全文获取类型
收费全文 | 4263篇 |
免费 | 286篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 48篇 |
综合类 | 5篇 |
化学工业 | 955篇 |
金属工艺 | 88篇 |
机械仪表 | 62篇 |
建筑科学 | 186篇 |
矿业工程 | 5篇 |
能源动力 | 156篇 |
轻工业 | 317篇 |
水利工程 | 41篇 |
石油天然气 | 15篇 |
无线电 | 334篇 |
一般工业技术 | 857篇 |
冶金工业 | 735篇 |
原子能技术 | 29篇 |
自动化技术 | 722篇 |
出版年
2023年 | 62篇 |
2022年 | 105篇 |
2021年 | 177篇 |
2020年 | 122篇 |
2019年 | 122篇 |
2018年 | 150篇 |
2017年 | 133篇 |
2016年 | 149篇 |
2015年 | 122篇 |
2014年 | 196篇 |
2013年 | 287篇 |
2012年 | 245篇 |
2011年 | 315篇 |
2010年 | 214篇 |
2009年 | 199篇 |
2008年 | 204篇 |
2007年 | 188篇 |
2006年 | 161篇 |
2005年 | 111篇 |
2004年 | 112篇 |
2003年 | 75篇 |
2002年 | 91篇 |
2001年 | 36篇 |
2000年 | 36篇 |
1999年 | 48篇 |
1998年 | 97篇 |
1997年 | 70篇 |
1996年 | 50篇 |
1995年 | 46篇 |
1994年 | 36篇 |
1993年 | 36篇 |
1992年 | 23篇 |
1991年 | 15篇 |
1990年 | 22篇 |
1989年 | 23篇 |
1988年 | 16篇 |
1986年 | 15篇 |
1985年 | 25篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 23篇 |
1981年 | 30篇 |
1980年 | 17篇 |
1979年 | 26篇 |
1978年 | 26篇 |
1977年 | 21篇 |
1976年 | 27篇 |
1975年 | 22篇 |
1974年 | 18篇 |
1898年 | 14篇 |
排序方式: 共有4555条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Cloning of observables, unlike standard cloning of states, aims at copying the information encoded in the statistics of a
class of observables rather then on quantum states themselves. In such a process the emphasis is on the quantum operation
(evolution plus measurement) necessary to retrieve the original information. We analyze, for qubit systems, the cloning of
a class generated by two noncommuting observables, elucidating the relationship between such a process and joint measurements.
This helps in establishing an optimality criterion for cloning of observables. We see that, even if the cloning machine is
designed to act on the whole class generated by two noncommuting observables, the same optimal performances of a joint measurement
can be attained. Finally, the connection with state dependent cloning is enlightened. 相似文献
5.
Two proprietary biocides were compounded and extruded at three concentrations, respectively, into high density polyethylene-maple wood flour lumber (HDPE-MWL) and evaluated for their efficacy to control fungal colonization and discoloration using the ASTM Standard G 21-96. Although the silver biocide used in this study did not control fungal colonization and discoloration of HDPE-MWL, statistically significant difference was observed between the highest silver biocide concentration and those of the two lower silver biocide concentrations. The latter exhibited no significant difference with the controls. In contrast, the three levels of zinc biocides showed significant difference from each other with respect to their efficacy against fungal colonization and discoloration of HDPE-MWL. Overall, only the zinc biocide was efficacious against fungal colonization and discoloration. The biocide containing zinc as an active biocidal agent was most efficacious at 1% (by weight) concentration. 相似文献
6.
Leslie E. Chipman Benjamin B. Bederson Jennifer A. Golbeck 《Behaviour & Information Technology》2004,23(1):1-9
The SlideBar is a physical linear input device for absolute position control of 1° of freedom, consisting of a physical slider with a graspable knob positioned near or attached to the keyboard. Its range of motion is directly mapped to a one dimensional input widget such as a scrollbar. The SlideBar provides absolute position control in one dimension, is usable in the non-dominant hand in conjunction with a pointing device, and offers constrained passive haptic feedback. These characteristics make the device appropriate for the common class of tasks characterized by one-dimensional input and constrained range of operation. An empirical study of three devices (SlideBar, mouse controlled scrollbar, and mousewheel) shows that for common scrolling tasks, the SlideBar has a significant advantage over a standard mouse controlled scrollbar in user preference. In addition, users tended to prefer it over the mousewheel (without statistical significance). 相似文献
7.
This study tried to investigate, by the power comsumption technique, the influence of the powder's and solvent's properties on wet granulation.
It could be shown that the required amount of granulation liquid decreases when the particle size of the powder to be granulated increases. This relationship is however only true when the particle size distribution of the powder to be granulated is rather narrow.
Powders having the same solubility in different solvents require the same optimal liquid quantity for granulation, but the properties of resulting granules depend on surface tension and wetting properties of the solvent.
When the powder to be granulated contains crystallisation water, the temperature rising in the mixer can be sufficient to liberate this water, which must be taken into account in the optimal granulation liquid requirement.
The effect of a macromolecular binder (PVP, HPMC) has also been studied: the optimal liquid quantity required changes with the kind of binder used and the manufacturing process (binder used in solution or added as dry powder).
It was also shown that in the case of lactose, the optimal quantity of PVP or HPMC can be determined from the power consumption records and from the granules friability studies 相似文献
It could be shown that the required amount of granulation liquid decreases when the particle size of the powder to be granulated increases. This relationship is however only true when the particle size distribution of the powder to be granulated is rather narrow.
Powders having the same solubility in different solvents require the same optimal liquid quantity for granulation, but the properties of resulting granules depend on surface tension and wetting properties of the solvent.
When the powder to be granulated contains crystallisation water, the temperature rising in the mixer can be sufficient to liberate this water, which must be taken into account in the optimal granulation liquid requirement.
The effect of a macromolecular binder (PVP, HPMC) has also been studied: the optimal liquid quantity required changes with the kind of binder used and the manufacturing process (binder used in solution or added as dry powder).
It was also shown that in the case of lactose, the optimal quantity of PVP or HPMC can be determined from the power consumption records and from the granules friability studies 相似文献
8.
Xiao-Ying Wang Jonathan M. Garibaldi Benjamin Bird Michael W. George 《Applied Intelligence》2007,27(3):237-248
Recently Fourier Transform Infrared (FTIR) spectroscopic imaging has been used as a tool to detect the changes in cellular
composition that may reflect the onset of a disease. This approach has been investigated as a mean of monitoring the change
of the biochemical composition of cells and providing a diagnostic tool for various human cancers and other diseases. The
discrimination between different types of tissue based upon spectroscopic data is often achieved using various multivariate
clustering techniques. However, the number of clusters is a common unknown feature for the clustering methods, such as hierarchical
cluster analysis, k-means and fuzzy c-means. In this study, we apply a FCM based clustering algorithm to obtain the best number
of clusters as given by the minimum validity index value. This often results in an excessive number of clusters being created
due to the complexity of this biochemical system. A novel method to automatically merge clusters was developed to try to address
this problem. Three lymph node tissue sections were examined to evaluate our new method. These results showed that this approach
can merge the clusters which have similar biochemistry. Consequently, the overall algorithm automatically identifies clusters
that accurately match the main tissue types that are independently determined by the clinician. 相似文献
9.
10.
MG Fehlings T Errico P Cooper V Benjamin T DiBartolo 《Canadian Metallurgical Quarterly》1993,32(2):198-207; discussion 207-8
Although occipitocervical fusion is frequently used for instability of the upper cervical spine and the occipitocervical articulation, most currently used techniques have one or more of the following disadvantages: the necessity for sublaminar wires, the use of occipital screws, a fixed angle of instrumentation, or the necessity for routine postoperative halo immobilization. Moreover, many reported techniques are associated with a high rate of nonunion or instrumentation failure. We present our experience with a technically simple method of obtaining rigid occipitocervical arthrodesis using a 5-mm malleable rod that is fixed to the skull by a pair of wires passed through four suboccipital burr holes. Segmental spinal fixation is achieved with Wisconsin interspinous wires and is occasionally supplemented with sublaminar wires. Supplemental autogenous bone graft is used in all cases. A cervical collar is routinely used for postoperative immobilization. The results of treatment were retrospectively reviewed in 16 patients with an average age of 49.4 years (range, 9-69). Mean follow-up was 24 months (range, 12-36 mo). The indication for fusion was instability of the occiput-C1-C2 complex as a result of Chiari malformation, rheumatoid disease, skull base tumor resection, basilar invagination, ankylosing spondylitis, Down's syndrome, cervical laminectomy, and trauma. The average number of levels fused was 5.4 (range, O-C3 to O-T3). Successful occipitocervical arthrodesis was achieved in all but one of the surviving patients. The single patient with a pseudarthrosis was successfully managed with supplemental bone grafting and halo immobilization. There were two deaths from medical complications in chronically ill patients. Other complications included one postoperative instrumentation loosening, one myocardial infarction, and one superficial occipital decubitus. In conclusion, rodding and segmental interspinous wiring is an effective, technically simple method of obtaining rigid occipitocervical fixation, which obviates the need for bulky orthoses. 相似文献