全文获取类型
收费全文 | 452352篇 |
免费 | 4978篇 |
国内免费 | 1311篇 |
专业分类
电工技术 | 7913篇 |
综合类 | 297篇 |
化学工业 | 70234篇 |
金属工艺 | 19926篇 |
机械仪表 | 14179篇 |
建筑科学 | 10180篇 |
矿业工程 | 3517篇 |
能源动力 | 10577篇 |
轻工业 | 36309篇 |
水利工程 | 5492篇 |
石油天然气 | 12609篇 |
武器工业 | 36篇 |
无线电 | 48920篇 |
一般工业技术 | 92714篇 |
冶金工业 | 79948篇 |
原子能技术 | 12116篇 |
自动化技术 | 33674篇 |
出版年
2021年 | 3796篇 |
2019年 | 3609篇 |
2018年 | 6586篇 |
2017年 | 6583篇 |
2016年 | 7076篇 |
2015年 | 4319篇 |
2014年 | 7277篇 |
2013年 | 19244篇 |
2012年 | 11446篇 |
2011年 | 15100篇 |
2010年 | 12262篇 |
2009年 | 13887篇 |
2008年 | 14234篇 |
2007年 | 14048篇 |
2006年 | 12273篇 |
2005年 | 11334篇 |
2004年 | 10503篇 |
2003年 | 10144篇 |
2002年 | 10069篇 |
2001年 | 10061篇 |
2000年 | 9543篇 |
1999年 | 9667篇 |
1998年 | 23503篇 |
1997年 | 17118篇 |
1996年 | 13218篇 |
1995年 | 10006篇 |
1994年 | 8848篇 |
1993年 | 8971篇 |
1992年 | 6854篇 |
1991年 | 6805篇 |
1990年 | 6514篇 |
1989年 | 6511篇 |
1988年 | 6438篇 |
1987年 | 5514篇 |
1986年 | 5580篇 |
1985年 | 6357篇 |
1984年 | 6026篇 |
1983年 | 5616篇 |
1982年 | 5215篇 |
1981年 | 5299篇 |
1980年 | 5205篇 |
1979年 | 5139篇 |
1978年 | 5251篇 |
1977年 | 5826篇 |
1976年 | 7277篇 |
1975年 | 4770篇 |
1974年 | 4536篇 |
1973年 | 4641篇 |
1972年 | 4056篇 |
1971年 | 3703篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Diphenylzinc, alone or in combination with water and butanone as coinitiators, was used as a polymerization initiator system for a variety of lactones at varying temperatures. The resulting data indicate that the course of the polymerization is greatly influenced by the lactone structure, as well as by the molar ratio of coinitiator to diphenylzinc. When used alone, diphenylzinc exhibited high activity as an initiator in δ‐valerolactone polymerizations, although it was less efficient when used in the β‐butyrolactone and the β‐propiolactone polymerizations. Activity in the polymerization of β‐lactones was increased by adding small amounts of butanone or water. It was also observed that the diphenylzinc–butanone combination was more effective than the diphenylzinc–water mixture in the polymerizations of β‐butyrolactone and β‐propiolactone. Copyright © 2003 Society of Chemical Industry 相似文献
12.
V. N. Tsygankov V. V. Safonov A. I. Kozlov V. P. Gavrilov 《Inorganic Materials》2003,39(10):1076-1078
The GeO2–NiO system is studied in the stability range of Ni2GeO4 by temperature-dependent resistivity measurements, in combination with x-ray diffraction, differential thermal analysis, and thermogravimetry. The resistivity of the starting mixtures and heat-treated samples is measured in the composition range 55–90 mol % NiO. The effect of air humidity on the resistivity of the samples is examined. 相似文献
13.
14.
15.
16.
Kontogiannopoulos N. Psychalinos C. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2006,53(12):1373-1377
In this brief, the well-known switched-current (SI) filtering technique is revisited using the concept of the square-root domain (SRD) filtering. It is proved that SI filters are a subclass of the SRD filters, where sampled-data signal processing is performed. This is achieved by considering typical lossless and lossy SRD sampled-data integrator configurations, using a set of complementary SRD operators which are based on the quadratic I-V relationship of MOS transistor operated in the saturation. Circuit examples are given, where linear-domain integrator and third-order filter configurations were derived using appropriate SRD sampled-data building blocks 相似文献
17.
Nucleation and growth mechanisms and kinetics of crystals of an amino acid salt were investigated in a methanol‐water system by measuring and evaluating the induction time as a function of the supersaturation ratio and temperature in batch salting out crystallization experiments. Discrimination between the possible crystallization mechanisms, and estimation of the kinetic parameters were carried out using nonlinear parameter identification. The results concerning the growth mechanism obtained were checked additionally by measuring the induction time as a function of number density of seed crystals. 相似文献
18.
G. I. Glazov A. M. Garaiev R. V. Timerkhanov 《Chemistry and Technology of Fuels and Oils》2003,39(1-2):26-53
A series of small–capacity units has recently been constructed in regions of oil field development and crude oil and gas condensate production to satisfy the requirements for such petroleum products as naphtha, diesel fuel, kerosene, and boiler fuel and to reduce costs for delivery of these products. There are almost no data in the technical literature, particularly in periodicals, on the construction and operation of small–capacity units. We attempt to generalize the experience of Orgeneftekhimzavody Trust in this area. We hope that this experience will be useful to specialists in the development and management of small–capacity plants. 相似文献
19.
G. Pfaff 《Inorganic Materials》2003,39(2):123-126
A new class of special effect pigments based on synthetically manufactured silica flakes coated with metal oxides was developed and introduced into the market. Silica flake pigments show extraordinary color effects such as improved interference and strong angle-dependent behavior. They can be used in automotive paints, industrial paints, plastics, and printing inks. 相似文献
20.