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   3190篇
  免费   1篇
电工技术   4篇
化学工业   177篇
金属工艺   58篇
机械仪表   2篇
建筑科学   2篇
矿业工程   8篇
能源动力   2篇
轻工业   25篇
水利工程   1篇
石油天然气   4篇
无线电   26篇
一般工业技术   58篇
冶金工业   2792篇
原子能技术   4篇
自动化技术   28篇
  2013年   16篇
  2011年   7篇
  2010年   4篇
  2009年   7篇
  2008年   10篇
  2007年   6篇
  2006年   8篇
  2005年   6篇
  2004年   5篇
  2003年   9篇
  2002年   16篇
  2001年   4篇
  2000年   10篇
  1999年   82篇
  1998年   832篇
  1997年   486篇
  1996年   310篇
  1995年   161篇
  1994年   148篇
  1993年   189篇
  1992年   25篇
  1991年   38篇
  1990年   50篇
  1989年   50篇
  1988年   45篇
  1987年   38篇
  1986年   32篇
  1985年   27篇
  1984年   9篇
  1983年   8篇
  1982年   13篇
  1981年   20篇
  1980年   39篇
  1979年   8篇
  1978年   13篇
  1977年   85篇
  1976年   205篇
  1975年   18篇
  1974年   17篇
  1973年   21篇
  1972年   15篇
  1971年   14篇
  1970年   7篇
  1969年   7篇
  1968年   6篇
  1967年   6篇
  1966年   5篇
  1964年   4篇
  1926年   3篇
  1921年   5篇
排序方式: 共有3191条查询结果,搜索用时 31 毫秒
121.
Numerous complications and increased operating times were reported with ultrasonically assisted lipoplasty in the first several months after introduction of the technology in the United States. The purpose of this study was to review early reported complications and management regimens, evaluate possible causes of problems, and apply indications and techniques to attempt to minimize complications during an initial experience with this technique beginning in January of 1997. Seven specific indications and modifications of existing techniques were developed and applied to an initial clinical series of 70 consecutive patients who underwent ultrasound-assisted suction lipoplasty between January 10, 1997, and August 1, 1997. Follow-up ranged from 1 to 7 months. No perioperative or postoperative complication occurred in any patient in this series. In this series of ultrasound-assisted lipoplasty cases, application of the following criteria resulted in a series of 70 patients with 1 to 7-month follow-up without complications: (1) selecting patients with well localized fat deposits who were no more than 20 percent above their ideal body weight; (2) infusing a solution of Ringer's Lactate containing 1 cc of 1:1000 epinephrine per 1000 cc into the area of fat removal, stopping infusion when the tissues first become firm, not infusing to marked tissue turgor or skin induration; (3) restricting the level of energy application to a minimum of 1 cm from the undersurface of the dermis; (4) limiting ultrasonic energy application in each area to approximately 1 minute per estimated 100 cc of total aspirate in a wet to superwet environment; (5) not performing ultrasound-assisted lipoplasty in the same area as another procedure that could potentially compromise tissue vascularity; (6) using a Lysonix 2000 generator and 5-mm golf tee tip probe at a power setting of 8 to apply ultrasonic energy to the area of fat removal, ceasing energy application when tissue resistance to the passage of the probe decreases and moving the cannula as rapidly as tissue resistance allows; and (7) using a standard elastic garment without adherent foam or other materials for 2 weeks postoperatively, encouraging all normal activity immediately, and restricting aerobic activities for 2 weeks.  相似文献   
122.
Stroke is the third leading cause of death in the United States. Carotid artery stenting is being investigated as a therapeutic strategy for the management of extracranial bifurcation stenosis and has the potential to prevent stroke in thousands of patients. Carotid endarterectomy, although effective, does have limitations, and percutaneous techniques may offer an alternative method of treatment, especially for those who are at highest risk. Although the technique is still evolving, this article describes the protocol and technique of stent-supported carotid angioplasty and care for patients undergoing this procedure at Washington Adventist Hospital in Takoma Park, MD.  相似文献   
123.
A method for calculating and predicting the coefficients of thermal conductivity and viscosity of pure substances and two- or multicomponent mixtures has been developed on the basis of the single-parameter law of the corresponding states.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 55, No. 4, pp. 620–624, October, 1988.  相似文献   
124.
The changes in the serum level of selenium in cases with pathologic pregnancies are still not clear. The aim of the present study was to determine whether serum selenium in cases with missed abortion differed from selenium concentration in serum during first trimester of normal pregnancy. Twenty-three women with missed abortion and 61 with normal pregnancy were included in the study. We found a statistically significant (p < 0.001) elevation of serum selenium level in cases with missed abortion (928 +/- 335 nmol/l) comparing with those with normal pregnancy (568 +/- 77 nmol/l). We discuss the possible mechanisms of the observed changes.  相似文献   
125.
126.
Over the past few years, there has been an increasing interest in making oligonucleotides specific for ammonia-oxidizing bacteria (AOB), in order to detect and monitor these slow growing bacteria in environmental samples, in enrichment cultures and in wastewater treatment plants. Based on 16S rDNA sequences, a broad selection of oligonucleotides have been designed, either encompassing all known AOB in the beta-subgroup of the Proteobacteria (beta AOB), or subclasses within beta AOB. Thirty different oligonucleotides have so far been published, with varying specificity. The first AOB-specific oligonucleotides published were obtained as a result of an alignment of only eleven 16S rDNA sequences from AOB. Including the present study, there are now forty nearly full length 16S rDNA sequences available from these bacteria, in addition to a number of partial sequences, so that an improved evaluation of the published oligonucleotides can be done. Two new 16S rRNA gene sequences from Nitrosospira are presented here, in a phylogenetic analysis containing every 16S rRNA gene sequences (> 1 kb) available from AOB. On the basis of an alignment of all these sequences, combined with searches in the nucleotide sequence databases, an evaluation of the thirty published oligonucleotides is presented. The analysis expose the strength and weakness of each oligonucleotide and discuss the use of oligonucleotides specific for 16S rRNA genes in future studies of AOB. The present work also identifies one new, broad range primer, specific for the AOB in the beta-subgroup of the Proteobacteria.  相似文献   
127.
128.
129.
Congenital dislocation of the knee is a uncommon malformation. Frequently there is an association with other congenital deformities including congenital dislocation of the hip. The classification of Leveuf and Pais into three separate groups (Type A, Type B, Type C) is now widely accepted. Between October 1989 and April 1995 we evaluated ten children (five girls and five boys) with twelve dislocated knees. Clinical, radiographic and different ultrasonography examinations were carried out on both knees. The sonographic classification showed Type A in 3, Type B in 5 and Type C in 4 cases. The sonographic examination revealed the essential anatomic structures and their pathomorphology. The anterior and the posterior cruciate ligament could be demonstrated in the majority of the cases. Three dislocated knees showed an obliteration of the recessus suprapatellaris and fibrotic changes in the m. quadriceps. These cases required operative treatment. With conservative treatment we achieved a satisfactory result in eight children with nine disease knees. There was a good functional result with an average flexion of 106 degrees. Early conservative treatment recommend as the therapy of choice. Ultrasonography imaging offers the possibility of reliable differentiation into one of the three groups of the classification of Leveuf and Pais. Radiographic documentation during the therapy has become the exception. Ultrasonography imaging helped substantially in the decision making and the timing of operative treatment.  相似文献   
130.
For ultrasonographic B-scan images collected by means of a handheld transducer moving in the elevational direction, frame spacings are computed with a speckle-decorrelation algorithm, without additional positioning hardware. Fully developed speckle volumes are automatically segmented and spacing computed from the decorrelation curves. Position accuracy is within 10% for phantoms and 15% for breast studies. The algorithm provides image-based registration, which allows accurate three-dimensional volume rendering.  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