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   1618篇
  免费   35篇
  国内免费   5篇
电工技术   100篇
综合类   7篇
化学工业   390篇
金属工艺   41篇
机械仪表   34篇
建筑科学   20篇
能源动力   52篇
轻工业   111篇
水利工程   10篇
无线电   150篇
一般工业技术   292篇
冶金工业   292篇
原子能技术   46篇
自动化技术   113篇
  2023年   11篇
  2022年   13篇
  2021年   20篇
  2020年   17篇
  2019年   27篇
  2018年   22篇
  2017年   24篇
  2016年   33篇
  2015年   25篇
  2014年   39篇
  2013年   78篇
  2012年   60篇
  2011年   110篇
  2010年   51篇
  2009年   75篇
  2008年   83篇
  2007年   64篇
  2006年   49篇
  2005年   57篇
  2004年   42篇
  2003年   57篇
  2002年   43篇
  2001年   28篇
  2000年   35篇
  1999年   33篇
  1998年   119篇
  1997年   73篇
  1996年   60篇
  1995年   28篇
  1994年   30篇
  1993年   38篇
  1992年   14篇
  1991年   16篇
  1990年   16篇
  1989年   17篇
  1988年   13篇
  1987年   8篇
  1986年   10篇
  1985年   17篇
  1984年   11篇
  1983年   5篇
  1982年   11篇
  1981年   7篇
  1980年   8篇
  1979年   3篇
  1978年   10篇
  1977年   7篇
  1976年   18篇
  1975年   9篇
  1973年   4篇
排序方式: 共有1658条查询结果,搜索用时 0 毫秒
201.
Previous in vitro studies have suggested that calreticulin (CALR), which is responsible for the folding and quality control of glycoproteins, may be associated with decidualization. However, its precise role in regulating decidualization has not been explored in vivo. Here, we used pregnant rat models to examine endometrial CALR expression during the peri-implantation period. We also examined whether polypectomy, a procedure that could ameliorate infertility, alters the endometrial expression levels of CALR and several implantation factors in women diagnosed as infertile. In rats, uterine CALR was expressed at a high level at the implantation site, and a marked increase in CALR expression was observed in decidual cells of normal pregnancy. In addition, endometrial CALR expression was enhanced by either administration of estradiol-17β in the delayed implantation rat model or the artificial induction of decidualization in the pseudopregnant rat. In cultured stromal cells, siRNA-mediated silencing of CALR inhibited the decidual stimulus-induced expression of prolactin, decidual/trophoblast prolactin-related protein, and connexin 43. In humans, the endometrial expression levels of the mRNAs encoding CALR and the implantation-related factor insulin-like growth factor binding protein (IGFBP)-7 tended to increase after polypectomy. The strongest positive correlation between expression levels before polypectomy was observed for IGFBP-7 and CALR, and the strength of this correlation increased after the surgery. Thus, endometrial CALR may play a role in the formation of decidua, and the polypectomy of infertile patients may result in the co-operative expression of endometrial factors, including CALR, that could enhance endometrial receptivity.  相似文献   
202.
203.
High‐pressure, pulsed glow discharge has been studied for the excitation discharge in TEA gas lasers. Various instabilities occur in the subsequent discharge, which induce the arc and collapse for the highly repetitive operation. In this paper, the influences of the gas density depletion on the high‐pressure, pulsed glow discharge have been investigated, eliminating the other instabilities such as shock waves, residual ions, discharge products, and electrode heating. The gas density depletion was produced by utilizing a subsonic flow between the curved electrodes. The comparison has been made on the discharge occurring in the presence of the gas density depletion with that by the double‐pulse experiment in a stable gas. The big gas density nonuniformity tends to cause the arc without the shocks, ions, discharge products, and electrode heating. The transition from glow to arc discharge discontinuously occurs with respect to the gas density depletion. On the other hand, the second discharge in the double‐pulse experiment becomes an arc in much smaller gas density nonuniformity, and the transition from glow to arc occurs gradually. The arc discharge might be driven by some factors other than the gas density depletion. © 2000 Scripta Technica, Electr Eng Jpn, 130(4): 9–16, 2000  相似文献   
204.
205.
Superconducting ac machines such as transformers and reactors are expected to have an important role in future electric power transport lines. In these machines, superconducting coils are wound with superconducting cables that have low ac loss, stable ac quenching current, and high normal resistivity. We have developed Nb-Ti superconducting cables with ultrafine filaments and high-resistivity matrix for these coils. One such cable is a double-stranded round structure using 0.2-mm strands with 0.14-μm filaments and Cu-30wt%Ni as a matrix material. The 50-Hz quenching current without external magnetic field exceeds 1400 Arms. The ac loss is 15 kW/m3 at a transverse external magnetic field of 0.5 T, 50 Hz, and the normal resistivity is 0.21 Ω/m at 0 T, 10 K. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 8–18, 1997  相似文献   
206.
Video Scene Annotation Based on Web Social Activities   总被引:1,自引:0,他引:1  
This article describes a mechanism to acquire the semantics of video content from the activities of Web communities that use a bulletin-board system and weblog tools to discuss video scenes.  相似文献   
207.
World Health Organization grade II and III gliomas most frequently occur in the central nervous system (CNS) in adults. Gliomas are not circumscribed; tumor edges are irregular and consist of tumor cells, normal brain tissue, and hyperplastic reactive glial cells. Therefore, the tumors are not fully resectable, resulting in recurrence, malignant progression, and eventual death. Approximately 69–80% of grade II and III gliomas harbor mutations in the isocitrate dehydrogenase 1 gene (IDH1), of which 83–90% are found to be the IDH1-R132H mutation. Detection of the IDH1-R132H mutation should help in the differential diagnosis of grade II and III gliomas from other types of CNS tumors and help determine the boundary between the tumor and normal brain tissue. In this study, we established a highly sensitive antibody-based device, referred to as the immuno-wall, to detect the IDH1-R132H mutation in gliomas. The immuno-wall causes an immunoreaction in microchannels fabricated using a photo-polymerizing polymer. This microdevice enables the analysis of the IDH1 status with a small sample within 15 min with substantially high sensitivity. Our results suggested that 10% content of the IDH1-R132H mutation in a sample of 0.33 μl volume, with 500 ng protein, or from 500 cells is theoretically sufficient for the analysis. The immuno-wall device will enable the rapid and highly sensitive detection of the IDH1-R132H mutation in routine clinical practice.  相似文献   
208.
We investigated the effect of platelet-activating factor (PAF) and of the PAF specific antagonist CV-6209 on plasma lipid metabolism, and particularly on post-heparin plasma lipolytic activity in male Wistar rats. Lipoprotein lipase (LPL) activity was enhanced by intravenous injection of PAF before intravenous injection of heparin when the PAF dose was low (0.2 μg/kg). PAF activated hepatic triacylglycerol lipase (HTGL) activity dose-dependently. Plasma triacylglycerols (TG) significantly decreased with the activation of LPL and/or HTGL. Plasma total cholesterol (TC) and phospholipid (PL) levels decreased at a low dose of PAF (0.2 μg/kg), but increased when higher doses were used. The PAF antagonist CV-6209 partially reversed the PAF induced effects on HTGL, TC and PL. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.  相似文献   
209.
New antioxidants, cassumunarins A, B, and C, were isolated from the rhizomes ofZingiber cassumunar, and the structures were determined by spectroscopic methods to be complex curcuminoids. The antixidant efficiency of cassumunarins was determined by inhibitory activity of autoxidation of linoleic acid in a buffer-ethanol system. The anti-inflammatory effect was measured by inhibition of edema formation on mouse ear induced by 12-O-tetradecanoylphorbol-13-acetate. Both types of activities were stronger for the cassumunarins than for the curcumin. Visiting scholar at University of Texas (October 1992–September 1993).  相似文献   
210.
Summary 3-(N-Carbazolyl)-1-propyne polymerized with MoCl5- and WCl6-based catalysts to produce a polymer in high yields. The MoCl5 and MoCl5-n-Bu4Sn catalysts were the most effective (the systems solidified immediately after initiation of polymerization with these catalysts). The product polymer was a yellow solid insoluble in any solvent. Copolymerization of the present monomer with tert-butylacetylene by MoCl5-n-Bu4Sn produced a copolymer; it had a high molecular weight (M w 350,000), completely dissolved in toluene, CHCl3 etc, and formed a free-standing film by solution casting. -N-Carbazolyl-1-hexyne and-1-octyne produced toluene-insoluble polymers with WCl6-Ph4Sn.  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