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   10685篇
  免费   13篇
  国内免费   3篇
电工技术   6篇
综合类   1篇
化学工业   55篇
金属工艺   38篇
机械仪表   11篇
建筑科学   33篇
矿业工程   1篇
能源动力   7篇
轻工业   33篇
水利工程   1篇
石油天然气   1篇
无线电   25篇
一般工业技术   119篇
冶金工业   10300篇
原子能技术   12篇
自动化技术   58篇
  2019年   3篇
  2018年   9篇
  2017年   7篇
  2016年   12篇
  2015年   5篇
  2014年   13篇
  2013年   42篇
  2012年   13篇
  2011年   22篇
  2010年   19篇
  2009年   27篇
  2008年   14篇
  2007年   24篇
  2006年   19篇
  2005年   14篇
  2004年   16篇
  2003年   25篇
  2002年   17篇
  2001年   8篇
  2000年   13篇
  1999年   301篇
  1998年   3341篇
  1997年   1942篇
  1996年   1186篇
  1995年   675篇
  1994年   531篇
  1993年   635篇
  1992年   67篇
  1991年   135篇
  1990年   112篇
  1989年   123篇
  1988年   136篇
  1987年   101篇
  1986年   88篇
  1985年   64篇
  1984年   5篇
  1983年   13篇
  1982年   53篇
  1981年   54篇
  1980年   67篇
  1978年   25篇
  1977年   195篇
  1976年   468篇
  1975年   15篇
  1974年   8篇
  1973年   3篇
  1966年   3篇
  1965年   3篇
  1955年   8篇
  1954年   4篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
The effects of a semidominant autosomal meiotic mutant, orientation disruptor (symbol: ord), located at 2-103.5 on the genetic map and in region 59B-D of the salivary map, have been examined genetically and cytologically. The results are as follows. (1) Crossing over in homozygous females is reduced to about seven percent of controls on all chromosomes, with the reduction greatest in distal regions. (2) Crossing over on different chromosomes is independent. (3) Reductional nondisjunction of any given chromosome is increased to about thirty percent of gametes from homozygous females. The probability of such nondisjunction is the same among exchange and nonexchange tetrads with the exception that a very proximal exchange tends to regularize segregation. (4) Equational nondisjunction of each chromosome is increased to about ten percent of gametes in homozygous females; this nondisjunction is independent of exchange. (5) The distributive pairing system is operative in homozygous females. (6) In homozygous males, reductional nondisjunction of each chromosome is increased to about ten percent, and equational nondisjunction to about twenty percent, of all gametes. (7) Cytologically, two distinct meiotic divisions occur in spermatocytes of homozygous males. The first division looks normal although occasional univalents are present at prophase I and a few lagging chromosomes are seen at anaphase I. However, sister chromatids of most chromosomes have precociously separated by metaphase II. Possible functions of the ord(+) gene are considered.  相似文献   
82.
Regional medical sympathectomy achieved by the intra-arterial injection of reserpine appeared to be of benefit in the treatment of five patients with acute or chronic frostbite injuries. Clinical improvement was associated with a significant increase in arteriographically determined regional perfusion.  相似文献   
83.
Administration of 4-aminopyrazolo [3,4-d] pyrimidine decreased serum cholesterol levels in the rat to less than 5 milligrams per deciliter. Coincident with this change, there was a 2.1 - to 16.0-fold increase in the rate of sterol synthesis in seven extrahepatic tissues. This suggests that cholesterol carried in serum lipoproteins plays a major role in regulating sterol synthesis in many extrahepatic tissues.  相似文献   
84.
The correlation of sexual education during childhood and the later contentment with the feminine sexual role was quantitively tested for its statistical significance. The data were collected for 386 women with a questionnaire and psychometric testing. Contentment with the feminine sexual role showed correlations to the age of the first sexual education (p smaller than 0.01), to the quality of the sexual education (p smaller than 0.05) and to the experience of the individual sexuality during adolescence (p smaller than 0.05). The earlier and the more positive the sex education the higher was the contentment with the own sexual role. Women who were most content with their presently experienced sexuality were also most content with their social role (p smaller than 0.01). Of importance in the discussion of the results were relationships between the contentment with the sexual role and the age (p smaller than 0.05), neurotic personality traits (p smaller than 0.01), obesity (p smaller than 0.01), psychosomatic complaints (p smaller than 0.05) and the present state of health (p smaller than 0.001). These results are of practical importance for sexual councelling in gynaecology.  相似文献   
85.
In human peripheral blood polymorphonuclear leukocytes and lymphocytes, GSH-oxidizing agents promote the movement of surface-bound concanavalin A (Con A) into caps and inhibit the assembly of microtubules (MT) that is normally induced by Con A binding. Con A capping and inhibition of MT assembly occur when GSH levels in cell suspensions are decreased by 30-70%, and return to GSH to control levels is accompanied by the appearance of cytoplasmic MT and by inhibition of the capping response with Con A. Oxidation of GSH markedly stimulates the hexose monophosphate shunt, and regeneration of GSH occurs rapidly. The data indicate that MT cannot be assembled or maintained in the face of decreased GSH levels. Thus, GSH homeostasis becomes critical during physiological events such as phagocytosis which simultaneously induce the assembly of MT and the production of agents like H2O2 that can oxidize GSH.  相似文献   
86.
87.
Ethane-1-hydroxy-1, 1-diphosphonate (EHDP) was administered in a dose of 20 mg/kg/d to 21 patients with symptomatic Paget's disease. All patients were treated for 6 months and then followed for an additional 6 months. There was a striking decline in serum alkaline phosphatase and urinary hydroxy-proline excretion observed after 3 months of therapy which was not significantly improved in the succeeding 3 months. Concomitantly there was marked improvement in clinical symptoms and bone scans. Following cessation of therapy, continued biochemical and clinical evidence of remission persisted. Several patients on repeat treatment with EHDP appeared to respond promptly. Side effects were minimal except for a possibly related osteomalacia and increased incidence of pathologic fractures.  相似文献   
88.
89.
A transplacentally induced lung tumor of strain C3Hf mice grows progressively when transplanted to (C3Hf X A)F1 hybrid mice but not when transplanted to C3Hf recipients. Progressive tumor growth occurs in [(C3Hf X A)F1 X C3Hf] backcross mice inheriting the H-2a haplotype from the F1 parent. Furthermore, radioresistant immunity to the lung tumor can be induced in C3Hf mice by immunization with normal tissue of B10.A and B10.A(2R) but not of B10 or B10.A(5R) strain mice.  相似文献   
90.
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