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   4096篇
  免费   16篇
  国内免费   1篇
电工技术   6篇
综合类   3篇
化学工业   120篇
金属工艺   9篇
机械仪表   14篇
建筑科学   33篇
矿业工程   1篇
能源动力   7篇
轻工业   66篇
水利工程   8篇
石油天然气   1篇
武器工业   2篇
无线电   68篇
一般工业技术   118篇
冶金工业   3587篇
原子能技术   1篇
自动化技术   69篇
  2023年   5篇
  2022年   4篇
  2021年   10篇
  2019年   9篇
  2018年   6篇
  2017年   9篇
  2016年   9篇
  2013年   50篇
  2012年   17篇
  2011年   58篇
  2010年   17篇
  2009年   17篇
  2008年   13篇
  2007年   17篇
  2006年   14篇
  2005年   20篇
  2004年   19篇
  2003年   21篇
  2002年   9篇
  2001年   11篇
  2000年   10篇
  1999年   128篇
  1998年   1185篇
  1997年   699篇
  1996年   412篇
  1995年   209篇
  1994年   190篇
  1993年   246篇
  1992年   20篇
  1991年   32篇
  1990年   37篇
  1989年   51篇
  1988年   39篇
  1987年   43篇
  1986年   21篇
  1985年   31篇
  1983年   15篇
  1982年   28篇
  1981年   21篇
  1980年   38篇
  1978年   15篇
  1977年   83篇
  1976年   146篇
  1975年   6篇
  1974年   5篇
  1972年   4篇
  1970年   7篇
  1955年   6篇
  1938年   3篇
  1937年   5篇
排序方式: 共有4113条查询结果,搜索用时 546 毫秒
51.
A 62-year-old female who had a complaint of palpitation was diagnosed as bicuspid aortic stenosis and left single coronary artery by the echocardiographic examination, cardiac catheterization study and coronary artery angiography. Aortic valve replacement was performed and the patient was discharged 22 days after surgery with good post-operative course. Preoperative coronary artery angiography was important in the case of aortic valvular disease.  相似文献   
52.
GRIFFIN (graphics investigation of familial information), an interactive graphics system for exploratory investigation of data on individuals associated by familial relationships, was designed to provide genetic epidemiologists a flexible, rapidly responsive tool for viewing and guiding exploration of complex databases in the context of familiar pedigree structures. It graphically portrays both categorical and multivariate scalar data on individuals in those structures. The display can be inverted to show all ancestors and descendants of any individual the user designates. It provides cues to censored information when bushy pedigrees cannot be fully displayed without sacrificing legibility. These guide users on where to next invert the system. Investigators may translate/zoom the display, vary the mode of representing data, point to individuals to obtain displays of alphameric information about them, etc. Developed in Fortran using IBM's GDDM graphics subroutines for an IBM 3090 mainframe, GRIFFIN's design anticipates porting to smaller systems.  相似文献   
53.
Patients with non-cardiac chest pain (NCCP) (n = 387) and cardiac chest pain (CCP) (n = 93) were compared with community controls (n = 81), using a symptom questionnaire that assessed the presence of irritable bowel syndrome (IBS), functional dyspepsia, and oesophageal dysfunction and chest pain characteristics. A significantly (p < 0.05) increased prevalence of symptoms compatible with IBS occurred in NCCP patients when compared with those with CCP and with controls. Dysphagia was more frequent in both those with non-cardiac and cardiac chest pain than in controls; this was not apparent, however, when patients with concomitant IBS were excluded. The presence of oesophageal or gastrointestinal symptoms did not enable discrimination with regard to the chest pain characteristics. We conclude that unselected referred patients with documented NCCP are more likely to have IBS and that the presence of oesophageal symptoms such as dysphagia may merely reflect the spectrum of the 'irritable gut'.  相似文献   
54.
55.
A male patient presented with complaints of fever, cough with expectoration, burning micturition and 5-6 semisolid motions per day for the past 6 days. Skiagram chest (PA view) revealed lung abscess in the left mid zone. There was no improvement, symptomatically and radiologically, after an empirical course of antibiotics (IV ampicillin and gentamycin). Sputum, urine and stool cultures grew salmonella group E organisms sensitive only to cefotaxime. The patient was treated with IV cefotaxime and responded well clinically, radiologically and bacteriologically.  相似文献   
56.
Purkinje cell toxicity is one of the characteristic features of the Gordon phenomenon, a syndrome manifested by ataxia, muscular rigidity, paralysis, and tremor that may lead to death (Gordon, 1933). Two members of the RNase superfamily found in humans, EDN (eosinophil-derived neurotoxin) and ECP (eosinophil cationic protein), cause the Gordon phenomenon when injected intraventricularly into guinea pigs or rabbits. We have found that another member of the RNase superfamily, an antitumor protein called onconase, isolated from Rana pipiens oocytes and early embryos, will also cause the Gordon phenomenon when injected into the cerebrospinal fluid of guinea pigs at a dose similar to that of EDN (LD50, 3-4 micrograms). Neurologic abnormalities of onconase-treated animals were indistinguishable from those of EDN-treated animals, and histology showed dramatic Purkinje cell loss in the brains of onconase-treated animals. The neurotoxic activity of onconase correlates with ribonuclease activity. Onconase modified by iodoacetic acid to eliminate 70% and 98% of the ribonuclease activity of the native enzyme displays a similar decrease in ability to cause the Gordon phenomenon. In contrast, the homologous bovine pancreatic RNase A injected intraventricularly at a dose 5000 times greater than the LD50 dose of EDN or onconase is not toxic and does not cause the Gordon phenomenon. A comparison of the RNase activities of EDN, onconase, and bovine pancreatic RNase A using three pancreatic RNA substrates demonstrates that onconase is orders of magnitude less active enzymatically than EDN and RNase A. Thus, another member of the RNase superfamily in addition to EDN and ECP can cause the Gordon phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
57.
58.
In the present study, the effect of bradykinin on basal and precontracted mouse-isolated trachea was investigated. In basal conditions mouse-isolated tracheal rings do not respond to bradykinin. However, when the tracheal rings were precontracted with carbachol (10(-7) M) a relaxation with bradykinin (3 x 10(-9)-3 x 10(-7)) was found. The maximal response amounted 69.7+/-4.1% (n=15) with a pD2 value of 7.2+/-0.21. The selective bradykinin B2 receptor antagonist HOE 140 (10(-10)-10(-8) M) antagonized the bradykinin-induced relaxation, while the bradykinin B1 receptor antagonist des-Arg9-Leu8-bradykinin (10(-6) M) had no influence. The selective bradykinin B1 receptor agonist des-Arg9-bradykinin (10(-6) M) caused a small relaxation (8.4+/-2.5%, n=6), which could be antagonized completely by the selective bradykinin B1 receptor antagonist des-Arg9-Leu8-bradykinin (10(-6) M) while addition of the selective bradykinin B2 receptor antagonist HOE 140 (10(-8) M) was without effect. In the presence of indomethacin (10(-6) M) the relaxation of bradykinin was completely abolished. Pretreatment of the tracheal rings with capsaicin, or the presence of the selective NK1 receptor antagonist RP 67851 (10(-6) M) or the presence of the nitric oxide synthase inhibitor L-NAME (3 x 10(-4) M) had no effect on the bradykinin-induced relaxation. In conclusion, these results demonstrate that the mouse-isolated tracheal is a preparation in which bradykinin exerts a relaxant response via stimulation of bradykinin B2 receptors. This response is probably mediated by prostaglandins.  相似文献   
59.
The calcium-dependent cell-cell adhesion molecule E-cadherin has been shown to counteract invasion of epithelial neoplastic cells. Using three monoclonal antibodies, we have demonstrated the presence of E-cadherin at the surface of human MCF-7/6 mammary carcinoma cells by indirect immunofluorescence coupled to flow cytometry and by immunocytochemistry. Nevertheless, MCF-7/6 cells failed to aggregate in a medium containing 1.25 mM CaCl2, and they were invasive after confrontation with embryonic chick heart fragments in organ culture. Treatment of MCF-7/6 cells with 0.5 microgram ml-1 insulin-like growth factor I (IGF-I) led to homotypic aggregation within 5 to 10 min and inhibited invasion in vitro during at least 8 days. The effect of IGF-I on cellular aggregation was insensitive to cycloheximide. However, monoclonal antibodies that interfered with the function of either the IGF-I receptor (alpha IR3) or E-cadherin (HECD-1, MB2) blocked the effect of IGF-I on aggregation. The effects of IGF-I on aggregation and on invasion could be mimicked by 1 microgram ml-1 insulin, but not by 0.5 microgram ml-1 IGF-II. The insulin effects were presumably not mediated by the IGF-I receptor, since they could not be blocked by an antibody against this receptor (alpha IR3). Our results indicate that IGF-I activates the invasion suppressor role of E-cadherin in MCF-7/6 cells.  相似文献   
60.
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