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   635篇
  免费   2篇
电工技术   2篇
综合类   1篇
化学工业   19篇
机械仪表   1篇
建筑科学   1篇
轻工业   2篇
无线电   2篇
一般工业技术   3篇
冶金工业   595篇
原子能技术   1篇
自动化技术   10篇
  2023年   1篇
  2022年   2篇
  2021年   3篇
  2019年   1篇
  2018年   3篇
  2017年   2篇
  2016年   1篇
  2015年   3篇
  2013年   2篇
  2012年   1篇
  2011年   2篇
  2010年   2篇
  2009年   3篇
  2008年   2篇
  2007年   2篇
  2005年   3篇
  2004年   1篇
  2003年   2篇
  2001年   1篇
  1999年   15篇
  1998年   165篇
  1997年   113篇
  1996年   61篇
  1995年   50篇
  1994年   38篇
  1993年   33篇
  1992年   9篇
  1991年   11篇
  1990年   7篇
  1989年   7篇
  1988年   3篇
  1987年   10篇
  1986年   5篇
  1985年   5篇
  1983年   4篇
  1982年   2篇
  1981年   3篇
  1980年   3篇
  1979年   1篇
  1978年   1篇
  1977年   17篇
  1976年   34篇
  1975年   1篇
  1965年   1篇
  1955年   1篇
排序方式: 共有637条查询结果,搜索用时 0 毫秒
101.
OBJECTIVE: To investigate the role of tumor persistence in patients submitted to irradiation therapy and radical hysterectomy. DESIGN: A retrospective analysis of prognostic factors. LOCATION: Hospital A.C. Camargo, S?o Paulo, Brazil, a private non-profitmaking foundation and tertiary referral centre. PATIENTS: A total of 629 cases of invasive squamous cell carcinoma of the cervix were studied. Criteria for inclusion in the study were: confirmed histological diagnosis of squamous cell carcinoma and no previous treatment (except for preoperative radiotherapy carried out at the Hospital A.C. Camargo itself). At the end of the follow-up period, 410 patients (65%) had no evidence of disease and 219 (34.8%) had died because of the tumor. INTERVENTION: The patients were submitted to radical surgery and radiation therapy, separately or in combination between 1953 and 1982. MAIN OUTCOMES MEASURES: Multivariate analysis of the different variables was performed according to the Cox regression method. RESULTS: The variables of prognostic value were, in decreasing order of importance: the decade of patient admission (p = 0.0001), the modality of therapy employed (p = 0.0005), the presence of residual tumor in the surgical specimens (p = 0.0055) and the clinical stage of the disease (p = 0.0575). CONCLUSION: Radiation therapy controlled a considerable number of local tumors and pelvic lymph nodes but not all of them in every patient. There is a specific group of patients for whom radical surgery is necessary to achieve control of the disease.  相似文献   
102.
Two chemicals previously shown to have estrogenic activity, bisphenol A and octylphenol, were examined for their effects on accessory reproductive organs and daily sperm production in male offspring of mice fed these chemicals during pregnancy. These chemicals are used in the manufacture of plastics and other products, and have been detected in food and water consumed by animals and people. From gestation day 11-17 female mice were fed an average concentration (dissolved in oil) of bisphenol A or octylphenol of 2 ng/g body weight (2 ppb) and 20 ng/g (20 ppb). The 2 ppb dose of bisphenol A is lower than the amount reported to be swallowed during the first hour after application of a plastic dental sealant (up to 931 micrograms; 13.3 ppb in a 70 kg adult). We found that the 2 ng/g dose of bisphenol A permanently increased the size of the preputial glands, but reduced the size of the epididymides; these organs develop from different embryonic tissues. At 20 ng/g, bisphenol A significantly decreased efficiency of sperm production (daily sperm production per g testis) by 20% relative to control males. The only significant effect of octylphenol was a reduction in daily sperm production and efficiency of sperm production at the 2 ng/g dose. A new approach to studying physiologically relevant doses of environmental endocrine disruptors is discussed, particularly with regard to the development of the reproductive organs, the brain, and behavior.  相似文献   
103.
Cells expressing the hemagglutinin protein of influenza virus were fused to planar bilayer membranes containing the fluorescent lipid probes octadecylrhodamine (R18) or indocarbocyanine (DiI) to investigate whether spontaneous curvature of each monolayer of a target membrane affects the growth of fusion pores. R18 and DiI lowered the transition temperatures for formation of an inverted hexagonal phase, indicating that these probes facilitate the formation of negative curvature structures. The probes are known to translocate from one monolayer of a bilayer membrane to the other in a voltage-dependent manner. The spontaneous curvature of the cis monolayer (facing the cells) or the trans monolayer could therefore be made more negative through control of the polarity of voltage across the planar membrane. Electrical admittance measurements showed that the open times of flickering fusion pores were shorter when probes were in trans monolayers and longer when in cis monolayers compared with times when probe was symmetrically distributed. Open times were the same for probe symmetrically distributed as when probes were not present. Thus, open times were a function of the asymmetry of the spontaneous curvature between the trans and cis monolayers. Enriching the cis monolayer with a negative curvature probe reduced the probability that a small pore would fully enlarge, whereas enriching the trans monolayer promoted enlargement. Lysophosphatidylcholine has positive spontaneous curvature and does not translocate. When lysophosphatidylcholine was placed in trans leaflets of planar membranes, closing of fusion pores was rare. The effects of the negative and positive spontaneous curvature probes do not support the hypothesis that a flickering pore closes from an open state within a hemifusion diaphragm (essentially a "flat" structure). Rather, such effects support the hypothesis that the membrane surrounding the open pore forms a three-dimensional hourglass shape from which the pore flickers shut.  相似文献   
104.
This study carried out in Hong Kong, identified 29 Chinese patients' perceptions of the importance of nursing care behaviours in an acute setting using a Chinese language translated version of the CARE-Q instrument. Patients ranked items concerned with 'giving the patients' treatments and medication on time' as the most important and 'sits down with the patient' as the least important. Comparisons are made with the results from other cultures and specific Chinese cultural interpretations are drawn to provide direction for nursing care of Chinese patients in Hong Kong and worldwide.  相似文献   
105.
106.
High density oligonucleotide arrays (DNA chips) have been used in two color mutational analysis of the 3.43 kb exon 11 of the hereditary breast and ovarian cancer gene BRCA1 . Two color analysis allows competitive hybridization between a reference standard and an unknown sample, improving the performance of the assay. Fluorescein and phycoerythrin dyes werepreviously used due to their compatibility with a single line 488 nm excitation source. Here we show that an alternative dye combination, containing the energy transfer dye system phycoerythrin*cy5 along with phycoerythrin, provides more evenly matched signal intensities and decreased spectral overlap between the two fluorophores, while maintaining compatibility with a 488 nm excitation source.  相似文献   
107.
108.
The Wiskott-Aldrich syndrome (WAS) is a disease of profound thrombocytopenia and severe immune defects caused by an unidentified defective X chromosome gene. In this study, T lymphocyte function is examined using a panel of allospecific WAS patient T cell lines, previously found to express the abnormal disease gene and the cytoarchitectural defect characteristic of the disease. Although T cell lines from normal individuals proliferate vigorously in response to immobilized anti-CD3 mAb OKT3 and SPV-T3b, five of seven WAS patient T cell lines failed to proliferate and two lines showed significantly decreased proliferation when challenged with the immobilized anti-CD3 mAb. The deficient responsiveness of the WAS T cell lines to immobilized anti-CD3 mAb is a restricted defect, because the cells proliferate normally when challenged with allospecific Ag, PHA, or PMA plus ionomycin. Addition of anti-CD28 mAb did not correct the deficient proliferation of the WAS cells challenged with immobilized anti-CD3. Deficient response of the WAS T cell lines to immobilized anti-CD3 was detected also when earlier events of the proliferation process, IL-2 production and up-regulation of activation Ag CD69 and CD28, were measured. On the other hand, WAS cell lines did not differ from normal cell lines in binding of anti-CD3 mAb, mobilization of Ca2+ in response to soluble OKT3, and tyrosine phosphorylation and GTP binding of the CD3 zeta-chain in response to OKT3. Cumulatively, these findings demonstrate a striking restricted defect in the proliferative response of WAS T cells, which because it is found in cell lines free of secondary changes that occur in the patient circulation must be a reflection of the inherited defective disease gene product.  相似文献   
109.
Turnover of inositol polyphosphate pyrophosphates in pancreatoma cells   总被引:1,自引:0,他引:1  
There is little information concerning the intracellular function of inositol 1,3,4,5,6-pentakis- and hexakisphosphate, despite their being the most abundant inositol polyphosphates. Current opinions that they play passive roles as antioxidants (Graf, E., Mahoney, J. R., Bryant, R. G., and Eaton, J. W. (1987) J. Biol. Chem. 259, 3620-3624) or "housekeeping" molecules (Berridge, M. J., and Irvine, R. F. (1989) Nature 341, 197-205) arises from belief in their metabolic lethargy. However, we have discovered that cell homogenates, incubated with 5 mM fluoride and 5 mM ATP, converted both inositol hexakisphosphate (Km = 2 +/- 0.5 microM, Vmax = 9 +/- 2 pmol/mg of protein/min) and inositol 1,3,4,5,6-pentakisphosphate (Km = 13 +/- 4 microM, Vmax = 11 +/- 5 pmol/mg of protein/min) to more polar products. These reactions were also observed in intact cells treated with 0.5-20 mM fluoride, and the precursor/product relationships were confirmed by comparing the effects of fluoride on cells differentially labeled with [3H]inositol in either short-term or pulse-chase protocols. The novel products were determined to be inositol pyrophosphates because of their relatively specific hydrolysis by tobacco pyrophosphatase and alkaline phosphatase. The pyrophosphates were metabolized rapidly by cell homogenates back to their pentakisphosphate and hexakisphosphate precursors. This endogenous pyrophosphatase activity was inhibited by up to 99% by 5 mM fluoride in vitro. In intact cells incubated with 10 mM fluoride, about 20% of the inositol 1,3,4,5,6-pentakisphosphate pool, and 50% of the inositol hexakisphosphate pool were each converted to pyrophosphate derivatives within 1 h.  相似文献   
110.
In recent years, methods of consensus, developed for the solution of problems in the social sciences, have become widely used in molecular biology. We study a method of consensus originally due to Waterman et al. (Waterman, Galas and Arratis. 1984. Pattern recognition in several sequences: consensus and alignment. Bull. math. Biol. 46, 515-527) which is used to identify patterns or features in a molecular sequence where a pattern can vary in position within a given window. We show that some well-known consensus methods of the social sciences, the median and the mean, are special cases of this method for certain choices of the parameters used in it and give a precise account of the parameters for which these special cases arise. We also show that the specific parameters used in the method of Waterman et al. make their method equivalent to the media procedure which is widely used in the social sciences.  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