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   590篇
  免费   4篇
电工技术   7篇
化学工业   66篇
金属工艺   13篇
机械仪表   9篇
建筑科学   4篇
能源动力   7篇
轻工业   15篇
水利工程   3篇
石油天然气   3篇
无线电   22篇
一般工业技术   69篇
冶金工业   347篇
原子能技术   4篇
自动化技术   25篇
  2023年   2篇
  2022年   2篇
  2021年   3篇
  2020年   5篇
  2019年   2篇
  2018年   2篇
  2017年   5篇
  2016年   3篇
  2014年   7篇
  2013年   15篇
  2012年   6篇
  2011年   10篇
  2010年   11篇
  2009年   11篇
  2008年   10篇
  2007年   11篇
  2006年   5篇
  2005年   13篇
  2004年   12篇
  2003年   5篇
  2002年   4篇
  2001年   8篇
  2000年   9篇
  1999年   27篇
  1998年   107篇
  1997年   64篇
  1996年   57篇
  1995年   17篇
  1994年   20篇
  1993年   25篇
  1992年   6篇
  1991年   11篇
  1990年   5篇
  1989年   7篇
  1988年   10篇
  1987年   5篇
  1986年   4篇
  1985年   8篇
  1984年   2篇
  1983年   6篇
  1981年   2篇
  1979年   7篇
  1978年   3篇
  1977年   9篇
  1976年   10篇
  1975年   3篇
  1973年   5篇
  1972年   3篇
  1971年   2篇
  1957年   2篇
排序方式: 共有594条查询结果,搜索用时 15 毫秒
91.
The Community Health Promotion Grants Program, sponsored by the Henry J. Kaiser Family Foundation, represents a major health initiative that established 11 community health promotion projects. Successful implementation was characterized by several critical factors: (1) intervention activities; (2) community activation; (3) success in obtaining external funding; and (4) institutionalization. Analysis of the program was based on data from several sources: program reports, key informant surveys, and a community coalition survey. Results indicate that school-based programs focusing on adolescent health problems were the most successful in reaching the populations they were targeting. The majority of the programs were able to attract external funding, thereby adding to their initial resource base. The programs were less successful in generating health promotion activities and in achieving meaningful institutionalization in their communities.  相似文献   
92.
OBJECTIVES: The purpose of this study was to determine the effects of poverty, program generosity, and health on state variations in enrollment of children and adolescents in the Supplemental Security Income (SSI) program during recent program expansions. METHODS: The relationship of state SSI rates for 1989 and 1992 to child poverty, health, and program generosity were determined by multiple regression. RESULTS: The mean percentage of children enrolled grew from 0.36% (1989) to 0.75% (1992). Poverty rates accounted for 78% of the variance among states in 1989 and 53% in 1992. Other indicators accounted for little variance. CONCLUSIONS: Differences in state poverty levels explained almost all variation in SSI enrollment.  相似文献   
93.
The aim of this work was to specify the time course of response to interferon (IFN) of hepatitis G virus (HGV) and hepatitis C virus (HCV) in coinfected individuals. A group of 33 patients, undergoing 12 months of IFN therapy for chronic hepatitis C, was screened for the presence of both HGV and HCV RNAs to select seven coinfected patients. Spontaneous recovery from HGV infection was excluded through the detection of antibodies to the envelope-2 protein of HGV and HCV isolates were genotyped. Within three months of treatment, we found that HGV RNA was transiently cleared in 6/7 patients, but the rate of long-term favorable response was very low (1/7). In addition, considering the same individuals separately, it was shown that HGV and HCV responded to IFN with different kinetics in 5/7 patients. Taken together, these results underscore the importance of the virological basis of the resistance to IFN treatment.  相似文献   
94.
In a single institution, we have used recombinant interferon- (IFN-) to treat 116 newly diagnosed Philadelphia-positive (Ph+) chronic myeloid leukemia (CML) patients and analyzed the predictive factors for response and survival. The patients whose median age was 50.3 years (range, 9 to 70) were administered IFN- (5 million units/m2/d) subcutaneously. The IFN- dose was subsequently adjusted to maintain the white blood cell and platelet counts between 1.5 and 5 x 10(9)/L, 50 and 100 x 10(9)/L, respectively. At diagnosis, the Sokal score was used to classify the patients into three groups: low (n = 57), intermediate (n = 42), and high risk (n = 16). A complete hematological response (CHR) was achieved in 93 cases (80.2%). Of the 116 patients, 113 were available for cytogenetic evaluation. Fifty patients (43%) achieved a major cytogenetic response (MCR) (=65% marrow Ph- cells), 37 of them having a complete cytogenetic response (CCR). The estimated 5-year survival of the 116 patients was 68% +/- 11% (95% confidence interval [CI]) with a median follow-up of 42 months (range, 3 to 114) and 85% +/- 11% (95% CI) with a median follow-up of 30.9 (range, 3 to 111) when patients were censored at the time of transplantation. Event-free survival at 5 years (adding death and transplant as event) was 46% +/- 11% (95% CI). Using proportional hazards regression to study time-dependent variables, we confirmed that the most significant factor associated with survival was the cytogenetic response (MCR or CCR) (P <.0001). This factor was independent compared with the Sokal score and baseline variables used to calculate the Sokal score. Moreover, using either univariate or multivariate analysis, the achievement of CHR within 3 months was strongly correlated with MCR (P <.0001). Minimum cytogenetic response (mCR, ie, at least 5% of Ph- metaphases) at 3 months was also a significant predictive factor for MCR (P <.0001). These results show that IFN- can induce a high rate of hematological and cytogenetic response when administered in doses leading to myelosuppression. Factors such as the achievement of CHR and mCR within 3 months could be useful to identify early those patients who will not respond to IFN- and who need alternative treatments such as stem cell transplantation.  相似文献   
95.
The RNase 4 family is unique among RNase enzymes, displaying the highest level of sequence similarity and encompassing the shortest polypeptide chain. It is the only one showing high specificity. The human representative is an intracellular and plasma enzyme, first isolated from colon adenocarcinoma cell line HT-29. The crystal structures of human recombinant RNase 4, unliganded and in complex with d(Up), have been determined, revealing in the unique active site an explanation for the uridine specificity. Arg101, at a position not involved in catalysis in the other RNase enzymes, penetrates the enzyme moiety shaping the recognition pocket, a flip that is mediated by the interaction with the (shorter chain) C-terminal carboxylate group, providing an anchoring point for the O4 atom of the substrate uridine. The bulky Phe42 side-chain forces Asp80 to be in the chi1=-72.49 degrees rotamer, accepting a hydrogen bond from Thr44, further converting the latter into a hydrogen bond acceptor. This favours an interaction with the -NH-donor group of uridine at position 3 over that with the =N-acceptor of cytidine. The two chemical groups that distinguish uracyl from cytosine are used by the enzyme to discriminate between these two bases.  相似文献   
96.
HISTORY AND ADMISSION FINDINGS: A 63-year-old man had for 10 months suffered from marked weight loss, night sweats, diffuse abdominal pain and increased stool frequency. He was admitted to evaluate an ultrasonically abnormal focus in the liver parenchyma and elevated liver function parameters. His sclerae were obviously icteric and he looked under-weight. INVESTIGATIONS: He had a hypochromic microcytic anemia and abnormal liver and pancreatic function tests: total bilirubin 3.11 mg/dl, direct bilirubin 2.21 mg/dl, GOT21U/l, gamma-GT 422 U/l, alkaline phosphatase 1449 U/l, alpha-amylase 481 U/l, lipase 2827 U/l. The serum creatinine level was elevated to 1.47 mg/dl. Computed tomography revealed enlarged liver and spleen as well as an enlargement of intraabdominal lymph nodes, chest radiogram and endoscopic cholangio-pancreatography were unremarkable. Biopsies from the lower duodenum, large intestine, bone marrow and liver showed inflammatory changes with Langhans-type mononuclear granulomas. Together with these findings an increased activity of the angiotensin-converting-enzyme (ACE) indicated sarcoidosis, other causes having been excluded. TREATMENT AND COURSE: All signs and symptoms rapidly improved under prednisolone, and 4 weeks after begin of treatment the biochemical abnormalities had clearly regressed. The raised serum levels of soluble IL-2 receptors and of neopterin, measures of sarcoidosis activity, had decreased. Activity of ACE had fallen. CONCLUSION: Sarcoidosis can present with diverse clinical signs and symptoms. In a case of multi-system disease that cannot be readily classified, sarcoidosis should be included in the differential diagnosis.  相似文献   
97.
As an internship applicant, do you know what internship agencies look for to select or exclude you from further consideration? In a survey, the authors examined exclusion and inclusion criteria used at 402 internship sites accredited by the American Psychological Association (APA). The 249 respondents (62%) rated fit between applicant goals and site opportunities as the most important inclusion criteria. Four exclusion criteria (lack of completion of orals, lack of APA status of doctoral program, poor fit between applicant goals and site opportunities, and incomplete doctoral course work) were most commonly used to eliminate applicants from consideration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
98.
99.
Syntheses of the enantiomers of malathion, malaoxon, and isomalathion are reported herein. Malathion enantiomers were prepared from (R)- or (S)-malic acid in three steps. Enantiomers of malathion were converted to the corresponding enantiomers of malaoxon in 52% yield by oxidation with monoperoxyphthalic acid, magnesium salt. The four isomalathion stereoisomers were prepared via two independent pathways using strychnine to resolve the asymmetric phosphorus moiety. The absolute configurations of the four stereoisomers of isomalathion were determined by X-ray crystallographic analysis of an alkaloid salt precursor. A high-performance liquid chromatography technique was developed to resolve the four stereoisomers of isomalathion, and to determine their stereoisomeric ratios.  相似文献   
100.
A new process of management of waste of composite materials from Sheet Moulding Compounds (SMC), as reinforcing fillers for thermoplastic materials, including both mechanical and chemical processes is proposed in this paper. Communited SMC being composed of coated glass fibres intimately mixed with calcium carbonate powder, their reinforcing power is low. First, the fibrous part was increased by partial dissolution of calcium carbonate present in the crushed products SMC. Second, a process of partial solvolysis was developed aiming at strong increasing the interfacial mechanical properties by functionalising of SMC load incorporated into polypropylene/grafted maleic anhydride polypropylene (PP/PPgma). At this effect, we investigated a treatment with a hot triamine (diethylenetriamine, DETA) in order to create a functionalisation, after scission of the bond ester of unsaturated polyester, as bridging amino-succinimide.The effect of this recycling way by partial solvolysis was checked from the mechanical properties of the resulting reinforced PP/PPgma material: Although a lower of Young modulus, better yield stress and especially resilience were observed.  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