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   1218篇
  免费   4篇
电工技术   9篇
化学工业   38篇
金属工艺   5篇
建筑科学   3篇
能源动力   2篇
轻工业   5篇
水利工程   5篇
石油天然气   9篇
无线电   7篇
一般工业技术   37篇
冶金工业   1023篇
原子能技术   1篇
自动化技术   78篇
  2016年   2篇
  2015年   4篇
  2014年   2篇
  2013年   10篇
  2012年   7篇
  2011年   9篇
  2010年   8篇
  2009年   10篇
  2008年   10篇
  2007年   9篇
  2006年   5篇
  2005年   9篇
  2004年   4篇
  2003年   10篇
  2002年   6篇
  2001年   3篇
  2000年   2篇
  1999年   40篇
  1998年   326篇
  1997年   197篇
  1996年   100篇
  1995年   73篇
  1994年   48篇
  1993年   70篇
  1992年   8篇
  1991年   20篇
  1990年   16篇
  1989年   13篇
  1988年   17篇
  1987年   10篇
  1986年   12篇
  1985年   12篇
  1984年   3篇
  1983年   4篇
  1982年   11篇
  1981年   9篇
  1980年   8篇
  1978年   11篇
  1977年   23篇
  1976年   49篇
  1975年   7篇
  1974年   8篇
  1973年   4篇
  1972年   1篇
  1971年   1篇
  1970年   2篇
  1969年   1篇
  1968年   1篇
  1967年   1篇
  1955年   1篇
排序方式: 共有1222条查询结果,搜索用时 51 毫秒
91.
92.
This paper argues that intermediation is both a valuable form of occupational self-organization for professional artists and a political act of embedding with socio-spatial ramifications at different local, urban, and global scales. A case study of events organized in Berlin by the interdisciplinary cultural centre Zentrum für Kunst und Urbanistik demonstrates how artists strategically practice intermediation as modes of autopoietic and dissipative self-organization and as an interscalar survival strategy. These artist intermediaries add improvisational flexibility to the state’s understanding of Verstetigung (sustainable anchoring that fosters a reliable relationship between urban policymakers and cultural producers) and challenge neoliberal urban development logics that instrumentalize creativity.  相似文献   
93.
Simultaneous interphase mass transfer and a zero–order reaction is described by the film model of mass transfer. The analysis leads to the conclusion that three regimes of the process need to be considered. At low rates of absorption the reaction goes to completion in the film, and at higher rates it goes to completion in the bulk and proceeds there at zero apparent concentration of the reactant. At still higher rates of absorption the reaction does not go to completion and the reactant is present also in the bulk in appreciable concentration. Design procedures based on the results obtained are discussed for a well–mixed CSTR and for a column with con–tinuous change.  相似文献   
94.
The Sleep Heart Health Study (SHHS) is a prospective cohort study designed to investigate obstructive sleep apnea (OSA) and other sleep-disordered breathing (SDB) as risk factors for the development of cardiovascular disease. The study is designed to enroll 6,600 adult participants aged 40 years and older who will undergo a home polysomnogram to assess the presence of OSA and other SDB. Participants in SHHS have been recruited from cohort studies in progress. Therefore, SHHS adds the assessment of OSA to the protocols of these studies and will use already collected data on the principal risk factors for cardiovascular disease as well as follow-up and outcome information pertaining to cardiovascular disease. Parent cohort studies and recruitment targets for these cohorts are the following: Atherosclerosis Risk in Communities Study (1,750 participants), Cardiovascular Health Study (1,350 participants), Framingham Heart Study (1,000 participants), Strong Heart Study (600 participants), New York Hypertension Cohorts (1,000 participants), and Tucson Epidemiologic Study of Airways Obstructive Diseases and the Health and Environment Study (900 participants). As part of the parent study follow-up procedures, participants will be surveyed at periodic intervals for the incidence and recurrence of cardiovascular disease events. The study provides sufficient statistical power for assessing OSA and other SDB as risk factors for major cardiovascular events, including myocardial infarction and stroke.  相似文献   
95.
In recent years, home visitation services have been widely promoted as a means of preventing health and developmental problems in children from vulnerable families. The U.S. Advisory Board of Child Abuse and Neglect, for example, recommended that home visitation services be made available to all parents of newborns to prevent child abuse and neglect.  相似文献   
96.
97.
98.
Escherichia coli leader peptidase, an integral membrane protein, is responsible for the cleavage of the signal sequence of many exported proteins. Recent studies suggest that it is a novel serine protease that utilizes a serine-lysine catalytic dyad. In an effort to further understand the mechanism of this enzyme, an internally quenched fluorescent peptide substrate incorporating the leader peptidase cleavage site of maltose binding protein signal peptide, Y(NO2)-F-S-A-S-A-L-A-K-I-K(Abz) (anthraniloyl), was designed and synthesized. In the intact peptide, the fluorescence of the anthraniloyl group is quenched by the 3-nitrotyrosine. This quenched fluorescence is liberated upon cleavage of the peptide by the leader peptidase, resulting in increased fluorescence that could then be monitored fluorometrically. The designed substrate can be cleaved effectively by E. coli leader peptidase as detected by both HPLC and fluorescent spectroscopy. Mass spectra of cleavage products demonstrated that the cleavage occurs at the predicted site (A-K). The cleavage of the peptide substrate has a linear dependence on the enzyme concentration (0.1 to 1.9 microM) and the kcat/K(m) was calculated to be 71.1 M-1 s-1. These data are comparable with the unmodified peptide substrate. This report represents the first direct continuous assay based on fluorescence resonance energy transfer for E. coli leader peptidase.  相似文献   
99.
A large number of substituted chalcones have been synthesized and tested for antileishmanial and lymphocyte-suppressing activities. A subset of the chalcones was designed by using statistical methods. 3D-QSAR analyses using 67 (antileishmanial activity) and 63 (lymphocyte-suppressing activity) of the compounds for the training sets and 9 compounds as an external validation set were performed by using the GRID/GOLPE methodology. The Smart Region Definition procedure with subsequent region selection as implemented in GOLPE reduced the number of variables to approximately 1300 yielding 3D-QSAR models of high quality (lymphocyte-suppressing model, R2 = 0. 90, Q2 = 0.80; antileishmanial model, R2 = 0.73, Q2 = 0.63). The coefficient plots indicate that steric interactions between the chalcones and the target are of major importance for the potencies of the compounds. A comparison of the coefficient plots for the antileishmanial effect and the lymphocyte-suppressing activity discloses significant differences which should make it possible to design chalcones having a high antileishmanial activity without suppressing the proliferation of lymphocytes.  相似文献   
100.
Antimicrobial therapy can be a confounding factor in the diagnosis of urinary tract infection and is not always reported to laboratories by physicians. We developed a microbiologic assay for screening urine specimens for antimicrobial agents. Bacillus stearothermophilus was used as the indicator bacteria. A total of 1,921 urine specimens from three hospitals in Taiwan were screened using this assay. Of the samples assayed, 1,293 were positive for antimicrobial agents. Agreement between information provided by physicians and laboratory findings was 68.5% (419/612). In the presence of antimicrobial agents in the urine samples, the isolation of yeasts and Pseudomonas aeruginosa increased dramatically, from 4.5 to 19.5% and 4.2 to 13.2%, respectively. Additionally, Escherichia coli was more resistant to gentamicin (75.3% vs 48.7%, p < 0.0001), norfloxacin (85.2% vs 64.6%, p = 0.0006) and co-trimoxazole (58.5% vs 35.5%, p = 0.0018). In view of the high rate of occurrence of antimicrobial agents in urine specimens and the lack of information provided by most physicians to laboratories, a screening method to detect the presence (or absence) of antimicrobials in urine specimens may be a useful tool particularly in areas such as Taiwan where antimicrobial agents are commonly abused.  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