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   1952篇
  免费   29篇
  国内免费   8篇
电工技术   66篇
综合类   1篇
化学工业   346篇
金属工艺   72篇
机械仪表   31篇
建筑科学   17篇
能源动力   38篇
轻工业   167篇
水利工程   1篇
石油天然气   5篇
无线电   277篇
一般工业技术   263篇
冶金工业   565篇
原子能技术   58篇
自动化技术   82篇
  2023年   9篇
  2022年   23篇
  2021年   36篇
  2020年   18篇
  2019年   23篇
  2018年   27篇
  2017年   32篇
  2016年   18篇
  2015年   21篇
  2014年   28篇
  2013年   92篇
  2012年   49篇
  2011年   50篇
  2010年   52篇
  2009年   47篇
  2008年   68篇
  2007年   56篇
  2006年   45篇
  2005年   43篇
  2004年   41篇
  2003年   41篇
  2002年   37篇
  2001年   32篇
  2000年   33篇
  1999年   66篇
  1998年   226篇
  1997年   133篇
  1996年   110篇
  1995年   63篇
  1994年   53篇
  1993年   55篇
  1992年   38篇
  1991年   17篇
  1990年   23篇
  1989年   26篇
  1988年   22篇
  1987年   11篇
  1986年   29篇
  1985年   18篇
  1984年   17篇
  1983年   14篇
  1982年   13篇
  1981年   17篇
  1980年   19篇
  1979年   21篇
  1978年   10篇
  1977年   17篇
  1976年   28篇
  1973年   5篇
  1967年   3篇
排序方式: 共有1989条查询结果,搜索用时 15 毫秒
991.
Carbon fibers produced from PAN (polyacrylonitrile) as a precursor are generally subjected to the three heat treatment processes of stabilization and carbonization followed by graphitization. Stabilized fibers were carbonized in a high magnetic field of 5 T imposed parallel to the fiber axis at a temperature of 1445 K and graphitized without a magnetic field at 2273 K. The tensile strength of these treated fibers is increased by 14% in comparison with those of no magnetic treatment. The reason why the imposition of the magnetic field could improve the strength of the fibers has been studied through microscopic observation of the fiber surface as well as a statistical analysis by use of Weibull distributions.  相似文献   
992.
The authors describe calibration measurements for the efficiency and response function of the NE213 scintillator as an application of a two-dimensional pulse height analysis system. In this method, a 252 Cf spontaneous fission source with a continuous spectrum is employed by taking each fission event as a pulsed neutron source, and the efficiency and response function of the NE213 scintillator can be estimated by two-dimensional measurements of the time-of-flight spectrum (neutron energy spectrum) and pulse height spectrum  相似文献   
993.
Two near full-length cDNAs (LE4CL-1, LE4CL-2), which encode 4-coumarate:CoA ligase (4CL), were cloned from a library of Lithospermum erythrorhizon cell suspension cultures by the use of heterologous probe of potato 4CL. These cDNAs are 2.1 kb and 2.2 kb in length, respectively. LE4CL-1 encodes 636 amino acids, whose homologies to the 4CL protein sequences known to potato, parsley, pine and rice, were found to be 68%, 66%, 56% and 50% (identities on amino acid level), respectively, whereas those of the predicted translation product of LE4CL-2 (594 amino acids) to the above 4CL proteins were 49 approximately 54%. The similarity of the deduced amino acid sequences between the two 4CLs from Lithospermum cell cultures was 49% in identity. Northern analyses showed that the mRNA levels of both LE4CL-1 and LE4CL-2 were much higher under illumination than in the dark, as reported for the 4CL genes of such plants as parsley. In comparison of mRNA levels of LE4CL-1 and LE4CL-2, the former was demonstrated to be generally higher than the latter by means of an application of RT-PCR. The genomic southern blot experiments suggested that there are probably three copies of LE4CL-1 in the Lithospermum genome DNA, whereas only one copy was detected for LE4CL-2.  相似文献   
994.
995.
The patient was a 50-year-old alcoholic man with a left palatine tonsillar ulcer. Histopathological and bacteriological studies established the diagnosis of tonsillar tuberculosis with asymptomatic advanced pulmonary tuberculosis and multiple cerebral supra- and infratentorial tuberculomas previously unnoticed.  相似文献   
996.
We reported the first case of chorea-acanthocytosis associated with low glycohemoglobin A1c. Fasting blood sugar, daily profile of blood sugar, serum fructosamine and 75 g glucose tolerance test were all within normal limits. While abnormal hemoglobins were not detected, red blood cell half-life was sharply reduced to 13.4 days. These findings suggest that the low glycohemoglobin A1c in this case is highly ascribable to the reduction of red blood cell half-life rather than to continuous hypoglycemia. However, we can not rule out that the abnormalities of red blood cell membrane, suggested factors in this disease, may be related to the low glycohemoglobin A1c value. Further investigations on chorea-acanthocytosis cases with normal red blood cell half-life are necessary in order to elucidate whether an abnormal glycohemoglobin A1c value is a specific indication regarding this disease.  相似文献   
997.
EP37 family proteins are non-lens members of the betagamma-crystallin superfamily, of which expression is observed in integumental tissues of the Japanese newt, Cynops pyrrhogaster. In the present study, a gene was isolated that has high homology with ep37 and is transcribed mainly in the gastric epithelial cells and hence designated gep. The predicted amino acid sequence of the gep cDNA contains four betagamma-crystallin motifs in the N-terminal half, as is the case in the integumental EP37 proteins. Immunohistochemical analysis showed that GEP protein was mainly localized on the luminal content of the surface mucous cells of the gastric epithelium in both premetamorphic larvae and adults. In addition, GEP protein was also expressed in fundic glands after metamorphosis. Considering the fact that beta- and gamma-crystallins are evolutionarily related to stress-induced proteins, this localization suggests that GEP protein may have an evolutionarily conserved role in protection against physico-chemical stresses, such as physical abrasion and autodigestion, during assimilation.  相似文献   
998.
We studied T cell responses to four glutathione S transferase (GST)-fused mite antigens prepared in our laboratory using peripheral blood lymphocytes from mite-sensitive patients with bronchial asthma. Of the four recombinant antigens, purified GST-Mag3 had the strongest ability to cause patients' lymphocytes to proliferate, and its potency was almost comparable to that of crude mite bodies (Dfb) and faeces (Dff) antigens and a purified major antigen, Der f 2. The responder lymphocytes were mainly T cells, because the proliferative response was depleted by the treatment of lymphocytes with anti-CD3 antibody and complement, but not with anti-CD20 antibody and complement. The responsiveness of lymphocytes to GST-Mag3 correlated with that to Der f 2, but GST-Mag3 displayed slightly higher activity to stimulate lymphocytes than Der f 2. Simultaneously, the levels of Dff- and GST-Mag3-specific IgE antibodies correlated with the responsiveness of lymphocytes to GST-Mag3. These results suggest that Mag3 is a new valuable antigen for the response of T cell proliferation in mite-sensitive patients.  相似文献   
999.
Preliminary screening of antiviral AIDS drugs has been carried out using three different in vitro assay systems. Among 96 samples of different origin tested, two were shown to inhibit the growth of HIV in vitro. One of the positive samples (plant origin) has hopeful signs, as the ranges of effective doses are wider than those of most of positive samples which had been found by us.  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