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   2634篇
  免费   9篇
  国内免费   1篇
综合类   2篇
化学工业   177篇
金属工艺   17篇
机械仪表   6篇
建筑科学   6篇
能源动力   8篇
轻工业   23篇
石油天然气   3篇
无线电   24篇
一般工业技术   22篇
冶金工业   2337篇
原子能技术   2篇
自动化技术   17篇
  2022年   3篇
  2018年   4篇
  2016年   6篇
  2014年   13篇
  2013年   22篇
  2012年   9篇
  2011年   10篇
  2010年   9篇
  2009年   7篇
  2008年   5篇
  2007年   9篇
  2006年   5篇
  2004年   6篇
  2003年   7篇
  1999年   79篇
  1998年   786篇
  1997年   438篇
  1996年   260篇
  1995年   147篇
  1994年   124篇
  1993年   144篇
  1992年   16篇
  1991年   25篇
  1990年   36篇
  1989年   33篇
  1988年   41篇
  1987年   43篇
  1986年   26篇
  1985年   31篇
  1984年   9篇
  1983年   7篇
  1982年   12篇
  1981年   13篇
  1980年   22篇
  1979年   4篇
  1978年   10篇
  1977年   53篇
  1976年   99篇
  1975年   6篇
  1974年   5篇
  1972年   9篇
  1971年   6篇
  1970年   8篇
  1969年   3篇
  1967年   2篇
  1966年   3篇
  1965年   2篇
  1964年   2篇
  1961年   4篇
  1960年   2篇
排序方式: 共有2644条查询结果,搜索用时 0 毫秒
51.
18 chronic insomniacs (mean age, 44.7 yrs; mean education, 3.4 yrs post high school), whose sleep problems were confirmed by all-night EEG recordings, were matched with normal sleepers on age, sex, and education. Insomniacs were significantly more depressed than normals on Zung's Self-Rating Depression Scale and the MMPI D scale. Insomniacs showed more anxious worrying behavior (high on the MMPI Pt, Hy, Hs, Taylor Manifest Anxiety scale, and Eysenck's Neuroticism scale, toward the sensitization end on Byrne's Repression-Sensitization scale, and overly concerned about the past and future on the Time Competence scale). Insomniacs also appeared to be sensory reducers, as evidenced by lower evoked potential responses to sound and by low scores on Zuckerman's Sensation-Seeking Scale. They were also less proficient in perceptual-motor skills on the WAIS. A stepwise regression analysis showed that the sensation-avoiding dimension accounted for the most variance in predicting an EEG sleep-efficiency criterion. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
52.
Polyunsaturated fatty acid methyl esters of soybean oil (MeSBO) were selectively conjugated as a means of increasing the linolenate selectivity of various homogeneous and heterogeneous hydrogenation catalysts. Kinetics of the conjugation reaction in various solvents indicated that linolenate conjugated 5–8 times faster than linoleate. Selective conjugation of MeSBO with potassiumt-butoxide in dipolar solvents resulted in an increase in linolenate hydrogenation selectivity to 7–8 with Ni and Pd heterogeneous catalysts, and to 7–10 with homogeneous and heterogeneous chromium carbonyl catalysts.Trans-unsaturation in the hydrogenated products was only 1–3% with the chromium carbonyl catalysts, in contrast to 30–39% with the heterogeneous metal catalysts. Triglycerides were readily converted to partial glycerides andt-butyl esters with the potassiumt-butoxide reagent. Presented at the AOCS North Central Section Symposium, March 1980.  相似文献   
53.
A silica-bonded complex was prepared by reacting polyphenylsiloxane with silylated Chromosorb and then with Cr(CO)6. This complex catalyzed stereoselective hydrogenation of sorbate tocis-3-hexenoate. Soybean methyl esters were hydrogenated at 210 C in cyclohexane to form products high incis unsaturation. The recovered catalyst could be recycled once with methyl sorbate. IR showed decreased Cr(CO)3 in the recovered catalysts, and the hydrogenation products contained inactive Cr.  相似文献   
54.
55.
The glycosylation of the equine interhaemal barrier and areola was studied throughout the period of gestation. Placentae of 35, 37, 50, 119, 152, 200, 280 and 300 days gestation were investigated, using semithin plastic embedded sections and a panel of 15 biotinylated lectins with an avidin-peroxidase revealing system. Glycosylation of the trophoblast and maternal epithelium showed the most change during the first 50 days of gestation, being associated with the initial stages of adhesion and attachment. In the trophoblast, non-bisected tri/tetraantennary complex N-glycan was only evident after day 37 and terminal N-acetyl galactosamine, alpha2,3- and alpha2,6-linked sialic acids disappeared at the same time. The areolar trophoblast exhibited some differences from microcotyledonary areas, especially with respect to 2-deoxy, 2-acetamido alpha-galactose and tri/tetraantennary, non-bisected complex N-glycan, suggesting that the differences in function between microcotyledonary and areolar trophoblast are reflected at both the morphological and the biochemical level. Granules of the maternal uterine epithelium bound many lectins, particularly those with specificity for bisected and non-bisected bi/triantennary N-linked glycan, 2-deoxy, 2-acetamido alpha-galactosyl, beta-galactosyl and some fucosylated termini. Binding to sialic acids in alpha2,3- and alpha2,6-linkage was sparse. Maternal and fetal capillaries showed little change in glycan expression over the period studied, being rich in bisected and non-bisected bi/triantennary N-linked glycan and sialic acids, with some terminal N-acetyl galactosamine and no detectable terminal fucosyl residues.  相似文献   
56.
KinMutBase (http://www.uta.fi/laitokset/imt/KinMut Base.html) is a registry of mutations in human protein kinases related to disorders. Kinases are essential cellular signalling molecules, in which mutations can lead into diseases including, e.g., immunodeficiencies, cancers and endocrine disorders. The first release of KinMutBase contains information for nine protein tyrosine kinases. There are altogether 170 entries representing 273 families and 403 patients. Mutations appear both in conserved hallmark residues of the kinases as well as in non-homologous sites. The KinMutBase WWW pages provide plenty of information, namely mutation statistics and display, clickable sequences with mutations, restriction enzyme patterns and online submission.  相似文献   
57.
Ipriflavone, an isoflavone synthesized from the soy isoflavone daidzein, holds great promise in the prevention and treatment of osteoporosis and other metabolic bone diseases. It has been widely studied in humans and found effective for inhibiting bone resorption and enhancing bone formation, the net result being an increase in bone density and a decrease in fracture rates in osteoporotic women. While ipriflavone appears to enhance estrogen's effect, it does not possess intrinsic estrogenic activity, making it an attractive adjunct or alternative to conventional hormone replacement therapy. Preliminary studies have also found ipriflavone effective in preventing bone loss associated with chronic steroid use, immobility, ovariectomy, renal osteodystrophy, and gonadotrophin hormone-releasing hormone agonists. In addition, it holds promise for the treatment of other metabolic diseases affecting the bones, including Paget's disease of the bone, hyperparathyroidism, and tinnitus caused by otosclerosis.  相似文献   
58.
59.
PURPOSE: We determined the temporal course of patient return to baseline quality of life after treatment with radical prostatectomy for early stage prostate cancer. MATERIALS AND METHODS: After establishing a longitudinal observational database of men undergoing radical retropubic prostatectomy we used established, validated quality of life questionnaires (RAND 36-Item Health Survey and University of California, Los Angeles Prostate Cancer Index) to document changes in general and disease specific health related quality of life (HRQOL). We assessed 90 patients at baseline before surgery and then at 3-month intervals for 1 year postoperatively. Logistic regression was used to explore predictors of the return to baseline. RESULTS: After prostatectomy patients had a significant decrease in all domains of HRQOL. Return to baseline was rapid in the general and bowel domains with at least two-thirds to three-fourths of patients reaching pretreatment levels within 6 months of surgery. Return to baseline was slower in the urinary and sexual function domains with 61 and 31% of the men, respectively, reaching pretreatment levels by 1 year after surgery. Of those who reached baseline the average intervals for the bowel, sexual and urinary domains were 5, 6 and 7 months, respectively. Married and white patients were more likely to achieve a return to baseline HRQOL during year 1 postoperatively. However, education level was inversely associated with the likelihood of returning to baseline. CONCLUSIONS: During the year after radical prostatectomy for early stage prostate cancer patient quality of life steadily improved. By 3 months postoperatively 30 to 40% of the patients had already recovered baseline levels of physical, mental and social functioning, and by 6 months more than 70% had reached baseline in the general HRQOL domains. By 12 months after surgery 86 to 97% of the patients had returned to baseline levels in each domain. Each domain continued to improve throughout the year. For the patients who reached baseline general HRQOL during followup average recovery time was 5 to 6 months.  相似文献   
60.
The roles of the dorsal hippocampus and the central nucleus of the amygdala in the expression of contextual fear were assessed using two measures of conditioned fear: freezing and fear-potentiated startle. A discriminable context conditioning paradigm was developed that demonstrated both conditioned freezing and fear-potentiated startle in a context paired previously with foot shock, relative to a context in which foot shock had never been presented. Post-training lesions of the central nucleus of the amygdala completely blocked both contextual freezing and fear-potentiated startle. Post-training lesions of the dorsal hippocampus attenuated contextual freezing, consistent with previous reports in the literature; however, these same lesions had no effect on fear-potentiated startle, suggesting preserved contextual fear. These results suggest that lesions of the hippocampus disrupt the freezing response but not contextual fear itself.  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