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   861989篇
  免费   11402篇
  国内免费   2537篇
电工技术   15904篇
综合类   804篇
化学工业   131046篇
金属工艺   32782篇
机械仪表   24713篇
建筑科学   21256篇
矿业工程   4338篇
能源动力   22800篇
轻工业   75132篇
水利工程   8493篇
石油天然气   15436篇
武器工业   57篇
无线电   97807篇
一般工业技术   165455篇
冶金工业   169775篇
原子能技术   17239篇
自动化技术   72891篇
  2021年   7626篇
  2020年   5638篇
  2019年   7107篇
  2018年   11834篇
  2017年   11577篇
  2016年   12376篇
  2015年   8720篇
  2014年   14158篇
  2013年   39061篇
  2012年   22493篇
  2011年   30841篇
  2010年   24726篇
  2009年   27667篇
  2008年   28336篇
  2007年   27732篇
  2006年   24496篇
  2005年   22684篇
  2004年   21674篇
  2003年   21152篇
  2002年   20439篇
  2001年   20336篇
  2000年   19059篇
  1999年   20262篇
  1998年   52186篇
  1997年   36784篇
  1996年   28488篇
  1995年   21249篇
  1994年   18617篇
  1993年   18396篇
  1992年   13180篇
  1991年   12629篇
  1990年   12290篇
  1989年   12019篇
  1988年   11326篇
  1987年   9852篇
  1986年   9755篇
  1985年   11118篇
  1984年   10337篇
  1983年   9298篇
  1982年   8712篇
  1981年   9045篇
  1980年   8514篇
  1979年   8218篇
  1978年   8046篇
  1977年   9720篇
  1976年   12924篇
  1975年   7174篇
  1974年   6751篇
  1973年   6811篇
  1972年   5726篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
Gastrointestinal symptoms are often encountered in patients with diabetes mellitus. Symptoms may arise in any region of the alimentary tract; common symptoms are heartburn, nausea, vomiting, diarrhea, constipation, fecal incontinence, and abdominal pain. This article reviews practical approaches to the identification of the pathophysiologic mechanisms involved in diabetic enteropathies and their complications and briefly outlines strategies to treat these symptoms. Particular emphasis is placed on applied physiologic tests and the choice of pharmacotherapy (e.g., cisapride, erythromycin, or octeotide). The current role of pancreatic transplantations also is briefly reviewed.  相似文献   
105.
For pt.I see ibid., vol.43, no.6, pp.1150-9 (1996). An exact solution of the electrostatic problem for calculating the surface charge and electric field distributions in an arbitrary periodic interdigital transducer (IDT) is given using the results of our companion paper. An arbitrary external electric field may be specified along the electrode structure with the unit cell containing one electrode, or several electrodes, of different widths. The potentials of the electrodes that may be specified are also arbitrary. It is shown that in the case without an external field, the solution includes all the known results as special cases. The case of shorted electrodes in the external electric field is investigated in detail. The surface charge and electric field distributions are calculated for a spatially harmonic external field with an arbitrary wavenumber. The results of the calculations are represented graphically for various ratios between the period of the electrode structure and the wavelength of the external field for the case of a unit cell containing one or two electrodes of different widths  相似文献   
106.
In a prospective study we found good results concerning postoperative complications (21%), perioperative lethality (3.2%) and lethality during hospital stay (6.5%) after implantation of dynamic hip screws (DHS) in patients with per- and subtrochanteric fractures of the femur. The ability to walk, as well as housing and social care postoperatively and follow-up for at least six months after dismissal demonstrates the importance of these fractures for the elderly. One of three patients needs professional care, 21% at home, 13% in nursing homes. Six months after operation the lethality is nearly 20%, i.e. three times higher than in hospital. These are the essential data for all techniques of osteosynthesis used in patients with these fractures, which could only be documented in prospective studies.  相似文献   
107.
108.
In this study chick embryo optic cups at HH stage 13 of development were analyzed under normal conditions and after inoculation with colchicine for 1, 2, 4, and 8 h. Several changes were seen after these periods of treatment: 1) modifications of the structure, with thicker regions in the cup and a general decrease in the total volume according to the duration of exposure to the drug (about 4 times less than normal, 5,035 x 10(3) microns 3 vs 1,334 x 10(3) microns 3 after 8 h of treatment); 2) enlargement of the ventricular cavity and its closure, due to failure of approximation of retinal and pigmentary layers; 3) failure of lens development, with delay and impairment of pit formation and deformation of all structures; lens volume was less than normal (about 4 times less, 2,148 x 10(3) microns 3 vs 658 x 10(3) microns 3 after 8 h of treatment); 4) a general segregation of the cells making up the structure, principally in the more active proliferating zones. The local alterations found are described.  相似文献   
109.
110.
This article presents the results of a pilot-study conducted on a small sample of women with breast cancer and the members of their social support system. The purpose was to determine the potential link between the mental health of the breast cancer patient and their support system. Mental health was assessed with the SCL-90-R (Derogatis, 1977), a self-report scale composed of 90 items divided into nine categories, offering three global indicators of distress: the Global Severity Index (GSI); the Positive Symptom Distress Index (PSDI), and the Positive Symptom Total (PST). The SCL-90-R was distributed to a sample of 14 subjects: seven women treated for breast cancer and seven significant others (social support). The results led to the definition of symptoms such as hostility, phobic anxiety and psychosis specific to either the woman or the support system.  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