety of murine and human cancers is reported. 相似文献
93.
G. Trigueros M. L. García C. Casas J. A. Ordóñez M. D. Selgas 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1995,201(3):298-302
Proteolytic and lipolytic activities of ninePenicillium strain and oneMucor strain previously isolated from Spanish dry fermented sausages have been studied.P. camemberti STCC 2267 andAspergillus oryzae ATCC 9362 were also used. Myofibrillar and sarcoplasmic proteins as well as fat extracted from pork meat and -naphthyl acetate, -naphthyl caprilate and -naphthyl laurate were used as substrates. Mould strains were grown in an enrichment medium prepared at pH 5.5 and 7.0 and malt extract broth. Strains were incubated at 18°C and 22°C. Myofibrillar proteins and -naphthyl caprilate were the most hydrolysed substrates. The greater enzymatic activities were observed at a pH 7.0 and 22°C. However, five mould strains showed considerable enzymatic activities under conditions similar to those used for ripening dry fermented sausages. These strains can be assayed as potential starter cultures for industrial sausage production. 相似文献
94.
Bravo-Montes J. A. Martín-Toledano A. Sánchez-Macián A. Ruano O. Garcia-Herrero F. 《The Journal of supercomputing》2022,78(6):8056-8080
The Journal of Supercomputing - CMOS technology is facing physical limitations in scaling the manufacturing process. Therefore, to deepen the development of better designs in a smaller area, it is... 相似文献
95.
96.
A method for the calculation of the fractional Fourier transform (FRT) by means of the fast Fourier transform (FFT) algorithm is presented. The process involves mainly two FFT's in cascade; thus the process has the same complexity as this algorithm. The method is valid for fractional orders varying from -1 to 1. Scaling factors for the FRT and Fresnel diffraction when calculated through the FFT are discussed. 相似文献
97.
98.
S. Rodríguez C. Lafuente J. A. Carrión F. M. Royo J. S. Urieta 《International Journal of Thermophysics》1996,17(6):1281-1288
Excess Volumes,V
E, and excess viscosities,
E, at 293.15 and 313.15 K are reported for binary mixtures of some cyclic ethers (tetrahydrofuran, tetrahydropyran, 2-methyltetrahydrofuran and 2,5-dimethyltetrahydrofuran) + bromocyclohexane. These properties were obtained from density and viscosity measurements.
E and
E show negatives values for all the mixtures. 相似文献
99.
JA Ortu?o-Cortés L Quintana-Tomás A García-García 《Canadian Metallurgical Quarterly》1996,19(2):47-51
1.5% Capsaicin (Cap) or Vehicle was respectively used to treat the right or left sciatic nerve in 20 Sprague-Dawley rats. On the seventh day, the 20 rats were at random divided into electroacupuncture (EA) group and non-EA group, the spinal cord corresponding to the afferent segments of sciatic nerve was taken out for observing the changes of acetylcholinesterase (AChE) activity and [3H]-quinuelidinylbenzylate (QNB) binding sites in the spinal dorsal horn (SDH). The results were as follows: (1) EA "Huantiao" could enhance AChE activity in the SDH and decrease [3H]-QNB binding sites; (2) Cap treating sciatice nerve could weaken AChE activity in the SDH and merease [3H]-QNB binding sites; (3) Cap treatment could inhibit or partially inhibit the actions of EA as above. The results indicated that ACh participated in the primary afferent of acupuncture information and might exist in Cap-sensitive neurons. 相似文献
100.
E Poves Martínez 《Canadian Metallurgical Quarterly》1996,88(10):677-686
In the last years different classification systems for hospitalized patients have been developed in the United States, that allow to evaluate different aspects of any Hospital: The quality, the efficacy and the efficiency. The classification of "The Diagnosis Related Groups" (DRG) relates the hospitalized patients with the expenses that they generate, and it is the most used in Europe. In the version DRG-All Patient, all the diagnoses and procedures of the hospitalized patients, using the International Classification of Diseases, are divided in to 25 Major Diagnostic Categories (MDC) where each one excludes all the others. We describe the behavior with respect to the age, sex and stay of all the GDR integrated in the CDM 6 and 7: diseases and disorders of the digestive tract, and diseases and disorders of the hepatobiliary system and the pancreas. The study has been carried out with a national data base of two millions of cases seen from 214 acute-care Hospitals. The MDC number 6 is the most frequent, with an important number of patients in the pediatric age; it is more frequent in males; the average stay is 8.59 days and 19 GDR (36.5%) have a variation coefficient greater than one. The other MDC, number 7 is less frequent, the majority of the patients are between 60-80 years of age, the average stay is 12.2 days with a coefficient of variation greater than one in 4 GDR (17.4%). Clinical Services should know the characteristics and behavior of their patients, as well as the comparison with the national data bases. This may allow a control of the quality and the costs by using a common "language" with the managers. 相似文献