全文获取类型
收费全文 | 4467篇 |
免费 | 133篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 77篇 |
综合类 | 6篇 |
化学工业 | 879篇 |
金属工艺 | 90篇 |
机械仪表 | 60篇 |
建筑科学 | 161篇 |
矿业工程 | 22篇 |
能源动力 | 92篇 |
轻工业 | 445篇 |
水利工程 | 26篇 |
石油天然气 | 6篇 |
无线电 | 455篇 |
一般工业技术 | 743篇 |
冶金工业 | 1032篇 |
原子能技术 | 61篇 |
自动化技术 | 447篇 |
出版年
2023年 | 26篇 |
2022年 | 31篇 |
2021年 | 69篇 |
2020年 | 51篇 |
2019年 | 70篇 |
2018年 | 64篇 |
2017年 | 58篇 |
2016年 | 90篇 |
2015年 | 80篇 |
2014年 | 90篇 |
2013年 | 155篇 |
2012年 | 153篇 |
2011年 | 220篇 |
2010年 | 119篇 |
2009年 | 148篇 |
2008年 | 165篇 |
2007年 | 123篇 |
2006年 | 132篇 |
2005年 | 96篇 |
2004年 | 91篇 |
2003年 | 100篇 |
2002年 | 112篇 |
2001年 | 88篇 |
2000年 | 95篇 |
1999年 | 105篇 |
1998年 | 338篇 |
1997年 | 217篇 |
1996年 | 143篇 |
1995年 | 112篇 |
1994年 | 115篇 |
1993年 | 115篇 |
1992年 | 70篇 |
1991年 | 90篇 |
1990年 | 58篇 |
1989年 | 58篇 |
1988年 | 58篇 |
1987年 | 54篇 |
1986年 | 40篇 |
1985年 | 60篇 |
1984年 | 52篇 |
1983年 | 39篇 |
1982年 | 27篇 |
1981年 | 33篇 |
1980年 | 30篇 |
1979年 | 27篇 |
1978年 | 25篇 |
1977年 | 35篇 |
1976年 | 72篇 |
1975年 | 23篇 |
1973年 | 23篇 |
排序方式: 共有4602条查询结果,搜索用时 796 毫秒
21.
22.
HISTORY AND CLINICAL FINDINGS: A 39-year-old HIV positive patient developed myalgia, headache and cough 4 weeks after a tick bite. His temperature was 37.4 degrees C and a circular pale erythema was noted over the left lower leg. INVESTIGATIONS: C-reactive protein was raised to 120 mg/l, white blood cell count was 5860/microliter, CD4-lymphocyte count 250/microliter. The chest radiogram showed pneumonitic infiltration in the left lower lobe. There were IgM antibodies against Borrelia burgdorferi. TREATMENT AND COURSE: Left lower lobe pneumonia and chronic erythema migrans were diagnosed and he was given oral azithromycin (500 mg on the first day and 250 mg for 4 days). The pneumonia cleared up, but 2 weeks later he developed symptoms of meningitis (496 cells per microliter, 87% lymphocytes, positive Borrelia burgdorferi antibody titer), which quickly and lastingly responded to ceftriaxon (2 g daily by brief infusion for 14 days). CONCLUSION: This immune-compromised HIV-infected patient developed disseminated borreliosis with CNS involvement 2 weeks after the occurrence of chronic erythema migrans. The initial treatment of the latter with azithromycin was unable to prevent the meningitis. It is unlikely that there was a causal connection between the borreliosis and the pneumonia. 相似文献
23.
The NADPH-dependent metabolism of ifosphamide catalyzed by rat liver microsomes was investigated in order to identify individual P450 enzymes that activate this anti-cancer drug and to ascertain their relationship to the P450 enzymes that activate the isomeric drug cyclophosphamide. Pretreatment of rats with phenobarbital or clofibrate increased by up to 8-fold the activation of both ifosphamide and cyclophosphamide catalyzed by isolated liver microsomes. Studies using P450 form-selective inhibitory antibodies demonstrated that constitutively expressed P450s belonging to subfamily 2C (forms 2C11/2C6) make significant contributions to the activation of both oxazaphosphorines in uninduced male rat liver microsomes, while the phenobarbital-inducible P450 2B1 was shown to be a major catalyst of these activations in phenobarbital-induced microsomes. Pretreatment of rats with dexamethasone increased liver microsomal activation of ifosphamide approximately 6-fold without a corresponding effect on cyclophosphamide activation rates. Ifosphamide activation catalyzed by dexamethasone-induced liver microsomes was minimally inhibited by anti-P450 2B or anti-P450 2C antibodies, but was selectively inhibited by anti-P450 3A antibodies. Selective inhibition of liver microsomal ifosphamide activation was also effected by the macrolide antibiotic triacetyloleandomycin, an inhibitor of several dexamethasone-inducible 3A P450s. These studies establish that a dexamethasone-inducible family 3A P450 can make an important contribution to rat liver microsomal ifosphamide activation, and suggest that dexamethasone pretreatment might provide a useful approach for modulation of ifosphamide metabolism in order to improve its therapeutic efficacy in cancer patients. 相似文献
24.
25.
F Namouni F Doz ML Tanguy E Quintana J Michon H Pacquement E Bouffet JC Gentet D Plantaz P Lutz JP Vannier P Validire S Neuenschwander L Desjardins JM Zucker 《Canadian Metallurgical Quarterly》1997,33(14):2368-2375
This study investigates the role of high-dose chemotherapy with haematopoietic stem cell rescue as consolidation treatment in high-risk retinoblastoma (extraocular disease at diagnosis or relapse or invasion of cut end of optic nerve). 25 patients received high-dose chemotherapy including carboplatin (250 mg/m2/day from day 1 to day 5 for the 6 first patients and 350 mg/m2/day from day 1 to day 5 for the other patients), etoposide (350 mg/m2/day from day 1 to day 5) and cyclophosphamide (1.6 g/m2/day from day 2 to day 5) (CARBOPEC) followed by autologous haematopoietic stem cell rescue. 19 patients received this drug combination for chemosensitive extraocular relapse. The other 6 patients with histological high-risk factors were given this treatment as consolidation after enucleation and conventional chemotherapy. The three year disease-free survival was 67.1%. In 7 of the 9 relapsing patients, the first site of relapse was the central nervous system. All patients with central nervous system disease died except one. The main toxicity was haematological and digestive (mucositis and diarrhoea). 2 of the 13 evaluable patients had grade III and IV ototoxicity. One patient experienced an acute grade I reversible cardiotoxicity. The CARBOPEC regimen seems to be a promising therapeutic strategy in patients with high-risk retinoblastoma, especially those with bone and/or bone marrow involvement. This treatment did not improve the outcome of patients with central nervous system disease. 相似文献
26.
27.
Torshin Ivan Y.; Weber Irene T.; Harrison Robert W. 《Protein engineering, design & selection : PEDS》2002,15(5):359-363
Empirical criteria for identification of hydrogen bonds wereanalyzed to produce a set of geometrically consistent criteria.For a data set of 30 structures, application of a set of purelygeometrical criteria, along with exclusion of abnormal backboneconformations, also excluded a common interaction of Ser/Thrside chains with Asp/Glu side chains ([ST]/[DE] pairs). Theseinteractions were termed `bifurcated hydrogen bonds/', whichimplies delocalization of a positively charged hydrogen of hydroxylbetween the two acceptor atoms of the carboxylic group. These`bifurcated/' interactions are among the most common packingpatterns for [ST]/[DE] pairs of side chains. Therefore, theidentification of hydrogen bonds cannot be based on geometricalcriteria only and requires introduction of some physico-chemicalcriteria. 相似文献
28.
The multipurpose mask set described, which consists of three stepper reticles, contains 95% of all test structures required for CMOS process development and random defect detection, thereby dramatically reducing the stepper reticle inventory and the frequency of reticle changes. Realizing the mask set by two dozen standard unit processes minimizes the feedback loop for defect density data, parametric data and unit process data 相似文献
29.
Daniel Röhnert Fritz Phillipp Helfried Reuther Till Weber Egbert Wessel Michael Schütze 《Oxidation of Metals》2007,68(5-6):271-293
The initial stages of the metal-dusting process on Alloy 800 at 620 °C were investigated by light optical microscopy, RAMAN
spectroscopy, atomic-force microscopy, Auger electron spectroscopy, transmission-electron microscopy and electron back-scatter
diffraction. As it turned out the incubation period for metal-dusting is characterized by simultaneous formation of a heterogeneously
growing oxide scale and deposition of carbon. The material surface shows different tarnish colors depending on the substrate-grain
orientation with different susceptibility to the beginning of metal-dusting attack. “Low-index” grains were not attacked within
the times investigated while the other grain orientations showed pitting. Carbon is evidently incorporated into the oxide
scale from the very beginning of exposure with different intensities depending on the underlying substrate-grain orientation
leading to differences in the tarnish colors. As a consequence carbides are formed even underneath “dense” oxide layers. Evidently
metal-dusting attack starts at positions of the oxide scale where “higher carbon concentrations” are present. 相似文献
30.
C Wilken W Baltes I Mehlitz R Tiebach R Weber 《Zeitschrift für Lebensmittel-Untersuchung und -Forschung》1985,180(6):496-497
A rapid procedure for the isolation and clean-up on a silica gel column is described for the determination of Ochratoxin A from pork kidneys. The detection limit is 0.3 microgram/kg. 相似文献