全文获取类型
收费全文 | 98787篇 |
免费 | 1619篇 |
国内免费 | 464篇 |
专业分类
电工技术 | 939篇 |
综合类 | 2343篇 |
化学工业 | 14108篇 |
金属工艺 | 5029篇 |
机械仪表 | 3288篇 |
建筑科学 | 3106篇 |
矿业工程 | 618篇 |
能源动力 | 1546篇 |
轻工业 | 4911篇 |
水利工程 | 1435篇 |
石油天然气 | 411篇 |
武器工业 | 1篇 |
无线电 | 10312篇 |
一般工业技术 | 18861篇 |
冶金工业 | 5955篇 |
原子能技术 | 335篇 |
自动化技术 | 27672篇 |
出版年
2023年 | 72篇 |
2022年 | 139篇 |
2021年 | 266篇 |
2020年 | 194篇 |
2019年 | 207篇 |
2018年 | 14683篇 |
2017年 | 13569篇 |
2016年 | 10252篇 |
2015年 | 890篇 |
2014年 | 690篇 |
2013年 | 1137篇 |
2012年 | 3848篇 |
2011年 | 10326篇 |
2010年 | 8978篇 |
2009年 | 6218篇 |
2008年 | 7550篇 |
2007年 | 8542篇 |
2006年 | 817篇 |
2005年 | 1832篇 |
2004年 | 1677篇 |
2003年 | 1631篇 |
2002年 | 1055篇 |
2001年 | 439篇 |
2000年 | 508篇 |
1999年 | 350篇 |
1998年 | 558篇 |
1997年 | 407篇 |
1996年 | 334篇 |
1995年 | 304篇 |
1994年 | 281篇 |
1993年 | 285篇 |
1992年 | 211篇 |
1991年 | 137篇 |
1990年 | 168篇 |
1989年 | 158篇 |
1988年 | 149篇 |
1987年 | 147篇 |
1986年 | 102篇 |
1985年 | 163篇 |
1984年 | 148篇 |
1983年 | 104篇 |
1982年 | 79篇 |
1981年 | 81篇 |
1980年 | 67篇 |
1979年 | 66篇 |
1978年 | 57篇 |
1977年 | 55篇 |
1976年 | 81篇 |
1955年 | 64篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The viscous damping coefficient(VDC) of hydraulic actuators is crucial for system modeling,control and dynamic characteristic analysis.Currently,the researches on hydraulic actuators focus on behavior assessment,promotion of control performance and efficiency.However,the estimation of the VDC is difficult due to a lack of study.Firstly,using two types of hydraulic cylinders,behaviors of the VDC are experimentally examined with velocities and pressure variations.For the tested plunger type hydraulic cylinder,the exponential model B=αυ~(-β),(α0,β0)or B=α_1e~(-β_1υ)+α_2e~(-β_2υ)(α_1,α_20,β_1,β_20),fits the relation between the VDC and velocities for a given pressure of chamber with high precision.The magnitude of the VDC decreases almost linearly under certain velocities when increasing the chamber pressure from 0.6 MPa to 6.0 MPa.Furthermore,the effects of the chamber pressures on the VDC of piston and plunge type hydraulic cylinders are different due to different sealing types.In order to investigate the VDC of a plunger type hydraulic actuator drastically,a steady-state numerical model has been developed to describe the mechanism incorporating tandem seal lubrication,back-up ring related friction behaviors and shear stress of fluid.It is shown that the simulated results of VDC agree with the measured results with a good accuracy.The proposed method provides an instruction to predict the VDC in system modeling and analysis. 相似文献
992.
This paper presents the results of studies of wall effects in commercial soap-based greases LT4-S2 and HUTPLEX EP-2, thickened with, respectively, lithium 12-hydroxystearate and overbased calcium sulfonate. The studies were conducted in the presence of five different materials: copper alloy C11000, bronze B476, EPDM rubber and PTFE and PU thermoplastics. The influence of the energy state of the surface layer of the adsorbents and temperature (ranging from ?20 to 60 °C) on the intensity of wall effects was investigated. Changes in the structural viscosity and shear stress in the boundary layer area in the greases and the soap-based thickener’s ability to adsorb on the surfaces of the adsorbents were determined by evaluating the rheological parameter plateau modulus. 相似文献
993.
Janine Glänzel Arnd Meyer Roman Unger Michael Bräunig Volker Wittstock Steffen Ihlenfeldt 《The International Journal of Advanced Manufacturing Technology》2017,88(5-8):1279-1288
A new interdisciplinary approach is discribed to identifying unknown parameters using an extended version of the known interval bisection method. This developed method is based on the use of finite elements for calibrating the simulation calculation. The resulting thermo-elastic deformations which occur in drilling processes with impaired cooling lubrication are to be used as correction values for tool positioning in the NC control. Based on the strong impact on workpiece temperature of machining, a simulation approach is presented for calculating the temperature fields and their thermo-elastic consequences. In addition, methods are presented to correct these effects. This paper particularly deals with the temperature fields of drilling operations. Special attention is paid to the technique employed for iterative numerical determination of the unknown heat flux η w and heat transfer coefficient \(\bar {\gamma }\) values. Finally, the data obtained from experiments are compared with those achieved by numerical simulation in order to verify the efficiency of simulation and determination of parameters. 相似文献
994.
Definition of the problem Ethics cafés in long-term geriatric care are considered as ethical education. They allow the participants to have an open discourse in a casual setting about moral issues related to daily work. In the literature, various characteristics are attributed to ethics cafés, e.g., improving analytical skills and communication, increasing ethical sensitivity and authority for making decisions. These characteristics primarily result from theory-based models. Arguments The goal of this study is the empirical investigation of the effectiveness of ethics cafés in the Nursing Homes Mattenhof–Irchelpark, Zurich. Furthermore, the study examined whether the subjective evaluation of characteristics of nurses and other professional groups are different. To capture the characteristics, a questionnaire was constructed in which the participants rated 16 statements during the survey period. A 5-point Likert scale was used for the analysis. One subgroup distinguished between “nursing staff” and “non-nursing staff”. Conclusion The postulated characteristics were confirmed with a very high approval. Therefore, the ethics cafés provide important input which enable the staff to analyze more clearly in difficult situations or to let them decide ethically in a more sensitive manner and to justify decisions made. The interdisciplinary approach supports an understanding of the views and arguments among the various areas and hierarchies. The differences between the two professionals groups are partially highly significant. It can be noted that the assigned characteristics in the questionnaire are generally perceived stronger and more significantly by the nursing staff. Therefore, a distinction must be made when interpreting the results of this study concerning the participants. 相似文献
995.
Nina Streeck 《Ethik in der Medizin》2016,28(2):135-148
Definition of the problem This article takes a critical look at the current theory and practice of palliative care (PC), how it deals with death and dying, and the underlying guiding principle of a good death. Thereby, Foucault’s concept of biopower is utilized. Argument Because PC aims to facilitate a good death, manifold criteria and measures have been developed that help plan interventions and determine their success. In light of the concept of biopower, certain problematic aspects of this development become manifest that usually remain hidden in the bioethical discourse. Conclusion A goal of PC is to improve the quality of life of the dying and therefore not only treats physical symptoms but also psychological, social, and spiritual suffering; thus, it commits itself to maximizing life in a way that can become overdemanding for the individual and possibly does not satisfy the patient’s real needs. 相似文献
996.
Dieter Birnbacher 《Ethik in der Medizin》2016,28(4):283-294
Definition of the problem
Advance directives for later states of grave cognitive impairment that are typical for late stages of dementia meet with more far-reaching reservations than advance directives for other states of reduced competence. One of the reasons seems to lie in the ethical and psychological conflicts arising from advance directives demanding nontreatment of additional diseases or the abstention from artificial nutrition in situations in which patients show no signs of suffering from their condition.Arguments
In this article, it is argued that a “mixed” ethical strategy be used for these cases.Conclusion
Advance directives in the legally defined sense, especially if drawn up in a process of advance care planning, should be followed in order to avoid that advance directives as an instrument of patient autonomy are rendered futile to a degree incompatible with confidence that wishes for terminating medical treatment will be followed. In contrast, the authority of “care directives” without recognized legal status should be restricted to cases in which there is concordance between the patient’s will as expressed in the directive and the patient’s “natural” will in the relevant situation.997.
Definition of the problem
Full age patients with mental disorders and preserved decision-making capacity are increasingly interested in drafting advance directives. Whereas in Switzerland (as well as in Germany) advance directives are binding in principle, an advance directive is not binding and has only to be considered in case of involuntary admission due to a mental disorder. Thereby, the virtual aim of an advance directive – the anticipated self-determination – is questioned.Arguments
From an ethical perspective, patients with mental disorders have the same rights as patients with somatic diseases. Therefore, the question arises if there are good reasons for this unequal treatment. In the present contribution, four possible reasons are analyzed: (1) persons with mental disorders are “different”; (2) protection from self-harm; (3) often not present end-of-life context; (4) reduced bindingness as the more appropriate standard in general.Conclusion
The authors come to the conclusion that patients with mental disorders are often capable of composing a valid advance directive, and just as any other human being, they have a principal and binding right for self-determination, even though they are particularly vulnerable in crisis situations.998.
Definition of the problem
In Germany as well as in many other countries, mentally ill criminals who are not guilty by reasons of insanity can be sentenced to psychiatric treatment in forensic clinics. In 2011, the German Constitutional Court substantially strengthened these patients’ right to self-determination in case of treatment refusal.Arguments
In this context, we discuss the significance of instruments of advance healthcare planning. First, we describe the context of psychiatric treatment in forensic clinics and the changes the new German legal regulations brought about. A case study helps to illustrate the consequences of treatment refusal for both patient and healthcare personnel.Conclusion
Eventually, we discuss if and how advance directives and joint crisis plans can be useful in forensic clinics and how additional measures can help to facilitate patient self-determination.999.
The Cu x Si1-x thin films have been grown by pulsed laser deposition (PLD) with in situ annealing on Si (001) and Si (111), respectively. The transformation of phase was detected by X-ray diffraction (XRD). The results showed that the as-deposited films were composed of Cu on both Si (001) and Si (111). The annealed thin films consisted of Cu + η”-Cu3Si on Si (001) while Cu + η’-Cu3Si on Si (111), respectively, at annealed temperature (T a) = 300-600 °C. With the further increasing of T a, at T a= 700 °C, there was only one main phase, η”-Cu3Si on Si (001) while η’-Cu3Si on Si (111), respectively. The annealed thin films transformed from continuous dense structure to scattered-grain morphology with increasing T a detected by field emission scanning electron microscope (FESEM). It was also showed that the grain size would enlarge with increasing annealing time (t a). 相似文献
1000.
刘转年 《武汉理工大学学报(材料科学英文版)》2016,31(1):58-63
Forming adsorbents FFA-R, FFA-A and FFA-B were prepared from different particle size coal fly ashes FA-R, FA-A and FA-B, their average particle sizes (d 50) were 15.75, 3.61 and 1.73 μm respectively. The structure and adsorption properties for Cr6+ of forming adsorbents from aqueous solution were studied. The results show that forming adsorbent prepared from the coal fly ash with smaller particle size exhibits higher specific surface area, higher pore volume and better adsorption properties for Cr6+.The adsorption kinetics of Cr6+ on FFA-R, FFA-A and FFA-B fitts the second order kinetic model and the second adsorption rate constants are 7.523, 3.197 and 2.187 mg·g-1· min-1/2, respectively. The adsorption of Cr6+ on FFA-R, FFA-A and FFA-B can be described in terms of Langmuir isotherms better, and the adsorption processes are spontaneous and exothermic. 相似文献