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   2654篇
  免费   97篇
  国内免费   5篇
电工技术   30篇
化学工业   362篇
金属工艺   62篇
机械仪表   51篇
建筑科学   34篇
矿业工程   3篇
能源动力   74篇
轻工业   246篇
水利工程   8篇
石油天然气   16篇
无线电   191篇
一般工业技术   407篇
冶金工业   1019篇
原子能技术   12篇
自动化技术   241篇
  2023年   13篇
  2022年   27篇
  2021年   28篇
  2020年   33篇
  2019年   39篇
  2018年   60篇
  2017年   43篇
  2016年   49篇
  2015年   45篇
  2014年   69篇
  2013年   113篇
  2012年   118篇
  2011年   132篇
  2010年   112篇
  2009年   117篇
  2008年   107篇
  2007年   88篇
  2006年   86篇
  2005年   59篇
  2004年   64篇
  2003年   46篇
  2002年   48篇
  2001年   37篇
  2000年   29篇
  1999年   59篇
  1998年   320篇
  1997年   176篇
  1996年   126篇
  1995年   91篇
  1994年   69篇
  1993年   66篇
  1992年   13篇
  1991年   24篇
  1990年   17篇
  1989年   25篇
  1988年   19篇
  1987年   19篇
  1986年   16篇
  1985年   16篇
  1984年   5篇
  1983年   5篇
  1982年   8篇
  1981年   7篇
  1980年   14篇
  1979年   2篇
  1978年   7篇
  1977年   16篇
  1976年   69篇
  1965年   1篇
  1955年   1篇
排序方式: 共有2756条查询结果,搜索用时 15 毫秒
11.
Rotational and functional motor behavioral changes were studied in five MPTP lesioned chronic hemiparkinsonian Macaca nemestrina monkeys after i.m. pramipexole, a predominant D2 subfamily agonist. Pramipexole induced contraversive rotations in a dose-dependent manner with an optimal dose of 56 microg/kg for approximately 2 to 4 hr after injection. Three different rating scales were used to determine drug-induced functional improvement. They included a monkey parkinsonism rating scale, volitional responses to fruit presentations, and number of hand movements that appeared volitional. A dose of 56 microg/kg of pramipexole produced functional improvements on hand disability, and on a parkinsonian rating scale for monkeys in a dose-dependent manner from 32 to 100 microg/kg. These doses produced an increase in significant hand movements in the affected (contralateral) as well as in the normal (ipsilateral) hand to the side of the brain lesion compared with 5% dextrose in water vehicle control. With a dose of 100 microg/kg, the therapeutic effects of pramipexole on hand movements were less than with 56 microg/kg, due to side effects such as scratching.  相似文献   
12.
13.
Radiation therapy exerts both acute and chronic effects on normal tissue included within treatment fields. The physics of radiation therapy and treatment techniques to minimize deleterious effects of radiation are presented. Management of radiation-damaged skin is discussed. Radiation effect on tissue, wound healing, and tumorigenesis also are reviewed.  相似文献   
14.
The present study, based on 158 HIV seropositives and 167 HIV seronegatives, demonstrates that saliva collected with the Omni-SAL device and tested with GACELISA (an IgG antibody capture ELISA) is an effective non-invasive alternative to serum for anti-HIV IgG antibody screening. The study also shows that a conventional serum Western blot kit can be used, with slight modifications, for confirmatory testing of saliva specimens. Collecting saliva with the Omni-SAL device had a very good acceptance rate among Tanzanian subjects, and although this diagnostic method is not yet known by the general public, 65% of the study participants preferred to give saliva instead of blood for HIV testing.  相似文献   
15.
16.
17.
It is essential to know how the immune system acts in different neurological diseases, some of them non very well known or of unknown etiology at all. It was applied Reiber and Felgenhauer's formula in 56 patients with different diseases. IgA, IgM, IgG and albumin were quantified in sera and cerebrospinal fluid by simple immunodiffusion. It was observed more frequent IgG local synthesis and IgA in this sample.  相似文献   
18.
19.
In this study, 64% of children aged 7–12 yrs with sickle cell disease were found to have a parent-reported behavior problem, and 50% met the criteria for a Diagnostic and Statistical Manual of Mental Disorders-III-Revised (DSM-III-R) diagnosis based on a structured clinical interview of the child. Internalizing types of behavior problems and diagnoses were the most frequent. Support was provided for a transactional stress and coping model in delineating the processes associated with child adjustment. In particular, maternal anxiety accounted for 16–33% of the variance in mother-reported internalizing and externalizing behavior problems, respectively, and child pain-coping strategies accounted for 21% of the variance in child-reported adjustment problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
20.
Wrinkling is a well known phenomenon experimented by tension membranes in Civil Engineering applications. This paper will present an efficient numerical technique for the computational simulation of such wrinkles in a prestressed membrane. In particular, the relaxed energy approach (Pipkin in IMA J Appl Math 36:85–99, 1986) is particularized for prestressed membranes (Gil in Textile composites and inflatable structures, CIMNE, 2003) undergoing moderate strains. Wrinkling conditions in terms of the Euler-Lagrange finite deformation tensor along principal directions will be obtained. This will provide a framework to describe properly the initial instant when wrinkles start to be encountered in a prestressed Saint Venant–Kirchhoff hyperelastic membrane. Subsequently, a modified Helmholtz’s free energy functional will be introduced with the purpose of describing the modified constitutive behaviour of the continuum after the onset of wrinkling. Consistent derivations of the stress tensor as well as the constitutive tensor will de depicted. The results will be particularized for membranes and cables in a Finite Element discretization basis. Some numerical examples will prove the accuracy and robustness of the described algorithm.  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