全文获取类型
收费全文 | 760篇 |
免费 | 37篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 8篇 |
综合类 | 11篇 |
化学工业 | 8篇 |
金属工艺 | 6篇 |
机械仪表 | 12篇 |
建筑科学 | 12篇 |
矿业工程 | 5篇 |
能源动力 | 3篇 |
轻工业 | 11篇 |
水利工程 | 60篇 |
石油天然气 | 1篇 |
无线电 | 69篇 |
一般工业技术 | 14篇 |
冶金工业 | 492篇 |
原子能技术 | 4篇 |
自动化技术 | 85篇 |
出版年
2024年 | 2篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 27篇 |
2014年 | 15篇 |
2013年 | 7篇 |
2012年 | 6篇 |
2011年 | 15篇 |
2010年 | 14篇 |
2009年 | 14篇 |
2008年 | 10篇 |
2007年 | 14篇 |
2006年 | 20篇 |
2005年 | 49篇 |
2004年 | 11篇 |
2003年 | 9篇 |
2002年 | 27篇 |
2001年 | 6篇 |
1999年 | 12篇 |
1998年 | 140篇 |
1997年 | 78篇 |
1996年 | 60篇 |
1995年 | 29篇 |
1994年 | 35篇 |
1993年 | 15篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1978年 | 1篇 |
1977年 | 27篇 |
1976年 | 44篇 |
1975年 | 2篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有801条查询结果,搜索用时 15 毫秒
21.
DNA sequences from parts of the 12S, 16S and cytochrome b mitochondrial genes, which totalled 1049 aligned base pairs, were used to estimate the relationships of 49 species of Lacertidae, including representatives of 19 out of the 23 recognized genera and 23 species of the paraphyletic genus Lacerta. These data were used, together with morphological information, to estimate the relationships within the family. Molecular evidence corroborates the monophyletic status of many genera and species groups originally based on morphology. It indicates that Psammodromus forms a clade with Gallotia, which is the sister taxon of all other lacertids. These comprise three units: the primarily Afrotropical armatured group; the largely Oriental Takydromus; and the west Palaearctic Lacerta and its derivatives, Podarcis and Algyroides. Morphology also supports the first three assemblages, but suggests that they are derived from a paraphyletic Lacerta. Within Lacerta and its allies, DNA sequence analysis corroborates the affinity of some members of each of the subgenera Lacerta s. str. and Timon, and of the L. saxicola group. It also supports the relationship of L. monticola, L. bonnali and L. horvathi, and suggests that the L. parva--L. fraasi clade and L. brandli are not related to Psammodromus Gallotia, as morphology indicates, but instead are associated respectively with the L. danfordi and L. saxicola groups. DNA sequence data provide additional evidence that the eastern Arabian 'Lacerta' jayakari and 'L.' cyanura are members of the armatured clade and also sister species. Our analysis supports an origin for present lacertids in west Eurasia. The armatured clade invaded Africa, probably in the mid-Miocene, spreading widely and evolving increasingly xeric-adapted forms, one lineage of which later moved back into the Palaearctic. 'Lacerta' jayakari and 'L.' cyanura are assigned to Omanosaura, Lutz and Mayer 1986. The name Gallotiinae Cano, Baez, Lopez-Jurado & Ortega, 1984 is available for the Gallotia-Psammodromus clade, Eremiainae Shcherbak 1975 for the armatured clade and Lacertinae for Lacerta, Podarcis and Algyroides. Two new subgenera of Lacerta are proposed here: Caucasilacerta for L. saxicola and its allies, and Parvilacerta for L. parva and L. fraasi. 相似文献
22.
WJ Hoogendijk JS Purba MA Hofman RA de Vos EN Jansen DF Swaab 《Canadian Metallurgical Quarterly》1998,43(12):913-917
BACKGROUND: Depression is frequently encountered in Parkinson's disease (PD). In addition, more than half of the PD patients have a disturbed dexamethasone suppression test, which is associated with increased activity of corticotropin-releasing hormone (CRH) neurons. We recently found an increase in CRH neuron number, CRH-messenger RNA, and vasopressin colocalization in CRH neurons in the paraventricular nucleus (PVN) of depressed patients, which may be involved in the pathogenesis of depression. METHODS: The number of neurons expressing CRH was determined in the PVN of 6 depressed PD patients with a high score (> or = 13) on the Hamilton Depression Rating Scale, 6 nondepressed PD patients, and 6 controls. RESULTS: The three groups did not differ in the number of neurons expressing CRH. CONCLUSIONS: We hypothesize that activation of CRH neurons in the PVN, as we recently observed in idiopathic depression, does not play an essential role in depression in PD. 相似文献
23.
The cagA gene was detected in 100% of 16 Helicobacter pylori isolates from patients with gastric carcinoma versus 78% of 18 isolates from patients with duodenal ulcers (P = 0.344) and only 64% of 22 isolates from patients with gastritis only (P = 0.005) in Brazil. Also, there was a significant association between isolation of cagA+ s1-type vacA H. pylori in cases of stomach cancer and ulcers as opposed to cases of gastritis only (P = 0.004), but this was not true in Houston (P = 0.238), where 94% of all isolates were cagA+. 相似文献
24.
ES Naumenko AG Gol''del''man LI Tikhotskaia EP Zhovtiak AL Iarina VI Ershov EN Larina 《Canadian Metallurgical Quarterly》1998,37(2):16-20
Seventy-five newborns from multiple pregnancies with very low and extremely low birth weight are studied. 94% of the infants under 1000 g and 66% of those above 1000 g are born by vaginal way. Intrapartal asphyxia develop most often the second twins with birth weight under 1000 g--64.7%. These are the infants with higher morbidity: RDS--56.5%, IVH--100%. The survival rate of the twins of this group is notably lower than that of the infants from singleton pregnancies with equal weight and gestational age: 12.1% under 1000 g and 69% above 1000 g, against 38.3% and 77.9% respectively. 相似文献
25.
26.
AA Drosos PV Voulgari IA Papadopoulos EN Politi PE Georgiou AK Zikou 《Canadian Metallurgical Quarterly》1998,16(6):695-701
OBJECTIVE: To investigate the efficacy, tolerability and safety of cyclosporine A (CSA) in early rheumatoid arthritis (RA) patients. METHODS: Patients with an early diagnosis of RA, a disease duration of less than 3 years, and without prior disease modifying antirheumatic drug (DMARD) treatment were studied. They randomly received oral CSA (3 mg/kg/day) or oral methotrexate (MTX) (0.15 mg/kg/week). In addition, all patients in both groups received oral prednisone (7.5 mg/day). RESULTS: Fifty-two patients were assigned to the CSA group and 51 to the MTX group. After 24 months of treatment, 48 patients from the CSA group and 48 from the MTX group showed significant clinical improvement. This was evaluated by the duration of morning stiffness, grip strength, the total joint count, joint swelling, and joint tenderness and pain, compared to pre-treatment values. The clinical improvement was also associated with a significant decrease in ESR and CRP values in both groups. No significant radiological deterioration was observed in the CSA patients compared to those treated with MTX after 24 months. Four patients from the CSA group dropped out of the study, two because of a synovitis flare, one because of severe hypertrichosis and one because of severe gingival hyperplasia. Three patients from the MTX group withdrew, one because of disease flare-up and two because of gastrointestinal disturbances. CONCLUSION: Early immunointervention in RA patients appears to be crucial to limit the development of joint damage. Cyclosporine A appears to be effective, well tolerated and safe in the long-term treatment of RA and can therefore be used as a first immunomodulatory drug in the armamentarium for the treatment of RA. 相似文献
27.
KATP channels are unique in requiring two distinct subunits (Kir6.2, a potassium channel subunit) and SUR1 (an ABC protein) for generation of functional channels. To examine the cellular trafficking of KATP channel subunits, green fluorescent protein (GFP) was tagged to the cytoplasmic N or C terminus of SUR1 and Kir6. 2 subunits and to the C terminus of a dimeric fusion between SUR1 and Kir6.2 (SUR1-Kir6.2). All tagged constructs generated functional channels with essentially normal properties when coexpressed with the relevant other subunit. GFP-tagged Kir6.2 (Kir6.2-GFP) showed perinuclear and plasma membrane fluorescence patterns when expressed alone or with SUR1, and a very similar pattern was observed when channel-forming SUR1-Kir6.2-GFP was expressed on its own. In contrast, whereas SUR1 (SUR1-GFP) also showed a perinuclear and plasma membrane fluorescence pattern when expressed alone, an apparently cytoplasmic fluorescence was observed when coexpressed with Kir6.2 subunits. The results indicate that Kir6.2 subunits traffic to the plasma membrane in the presence or absence of SUR1, in contradiction to the hypothesis that homomeric Kir6.2 channels are not observed because SUR1 is required as a chaperone to guide Kir6.2 subunits through the secretory pathway. 相似文献
28.
MH Edwards S Pierangeli X Liu JH Barker G Anderson EN Harris 《Canadian Metallurgical Quarterly》1997,96(12):4380-4384
BACKGROUND: Previous studies have demonstrated that human monoclonal and polyclonal anticardiolipin antibodies have thrombogenic properties in vivo. Using such a model in which these antibodies have been shown to increase both the size of an induced thrombus and the duration of time in which such a clot lasts, we investigated whether hydroxychloroquine alters the dynamics of such thrombus formation. METHODS AND RESULTS: Three groups of nine mice were injected with purified immunoglobulin G (IgG) from a patient with the antiphospholipid syndrome (IgG-APS) and then fed with hydroxychloroquine at various doses (100, 6, and 3 mg/kg body wt). Three control groups of mice were also studied, including mice injected with IgG-APS and then fed with placebo, as well as two other groups injected with IgG from normal human serum and fed either hydroxychloroquine or placebo. A standardized thrombogenic injury was subsequently induced in the femoral vein of each mouse and the area (size) of thrombus measured as well as the total period of time that thrombus was present. Mice treated with hydroxychloroquine and IgG-APS showed significantly smaller thrombi that persisted for a shorter period of time compared with animals treated with IgG-APS and placebo. CONCLUSIONS: Hydroxychloroquine significantly diminished both thrombus size and total time of thrombus formation in mice previously injected with IgG-APS. 相似文献
29.
EN Kraiselburd A Salaman M Beltrán M Rivera J Oliver M Kessler M Knezevich A Rodriguez M Bilska D Montefiori LJ Torres-Bauza I Martinez 《Canadian Metallurgical Quarterly》1997,43(7):915-924
Non-infectious virus-like particles of SIVsmB7 that expresses env and gag gene products but are defective in pol and vpx/vpr were assessed for their ability to induce protective immunity against infection with pathogenic SIVsmE660 in rhesus macaques. Animals were immunized in three groups: group A was primed with cell-associated SIVsmB7 and boosted with cell-free SIVsmB7; group B was primed with cell-free SIVsmB7 and boosted with cell-free SIVsmB7 conjugated to iron oxide microbeads; group C was primed with cell-free SIVsmB7 mixed with Titer Max adjuvant and boosted with cell-free SIVsmB7 mixed with SAF-M adjuvant followed by secondary boosting with cell-free SIVsmB7 conjugated to microbeads. Animals were challenged intravenously with 20 animal infectious doses of SIVsmE660 grown in rhesus peripheral blood mononuclear cells 3 weeks after final boosting. All animals became infected as evidenced by quantitative virus cultivation. Sera from immunized animals contained low-titer antibodies by ELISA and low or undetectable neutralizing antibodies on the day of challenge but strong anamnestic antibody responses were observed following challenge. Interestingly, 2 of 3 animals in group A showed evidence of transient viremia and more stable CD4 counts following challenge as compared to the other immunized animals and to non-immunized controls. Thus, immunization with cell-associated SIVsmB7 did not provide sterilizing immunity against challenge with a highly pathogenic SIV strain but might have caused virus clearance later in infection. 相似文献
30.
We describe two cases of congenital chylothorax in siblings with important differences from previously described familial cases. Our findings support the likelihood of an autosomal recessive inheritance in some cases of this condition, rather than X-linked recessive inheritance, which has also been suggested. Autopsy findings from one of these cases and others previously described suggest that the pathophysiological mechanisms involved may be variable. 相似文献