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   167617篇
  免费   1325篇
  国内免费   188篇
电工技术   2540篇
综合类   117篇
化学工业   26066篇
金属工艺   9466篇
机械仪表   5704篇
建筑科学   2994篇
矿业工程   1886篇
能源动力   2702篇
轻工业   8715篇
水利工程   2726篇
石油天然气   8689篇
武器工业   12篇
无线电   14475篇
一般工业技术   38235篇
冶金工业   27790篇
原子能技术   6932篇
自动化技术   10081篇
  2018年   2977篇
  2017年   3091篇
  2016年   3344篇
  2015年   1672篇
  2014年   2954篇
  2013年   6338篇
  2012年   4311篇
  2011年   5397篇
  2010年   4420篇
  2009年   4894篇
  2008年   4940篇
  2007年   4868篇
  2006年   4140篇
  2005年   3819篇
  2004年   3634篇
  2003年   3520篇
  2002年   3451篇
  2001年   3463篇
  2000年   3361篇
  1999年   3212篇
  1998年   7018篇
  1997年   5148篇
  1996年   3703篇
  1995年   2903篇
  1994年   2578篇
  1993年   2703篇
  1992年   2239篇
  1991年   2291篇
  1990年   2399篇
  1989年   2301篇
  1988年   2301篇
  1987年   2168篇
  1986年   2234篇
  1985年   2281篇
  1984年   2199篇
  1983年   2119篇
  1982年   1962篇
  1981年   2181篇
  1980年   2048篇
  1979年   2249篇
  1978年   2425篇
  1977年   2422篇
  1976年   3082篇
  1975年   2239篇
  1974年   2296篇
  1973年   2333篇
  1972年   2152篇
  1971年   1902篇
  1970年   1694篇
  1969年   1623篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
992.
The clinical and cytogenetic data of the first patient proven to belong to the fifth Fanconi anemia complementation group are described. The Turkish boy presented with psychomotoric retardation, growth retardation, retarded bone age, brachycephaly, hypotelorism, epicanthus, syndactyly, brachydactyly, renal dystopia, and cryptorchism. In addition, an asymmetrical skeletal anomaly was seen with a double distal phalanx of the left thumb and hypoplasia of the right thumb. Typical hematological features of the disorder developed, at the age of 2.5 years, about 1 year after diagnosis. Cytogenetic studies confirmed the clinical diagnosis and revealed a spontaneous chromosomal instability and hypersensitivity to the cross-linking agents diepoxybutane and Trenimon. The findings in the patient, who is considered to be the standard for the fifth Fanconi anemia complementation group, are compared with data reported for other patients affected with Fanconi anemia.  相似文献   
993.
Patients with carcinoma of the stomach who underwent curative resection were randomized to total gastrectomy (n = 49), total gastrectomy and an S-shaped gastric substitute (n = 28) or subtotal gastrectomy (n = 12); all had a Roux-en-Y reconstruction. The gastric substitute and gastric remnant allowed a volume of 400-500 ml to be installed without increments in basal pressures. The corresponding volume in the Roux limb was 100 ml. Energy intake was approximately 120 kJ/kg preoperative weight per day 3 months after operation, and then remained constant. Patients who had subtotal gastrectomy ate less (91.7 kJ/kg preoperative weight) 3 months after operation, but thereafter increased their intake. Patients allocated to have a gastric pouch or subtotal gastrectomy complained more frequently of adverse postprandial symptoms (P < 0.03) as a major cause of reduced calorie intake. The construction of a gastric reservoir did not improve nutritional adaptation after surgery for gastric carcinoma.  相似文献   
994.
Compositions and technologies are suggested for preparing highly efficient catalyst blocks with a honeycomb structure to be used for reducing nitrogen oxides with ammonia in flue gases from thermal power plants. The blocks have high structural strength and catalytic activity.  相似文献   
995.
Conclusions The calculations for the different levels of volume heat release showed that the integral heat fluxes at the lateral and top surfaces are virtually independent of the scenario of convective flow. However, the maximum of the heat flux on the lateral surface in the homogeneous case is 1.5–1.6 times higher than the maximum heat flux in the stratified case. This could result in larger mechanical loads on the reactor vessel and therefore more stringent requirements on the cooling of the outer surface of the reactor vessel. Institute of Fast Reactors, Russian Academy of Sciences. Translated from Atomnaya énergiya, Vol. 76, No. 5, pp. 406–411, May, 1994.  相似文献   
996.
997.
All-Union Scientific-Research Institute of Nuclear Power Plants NIIP. Translated from Atomnaya énergiya, Vol. 77, No. 5, pp. 392–402, November, 1994.  相似文献   
998.
999.
Cultures of both isolated and conjugated explants from early gastrulae of Bufo arenarum were prepared for a study of the development of ventral mesoderm. Only combinations including components of the deep ventral marginal zone and the animal pole successfully differentiated into blood cells (erythrocytes). Histological studies indicated that, while prospective mesodermal cells constituted the only source of such cells, prospective ectodermal cells provided the necessary stimulus for this kind of differentiation. Differentiated cultures, in which the tracer of cell-lineage fluorescein dextran amine was used to label these components, confirmed the above conclusions. These findings are discussed in the context of current concepts about the formation of mesoderm.  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