全文获取类型
收费全文 | 1553篇 |
免费 | 41篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 36篇 |
综合类 | 2篇 |
化学工业 | 418篇 |
金属工艺 | 33篇 |
机械仪表 | 15篇 |
建筑科学 | 88篇 |
矿业工程 | 8篇 |
能源动力 | 28篇 |
轻工业 | 249篇 |
水利工程 | 10篇 |
石油天然气 | 1篇 |
无线电 | 70篇 |
一般工业技术 | 233篇 |
冶金工业 | 251篇 |
原子能技术 | 7篇 |
自动化技术 | 147篇 |
出版年
2021年 | 32篇 |
2020年 | 24篇 |
2019年 | 28篇 |
2018年 | 21篇 |
2017年 | 14篇 |
2016年 | 30篇 |
2015年 | 29篇 |
2014年 | 37篇 |
2013年 | 52篇 |
2012年 | 50篇 |
2011年 | 66篇 |
2010年 | 60篇 |
2009年 | 44篇 |
2008年 | 47篇 |
2007年 | 57篇 |
2006年 | 45篇 |
2005年 | 35篇 |
2004年 | 38篇 |
2003年 | 35篇 |
2002年 | 33篇 |
2001年 | 14篇 |
2000年 | 29篇 |
1999年 | 13篇 |
1998年 | 34篇 |
1997年 | 39篇 |
1996年 | 26篇 |
1995年 | 24篇 |
1994年 | 26篇 |
1993年 | 26篇 |
1992年 | 35篇 |
1991年 | 19篇 |
1990年 | 30篇 |
1989年 | 22篇 |
1988年 | 14篇 |
1987年 | 23篇 |
1986年 | 13篇 |
1985年 | 29篇 |
1984年 | 24篇 |
1983年 | 23篇 |
1982年 | 17篇 |
1981年 | 22篇 |
1978年 | 23篇 |
1977年 | 17篇 |
1976年 | 18篇 |
1974年 | 13篇 |
1973年 | 12篇 |
1972年 | 16篇 |
1970年 | 14篇 |
1963年 | 13篇 |
1943年 | 12篇 |
排序方式: 共有1596条查询结果,搜索用时 453 毫秒
1.
Konstantinos Spyrou Matteo Calvaresi Evmorfia K. Diamanti Theodoros Tsoufis Dimitrios Gournis Petra Rudolf Francesco Zerbetto 《Advanced functional materials》2015,25(2):263-269
Experimental and theoretical studies are performed in order to illuminate, for first time, the intercalation mechanism of polycyclic aromatic molecules into graphite oxide. Two representative molecules of this family, aniline and naphthalene amine are investigated. After intercalation, aniline molecules prefer to covalently connect to the graphene oxide matrix via chemical grafting, while napthalene amine molecules bind with the graphene oxide surface through π–π interactions. The presence of intercalated aromatic molecules between the graphene oxide layers is demonstrated by X‐ray diffraction, while the type of interaction between graphene oxide and polycyclic organic molecules is elucidated by X‐ray photoelectron spectroscopy. Combined quantum mechanical and molecular mechanical calculations describe the intercalation mechanism and the aniline grafting, rationalizing the experimental data. The present work opens new perspectives for the interaction of various aromatic molecules with graphite oxide and the so‐called “intercalation chemistry”. 相似文献
2.
3.
Rudolf Habison 《International Journal of Project Management》1985,3(3):178-181
Meeting time and cost objectives in complex projects involves specific problems and risks. An attempt is made to analyse the components of total cost increase of a project caused by time delay. An outline is given as to how these considerations can be used to estimate cost increases in investors' decision situations as well as to ascertain fair contractual penalties and claims for compensation and for the evaluation of justified project acceleration costs. 相似文献
4.
5.
6.
7.
HU Rothen B Sporre G Engberg G Wegenius M H?gman G Hedenstierna 《Canadian Metallurgical Quarterly》1995,82(4):832-842
BACKGROUND: Atelectasis, an important cause of impaired gas exchange during general anesthesia, may be eliminated by a vital capacity maneuver. However, it is not clear whether such a maneuver will have a sustained effect. The aim of this study was to determine the impact of gas composition on reappearance of atelectasis and impairment of gas exchange after a vital capacity maneuver. METHODS: A consecutive sample of 12 adults with healthy lungs who were scheduled for elective surgery were studied. Thirty minutes after induction of anesthesia with fentanyl and propofol, the lungs were hyperinflated manually up to an airway pressure of 40 cmH2O. FIO2 was either kept at 0.4 (group 1, n = 6) or changed to 1.0 (group 2, n = 6) during the recruitment maneuver. Atelectasis was assessed by computed tomography. The amount of dense areas was measured at end-expiration in a transverse plane at the base of the lungs. The ventilation-perfusion distributions (VA/Q) were estimated with the multiple inert gas elimination technique. The static compliance of the total respiratory system (Crs) was measured with the flow interruption technique. RESULTS: In group 1 (FIO2 = 0.4), the recruitment maneuver virtually eliminated atelectasis for at least 40 min, reduced shunt (VA/Q < 0.005), and increased at the same time the relative perfusion to poorly ventilated lung units (0.005 < VA/Q < 0.1; mean values are given). The arterial oxygen tension (PaO2) increased from 137 mmHg (18.3 kPa) to 163 mmHg (21.7 kPa; before and 40 min after recruitment, respectively; P = 0.028). In contrast to these findings, atelectasis recurred within 5 min after recruitment in group 2 (FIO2 = 1.0). Comparing the values before and 40 min after recruitment, all parameters of VA/Q were unchanged. In both groups, Crs increased from 57.1/55.0 ml.cmH2O-1 (group 1/group 2) before to 70.1/67.4 ml.cmH2O-1 after the recruitment maneuver. Crs showed a slow decrease thereafter (40 min after recruitment: 61.4/60.0 ml.cmH2O-1), with no difference between the two groups. CONCLUSIONS: The composition of inspiratory gas plays an important role in the recurrence of collapse of previously reexpanded atelectatic lung tissue during general anesthesia in patients with healthy lungs. The reason for the instability of these lung units remains to be established. The change in the amount of atelectasis and shunt appears to be independent of the change in the compliance of the respiratory system. 相似文献
8.
9.
R. Bunk U. Leske R. Krompass Z. Pretch K. Rudolf R. Herbig K. Pitch V. A. Tsykanov O. V. Skiba V. A. Makarov L. P. Bol'shakov P. T. Porodnov A. A. Maershin S. S. Keruchen'ko 《Atomic Energy》1989,67(5):802-806
Translated from Atomnaya Énergiya, Vol. 67, No. 5, pp. 320–323, November, 1989. 相似文献
10.
This paper reports on an evaluation of real-time properties of MAP (Manufacturing Automation Protocol) networks by analytical considerations and measurements. Based on a model of the time schedule of a communication cycle figures for response times (transport system) and message delays (MAC layer) are given. The influence of some options for handling acknowledgments within the transport layer is shown. The message delay at MAC layer is separated into an implementation-dependent and a protocol-dependent protion, and an upper bound is derived. Rules for selecting protocol parameters affecting real time behavior are given. Aspects for improved implementations of communication controllers for MAP networks are discussed. 相似文献