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   3526篇
  免费   25篇
电工技术   11篇
综合类   2篇
化学工业   113篇
金属工艺   26篇
机械仪表   34篇
建筑科学   34篇
能源动力   5篇
轻工业   78篇
水利工程   6篇
石油天然气   3篇
无线电   71篇
一般工业技术   152篇
冶金工业   2904篇
原子能技术   5篇
自动化技术   107篇
  2021年   7篇
  2019年   11篇
  2018年   12篇
  2017年   15篇
  2016年   13篇
  2015年   6篇
  2014年   15篇
  2013年   28篇
  2012年   23篇
  2011年   32篇
  2010年   17篇
  2009年   24篇
  2008年   24篇
  2007年   36篇
  2006年   46篇
  2005年   26篇
  2004年   27篇
  2003年   23篇
  2002年   22篇
  2001年   22篇
  2000年   24篇
  1999年   104篇
  1998年   852篇
  1997年   484篇
  1996年   353篇
  1995年   188篇
  1994年   153篇
  1993年   166篇
  1992年   34篇
  1991年   38篇
  1990年   34篇
  1989年   38篇
  1988年   33篇
  1987年   37篇
  1986年   34篇
  1985年   39篇
  1984年   13篇
  1983年   15篇
  1982年   24篇
  1981年   24篇
  1980年   32篇
  1979年   14篇
  1978年   20篇
  1977年   71篇
  1976年   195篇
  1975年   16篇
  1973年   6篇
  1972年   9篇
  1971年   9篇
  1967年   6篇
排序方式: 共有3551条查询结果,搜索用时 15 毫秒
41.
42.
43.
To identify factors affecting the chemical stability and preservative efficacy of lamivudine oral liquid formulations, an optimization study using a central composite design was performed. In this design, five factors, each at three levels, were investigated: pH (4.5, 5.5, and 73, sucrose (5%, 20%. and 50% w/v), propylene glycol (0% 2%, and 5% w/v), glycerin (4% 8%, and 12% w/v). and EDTA (0.100. 0.175, and 0.250 mg/mL). All formulations contained a constant concentration of lamivudine, parabens, and artificial strawberry and banana flavors. All formulations were evaluated for preservative effectiveness against USP and BP standards and for chemical stability at 30°C and 40°C for three months. All formulations were effective against bacteria and yeasts, but indicated reduced preservative effectiveness against the mold Aspergillus niger. Preservative effectiveness improved with increasing pH (4.5 to 7.5) and to a lesser extent with increasing EDTA concentration (0.100 to 0.250 mg/mL). Increasing glycerin concentration (4% to 12% w/v) slightly decreased preservative effectiveness. Over the concentration ranges tested, no change in preservative effectiveness was noted with concentration changes in sucrose or propylene glycol. The pH was the main factor influencing the chemical stability of the drug and preservatives in this study. Lamivudine chemical stability increased with increasing pH from 4.5 to 7.5. Methyl and propylparaben showed extensive degradation at pH 7.5.  相似文献   
44.
Treleaven  P. Wells  J. 《Computer》2007,40(7):28-34
Developed largely for the clothing industry, 3D body-surface scanners are transforming our ability to accurately measure and visualize a person's body size, shape, and skin-surface area. Advancements in 3D whole-body scanning seem to offer even greater potential for healthcare applications.  相似文献   
45.
The aim was to investigate whether a truncated recombinant Tissue Factor Pathway Inhibitor (TFPI1-161), which lacked the third Kunitz-type domain and the basic c-terminal region, had an antithrombotic effect comparable to LMWH in a randomised double-dummy study. The experimental thrombosis was induced in jugular veins, in a total of 40 rabbits by a combination of destruction of the endothelium and restricted blood flow. Group 1: placebo, gr 2: LMWH 60 anti-FXa IU/kg, gr 3-5: 0.1, 1.0 and 10.0 mg/kg TFPI1-161. TFPI1-161 reduced the thrombus weights in all treated groups, significantly in doses of 1.0 and 10.0 mg/kg compared to placebo. The frequency of thrombosis and occlusive thrombosis were also significantly reduced in those doses. The antithrombotic properties of TFPI1-161 (1.0-10.0 mg/kg) measured as thrombus weight, frequency of thrombosis and frequency of occlusive thrombosis was equivalent to the anti-thrombotic properties of LMWH. In the anti-FXa, APTT and PT-assays TFPI1-161 displayed a dose dependent increase of activity. Recombinant-TFPI1-161 did not influence the anti-FIIa-assay. No haemorrhagic side effects were noted.  相似文献   
46.
47.
The removal of most ceramic brackets is accomplished by specially designed pliers that apply some form of tensile or shear force to the tooth surface. While the shear and tensile bond strengths for ceramic brackets in vitro have been reported, a simulation of the actual force application when using sharp-edged debonding pliers to debond a bracket has not. The purpose of this study is to determine the effectiveness and the force levels generated by the use of both the wide and the narrow blades in the debonding of ceramic brackets. The present findings indicate that the narrow blades effectively debonded ceramic brackets with a significantly lower mean debonding force (120 kg/cm2) than the wider blades (150 kg/cm2). The surface area of the blade in contact with the bracket-adhesive interface is less for the narrow blade (2.0 mm) than for the wide blade (3.2 mm). This relatively smaller contact area is sufficient to debond a bracket at a significantly lower debonding force.  相似文献   
48.
49.
An initial Bentall operation was performed on a patient aged 38 years with annuloaortic ectasia and aortic regurgitation. An echocardiogram and RI angiogram revealed a perigraft aortic aneurysm on the same patient aged 45 years. The aneurysm gradually developed and the maximum diameter reached 90 mm in size. The Redo-Bentall operation (Piehler modification) was successfully done once again on the same patient aged 56 years. The anastmosis between the right coronary orifice and the graft was detached on all sides. The anastmosis between the left coronary orifice and the graft was detached two thirds of all sides.  相似文献   
50.
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