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   2407篇
  免费   52篇
  国内免费   12篇
电工技术   83篇
综合类   5篇
化学工业   533篇
金属工艺   115篇
机械仪表   73篇
建筑科学   35篇
矿业工程   1篇
能源动力   69篇
轻工业   160篇
水利工程   3篇
石油天然气   1篇
无线电   236篇
一般工业技术   335篇
冶金工业   643篇
原子能技术   49篇
自动化技术   130篇
  2023年   8篇
  2022年   25篇
  2021年   38篇
  2020年   17篇
  2019年   14篇
  2018年   31篇
  2017年   15篇
  2016年   29篇
  2015年   28篇
  2014年   38篇
  2013年   90篇
  2012年   59篇
  2011年   99篇
  2010年   73篇
  2009年   88篇
  2008年   111篇
  2007年   96篇
  2006年   64篇
  2005年   76篇
  2004年   62篇
  2003年   68篇
  2002年   65篇
  2001年   65篇
  2000年   53篇
  1999年   61篇
  1998年   218篇
  1997年   165篇
  1996年   119篇
  1995年   72篇
  1994年   64篇
  1993年   66篇
  1992年   34篇
  1991年   25篇
  1990年   28篇
  1989年   19篇
  1988年   22篇
  1987年   21篇
  1986年   12篇
  1985年   19篇
  1984年   16篇
  1983年   11篇
  1982年   24篇
  1981年   18篇
  1980年   24篇
  1979年   24篇
  1978年   8篇
  1977年   19篇
  1976年   37篇
  1975年   11篇
  1966年   4篇
排序方式: 共有2471条查询结果,搜索用时 15 毫秒
871.
In order to assess the role of hydrogen transport in hydrogen embrittlement, one of the kinetic aspects of hydrogen embrittlement, the strain rate dependence, was analyzed in terms of hydrogen transport. The results have been analyzed in terms of a new model which takes into account atomic and macroscopic diffusion in describing dislocation-hydrogen interactions. It was found that the strong strain rate dependence of hydrogen embrittlement can be explained by a dynamic trapping effect, which is associated with an increase in the population of dislocations during deformation.  相似文献   
872.
We report a case who was clinically and histopathologically diagnosed as herpetiform pemphigus (HP) and associated with autoimmune hemolytic anemia (AIHA). However, immunofluorescence studies demonstrated concurrent anti-cell-surface and anti-basement-membrane-zone antibodies in the patient's serum. Immunochemical studies showed that the patient's serum reacted with both the pemphigus foliaceus antigen and the two bullous pemphigoid antigens. Subsequently, the patient developed AIHA. Both anemia and skin lesions were successfully treated with oral prednisolone. We believe that this is the first case with HP in association with AIHA. The presence of autoantibodies against multiple antigens suggests an abnormal immunologic tolerance in the antibody production system in this patient.  相似文献   
873.
This paper focuses on the application results of the dispersed autonomous voltage control system, which the authors have proposed, to a real distribution network. This system is effective for regulating the supply voltage of an entire HV line within an optimum range. In the system configuration, an SCC is installed together with an SC and/or ShR on the line. Individual SCCs autonomously control the operation of SCs and/or ShRs based on the voltage measured where the SCs and/or ShRs are located on the line. A field test on a real high‐voltage distribution network found that the proposed system could sustain a high fault tolerance ability and also be cost‐effective in regulating line voltage. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 27–36, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10252  相似文献   
874.
The validity of dual energy single-photon emission computed tomography (SPECT) with technetium-99m pyrophosphate (Tc-99m PPi) and thallium-201 for the diagnosis of right ventricular (RV) infarction, and the clinical features of RV infarction, were investigated in 190 patients with acute myocardial infarction. Diagnosis of RV infarction was performed by Tc-99m PPi accumulation in the RV myocardium on thallium-201 and Tc-99m PPi over-lay images at the dual SPECT with simultaneous imaging taken 2 to 9 days after the onset of myocardial infarction. Thirty RV infarctions were found among the 190 patients with left ventricular infarction (15.8%): 29 (97%) in association with the inferior and 1 (3%) with the lateral infarction. Tc-99m PPi accumulation was mostly observed in the posterior wall of the right ventricle. A total occlusion or a severe stenosis of the right coronary artery was demonstrated angiographically in 92% of the patients with RV infarction. The prevalence of RV infarctions was significantly lower in patients who achieved successful early reperfusion than in those who did not (26.7 vs 68.4%, respectively, p < 0.01). However, a successful early reperfusion therapy could not significantly decrease the rate of RV involvement in patients without significant collateral flow (p < 0.01). Thus, dual isotope SPECT with Tc-99m PPi and thallium-201 can be used as a reliable method for the diagnosis of RV infarction.  相似文献   
875.
876.
OBJECTIVES: To determine the risk factors for the development of thyroid diseases during interferon-alpha therapy, we analyzed the patients with chronic hepatitis C who were treated with interferon-alpha. METHODS: One hundred nine patients with chronic hepatitis C (77 men and 32 women, ages 20-72 yr) were treated with interferon-alpha (alpha, 48; alpha 2a, 38; alpha 2b, 23) for 14-40 wk. Thyroid function tests and seven autoantibodies were assessed at the beginning and end of interferon-alpha therapy, and every other month. A logistic multiple regression model was used in the statistical analysis of risk factors for development of thyroid diseases. RESULTS: Among the 106 patients with normal pretreatment thyroid function tests, nine patients (three men and six women, ages 33-62 yr) developed thyroid diseases. However, among three patients with abnormal thyroid function tests, exacerbation of thyroid disease was not observed during interferon-alpha therapy. Logistic multiple regression model revealed that positivity for microsome antibody was a significant risk factor for the development of thyroid disease (p < 0.0001, chi 2 = 20.18). Actually, compared to patients without microsome antibody at the beginning of therapy, the incidence of thyroid diseases in the patients with pretreatment microsome antibody was very high: 3.3% (3/99) versus 60% (6/10), respectively. Six patients developed hyperthyroidism and three patients developed hypothyroidism. The patients with hyperthyroidism had atypical clinical features. CONCLUSION: Our study revealed that positivity for microsome antibody at the beginning of interferon-alpha therapy is a risk factor for thyroid dysfunction.  相似文献   
877.
We investigated the relationship between the Trp64Arg mutation in the beta 3-adrenergic receptor gene and insulin sensitivity, which was evaluated by the euglycemic-hyperinsulinemic-clamp technique, in 54 patients with impaired glucose tolerance (IGT) or non-insulin dependent diabetes mellitus (NIDDM) who were not receiving insulin therapy. The frequencies of Trp/Trp, Trp/Arg, and Arg/Arg genotypes in the patients were 63.0, 33.3, and 3.7%, respectively, which did not differ significantly from those of the 227 controls (67.0, 33.3, and 3.7%, respectively, which did not differ significantly from those of the 227 controls (67.0, 31.3, and 1.8%, respectively). The mean glucose infusion rate of the 34 patients with Trp/Trp did not differ from that of the 18 patients with Trp/Arg (4.3 +/- 2.2 and 5.3 +/- 2.4 mg/kg/min, respectively); while that of the 2 patients with Arg/Arg was 11.5 mg/kg/min. There were no differences in the BMI or fat distribution in the abdomen between each genotype of patients, although the frequency of the Arg64 allele tended to increase with body mass index (BMI) in the control subjects under 60 years of age, which suggests that the mutation is involved in weight gain.  相似文献   
878.
Summary A new polyamide macromer having a vinylbenzyl end group (1), of which molecular weight was 3700–3800, was prepared by the anionic polymerization of bicyclic oxalactam (2) followed by the reaction with p-vinylbenzylamine. Its radical copolymerization with styrene was conducted to obtain a novel graft copolymer consisting of a polystyrene stock-chain and hydrophilic polyamide branches.  相似文献   
879.
A widely wavelength tunable laser combining a semiconductor optical amplifier, an acousto-optic tunable filter and a Fabry-Perot etalon has been developed. It exhibited good characteristics over a 132 nm (1480-1612 nm) tuning range.  相似文献   
880.
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