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   1859篇
  免费   2篇
电工技术   3篇
化学工业   15篇
金属工艺   16篇
机械仪表   7篇
建筑科学   2篇
能源动力   6篇
轻工业   3篇
水利工程   1篇
无线电   8篇
一般工业技术   21篇
冶金工业   1775篇
自动化技术   4篇
  2021年   2篇
  2020年   1篇
  2019年   4篇
  2018年   1篇
  2016年   2篇
  2015年   1篇
  2014年   2篇
  2013年   3篇
  2012年   2篇
  2011年   2篇
  2010年   5篇
  2009年   2篇
  2008年   9篇
  2007年   5篇
  2006年   5篇
  2005年   3篇
  2004年   3篇
  2003年   4篇
  2002年   3篇
  2001年   2篇
  2000年   4篇
  1999年   61篇
  1998年   583篇
  1997年   295篇
  1996年   204篇
  1995年   85篇
  1994年   90篇
  1993年   104篇
  1992年   14篇
  1991年   32篇
  1990年   26篇
  1989年   26篇
  1988年   21篇
  1987年   23篇
  1986年   24篇
  1985年   27篇
  1984年   2篇
  1983年   6篇
  1982年   5篇
  1981年   8篇
  1980年   19篇
  1979年   1篇
  1978年   5篇
  1977年   38篇
  1976年   87篇
  1975年   5篇
  1965年   1篇
  1962年   2篇
  1955年   1篇
  1954年   1篇
排序方式: 共有1861条查询结果,搜索用时 15 毫秒
81.
Nonobese diabetic (NOD) mice genetically deficient in B lymphocytes (NODJg mu(null)) are resistant to T cell-mediated autoimmune insulin-dependent diabetes mellitus (IDDM). Ig infusions from diabetic NOD donors did not abrogate IDDM resistance in NODJg mu(null) mice. However, T cell responses to the candidate pancreatic beta cell autoantigen glutamic acid decarboxylase (GAD), but not the control Ag keyhole limpet hemocyanin, were eliminated in NODJg mu(null) mice. To initially test whether they contribute to IDDM as APC, NOD B lymphocytes were transferred into NODJg mu(null) recipients. B lymphocytes transferred into unmanipulated NODJg mu(null) recipients were rejected by MHC class I-restricted T cells. Stable T and B lymphocyte repopulation was achieved in irradiated NODJg mu(null) mice reconstituted with syngeneic bone marrow admixed with NOD B lymphocytes. IDDM susceptibility was restored in NODJg mu(null) mice reconstituted with syngeneic marrow plus B lymphocytes, but not with syngeneic marrow only. T cell responses to GAD were restored only in NODJg mu(null) mice reconstituted with syngeneic marrow plus B lymphocytes. Hence, B lymphocytes appear to contribute to IDDM in NOD mice as APC with a preferential ability to present certain beta cell Ags such as GAD to autoreactive T cells.  相似文献   
82.
Ibogaine, an alkaloid found in the root bark of the African shrub Tabernanthe iboga, has been claimed to interrupt opioid dependence in humans; in animals, it has been shown to inhibit morphine self-administration and to attenuate signs of morphine withdrawal. However, ibogaine has some neurotoxicity, and because of this, efficacious and safer congeners of ibogaine have been sought, 18-Methoxycoronaridine (18-MC), a novel iboga alkaloid congener, has been shown, in animals, to mimic the effects of ibogaine on morphine self-administration without producing any ibogaine-like neurotoxiticity. In the present study, 18-MC was shown to attenuate five of seven signs of morphine withdrawal in rats. The data suggest that 18-MC will ameliorate symptoms of opioid dependence in humans.  相似文献   
83.
Birth and weaning weights adjusted for age of dam from four lines of Hereford cattle were analyzed to determine the relationships among grandmaternal, maternal, and direct genetic effects. Three lines were selected for 1) weaning weight (WWL), 2) yearling weight (YWL), and 3) an index of yearling weight and muscle score (IXL). The fourth line was an unselected control line (CTL). Numbers of observations ranged from 1,699 (CTL) to 2,811 (WWL), and number of animals in the pedigree file ranged from 2,266 to 3,192. Two animal models were used to obtain estimates by REML using an average information method. Model 1 included random direct and maternal genetic, permanent maternal environmental, and residual environmental effects, and fixed sex x year effects. Model 2 additionally included random grandmaternal genetic and permanent grandmaternal environmental effects. For birth weight, Models 1 and 2 gave almost identical estimates for direct and maternal heritability, and for the fraction of variance that was due to maternal permanent environmental effects. Estimates for grandmaternal heritability could be obtained only for IXL (.03) and CTL (.01). For weaning weight, estimates for direct heritability were similar from both models. Estimates for maternal heritability from Model 1 were .18, .20, .13, and .20, and corresponding estimates from Model 2 were .34, .31, .13, and .34 for WWL, YWL, IXL, and CTL, respectively. For IXL, estimates for variances that were due to grandmaternal genetic and grandmaternal permanent environmental variances could not be obtained and were set to zero. Grandmaternal heritability estimates for WWL, YWL, and CTL were .05, .09, and .12. Estimates of correlations between direct and maternal genetic effects were -.13, -.44, -.11, and -.26 for WWL, YWL, IXL, and CTL. Estimates of correlations between direct and grandmaternal genetic effects were .21, .83, and .55, and those between maternal and grandmaternal genetic effects were -.99, -.84, and -.76 for WWL, YWL, and CTL, respectively. These results indicate that grandmaternal effects may be important for weaning weight and that maternal heritability may be underestimated if grandmaternal effects are not included in the model.  相似文献   
84.
Hypertensive end-stage renal disease (ESRD) purportedly accounts for 25% of new ESRD patients each year in the United States, but remains poorly understood. Clinical features include normal renal function at diagnosis of hypertension, family history of hypertension, left ventricular hypertrophy, and minimal proteinuria. We evaluated clinical and historic data documenting the diagnosis of hypertensive ESRD in 43 patients with ESRD attributed to hypertension who were referred to our center for renal transplantation. Hypertensive ESRD patients were more likely to be black patients with left ventricular hypertrophy compared with our overall population. Few of the hypertensive ESRD patients had undergone kidney biopsy, none of whom had classic features of benign nephrosclerosis. Less than 5% of patients had hypertension documented at any time with normal renal function. Based on our review, it is clearly possible that the number of patients reaching dialysis and transplantation with renal failure attributed to hypertensive ESRD may be overestimated.  相似文献   
85.
Casein kinase I (CKI) is a family of serine/threonine protein kinases found in all eukaryotes examined to date. Here, the rat CKI isoforms alpha and alpha L were cloned and expressed in both eukaryotic and prokaryotic systems. Characterization of the genomic DNA flanking the exon unique to CKI alpha L demonstrated that CKI alpha and CKI alpha L arise by the alternative splicing of a common pre-mRNA molecule. To the best of our knowledge, the alpha L isoform is the only known active serine/threonine kinase to contain an insert within its catalytic domain. Tissue distribution of each splicing isoform was examined by RT-PCR, immunoprecipitation, and Western blotting. Both isoforms were expressed in all tissues tested but at different levels. Bacterially expressed CKI alpha isoforms were active and therefore biochemically characterized. CKI alpha and CKI alpha L proteins were demonstrated to have casein kinase I catalytic properties. More importantly, the recombinant isoform proteins exhibited differences in binding and activity toward common CKI substrates. These observations demonstrate that the alpha L insert within the kinase domain modulates substrate kinetics. These kinetic differences suggest that CKI alpha and CKI alpha L may perform different biological roles.  相似文献   
86.
OBJECTIVE: Relationships among different dimensions of patient satisfaction and selected demographic, clinical, and outcome variables were explored in a sample of severely ill people receiving inpatient psychiatric services. METHOD: The sample consisted of 81 patients admitted to and discharged from an inpatient psychiatric unit at a midwestern Veterans Affairs medical center. Stepwise multiple regression was used to examine the relationship between patient satisfaction and self-reported changes in quality of life, symptomatology, and level of functioning as measured by the Treatment Outcome Profile. Other variables such as diagnosis, length of stay, employment, living situation, and prior psychiatric and substance abuse treatment were also considered. A subsample of the most satisfied and dissatisfied patients was chosen to further explore variables contributing to satisfaction with services. RESULTS: Patient satisfaction was related to initial level of functioning, certain diagnoses, and treatment gains. Clinicians were highly accurate in identifying patients who were satisfied, based on blind chart reviews. CONCLUSIONS: This study underscores the significant relationships between patient satisfaction, psychiatric diagnosis, and other outcome measures, and argues for the validity and utility of patient satisfaction measures in assessing the efficacy of inpatient care.  相似文献   
87.
Fallopian tubes were obtained from 25 women undergoing abdominal hysterectomy. Pieces of fallopian tube mucosa were placed in culture flasks containing minimum essential medium in Earle's salts supplemented with fetal bovine serum. First passage was carried out after 7-10 days and subcultures in 4-5 days. For polarised cell culture, epithelial cells were seeded onto an extracellular matrix system. New epithelial cells were seen on day 2-3 of the primary culture and epithelial patches on day 7-10. Cells reached confluence in 4-5 days in subcultures. The cells could be subcultured for 7-11 passages with a life span of 42-60 days. Epithelial origins of the cells were confirmed by immunofluorescence staining with anti-cytokeratin antibody. Polarised cells showed a columnar pattern, microvilli on their apical surface and basally located nucleus whereas non-polarised cells were flat. It was concluded that the human fallopian tube epithelial cells can be cultured in vitro to create non-polarised and polarised cell layers by using a simple and reproducible technique and this system can be a potential model to study function of the fallopian tube.  相似文献   
88.
89.
Glycogen Synthase Kinase-3 (GSK-3) was isolated from bovine heart tissue extracts by a procedure involving ammonium sulfate fractionation, followed by chromatography on phosphocellulose, Cibacron blue 3GA-agarose, DEAE-Sephacel, CM-Sepharose, heparin-agarose, myelin basic protein-Sepharose, and LiChrospher 1000 C00-. GSK-3 was identified by its activation of protein phosphatase-1i (PP-1i). The purified enzyme had a specific activity of 25,500 units of protein phosphatase-1i activated/mg protein. The enzyme is an asymmetric monomeric protein of 53 kDa. The molecular size and retention of activity after autophosphorylation indicated that the isolated enzyme was the GSK-3 alpha-isoform.  相似文献   
90.
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