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   21601篇
  免费   849篇
  国内免费   318篇
电工技术   474篇
综合类   546篇
化学工业   3863篇
金属工艺   521篇
机械仪表   737篇
建筑科学   903篇
矿业工程   183篇
能源动力   573篇
轻工业   2316篇
水利工程   251篇
石油天然气   178篇
武器工业   27篇
无线电   2407篇
一般工业技术   2858篇
冶金工业   3857篇
原子能技术   169篇
自动化技术   2905篇
  2023年   119篇
  2022年   354篇
  2021年   494篇
  2020年   266篇
  2019年   346篇
  2018年   395篇
  2017年   367篇
  2016年   420篇
  2015年   365篇
  2014年   556篇
  2013年   1043篇
  2012年   829篇
  2011年   1017篇
  2010年   779篇
  2009年   852篇
  2008年   838篇
  2007年   845篇
  2006年   739篇
  2005年   637篇
  2004年   705篇
  2003年   917篇
  2002年   1212篇
  2001年   1023篇
  2000年   601篇
  1999年   551篇
  1998年   1387篇
  1997年   913篇
  1996年   654篇
  1995年   446篇
  1994年   332篇
  1993年   366篇
  1992年   197篇
  1991年   157篇
  1990年   153篇
  1989年   138篇
  1988年   136篇
  1987年   114篇
  1986年   115篇
  1985年   156篇
  1984年   89篇
  1983年   91篇
  1982年   85篇
  1981年   103篇
  1980年   99篇
  1979年   61篇
  1978年   54篇
  1977年   107篇
  1976年   203篇
  1975年   52篇
  1973年   53篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The influence of ointment formulation on the stability, the in-vitro release and the in-vivo absorption through the skin of rabbits was investigated. The choice of the selected ointments has no influence on the drug stability with the exception of an acidified emulsion base. A good correlation between in-vitro release and in-vivo absorption was found revealing that metronidazole was quickly released and effectively absorbed from a polyethylene glycol base.  相似文献   
62.
Some zirconia-supported vanadium oxides have been prepared by sol-gel method and characterized by different techniques. The vanadium content exerts an effect on the area and pore-size of precursors and samples calcined. The presence of vanadium also affects the decomposition of precursors into ZrO2 and to its phase transformation, as well as the formation of fibres, as shown by SEM-EDX. XPS analyses show the presence of two species of vanadium at the surface, V5– and V4+, the percentage of each one depending on the load of vanadium in the catalyst.  相似文献   
63.
Eighty-four patients with locally advanced, non metastatic squamous cell carcinoma of head and neck or esophagus, were included in a multicentric double-blind randomized trial, comparing goralatide (12.5 or 62.5 micrograms/kg/day, d1-d4) to placebo, associated with carboplatin (400 mg/m2, d1) and 5-fluorouracile (1 g/m2/d continuous IV over 96 hours). Haematological toxicity was analysed on 221 cycles of chemotherapy. All but one patient were evaluable because of early death without haematological toxicity. No significant difference was observed for mean nadir of leukocytes, granulocytes, platelets counts and hemoglobin level. Duration of haematological toxicity was no significantly different for the two groups of patients. Anemia and lymphopenia were more frequent in the goralatide treated patients. Clinical and biological tolerability of goralatide was excellent.  相似文献   
64.
We measured basal and pentagastrin-stimulated acid secretion, as well as basal and meal-stimulated plasma gastrin concentration to determine, in 67 patients affected by resistant duodenal ulcer, whether their condition could be related to gastric acid secretion and/or gastrin-related syndromes. We then compared them to 46 duodenal ulcer control patients. The outpatients were investigated consecutively. The resistant duodenal ulcer patients differed from the controls only in their higher complication rates (bleeding or perforation, P < 0.05). We identified five patients in the resistant duodenal ulcer group with Zollinger-Ellison syndrome and 12 with antral G cell hyperfunction, whereas in the control group only one patient was affected by antral G cell hyperfunction. IgG anti-Helicobacter pylori antibodies were positive for the presence of infection in 7 of the hypergastrinaemic patients. When Zollinger-Ellison syndrome or antral G cell hyperfunction were excluded, no differences could be found in gastric acid secretion, or basal and meal-stimulated plasma gastrin levels, between the resistant and control duodenal ulcer patients, except for basal acid hypersecretion (resistant duodenal ulcer 16% vs duodenal ulcer 2% P = 0.0144). In the presence of duodenal ulcer disease resistant to H2-blockers, it is mandatory to measure basal plasma gastrin concentration since it was possible to diagnose the gastrin-related syndromes, Zollinger-Ellison syndrome and antral G cell hyperfunction, in 26% of this group of patients.  相似文献   
65.
The acyclic nucleoside phosphonate analog 9-(2-phosphonylmethoxyethyl)adenine (PMEA) was recently found to be effective as an inhibitor of visna virus replication and cytopathic effect in sheep choroid plexus cultures. To study whether PMEA also affects visna virus infection in sheep, two groups of four lambs each were inoculated intracerebrally with 10(6.3) TCID50 of visna virus strain KV1772 and treated subcutaneously three times a week with PMEA at 10 and 25 mg/kg, respectively. The treatment was begun on the day of virus inoculation and continued for 6 weeks. A group of four lambs were infected in the same way but were not treated. The lambs were bled weekly or biweekly and the leukocytes were tested for virus. At 7 weeks after infection, the animals were sacrificed, and cerebrospinal fluid (CSF) and samples of tissue from various areas of the brain and from lungs, spleen, and lymph nodes were collected for isolation of virus and for histopathologic examination. The PMEA treatment had a striking effect on visna virus infection, which was similar for both doses of the drug. Thus, the frequency of virus isolations was much lower in PMEA-treated than in untreated lambs. The difference was particularly pronounced in the blood, CSF, and brain tissue. Furthermore, CSF cell counts were much lower and inflammatory lesions in the brain were much less severe in the treated lambs than in the untreated controls. The results indicate that PMEA inhibits the propagation and spread of visna virus in infected lambs and prevents brain lesions, at least during early infection. The drug caused no noticeable side effects during the 6 weeks of treatment.  相似文献   
66.
67.
The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties.  相似文献   
68.
Probabilistic Visual Cryptography Schemes   总被引:1,自引:0,他引:1  
  相似文献   
69.
70.
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