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   1030篇
  免费   30篇
  国内免费   1篇
电工技术   7篇
综合类   3篇
化学工业   342篇
金属工艺   14篇
机械仪表   11篇
建筑科学   58篇
矿业工程   2篇
能源动力   27篇
轻工业   219篇
水利工程   10篇
石油天然气   3篇
无线电   37篇
一般工业技术   151篇
冶金工业   83篇
原子能技术   4篇
自动化技术   90篇
  2024年   3篇
  2023年   8篇
  2022年   35篇
  2021年   55篇
  2020年   11篇
  2019年   18篇
  2018年   16篇
  2017年   18篇
  2016年   27篇
  2015年   22篇
  2014年   26篇
  2013年   94篇
  2012年   55篇
  2011年   64篇
  2010年   46篇
  2009年   38篇
  2008年   53篇
  2007年   49篇
  2006年   47篇
  2005年   43篇
  2004年   31篇
  2003年   28篇
  2002年   35篇
  2001年   6篇
  2000年   17篇
  1999年   13篇
  1998年   20篇
  1997年   13篇
  1996年   13篇
  1995年   13篇
  1994年   14篇
  1993年   15篇
  1992年   9篇
  1991年   8篇
  1990年   8篇
  1989年   4篇
  1988年   3篇
  1987年   4篇
  1986年   7篇
  1985年   4篇
  1983年   3篇
  1981年   4篇
  1980年   6篇
  1978年   6篇
  1977年   7篇
  1976年   3篇
  1975年   4篇
  1955年   3篇
  1942年   3篇
  1917年   3篇
排序方式: 共有1061条查询结果,搜索用时 15 毫秒
31.
32.
Targeting molecular alterations as an effective treatment for isocitrate dehydrogenase-wildtype glioblastoma (GBM) patients has not yet been established. Sterol-O-Acyl Transferase 1 (SOAT1), a key enzyme in the conversion of endoplasmic reticulum cholesterol to esters for storage in lipid droplets (LD), serves as a target for the orphan drug mitotane to treat adrenocortical carcinoma. Inhibition of SOAT1 also suppresses GBM growth. Here, we refined SOAT1-expression in GBM and IDH-mutant astrocytoma, CNS WHO grade 4 (HGA), and assessed the distribution of LD in these tumors. Twenty-seven GBM and three HGA specimens were evaluated by multiple GFAP, Iba1, IDH1 R132H, and SOAT1 immunofluorescence labeling as well as Oil Red O staining. To a small extent SOAT1 was expressed by tumor cells in both tumor entities. In contrast, strong expression was observed in glioma-associated macrophages. Triple immunofluorescence labeling revealed, for the first time, evidence for SOAT1 colocalization with Iba1 and IDH1 R132H, respectively. Furthermore, a notable difference in the amount of LD between GBM and HGA was observed. Therefore, SOAT1 suppression might be a therapeutic option to target GBM and HGA growth and invasiveness. In addition, the high expression in cells related to neuroinflammation could be beneficial for a concomitant suppression of protumoral microglia/macrophages.  相似文献   
33.
Bacteriological analysis of milk samples from quarters of a dairy cow suffering from subclinical mastitis yielded two isolates of Staphylococcus aureus which gave a negative reaction in the standard coagulase test. Both isolates were also clumping factor and thermonuclease negative, and gave a negative reaction in the Staphaurex? test. The isolates were identified by using commercial biochemical systems, and by PCR analysis of different staphylococcal cell surface protein and exoprotein genes. Further molecular identification of the isolates, which included sequencing of the 16S rRNA gene and RT-PCR of coagulase (coa), clumping-factor (clfA) and thermonuclease (nuc) genes, was consistent with the diagnosis phenotypically 'coagulase-negative variant of Staph. aureus'. The fact that coagulase-negative Staph. aureus variants can occur in the context of intramammary infections in cattle may result in the incorrect diagnosis 'coagulase-negative staphylococci (CNS)' in routine mastitis diagnostic, at least in rare cases. To fully ensure correct species diagnosis, sequencing of the 16S rRNA gene and amplification of specific genes such as coa is necessary in these cases.  相似文献   
34.
Entrapped air can commonly lead to large delaminations in thick walled sheet molding compound (SMC) products. In this work different sources of air entrapment in SMC are investigated. The critical process is shown to be the impregnation of the fibers. If no surface active additives are used, large volumes of air may be entrapped in this process, unless the viscosity of the compound is very low. In this situation of poor wetting, the viscosity of the compound during fiber impregnation will critically determine the interlaminar, tensile strength of the product. However, if surface active additives are used, the air escapes entrapment even at relatively high viscosities. The lowering of the viscosity, which is a side effect of the additives, has practically no importance under these conditions of good wetting. Large numbers of small air bubbles are also entrapped during the mixing of the components, but it is shown that these bubbles have very little effect on the mechanical properties of the finished part.  相似文献   
35.
Fetal alcohol syndrome (FAS) is the leading birth defect in the United States, yet few treatment options exist for children afflicted with this disorder. Although play therapy has demonstrated its efficacy with numerous special populations, as of today, no research has been conducted on its use with FAS. This article presents an overview of current data on FAS, an argument for the use of child-centered play therapy for children diagnosed FAS, and suggests areas of research needs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
36.
37.
Summary A new group of low-molecular weight channel-forming oligo(hydroxybutyric acids) (cPHBs, 1 with n = 8–30; main component MW ≈ 1300 dalton) was isolated from microorganisms of different origin. Inclusion bodies were electron-microscopically visible in cells in the state of autolysis, not in cells in the exponential phase of growth. cPHB and high-molecular poly(l3-hydroxybutyric acid) (sPHB) is cleaved by phenylethylamine and forms the corresponding monomeric hydroxybutyramide and – under drastic conditions, the crotylamide. One of these compounds, the 3-hydroxy-N-phenethyl-butyramide (5), was isolated as a new natural product now. Received: 28 March 2002/Revised version: 26 July 2002/ Accepted: 26 July 2002 RID="*" ID="*"Marine Bakterien, XVII. XVI: R.P. Maskey, R.N. Asolkar, E. Helmke, and H. Laatsch, Chalcomycin B, a new antibiotic from a marine Streptomyces sp. B7064. J. Antibiot., submitted 2002 Correspondence to Hartmut Laatsch, e-mail: hlaatsc@gwdg.de, Fax: +49-551-399660  相似文献   
38.
Integrins, a widely expressed family of heterodimeric cell surface adhesion proteins, are expressed in a variety of cell types. They play a decisive role in cell-cell adhesion or cell to extracellular matrix adhesion events. Antagonists of alpha(v)beta(3) or alpha(IIb)beta(3) integrin may have a potential use in suppression of pathological processes. We present the synthesis of novel tricyclic benzodiazepinedione-based RGD analogues, which were subsequently tested in a solid-phase receptor assay in order to investigate their binding affinities towards alpha(v)beta(3) and alpha(IIb)beta(3) integrin.  相似文献   
39.
The objective of the present study was to examine the role of the corpus callosum (CC) in dichotic listening. For this purpose, 40 right-handed healthy male participants were assessed with morphological and diffusion tensor imaging, which yielded macrostructural (midsagittal area) and microstructural (mean diffusion, fractional anisotropy) measures of the total CC and predefined subregions. Applying the standard consonant-vowel Bergen Dichotic Listening Test (including 3 different attentional instructions), the authors found dichotic listening performance to be substantially related to the integrity of the CC at both macro- and microstructural levels. Results indicate a dual role of the CC; it is relevant not only for the stimulus-driven (bottom-up) transfer of left-ear input to the left hemisphere but also for its attentional (top-down) modulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
40.
Natural language and databases are core components of information systems. They are related to each other because they share the same purpose: the conceptualization aspects of the real world in order to deal with them in some way. Natural language processing (NLP) techniques may substantially enhance most phases of the information system lifecycle, starting with requirements analysis, specification and validation, and going up to conflict resolution, result processing and presentation. Furthermore, natural language based query languages and user interfaces facilitate the access to information for anyone and allow for new paradigms in the usage of computerized services. This paper investigates the use of NLP techniques in the design phase of information systems. Then, it reports on data base querying and information retrieval enhanced with NLP.  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