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   11803篇
  免费   840篇
  国内免费   7篇
  12650篇
  2022年   65篇
  2021年   128篇
  2020年   81篇
  2019年   96篇
  2018年   141篇
  2017年   106篇
  2016年   194篇
  2015年   363篇
  2014年   417篇
  2013年   631篇
  2012年   713篇
  2011年   715篇
  2010年   510篇
  2009年   422篇
  2008年   646篇
  2007年   622篇
  2006年   605篇
  2005年   591篇
  2004年   612篇
  2003年   580篇
  2002年   515篇
  2001年   188篇
  2000年   162篇
  1999年   197篇
  1998年   183篇
  1997年   118篇
  1996年   136篇
  1995年   130篇
  1994年   110篇
  1993年   123篇
  1992年   151篇
  1991年   122篇
  1990年   120篇
  1989年   101篇
  1988年   148篇
  1987年   115篇
  1986年   73篇
  1985年   105篇
  1984年   134篇
  1983年   117篇
  1982年   120篇
  1981年   100篇
  1980年   102篇
  1979年   89篇
  1978年   101篇
  1977年   94篇
  1976年   84篇
  1975年   76篇
  1974年   91篇
  1973年   81篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
192.
Treatment techniques for airway obstruction in croup and epiglottitis are reviewed in the medical literature. Series totaling 295 nasotracheal intubations, and 591 tracheostomies were reviewed. There were two deaths attributable to airway complications in 126 patients in whom nasotracheal intubation was carried out. In three patients subglottic granulation tissue and subglottic stenoses developed from short-term nasotracheal intubation. There were no subglottic stenoses or tracheal stenoses reported in the 591 tracheostomies. From this review, it would seem feasible to use nasotracheal intubation for short-term airway treatment in croup and epiglottitis. The increasing occurrence of laryngeal and tracheal complications with long-term intubation suggests that tracheostomy be considered in such cases.  相似文献   
193.
Summary A 1730-g male infant, born at 37 weeks gestation, had multiple congenital anomalies, consisting of microcephaly, hypertelorism, bilateral cleft lip and palate, micrognathia, lowset ears, and cryptorchidism. Chromosome analysis showed a recombinant 22 derived from the paternal inversion (22) (p13q12.2). The proband's karyotype is 46,XY,rec(22),dup q,inv(22)(p13q12.2)pat, which has a duplication of q12.2qter. An identical recombinant has been reported in a female infant in Mexico whose mother was a carrier of the inversion. Similar congenital anomalies present in these two patients demonstrate the phenotype of duplication of the distal long arm 22. This report also documents the occurrence of an identical inversion in two apparently unrelated Mexican families.  相似文献   
194.
Poly(A)-positive mRNA extracted from tonsillar mononuclear cells stimulated with phytohemagglutinin-M and 12-o-tetradecanoyl phorbol 13-acetate was successfully translated into biologically active interleukin 2 (IL-2) in Xenopus laevis oocytes, and secreted into the incubation medium. In control experiments, the extract of oocytes injected with either poly(A)-negative RNA or buffer did not show any IL-2 activity. By sucrose density gradient centrifugation analysis, IL-2 mRNA was found as a single peak corresponding to a sedimentation coefficient of 10-11S.  相似文献   
195.
The detection of high activities of two sex-steroid biosynthetic enzymes—aromatase and 5-alpha-reductase—in pancreatic carcinoma tissue suggested the possibility that these enzymes may influence the circulating concentrations of sex-steroid hormones. Mean serum testosterone concentrations in 22 men and women with exocrine carcinoma of the pancreas were significantly lower than those in 20 healthy controls and 27 patients with other known malignancies, who were of similar age and sex composition. Low serum testosterone concentrations may be due to uptake by and metabolism within the tumour; alternatively, patients with low androgen concentrations may be at greater risk of developing pancreatic carcinoma.  相似文献   
196.
197.
When catalase was immunoprecipitated from different subfractions of mouse liver homogenates, the enzyme which was obtained from extracts of the large granular fraction exhibited a lower molecular weight than that from either the cytosol or purified peroxisomal fractions, as judged by sodium dodecyl sulphate polyacrylamide gel electrophoresis. This modification of the enzyme could be prevented by the addition of proteolytic inhibitors to extraction buffers; and consequently, unmodified catalase was able to be purified in the presence of 5 mM iodoacetamide. Electrophoretic comparison of the catalases against standards of known molecular sizes indicated that the unmodified enzyme had a subunit mass approximately 2,000 daltons larger than the modified enzyme. The significance of these proteolytic modifications has been discussed in relation to the involvements of catalase and peroxisome turnover.  相似文献   
198.
The purpose of this study was to learn wether a number of Ca2+ antagonists were effective in reducing contractile response of the isolated ileum of the sensitized and normal guinea pig. Contractions of the normal ileum in response to LTD4, acetylcholine, histamine, and potassium chloride were obtained before and after verapamil, diltiazen and papaverine. Ovalbumin-induced contractions of the ovalbumin-sensitized ileum were obtained in the presence of the three Ca2+ antagonists. In the normal ileum, all the Ca2+ antagonists were highly effective in diminishing the contractile responses to LTD4, acetylcholine, histamine and potassium chloride. In the sensitized ileum, ovalbumin-evoked contractions, with subsequent release of a potent contractile mediator (presumably SRS-A), were Ca2+-dependent since verapamil, diltiazem and papaverine caused a concentration-related reduction of contractions. Thus, the influx of extracellular Ca2+ plays a key role in the contractile responses of the normal and sensitized guinea pig ileum when stimulated by various potent agonists acting on specific receptors or on the cell membrane.  相似文献   
199.
We have previously shown that several agents which interfere with binding of ligands to the mannose-glycoprotein receptor on macrophages can inhibit zymosan-induced lysosomal enzyme secretion. Here we show that mannose only reduces the association of zymosan with macrophages during the first hour of exposure; after longer periods of uptake no effect is detectable. We have previously shown that mannose reduces surface binding of zymosan, probably by interfering selectively with binding to the mannose receptor. The present inhibition of association of zymosan with macrophages during short exposures can be entirely explained by this reduction of binding. Macrophages must therefore internalize zymosan at sites in addition to the mannose receptor. In contrast to macrophages the murine macrophage-like cell line P388D1 is lacking the mannose-glycoprotein receptor. Accordingly we find that binding of zymosan to P388D1 is much slighter than to macrophages and is unaffected by mannose or mannose-6-phosphate. The spontaneous lysosomal enzyme secretion of P388D1 is also unaffected by mannose. The data on macrophages confirm our previous suggestion that agents interfering with the mannose receptor inhibit the induction of lysosomal enzyme secretion by acting directly on the receptor. The data on P388D1 cells support this assertion by excluding effects at later steps in the secretory pathway.  相似文献   
200.
After a boy of Mexican-American descent became jaundiced during treatment of a serious urinary tract infection with an oxidant drug, an extensive hematological examination was made. The important finding was the presence of Hb-Leiden to the extent of less than 3% or about a tenth of the usual percentage. Although inclusion bodies are present in the erythrocytes at all times, his hematological parameters have remained normal. The genetic basis for the unusually small amount of Hb-Leiden in the propositus may be due to the Hb-Leiden gene in an anti-Lepore configuration, that is, and Hb-Leiden gene in cis to the normal β and δ genes.  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