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   340篇
  免费   24篇
  国内免费   2篇
电工技术   10篇
综合类   2篇
化学工业   88篇
金属工艺   5篇
机械仪表   10篇
建筑科学   13篇
能源动力   10篇
轻工业   50篇
水利工程   1篇
无线电   22篇
一般工业技术   45篇
冶金工业   55篇
原子能技术   2篇
自动化技术   53篇
  2022年   9篇
  2021年   18篇
  2020年   13篇
  2019年   4篇
  2018年   9篇
  2017年   10篇
  2016年   13篇
  2015年   18篇
  2014年   7篇
  2013年   27篇
  2012年   20篇
  2011年   22篇
  2010年   20篇
  2009年   18篇
  2008年   19篇
  2007年   7篇
  2006年   14篇
  2005年   8篇
  2004年   9篇
  2003年   10篇
  2002年   5篇
  2001年   4篇
  2000年   3篇
  1999年   9篇
  1998年   15篇
  1997年   13篇
  1996年   6篇
  1995年   8篇
  1994年   5篇
  1993年   8篇
  1992年   1篇
  1991年   3篇
  1989年   1篇
  1986年   1篇
  1982年   1篇
  1980年   1篇
  1974年   1篇
  1973年   2篇
  1972年   1篇
  1970年   1篇
  1968年   1篇
  1967年   1篇
排序方式: 共有366条查询结果,搜索用时 15 毫秒
31.
The quality of leafy vegetables has to be guaranteed for consumers over the whole postharvest period, usually limited to 5–7 days. The analyses to evaluate the quality of vegetables are very time- and resource consuming, so the use of qualitative markers can be much useful. The aim of this work was to evaluate the use of thermoluminescence (TL) parameters as qualitative markers of fresh-cut leafy vegetables during the shelf life. TL is a technique consisting of a cooling, followed by the progressive warming, of a preilluminated sample to reveal the different types of charge pairs as successive emission bands, which are resolved better than the corresponding decay phases recorded at constant temperature. Experiments were performed on rocket (Diplotaxis tenuifolia L.) stored at 2 °C for 7 days. During storage, several changes in TL glow curves were found. The position of the peaks showed a shift to higher temperature. The area of the peaks, relating to the photosystem II (20–65 °C), grew up lightly; whereas in the temperature range that detects lipidic peroxidation (65–140 °C), the TL emission became more than twice. These changes demonstrated that, during the shelf life, a progressive destabilization of PSII centres occurred and that lipid peroxidation products were accumulated in membranes. TL could be used to estimate the damages immediately after as well as during the storage period. This is the first time that TL was used to evaluate the quality of fresh-cut vegetables products during the shelf life.  相似文献   
32.
Noninvasive positive pressure ventilation (NPPV) via nasal mask is well known to be effective in the treatment of acute respiratory failure (ARF) secondary to chronic obstructive pulmonary disease (COPD). A case of ARF with hypercapnic coma due to exacerbation of COPD is described. Six hours of conservative therapy with oxygen and medical treatment did not show any result. As endotracheal intubation (ET) was avoided on the basis of advanced age, poor life expectancy of the patient and family wish, NPPV was set up using a pressure triggered ventilator. After 61 hours of uninterrupted NPPV, the acid-base alteration and the lethargic status was fully reversed. The conclusions is drawn that NPPV may be useful also in the treatment of patients affected by severe decompensated hypercapnic respiratory failure in whom ET is not indicated.  相似文献   
33.
Purpura fulminans is a rare form of disseminated intravascular coagulation characterized by rapidly progressive purpuric lesions, hypotension and, in some cases, fever. In neonates, purpura fulminans usually develops following deficiency of anticoagulant protein C or S, although acquired forms have been described. The management of disseminated intravascular coagulation is still controversial, with some studies finding a positive effect of anticoagulants and others showing no effect or even a detrimental one. Therefore, at present, management is limited to the treatment of underlying disease and replacement of clotting factors. Personal experience is reported on the efficacy of heparin in combination with antithrombin III in the treatment of purpura fulminans in two preterm neonates who did not have inherited deficiency of protein C or S and developed the disease possibly following prolonged labor (36 hours) in the first case, and maternal neoplasia, in the second. Both neonates presented with widespread cyanotic areas rapidly evolving in purpuric lesions and hemorrhagic bullae. Laboratory tests (prolonged prothrombin and partial thromboplastin time, fibrinogen and antithrombin III concentrations below normal ranges, d-dimer highly positive) were consistent with disseminated intravascular coagulation. In both cases anticoagulant treatment with heparin (50 UI/kg in bolus followed by 15 UI/kg/h) and antithrombin III was associated with resolution of disseminated intravascular coagulation and prompt amelioration of the purpuric lesions, without apparent side effects.  相似文献   
34.
35.
36.
Data from the Brazilian Agricultural Ministry show that before the implementation of the Brazilian programme of nitrofuran control in February 2003, the cases of contamination of Brazilian chicken by nitrofurans were almost exclusively due to furaltadone. After May 2003, such cases decreased until no more reports of Brazilian chicken contamination with this nitrofuran were reported. Curiously, after April 2003, an increase was observed in the numbers of contaminated samples by semicarbazide, the target metabolite of nitrofurazone. Most Brazilian chicken found to be contaminated with semicarbazide has been covered with flour, salt and spices. For this reason, the authors' laboratory initialized a programme for tracing possible sources of food contamination by semicarbazide. After several semicarbazide positives in flour of controlled origin (results varying between 2.2 and 5.2 microg kg(-1)), the different additives used in the cereal industry as flour improvement agents were studied. The results indicate that the compound azodicarbonamide was responsible for the source of the contaminant semicarbazide.  相似文献   
37.
38.
BACKGROUND: Soilless growth systems, developed mainly for vegetables and ornamental crops, have also been used recently as an alternative to soil culture for table grape in order to achieve optimal production performance. In this study, sensory, physical and chemical parameters were analysed in table grapes obtained from soil and soilless growth systems at harvest and during storage in air or modified atmosphere. RESULTS: At harvest, soilless‐grown berries were 30% firmer than those grown in soil. Moreover, they showed 60% higher antioxidant activity and total phenol content than soil‐grown fruits. Modified atmosphere storage resulted in a better quality of table grapes compared with those stored in air. Furthermore, soilless growth was more suitable than soil growth for preserving visual quality and controlling rachis browning and weight loss. CONCLUSION: Since the soilless system produces berries that are cleaner and of higher quality than those grown in soil, the implementation of soilless growth for the production of health‐promoting and convenience fruits is suggested. Copyright © 2011 Society of Chemical Industry  相似文献   
39.
LC-MS-based shotgun proteomics relies both on the power of the separation techniques and the sensitivity of detection methods. As a viable alternative to classical approaches in this field, we developed a fully automated, comprehensive 2D LC system, in which RPLC × RPLC was coupled to MS detection, for the first time, and applied for the analysis of tryptic digests obtained from α-casein and dephosphorylated α-casein. The use of a significantly different pH in the two dimensions allowed us to attain high peak capacity, despite the employment of novel identical stationary phases. Furthermore, such a combination addresses compatibility issues, thus allowing straightforward interfacing in online 2D LC configuration, as well as direct linkage to a mass spectrometer. A theoretical peak capacity of ca. 8500 was calculated for the setup, employing four serially coupled C18 columns in the first dimension (600 × 2.1 mm, 2.7 μm d.p.), operated under basic conditions, and 3 cm length of the same stationary phase (30 × 4.6 mm, 2.7 μm d.p. column), under acidic conditions, for fast second dimension analysis.  相似文献   
40.
The M1 zinc metalloproteases ERAP1, ERAP2, and IRAP play a role in HLA-I antigen presentation by refining the peptidome either in the ER (ERAP1 and ERAP2) or in the endosomes (IRAP). They have also been entrusted with other, although less defined, functions such as the regulation of the angiotensin system and blood pressure. In humans, ERAP1 and IRAP are commonly expressed. ERAP2 instead has evolved under balancing selection that maintains two haplotypes, one of which undergoing RNA splicing leading to nonsense-mediated decay and loss of protein. Hence, likewise in rodents, wherein the ERAP2 gene is missing, about a quarter of the human population does not express ERAP2. We report here that macrophages, but not monocytes or other mononuclear blood cells, express and secrete an ERAP2 shorter form independent of the haplotype. The generation of this “short” ERAP2 is due to an autocatalytic cleavage within a distinctive structural motif and requires an acidic micro-environment. Remarkably, ERAP2 “short” binds IRAP and the two molecules are co-expressed in the endosomes as well as in the cell membrane. Of note, the same phenomenon could be observed in some cancer cells. These data prompt us to reconsider the role of ERAP2, which might have been maintained in humans due to fulfilling a relevant function in its “short” form.  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