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   2359篇
  免费   0篇
  国内免费   1篇
化学工业   5篇
金属工艺   1篇
建筑科学   1篇
矿业工程   1篇
水利工程   1篇
石油天然气   1篇
无线电   1篇
一般工业技术   3篇
冶金工业   2346篇
  2013年   1篇
  2011年   1篇
  2010年   1篇
  2007年   1篇
  2003年   3篇
  2001年   1篇
  1999年   70篇
  1998年   654篇
  1997年   386篇
  1996年   292篇
  1995年   128篇
  1994年   113篇
  1993年   165篇
  1992年   19篇
  1991年   33篇
  1990年   31篇
  1989年   35篇
  1988年   24篇
  1987年   30篇
  1986年   33篇
  1985年   31篇
  1983年   4篇
  1982年   14篇
  1981年   25篇
  1980年   22篇
  1978年   8篇
  1977年   69篇
  1976年   157篇
  1975年   3篇
  1974年   1篇
  1965年   1篇
  1964年   1篇
  1959年   1篇
  1955年   2篇
排序方式: 共有2360条查询结果,搜索用时 15 毫秒
1.
PURPOSE: In an experimental pyogenic liver abscess model, the signal intensities were compared intraindividually and interindividually after the application of a new blood pool contrast agent, 24-gadolinium-DTPA (diethylenetriamine-pentaacetic acid) cascade polymer, and after the application of gadopentetate dimeglumine. METHODS: In 20 rabbits with experimentally induced liver abscesses, the relative signal intensities of the liver, abscess centre, abscess wall and portal vein were assessed before and between 30 seconds and 60 minutes after injection of a 25 mumol/kg dose of gadolinium polymer and of 100 mumol/kg of gadolinium-DTPA, respectively. Measurements were performed at 1.5 Tesla, using a head coil and a Flash-2-D sequence. RESULTS: The interindividual comparison (unpaired T-test, p < 0.05) yielded significant differences of the relative signal intensities of the abscess centre (at any time point after contrast-media application), abscess wall (between 15 and 60 minutes after contrast media application), and portal vein (between 30 seconds and 7.5 minutes after contrast media application). The interindividual comparison showed a significantly higher abscess centre-liver contrast (between 30 seconds and 12.5 minutes after contrast media application) and a significantly higher abscess wall-centre contrast (between two and 7.5 minutes after contrast media application) after the application of gadolinium polymer compared with gadopentetate dimeglumine. CONCLUSION: In this animal model, the higher abscess centre-liver contrast after the application of gadolinium polymer was the basis for a better and prolonged visibility of the abscesses, as compared with images acquired after injection of gadopentetate dimeglumine.  相似文献   
2.
3.
A myasthenic reaction developed after an average latency of seven to eight months in 12 female patients (average age 51 years) treated with penicillamine for chronic rheumatoid arthritis. In most of them only the purely ocular form was noted, but generalisation of various degrees also occurred. When penicillamine had been discontinued the myasthenic signs were almost always fully reversible, recurring once again when treatment with penicillamine was started. In some instances a transitory symptomatic treatment with cholinesterase inhibitors was necessary. The occurrence of the myasthenic signs in these circumstances is probably similar to the anti-basal membrane nephropathy induced by penicillamine.  相似文献   
4.
5.
Based on the hitherto published population data of the human red cell PGM1 and acid phosphatase polymorphisms, the geographical distributions of their gene frequencies were analyzed. As far as the acid phosphatase alleles are concerned, a marked geographical gradient was found as the Pa and Pb alleles showed significant correlations with the mean annual temperatures of the various human biotopes (Pa:r = -0.706; Pb:r = +0.812). Against that, the world distribution of the PGM1 alleles did not show a comparable correlation (PGM1 1:R = +0.063; PGM2 1:R = -0.063). The possible reasons for the distribution pattern of the acid phosphatase alleles are discussed.  相似文献   
6.
Rancinamycins are secondary metabolites produced by Streptomyces lincolnensis in a sulfur-depleted culture medium. The structures (except stereochemistry) of the main components of the rancinamycin-complex were determined by the use of IR, UV, PMR, and CMR spectra.  相似文献   
7.
When mammalian sperm cells are exposed to solutions of albumin there are changes in the membranes of some species that resemble those that normally occur in the uterus prior to fertilization. We have shown that albumin molecules absorb on to the membranes of ejaculated rabbit sperm cells, and that the equilibrium binding constant, K, (1) varies inversely with the albumin concentration, (2) is independent of the sperm cell concentration in the range of 10(6)--10(7) per ml, (3) is independent of the time of exposure of the sperm cells to the albumin solution, and (4) decreases in the presence of Ca++ and Mg++ ions. An unusual aspect of the adsorption is that if the albumin concentration is given the symbol [A], K[A] is a constant in our measurements. This means that for virtually the entire range of [A] studied, the sperm cells bind albumin so that half of the available surface is coated and half remains uncoated. This situation is rather remarkable and it suggests a role that adsorption could play in the physical processes preceding fertilization. In purely physical systems, the optimum for the bridging and flocculation of particles that are coated with adsorbed macromolecular films occurs when half of the available surface is covered. The sperm cell appears to provide the optimal situation for interacting with itself or with another surface.  相似文献   
8.
9.
Antibody against a breast carcinoma antigen was present in patients with breast carcinoma and other cancer more often (P less than .05) than in normal women. The incidence of antibody in women with breast carcinoma correlated with the presence or absence of gross tumor, and the titer of antibody paralleled the clinical course. These results suggest importance of a host-immune response to breast carcinoma. Fifty-seven patients with stage II carcinoma of the breast were entered into a prospective randomized adjuvant chemoimmunotherapy program of cyclophosphamide, methotrexate, and fluorouracil, and BCG vaccine +/- an irradiated allogeneic tumor cell vaccine. After 24 months of study, metastases occurred in two patients (3.5%) and a new primary carcinoma developed in the contralateral breast in two others, for an overall treatment failure rate of 7%. Adjuvant chemoimmunotherapy can delay early recurrence. Long-term follow-up is needed to assess the significance of these results.  相似文献   
10.
Infantile hypertrophic pyloric stenosis is best treated surgically, after an appropriate period of rehydration and resuscitation. Our experience with this entity has resulted in the performance of fewer contrast studies to establish the diagnosis as well as the use of an operative technique which can be safely applied to the teaching environment.  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