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   5274篇
  免费   31篇
电工技术   26篇
综合类   2篇
化学工业   143篇
金属工艺   16篇
机械仪表   27篇
建筑科学   31篇
矿业工程   1篇
能源动力   35篇
轻工业   88篇
水利工程   8篇
石油天然气   1篇
无线电   105篇
一般工业技术   166篇
冶金工业   4513篇
原子能技术   32篇
自动化技术   111篇
  2023年   6篇
  2022年   7篇
  2021年   10篇
  2019年   10篇
  2018年   22篇
  2017年   13篇
  2016年   20篇
  2015年   17篇
  2014年   27篇
  2013年   54篇
  2012年   46篇
  2011年   52篇
  2010年   36篇
  2009年   44篇
  2008年   42篇
  2007年   54篇
  2006年   27篇
  2005年   34篇
  2004年   20篇
  2003年   17篇
  2002年   17篇
  2001年   15篇
  2000年   19篇
  1999年   164篇
  1998年   1503篇
  1997年   831篇
  1996年   547篇
  1995年   278篇
  1994年   261篇
  1993年   272篇
  1992年   39篇
  1991年   48篇
  1990年   51篇
  1989年   58篇
  1988年   60篇
  1987年   38篇
  1986年   39篇
  1985年   43篇
  1984年   8篇
  1983年   17篇
  1982年   22篇
  1981年   23篇
  1980年   47篇
  1978年   9篇
  1977年   95篇
  1976年   195篇
  1975年   10篇
  1974年   3篇
  1972年   3篇
  1967年   3篇
排序方式: 共有5305条查询结果,搜索用时 0 毫秒
31.
The frequency and severity of CNSLD was studied in workers of an Hungarian firm (Ganz-Mavag) by means of questionnaire. Symptoms of CNSLD can be found more frequently in workers with air pollution than in those without. The symptoms of CNSLD show an age-dependence with regard to frequency and grade of severity, the single symptoms of CNSLD not occurring simultaneously and changing in their proportional frequency.  相似文献   
32.
33.
34.
Halofenate, a serum lipid-lowering agent which inhibits binding of thyroid hormone to thyroxine-binding globulin (TBG), was administered daily for 14 days to 8 hypothyroid subjects with elevated TSH concentrations as a result of incomplete thyroxine (T4) therapy. Drug administration resulted in mean increases in serum dialyzable fraction T4 (DFT4) of 52% over pretreatment levels (P less than 0.01) and in dialyzable fraction triiodothyronine (DFT3) of 26% in 7 subjects, (P less than 0.01). During halofenate treatment in these 7 subjects, serum TSH concentrations decreased significantly (mean = 39%, P less than 0.01) when DFT4 and DFT3 were increased by halofenate. In only two subjects was there a convincing temporal relationship between increased serum absolute free T4 (AFT4) and decreased serum TSH concentrations. Contrary to what would be predicted from the "free hormone hypothesis", changes in serum TSH concentration in these hypothyroid patients appeared to relate primarily to changes in the free fraction of circulating T4 and T3 (DFT4, DFT3), rather than to alterations in AFT4 or AFT3. Halofenate did not alter serum TBG binding capacity. An eighth subject did not show increased DFT4 and DFT3 during halofenate treatment despite achievement of therapeutic serum levels of the agent; in this patient, serum TSH levels rose progressively throughout the period of inadequate T4 replacement and halofenate administration. In hypothyroid patients, short-term halofenate use suggests that the pituitary-thyroid hormone feedback circuit can respond to increases in serum DFT4 and DFT3 in the absence of detactable increases in absolute free hormone concentrations.  相似文献   
35.
36.
A trial of a continuous intravenous infusion of Althesin is described for sedation during cardiac catheterisation, both for children and adults. The conditions produced for the procedure were very satisfactory. The advantages and problems of its use are discussed. The technique justifies further trials.  相似文献   
37.
The complexes 1,10-phenanthrolineethylenediamineplatinum(II) and 2,2'-bipyridineethylenediamineplatinum(II) have a planar, aromatic ligand system that facilitates intercalation, as shown by their ability to unwind closed circular duplex DNA. Nonbonded steric interactions can rotate the pryidine ligands out of the coordination plane in bis(pyridine)ethylenediamineplatinum(II), thus preventing intercalation. Fiber x-ray diffraction patterns of the two metallointeracalators indicate that the binding is governed by the neighbor exclusion principle.  相似文献   
38.
39.
Role of membrane-bound Ca in ghost permeability to Na and K   总被引:1,自引:0,他引:1  
The permeability of red cell ghosts to K is determined by the amount of membrane-bound Mg which, in turn, depends on internal Mg. Contrasting with such effect, an increase in cellular Ca raises K permeability. To test whether this action is due to a competitive displacement of membrane Mg, the free Ca content of human red cell ghosts was altered by means of Ca-EGTA buffers. Net Na and K movements as well as Ca and Mg bindings were assessed after incubation in a Na-medium at 37 degrees C. Raising Ca from 3 X 10(-7) to 1 X 10(-2) M caused a large K efflux with very little Na gain. Under similar conditions, Ca binding was increased without affecting membrane-bound Mg. Both Ca binding and K loss were markedly diminished by either adding ATP to the hemolytic medium or increasing internal Mg at a fixed Ca concentration. A Scatchard analysis showed three Ca binding sites, two of them having high affinity. It is concluded that Ca action does not arise from a displacement of membrane-bound Mg but from binding to different sites in the membrane. Presumably, high affinity sites are involved in the control of K permeability.  相似文献   
40.
This study was concerned with psychotherapists' evaluations of the outcome of therapy. Staff and resident psychiatrists employed in 23-item questionnaire to rate the seccess of psychotherapy with 85 of their inpatients. These were patients for whom psychotherapy constituted a significant part of the treatment that they received in the hospital. The therapists' responses to the questionnaire items were intercorrelated. The results indicated that a major aspect of a psychotherapist's judgment of the success of treatment-as these judgments usually are employed in current psychotherapy research-is the therapist's affective reaction to the patient, Better-liked patients were viewed as having improved more. However, when the therapists' responses were subjected to factor analysis, independent Improvement and Affection factors emerged. It is suggested that when therapists' ratings of success are used in psychotherapy research they should be treated or refined statistically to minimize potential confounding with their affection for patients.  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