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   3344篇
  免费   159篇
  国内免费   3篇
电工技术   35篇
综合类   2篇
化学工业   560篇
金属工艺   52篇
机械仪表   58篇
建筑科学   66篇
矿业工程   1篇
能源动力   69篇
轻工业   378篇
水利工程   21篇
石油天然气   16篇
无线电   137篇
一般工业技术   412篇
冶金工业   1457篇
原子能技术   12篇
自动化技术   230篇
  2024年   4篇
  2023年   13篇
  2022年   31篇
  2021年   75篇
  2020年   52篇
  2019年   73篇
  2018年   64篇
  2017年   85篇
  2016年   81篇
  2015年   62篇
  2014年   100篇
  2013年   135篇
  2012年   98篇
  2011年   149篇
  2010年   101篇
  2009年   125篇
  2008年   101篇
  2007年   96篇
  2006年   69篇
  2005年   59篇
  2004年   64篇
  2003年   56篇
  2002年   44篇
  2001年   34篇
  2000年   51篇
  1999年   58篇
  1998年   453篇
  1997年   283篇
  1996年   191篇
  1995年   115篇
  1994年   81篇
  1993年   102篇
  1992年   36篇
  1991年   26篇
  1990年   33篇
  1989年   31篇
  1988年   26篇
  1987年   24篇
  1986年   21篇
  1985年   13篇
  1984年   8篇
  1983年   10篇
  1982年   10篇
  1981年   11篇
  1980年   21篇
  1979年   3篇
  1978年   7篇
  1977年   35篇
  1976年   77篇
  1975年   3篇
排序方式: 共有3506条查询结果,搜索用时 15 毫秒
41.
Femoral artery pseudoaneurysms (PSA or false aneurysm) develop in about 1% of patients undergoing procedures that require femoral artery cannulation. PSA prolong hospitalization, consuming health-care resources, and result in significant morbidity. We designed a study to review the prevalence, risk factors, and treatment of PSA. We performed a retrospective, case-controlled study of patients diagnosed with PSA at a large, urban, tertiary-care teaching hospital. We reviewed 48 patients with PSA for our study. The estimated prevalence of PSA was 0.28%, with identical rates found for procedures done in the interventional radiology department and in the cardiac catheterization suite. Logistic regression identified three independent risk factors for developing PSA: being female (odds ratio 2.62), having an intervention performed (odds ratio 3.22), and not having a closure device used (odds ratio 10.2). Patients with PSA had longer hospital length of stay than that of patients without PSA. We found no statistically significant difference in failure or complication rates for the four treatment options and that spontaneous resolution of PSA does not correlate with its size. Thrombin injection and observation are effective, low-complication treatment options.  相似文献   
42.
This paper analyzes a system subject to repairable and non-repairable failures. Non-repairable failures lead to replacement of the system. Repairable failures, first lead to repair but they lead to replacement after a fixed number of repairs. Operating and repair times follow phase type distributions (PH-distributions) and the pattern of the operating times is modelled by a geometric process. In this context, the problem is to find the optimal number of repairs, which maximizes the long-run average reward per unit time. To this end, the optimal number is determined and it is obtained by efficient numerical procedures.  相似文献   
43.
The attributes of an orthorhombic Ti aluminide alloy, Ti-21Al-22Nb (at. pct), and an alpha-two Ti aluminide alloy, Ti-24Al-11Nb (at. pct), for use as a matrix with continuous SiC (SCS-6) fiber reinforcement have been compared. Foil-fiber-foil processing was used to produce both unreinforced (“neat”) and unidirectional “SCS-6” reinforced panels. Microstructure of the Ti-24A1-11Nb matrix consisted of ordered Ti3Al (α 2) + disordered beta(β), while the Ti-21 Al-22Nb matrix contained three phases: α2, ordered beta (β 0), and ordered orthorhombic(O). Fiber/ matrix interface reaction zone growth kinetics at 982 °C were examined for each composite system. Although both systems exhibited similar interface reaction products(i.e., mixed Ti carbides, silicides, and Ti-Al carbides), growth kinetics in theα 2 +β matrix composite were much more rapid than in theO +β 0 +α 2 matrix composite. Additionally, interfacial reaction in theα 2 +β} composite resulted in a relatively large brittle matrix zone, depleted of beta phase, which was not present in theO +β 0+α 2 matrix composite. Mechanical property measurements included room and elevated temperature tensile, thermal stability, thermal fatigue, thermo-mechanical fatigue (TMF), and creep. The three-phase orthorhombic-based alloy outperformed the α2+β alloy in all of these mechanical behavioral areas, on both an absolute and a specific(i.e., density corrected) basis.  相似文献   
44.
45.
We prove several results concerning problems invariant under the action of an arbitrary compact Lie group Γ. These include the existence of mixed-mode solutions and secondary Hopf bifurcations. We provide a definition of mode interaction which applies to a wide selection of problems and consider the unfolding of the equations characterizing such problems. Where appropriate, we distinguish the case when I acts trivially on one of the modes  相似文献   
46.
The density of HCFC 141b has been measured at several temperatures between 260 and 320 K, Mid pressures up to 20 MPa, with a mechanical oscillator densimeter. The densimeter was calibrated with 2,2,4-trimethylpentane, whose density was obtained from a correlating cyuation with 0.3% uncertainty. The density data obtained for HCFC 14H) hits a reproducibility of 0.05% and an uncertainty of 0.3%. The data obtained were fitted to a Tait-type equation. which reproduced the experimental densities within 0.11 % and were compared with the data obtained in other works.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.  相似文献   
47.
PURPOSE: To determine the frequency and nature of hepatic toxicity associated with fluorouracil (5-FU) plus levamisole adjuvant therapy. PATIENTS AND METHODS: All patients had resection of stage II or stage III colon cancer and were randomized to receive observation only, levamisole alone, or 5-FU plus levamisole. Serial liver function studies were documented in 1,025 patients who did not develop recurrence during the year of therapy. RESULTS: One hundred forty-nine (39.6%) of 376 patients treated with 5-FU plus levamisole showed laboratory abnormalities consistent with hepatic toxicity, compared with 16.3% of 251 patients treated with levamisole alone and 16.1% of 398 untreated controls. Most common was elevation of alkaline phosphatase, frequently accompanied by elevations of transaminase or serum bilirubin. Characteristically, these changes were mild, not associated with symptoms, and resolved when therapy was stopped. In some instances, they were associated with elevated carcinoembryonic antigen (CEA) tests or with fatty liver seen on computed tomographic (CT) scan or liver biopsy. CONCLUSION: Mild and reversible hepatotoxicity is a common consequence of 5-FU plus levamisole adjuvant therapy, but this is only rarely symptomatic. However, the oncologist should be alert to this phenomenon, since the associated laboratory and imaging findings may simulate those associated with hepatic metastasis.  相似文献   
48.
In a 63-year-old woman with longstanding type I diabetes mellitus, CAD and chronic heart failure, a subacute myocardial infarction developed, together with decompensation of cardiac function and diabetes and concurrent pneumonia. Acute heart failure with acute renal failure on top of diabetic nephropathy, and interstitial pulmonary edema was initially treated with hemofiltration and catechol amines together with antibiotic and perfusor-regulated insulin therapy, and systemic heparinization. Subsequent chronic treatment with digitalis, acetyl salicylic acid, insulin and a combination of an ACE inhibitor and a loop diuretic resulted in an improvement of heart failure to NYHA functional class II where PTCA of coronary multi-vessel disease could be performed with low risk.  相似文献   
49.
50.
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