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   154160篇
  免费   2101篇
  国内免费   658篇
电工技术   3135篇
综合类   187篇
化学工业   24463篇
金属工艺   5821篇
机械仪表   4974篇
建筑科学   4510篇
矿业工程   398篇
能源动力   4031篇
轻工业   17593篇
水利工程   1157篇
石油天然气   626篇
武器工业   5篇
无线电   20697篇
一般工业技术   29167篇
冶金工业   24449篇
原子能技术   2358篇
自动化技术   13348篇
  2019年   854篇
  2018年   1117篇
  2017年   1157篇
  2016年   1302篇
  2015年   1102篇
  2014年   1859篇
  2013年   6686篇
  2012年   3277篇
  2011年   4716篇
  2010年   3668篇
  2009年   4232篇
  2008年   4762篇
  2007年   5012篇
  2006年   4427篇
  2005年   4182篇
  2004年   4058篇
  2003年   3964篇
  2002年   3974篇
  2001年   4042篇
  2000年   3772篇
  1999年   3744篇
  1998年   6833篇
  1997年   5360篇
  1996年   4547篇
  1995年   3774篇
  1994年   3403篇
  1993年   3243篇
  1992年   2820篇
  1991年   2717篇
  1990年   2656篇
  1989年   2638篇
  1988年   2482篇
  1987年   2187篇
  1986年   2142篇
  1985年   2579篇
  1984年   2334篇
  1983年   2218篇
  1982年   2080篇
  1981年   2001篇
  1980年   1877篇
  1979年   1882篇
  1978年   1786篇
  1977年   2105篇
  1976年   2617篇
  1975年   1595篇
  1974年   1437篇
  1973年   1466篇
  1972年   1208篇
  1971年   1120篇
  1970年   955篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
In this study, the effect and side-effect of epidural injection with lappaconitine compound for post-operative analgesia was observed. One hundred and twenty patients were randomly divided into 4 groups. Lappaconitine compound (LB) consisted of 12 mg of lappaconitine and 22.5 mg of bupivacaine, was given to group A (the group of observation), and lappaconitine 12 mg, bupivacaine 22.5 mg and morphine 2 mg to group B, C and D respectively for control. All were given by epidural injection with single blind method during post-operative pain of incision operation. Result showed that the initiating of analgesia was quicker in group A and C than that in group B and D, and the efficacy was group D > A > C > B. There was significant difference between group A and B in the above two parameters, P < 0.01 and P < 0.05. The analgisia maintenence time of single injection was D > A > B > C, that of group D was significantly longer than that of group A (P < 0.01). It indicated that the epidural injection with LB was more rapid and potent than that with lappaconitine alone in post-operative analgesia, and the former had no side-effect, it was safer than morphine.  相似文献   
122.
123.
The Department of Veterans Affairs, Social Work Service has designed, developed and implemented the Social Work Information Management System (SWIMS) which provides for the collection and reporting of both administrative and clinical information. This paper describes the implementation of one component of SWIMS, the automated Social Work Data Base/Assessment. The discussion details the implementation process and discusses issues encountered in the implementation of a computerized documentation system.  相似文献   
124.
A review of isolates of Neisseria meningitidis and other laboratory evidence of meningococcal infection was carried out for the period 1990-1995. Thirty-three patients with evidence of meningococcal disease were identified over the six year period. Group B organisms were the most commonly identified, but an increase in Group C has occurred and is almost equal in number. Data from clinical, laboratory and public health sources should be centralized in a National Surveillance Centre.  相似文献   
125.
Tumor suppressor genes such as p53 contribute to the oncogenic process via loss-of-function mechanisms such as genetic mutation or complex formation with other cellular or viral proteins. p53 is mutated in approximately 50% of human tumors and has an important role in the genesis or progression of both colorectal and hepatocellular cancers. Colorectal cancer is leading cause of cancer mortality in the United States, whereas hepatocellular cancer is the leading worldwide cause of cancer death; the liver is a primary site of morbidity in both diseases. Because systemic tumor suppressor gene therapy is currently not feasible, we have chosen to develop a regional form of such therapy directed at primary or metastatic liver neoplasms. Gene replacement therapy with p53 is a promising new strategy to treat advanced human cancers.  相似文献   
126.
14 medicated hypertensive, 15 nonmedicated mild hypertensive, 39 normotensive, and 13 hypotensive adults participated in a 1–2 hr laboratory experiment that assessed each S's symptoms, moods, and estimates of systolic blood pressure (SBP) relative to actual SBP levels. Several self-reports and autonomic measures were collected during and after each of 22 tasks. Within-S correlations indicated that all Ss could estimate SBP at levels greater than chance. Further, 68% of the Ss evidenced at least 1 significant symptom–SBP correlation. Although medicated hypertensives believed they could estimate their BP more accurately than other groups, they were actually no more accurate than the other Ss. They also evidenced far fewer empirically derived symptom–SBP and emotion–SBP correlations than any other group. Overall, blood pressure (BP) beliefs were largely inaccurate. If these erroneous beliefs can be eliminated, Ss may be able to estimate BP fluctuations more accurately. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
127.
128.
In this paper, a physics-based mismatch model is presented. It is demonstrated on a 0.18-/spl mu/m technology that a simple mismatch model can still be used to characterize deep-submicron technologies. The accuracy of the model is examined and found to be within 20% in the strong inversion region. Bulk bias dependence is modeled in a physical way. To extract the mismatch parameters, a weighted fit is introduced. It is shown that the width and length dependence of the mismatch parameters is given by the Pelgrom model.  相似文献   
129.
An attack on the public key cryptosystem Polly Cracker is described, that reveals the complete secret key σ ∈ Fq n by means of n (nonadaptively) chosen "fake" ciphertexts  相似文献   
130.
Using AuGeNiCr multilayered metals as the wafer bonding medium, long-wavelength GaInAsP/InP vertical cavity surface emitting lasers employing Al-oxide/Si as the upper and lower distributed Bragg reflectors were fabricated on Si substrate with the bonding interface formed outside the vertical cavity surface emitting laser cavity. Laser emission at 1.545 μm was measured under pulsed operations near room temperature. The low-temperature metallic bonding process demonstrates a great potential in device fabrication  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