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   3676篇
  免费   117篇
  国内免费   2篇
电工技术   56篇
综合类   2篇
化学工业   716篇
金属工艺   118篇
机械仪表   66篇
建筑科学   168篇
矿业工程   29篇
能源动力   52篇
轻工业   335篇
水利工程   22篇
石油天然气   8篇
无线电   296篇
一般工业技术   518篇
冶金工业   1018篇
原子能技术   39篇
自动化技术   352篇
  2021年   45篇
  2020年   50篇
  2019年   44篇
  2018年   60篇
  2017年   42篇
  2016年   68篇
  2015年   57篇
  2014年   79篇
  2013年   87篇
  2012年   115篇
  2011年   136篇
  2010年   114篇
  2009年   109篇
  2008年   116篇
  2007年   112篇
  2006年   101篇
  2005年   126篇
  2004年   79篇
  2003年   77篇
  2002年   82篇
  2001年   88篇
  2000年   82篇
  1999年   79篇
  1998年   301篇
  1997年   178篇
  1996年   129篇
  1995年   114篇
  1994年   85篇
  1993年   91篇
  1992年   56篇
  1991年   55篇
  1990年   53篇
  1989年   48篇
  1988年   37篇
  1987年   34篇
  1986年   35篇
  1985年   42篇
  1984年   30篇
  1983年   31篇
  1982年   38篇
  1981年   37篇
  1980年   27篇
  1979年   48篇
  1978年   20篇
  1977年   44篇
  1976年   89篇
  1975年   22篇
  1974年   15篇
  1972年   18篇
  1971年   15篇
排序方式: 共有3795条查询结果,搜索用时 296 毫秒
11.
12.
IEEE Security & Privacy's associate editor in chief discusses technology's role in identity fraud and identity theft.  相似文献   
13.
14.
Heart transplant patients take several medications that could affect their periodontal health. Gingival overgrowth associated with cyclosporin (immunosuppressant agent) and nifedipine (calcium channel blocker) is well documented. Candidal infections often develop because of immune suppression. This report describes the clinical and histopathological changes in the gingival tissues of a heart transplant patient and their management. The gingival tissues exhibited pronounced enlargement. The gingivae were lobulated, and the surface of the lobulations was pebbly and granular. Biopsies showed lobules of fibrous connective tissue covered by stratified squamous epithelium. The outer surfaces were dotted with numerous smaller papillations. Candidal hyphae were present in the superficial layers of the epithelium. The extensive papillary lesions appear to be related to candidiasis and constitute a condition which is best designated as papillary stomatitis. Hyperplastic gingival tissues were excised, and the patient was placed on periodic maintenance. One-year postoperative follow-up showed minor gingival growth.  相似文献   
15.
Two different plaque variants of Japanese encephalitis virus were selected from a wild-type Taiwanese isolate using Vero cells. One variant was found to exhibit small plaque morphology with retarded virus replication kinetics in Vero cells, and was demonstrated to be resistant to monoclonal antibody (mAb) E3.3 neutralization. The other variant showed large plaque morphology, was sensitive to mAb E3.3 neutralization, and manifested reduced virulence in mice on both intracranial and intraperitoneal inoculations. These two variants propagated in Vero cells retained high levels of infectivity but had relatively low HA titers as compared with the parent strain. The envelope sequences of these two variants showed four amino acid differences at residues E-85 (Glu/Arg), E-306 (Glu/Gly), E-331 (Ser/Arg), and E-387 (Met/Arg). Our results indicated the neutralizing epitope of Japanese encephalitis virus did not overlap with virus virulence determinant.  相似文献   
16.
S. Haas  W. Schneider 《Acta Mechanica》1997,125(1-4):211-215
Summary The laminar flow near an infinite plane wall perpendicular to a line sink of constant strength is investigated in the limit of large Reynolds numbers. Self-similarity requires that fluid is issuing from the boundary layer. The inviscid flow outside the boundary layer is governed by the Euler equations. A one-parametric set of solutions to the Euler equations with appropriate boundary conditions is given. Uniqueness of the inviscid flow solution is obtained from matching with the boundary layer expansion. The solution of the boundary-layer equations is given both in closed form and numerically. It is found that at the edge of the boundary layer the vorticity decays algebraically.Dedicated to Prof. Dr. Dr. h. c. Franz Ziegler on the occasion of his 60th birthday  相似文献   
17.
18.
The demonstration of the first visible resonant cavity light-emitting diodes (RCLEDs) is reported. The devices consist of an InAlGaP strained quantum well active region surrounded by AlAs/AlGaAs distributed Bragg reflectors. Linewidths from 0.9 mm (2.6 meV) to 45 nm (12.8 meV) were obtained by varying the cavity factor (Q).<>  相似文献   
19.
OBJECTIVE: To determine the characteristics and long-term outcome of radiation-induced thyroid cancer in children. DESIGN: Retrospective review of a cohort of 4296 irradiated patients who received childhood radiation treatment to the head and neck area at the same hospital. PATIENTS: Forty-one children who were younger than 20 years when thyroid cancer developed in them and 77 adults in whom thyroid cancer developed. All 118 cases were diagnosed before 1974 and were followed up for a median of 19.4 years. RESULTS: Children presented with clinically palpable lymph nodes more often than adults (30.7% vs 15.1%, P = .05) and had more recurrences (39% vs 16%, P = .05). Despite these frequent recurrences, only one patient (an adult) died of thyroid cancer. Seventy percent of the recurrences occurred during the first 10 years of follow-up, but recurrences continued after 20 years. The adults had previously identified factors that predicted the risk of recurrences, but none could be identified in the children. CONCLUSION: The presentation and relatively good outcome of radiation-induced thyroid cancer in children is similar to that in nonirradiated children. Frequent and late recurrences call for lifelong follow-up.  相似文献   
20.
Replicated the 1st author and J. J. Parkington's (1979) research on the relationships between employees and customers in service organizations by analyzing survey data from 142 employees and 968 customers from 28 branches of a bank. Moderate support was found for the 1st author and Parkington's work on correlates of stress for boundary role employees. Support was also found for relationships between branch employees' and branch customers' service perceptions and attitudes as reported by the present 1st author et al (1980). Significant relationships were reported between branch employees' perceptions of organizational human resources practices and branch customers' attitudes about service. Employee attitudes and customer attitudes were related to their own and one another's turnover intentions. Results are discussed from the perspective of promoting an integration of consumer and organizational behavior in the service sector. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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