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   825篇
  免费   29篇
电工技术   24篇
综合类   1篇
化学工业   236篇
金属工艺   20篇
机械仪表   18篇
建筑科学   9篇
能源动力   23篇
轻工业   146篇
水利工程   1篇
无线电   32篇
一般工业技术   106篇
冶金工业   183篇
原子能技术   8篇
自动化技术   47篇
  2023年   4篇
  2022年   12篇
  2021年   30篇
  2020年   9篇
  2019年   12篇
  2018年   12篇
  2017年   15篇
  2016年   11篇
  2015年   9篇
  2014年   34篇
  2013年   34篇
  2012年   34篇
  2011年   48篇
  2010年   31篇
  2009年   38篇
  2008年   25篇
  2007年   25篇
  2006年   23篇
  2005年   28篇
  2004年   25篇
  2003年   30篇
  2002年   24篇
  2001年   18篇
  2000年   16篇
  1999年   20篇
  1998年   59篇
  1997年   43篇
  1996年   38篇
  1995年   14篇
  1994年   21篇
  1993年   21篇
  1992年   6篇
  1991年   5篇
  1990年   7篇
  1989年   7篇
  1988年   9篇
  1987年   5篇
  1986年   3篇
  1985年   8篇
  1984年   5篇
  1983年   2篇
  1982年   4篇
  1981年   3篇
  1979年   7篇
  1978年   1篇
  1977年   3篇
  1976年   9篇
  1975年   1篇
  1974年   2篇
  1973年   2篇
排序方式: 共有854条查询结果,搜索用时 31 毫秒
1.
In order to investigate the influence of puffer volume V/sub P/ and operating force to dielectric performance of GCB at current interruption, we calculated the prospective dielectric withstand voltage V/sub W/ between arcing contacts. The withstand voltage was calculated by the electric field strength appeared on arcing contacts and the allowable electric field strength E/sub W//sup */ of hot gas due to thermal puffer action. We could clarify that large initial puffer volume V/sub P/ can increase withstand voltage V/sub W/ at current breaking point and also that an optimum point exists in operating force F. For example, it was found that in case of the operating force of 1000 kgf, the puffer volume V/sub P/ of 1.2 liter would be best choice in the interrupting condition of i=50 kA and arcing time of 1.35 cycle.  相似文献   
2.
The presence of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) activities was determined in milk and serum of cows with naturally occurring coliform mastitis (CFM). TNF-alpha was detected in the sera from 26 of 32 cows with CFM. TNF-alpha levels were higher in the sera than in the milk. IL-6 was high in the sera of surviving CFM animals, but was low in animals that died and in healthy controls. Furthermore, the mean level of IL-6 was 20-fold higher in the milk than in the sera of mastitic cows. The level of IL-6 in the serum was correlated to that in the milk in individual animals. The presence of IL-6 and TNF-alpha in the sera appears to relate to severe clinical condition of CFM, in the milk whereas they may play a role in generating inflammation of the mammary gland.  相似文献   
3.
Yayoi Yoshioka  Kohji Tashiro 《Polymer》2003,44(22):7007-7019
Structural changes in the Brill transitions of Nylon 10/10 and its model compounds have been investigated by carrying out the temperature-dependent measurements of X-ray diffraction and infrared spectra along with the DSC measurement. The crystal structure at room temperature was found to be the so-called α form with the all-trans zigzag methylene segments. When the samples were heated, the infrared progression bands of the methylene segments, which are sensitive to the length of all-trans segmental parts, were found to change their spectral patterns in the transition temperature region: the progression bands decreased in intensity and disappeared above the transition region. At the same time several new bands were observed to appear, which were found to correspond to the progression bands of (CH2)7-(CH2)5trans-zigzag segments. These spectral changes indicate that the methylene segments were conformationally disordered by an invasion of some gauche bonds and as a result the effective length of trans-zigzag segments became shorter. This conformational disordering was found to occur more remarkably in the methylene segment of NH-(CH2)10-NH part than the CO-(CH2)8-CO part. At the same time the infrared bands of amide groups, in particular the bands sensitive to the twisting angles about the CH2-amide bonds were found to show the remarkable change, indicating the local conformational change from planar-zigzag to twisted form in the CH2-amide moiety. The frequency shift of amide A band (NH stretching mode) indicated a weakening of intermolecular hydrogen bonds, which however, did not disappear up to the melting region. From these data combined with the X-ray diffraction data, the structural disordering in the Brill transition phenomena was deduced concretely.  相似文献   
4.
Understanding the topographical relationships between phosphatidylserine (PS) and protein kinase C (PKC) within neurons can provide clues about the mechanism of translocation and activation of PKC. For this purpose we applied monoclonal antibodies (Abs) of PS and PKC to sections of developing rat cerebellum. The anti-PKC Ab immunohistochemical pattern showed homogeneous staining of Purkinje cells over various postnatal ages, whereas the anti-PS Ab staining showed a heterogeneous localization over these ages. Purkinje cells did not stain well between postnatal day 14 (PND 14) and PND 21, suggesting that the PS was lost from the membrane during preparation of the sections during this period. These data imply that interactions between PS and PKC vary in Purkinje cells during postnatal development.  相似文献   
5.
6.
Two patients with polymyositis (PM) or dermatomyositis (DM) complicated with massive pleural effusion are reported here. Both patients presented a high-grade fever, pleural effusion prominent on the right, and good response to steroid therapy. In a 50-year-old woman with PM, combined process of pleural inflammation, cardiomyopathy and coexisting hypothyroidism were considered to be responsible for the accumulation of the massive pleural effusion. However, in a 34-year-old man with DM, pleural inflammation associated with interstitial pneumonia or pleural microvasculopathy in DM was considered to be responsible for the accumulation of the massive pleural effusion.  相似文献   
7.
This paper shows the value of Doppler ultrasound of the uterine blood flow in predicting the effect of GnRHa on myoma uteri. Thirty-eight patients with myoma uteri were divided into two groups by Doppler ultrasound before treatment: a group with positive arterial blood flow in or around the myoma nodule, and another group with negative arterial blood flow. Histological examinations which were performed in thirty patients demonstrated that the myoma in the negative blood flow group showed higher hyalinization with poor vascularization. In fifteen patients treated with GnRHa (Buserelin 900 micrograms/day), a significant increase (p < 0.01) in the resistance index of the uterine arteries was induced and suppressed the serum estradiol concentration in all cases during GnRHa therapy. The size of the myoma nodules also decreased in all 6 patients in the positive blood flow group, but in only 3 of the 9 patients in the negative blood flow group during GnRHa therapy. These results indicated that Doppler assessments of the arterial blood flow in myoma would be useful in predicting the effect of GnRHa on myoma uteri.  相似文献   
8.
Amorphous SnOx films were deposited by ion-beam sputtering on sintered alumina substrates. Amorphous film sensors were prepared by annealing the films at 300° C for 2 h in air. The thickness dependence of resistivity and hydrogen gas sensitivity were measured at 150° C over the thickness range 1 to 700 nm. A resistivity maximum was observed in ultrathin films. Resistivity increased by three orders of magnitude with increasing film thickness from 0.9 to 7.4 nm and then decreased by five orders of magnitude from 7.4 to 35 nm. Ultrathin film sensors showed sensitivity maxima around a thickness of 10 nm. Sensitivity and resistivity of ultrathin films were significantly influenced by the thermal expansion coefficient and the surface state of the substrate.  相似文献   
9.
Cripto-1 is a member of the EGF-CFC/FRL1/Cryptic family and is involved in embryonic development and carcinogenesis. We designed a novel anti-Cripto-1 artificial antibody and assessed the recognition to the antigen and the potential to suppress the growth of cancer stem cells. First, single chain antibody clones were isolated by bio-panning with the affinity to recombinant Cripto-1 protein from our original phage-display library. Then, the variable regions of heavy chain VH and light chain VL in each clone were fused to constant regions of heavy chain CH and light chain CL regions respectively. These fused genes were expressed in ExpiCHO-S cells to produce artificial humanized antibodies against Cripto-1. After evaluation of the expression levels, one clone was selected and the anti-Cripto-1 antibody was produced and purified. The purified antibody showed affinity to recombinant Cripto-1 at 1.1 pmol and immunoreactivity to cancer tissues and cell lines. The antibody was available to detect the immunoreactivity in tissue microarrays of malignant tumors as well as in Cripto-1 overexpressing cells. Simultaneously, the antibody exhibited the potential to suppress the growth of human colon cancer derived GEO cells overexpressing Cripto-1 with IC50 at approximately 110 nM. The artificially humanized antibody is proposed to be a good candidate to target cancer cells overexpressing Cripto-1.  相似文献   
10.
New biomarkers are needed to further stratify the risk of malignancy in intraductal papillary mucinous neoplasm (IPMN). Although microRNAs (miRNAs) are expected to be stable biomarkers, they can vary owing to a lack of definite internal controls. To identify universal biomarkers for invasive IPMN, we performed miRNA sequencing using tumor-normal paired samples. A total of 19 resected tissues and 13 pancreatic juice samples from 32 IPMN patients were analyzed for miRNA expression by next-generation sequencing with a two-step normalization of miRNA sequence data. The miRNAs involved in IPMN associated with invasive carcinoma were identified from this tissue analysis and further verified with the pancreatic juice samples. From the tumor-normal paired tissue analysis of the expression levels of 2792 miRNAs, 20 upregulated and 17 downregulated miRNAs were identified. In IPMN associated with invasive carcinoma (INV), miR-10a-5p and miR-221-3p were upregulated and miR-148a-3p was downregulated when compared with noninvasive IPMN. When these findings were further validated with pancreatic juice samples, miR-10a-5p was found to be elevated in INV (p = 0.002). Therefore, three differentially expressed miRNAs were identified in tissues with INV, and the expression of miR-10a-5p was also elevated in pancreatic juice samples with INV. MiR-10a-5p is a promising additional biomarker for invasive IPMN.  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