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   2536篇
  免费   3篇
  国内免费   2篇
化学工业   23篇
金属工艺   2篇
机械仪表   7篇
建筑科学   11篇
能源动力   10篇
轻工业   71篇
石油天然气   1篇
无线电   9篇
一般工业技术   16篇
冶金工业   2383篇
原子能技术   1篇
自动化技术   7篇
  2020年   4篇
  2019年   2篇
  2017年   7篇
  2016年   2篇
  2015年   3篇
  2014年   3篇
  2013年   11篇
  2012年   3篇
  2011年   6篇
  2010年   10篇
  2009年   7篇
  2008年   5篇
  2007年   7篇
  2006年   10篇
  2005年   3篇
  2003年   8篇
  2002年   3篇
  2001年   2篇
  2000年   3篇
  1999年   69篇
  1998年   725篇
  1997年   399篇
  1996年   274篇
  1995年   169篇
  1994年   114篇
  1993年   159篇
  1992年   18篇
  1991年   19篇
  1990年   32篇
  1989年   28篇
  1988年   34篇
  1987年   15篇
  1986年   21篇
  1985年   14篇
  1984年   2篇
  1983年   4篇
  1982年   11篇
  1981年   17篇
  1980年   26篇
  1979年   2篇
  1978年   9篇
  1977年   77篇
  1976年   179篇
  1975年   3篇
  1965年   2篇
  1938年   3篇
  1916年   3篇
  1914年   2篇
  1912年   2篇
  1911年   1篇
排序方式: 共有2541条查询结果,搜索用时 0 毫秒
961.
A high-performance liquid chromatographic (HPLC) method using fluorescence detection has been developed for the simultaneous analysis of low nanogram concentrations of an anti-inflammatory drug, 5-Bromo-2-(4-fluorophenyl)-3-[4-(methylsulfonyl)phenyl]thiophene (DuP 697), and a potential metabolite (X6882) in human plasma and of DuP 697 in human urine. This assay method used an EM Separations Lichrospher C18 endcapped column. The mobile phase was acetonitrile-water (75:25, v/v). The detection of DuP 697 and X6882 was by fluorescence at excitation and emission wavelengths of 256 and 419 nm, respectively. The chromatographic system could separate DuP 697 from X6882, the external standard (anthracene), and other endogenous substances present in human plasma. In human plasma the limits of quantification for DuP 697 and X6882 were 3 and 20 ng/ml, respectively; the limit of quantification for DuP 697 in human urine was 5 ng/ml. These compounds were shown to be stable in frozen (-20 degrees C) human plasma and urine for at least 9 weeks. The assay described has been used to characterize DuP 697 pharmacokinetics after oral administration in humans.  相似文献   
962.
In S?o Paulo State, Brazil, five males, aged between 8 and 64 years, were attacked by 'Africanized' honey bees (Apis mellifera scutellata). The estimated number of stings received by each patient ranged from > 200 to > 1000. All five were transferred to intensive care units in S?o Paulo City. Clinical features included intravascular haemolysis, respiratory distress with ARDS, hepatic dysfunction, rhabdomyolysis (with myoglobinaemia and myoglobinuria), hypertension and myocardial damage (perhaps explained by release of endogenous catecholamines by venom phospholipase A2 and mellitin), shock, coma, acute renal failure and bleeding. Laboratory findings included gross neutrophil leucocytosis, elevated serum enzymes [AST, ALT, LDH, CPK (predominantly CPK-MM)] and creatinine. Clotting times were slightly prolonged. Despite treatment with antihistamines, corticosteroids, bronchodilators, vasodilators, bicarbonate, mannitol and mechanical ventilation, three of the patients died between 22 and 71 h after the attacks, with histopathological features of ARDS, hepatocellular necrosis, acute tubular necrosis, focal subendocardial necrosis and disseminated intravascular coagulation. Whole bee venom and phospholipase A2 (PLA2) antigen concentrations were measured in serum and urine for the first time, using enzyme immunoassay. High venom and PLA2 concentrations were detected in serum and urine for more than 50 h after the stings in two fatal cases, in one of which the total circulating unbound whole venom was estimated at 27 mg, one hour after the attack. An antivenom should be developed to treat the increasing numbers of victims of mass attacks by Africanized 'killer' bees in USA, Middle and South America.  相似文献   
963.
We report further characterization of a cementum-derived protein that promotes the adhesion and spreading of periodontal cells. The cementum attachment protein (CAP) was extracted from bovine cementum, separated by diethylamino ethyl (DEAE)-cellulose chromatography, and purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and C18 reverse phase high performance liquid chromatography. The purified preparation contained a single protein band migrating with M(r) 56,000. It did not cross-react with polyclonal antibodies to osteopontin, vitronectin, or other attachment proteins. The attachment activity was resistant to chondroitinase ABC digestion. An internal amino acid sequence of six peptides was determined by microsequencing, and the peptide sequences were not present in other attachment proteins described in cementum. Four sequences contained Gly-X-Y repeats typical of collagen helix. One 17 amino acid peptide had 82% homology with a type XII collagen domain. However, bovine type XII collagen did not promote fibroblast attachment. Although another 19-amino-acid-long peptide had 95% homology to bovine alpha 1 [I], two other peptides were only 74% and 68% homologous, and the CAP was not recognized by anti-type I collagen antibody. The attachment activity of CAP was susceptible to bacterial collagenase. The CAP did not cross-react with antibodies to type V, XII, and XIV collagens. These data and our previous immunostaining data indicate that the CAP is not related to other collagens or attachment proteins and that it is a collagenous attachment protein localized in cementum.  相似文献   
964.
The structural abnormalities and functional characteristics of dysfunctional prothrombin variants in two new kindreds have been determined. Prothrombin Corpus Christi (family 1) was purified and found to have markedly reduced fibrinogen clotting activity, yet normal amidolytic and near-normal platelet aggregating activity. A transition (C to T) at nucleotide position 8885, present in the heterozygous form in affected family members, resulted in the substitution of Cys for Arg 382. This substitution results in the loss of a positive charge within the fibrinogen-binding exosite of thrombin, thus accounting for the observed functional defect. A heterozygous C to T transition was also present at position 19994 in other family members with a hypoprothrombinemic phenotype. This mutation results in the replacement of Gln 541 (CAA) by a premature stop codon (TAA). Prothrombin Dhahran (family 2) was found to have markedly reduced fibrinogen clotting activity, but normal amidolytic activity. Affected family members were found to have a G to A transition at nucleotide position 7312 resulting in the substitution of His for Arg 271. This substitution results in the abolition of a factor Xa cleavage site, yielding meizothrombin rather than thrombin, on activation of prothrombin Dhahran by factor Xa. All but one of the above mutations occur at CpG dinucleotides, thus further supporting the observation of a high incidence of CpG transitions in hereditary dysprothrombinemia. The significant bleeding tendencies of individuals homozygous for prothrombin Dhahran (prothrombin clotting activity 5% to 7%) contrast sharply with the absence of significant chronic bleeding in the proband expressing prothrombin Corpus Christi (prothrombin clotting activity 2%). Our findings underscore the capacity of thrombin to contribute to clinical hemostasis by mechanisms other than its fibrinogen clotting activity.  相似文献   
965.
Four distinct genes that encode mucins have previously been mapped to chromosome 11p15.5. Three of these genes (MUC2, MUC5AC, and MUC6) show a high level of genetically determined polymorphism and were analyzed in the CEPH families. Linkage analysis placed all three genes on the genetic map in a cluster between HRAS and INS, and more detailed analysis of recombinant breakpoints revealed that MUC6 is telomeric to MUC2. Using these recombinants D11S150 was mapped close to MUC2. Ten of the 11 recombinant chromosomes studied in detail were paternal, and the recombinant events were distributed throughout the 11p15 region, suggesting that the high level of recombination observed in 11p15.5 is not due to a particular recombinational hot spot. Pulsed-field gel electrophoresis was used to make a detailed physical map of the MUC cluster and to integrate the physical and genetical maps. The gene order was determined to be HRAS-MUC6-MUC2-MUC5AC-MUC5B-IGF2. The MUC genes span a region of some 400 kb and the map extends 770 kb and contains 15 putative CpG islands. The order of the MUC genes on the map corresponds to the relative order of their expression along the anterior-posterior axis of the body, suggesting a possible functional significance to the gene order.  相似文献   
966.
The aim of the present paper was to study the effect of infrared laser radiation on endocrine regulation of immunogenesis and on endogenic opioid system. For this purpose experiments on rabbits were carried out. The animals underwent transcerebral radiation with subsequent induction of the primary immune response (PIR) to thymus-dependent antigen (sheep red blood cells). The PIR suppression was revealed in all test animals. It was more graphically expressed in rabbits exposed to impulse radiation. Immunodepression was combined with the increase of glucocorticoid activity of adrenal cortex, while no significant changes in thyroid hormones were registered. The 0.08 Joles impulse radiation cause a palpable fall in opioid concentration in blood plasma, the fact, which can be possibly accounted for the rapid exhaustion of opioid synthesis after their stimulation due to laser radiation.  相似文献   
967.
The results of aspirative lipectomy in patients with 2nd and 3rd stage of alimentary-constitutional obesity are analysed. The effectiveness of lipectomy with surgical creation of a small ventricle and without previous surgery, has been demonstrated. The criteria of patients selection, based on their somatic and psychic features, are formulated. Aspirative lipectomy has certain advantages over other types of plastic surgery as it has the minimal rate of postoperative complications.  相似文献   
968.
Community health, psychiatric, and pediatric nurses who work with young children and their families often assess the family's sleep and rest patterns, especially in relation to children's sleep disturbances. Nurses have traditionally taken a rigid approach on this issue that excludes culturally diverse options. The author uses examples from her own nursing education and from cross-cultural research to demonstrate the cultural bias favoring separation of child from parent. The article explores options for broadening nurses' assessment of family sleeping arrangements and designing interventions that take into consideration culturally diverse values and habits. Implications for nursing practice include greater trust-building and mutual learning.  相似文献   
969.
Ninety patients with carcinoma of the hypopharynx underwent pharyngolaryngectomy and reconstruction with a jejunal free autograft. Fifty-five patients had primary surgery and 35 salvage surgery for recurrence after radiotherapy. Following primary surgery 28 patients had postoperative radiotherapy and 27 did not. Complications occurred in 51 per cent of patients, the most common being necrosis of the jejunal graft (19 per cent); 12 per cent developed significant stenosis and 4 per cent died in the perioperative period. Eleven per cent of patients developed a fistula. The total number of complications diminished as the experience of the unit increased. Median follow-up was 4.9 years. Of patients treated with primary surgery, 48 per cent developed primary site recurrence (at 3 years) and 53 per cent neck node recurrence (at 5 years). The tumour-specific 5-year survival rate for all patients was 42 per cent. Following primary surgery 28 per cent survived for 5 years and after salvage surgery the rate was 59 per cent. Positive resection margins and extensive neck disease adversely affected survival (P = 0.02 and P = 0.001 respectively). The free revascularized jejunal graft is a safe and predictable method of repair following total pharyngolaryngectomy.  相似文献   
970.
Immunoproliferative small intestinal disease (IPSID) is a poorly recognized cause of malabsorption syndrome in India. Clinicopathological features of five patients with IPSID seen over a two-year period are described. Our data suggest that IPSID is commonly misdiagnosed as intestinal tuberculosis due to lack of awareness and reluctance to obtain small bowel biopsies. Empirical institution of anti-tubercular chemotherapy not only leads to delayed diagnosis but also possibly alters the natural history of the disease, resulting in an intermediate phase of amelioration followed by a terminal phase of lymphomatous transformation. The disease is therefore usually diagnosed at an advanced stage and hence is associated with a relatively poor outcome.  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