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   2293篇
  免费   12篇
  国内免费   2篇
电工技术   8篇
化学工业   96篇
金属工艺   5篇
机械仪表   12篇
建筑科学   12篇
矿业工程   3篇
能源动力   4篇
轻工业   18篇
水利工程   1篇
石油天然气   5篇
无线电   44篇
一般工业技术   41篇
冶金工业   1980篇
原子能技术   4篇
自动化技术   74篇
  2022年   3篇
  2018年   4篇
  2017年   8篇
  2016年   8篇
  2015年   6篇
  2014年   7篇
  2013年   23篇
  2012年   12篇
  2011年   11篇
  2010年   10篇
  2009年   15篇
  2008年   15篇
  2007年   22篇
  2006年   12篇
  2005年   15篇
  2004年   8篇
  2003年   13篇
  2002年   5篇
  2001年   8篇
  2000年   11篇
  1999年   53篇
  1998年   595篇
  1997年   306篇
  1996年   216篇
  1995年   125篇
  1994年   103篇
  1993年   106篇
  1992年   22篇
  1991年   32篇
  1990年   27篇
  1989年   41篇
  1988年   42篇
  1987年   36篇
  1986年   35篇
  1985年   25篇
  1984年   5篇
  1983年   8篇
  1982年   16篇
  1981年   11篇
  1980年   24篇
  1979年   6篇
  1978年   8篇
  1977年   61篇
  1976年   141篇
  1975年   3篇
  1973年   5篇
  1971年   3篇
  1967年   3篇
  1937年   3篇
  1905年   2篇
排序方式: 共有2307条查询结果,搜索用时 15 毫秒
101.
Meckel's diverticulum is one of the primary concerns in the differential diagnosis of the pediatric patient with massive, acute gastrointestinal bleeding, intussusception, or abdominal pain of uncertain cause. The hospital course of two children with Meckel's diverticulum, successfully treated by laparoscopic excision, is presented, along with details of the operative procedure. Both patients recovered from the procedure without incident and were discharged at 24 and 48 hours after surgery. The authors believe a laparoscopic approach is safe and effective in the diagnosis and treatment of Meckel's diverticulum.  相似文献   
102.
Circulatory changes following standardized compression trauma to the hind leg in dogs were evaluated using an electromagnetic flow meter and repeated angiography. A transient increase of flow to the injured limb and within the traumatized region was observed. Good agreement was found between the electromagnetic flow recordings and estimates of relative changes in flow by the angiographic method.  相似文献   
103.
Oxyphil cells and oxyphil cell adenomas of parathyroid glands are, in most instances, regarded to be nonfunctioning. Although 21 cases of hyperparathyroidism associated with parathyroid oxyphil cell adenoma have been reported, secretion of hormone by these tumors has not been conclusively demonstrated. A parathyroid adenoma, diagnosed by light microscopy as oxyphil type, together with the results from ultrastructural and biochemical studies of the patient's adenomatous tissue, are reported here. The patient, a 64-year-old male, was found to have elevated serum calcium, low serum phosphorus, and elevated serum immunoreactive parathormone: findings consistent with hyperparathyroidism. After excision of two small normal-appearing glands and one greatly enlarged (1.9 g) parathyroid gland, those laboratory values returned to normal. Light microscopy of the enlarged parathyroid indicated that it consisted almost entirely of an oxyphil adenoma. Electron microscopy revealed that the adenoma was composed mainly of mitochondria-rich oxyphil cells but also of interspersed transitional oxyphil cells and rare scattered chief cells. Golgi zones, rough endoplasmic reticulum, and prosecretory and secretory-like granules were observed in some oxyphil cells, in most transitional oxyphil cells, and in the infrequent chief cells. Thus, many of these cells appear to contribute to the production and secretion of parathormone. Biochemical studies performed directly on the adenomatous tissue demonstrated that it was able to synthesize proparathormone and parathormone, although the proportion of hormonal peptide synthesis relative to that of the total protein synthesis in this tissue was much smaller (0.9%) than that found in normal parathyroid tissue (5.7%). There was a small increase in immunoreactive parathormone when the adenoma tissue was incubated in a low-calcium medium. These findings indicate that this oxyphil adenoma of the parathyroid gland synthesized and secreted parathormone, apparently to some extent autonomously, but suggest that its capacity to do so was largely dependent on its component of cells other than fully developed oxyphil cells, such as transitional oxyphil cells.  相似文献   
104.
In the suckling newborn rat, blood ketone bodies begin to increase slowly 4h after birth and then rise sharply between 12 and 16h, whereas the major increase in plasma non-esterified fatty acids and liver carnitine occurs during the first 2h of life, parallel with the onset of suckling. In the starved newborn rat, which shows no increase in liver carnitine unless it is fed with a carnitine solution, the developmental pattern of the ketogenic capacity (tested by feeding a triacylglycerol emulsion, which increases plasma non-esterified fatty acids by 3-fold) is the same as in the suckling animal. This suggests that the increases in plasma non-esterified fatty acids and liver carnitine seen 2h after birth in the suckling animal are not the predominant factors inducing the switch-on of ketogenesis. Injection of butyrate to starved newborn pups resulted in a pattern of blood ketone bodies which was similar to that found after administration of triacylglycerols, but, at all time points studied, the hyperketonaemia was more pronounced with butyrate. It is suggested that, even if the entry of long-chain fatty acids into the mitochondria is a rate-limiting step, it is not the only factor controlling ketogenesis after birth in the rat. As in the adult rat, there is a reciprocal correlation between the liver glycogen content and the concentration of ketone bodies in the blood.  相似文献   
105.
106.
Granulocytic sarcoma (chloroma) is a localized tumefaction of immature granulocytes that is typically seen in association with myelogenous leukemia. The primitive cell population seen in biopsy material may be misinterpreted as histiocytic lymphoma or other sarcoma unless additional studies are performed. We saw a 36-year-old woman with promyelocytic leukemia in remission who had the signs and symptoms of an acute coalescent mastoiditis. Histologic examination of the surgical specimen, however, demonstrated a granulocytic sarcoma. Our case exemplifies some of the difficulties that may be encountered in the diagnosis of granulocytic sarcoma and illustrates the point that symptoms of an inflammatory process in a patient with a diagnosis of leukemia must be regarded with a degree of suspicion.  相似文献   
107.
A case of multiple adenocarcinoma arising from the kidney, bladder, and prostate is presented with a relevant discussion of the possible factors of pathogenesis. A staged approach of radical extirpative surgery is suggested.  相似文献   
108.
109.
The largest human exposure to N-nitrosamines is in the industrial section. Leather tanners are exposed to N-nitrosodimethylamine at levels up to 47 microgram/m3, corresponding to 440 microgram/person/day. Workers in the curing area of tire factories are exposed to N-nitrosomorpholine at levels up to 27 microgram/m3, corresponding to a intake of 250 microgram/person/day. These industrial exposures are considerably greater than exposure via foodstuffs, beer, cosmetics, cutting fluids and herbicides.  相似文献   
110.
1. Part of the DNA extruded by cultured rat spleen cells occurs in the form of a low density lipid complex. 2. The present work indicates that this complex is also associated with protein but not with RNA and its elementary properties have been studied. 3. For example, it is destroyed by freezing and thawing or by deoxycholate treatment and small quantities of copper salts added to the medium may either inhibit or stimulate its release depending on the conditions.  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