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   648篇
  免费   13篇
电工技术   9篇
化学工业   31篇
金属工艺   4篇
机械仪表   9篇
建筑科学   6篇
能源动力   2篇
轻工业   87篇
石油天然气   2篇
无线电   27篇
一般工业技术   17篇
冶金工业   435篇
原子能技术   3篇
自动化技术   29篇
  2020年   3篇
  2018年   5篇
  2017年   3篇
  2016年   6篇
  2015年   3篇
  2014年   4篇
  2013年   11篇
  2012年   13篇
  2011年   8篇
  2010年   4篇
  2009年   8篇
  2008年   16篇
  2007年   20篇
  2006年   11篇
  2005年   5篇
  2004年   9篇
  2003年   13篇
  2002年   6篇
  2001年   6篇
  2000年   8篇
  1999年   9篇
  1998年   130篇
  1997年   70篇
  1996年   51篇
  1995年   34篇
  1994年   26篇
  1993年   29篇
  1992年   3篇
  1991年   4篇
  1990年   3篇
  1989年   5篇
  1988年   3篇
  1987年   5篇
  1986年   10篇
  1985年   7篇
  1983年   9篇
  1982年   14篇
  1981年   6篇
  1980年   7篇
  1978年   3篇
  1977年   23篇
  1976年   34篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1970年   1篇
  1969年   2篇
  1966年   4篇
  1961年   2篇
  1957年   1篇
排序方式: 共有661条查询结果,搜索用时 15 毫秒
1.
Papaya proteinase omega (pp omega) has been purified from dried latex both by immunoaffinity and traditional methods. Kinetic analysis revealed that (1), the pp omega-catalysed hydrolysis of N-benzoyl-L-arginine p-nitroanilide (BApNA) has a lower specificity (kcat/Km) than the same reaction catalysed by papain; (2), the pp omega-catalysed hydrolysis of a tripeptide substrate having phenylalanine at the second position (S2-site) showed a more similar specificity to that catalysed by papain; (3), the significant difference between the two enzymes is that steady state kinetics with both L-BApNA and a tripeptide enables the identification in pp omega of other ionizations affecting binding. The active sites of papain and pp omega can therefore be distinguished by pH-dependence of kcat/Km.  相似文献   
2.
A calorimeter of 25 bismuth germanate (BGO) crystals equipped with silicon photodiode readout has been tested at the CERN SPS in the energy range 1–50 GeV. The response for electrons has been shown to be linear in this energy range and the rms resolution obtained ( ) is approximately 1%, for E > 4 GeV. The electron/pion separation was found to be better than 1:500 in the energy range 1–20 GeV. Data on lateral and longitudinal shower development were compared with the results of a Monte Carlo simulation using the SLAC-EGS program and found to be in good agreement.  相似文献   
3.
Based on generalization and analysis of instructions and guidelines for therapeutical and prophylactic diets of workers, ways of its optimization were proposed, by using bifide-containing acid dairy products as a preventive agent against possible occupational diseases caused by occupational factors.  相似文献   
4.
A new indirect fluorescent-antibody (IFA) assay with antigen produced in vitro in the human promyelocytic leukemia cell line HL60 was used to identify the first recognized case of human granulocytic ehrlichiosis in Rhode Island. This IFA assay was used to detect granulocytic ehrlichiae in white-footed mice and in a dog inhabiting the area surrounding the patient's residence. Host-seeking Ixodes scapularis ticks found in the same habitat also were infected. I. scapularis ticks collected from other locations were fed on dogs and New Zealand White rabbits to assess the competency of these species as hosts of granulocytotropic Ehrlichia. Tick-induced infections of dogs were confirmed by serologic testing, tissue culture isolation, and PCR amplification, whereas several rabbits seroconverted but were PCR and culture negative. PCR amplification of the 16S rRNA gene and DNA sequencing of the PCR products or culture isolation was used to confirm granulocytic Ehrlichia infections in humans, dogs, white-footed mice, and ticks.  相似文献   
5.
This retrospective study examined the clinical course of 18 prepubertal boys (aged 6 to 12) who had dual diagnoses of attention deficit hyperactivity disorder and conduct disorder and who received clonidine on an inpatient basis after failed trials of conventional drug therapy, consisting predominantly of psychostimulants. The effects of clonidine were assessed during inpatient treatment and after discharge at intervals of 1 to 2 months. Eleven (61%) of the children had marked improvement as measured by clinical impression. Transient sedation lasting 2 to 3 days occurred after initial administration or dosage increase; otherwise, clonidine was well tolerated. Our findings suggest that clonidine may prove to be an alternative treatment of comorbid attention deficit hyperactivity disorder and conduct disorder.  相似文献   
6.
The paper presents the results of treating patients with chronic nonspecific diseases of the lung by the use of extracorporeal ultraviolet autoblood irradiation (EUVABI). The marked clinical effect recorded after an EUVABI course coincided with the normalization of an erythrocytic membrane morphoform, which suggests that the severity of allergic and inflammatory reactions was liquidated and blood viscosity was improved. EUVABI led to positive changes in the pattern of morphotypes in the crystallogram of plasma, except the patients who showed no clinical effect, which indicates that plasma crystallography can be used as a diagnostic test in predicting the results of EUVABI application.  相似文献   
7.
The development of control strategies for loiasis is of crucial importance in endemic areas and depends heavily on the accurate identification of occult-infected individuals. A polymerase chain reaction (PCR) and nested polymerase chain reaction (nested PCR) were developed and based on sequences of the repeat 3 region (15r3) of the gene encoding a Loa loa 15-kD protein. The assays was performed on 20 blood samples from occult-infected subjects and 30 from field-collected amicrofilaremic individuals. The size of the initial PCR product was 396 basepairs (bp). When this initial amplification using primers 15r3(1) and 15r3(2) was carried out for 30 cycles, the PCR products from three of the 20 occult-infected and five of the 30 amicrofilaremic individuals were visualized after electrophoresis by staining the gel with ethidium bromide. Subsequent Southern blotting and hybridization with the specific probe revealed hybridization in 19 of 20 occult-infected and 23 of 30 amicrofilaremic samples but only after two days of exposure of the blot to the x-ray film. When the nested PCR was carried out (product size = 366 bp, primers 15r3(3) and 15r3(4)), 19 of 20 occult-infected and 23 of 30 amicrofilaremic samples that were positive by Southern hybridization of the initial PCR products were strongly positive by staining with ethidium bromide. Qualitative Southern blotting of the nested PCR products using the same probe previously described confirmed the ethidium bromide staining results after a very short exposure time of 4 hr. These results demonstrate that the nested PCR amplification product is specific and that its sensitivity in detecting occult loiasis is 95%. This approach has significant promise for the screening of large human populations for active loiasis without the requirement for blotting and hybridization of the PCR products.  相似文献   
8.
过去10年中,原配轮胎的滚动阻力和抓着性能不断得到改善,以满足汽车公司越来越严格的要求。由于各种胎面用聚合物的不断发展,才能实现上述改善。  相似文献   
9.
This paper compares the experimental performance of three flux and speed observers for speed-sensorless induction motor drives and discusses the cause of their differences. The small signal analysis using the linearized model is carried out to analyze stability. Three methods are generally accepted to be representative candidates for high sensorless performance, namely: 1) rotor-flux model reference adaptive system (MRAS); 2) torque-current MRAS; and 3) adaptive nonlinear flux observer. Many other sensorless methods improved these methods. The paper discusses baseline conditions for the experiments and the stability analysis, which include matched load inertia, specified speed estimator dynamics, and sensorless operation within a speed control loop. For the comparison tests in the paper, the speed estimation dynamics of the methods are the same; this is important for parameter sensitivity. The paper concentrates on the low-speed performance, and all results shown are under sensorless speed control.  相似文献   
10.
A system is described for preparing and examining frozen-hydrated sections of mammalian tissue, using commercially available equipment. An essential part of the system is a liquid nitrogen cooled vacuum transfer system. Minor modifications were required to interface the various manufacturers' equipment, and also to facilitate handling of specimens in the cryoultramicrotome. A variety of criteria indicates that our sections are truly frozen-hydrated, but negligible image contrast in the sections is a serious problem both for morphological work and X-ray microanalysis.  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