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   3461篇
  免费   6篇
  国内免费   1篇
电工技术   2篇
综合类   3篇
化学工业   24篇
金属工艺   3篇
机械仪表   2篇
建筑科学   9篇
矿业工程   1篇
能源动力   3篇
轻工业   10篇
石油天然气   1篇
武器工业   2篇
无线电   10篇
一般工业技术   8篇
冶金工业   3374篇
自动化技术   16篇
  2022年   2篇
  2021年   1篇
  2020年   1篇
  2017年   2篇
  2016年   2篇
  2014年   1篇
  2013年   6篇
  2012年   1篇
  2011年   26篇
  2010年   5篇
  2009年   2篇
  2008年   2篇
  2006年   1篇
  2005年   4篇
  2004年   5篇
  2003年   10篇
  2002年   3篇
  2000年   3篇
  1999年   118篇
  1998年   1125篇
  1997年   653篇
  1996年   389篇
  1995年   194篇
  1994年   178篇
  1993年   228篇
  1992年   13篇
  1991年   28篇
  1990年   27篇
  1989年   41篇
  1988年   33篇
  1987年   33篇
  1986年   16篇
  1985年   25篇
  1984年   1篇
  1983年   7篇
  1982年   17篇
  1981年   13篇
  1980年   26篇
  1979年   1篇
  1978年   10篇
  1977年   75篇
  1976年   136篇
  1971年   1篇
  1955年   3篇
排序方式: 共有3468条查询结果,搜索用时 15 毫秒
991.
The insulin-like growth factors (IGF-I and IGF-II) play a key role in cellular proliferation and are involved in cellular transformation. The expression of the IGF-I receptor has been demonstrated in a variety of human tumor cell lines including ovarian cancer cells. Phosphorothioate antisense oligodeoxynucleotides (S-ODNs) were analyzed for their potential to suppress the IGF-I receptor in the NIH: OVCAR-3 ovarian cancer cell line. The application of the antisense S-ODN reduced potently the cell growth of unstimulated NIH:OVCAR-3 cells, whereas sense and mismatch S-ODNs were without any effect. This effect resembled that of the monoclonal antibody (MAb) alphaIR-3. In contrast to the antisense compound, this MAb only partially inhibited the IGF-I-induced proliferation of ovarian cancer cells. The concentration of the antisense S-ODN to exhibit an identical inhibition of cell proliferation was reduced to 50 nM when the oligonucleotides were delivered by the cationic lipid formulation lipofectin. The specificity of the antisense S-ODN action was confirmed by reduction of the receptor protein and of the receptor mRNA, as assayed by flow cytometry and by Northern blot hybridizations. Our data demonstrate the potency of antisense S-ODNs to target the IGF-I receptor message and show that antisense strategies against the IGF-I receptor may provide new strategies for the therapy of ovarian cancer.  相似文献   
992.
993.
The mixing between a hot turbulent flow and a cold fluid, injected through a porous plate or using a discrete injection, is experimentally investigated. The blowing is shown to dramatically modify the dynamic and thermal fields, whereas the discrete injection has a weaker effect. The influence on the average quantities and fluctuating parts are found to be different. The effect of the main flow temperature is addressed and a discussion for the mixing in the blowing and discrete injection cases is proposed.  相似文献   
994.
采用热分析、X射线衍射、扫描电镜等方法对Mo-La2O3阴极中La2O3与Mo2C的反应情况进行了研究.实验结果表明:La2O3与Mo2C在高温下可以发生化学反应,产生单质La和金属Mo;反应物存在状态不同,二者发生反应的温度不同. 粉末样品中二者反应温度(1203K)低于阴极丝中二者的反应温度(1533K).  相似文献   
995.
吴春  聂芊  张若男  李健 《化学与粘合》2002,(6):297-299,300
制备了纤维素氧磷-钯配合物催化剂,详细考察了催化剂对三(正)丁基锡氢化物和酰卤化合物偶联反应的催化作用。结果表明,该负载型高分子配合物催化剂对偶联反应具有很高的催化活性和化学选择性,分离容易,可重复使用,用XPS方法对催化机理进行了研究。  相似文献   
996.
采用2种低阶煤——新疆1号,2号不粘煤对含氨氮的焦化废水进行了成浆性试验研究。结果发现,它们的成浆性较差,属难制浆煤种。全面分析了制浆的影响因素,对低阶煤而言,成浆性差是由于煤中富含含氧官能团、较高的内在水分和较差的可磨性。为了进一步了解焦化废水中氨氮对水煤浆流变性的影响,采用不同浓度的含氨氮废水进行了成浆性试验。结果表明,焦化废水中的氨氮对水煤浆的流变性有不利的影响,随着氨氮浓度的升高,水煤浆的表观粘度有升高的趋势,流动性逐渐变差,而稳定性越来越好。  相似文献   
997.
Recently, several clusters of hepatitis A have been observed among hemophiliacs linked to factor VIII concentrates treated for virus inactivation solely with the solvent/detergent (S/D) method, a procedure that does not affect nonenveloped viruses such as the hepatitis A virus (HAV). A new outbreak of hepatitis A in six hemophiliacs treated with the same lot of a factor VIII preparation occurred recently in Germany. The objective of the study was to clarify whether these diseases were caused by the administration of the S/D-treated plasma product, rather than a community-acquired infection. Polymerase chain reactions designed to detect HAV nucleic acid have been carried out in the implicated factor VIII lots, in the corresponding plasma pools, and in serum samples of four out of six infected individuals. The nucleic acid sequences were determined in samples that resulted in positive amplification products. HAV sequences were found in one of the two plasma pools used for manufacture of the incriminated product, in the incriminated lot itself, and in all recipient sera tested so far, although the latter were collected up to 7 weeks after the onset of jaundice. The sequences obtained were completely identical, revealing a unique HAV strain of genotype IA. This study provides conclusive evidence that hepatitis A can be transmitted by factor VIII concentrates treated solely by the S/D procedure for virus inactivation. This inactivation method is not effective against nonenveloped viruses. Since a number of hepatitis A transmission episodes have been described with such preparations during the past 10 years, their continued use seems to be questionable unless additional virus removal or inactivation steps are introduced to prevent the transmission of nonenveloped viruses. Molecular approaches again proved to be reliable tools for elucidating the chain of virus transmission.  相似文献   
998.
999.
Immunoglobulin G (IgG)-mediated phagocytosis by polymorphonuclear leukocytes (PMNL) constitutes the main defense against Streptococcus pneumoniae. Two leukocyte IgG receptors, FcgammaRIIa and FcgammaRIIIb, are constitutively expressed on PMNL. Blocking experiments showed FcgammaRIIa is crucial for opsonophagocytosis of serum-opsonized S. pneumoniae. The biallelic, genetically determined FcgammaRIIa polymorphism (FcgammaRIIa-R131 vs. IIa-H131) determines the capacity of IgG2-mediated phagocytosis via this receptor. Comparative studies with PMNL from donors either homozygous for FcgammaRIIa-R131 or IIa-H131 showed the latter had higher phagocytic capacity. These results were confirmed in FcgammaRIIa-R131- and FcgammaRIIa-H131-transfected IIA1.6 cells. The performance of FcgammaRIIa-transfected cells in S. pneumoniae phagocytosis was validated using sera from adults and children. Serum-induced phagocytic activity depended mainly on anti-pneumococcal IgG2 antibodies. Results obtained with PMNL and IIA1.6 cells showed high correlation (r=0.94; P<.001), and support that FcgammaRIIa transfectants are a good alternative to PMNL as effector cells in opsonophagocytosis assays.  相似文献   
1000.
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