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   5777篇
  免费   257篇
  国内免费   21篇
电工技术   54篇
综合类   23篇
化学工业   1133篇
金属工艺   90篇
机械仪表   125篇
建筑科学   298篇
矿业工程   10篇
能源动力   228篇
轻工业   356篇
水利工程   56篇
石油天然气   31篇
无线电   514篇
一般工业技术   1164篇
冶金工业   835篇
原子能技术   49篇
自动化技术   1089篇
  2023年   56篇
  2022年   116篇
  2021年   183篇
  2020年   130篇
  2019年   174篇
  2018年   212篇
  2017年   136篇
  2016年   163篇
  2015年   134篇
  2014年   194篇
  2013年   351篇
  2012年   309篇
  2011年   346篇
  2010年   254篇
  2009年   262篇
  2008年   271篇
  2007年   275篇
  2006年   200篇
  2005年   193篇
  2004年   169篇
  2003年   171篇
  2002年   144篇
  2001年   85篇
  2000年   96篇
  1999年   71篇
  1998年   232篇
  1997年   157篇
  1996年   99篇
  1995年   107篇
  1994年   78篇
  1993年   71篇
  1992年   58篇
  1991年   45篇
  1990年   31篇
  1989年   32篇
  1988年   38篇
  1987年   34篇
  1986年   20篇
  1985年   29篇
  1984年   20篇
  1983年   16篇
  1982年   25篇
  1981年   29篇
  1980年   22篇
  1979年   21篇
  1978年   17篇
  1977年   26篇
  1976年   45篇
  1975年   14篇
  1972年   13篇
排序方式: 共有6055条查询结果,搜索用时 0 毫秒
1.
2.
Historical, high-resolution rain series are the backbone of modern combined sewer overflow (CSO) structure design. These rain series are the input to the computational estimation of the performance of the measures with respect to CSO pollution abatement. However, those historical precipitation measurements are available at only a few locations. Frequently rain series have to be used from gauging stations at a significant distance. In order to judge and to compensate for this influence an estimate between rain characteristics and combined sewer outflow (CSO) performance indicators would be useful. In this paper such correlations have been sought for a collection of 37 rain series covering large areas of Europe. It was found that the mean annual rain volume can explain most of the variances for the performance indicators Number of overflows and CSO volume. For explaining the spatial differences in the efficiency of the CSO structure another rain characteristic, i.e. the maximum event with a return period of one year, is to be used.  相似文献   
3.
4.
X-ray diffraction analysis shows that the transformation during heat treatment from amorphous to crystalline phases of bismuth-borate glass samples takes place in sequences. After a short heat treatment, 5 min at 550 °C, a layered structure with a preferred orientation of crystallites on the surface is observed. After a long heat treatment, 8 h at the same temperature, normal polycrystalline bulk samples are obtained.  相似文献   
5.
Rainwater can collect in a lens-shaped region within the rock of a tropical island, and may be separated from the underlying salt water by a sharp interface. This paper presents a nonlinear theory for determining the shape of this interface. The island is assumed to be saturated with rain, and provision is made for the outflow of rain-water through the sides of the island. The effect of a bore well on the shape of the interface is investigated, and the problem is solved using a spectral method. An integral-equation method is also presented for the case when the island has infinite width.  相似文献   
6.
This paper presents results of a research project, in which a process-dependent real-time control (RTC) strategy for a sequencing batch reactor plant was realised in full-scale. The cycle controller is based on NH4 analysers, NO3 probes, TSS probes and sludge level probes. With this new RTC strategy it was possible to increase the treatment capacity by 50%. By implementation of the new controller the TN, TP and NH4-N treatment efficiency could be improved significantly, too. The treatment efficiency concerning COD is comparable.  相似文献   
7.
This case study covers what is believed to be the world’s largest dry-running, non-contacting gas seal, manufactured by John Crane. Recently returned for routine maintenance, it has reached its five-year anniversary while remaining in excellent condition.  相似文献   
8.
Ileal pouch-anal anastomosis is a surgical procedure used for the treatment of people with chronic ulcerative colitis and familial adenomatous polyposis. The surgery is intended to preserve anal sphincter function, but it carries a risk for certain complications, including pouchitis and anastomotic stricture. The purpose of this article is to review the clinical manifestations, causes, and treatment of anastomotic stricture and pouchitis after ileal pouch-anal anastomosis.  相似文献   
9.
10.
We reviewed the cases of sixty-two patients who had had a subcutaneous sarcoma to determine the effect of tumor and treatment-related variables on the rates of survival and local recurrence. Fifty-nine (95 per cent) of the patients had had an operation at another hospital before being referred to us. Twenty-nine (47 per cent) of the sixty-two tumors were high-grade, forty-two (68 per cent) were small (five centimeters or less), and thirty (48 per cent) were malignant fibrous histiocytomas. We followed a treatment strategy that consisted of repeat excision with the goal of obtaining wide margins. Excluding thirteen patients who had had a palpable local recurrence at the time of presentation, twenty (49 per cent) of forty-one patients who had had a marginal excision at another hospital had microscopic residual tumor on repeat excision. At a median of fifty-six months after the repeat excision, fifty (81 per cent) of the sixty-two patients had been continuously disease-free, one had no evidence of disease, eight had died of the disease, and three had died of other causes. The five-year rate of disease-free survival was 85 per cent (fifty-three of sixty-two patients). There were three local recurrences, all in patients who had had a marginal resection. No recurrences were noted in patients who had had a wide local excision of the tumor or of the previous operative field. Multivariate analysis revealed that a large tumor (greater than five centimeters), a marginal excision, and adjuvant radiation therapy were associated with a worse prognosis. Excellent rates of survival for patients who have a subcutaneous sarcoma, including those who have a large or high-grade tumor and those who have residual tumor following a previous operation, can be obtained with carefully planned operative treatment alone. We recommend operative excision or repeat excision with wide margins because of the high prevalence of residual tumor. Size is the most important tumor-related factor, and the operative margin is the most important treatment-related factor. The additional value of adjuvant radiation therapy remains unproved.  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