首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   691篇
  免费   5篇
化学工业   8篇
金属工艺   3篇
建筑科学   3篇
矿业工程   16篇
能源动力   1篇
轻工业   18篇
无线电   5篇
一般工业技术   13篇
冶金工业   607篇
原子能技术   3篇
自动化技术   19篇
  2022年   1篇
  2020年   1篇
  2018年   1篇
  2017年   1篇
  2016年   3篇
  2015年   1篇
  2014年   1篇
  2013年   19篇
  2012年   5篇
  2011年   2篇
  2009年   2篇
  2008年   2篇
  2007年   1篇
  2006年   6篇
  2005年   2篇
  2004年   1篇
  2003年   2篇
  2002年   1篇
  2001年   1篇
  1999年   15篇
  1998年   146篇
  1997年   90篇
  1996年   87篇
  1995年   48篇
  1994年   45篇
  1993年   27篇
  1992年   3篇
  1991年   4篇
  1990年   12篇
  1989年   17篇
  1988年   6篇
  1987年   11篇
  1986年   5篇
  1985年   7篇
  1983年   3篇
  1982年   6篇
  1981年   11篇
  1980年   8篇
  1979年   2篇
  1978年   4篇
  1977年   30篇
  1976年   51篇
  1975年   2篇
  1973年   1篇
  1966年   1篇
  1955年   1篇
排序方式: 共有696条查询结果,搜索用时 15 毫秒
11.
A simplex algorithm used to solve molecular structure from asymptotic momentum values is reported. The geometry of CO23+ molecular ions in linear and bent configurations is reconstructed. A polyatomic molecular ion with trigonal planar symmetry is used to demonstrate the scalability of the algorithm.  相似文献   
12.
The authors studied separate parameters of the reaction of morphological dissociation of clotted blood in 97 patients, 83 of them suffering chronic nonspecific pneumonia and 14--lung cancer. Such RMDCB tests as the amount of the third fraction of blood coagulation (TFCB), the time of TFCB sediment formation and "the prognostic index" are found to be of certain diagnostic value, and along with other laboratory tests and clinical symptoms these allowed a differentiation between chronic nonspecific pneumonia and lung cancer.  相似文献   
13.
This paper describes an empirical study that addresses the issue of communication among members of a software development organization. In particular, data was collected concerning code inspections in one software development project. The question of interest is whether or not organizational structure (the network of relationships between developers) has an effect on the amount of effort expended on communication between developers. The independent variables in this study are various attributes of the organizational structure in which the inspection participants work. The dependent variables are measures of the communication effort expended in various parts of the code inspection process, focusing on the inspection meeting. Both quantitative and qualitative methods were used, including participant observation, structured interviews, generation of hypotheses from field notes, statistical tests of relationships, and interpretation of results with qualitative anecdotes. The study results show that past and present working relationships between inspection participants affect the amount of meeting time spent in different types of discussion, thus affecting the overall inspection meeting length. Reporting relationships and physical proximity also have an effect. The contribution of the study is a set of well-supported hypotheses for further investigation  相似文献   
14.
tau is a major component of paired helical filaments found in the neurofibrillary tangles of Alzheimer's diseased brain. However, the mechanism or mechanisms responsible for the association of tau to form these aggregates remains unknown. In this study, the role of intermolecular disulfide bonds in the formation of higher order oligomers of bovine tau and the human recombinant tau isoform T3 was examined using the chemical cross-linking agent disuccinimidylsuberate (DSS). In addition, the role of phosphorylation and oxidation state on the in vitro self-association of tau was studied using this experimental model. Stabilization of tau-tau interactions with DSS indicated that intermolecular disulfide bonds probably play a predominant role in dimer formation, but the formation of higher order oligomers of tau cannot be attributed to these bonds alone. tau-tau interactions were significantly decreased either by blocking Cys residues or by exposing the tau to a reducing (nitrogen and dithiothreitol), instead of an oxidizing, environment. tau self-association was also significantly decreased by prior phosphorylation with calcium/calmodulin-dependent protein kinase II. Phosphorylation by cyclic AMP-dependent protein kinase or dephosphorylation by alkaline phosphatase did not alter tau self-assembly. These data suggest a role for several factors that may modulate tau self-association in vivo.  相似文献   
15.
The literature on total quality management or continuous quality improvement in the behavioral health care field is just beginning to emerge. Although most of the evidence on its effectiveness remains anecdotal, it seems clear that it can work in behavioral health care organizations with strong leadership support and a long-term commitment.  相似文献   
16.
In this study, dissolved Kr and SF6 gases were used to determine various hydrogeological parameters of laboratory columns under water-saturated and partially saturated conditions as a function of the flow velocity. The dissolved gases behaved conservatively in saturated columns but were significantly retarded in unsaturated conditions as a direct function of the Henry's law constant (KH) and the ratio of column pore spaces filled with air and water (Vg/Vw). Lower aqueous diffusion coefficients for SF6 compared to that for Kr also resulted in significant rate-limited mass transport across gas-water interface. This effect was exacerbated at higher flow velocities as was indicated by the asymmetric shape of breakthrough curves, more so in the case of SF6. A nonequilibrium advective-dispersive transport model accurately described tracer breakthrough and was used to estimate parameters such as final Vg/Vw under partially saturated conditions and partitioning rates. Internally consistent model results were obtained for both dissolved gases despite the wide range in physical properties (e.g., KH and aqueous diffusion coefficients), suggesting that dissolved Kr and SF6 may be used in conjunction to delineate and validate aquifer characteristics simultaneously from a single pulse injection of the tracer.  相似文献   
17.
As psychomotor stimulants, both amphetamine and cocaine elicit episodes of repetitive motor activation (focused stereotypy) known to involve the mesostriatal dopamine system. During amphetamine-induced focused stereotypy, motor-related neurons in the striatum respond with either an excitation or inhibition, depending on dose and behavioral pattern, whereas nonmotor-related units are inhibited. To assess striatal activity during the focused stereotypy induced by cocaine, both types of striatal units were recorded in ambulant rats. Either 20 or 40 mg/kg cocaine caused highly focused sniffing and head bobbing, which occurred in conjunction with activation of both motor- and nonmotor-related neurons. The activation of motor-related units was evident even when firing rate was compared during periods of matched pre- and post-drug behavior, arguing against movement as the sole basis for the drug-induced neuronal excitation. Subsequent administration of haloperidol (1.0 mg/kg) reversed but did not completely block the neuronal activation, while the behavioral response shifted away from focused stereotypy toward an increase in ambulation. Thus, the level of activation of both motor- and nonmotor-related striatal neurons may play a critical role in the behavioral response pattern induced by cocaine.  相似文献   
18.
Zinc has an important place amongst inhibitors of crystallisation and crystal growth. These views are supported by in vivo and in vitro studies which suggest that the urinary zinc level is a significant factor in urolithiasis. Some recent studies have given contradictory results. Blood serum and urinary zinc levels were measured in 30 normal healthy controls and 42 stone forming patients (renal, ureteric and vesical). Statistically significant levels were found in all groups, varying according to the number of calculi. Increased urinary zinc levels and decreased serum zinc levels appear to be secondary to the process of stone formation. The role of zinc as an inhibitor of urolithiasis is questionable.  相似文献   
19.
Computed tomography (CT) was performed in 189 individuals: in 44 children of schizophrenic parents (high risk group, HRG), in 39 parents with schizophrenia or with schizophrenic disturbance, in 56 children with schizophrenia, in 50 children with consequences of early organic damages of central nervous system (mental retardation syndrome and generalized tic syndrome). The frequency of CT changes was equal in the mentioned groups but their character was quite different. The widening of brain's liquor system (89.7%), the signs of frontal and temporal atrophia (31%), foci of decreased density of cerebral brain's matter, closer in subcortical ganglia and periventricular zone, and different anomalies of brain were observed in HRG children.  相似文献   
20.
The changes of bioelectric activity of the brain hemispheres were studied under the influence of an alternating magnetic field (AMF), directed on the hand of 20 epileptic patients and 18 healthy normals. Under AMF influence there was intensification of epileptic activity--elevation of the focal bioelectric characteristics and of the processes of generalization. It permitted to apply AMF for diagnosis of epileptic focus. Under AMF influence more stable changes in posterio-parietal areas of the right hemisphere occur. The authors came to the conclusion that AMF effects were mainly realized with participation of right hemisphere.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号