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   12375篇
  免费   376篇
  国内免费   19篇
电工技术   83篇
综合类   10篇
化学工业   1447篇
金属工艺   237篇
机械仪表   329篇
建筑科学   128篇
矿业工程   2篇
能源动力   274篇
轻工业   1010篇
水利工程   24篇
石油天然气   13篇
无线电   1359篇
一般工业技术   1319篇
冶金工业   5635篇
原子能技术   89篇
自动化技术   811篇
  2023年   65篇
  2022年   103篇
  2021年   162篇
  2020年   94篇
  2019年   130篇
  2018年   173篇
  2017年   155篇
  2016年   202篇
  2015年   163篇
  2014年   245篇
  2013年   532篇
  2012年   387篇
  2011年   487篇
  2010年   329篇
  2009年   384篇
  2008年   329篇
  2007年   280篇
  2006年   234篇
  2005年   245篇
  2004年   176篇
  2003年   188篇
  2002年   171篇
  2001年   131篇
  2000年   135篇
  1999年   253篇
  1998年   1765篇
  1997年   993篇
  1996年   713篇
  1995年   456篇
  1994年   392篇
  1993年   419篇
  1992年   116篇
  1991年   156篇
  1990年   119篇
  1989年   141篇
  1988年   136篇
  1987年   130篇
  1986年   114篇
  1985年   78篇
  1984年   48篇
  1983年   51篇
  1982年   68篇
  1981年   61篇
  1980年   84篇
  1978年   55篇
  1977年   170篇
  1976年   375篇
  1975年   49篇
  1972年   33篇
  1971年   33篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The percentage of long-term survivors after intensive chemotherapy and the outcome of MDS patients who achieve partial remission (PR) with intensive chemotherapy (IC) are not known. Between 1981 and 1996 we treated 99 patients with de novo MDS who had high-risk MDS or progression to AML, with IC. 41 (41%) achieved CR, 16 (16%) achieved partial remission (PR), 26 (26%) had failure, and 16 (16%) died in aplasia. Eight of the patients who achieved CR were autografted, three were allografted and the remaining cases received moderate consolidation chemotherapy. After IC, the 16 PR patients fulfilled the criteria for RA in 15 cases and CMML in one case. Median PR duration was 17 months, and three PR were > 3 years (39, 50+, 82+ months). Median actuarial survival of patients who achieved PR and CR was 18 months and 20 months from the onset of IC, respectively (difference not significant). Of the 71 patients treated before 1993, with sufficient follow-up, 10 (14%) had survived > 4 years (long-term survivors). Four of them were alive in first CR after 49+ to 110+ months and probably cured, two were alive in PR after 50+ and 82+ months and four had died after 49-78 months. Long-term survivors were characterized by a significantly higher incidence of RAEB-T at diagnosis, and with normal or favourable cytogenetic findings. In patients with RAEB-T at diagnosis included before 1993, 8/23 (35%) cases who had no unfavourable karyotype had survived > 4 years. Our findings suggest that MDS patients who achieve PR with IC, and not only those who achieve CR, can benefit from this type of treatment. The percentage of long-term survivors remains low, however, and is almost restricted to patients with RAEB-T at diagnosis and no unfavourable karyotype.  相似文献   
22.
Carcinoma of the prostate, that is adenocarcinoma, is one of the most common malignancies in the male with an estimated incidence for 1991 of 122,000 new cases. On the other hand, squamous cell carcinoma of the prostate, with a median incidence of .5%-1% of all prostatic malignancies, has a similar clinical presentation but differs in treatment response and prognosis. We herein present one case of this histological pattern and review the literature pertaining to it.  相似文献   
23.
OBJECTIVES: To identify knowledge levels of academic surgeons about Food and Drug Administration (FDA) and Institutional Review Board (IRB) regulations for clinical research and to determine whether being a member in an IRB, conducting or participating in clinical trials, or being a member in surgical societies affected knowledge levels. DESIGN: Survey of surgical department faculty members in 20 universities. RESULTS: Sixty-five responses were received from 14 sites. Overall mean (+/- SEM) correct score was 6.7 +/- 0.2 of a possible 20 points. The best predictor of overall score was being a primary investigator of a clinical trial (P < .001), followed by being or having been a member of an IRB (P < or = .02). The total mean score of members of the Surgical Infection Society (8.2 +/- 0.5) was significantly higher (P < .001) than that of nonmembers (6.1 +/- 0.2), a phenomenon not observed with other surgical societies. In certain hypothetical clinical scenarios, all respondents were mistakenly willing to conduct clinical trials without obtaining appropriate approval from the FDA. Four (22%) of 18 IRB member respondents and 16 (25%) of the 65 respondents were willing to conduct human research without appropriate approval from patients, the IRB, or both. CONCLUSIONS: Knowledge deficits exist in the academic surgical community about the role and requirements of the FDA and local IRBs for conducting clinical research. Further study is required to determine the reasons for this deficit and to identify appropriate interventions.  相似文献   
24.
Fibrous dysplasia is an abnormal fibroosseous process of bone of unknown cause. The incidence of skull involvement varies, painless enlargement being the most common presenting symptom. Change in vision is a rare but recognized finding. We report a 3-year-old boy with extreme fibrous dysplasia involving the skull base, who presented with blindness. He underwent exposure osteotomies of the frontal bones and orbits to provide access for skull base tumor removal. The orbital roofs were reconstructed with microplate-fixed cranial grafts. One and one half years after tumor excision followed by immediate reconstruction, the boy retains facial symmetry, and his ocular function has not deteriorated.  相似文献   
25.
The aim of this study was to compare the sensitivities of commercial monoclonal antibody pools to be used as an initial rapid screen for detection of viral antigens in respiratory secretions. The availability of commercial monoclonal antibodies has dramatically improved the detection of viruses by immunofluorescence techniques in exfoliated cells obtained from respiratory secretions. Several companies have recently introduced monoclonal antibody pools to detect the presence of respiratory viruses in a single preparation. Ninety-four stored slide preparations that had previously been examined by individual monoclonal antibodies were tested using three commercial monoclonal antibody pools produced by Sanofi (UK), Dako (UK), and Quadratech (UK). These monoclonal antibody pools had a sensitivity of 79.6%, 90.9%, and 100%, respectively, when compared with the original results. The overall intensity of immunofluorescence was also examined.  相似文献   
26.
27.
28.
Transport properties of disordered continuum systems   总被引:1,自引:0,他引:1  
  相似文献   
29.
Wet adhesion is widely adopted in biological adhesion systems in nature. Wet adhesion is studied in this paper with the focus on the effect of different contact shapes (flat, concave, convex, and ring-like) on the adhesion force. The evolution of the liquid bridge between a fiber tip and substrate during the detaching process shows two transition points. The first transition from the radius-controlled to the contact-angle controlled process is critical to influence the strength and robustness of adhesion. We show that a concave shape is more effective than a flat one, while a convex shape has no advantage. A ring-like contact shape has advantages in a hydrophobic environment and on a rough surface.  相似文献   
30.
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