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   7980篇
  免费   318篇
  国内免费   17篇
电工技术   73篇
综合类   7篇
化学工业   1546篇
金属工艺   107篇
机械仪表   149篇
建筑科学   328篇
矿业工程   9篇
能源动力   226篇
轻工业   542篇
水利工程   61篇
石油天然气   29篇
武器工业   2篇
无线电   582篇
一般工业技术   1108篇
冶金工业   2367篇
原子能技术   34篇
自动化技术   1145篇
  2023年   67篇
  2022年   107篇
  2021年   173篇
  2020年   123篇
  2019年   125篇
  2018年   176篇
  2017年   158篇
  2016年   193篇
  2015年   160篇
  2014年   223篇
  2013年   407篇
  2012年   366篇
  2011年   428篇
  2010年   326篇
  2009年   370篇
  2008年   353篇
  2007年   368篇
  2006年   264篇
  2005年   253篇
  2004年   207篇
  2003年   188篇
  2002年   157篇
  2001年   105篇
  2000年   112篇
  1999年   134篇
  1998年   511篇
  1997年   384篇
  1996年   230篇
  1995年   203篇
  1994年   161篇
  1993年   154篇
  1992年   76篇
  1991年   41篇
  1990年   62篇
  1989年   83篇
  1988年   64篇
  1987年   50篇
  1986年   59篇
  1985年   62篇
  1984年   44篇
  1983年   57篇
  1982年   37篇
  1981年   47篇
  1980年   54篇
  1979年   26篇
  1978年   21篇
  1977年   76篇
  1976年   154篇
  1975年   31篇
  1974年   22篇
排序方式: 共有8315条查询结果,搜索用时 15 毫秒
91.
In an attempt to validate the use of topographical mapping of EEG as a method of localising cerebral function, EEG was recorded during a simple motor task. A minimum of 20 sec artifact-free EEG was recorded from 24 healthy right handed subjects in each of 4 conditions: eyes open 1, motor task (left/right, order randomized), eyes open 2. EEG amplitude maps were computed in delta, theta, alpha, and beta (1 and 2). Differences were seen between the eyes open and the motor conditions in alpha, beta 1 and beta 2 localised to the motor and supplementary motor areas. It is argued that topographical mapping of EEG is a valid method of localising cognitive function in healthy individuals for the Luria task.  相似文献   
92.
The asymptotic angular stability of a dynamical system may be quantified by its rotation number or its winding number. These two quantities are shown to result from different assumptions, made about the flow generating the Poincaré map which results from the sequence of homeomorphisms in S l. An ergodic theorem of existence a.s. of the rotation number for non-linear systems is given. The advantages and disadvantages of both the rotation and winding numbers are discussed. Numerical calculations of the distribution of rotation number and winding number arising from different initial conditions are presented for three different chaotic maps.  相似文献   
93.
We report a case of homozygous alpha-thalassaemia with hydrops fetalis presenting at 22 weeks of gestation. In utero exchange transfusion was performed with maternal blood at 23 weeks. 25 weeks and 29 weeks of gestation. The fetus was delivered at 29 weeks of gestation without significant neonatal complication. Post-transfusion haemoglobin pattern after transfusion suggested that a total haematocrit of 0.52 may be the desired post-exchange transfusion haematocrit to aim for and the total haematocrit of haemoglobin A and haemoglobin Portland dropped approximately one percent per day.  相似文献   
94.
Haemophilus influenzae is a bacterium of medical interest of which the entire genome has been sequenced. The proteome of the microorganism has been analyzed by two-dimensional gel electrophoresis, during which immobilized pH 3-10 gradient strips were used and approximately 300 proteins were identified. In order to detect additional, basic proteins, we analyzed the soluble protein fraction of H. influenzae and the proteins of fractions collected from affinity chromatography on heparin, by two-dimensional gel electrophoresis, using for the first-dimensional separation immobilized pH gradient strips comprising the pH region of 6-11. The protein spots were analyzed by matrix-assisted laser desorption ionization-mass spectrometry. One hundred and two proteins were identified, of which 58 were identified for the first time. A large percentage of the basic proteins represent nucleic acid binding and, in particular, ribosomal proteins. The locations of the identified basic proteins of H. influenzae are indicated in a two-dimensional map.  相似文献   
95.
ATM promises increased functionality and performance for users and decreased costs for corporate voice and data networks. the tips provided here focus on the vendor selection and installation processes, which are critical to the successful design and implementation of an ATM network.  相似文献   
96.
97.
Atrial natriuretic peptide (ANP) and sodium nitroprusside (SNP) increase cGMP in vascular smooth muscle cells and act as vasodilators in some, but not all, blood vessels. In this present study, we attempted to correlate the ability of these two agents to dilate blood vessels with the ability to increase cGMP in cultured vascular smooth muscle cells. In the isolated guinea pig heart, SNP dose-dependently increased coronary flow while ANP was ineffective. In smooth muscle cells cultured from the coronary system, SNP increased intracellular cGMP in a dose-dependent manner while ANP had no effect on cGMP in these cells. In isolated guinea-pig thoracic aorta, precontracted with K+, both ANP and SNP produced relaxation and ANP was the more potent. In smooth muscle cells cultured from the aorta, ANP and SNP increased cGMP and the potency relationship was similar to the intact vessel. These results support the view that phenotypic properties of vascular smooth muscle cells can account for differences in the response of blood vessels to vasodilators.  相似文献   
98.
LR Goldman  WH Farland 《Canadian Metallurgical Quarterly》1998,279(5351):640-1; author reply 641
  相似文献   
99.
A new interest in replacing neurons lost to trauma or disease has been generated by findings that challenge the traditional view of the static (irreparable) adult brain. The discovery of stem cells and neurogenesis in the adult central nervous system is responsible for much of this interest.  相似文献   
100.
Using a submucosal needle tunneling technique for ureteral implantation, detubularized folded O-shaped ileal bladders were created for seven patients in need of bladder replacement. A segment of ileum of only 300 to 400 mm in length was required. Anastomosis of the reservoir to the urethra was simply performed by tailoring the ileum to reduce tension at the anastomosis site. Follow-up periods ranged from 24 to 46 months. Excellent upper tract function and good evacuation function with minimal residual urine were demonstrated. Urodynamic studies revealed a mean bladder capacity of 367 mL, with low intra-ileobladder pressure. All patients are continent during the day. Mild enuresis was noted in three patients. No reflux was noted on follow-up voiding cystourethrography. This type of ileal bladder is simple to create and provides reliable results. The presence of a short mesentery is not a serious limiting factor.  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