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   2826篇
  免费   39篇
  国内免费   21篇
电工技术   32篇
综合类   4篇
化学工业   334篇
金属工艺   55篇
机械仪表   64篇
建筑科学   42篇
矿业工程   3篇
能源动力   95篇
轻工业   89篇
水利工程   26篇
石油天然气   7篇
无线电   182篇
一般工业技术   371篇
冶金工业   1393篇
原子能技术   25篇
自动化技术   164篇
  2023年   23篇
  2022年   59篇
  2021年   86篇
  2020年   71篇
  2019年   52篇
  2018年   60篇
  2017年   69篇
  2016年   56篇
  2015年   38篇
  2014年   66篇
  2013年   109篇
  2012年   62篇
  2011年   82篇
  2010年   57篇
  2009年   76篇
  2008年   75篇
  2007年   50篇
  2006年   51篇
  2005年   19篇
  2004年   21篇
  2003年   28篇
  2002年   16篇
  2001年   16篇
  2000年   24篇
  1999年   64篇
  1998年   420篇
  1997年   266篇
  1996年   174篇
  1995年   104篇
  1994年   71篇
  1993年   96篇
  1992年   20篇
  1991年   41篇
  1990年   26篇
  1989年   34篇
  1988年   22篇
  1987年   38篇
  1986年   26篇
  1985年   39篇
  1984年   18篇
  1983年   12篇
  1982年   14篇
  1981年   8篇
  1980年   12篇
  1979年   9篇
  1978年   7篇
  1977年   33篇
  1976年   52篇
  1975年   5篇
  1969年   2篇
排序方式: 共有2886条查询结果,搜索用时 0 毫秒
991.
Seven hundred fifty-two patients with stage III disease (of those, 178 patients with inflammatory carcinoma) were treated with a combined modality approach at our institute in seven prospective studies. After three to four cycles of chemotherapy, each patient was treated with local therapy. An estimated 54% of patients with stage IIIA disease and 24% of patients with stage IIIB disease were free of disease. An estimated 30% of patients with inflammatory carcinoma of breast were free of disease beyond 10 years with this approach.  相似文献   
992.
993.
A double-blind, randomized, placebo-controlled crossover study was performed to assess the influence of one week of selective M1-muscarinic receptor blockade on pancreatic exocrine secretion in man. Ten healthy subjects received telenzepine (3 mg p.o.) and placebo each for 8 days, with a 6-day drug-free washout interval between treatment sequences. On Day 8 of each sequence, pancreatic secretion was stimulated for 2 h by infusion of submaximal secretin (0.2 U.kg/h) followed by maximal stimulation with secretin (1.0 U.kg/h) and ceruletide (120 ng.kg/h). Telenzepine had no significant effect on secretory parameters during submaximal stimulation with secretin. During maximal stimulation, total protein, secretory volume, and output of amylase, trypsin and bicarbonate were unexpectedly increased by telenzepine. These findings might be partially explained by removal of the inhibitory influence of pancreatic polypeptide, which was depressed by telenzepine. Acute studies have shown that M1-receptor antagonists inhibit exocrine secretion. Our results suggest that adaptation of physiological mechanisms governing the exocrine pancreas may occur after one week of receptor blockade by a therapeutic dosage of telenzepine, to the extent that M1-blockade no longer inhibits secretion.  相似文献   
994.
995.
996.
Patients with right lower quadrant (RLQ) pain referred for imaging studies with a clinical diagnosis of appendicitis may have other pathologic conditions mimicking appendicitis. Appropriate diagnostic imaging may establish other specific diagnoses and thereby play a significant role in determining proper medical or surgical treatment. In this pictorial essay, we present a spectrum of imaging findings in patients whose clinical features were suggestive of appendicitis, but the diagnoses of a broad spectrum of other diseases were established with the imaging studies. The differential diagnoses of diseases mimicking appendicitis are reviewed.  相似文献   
997.
OBJECTIVE: We compared the use of sedation for helical CT examination of pediatric patients with that for conventional CT studies. MATERIALS AND METHODS: We retrospectively compared two 4-month periods of CT examinations that differed only in that conventional CT was routinely used in one period and helical CT was exclusively used in the other period. For these two periods, we compared the type and number of CT examinations, the sedation used (if any), and the age of patients who required sedation. RESULTS: We performed 1055 conventional CT examinations in 762 pediatric cancer patients. Of the 264 children who were 8 years old or younger, 107 had been sedated. In comparison, 1195 helical CT examinations were performed on 838 patients: of the 246 children 8 years old or younger, 51 received sedation. For both study groups, the mean and median age of the patients was 4 years old. The mean age of patients requiring sedation was 21 (conventional CT) or 20 months (helical CT); the median age of patients who required sedation was 2 years old for both study groups. Patients who were 8 years old or younger and who underwent helical CT required sedation 49% less frequently than such patients who underwent conventional CT. The most dramatic reduction occurred among patients who were 3 years old or younger (p < or = .004). CONCLUSION: Use of helical CT reduced the need for sedation among our pediatric patients. Fewer sedations may reduce the risk of complications, decrease disruption of the patient's normal daily activities, and improve patient throughout. The associated savings in personnel time and pharmaceutical costs can be redistributed.  相似文献   
998.
This objective of this study was to examine the association between a women's HIV status and specific (IDUs) characteristics of her social networks with respect to (1) number of injection drug users (2) number of drug partners and (3) number of HIV-positive contacts in her personal networks, after controlling for the respondent's demographic characteristics and drug use. Participants were recruited through posted announcements in three methadone clinics in Harlem, New York City. Individuals were considered eligible if they were enrolled as patients in one of the clinics for at least three months. A social network questionnaire modeled after the General Social Survey network section was developed by the investigators. Face-to-face interviews were conducted by trained interviewers and included demographics, drug use, self-reported HIV status of the woman and her network members, and the social network structures. Univariate analyses found that HIV-positive and HIV-negative women had different network profiles. HIV-positive women were more likely to associate with a higher number of current drug users, injection drug users, injection drug users who were HIV-positive, drug partners, drug partners who used injection drugs, and drug partners who were HIV-positive. Multivariate analyses indicated that HIV-positive respondents were more likely to associate with HIV-positive network members than their HIV-negative counterparts. The findings suggest that to better understand the spread of HIV among female drug users and to design more effective HIV/AIDS prevention programmes, efforts should move beyond focusing on individual attributes to address the contextual dynamics of social networks.  相似文献   
999.
We have measured the effect of tension on dimerization kinetics of the channel-forming peptide gramicidin A. By aspirating large unilamellar vesicles into a micropipette electrode, we are able to simultaneously monitor membrane tension and electrical activity. We find that the dimer formation rate increases by a factor of 5 as tension ranges from 0 to 4 dyn/cm. The dimer lifetime also increases with tension. This behavior is well described by a phenomenological model of membrane elasticity in which tension modulates the mismatch in thickness between the gramicidin dimer and membrane.  相似文献   
1000.
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