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   985篇
  免费   19篇
  国内免费   2篇
电工技术   43篇
综合类   1篇
化学工业   213篇
金属工艺   28篇
机械仪表   17篇
建筑科学   11篇
能源动力   22篇
轻工业   148篇
水利工程   2篇
无线电   49篇
一般工业技术   179篇
冶金工业   172篇
原子能技术   14篇
自动化技术   107篇
  2023年   5篇
  2022年   13篇
  2021年   29篇
  2020年   18篇
  2019年   12篇
  2018年   6篇
  2017年   14篇
  2016年   13篇
  2015年   9篇
  2014年   24篇
  2013年   39篇
  2012年   29篇
  2011年   52篇
  2010年   44篇
  2009年   44篇
  2008年   42篇
  2007年   37篇
  2006年   39篇
  2005年   32篇
  2004年   30篇
  2003年   31篇
  2002年   31篇
  2001年   18篇
  2000年   14篇
  1999年   29篇
  1998年   72篇
  1997年   38篇
  1996年   34篇
  1995年   19篇
  1994年   23篇
  1993年   23篇
  1992年   6篇
  1991年   11篇
  1990年   11篇
  1989年   9篇
  1988年   8篇
  1987年   8篇
  1986年   12篇
  1985年   3篇
  1984年   5篇
  1983年   6篇
  1982年   8篇
  1981年   5篇
  1980年   9篇
  1979年   12篇
  1978年   8篇
  1977年   6篇
  1976年   8篇
  1965年   1篇
  1963年   1篇
排序方式: 共有1006条查询结果,搜索用时 15 毫秒
61.
Dynamic characteristics of fully depleted ultra-thin film CMOS/SIMOX devices in the range from 50 to 300 K are presented. Discussion is focused on the propagation delay time of CMOS/SIMOX ring oscillators. Using a simple theory, it is shown that the measure propagation delay time is larger than the predicted delay time. Adopting a simple theoretical assumption, it is strongly suggested that the propagation delay time is governed ultimately by the charging and discharging time of the inversion layer in off-to-on and on-to-off processes. The results are corroborated by the fact that fully depleted CMOS/SIMOX operate with extremely small parasitic capacitances  相似文献   
62.
The usefulness of INR as an index for assessing anticoagulation was studied using 85 outpatients, all suffering cardiovascular diseases and receiving warfain as subjects. The thrombotest, prothrombin time and INR were measured at follow-up, monthly intervals. The correlation between the thrombotest value and the INR value were assessed retrospectively. We found a stronged correlation between them. The 10 approximately 25% range of the thrombotest value, the therapeutic range, corresponded to 2.29 approximately 3.60 of the INR value. The INR value was more accurate than the thrombotest valve in the situation of prolonged coagulation time. It is recommended to use INR as an objective index for the anticoagulation due to increase accuracy and objectivity when comparing the data among the various institutions.  相似文献   
63.
Inflammatory cells accumulate within the lungs of cigarette smokers. Current concepts suggest that these cells can induce protease-antiprotease and/or oxidant-antioxidant imbalance(s), which may damage the normal lung alveolar and interstitial structures. Because type II pneumocytes line the alveolar space, and because the inflammatory cells migrate and reside at the alveolus, we postulated that the type II pneumocytes might release chemotactic activity for neutrophils and monocytes in response to smoke extract. To test this hypothesis, A549 cells were cultured and the supernatant fluids were evaluated for the neutrophil and monocyte chemotactic activity (NCA and MCA) by a blind-well chamber technique. A549 cells released NCA and MCA in response to smoke extract in a dose- and time-dependent manner (P < 0.05). Checkerboard analysis showed that the activity was chemotactic. Partial characterization of NCA and MCA revealed that the activity was partly heat labile, trypsin sensitive, and ethyl acetate extractable. Lipoxygenase inhibitors and cycloheximide inhibited the release of NCA and MCA. Molecular sieve column chromatography showed multiple peaks for both NCA and MCA. NCA was inhibited by anti-human-interleukin (IL)-8 antibody, granulocyte colony-stimulating factor (G-CSF) antibody, or leukotriene (LT)B4 receptor antagonist. Monocyte chemoattractant protein (MCP)-1 antibody or LTB4 receptor antagonist inhibited MCA. Immunoreactive IL-8, G-CSF, MCP-1, and LTB4 significantly increased in the supernatant fluids in response to smoke extract. These data suggest that the type II pneumocytes may release NCA and MCA and modulate the inflammatory cell recruitment into the lung.  相似文献   
64.
Implications of cultural accommodation–hybridization were explored within the framework of individualism–collectivism. Individualism highlights the personal and centralizes individuals as the unit of analyses, whereas collectivism highlights the social and contextualizes individuals as parts of connected social units. In 2 experiments, the ways in which individualism, collectivism, and identity salience influence social obligation to diverse others was explored. The authors varied the personal goal interrupted (achievement–pleasure), the target (individual–group), and focus (in-group–larger society) of social obligation within subjects. The authors hypothesized that collectivism would increase obligation to the in-group when identity was made salient; that individualism alone would dampen social obligation; and that cultural accommodation–hybridization (being high in both individualism and collectivism) would increase obligation to larger society. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
65.
Neoplastic lesions of the kidneys in untreated Long-Evans Cinnamon (LEC) rats of 57-118 weeks old (85 males and 34 females) and male F344 rats of 64-93 weeks old (59 males) were examined histologically. The incidences of renal cell tumors in male and female LEC rats were 6/80 (8%) in weeks 57-65, 3/19 (16%) in weeks 66-75, 3/8 (38%) in weeks 76-105 and 7/12 (58%) in weeks 106-118. Of these tumors, 13 were microscopic adenomas and 7 were renal cell carcinomas. The copper content of the kidneys was about three times higher in LEC rats than in F344 rats (P < 0.001), but the iron content of the kidneys was similar in the two strains.  相似文献   
66.
The relationship between ductility and material parameters such as grain-boundary (GB) precipitate size and dimple size in an Al-6.0% Zn-2.6% Mg alloy has been studied. Under the condition of a given GB precipitate size, the ductility increases with decreasing number of GB precipitates and dimples per unit area. The critical GB precipitate sizes acting as the nuclei for void formation are deduced.  相似文献   
67.
We have demonstrated the utility of normalization for efficient cDNA microarray preparation using Arabidopsis as a model. Nonredundant cDNAs including 5722 species were efficiently collected from random 7914 expressed sequence tags (ESTs) in four normalized cDNA libraries. The prepared microarrays were successfully used to monitor gene expression. These methodologies should be applicable to the study of other species in plant biotechnology.  相似文献   
68.
Standardization of transmission system for television satellite broadcasting with multiple sound and/or data signals for an operational broadcasting satellite system is under study in Japan. Based upon result obtained from the BSE experiment, several transmission systems have been developed at the NHK (Japan Broadcasting Corporation).  相似文献   
69.
In situ dynamic observations of the deformation and fracture characteristics of alpha/beta brass two-phase bicrystals were made by the solid diffusion method. The results indicated clearly that the crack initiation site was at the interface. The crack propagation direction, in both the alpha and beta phases, was found to be orientation dependent. Complementary experiments on alpha and beta brass single crystals confirmed the theories and results obtained previously on ductile single crystals.On leave from the Mechanical Engineering Department, Al-Azhar University, Cairo, Egypt.  相似文献   
70.
A simple and rapid determination of anticoccidial drug residues, diclazuril (DCZ) and nicarbazin (NCZ), in chicken tissues has been developed. DCZ and NCZ were extracted with acetonitrile from chicken liver, muscle, and fat. The extract was rinsed with n-hexane saturated with acetonitrile and then evaporated. The residue was dissolved in 1.4 mL of acetonitrile-methanol (1:1), then 1.0 mL of n-hexane saturated with acetonitrile-methanol (1:1) was added, and the mixture was partitioned by the addition of 0.6 mL of water. DCZ and NCZ in the aqueous layers were determined by HPLC on an Xterra RP-18 column with acetonitrile-0.5% ammonium acetate containing 0.01 mol/L tetra-n-butylammonium hydrogen sulfate (43:57) as the mobile phase. The mean recoveries (n = 5) of DCZ and NCZ spiked in chicken tissues at the maximum residue levels were 92.0-95.6% (CV 2.4-3.0%) and 87.3-89.4% (CV 1.7-2.8%), respectively. The detection limits of DCZ and NCZ were 0.01 and 0.004 microgram/g, respectively.  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