全文获取类型
收费全文 | 986篇 |
免费 | 2篇 |
专业分类
电工技术 | 1篇 |
综合类 | 1篇 |
化学工业 | 40篇 |
金属工艺 | 6篇 |
机械仪表 | 4篇 |
建筑科学 | 12篇 |
能源动力 | 3篇 |
轻工业 | 17篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 11篇 |
一般工业技术 | 43篇 |
冶金工业 | 821篇 |
原子能技术 | 2篇 |
自动化技术 | 22篇 |
出版年
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 10篇 |
2008年 | 11篇 |
2007年 | 2篇 |
2006年 | 7篇 |
2005年 | 10篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 15篇 |
1998年 | 212篇 |
1997年 | 118篇 |
1996年 | 91篇 |
1995年 | 38篇 |
1994年 | 57篇 |
1993年 | 56篇 |
1992年 | 14篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1986年 | 17篇 |
1985年 | 12篇 |
1984年 | 3篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 32篇 |
1976年 | 55篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1966年 | 3篇 |
1955年 | 2篇 |
1929年 | 2篇 |
排序方式: 共有988条查询结果,搜索用时 15 毫秒
61.
A random sample (N = 197) of supported employees with mental retardation was examined in a longitudinal study. Results indicate that intelligence, prior earnings, and federal job subsidy predicted future earnings. Statistical controls applied to the stratified sample show that job placement, job type, subsidy, and means of transportation had little influence on earnings. 相似文献
62.
Spatiotemporal patterns of secretomotor neuron generation in the parvicellular neuroendocrine system
Spatiotemporal patterns of parvicellular neurosecretory neuron generation (birthdates) were determined in the young adult male rat using a triple fluorescence labeling method. The six classic phenotypes were identified in histological sections with rabbit antisera to neurotransmitters (or related enzymes), nuclear bromodeoxyuridine was detected with a mouse monoclonal antibody, and an axonal projection to the median eminence was determined with the fluorescent retrograde tracer fast blue. The vast majority of triply labeled neurons are generated between embryonic days 12-14, during the time when magnocellular neurosecretory neurons are also generated. This pattern of neurogenesis is distinct from the well-known 'outside-in' pattern of hypothalamic neurogenesis, where the peak of lateral zone birthdates occurs on embryonic days 12 and 13, the peak of medial zone birthdates occurs on embryonic days 14 and 15, and the peak of periventricular zone birthdates occurs on embryonic days 16 and 17. Thus, neuroendocrine motoneurons may constitute 'pioneer neurons' for the various anatomically distinct regions of the periventricular zone. In addition, many intermixed neurons that express the same neurotransmitters as parvicellular neurosecretory neurons but do not send an axon to the median eminence, also appear to be generated between embryonic days 12 and 14. What these results imply about mechanisms underlying neuroendocrine motor zone differentiation is discussed. 相似文献
63.
This article reviews the prerequisites for quantitative models of animal learning and cognition, describes the types of models, provides a rationale for the development of such quantitative models, describes criteria for their evaluation, and makes recommendations for the next generation of quantitative models. A modular approach to the development of models is described in which a procedure is considered as a generator of stimuli and a model is considered as a generator of responses. The goal is to develop models that, in combination with many different procedures, produce sequences of times of occurrence of events (stimuli and responses) that are indistinguishable from those produced by the animal under many experimental procedures and data analysis techniques. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
64.
Individual differences in the construct of managerial self-awareness (MSA)—operationalized as congruence between self and direct reports' behavioral ratings—were examined in 134 high-performing (HP) and 470 average-performing (AV) managers obtained from 4 independent datasets. Results based on several different approaches to measuring ratings agreement indicated that HPs were significantly more managerially self-aware compared with AVs. This relationship was consistent regardless of data source, organization, or method of assessing managerial performance. No overall relationships were found between congruence and level of item importance, gender, management level, age, or tenure. When compared with other measures for assessing self-focus, the construct of self-monitoring was found to be convergent with managerial self-awareness, whereas the construct of self-consciousness appeared to reflect primarily rating leniency effects. The article concludes with a comparison of the measurement approaches used, limitations, and suggestions for further study. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
65.
VC Culotta LW Klomp J Strain RL Casareno B Krems JD Gitlin 《Canadian Metallurgical Quarterly》1997,272(38):23469-23472
Copper is distributed to distinct localizations in the cell through diverse pathways. We demonstrate here that the delivery of copper to copper/zinc superoxide dismutase (SOD1) is mediated through a soluble factor identified as Saccharomyces cerevisiae LYS7 and human CCS (copper chaperone for SOD). This factor is specific for SOD1 and does not deliver copper to proteins in the mitochondria, nucleus, or secretory pathway. Yeast cells containing a lys7Delta null mutation have normal levels of SOD1 protein, but fail to incorporate copper into SOD1, which is therefore devoid of superoxide scavenging activity. LYS7 and CCS specifically restore the biosynthesis of holoSOD1 in vivo. Elucidation of the CCS copper delivery pathway may permit development of novel therapeutic approaches to human diseases that involve SOD1, including amyotrophic lateral sclerosis. 相似文献
66.
Two aspects of codependency were investigated among 442 undergraduates. First, parental antecedents were examined by subjects completing measures of codependency, perceived parental dysfunctions (compulsivity, chemical dependency, and codependency), and parental styles (coercion, control, and non-nurturance). As expected, correlations between adult codependency and parental coercion, control, non-nurturance, and maternal compulsivity were significant. However, correlations between codependency and parental chemical dependency were not significant. A multiple regression analysis identified parental codependency and maternal coercion as significant predictors of subject codependency. To examine the second aspect of codependency, which assumes that codependency was identified over 40 years ago by Karen Horney, subjects completed a loss of self measure which correlated highly with codependency. 相似文献
67.
1. The block by ifenprodil of voltage-activated Ca2+ channels was investigated in intracellular free calcium concentration ([Ca2+]i) evoked by 50 mM K+ (high-[K+]o) in Fura-2-loaded rat hippocampal pyramidal neurones in culture and on currents carried by Ba2+ ions (IBa) through Ca2+ channels in mouse cultured hippocampal neurones under whole-cell voltage-clamp. The effects of ifenprodil on voltage-activated Ca2+ channels were compared with its antagonist actions on N-methyl-D-aspartate- (NMDA) evoked responses in the same neuronal preparations. 2. Rises in [Ca2+]i evoked by transient exposure to high-[K+]o in our preparation of rat cultured hippocampal pyramidal neurones are mediated predominantly by Ca2+ flux through nifedipine-sensitive Ca2+ channels, with smaller contributions from nifedipine-resistant, omega-conotoxin GVIA-sensitive Ca2+ channels and Ca2+ channels sensitive to crude funnel-web spider venom (Church et al., 1994). Ifenprodil (0.1-200 microM) reversibly attenuated high-[K+]o-evoked rises in [Ca2+]i with an IC50 value of 17 +/- 3 microM, compared with an IC50 value of 0.7 +/- 0.1 microM for the reduction of rises in [Ca2+]i evoked by 20 microM NMDA. Tested in the presence of nifedipine 10 microM, ifenprodil (1-50 microM) produced a concentration-dependent reduction of the dihydropyridine-resistant high-[K+]o-evoked rise in [Ca2+]i with an IC50 value of 13 +/- 4 microM. The results suggest that ifenprodil blocks Ca2+ flux through multiple subtypes of high voltage-activated Ca2+ channels. 3. Application of the polyamine, spermine (0.25-5 mM), produced a concentration-dependent reduction of rises in [Ca2+]i evoked by high-[K+]o. The antagonist effects of ifenprodil 20 micro M on high-[K+]0-evoked rises in [Ca2+]. were attenuated by spermine 0.25 mM but not by putrescine 1 or 5 mM. In contrast,spermine 0.1 mM increased rises in [Ca2+]i evoked by NMDA and enhanced the ifenprodil (5 micro M) block of NMDA-evoked rises in [Ca2+]i.4. Similar results were obtained in mouse cultured hippocampal pyramidal neurones under whole-cell voltage-clamp. Ifenprodil attenuated both the peak and delayed whole-cell IB. with an IC% value of 18 +/- 2 micro M, whilst it attenuated steady-state NMDA-evoked currents with an IC50 of 0.8 +/- 0.2 micro M. Block of IBa by ifenprodil 10 JaM was rapid in onset, fully reversible and occurred without change in thecurrent-voltage characteristics of Ba. The ifenprodil block of IBa was enhanced on membrane depolarization and was weakly dependent on the frequency of current activation. Spermine 0.1 mM potentiated control NMDA-evoked currents but attenuated IB,. In agreement with the microspectrofluorimetric studies, co-application of spermine produced a small enhancement of the inhibitory effect of ifenprodil 10 micro M on NMDA-evoked responses whereas the reduction of I4 by ifenprodil 10 micro M in the presence of spermine was less than expected if the inhibitory effects of ifenprodil and spermine on IBa were simply additive.5. The results indicate that ifenprodil blocks high voltage-activated Ca2+ channels in rat and mouse cultured hippocampal pyramidal neurones. Although the Ca2+ channel blocking actions of ifenprodil are observed at higher concentrations than those associated with NMDA antagonist activity, Ca2+ channel blockade may contribute, at least in part, to the established neuroprotective and anticonvulsant properties of the compound. 相似文献
68.
O Mokady MH Dick D Lackschewitz B Schierwater LW Buss 《Canadian Metallurgical Quarterly》1998,95(7):3673-3678
We report the isolation of an empty spiracles class homeodomain-containing gene, Cn-ems, from the hydrozoan Hydractinia symbiolongicarpus, the first gene of this class characterized in a lower metazoan. Cn-ems was found to be expressed in the head of gastrozooids, specifically in endodermal epithelial cells of the taeniolae of the hypostome. Cn-ems is not expressed in gonozooids, which lack taeniolae. Experimental conversion of the posterior region of the planula larva into head structures up-regulates expression of the gene. These findings establish that the association of ems-class genes with head structures preceded the evolution of bilateral symmetry. 相似文献
69.
OBJECTIVE: To assess the prevalence, clinical manifestations, associated genital infections, and HLA associations of reactive arthritis (ReA) among patients attending an urban sexually transmitted diseases (STD) clinic. METHODS: Using a standardized questionnaire, 271 consecutive adults, primarily black, with possible or proven Chlamydia trachomatis genital infection were screened for symptoms of ReA. A followup questionnaire was administered 6 weeks later by mail. Patients who reported at least 1 symptom were evaluated by a rheumatologist. HLA-B typing was performed on patients with objective ReA features. RESULTS: Nine of 217 patients (4.1%) with genital infection/inflammation had objective ReA features. Chlamydial or nongonococcal STD syndromes were diagnosed in 8 of these 9 patients (88%). Genital infection/inflammation was asymptomatic in 78% of patients with ReA features. HLA-B27 or other B7-cross-reactive group antigens were not associated with the occurrence of ReA. CONCLUSION: Nongonococcal genital infections, often asymptomatic, can trigger a relatively mild ReA in a larger number of exposed patients than previously thought, irrespective of the individual's HLA status. 相似文献
70.