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   1300篇
  免费   24篇
电工技术   11篇
化学工业   31篇
金属工艺   1篇
机械仪表   8篇
建筑科学   11篇
矿业工程   2篇
能源动力   1篇
轻工业   74篇
水利工程   1篇
石油天然气   4篇
无线电   21篇
一般工业技术   69篇
冶金工业   1050篇
原子能技术   4篇
自动化技术   36篇
  2021年   9篇
  2020年   2篇
  2019年   3篇
  2018年   2篇
  2017年   3篇
  2016年   4篇
  2015年   7篇
  2013年   17篇
  2012年   6篇
  2011年   12篇
  2010年   9篇
  2009年   10篇
  2008年   24篇
  2007年   26篇
  2006年   23篇
  2005年   11篇
  2004年   9篇
  2003年   18篇
  2002年   20篇
  2001年   5篇
  2000年   8篇
  1999年   41篇
  1998年   289篇
  1997年   160篇
  1996年   118篇
  1995年   73篇
  1994年   57篇
  1993年   73篇
  1992年   11篇
  1991年   7篇
  1990年   13篇
  1989年   20篇
  1988年   15篇
  1987年   7篇
  1986年   9篇
  1985年   15篇
  1984年   5篇
  1983年   7篇
  1982年   5篇
  1981年   19篇
  1980年   8篇
  1979年   5篇
  1978年   6篇
  1977年   32篇
  1976年   80篇
  1975年   3篇
  1971年   2篇
  1966年   2篇
  1963年   2篇
  1959年   1篇
排序方式: 共有1324条查询结果,搜索用时 15 毫秒
1.
2.
The authors elaborated a method measuring air level of orthophosphorous and orthophosphoric acids by means of ion chromatography within the range of 0.1-25 mg/cu m. The samples are extracted through concentration on a filter. The analysis regime includes depression of the background levels. The separating column (4 x 200 mm) is filled with anion exchanger BT IAN, the suppressing column (6 x 150 mm) is filled with cation exchanger Dowex 50 x 8, the elutriating agent is 1.5 mM of sodium carbonate, the detector is conductometric. Minimal amounts of ions that could be detected in the analyzed solution are 7-10 ng (HPO32-), 10-15 ng (HPO 42-). The method is designed to analyze the air of workplace.  相似文献   
3.
Glycoprotein 330 (gp330) is a member of a family of endocytic receptors related to the low density lipoprotein receptor. gp330 has previously been shown to bind a number of ligands in common with its family member, the low density lipoprotein receptor-related protein (LRP). To identify ligands specific for gp330 and relevant to its localization on epithelia such as in the mammary gland, gp330-Sepharose affinity chromatography was performed. As a result, a 70-kDa protein was selected from human milk and identified by protein sequencing to be apolipoprotein J/clusterin (apoJ). Solid-phase binding assays confirmed that gp330 bound to apoJ with high affinity (Kd = 14.2 nM). Similarly, gp330 bound to apoJ transferred to nitrocellulose after SDS-polyacrylamide gel electrophoresis. LRP, however, showed no binding to apoJ in either type of assay. The binding of gp330 to apoJ could be competitively inhibited with excess apoJ as well as with the gp330 ligands apolipoprotein E, lipoprotein lipase, and the receptor-associated protein, a 39-kDa protein that acts to antagonize binding of all known ligands for gp330 and LRP. Several cultured cell lines that express gp330 and ones that do not express the receptor were examined for their ability to bind and internalize 125I-apoJ. Only cells that expressed gp330 endocytosed and degraded radiolabeled apoJ. Furthermore, F9 cells treated with retinoic acid and dibutyryl cyclic AMP to increase expression levels of gp330 displayed an increased capacity to internalize and degrade apoJ. Cellular internalization and degradation of radiolabeled apoJ could be inhibited with unlabeled apoJ, receptor-associated protein, and gp330 antibodies. The results indicate that gp330 but not LRP can bind to apoJ in vitro and that gp330 expressed by cells can mediate apoJ endocytosis leading to lysosomal degradation.  相似文献   
4.
This study addresses the influence the 7-substituent on the cytotoxicity of pyrrolo[1,2-alpha]-benzimidazole quinones possessing a 6-aziridinyl group (PBIs) and a 6-acetamido group (APBIs). Reduction of a PBI to the aziridinyl hydroquinone results in both nucleophile trapping (alkylation) and 1,5-sigmatropic shift reactions. The latter process is essentially an internal redox reaction wherein the hydroquinone causes reductive opening of the aziridinyl ring. The 7-substituent controls the fate of the aziridinyl ring by means of steric and electronic effects. An electron-rich 7-substituent favors the 1,5-sigmatropic shift reaction. If the 7-substituent distorts the 6-aziridinyl group from the conformation required for the 1,5-sigmatropic shift, then nucleophile trapping occurs. The 7-methyl substituent results in significant nucleophilic trapping, and the 7-unsubstituted and 7-methoxy substituents favor the 1,5-sigmatropic reaction. Thus, the 7-methyl PBIs show the most cytotoxicity of the analogues studied. The APBIs are cytotoxic only as quinones, and reduction to the hydroquinone results in loss of activity. Consistent with this observation, the change from 7-methyl to the more electron-rich 7-methoxy results in a substantial loss of APBI cytotoxicity as well as decreased topoisomerase II inhibition. The mechanism of inhibition is thought to involve the interacalation of only electron deficient APBIs into DNA.  相似文献   
5.
6.
7.
In the article the rules about etiology and pathogenesis of vegetative paroxysms are stated based on careful analysis of the publications of researches as Russian, so foreign authors, and also own experimental and clinical supervision. During experimental and clinical researches the modern methods were used, enabling to estimate from positions of the system analysis different parts of pathogenesis of vegetative paroxysms, and also to offer ways of differential diagnostics of the various forms of disease. The application of some new preparations and direction of therapy of vegetative paroxysms are substantiated, and also the various circuits of treatment of the patients with distinguishing forms of given pathology are motivated.  相似文献   
8.
Biopsies of cervix uteri from 166 patients with benign and malignant lesions (12 normal, 48 inflammatory lesion, 6 adenocarcinoma, 2 adenosquamous carcinoma and 98 from squamous cell carcinomas) were studied histochemically. The stains used were PAS with/without diastase, AB/PAS (pH 2.5) and OR/AB. In inflammatory lesions neutral mucin was predominent which was replaced by sialomucin and sulphomucin in endocervical polyps. In malignant lesions sulphomucin was predominent. Seventeen percent cases of squamous cell carcinomas needed reclassification after mucin staining. Of the fourteen large cell non-keratinizing squamous cell carcinomas, 12 were reclassified as squamous cell carcinoma with mucin secretion and 2 as adenosquamous carcinoma. One case of small cell non-keratinizing squamous cell carcinoma was reclassified as moderately differentiated adenocarcinoma. None of the keratinizing carcinomas had evidence of mucin secretion. Mucin histochemistry should be done routinely on non-keratinizing squamous cell carcinomas to pick up more cases of carcinoma with evidence of mucin secretion which can be missed on routine haematoxylin and eosin stains. Such carcinomas are known to pursue a more aggressive clinical course and have a poorer prognosis than non-mucin secreting type of squamous cell carcinoma.  相似文献   
9.
This study examines the nature and extent of the relationship between stress levels and intentions to participate in a worksite smoking cessation program among male current smokers (n = 220) employed in an automobile manufacturing plant. A plantwide survey was conducted which measured job stress, nonjob stress, smoking behavior, and intent to participate. The results of polychotomous logistic regressions suggest that among the current smokers in this plant, job and nonjob stress were positively associated with workers' intentions to participate in a worksite smoking cessation program. Thus, contrary to the popular notion that stress diminishes the motivation to quit, employees under high levels of stress may be most receptive to educational interventions intended to persuade smokers to commit to quitting.  相似文献   
10.
Changes in the activity of acid phosphatase (AP) and its isoenzymes (tartrate-insensitive AP and formalin-insensitive AP) were investigated in patients with food poisoning in the course of the disease. The activity of AP and its isoenzymes in the serum started to grow in early convalescence and reached maximum in late convalescence. Total activity of AP in food toxic infections consists primarily of the activity of its platelet fraction. AP activity may serve as an additional criterion to predict vascular platelet involvement of hemostasis.  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