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   494篇
  免费   12篇
  国内免费   1篇
电工技术   24篇
化学工业   68篇
金属工艺   6篇
机械仪表   7篇
建筑科学   9篇
能源动力   8篇
轻工业   40篇
石油天然气   2篇
无线电   53篇
一般工业技术   60篇
冶金工业   169篇
原子能技术   11篇
自动化技术   50篇
  2023年   5篇
  2021年   8篇
  2020年   2篇
  2019年   3篇
  2018年   4篇
  2017年   4篇
  2016年   8篇
  2015年   10篇
  2014年   5篇
  2013年   15篇
  2012年   9篇
  2011年   13篇
  2010年   14篇
  2009年   12篇
  2008年   19篇
  2007年   17篇
  2006年   12篇
  2005年   14篇
  2004年   13篇
  2003年   9篇
  2002年   13篇
  2001年   10篇
  2000年   8篇
  1999年   11篇
  1998年   72篇
  1997年   45篇
  1996年   31篇
  1995年   16篇
  1994年   19篇
  1993年   10篇
  1992年   8篇
  1991年   11篇
  1990年   4篇
  1989年   5篇
  1988年   8篇
  1987年   3篇
  1986年   3篇
  1984年   4篇
  1983年   4篇
  1982年   5篇
  1981年   3篇
  1980年   2篇
  1979年   1篇
  1978年   2篇
  1977年   3篇
  1976年   3篇
  1975年   2篇
  1972年   1篇
  1965年   1篇
  1959年   1篇
排序方式: 共有507条查询结果,搜索用时 15 毫秒
1.
Aluminum nitride ceramics were prepared by sintering with 0–4.8 mass% of Ca3Al2O6 (C3A) as a sintering additive. The transmittance in the range of 260–550 nm increased with increasing amount of C3A. The cathodoluminescence intensity attributed to oxygen-induced defects decreased with increasing amount of C3A. From the results, the increase of the transmittance in the range of 260–550 nm was considered to be related to the decrease of the oxygen-induced defect density.  相似文献   
2.
3.
The pulsed KrF excimer laser annealing of silicon films for solar cell with EBEP-CVD and LP-CVD was studied theoretically and experimentally. Three-dimensional thermal diffusion equation for microcrystalline and amorphous silicon was solved by using the finite difference methods. The results of our heat-flow simulation of laser re-crystallization in a laser irradiation with 50 ns pulse duration almost agree with the experimental results in re-crystallization depth of 0.7 μm for microcrystalline silicon (EBEP-CVD) and 0.4 μm for amorphous silicon (LP-CVD) in a single pulse excimer laser annealing.  相似文献   
4.
N(alpha)-Phthalimidoglutarimide (thalidomide), 2-(2,6-diisopropylphenyl)-1H-isoindole-1,3-dione (PP-33) and its 4,5,6,7-tetrafluoro derivative (FPP-33) augmented 12-O-tetradecanoylphorbol 13-acetate-induced production by human leukemia HL-60 cells of both tumor necrosis factor alpha (TNF-alpha) mRNA and secreted TNF-alpha protein. Intracellular TNF-alpha protein production was increased to a lesser extent.  相似文献   
5.
In a fetal autopsy series, we have explored the occurrence of renal tubular dysgenesis in twins. Renal tubular dysgenesis was found exclusively among those monozygotic twins with evidence of twin transfusion syndrome, particularly in those donor twins with oligohydramnios and growth restriction. We infer that hypotension in the donor twin of the twin transfusion syndrome pair is responsible for the failure of proximal convoluted tubule differentiation, and the disturbance of renal function is manifested as oligohydramnios prenatally, and either oliguria or tubular dysfunction postnatally.  相似文献   
6.
BACKGROUND: We determined the types and distribution of glycosaminoglycans (GAGs) and collagens, in anterior capsular opacification after endocapsular phacoemulsification and aspiration (ECPEA) and intraocular lens implantation. METHODS: Opacified anterior capsules were removed from human eyes after ECPEA. Immunohistochemical staining was performed to determine GAGs with monoclonal antibodies to chondroitin, chondroitin-4-sulfate (C4S), chondroitin-6-sulfate (C6S), dermatan sulfate (DS), and keratan sulfate (KS); collagens with monoclonal antibodies to types I, II, and III collagens; and cellular characteristics with monoclonal antibodies to vimentin, desmin, alpha-smooth muscle actin, and cytokeratin. Decorin mRNA and type I collagen mRNA were detected by in situ hybridization. RESULTS: In the capsules, the C6S, DS, KS, and types I and III collagens were similar to the chemical components found at the adhesion site of the anterior and posterior capsules after extracapsular cataract extraction, and cellular components contained vimentin, desmin, alpha-smooth muscle actin, cytokeratin, decorin mRNA, and type I collagen mRNA. CONCLUSIONS: The GAGs and collagens in opacified anterior capsule after ECPEA were similar to those found during wound healing, although KS is present in normal anterior segment tissue during development and only in the cornea postnatally. These chemical components may be produced by myofibroblast-like cells presumably transformed from lens epithelial cells.  相似文献   
7.
The 35 nm gate length CMOS devices with oxynitride gate dielectric and Ni salicide have been fabricated to study the feasibility of higher performance operation. Nitrogen concentration in gate oxynitride was optimized to reduce gate current I/sub g/ and to prevent boron penetration in the pFET. The thermal budget in the middle of the line (MOL) process was reduced enough to realize shallower junction depth in the S/D extension regions and to suppress gate poly-Si depletion. Finally, the current drives of 676 /spl mu/A//spl mu/m in nFET and 272 /spl mu/A//spl mu/m in pFET at V/sub dd/=0.85 V (at I/sub off/=100 nA//spl mu/m) were achieved and they are the best values for 35 nm gate length CMOS reported to date.  相似文献   
8.
The hemostatic effect of aprotinin in pediatric cardiac surgery is controversial. This study demonstrated the usefulness of aprotinin in cases undergoing additional surgery. In a retrospective study, three groups of children were investigated. In group I (n = 10), no aprotinin or Cell saver was used (control). In group II (n = 12), Cell saver was used intraoperatively. In group III (n = 14), aprotinin 30,000 KIU/kg was added to the prime of cardiopulmonary bypass, and another 10,000 KIU/kg was given every hour during extracorporeal circulation. Both blood loss and use of homologous blood during operation were significantly (p < 0.01) reduced in group III compared to those in the other two groups. In group III, blood loss both 12 and 48 hours postoperatively were one-third less than those in group I (no significant difference). The use of homologous blood 48 hours postoperatively was significantly reduced in group III compared to that in group I (p < 0.01) or group II (p < 0.05). We conclude that aprotinin administration during cardiopulmonary bypass reduced blood loss and homologous blood requirements both operatively and postoperatively when pediatric cardiac surgery must be redone.  相似文献   
9.
Rac, a member of the rho family of GTPases, when activated transmits signals leading to actin-based membrane ruffling in fibroblasts. Compared with wild-type fibroblasts, gelsolin null (Gsn-) dermal fibroblasts have a markedly reduced ruffling response to serum or EGF stimulation, which signal through rac. Bradykinin-induced filopodial formation, attributable to activation of cdc42, is similar in both cell types. Wild-type fibroblasts exhibit typical lamellipodial extension during translational locomotion, whereas Gsn- cells move 50% slower using structures resembling filopodia. Multiple Gsn- tissues as well as Gsn- fibroblasts overexpress rac, but not cdc42 or rho, 5-fold. Re-expression of gelsolin in Gsn- fibroblasts by stable transfection or adenovirus reverts the ruffling response, translational motility and rac expression to normal. Rac migrates to the cell membrane following EGF stimulation in both cell types. Gelsolin is an essential effector of rac-mediated actin dynamics, acting downstream of rac recruitment to the membrane.  相似文献   
10.
Summary The size exclusion chromatography of neutral polymers and polymers containing ionic groups was investigated using N,N-dimethylacetamide (DMA) as mobile phase. As reported previously for N,N-dimethylformamide (DMF), acrylonitrile polymers containing charges, even those at terminal end groups, showed markedly small retention volumes and multimodal peaks by refractive index and 280 nm UV detectors. In DMA containing small amounts of LiBr the peaks of the ionic polymers were shifted to small retention volumes while neutral polymers with analogous chemical structures did not show the same behavior. As in the case of DMF the peculiarities observed in DMA were attributed to the formation of supramolecular structures by the interaction of the ionic groups in the polymer and the ionic species from DMA decomposition.  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