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   2336篇
  免费   12篇
  国内免费   3篇
电工技术   12篇
化学工业   85篇
金属工艺   10篇
机械仪表   25篇
建筑科学   33篇
能源动力   14篇
轻工业   49篇
水利工程   2篇
石油天然气   3篇
无线电   59篇
一般工业技术   187篇
冶金工业   1740篇
原子能技术   12篇
自动化技术   120篇
  2021年   5篇
  2020年   3篇
  2019年   5篇
  2018年   9篇
  2017年   5篇
  2016年   4篇
  2015年   12篇
  2014年   7篇
  2013年   48篇
  2012年   24篇
  2011年   23篇
  2010年   26篇
  2009年   26篇
  2008年   29篇
  2007年   32篇
  2006年   30篇
  2005年   27篇
  2004年   18篇
  2003年   29篇
  2002年   14篇
  2001年   21篇
  2000年   14篇
  1999年   50篇
  1998年   544篇
  1997年   323篇
  1996年   213篇
  1995年   118篇
  1994年   102篇
  1993年   113篇
  1992年   21篇
  1991年   32篇
  1990年   29篇
  1989年   25篇
  1988年   24篇
  1987年   36篇
  1986年   25篇
  1985年   23篇
  1984年   8篇
  1983年   4篇
  1982年   14篇
  1981年   28篇
  1980年   19篇
  1979年   8篇
  1978年   13篇
  1977年   37篇
  1976年   89篇
  1975年   7篇
  1974年   7篇
  1973年   6篇
  1972年   4篇
排序方式: 共有2351条查询结果,搜索用时 31 毫秒
1.
Two groups of Brangus steers produced by nuclear transplantation cloning were used in parallel studies investigating the impact of calf- and yearling-feeding. The first group (n = 8) were fed as calves (CF; n = 4) or yearlings (YF; n = 4) to a constant age end point of 16 mo. The second group (n = 10) were fed as calves (CF; n = 5) or yearlings (YF; n = 5) to a constant live weight end point (530 kg). When slaughtered at the same age, CF and YF steers did not differ (P > .05) in feedlot ADG, but the CF steers were heavier and had higher dressing percentages, numeric yield grades, and quality grades (P < .05). Top loin steaks from the groups of steers did not differ (P > .05) in palatability traits. When fed to a constant live weight, the YF steers gained more rapidly (P < .05) and had lower (P < .05) numeric yield grades than did CF steers. Again CF steers had higher (P < .05) dressing percentages. There was no difference (P > .05) between the treatments in carcass quality grade or meat palatability characteristics. Thus, when finished to a constant weight end point, YF steers gained more rapidly, with no adverse effects on carcass quality grade or palatability traits; however, CF steers consistently produced higher dressing percentages, largely due to greater external fatness.  相似文献   
2.
3.
SB McNeil 《Canadian Metallurgical Quarterly》1997,23(3):287-8; discussion 289-90, 317
Jehovah's Witnesses refuse blood transfusions for themselves and for their children. This action can be difficult for health professionals to understand and can lead to tensions between the staff and family. For one family, their refusal of blood for their child lead to a greater understanding of their religion and its beliefs for those who cared for them. Interspersed with their story are the medical reasons their son required blood, the reasons Jehovah's Witnesses refuse blood transfusions, and what the acceptable alternatives are to Jehovah's Witnesses. This article will share the thoughts and feelings of the family and the nursing staff who cared for the family during this crisis.  相似文献   
4.
5.
Fetus-in-fetu is an unusual condition in which a vertebrate fetus is enclosed within the abdomen of another fetus. These occurrences are usually benign. This report describes an instance of malignant recurrence after resection of a fetus-in-fetu.  相似文献   
6.
The majority of patients with soft tissue or bone sarcomas of the upper extremity can be treated today with limb-saving procedures using combined modality therapies. For patients with a tumor in the shoulder area, sometimes an interscapulothoracic amputation is the only radical surgical treatment. However, in selected cases, in which the tumor does not involve the neurovascular bundle, a limb-sparing alternative might be the Tikhoff-Linberg resection. Normal function of the hand and forearm, with reasonable function of the elbow, can be maintained by this procedure. Four case histories are reported.  相似文献   
7.
At the present time, somatic and male-specific coliphage and human enterovirus groups are being considered as indicators of possible pathogenic human enteric virus contamination from fecal contamination. A primary attribute for any indicator of fecal contamination is its prevalence at the source and in associated ground water. It must be consistently found in the source material at concentrations that are measurable with available techniques. Over a period of ten months, male-specific and somatic coliphage ranged from 7000 to 4,000,000 PFU/L in the effluent from a multi-user septic-tank. Unlike the values determined for septic-tank effluent, coliphage concentrations measured in ground water over this same period only varied by five-fold. Coliphage concentration in ground water under the down-gradient edge of the drainfield contained 1000 PFU/L. This concentration decreased at −1 log10/5 m during 17.4 m of ground-water transport. From these data, coliphage concentrations in septic-tank effluent seem sufficient to allow their use as indicators of fecal contamination in ground water.  相似文献   
8.
9.
PURPOSE: To assess long-term survival following cladribine salvage treatment for previously treated patients with chronic lymphocytic leukemia. PATIENTS AND METHODS: Fifty-two patients aged 39-84 years with previously treated CLL received cladribine 0.12 mg/kg/day in 2-hour infusions for 5 days in monthly courses. Two-thirds were refractory to previous therapy, and 8 had prior fludarabine. RESULTS: Sixteen (31%) patients achieved complete response (CR) and 14 (27%) partial remission (PR) according to consensus criteria. Response correlated with clinical stage, number of previous treatment regimes, blood lymphocyte count, and lymphocyte halflife following the first cladribine course. Toxicity included pneumonia (n = 9), herpes zoster (n = 7), and septicemia (n = 2). Four patients in CR underwent high-dose chemotherapy with autologous blood stem cell support, and 2 remain in CR 48 and 60 months from start of cladribine, and 2 had relapse at 42 and 48 months, respectively. Median progression-free survival (Kaplan-Meier analysis) for CR patients was 23 months from start of cladribine treatment, and for PR patients 16 months. The projected overall survival was 80% at 3 years for CR patients, and the median survival 28 months for PR patients and 4 months for non-responding patients. CONCLUSIONS: Our previous finding of durable CRs from cladribine in advanced CLL is thus confirmed in a larger patient material, and follow-up indicate that long-term survival may be achieved.  相似文献   
10.
Socially amoral economic forces now drive health system change. The authors, assisted by a panel of experts on employers, health plans, providers, and consumers, discuss current drivers such as (1) employers' price-focused purchasing, without good quality/value measures; (2) health plans' growing successes and market clout; (3) providers declining prospects and fears about their future; and (4) consumers' worries about less choice. Future influences will include Medicare reforms, better information, and pro-consumer regulation of managed care, as well as rising social distress. The health system's future is now open for resolution in an evolving, imperfect market.  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