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   1117篇
  免费   3篇
  国内免费   2篇
电工技术   5篇
化学工业   16篇
金属工艺   1篇
机械仪表   7篇
建筑科学   3篇
能源动力   6篇
轻工业   6篇
石油天然气   5篇
无线电   11篇
一般工业技术   3篇
冶金工业   1036篇
自动化技术   23篇
  2023年   2篇
  2022年   5篇
  2021年   2篇
  2020年   2篇
  2019年   5篇
  2018年   6篇
  2017年   6篇
  2016年   5篇
  2015年   2篇
  2014年   8篇
  2013年   11篇
  2011年   4篇
  2010年   11篇
  2009年   10篇
  2008年   2篇
  2007年   1篇
  2006年   1篇
  2005年   3篇
  2004年   1篇
  2003年   2篇
  1999年   18篇
  1998年   307篇
  1997年   204篇
  1996年   117篇
  1995年   68篇
  1994年   59篇
  1993年   54篇
  1992年   7篇
  1991年   15篇
  1990年   8篇
  1989年   9篇
  1988年   19篇
  1987年   13篇
  1986年   8篇
  1985年   8篇
  1983年   2篇
  1982年   6篇
  1981年   8篇
  1980年   7篇
  1978年   7篇
  1977年   28篇
  1976年   59篇
  1975年   1篇
  1954年   1篇
排序方式: 共有1122条查询结果,搜索用时 15 毫秒
81.
82.
The functional significance of the developmental transition from slow skeletal troponin I (ssTnI) to cardiac TnI (cTnI) isoform expression in cardiac myocytes remains unclear. We show here the effects of adenovirus-mediated ssTnI gene transfer on myofilament structure and function in adult cardiac myocytes in primary culture. Gene transfer resulted in the rapid, uniform, and nearly complete replacement of endogenous cTnI with the ssTnI isoform with no detected changes in sarcomeric ultrastructure, or in the isoforms and stoichiometry of other myofilament proteins compared with control myocytes over 7 days in primary culture. In functional studies on permeabilized single cardiac myocytes, the threshold for Ca2+-activated contraction was significantly lowered in adult cardiac myocytes expressing ssTnI relative to control values. The tension-Ca2+ relationship was unchanged from controls in primary cultures of cardiac myocytes treated with adenovirus containing the adult cardiac troponin T (TnT) or cTnI cDNAs. These results indicate that changes in Ca2+ activation of tension in ssTnI-expressing cardiac myocytes were isoform-specific, and not due to nonspecific functional changes resulting from overexpression of a myofilament protein. Further, Ca2+-activated tension development was enhanced in cardiac myocytes expressing ssTnI compared with control values under conditions mimicking the acidosis found during myocardial ischemia. These results show that ssTnI enhances contractile sensitivity to Ca2+ activation under physiological and acidic pH conditions in adult rat cardiac myocytes, and demonstrate the utility of adenovirus vectors for rapid and efficient genetic modification of the cardiac myofilament for structure/function studies in cardiac myocytes.  相似文献   
83.
Methanolic extracts prepared from the leaves of Lantana camara have been found to inhibit human thrombin. An assay, in which thrombin activity is measured as a function of clot formation from fibrinogen, was used to guide the fractionation and purification of five principal active constituents (1-5), which were all characterized as 5,5-trans-fused cyclic lactone-containing euphane triterpenes.  相似文献   
84.
BACKGROUND: Although a compulsory examination in medical English has been present in the medical degree curriculum in Italy since 1990, guidelines indicating what should be learnt and suggesting some means of overcoming the various problems this entails are still lacking. OBJECTIVE: To investigate the main features of teaching English in the Medical Faculties and enquire into how the various problems are solved in the individual English teaching units. METHOD: A questionnaire addressing the above issues was sent out to all the Italian Universities with a Medical Faculty. RESULTS: The first finding of our survey was that response was very poor: less than 30% of the survey volunteered any reply. Within the very reduced sample which responded, there was a high degree of variation among the solutions adopted, although the underlying problems were perceived to be much the same throughout Italy. CONCLUSIONS: The general objective of the English course for medicine should be more precisely defined, together with a series of specific minimum skills the student should possess to pass the final examination. A closer collaboration among the English teaching units might help to standardize these requirements, improve the quality of the teaching and hence the level of proficiency in English for the specific purpose of medical practice.  相似文献   
85.
Although continuous axillary block is effective for periods of up to four to six weeks, pain clinic patients with severe chronic pain in the upper extremities, mainly resulting from neuropathic disease, can require continuous drug delivery by catheter-reservoir for up to three months or longer. We studied possible locations for implanting reservoirs or catheters from the perivascular axillary space in fresh cadavers, checking for possible vascular or nerve damage after applying the usual technique for reservoir implantation. The ideal location for the reservoir is the subcutaneous tissue of the homolateral infraclavicular space of the anterior side of the thorax. The customary procedures for inserting the catheter along the subcutaneous route that extends from the perivascular axillary space to the reservoir carry no risk of damaging vascular or nerve structures.  相似文献   
86.
1% acetylcholine (5.5 10 M--acetylcholine chloride) applied directly to the cortex of conscious non-immobilized rabbits was established to produce neuroglial reaction in motor area. Following 30 min long application the number of astrocytes was significantly increased. Application lasting for 2 hrs resulted in a reverse effect. The above-mentioned changes were observed in surface and deep cortical layers. They were functional and could be attributed to the cell tinctorial properties.  相似文献   
87.
A case of a 66 years old patient suffering from a sigmoido-vaginal fistula and diverticulosis, previously treated with a total laparohysterectomy, is reported. Retrograde studies demonstrated the presence of fistula, whereas colonoscopy and barium enema failed. After laparotomy and an appropriate bowel preparation, surgery was restricted to the bowel resection and anastomosis, whereas the vaginal defect was not closed.  相似文献   
88.
Presynaptic paired-pulse facilitation (PPF) rate decreased in most CA1 pyramidal neurones following the long-term potantiation (LTP) induction. The decrease correlated with the LTP magnitude as well as with the initial (pretetanic) PPF rate. The data obtained suggests an involvement of presynaptic mechanisms in maintaining the early and the delayed LTPs.  相似文献   
89.
During a 9 month period, 50 consecutive children were evaluated by ultrasound to determine the size, location (mesenteric vs para-aortic), number, shape and texture of abdominal lymph nodes in a normal paediatric population. High resolution linear array transducers were used with graded compression. Nodes ranging from 10 to 20 mm were recorded in the majority of subjects. In all cases mesenteric lymph nodes were larger and more numerous than para-aortic nodes. Para-aortic lymph nodes were not seen in isolation.  相似文献   
90.
Polymeric films were deposited from hydroxyethylmethacrylate (HEMA) plasma on non-woven poly(butyleneterephtalate) (PBT) filter materials. To test the effect of deposition conditions on surface properties, film were deposited using a constant monomer flow rate and a discharge power ranging from 40-100 W. Surface composition and surface energetics were evaluated by Electron Spectroscopy for Chemical Analysis (ESCA) and contact angle measurement, respectively. Albumin (Alb) and fibrinogen (Fg) adsorption from single protein solutions to the plasma-coated filters was measured. Results illustrate the marked effects of the deposition condition on the surface composition, the surface field of forces, and the protein adsorption behavior. The latter is modeled by the application of the Good-van Oss-Chaudhury theory of Lewis acid-base contribution to interfacial energetics. Materials endowed with widely different properties are obtained from the same monomer and different deposition conditions, a result that must be taken into account both in the production step, to assure constant quality, and in the development of specifically tailored materials.  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