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   1459篇
  免费   12篇
  国内免费   1篇
电工技术   5篇
化学工业   44篇
金属工艺   7篇
机械仪表   15篇
建筑科学   7篇
能源动力   13篇
轻工业   57篇
水利工程   3篇
无线电   19篇
一般工业技术   66篇
冶金工业   1198篇
原子能技术   1篇
自动化技术   37篇
  2023年   2篇
  2022年   5篇
  2021年   4篇
  2020年   5篇
  2019年   4篇
  2018年   8篇
  2017年   5篇
  2016年   5篇
  2015年   5篇
  2014年   9篇
  2013年   30篇
  2012年   15篇
  2011年   18篇
  2010年   16篇
  2009年   12篇
  2008年   20篇
  2007年   6篇
  2006年   3篇
  2005年   5篇
  2004年   4篇
  2003年   10篇
  2002年   9篇
  2000年   7篇
  1999年   35篇
  1998年   376篇
  1997年   174篇
  1996年   136篇
  1995年   76篇
  1994年   53篇
  1993年   83篇
  1992年   10篇
  1991年   18篇
  1990年   16篇
  1989年   13篇
  1988年   14篇
  1987年   11篇
  1986年   14篇
  1985年   18篇
  1984年   5篇
  1983年   6篇
  1982年   6篇
  1981年   8篇
  1980年   16篇
  1979年   5篇
  1978年   8篇
  1977年   51篇
  1976年   106篇
  1975年   2篇
  1965年   2篇
  1955年   1篇
排序方式: 共有1472条查询结果,搜索用时 0 毫秒
61.
62.
A case of pulmonary Mycobacterium avium (M. avium) disease associated with idiopathic CD4+ T lymphocytopenia is reported. A rapidly growing pulmonary nodule was detected on a chest roentgenogram in a young man. Bronchoscopic examination revealed M. avium infection. Hematological studies showed a low CD4+ cell count in the absence of any identifiable immunodeficiency, including human immunodeficiency virus (HIV) infection. With the combination of chemotherapy and surgery, he had a good clinical outcome. Idiopathic CD4+ T lymphocytopenia should be considered in patients with unexplained opportunistic infection.  相似文献   
63.
Flow rates (W) of powder and granules are usually measured by letting the particulate solid pass through a stationary orifice. This is not a physical duplication of the event in, for instance, a rotary tablet machine, where the dies move in relation to the powder bed. An apparatus is described by which dynamic flow rates (i.e. flow into a moving orifice) can be measured. These dynamic flow rates (W2 g/sec) differ from static flow rates. They are subject to the same dependence on particle diameter, d, as static flow rate, i.e.: W2 ? Wm = ? k(d ? dm)s, where “m” refers to maximum and k and s are constants. They also exhibit the same type dependence on orifice opening (P cm) as static flow rates, i.e.W2 = qPn, where q and n are constants. The values for n are 3 – 3.25, which is somewhat higher than for static flow where n = 2.3 – 2.6.  相似文献   
64.
The primary goal in the medical management of ventricular septal defect complicating myocardial infarction is to support cardiac function and control symptoms, if possible, for a period of 4 to 6 weeks. If the patient survives this period, surgical correction of the defect is technically easier and safer. In many cases, However, cardiac function is severly compromised, intractable biventricular failure develops,early operation is necessary and the likelihood of successful repair is diminished.  相似文献   
65.
All of 16 infants with neonatal meningitis treated during a 30-month period were found to have accompanying ventriculitis at the time of the initial ventricular puncture. Fifteen of these infants were caused by gramm-negative organisms. All infants received antibiotics systemically and intraventricularly via an implanted ventriculostomy reservoir or by direct ventricular injection. Antibiotic concentrations within the ventricular fluid were monitored during chemotherapy; the complications encountered during treatment are discussed. Fifteen infants survived the infection; of these, seven infants were normal at follow-up examinations. In our experience intraventricular chemotherapy as an adjunct to systemic administration of antibiotics has greatly reduced the mortality rate in neonatal meningitis.  相似文献   
66.
Fecal neutral steroids and bile acids were measured in patients with familial polyposis, family controls who are immediate relatives of patients, and controls other than relatives. All subjects were consuming a mixed Western diet at the time of collection of stool specimens. Although the total fecal neutral sterol concentrations were not different between the groups, the patients with familial polyposis excreted a high amount of cholesterol and low levels of coprostanol and coprostanone compared with other groups. Patients with familial polyposis excreted levels of total bile acids in their feces comparable to those excreted by controls; lithocholic acid excretion was decreased in patients with familial polyposis. These findings suggest that analysis of stools for cholesterol and its metabolites be useful in screening the siblings of polyposis families for latent disease.  相似文献   
67.
Malignant melanoma of the mucous membranes is rare and has a very poor prognosis. When localized in the nose, the tumor becomes apparent late in the course of the disease with nasal obstruction and epistaxis. Distant metastases are uncommon, but any organ of the body can be involved. A case of a malignant melanoma of the nasal mucosa with metastasis to the small intestine is presented, and the natural history of the metastatic disease is discussed.  相似文献   
68.
Analysis of measurements from the tali of 21 individual fossil primates from Africa shows that the specimens fall into five clearly defined groups. Accordingly, these specimens have been included as groups along with extant species in a subsequent canonical analysis thus allowing the fossils to play their part in the determination of the canonical separations. The results of this procedure show that the five fossil groups lie in a part of the canonical space not occupied by any extant African primate. Their positions are between the envelope of Asiatic apes (Hylobates and Pongo) and the envelope of African forms near the edge which contains Pan and Papio. One fossil group is so similar to Hylobates that its talus may have functioned in locomotion in a parallel manner. Others lie near to Pongo in directions proceeding towards Pan and Papio and it is possible that this similarity may indicate remnants of morphological adaptation for climbing in these fossils. At the same time, however, individual specimens are closer to one or another of the extant groups and this considerable spread suggests that the locomotor adaptations as evidenced by talar morphology, of the primate fauna in Africa, may have been very different from those of the present day. This would not the inconsistent with the different habitats, floras and non-primate faunas that may have characterized the East African scene at these earlier times. Particular fossils from Olduvai and Kromdraai that are supposed to be australopithecine and therefore bipeds, are confirmed (Oxnard, '72; Lisowski et al., '74) as being totally different from man in their talar morphology and essentially rather similar to the majority of the other fossil tali examined.  相似文献   
69.
70.
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