全文获取类型
收费全文 | 1706篇 |
免费 | 31篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 21篇 |
综合类 | 14篇 |
化学工业 | 207篇 |
金属工艺 | 75篇 |
机械仪表 | 21篇 |
建筑科学 | 71篇 |
能源动力 | 44篇 |
轻工业 | 145篇 |
水利工程 | 10篇 |
石油天然气 | 4篇 |
武器工业 | 1篇 |
无线电 | 155篇 |
一般工业技术 | 239篇 |
冶金工业 | 549篇 |
原子能技术 | 5篇 |
自动化技术 | 181篇 |
出版年
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 18篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 16篇 |
2017年 | 22篇 |
2016年 | 20篇 |
2015年 | 34篇 |
2014年 | 34篇 |
2013年 | 75篇 |
2012年 | 50篇 |
2011年 | 70篇 |
2010年 | 54篇 |
2009年 | 64篇 |
2008年 | 59篇 |
2007年 | 61篇 |
2006年 | 46篇 |
2005年 | 48篇 |
2004年 | 50篇 |
2003年 | 44篇 |
2002年 | 48篇 |
2001年 | 32篇 |
2000年 | 30篇 |
1999年 | 55篇 |
1998年 | 169篇 |
1997年 | 99篇 |
1996年 | 89篇 |
1995年 | 62篇 |
1994年 | 73篇 |
1993年 | 47篇 |
1992年 | 16篇 |
1991年 | 15篇 |
1990年 | 26篇 |
1989年 | 19篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 12篇 |
1976年 | 30篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1971年 | 3篇 |
排序方式: 共有1742条查询结果,搜索用时 0 毫秒
1.
2.
射频电路设计人员常用的一条经验法则是:有源器件的fT至少应为工作频率的十倍时,现代无线设备中的射频电路才会具有良好的性能. 相似文献
3.
Henrik Pettersson Tadeusz Gruszecki Lars-Henrik Johansson Per Johander 《Solar Energy Materials & Solar Cells》2003,77(4):6595
A manufacturing technique for monolithic dye-sensitised solar cells is presented. Encapsulated modules designed for indoor low-power applications have been prepared using industrial methods and equipment. Under certain conditions (light intensity <5000 lx, temperature between –10°C and 50°C, and relative humidity of appr. 50%), the modules have performed well and shown excellent long-term stability. Moreover, modules withstand illumination in combination with storage at 100% relative humidity. However, a certain degradation of the module performance takes place at illuminations exceeding 5000 lx and temperatures exceeding 50°C. 相似文献
4.
5.
Visual and auditory stimulus discrimination tasks, analogous to those used in the Reitan-Klove Sensory Perceptual Examination, were performed by 12 cocaine-dependent and 5 alcohol-dependent patients after 1 week, 3 weeks, and 3 months of verified abstinence. Sixteen control subjects, who were not substance-dependent, performed the same tasks after comparable intervals. During each task, either visual or auditory stimuli were presented in the left, in the right, or in both sensory fields. A simple key press was made to discriminate these conditions. Cocaine-dependent patients responded more slowly than control subjects during both tasks. The reaction-time slowing persisted across all three sessions, spanning a 3-month period of abstinence. There were no significant differences between the cocaine-dependent and control groups in response accuracy. In the context of other findings, these findings are interpreted as reflecting an enduring effect of prior cocaine dependence on motor as opposed to sensory functioning. 相似文献
6.
A sampled grating distributed Bragg reflector-laser integrated with a waveguide Franz-Keldysh modulator is investigated for high optical power applications. The EAM modulation efficiency is demonstrated to asymptotically approach a limit determined by the internal differential photodetector efficiency. Linear photocurrent and 1 dB small signal AC compression point both exceed 70 mA, indicating high saturation power. 相似文献
7.
Claes-Gran Johansson 《Journal of the Institute of Brewing》1996,102(4):249-250
A combustion method, relying on the Dumas principle, for the determination of total nitrogen in barley and malt, has been collaboratively tested by the Analysis Committee of the European Brewery Convention. Repeatability, r95, and reproducibility, R95, values were 0.063 and 0.116% of dry matter, respectively, for samples with nitrogen contents in the range 1.23 to 1.86% N of dry matter. There was no significant difference between these values for barley and malt. The Analysis Committee approved the adoption of the combustion method for inclusion in Analytica EBC as an alternative method. 相似文献
8.
The purpose of all injury care is to restore patients' pre-injury functioning and to facilitate the return to normal activities. The aim of this prospective study was to describe and analyse psychiatric factors and other patient-related characteristics which influence long-term results after moderate injuries. One hundred and sixty-nine injured patients were randomized to go through a comprehensive psychosocial research protocol and to participate in the 12 month follow up. The 49 patients lost to follow-up differed significantly from all other patients. They were more often single, blue-collar workers with a lower educational level and had a less favourable psychosocial background, including alcohol abuse. The 120 patients who completed the follow-up were divided in two groups: the non-recovered group (NR, N = 58), patients reporting limitations in performing their work and/or limitations in carrying out housework and/or in social life, and the recovered group (R, N = 62), patients reporting full recovery or only minor limitations in exercise or sports 12 months after the injury. The NR patients were older (P < 0.05), had a slightly higher injury Severity Score (P < 0.01) and showed signs of depression both during the acute post-injury period and at 1 year follow up (P < 0.001). The multivariate analysis showed that measurements of pain and depression during the acute post-injury period were associated with the functional outcome after 12 months. Co-operation between injury and psychiatric units should be developed to identify patients needing psychosocial or psychiatric support during the early phase of rehabilitation. 相似文献
9.
Wheat proteins, soluble in diluted acid (glutenins), have been fractionated by counter-current distribution (CCD) using an aqueous two-phase system. The phase system is based on poly(ethylene glycol) and dextran but contains also 1% propionic acid and 6 mM magnesium sulfate. Approximately half of the bulk proteins partitioned to the upper phase while starch and other particles were recovered only into the lower phase. Whole wheat flour could be applied as sample for the CCD and 57 transfers were carried out. Starch and insoluble proteins remained stationary, while proteins followed the mobile phase to various degrees giving rise to a distribution pattern. The CCD pattern of the proteins showed distinct differences when various kinds of wheat flour were analysed. The patterns indicate that at least six subpopulations of proteins can be obtained by using two-phase extraction. 相似文献
10.
IuA Magakian EM Karalova LO Abroian SA Karapetian 《Canadian Metallurgical Quarterly》1997,39(8):705-710
Cytophotometry of rat blood erythroid cells during anaemia, induced by phenylhydrazin (4-8 days from the beginning of injections), revealed that all forms of bone marrow containing haemoglobin were thrown into the blood. On its peak (4th day), the greatest contribution in blood haemoglobinization (50%) is made by microcytes. From the 5th day and up to the end of the restoration period the important role in this process is played by macrocytes. From the 6th day the role of normocytes increases, whose contribution by 8th day reaches 70% of the whole haemoglobin amount in blood. In contrary to anaemizated birds, whose erythroid cells ripen in blood, in rats all the transformations of erythron during anaemia are accomplished in bone marrow. 相似文献