全文获取类型
收费全文 | 5074篇 |
免费 | 96篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 51篇 |
综合类 | 3篇 |
化学工业 | 792篇 |
金属工艺 | 55篇 |
机械仪表 | 73篇 |
建筑科学 | 133篇 |
矿业工程 | 13篇 |
能源动力 | 82篇 |
轻工业 | 357篇 |
水利工程 | 22篇 |
石油天然气 | 22篇 |
无线电 | 508篇 |
一般工业技术 | 665篇 |
冶金工业 | 1766篇 |
原子能技术 | 58篇 |
自动化技术 | 574篇 |
出版年
2022年 | 30篇 |
2021年 | 41篇 |
2020年 | 33篇 |
2019年 | 28篇 |
2018年 | 42篇 |
2017年 | 37篇 |
2016年 | 40篇 |
2015年 | 36篇 |
2014年 | 84篇 |
2013年 | 199篇 |
2012年 | 137篇 |
2011年 | 142篇 |
2010年 | 118篇 |
2009年 | 120篇 |
2008年 | 143篇 |
2007年 | 168篇 |
2006年 | 127篇 |
2005年 | 126篇 |
2004年 | 112篇 |
2003年 | 115篇 |
2002年 | 101篇 |
2001年 | 94篇 |
2000年 | 98篇 |
1999年 | 123篇 |
1998年 | 493篇 |
1997年 | 283篇 |
1996年 | 233篇 |
1995年 | 152篇 |
1994年 | 151篇 |
1993年 | 146篇 |
1992年 | 91篇 |
1991年 | 62篇 |
1990年 | 73篇 |
1989年 | 70篇 |
1988年 | 63篇 |
1987年 | 56篇 |
1986年 | 55篇 |
1985年 | 77篇 |
1984年 | 65篇 |
1983年 | 81篇 |
1982年 | 64篇 |
1981年 | 56篇 |
1980年 | 58篇 |
1979年 | 51篇 |
1978年 | 45篇 |
1977年 | 69篇 |
1976年 | 95篇 |
1975年 | 39篇 |
1973年 | 34篇 |
1972年 | 30篇 |
排序方式: 共有5174条查询结果,搜索用时 15 毫秒
21.
Antidepressant-induced adverse sexual effects are becoming more frequently reported by patients who require pharmacotherapy. A MED-LINE search was conducted to generate articles reporting such events. We report here on the sexual side effects associated with tricyclics, monoamine oxidase inhibitors including moclobemide, selective serotonin reuptake inhibitors, bupropion, and on the newer antidepressants venlafaxine and nefazadone. We conclude that adverse sexual effects are an increasingly important side effect of antidepressant medications, and patients must be routinely asked about their occurrence. 相似文献
22.
23.
M Davis 《Canadian Metallurgical Quarterly》1998,44(12):1239-1247
Although there is a close correspondence between fear and anxiety, and the study of fear in animals has been extremely valuable for understanding brain systems that are important for anxiety, it is equally clear that a richer animal model of human anxiety disorders would include measures of both stimulus-specific fear and something less stimulus specific, more akin to anxiety. Studies in patients with posttraumatic stress syndrome indicate these individuals seem to show normal fear reactions but abnormal anxiety measured with the acoustic startle reflex. Studies in rats, also using the startle reflex, indicate that highly processed explicit cue information (lights, tones, touch) activates the central nucleus of the amygdala, which in turn activates hypothalamic and brain stem target areas involved in specific signs of fear. Somewhat less explicit information, such as that produced by exposure to a threating environment for several minutes or by intraventricular administration of the peptide corticotropin-releasing hormone may activate a brain area closely related to the amygdala, called the bed nucleus of the stria terminalis, which in turn activates hypothalamic and brain stem target areas involved in specific signs of fear or anxiety. Because the nature of this information may be less specific than that produced by an explicit cue, and of much longer duration, activation of the bed nucleus of the stria terminalis may be more akin to anxiety than to fear. 相似文献
24.
BACKGROUND: Despite recognition of the high prevalence of alcoholism among patients with head and neck cancer, the prognostic importance of alcoholism has not been evaluated adequately. Previous investigators have speculated that alcoholic patients may have a poorer prognosis than nonalcoholic patients because of more advanced stage of cancer, the immunosuppressive effects of alcohol, and an increased rate of death due to other alcohol-related diseases. PURPOSE: The goal of this population-based study was to identify the features of alcoholism that are associated with survival for patients with head and neck cancer and to develop an alcoholic severity staging system from a composite of the independent features of alcoholism. METHODS: This prospective study included 649 patients who were diagnosed with cancer of the oral cavity, oropharynx, hypopharynx, or larynx during the period from September 1, 1983, through February 28, 1987, in a three-county area of western Washington state that participates in the Surveillance, Epidemiology, and End Results Program of the U.S. National Cancer Institute. Details on lifetime alcohol consumption, treatment for alcoholism, abstinence from alcohol prior to the diagnosis of cancer, and alcohol-related health problems were ascertained through in-person interviews near the time of diagnosis. Patients were classified as either nonalcoholics or alcoholics according to their responses to questions from the Michigan Alcoholism Screening Test. The measures of alcohol consumption and abuse that were found to be independently associated with 5-year survival by logistic regression analysis were combined using conjunctive consolidation to create a final composite variable, called an alcoholic severity stage. Cox proportional hazards regression analysis was done to estimate the relative risk (R) of death within 5 years due to specific causes of death for each of the alcoholic severity stages. RESULTS: Alcoholism (RR = 2.06; 95% confidence interval [CI] = 1.43-2.98) and a history of alcohol-related systemic health problems (i.e., liver disease, pancreatitis, delirium tremens, or seizures) (RR = 2.76; 95% CI = 1.69-4.49) were associated with an increased risk of death, whereas abstinence (i.e., the consumption of fewer than one drink per week at 1 year prior to the diagnosis of cancer) (RR = 0.62; 95% CI = 0.39-0.97) was associated with a decreased risk of death. These associations were independent of age, site of cancer, anatomical stage, histopathologic grade, smoking, and type of antineoplastic treatment. Patients in the two worst alcoholic severity stages had an increased risk of dying not only of head and neck cancer but also of cardiovascular disease, pulmonary disease, and other alcohol-related causes. CONCLUSIONS: Alcohol abuse, measured by alcohol consumption, functional impairment, a history of alcohol-related health problems, or abstinence, can provide important prognostic information for patients with head and neck cancer. Our results suggest that sobriety among alcoholic patients can lead to prolonged survival. 相似文献
25.
Transient hot-electron effect and its impact on circuit reliability are investigated. The rate of device decay is monitored as a function of the gate pulse transient period. Simulation results reveal that excess charges during a fast turn off time may cause an increase in the maximum substrate current. This, along with our experimental data, identifies that transient excess carrier may cause the enhancement of device degradation under certain stress conditions. The enhancement factor of the degradation is a function of the gate pulse transient time. Correlation between the analysis based upon AC/DC measurement and calculations based upon transient simulation are shown in the paper. Better agreement with experimental data is obtained by using the transient analysis and on chip test/stress structures. The correlation between AC and DC stress data is also shown based on the impact ionization model. A hot-electron design guideline is proposed based on the circuit reliability analysis. This guideline can help improve the circuit reliability without adversely effecting the circuit performance. 相似文献
26.
27.
Ashmead Daniel H.; Davis DeFord L.; Northington Anna 《Canadian Metallurgical Quarterly》1995,21(2):239
Of the several sources of acoustic information for distance perception, those arising from motion of the listener or sound source have received little attention. This motion-related information (recently called acoustic tau) is described, and experiments evaluating its utilization are presented. Accuracy and consistency at walking to the locations of briefly presented sounds were better when people listened while walking than while standing still. Manipulations of the sound to simulate shorter or longer target distances produced appropriate undershooting but not overshooting. The results indicate that people use motion-related acoustic information about distance to guide their locomotor actions, although they do not take full advantage of this information. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
28.
Administration of footshock (500-ms duration, 0.2–2.4 mA) increased the amplitude of the startle reflex for a long time after its presentation. The effect occurred with a single footshock, although its magnitude and consistency across animals were greater with 5 or 10 footshocks presented 1/s. The facilitatory effect came on within 2–4 min with a 0.6-mA shock, peaking in about 10 min and then dissipating over the next 40 min. Stronger shocks also increased startle, but with a more delayed onset of facilitation (8–20 min). Footshocks increased startle in rats not previously given startle-eliciting stimuli, indicating sensitization rather than dishabituation. The facilitatory effect may not be attributable to a rapid conditioning to the experimental context, because a change in lighting conditions from shock presentation to testing did not attenuate shock sensitization. This excitatory effect of shock on startle may represent the unconditioned effect of shock that can become associated with a neutral stimulus to support classical fear conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
30.
Goldman Susan R.; Mertz Davis L.; Pellegrino James W. 《Canadian Metallurgical Quarterly》1989,81(4):481
Practice on addition basic facts and changes in solution strategies were examined in 3rd- and 4th-grade students, practicing over 3 months. Response latencies decreased, indicating positive practice effects. Each of 3 student groups demonstrated different solution–strategy mixtures. Different mixtures led to different practice effects, indexed by shifts to more efficient counting strategies and more direct retrieval. Expectations about effects of practice and instructional strategies for optimizing practice must be sensitive to a child's actual strategy pattern. Most students had decreasing latency practice functions. However, quantitative functions fit to the practice session data indicated a high proportion of cases where the latency pattern over sessions was nonmonotonic. Trends over a small number of practice sessions may be inadequate for decisions about the utility of further practice, because such data may poorly represent long-term, cumulative effects on modifying strategy usage. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献