全文获取类型
收费全文 | 61225篇 |
免费 | 3266篇 |
国内免费 | 537篇 |
专业分类
电工技术 | 1062篇 |
综合类 | 626篇 |
化学工业 | 11111篇 |
金属工艺 | 1452篇 |
机械仪表 | 1542篇 |
建筑科学 | 2325篇 |
矿业工程 | 288篇 |
能源动力 | 1446篇 |
轻工业 | 7912篇 |
水利工程 | 649篇 |
石油天然气 | 621篇 |
武器工业 | 90篇 |
无线电 | 4474篇 |
一般工业技术 | 9832篇 |
冶金工业 | 12532篇 |
原子能技术 | 434篇 |
自动化技术 | 8632篇 |
出版年
2024年 | 146篇 |
2023年 | 633篇 |
2022年 | 957篇 |
2021年 | 1768篇 |
2020年 | 1380篇 |
2019年 | 1243篇 |
2018年 | 2156篇 |
2017年 | 2149篇 |
2016年 | 2203篇 |
2015年 | 1782篇 |
2014年 | 2305篇 |
2013年 | 3941篇 |
2012年 | 3597篇 |
2011年 | 3604篇 |
2010年 | 2775篇 |
2009年 | 2541篇 |
2008年 | 2768篇 |
2007年 | 2409篇 |
2006年 | 1910篇 |
2005年 | 1581篇 |
2004年 | 1398篇 |
2003年 | 1280篇 |
2002年 | 1203篇 |
2001年 | 825篇 |
2000年 | 765篇 |
1999年 | 921篇 |
1998年 | 4029篇 |
1997年 | 2502篇 |
1996年 | 1667篇 |
1995年 | 986篇 |
1994年 | 857篇 |
1993年 | 849篇 |
1992年 | 328篇 |
1991年 | 333篇 |
1990年 | 309篇 |
1989年 | 318篇 |
1988年 | 263篇 |
1987年 | 234篇 |
1986年 | 248篇 |
1985年 | 284篇 |
1984年 | 245篇 |
1983年 | 192篇 |
1982年 | 216篇 |
1981年 | 231篇 |
1980年 | 208篇 |
1979年 | 168篇 |
1978年 | 150篇 |
1977年 | 259篇 |
1976年 | 522篇 |
1975年 | 119篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Software Quality Journal - Energy consumption of software has been becoming increasingly significant, since it can vary according to how the software has been developed. In recent years, developers... 相似文献
102.
C García Barroso R Cela Torrijos J A Pérez-Bustamante 《Zeitschrift für Lebensmittel-Untersuchung und -Forschung》1987,185(4):307-314
The different groups and/or classes among phenolic acids and aldehydes identified during the elaboration process of "fino" sherry wine have been studied. The study was carried out using different processes during the elaboration of the wine and we have attempted to establish whether the different treatments of the grape affect these groupings. The study was undertaken by means of cluster and multifactorial analysis on the data obtained by the quantitative determination of phenolic acids and aldehydes during vinification and in experiments carried out on the grape under different mechanical treatments. The analysis of phenolic acids and aldehydes was done with HPLC, using a C-18 mu-Bondapak and a stepwise composite gradient. The samples were previously extracted with ethylic ether. 相似文献
103.
The influence of nonsolvent, crystallinity of the polymer film, and addition of dodecane (a poor solvent for the polymer and for the nonsolvent) on the morphology of polylactides films has been investigated and was related to phase separation behavior. Both amorphous poly‐DL ‐lactide (PDLLA) and crystalline poly‐L ‐lactide (PLLA) were dissolved in dichloromethane, and subsequently films were made by immersion in nonsolvent baths. PDLLA gave dense films without any internal structure, since the structure was not solidified by crystallization or glassification. PLLA films show varying structure depending on the nonsolvent. With methanol, asymmetric morphologies were observed as a result from combined liquid‐liquid demixing and crystallization, while with water symmetric spherulitic structures were formed. As a next step, dodecane was added, which is not miscible with the nonsolvent, and we found it to have a strong influence on the morphology of the films. The PDLLA films with dodecane did not collapse: a closed cell structure was obtained. In PLLA films, dodecane speeds up phase separation and induces faster crystallization in the films, and the porosity, size of the pores, and interconnectivity increased. When the PLLA solutions were subjected to a heat pretreatment, crystallization could be postponed, which yielded a cellular structure around dodecane, which did not contain spherulites anymore. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 959–971, 2007 相似文献
104.
Tin electrodeposition in its initial stages in acid sulfate/gluconate baths was studied with varying tin and gluconate concentrations using potential-controlled electrochemical techniques. The deposit morphology was observed by scanning electron microscopy (SEM). A comparison with tin electrodeposition from acid sulfate baths in the absence of gluconate was also carried out. Use of a highly acidic bath leads to nonuniform deposits, even in the presence of gluconate; at pH 4 deposits are uniform, brilliant and suitable for finishing applications. Tin crystallites have a well defined morphology which depends on bath agitation conditions. In the absence of agitation, the crystallites have the same tetragonal shape as in a sulfate bath without gluconate. 相似文献
105.
V. M. Lupéiko P. V. Umrikhin P. N. Dé'yachkov V. A. Perepelitsyn 《Refractories and Industrial Ceramics》1967,8(1-2):125-128
Conclusions A laboratory installation for flame guncreting was designed, built, and tested. A method was developed for flame guncreting of basic refractories. The guncreted layer obtained as a result of flame guncreting is formally bonded with the refractory, and in its density and structure, is significantly better than it.Translated from Ogneupory, No.2, pp.54–57, February, 1967. 相似文献
106.
107.
The catalytic activities of WCI6Ph4Sn, MoCl5Ph4Sn and tetrabenzyltitanium were examined in the polymerization of acetylene. The structure, morphology and electrical conductivity of the doped and non doped polyacetylene were also studied. 相似文献
108.
Summary Three copolymers of ethylene and 1-decene, covering a wide range of compositions, have been synthesized with a MgCl2-supported Ziegler-Natta catalyst. The analysis by DSC and X-ray shows a great degree of heterogeneity in these copolymers and appreciable levels of crystallinity, corresponding to the orthorhombic lattice of polyethylene, are present even for very high 1-decene contents. 相似文献
109.
110.
M. Pérez-Luna A. Cosultchi J. A. Toledo-Antonio C. Angeles-Chavez E. M. Arce-Estrada 《Catalysis Letters》2006,107(1-2):103-110
Three Ni/ZrO2–SO4=/Al2O3 catalysts with different concentrations of platinum (0.2, 0.3 and 0.4 wt%) were prepare and tested for n-butane isomerization reaction at 338 K, in absence and in presence of hydrogen. The results shown that, at low temperature,
platinum contributes to the olefin or butyl ion formation and the reaction follows a bimolecular pathway. However, when the
reaction occurs in the presence of hydrogen, the formation of butyl ions is inhibited. The main feature of platinum addition
is the stabilization of the catalytic activity, which is indicated by the slow deactivation constants compared to that of
the unpromoted catalyst. 相似文献