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   1212篇
  免费   2篇
  国内免费   1篇
化学工业   78篇
机械仪表   1篇
建筑科学   11篇
矿业工程   5篇
轻工业   2篇
石油天然气   1篇
无线电   24篇
一般工业技术   12篇
冶金工业   1074篇
自动化技术   7篇
  2023年   2篇
  2020年   2篇
  2018年   2篇
  2017年   2篇
  2016年   2篇
  2013年   8篇
  2012年   3篇
  2011年   4篇
  2010年   3篇
  2008年   1篇
  2006年   5篇
  2005年   5篇
  2004年   1篇
  2003年   4篇
  2002年   1篇
  2001年   4篇
  2000年   4篇
  1999年   35篇
  1998年   350篇
  1997年   187篇
  1996年   134篇
  1995年   61篇
  1994年   50篇
  1993年   72篇
  1992年   13篇
  1991年   13篇
  1990年   20篇
  1989年   15篇
  1988年   23篇
  1987年   11篇
  1986年   10篇
  1985年   11篇
  1984年   3篇
  1983年   4篇
  1982年   8篇
  1981年   3篇
  1980年   13篇
  1979年   4篇
  1978年   4篇
  1977年   30篇
  1976年   73篇
  1974年   2篇
  1971年   1篇
  1967年   3篇
  1966年   2篇
  1965年   3篇
  1964年   1篇
  1963年   1篇
  1955年   2篇
排序方式: 共有1215条查询结果,搜索用时 15 毫秒
111.
The most common tumoral lesion of the bony orbital region is osteoma. It is an infrequent and benign tumor, and generally attacks the craniofacial skeleton, but intraorbital involvement is extremely rare. After necessary radiologic examinations (radiographs and computed tomography scanning), surgery should be planned according to the tumor's localization. In the case presented here, osteoma originated mainly from the medial orbital wall. Therefore, for better surgical exposure, extra- and intracranial approaches were planned and carried out. The mass was removed successfully. At the 3-year follow-up, no recurrence was shown.  相似文献   
112.
Girth measurements provide a simple method for estimation of total body fat that can be used over a wide range of percentage body fat (%BF). Well-established equations for determining %BF from girth measurements were applied to 42 Caucasian and 40 Polynesian women. %BF was determined from total body water measurement using oxygen-18 dilution. The relationship between the criterion measurement of %BF and that calculated from girth measurements differed significantly between the two ethnic groups. Assessment of body fat using girth measurements should use ethnicity-specific equations.  相似文献   
113.
114.
Staphylococcus epidermidis colonises a wide range of implanted prosthetic devices, but rarely contact lenses -- despite a similarity in material composition. A conceivable explanation for this anomaly is the action of the tear defences, including the constitutive proteins lactoferrin and lysozyme. Therefore this study investigated the effect of lactoferrin, lysozyme and serum on the growth of S. epidermidis isolates in artificial tear fluid. Whether supplemented with serum alone or serum with either apolactoferrin or lysozyme, this medium induced a similar, strain-variable effect. However, simultaneous addition of these proteins induced a greater bactericidal or bacteristatic effect. Of those strains killed by the concerted action of apolactoferrin and lysozyme, the absence of serum led to a further increase in the bactericidal effect, whereas strains displaying bacteriostasis were unaffected by serum. Iron saturation of lactoferrin reversed the antimicrobial synergy of apolactoferrin and lysozyme. These results show synergy between lactoferrin and lysozyme which is dependent on the iron limitation of lactoferrin. As a bactericidal mechanism, this synergy is augmented by serum, but bacteriostasis remains unaffected by serum supplemention. Thus, the combination of lysozyme and lactoferrin may partly explain the low level of contact lens colonisation by S. epidermidis in vivo.  相似文献   
115.
Suitable measures of health and morbidity are less readily available for children than they are for adults. We present a measure, which is used to describe the impact of impairment and disability on the lives of children with cerebral palsy and their families. The development of this measure involved data collected from 691 children with cerebral palsy contained within the North-East England Cerebral Palsy Register and born between 1960 and 1985. Uniquely, multidimensional scaling techniques were used to derive dimensions analogous with those described in the International Classification of Impairments, Disabilities, and Handicaps. We present the analyses undertaken to test the properties of the tool, which show that it is a reliable and valid measure of the disadvantages experienced by children with cerebral palsy.  相似文献   
116.
We cloned the MLSB resistance determinant by PCR from a clinical isolate of Enterococcus faecalis 373, which is induced more strongly by a 16-membered-ring macrolide, tylosin, than by erythromycin. To elucidate the molecular basis of resistance of E. faecalis 373, we analyzed the cloned gene, designated ermAMR, by site-directed mutagenesis and reporter gene assay. Our results showed that an arginine-to-cysteine change in the seventh codon of the putative leader peptide endowed tylosin with resistance inducibility and that TAAA duplication enabled the control region to express the downstream methylase gene at a drastically increased level.  相似文献   
117.
Spectrin is a widely expressed protein with specific isoforms found in erythroid and nonerythroid cells. Spectrin contains an Src homology 3 (SH3) domain of unknown function. A cDNA encoding a candidate spectrin SH3 domain-binding protein was identified by interaction screening of a human brain expression library using the human erythroid spectrin (alphaI) SH3 domain as a bait. Five isoforms of the alphaI SH3 domain-binding protein mRNA were identified in human brain. Mapping of SH3 binding regions revealed the presence of two alphaI SH3 domain binding regions and one Abl-SH3 domain binding region. The gene encoding the candidate spectrin SH3 domain-binding protein has been located to human chromosome 10p11.2 --> p12. The gene belongs to a recently identified family of tyrosine kinase-binding proteins, and one of its isoforms is identical to e3B1, an eps8-binding protein (Biesova, Z., Piccoli, C., and Wong, W. T. (1997)Oncogene 14, 233-241). Overexpression of the green fluorescent protein fusion of the SH3 domain-binding protein in NIH3T3 cells resulted in cytoplasmic punctate fluorescence characteristic of the reticulovesicular system. This fluorescence pattern was similar to that obtained with the anti-human erythroid spectrin alphaI SigmaI/betaI SigmaI antibody in untransfected NIH3T3 cells; in addition, the anti-alphaI SigmaI/betaI SigmaI antibody also stained Golgi apparatus. Immunofluorescence obtained using antibodies against alphaI SigmaI/++betaI SigmaI spectrin and Abl tyrosine kinase but not against alphaII/betaII spectrin colocalized with the overexpressed green fluorescent protein-SH3-binding protein. Based on the conservation of the spectrin SH3 binding site within members of this protein family and published interactions, a general mechanism of interactions of tyrosine kinases with the spectrin-based membrane skeleton is proposed.  相似文献   
118.
The carboxy-terminal domain (CTD) of RNA polymerase II consists of multiple repeats of the unique heptad sequence -(Ser-Pro-Thr-Ser-Pro-Ser-Tyr)- which may interact with DNA through the intercalation of adjacent tyrosine aromatic rings. We have examined details of the interaction of this motif with calf thymus DNA through analysis of peptide analogues that contain (1) an amino-terminal tyrosine which mimics the presence of an adjacent heptad repeat and (2) positively-charged lysine residues which facilitate the initial contact between peptide and DNA. Results of fluorescence experiments, NMR titrations, and viscometric analyses indicate that these peptides bind to the DNA helix through a non-classical intercalation mode involving partial aromatic stacking of the tyrosine rings with the Watson-Crick base pairs.  相似文献   
119.
A study was made of the prevalence of voice disorders and their risk factors in teaching professionals of Logro?o, Spain. A prevalence and case-control study was made, including interviews, ENT examination, videostrobolaryngoscopy, perceptual evaluation of hoarseness, basic aerodynamic tests, the physical range of phonation, and a physical analysis of the acoustic signal. The prevalence of voice disorders among Logro?o teachers was 17.7% (confidence interval: 12.1-25%). Nodular lesions (8.1%) were the most frequent pathology, followed by hyperfunctional dysphonia (4.1%), chronic laryngitis (2.7%), polyps (1.4%), hypofunctional dysphonia (0.7%), and submucous suffusion (0.7%). Voice disorders were more prevalent in women (19.3%) than in men (15.6%), and among teachers of the lowest grades: 36.4% in nursery schools, 25% in elementary school, and 20.8% in junior school. The width and depth of classrooms, larger number of students, longer classroom hours, and noise level were related with the frequency of voice disorders.  相似文献   
120.
Working memory performance is influenced by dopamine activation of D1 family dopamine receptors in the prefrontal cortex; working memory performance is maximal at moderate stimulation of D1 family receptors and is reduced by either higher or lower levels of D1 stimulation. The neuronal mechanisms that underlie this complex relationship are not yet understood. Previous work from this laboratory has demonstrated that the D1 family receptors, D1 and D5, are located in different compartments of pyramidal cells. Here we use an antibody specific to the D1 receptor and double-label immunohistochemistry at the light and electron microscopic level to demonstrate that D1-like immunoreactivity (D1-LIR) is also present in interneurons. D1 receptor is prevalent in parvalbumin-containing interneurons and is less common in calretinin-containing interneurons. At the ultrastructural level, D1-LIR is found associated with the Golgi apparatus and endoplasmic reticulum in the soma, with the membranes of vesicles in proximal dendrites, and with the plasma membrane on distal dendrites, where it is often located near asymmetric synapses. In addition, D1-LIR is also seen in presynaptic axon terminals, which give rise to symmetric synapses onto dendritic shafts and soma. These results raise the possibility that the circuit basis of working memory in the prefrontal cortex involves a D1-mediated inhibitory component.  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