全文获取类型
收费全文 | 5111篇 |
免费 | 147篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 77篇 |
综合类 | 5篇 |
化学工业 | 1008篇 |
金属工艺 | 120篇 |
机械仪表 | 74篇 |
建筑科学 | 203篇 |
矿业工程 | 27篇 |
能源动力 | 97篇 |
轻工业 | 399篇 |
水利工程 | 42篇 |
石油天然气 | 23篇 |
无线电 | 467篇 |
一般工业技术 | 853篇 |
冶金工业 | 1193篇 |
原子能技术 | 84篇 |
自动化技术 | 587篇 |
出版年
2022年 | 42篇 |
2021年 | 58篇 |
2020年 | 48篇 |
2019年 | 51篇 |
2018年 | 58篇 |
2017年 | 67篇 |
2016年 | 73篇 |
2015年 | 73篇 |
2014年 | 94篇 |
2013年 | 264篇 |
2012年 | 166篇 |
2011年 | 190篇 |
2010年 | 158篇 |
2009年 | 145篇 |
2008年 | 216篇 |
2007年 | 176篇 |
2006年 | 180篇 |
2005年 | 140篇 |
2004年 | 149篇 |
2003年 | 139篇 |
2002年 | 134篇 |
2001年 | 94篇 |
2000年 | 101篇 |
1999年 | 117篇 |
1998年 | 254篇 |
1997年 | 186篇 |
1996年 | 165篇 |
1995年 | 90篇 |
1994年 | 111篇 |
1993年 | 97篇 |
1992年 | 74篇 |
1991年 | 56篇 |
1990年 | 55篇 |
1989年 | 48篇 |
1988年 | 80篇 |
1987年 | 57篇 |
1986年 | 50篇 |
1985年 | 65篇 |
1984年 | 61篇 |
1983年 | 46篇 |
1982年 | 48篇 |
1981年 | 55篇 |
1980年 | 43篇 |
1979年 | 37篇 |
1978年 | 52篇 |
1977年 | 67篇 |
1976年 | 78篇 |
1975年 | 45篇 |
1974年 | 34篇 |
1972年 | 36篇 |
排序方式: 共有5259条查询结果,搜索用时 15 毫秒
31.
PATIENT: A 14-year-old boy suffered from an acute bilateral blindness which occurred in 24-h time, accompanied by headache and raised temperature, with inconspicuous optic nerve head and fundus. After diagnosis of empyema with magnet resonance tomography (MRT) the sphenoid sinus was fenestrated and streptococcus pneumoniae isolated. Liquor and serology being inconspicuous, there was no evidence of leucaemic or autoimmune disease, intoxication or intracranial tumor. CLINICAL COURSE: The condition of the patient improved under systemic antibiotic therapy. The bilateral amaurosis remained and opticus atrophy developed. CONCLUSION: A bilateral amaurosis with descending opticus atrophy as a consequence of a sphenoiditis and spreading inflammation to the meninges and the optic nerve in the area of the chiasm is a rare event. The imaging technique of the MRT offers new opportunities for an early and more pointed diagnosis and therapy. 相似文献
32.
The growing involvement of psychologists in the management of human services, particularly in the public sector, has not been reflected in the development of corresponding academic or practicum training focusing on issues of service delivery. This article gives an overview of the practitioner-manager role and develops a rationale for management-oriented training in doctoral programs. An introductory course is briefly noted, and a review of models, knowledge and skills, and training resources is provided. Also described are practitioner-manager trends, training alternatives, and competing demands of the graduate curriculum. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
33.
Several areas of current interest in the neuropsychology of epilepsy are briefly reviewed in this article. These include variables pertaining to seizures, seizure history, antiepileptic drugs, and methods of neuropsychological evaluation. It is apparent that epilepsy is a multifaceted area: Psychologists not only can be of great assistance to patients with this condition, but may also learn a great deal from this complex disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
34.
M WünschB.A Wolf 《Polymer》2002,43(18):5027-5034
Vapor pressures, phase equilibria and interfacial tensions σ were measured for solutions of poly(dimethylsiloxane) (PDMS, Mw[equals]75 kg/mol and Mn[equals]50 kg/mol) in mixed solvents of toluene (TL) and ethanol (EtOH) at 30, 40, 50 and 60 °C. The experimental ternary phase diagrams can be modeled quantitatively from the determined concentration and temperature dependent binary interaction parameters χij if the experimentally inaccessible composition dependence of χEtOH/PDMS is adjusted. The relations between σ and the equation of state of the system differ from that applying to single solvents. The exponents as well as the amplitude prefactors of the corresponding scaling laws (e.g. the dependencies of σ on the length of the tie lines or on the hump energy, i.e. on the intrusion into the two phase regime quantified in terms of Gibbs energies) change considerably with temperature. However, this variation can be reduced significantly by normalizing the independent variables. Dividing the length of the tie lines by the length for the corresponding binary subsystem proves more efficient than the distance of these tie lines from the critical point of the ternary system relative to the maximum distance of the binary subsystem. A combined normalization does not improve the situation. 相似文献
35.
Takach A. Wolf W. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》1995,3(2):215-230
This paper describes a new algorithm for generation of scheduling constraints in networks of communicating processes. Our model of communication intertwines the schedules of the machines in the network: timing constraints of a machine may affect the schedules of machines communicating with it. This model of communication facilitates the modular specification of timing constraints. A feasible solution to the set of constraints generated gives a schedule for each machine in the network such that all internal constraints of each machine are satisfied and communication between machines is statically coordinated whenever possible. Static scheduling of communication saves on the cost of handshake associated with dynamic synchronization. Our algorithm can handle complex, state-dependent and cyclic timing constraints. Experimental results show that our algorithm is both effective and efficient 相似文献
36.
Carl Bruch Stephanie Altman Mishkat Al-Moumin Jessica Troell Elana Roffman 《国际水资源开发杂志》2007,23(4):595-624
For millennia, countries in the Middle East and North Africa (MENA) region have developed laws, regulations and other rules to govern their scarce water. These laws have been updated in recent years. This review of the legal frameworks (including regulations, decrees and other rules) reveals both progress and gaps in managing water quality, water quantity and procedural aspects. Of note, while the general frameworks are usually in place, in many instances the necessary details are lacking to give effect to the goals. However, in some instances the legal frameworks governing water lack certain key principles or approaches. In order to effectively meet the growing demands on their water resources, MENA countries will need to further strengthen and develop their legal frameworks. 相似文献
37.
Tihanyi P. Wagner D.K. Vollmer H.J. Roza A.J. Harding C.M. Davis R.J. Wolf E.D. 《Electronics letters》1987,23(15):772-773
We demonstrate, for the first time, laser diodes with anetched facet fabricated by chemically assisted ion beametching, producing 1?7 W pulsed and 470mW CW output power from one facet. The devices were coated and bonded junction-side-up and tested at room temperature. The single 40 ?m stripe, 300 ?m-long devices exhibit 94 mA threshold current and differential quantum efficiencies of 80% pulsed (78% CW). 相似文献
38.
Carl A. Soderstrom Patricia C. Dischinger Gordon S. Smith J.Richard Hebel David R. McDuff David A. Gorelick Timothy J. Kerns Shiu M. Ho Kathleen M. Read 《Accident; analysis and prevention》1997,29(6):715-721
A structured in-depth interview employing standardized criteria was used to determine the prevalence of lifetime and current alcohol dependence (alcoholism) in unselected consecutive patients admitted to a regional Level I trauma center. Of 629 patients, 157 (25.0%) were current alcoholics at the time of injury. An additional 87 (13.8%) were diagnosed as lifetime non-current alcoholics. There was no significant difference in the rates of current alcohol dependence among patients injured in vehicular crashes (23.5%), other unintentional trauma victims (29.3%), and those injured as a result of violence (24.6%). Of BAC + (blood alcohol concentration positive) patients, 54.5% were current alcoholics. However, 14.4% of alcohol-negative patients were also diagnosed as alcohol dependent. 相似文献
39.
R Germann M Haisjackl B Schwarz N Salak E Deusch W Pajk HJ Wolf B Riedmann W Hasibeder 《Canadian Metallurgical Quarterly》1997,79(3):357-362
Haemorrhage is associated with intestinal mucosal hypoxia and impaired gut barrier function. Dopamine increases oxygen delivery to the intestinal mucosa and may thus counteract haemorrhage-induced mucosal hypoxia. Jejunal mucosal tissue oxygen tension (mucosal PO2) and jejunal oxygen saturation of mucosal microvascular haemoglobin (mucosal HbO2) were measured in 14 anaesthetized pigs. Seven animals served as controls (group C) and seven received continuous infusion of dopamine 16 micrograms kg-1 min-1 (group D) while 45% of blood volume was removed in three equal increments. Resuscitation was performed using shed blood and fluid. Mean arterial pressure and systemic oxygen delivery decreasing significantly during haemorrhage and returned to baseline after resuscitation in both groups. Mucosal PO2 decreased from 4.4 to 1.7 kPa after haemorrhage (P < 0.01) and further to 1.5 kPa after resuscitation (P < 0.01) in group C whereas group D showed an increase from 3.9 to 5.9 kPa after the start of the dopamine infusion (P < 0.05), but no significant difference from baseline after haemorrhage (2.3 kPa) (ns) or resuscitation (3.1 kPa) (ns). Mucosal HbO2 decreased from 52 to 32% after haemorrhage (P < 0.05) and increased to near baseline (37%) (ns) after resuscitation in group C whereas group D showed no significant changes from baseline (54%) throughout the experiment. Comparison between groups showed higher mucosal PO2 and HbO2 values for group D animals after the start of the dopamine infusion (P < 0.05 each), after the first two steps of haemorrhage (P < 0.01 each) and after resuscitation (P < 0.05 each). We conclude that i.v. dopamine 16 micrograms kg-1 min-1 improved tissue oxygenation of the small intestinal mucosa during moderate haemorrhage and subsequent resuscitation. 相似文献
40.
F. L. Schmidt and J. E. Hunter (1989) critiqued the within-group interrater reliability statistic (rwg) described by L. R. James et al (1984). S. W. Kozlowski and K. Hattrup (1992) responded to the Schmidt and Hunter critique and argued that rwg is a suitable index of interrater agreement. This article focuses on the interpretation of rwg as a measure of agreement among judges' ratings of a single target. A new derivation of rwg is given that underscores this interpretation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献