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   931篇
  免费   57篇
  国内免费   1篇
  2024年   3篇
  2023年   8篇
  2022年   37篇
  2021年   54篇
  2020年   34篇
  2019年   60篇
  2018年   58篇
  2017年   29篇
  2016年   51篇
  2015年   48篇
  2014年   55篇
  2013年   69篇
  2012年   88篇
  2011年   59篇
  2010年   35篇
  2009年   32篇
  2008年   32篇
  2007年   31篇
  2006年   24篇
  2005年   32篇
  2004年   26篇
  2003年   22篇
  2002年   26篇
  2001年   8篇
  2000年   5篇
  1999年   2篇
  1997年   5篇
  1996年   3篇
  1995年   7篇
  1994年   3篇
  1993年   2篇
  1992年   2篇
  1991年   3篇
  1989年   4篇
  1985年   3篇
  1984年   4篇
  1982年   2篇
  1981年   1篇
  1977年   2篇
  1976年   1篇
  1975年   2篇
  1974年   2篇
  1972年   1篇
  1970年   2篇
  1969年   2篇
  1967年   4篇
  1965年   1篇
  1962年   1篇
  1961年   1篇
  1960年   1篇
排序方式: 共有989条查询结果,搜索用时 83 毫秒
101.
In order to show the alteration of blood pressure in subjects chronically exposed to natural gas containing sulfur compounds, the present study was done. The blood pressure of 94 (43 males, 51 females) of healthy individuals living in the polluted area of Masjid-i-Sulaiman (Khozestan province, southwest of Iran) was measured. The non-parametric Sign test was applied in order to detect differences between the study subjects and the normal mean values according to the sex and age of subjects. Statistical analysis showed that the systolic blood pressure significantly decreased (Z=-2.74; P=0.0031) while the diastolic blood pressure (Z=+2.11; P=0.0174) and heart rate (Z=+3.62; P<0.001) significantly increased in individuals living in the contaminated areas compared with those of normal mean values. The systolic and diastolic blood pressure decreased and increased, respectively, in individuals chronically exposed to natural sour gas containing sulfur compounds.  相似文献   
102.
In marine ecosystems, fluctuations in surface-seawater carbon dioxide (CO2), significantly influence the whole metabolism of marine algae, especially during the early stages of macroalgal development. In this study, the response of the green alga Ulva fasciata for elevating ocean acidification was investigated using four levels of pCO2 ~ 280, 550, 750 and 1050 µatm. Maximum growth rate (6.6% day−1), protein (32.43 %DW) and pigment (2.9 mg/g) accumulation were observed at pCO2-550 with an increase of ~2-fold compared to control. On the other hand, lipid and carbohydrate contents recorded their maximum production (4.23 and 46.96 %DW, respectively) at pCO2-750 while control showed 3.70 and 42.37 %DW, respectively. SDS-PAGE showed the presence of unique bands in response to pCO2, especially at 550 µatm. Dominant associated bacteria was shifted from Halomonas hydrothermalis of control to Vibrio toranzoniae at pCO2-1050. These findings suggest that ocean acidification at 550 µatm might impose noticeable effects on growth, protein, pigments, and protein profile of U. fasciata, which could be a good source for fish farming. While, pCO2-750 was recommended for energetic purpose, due to its high lipid and carbohydrate contents.  相似文献   
103.
BACKGROUND: The vibrational characteristics of any object are directly dependent on the physical properties of that object. Therefore, changing the physical properties of an object will cause the object to adopt changed natural frequencies. A fracture in a bone results in the loss of mechanical stability of the bone. This change in mechanical properties of a bone should result in a change of the resonant frequencies of that bone. A vibrational method for bone evaluation has been introduced. METHOD OF APPROACH: This method uses the radiation force of focused amplitude-modulated ultrasound to exert a vibrating force directly, and remotely, on a bone. The vibration frequency is varied in the range of interest to induce resonances in the bone. The resulting bone motion is recorded and the resonance frequencies are determined. Experiments are conducted on excised rat femurs and resonance frequencies of intact, fractured, and bonded (simulating healed) bones are measured. RESULTS: The experiments demonstrate that changes in the resonance frequency are indicative of bone fracture and healing, i.e., the fractured bone exhibits a lower resonance frequency than the intact bone, and the resonance frequency of the bonded bone approaches that of the intact bone. CONCLUSION: It is concluded that the proposed radiation force method may be used as a remote and noninvasive tool for monitoring bone fracture and healing process, and the use of focused ultrasound enables one to selectively evaluate individual bones.  相似文献   
104.
105.
106.
The main aim of the present study was to investigate the association between several genetic polymorphisms (in glutathione S-transferase members and DNA repair genes) and clinical response to chemotherapy in locally advanced breast cancer. A sequential series of 101 patients were prospectively included in this study. Clinical assessment of treatment was accomplished by comparing initial tumor size with preoperative tumor size using revised RECIST guideline (version 1.1). Clinical response was regarded as a response or no response. There was no difference between non-responders and responders for the prevalence of genotypes of the study polymorphisms.  相似文献   
107.
Burkholderia cenocepacia is an opportunistic pathogen that causes chronic infection and induces progressive respiratory inflammation in cystic fibrosis patients. Recognition of bacteria by mononuclear cells generally results in the activation of caspase-1 and processing of IL-1β, a major proinflammatory cytokine. In this study, we report that human pyrin is required to detect intracellular B. cenocepacia leading to IL-1β processing and release. This inflammatory response involves the host adapter molecule ASC and the bacterial type VI secretion system (T6SS). Human monocytes and THP-1 cells stably expressing either small interfering RNA against pyrin or YFP-pyrin and ASC (YFP-ASC) were infected with B. cenocepacia and analyzed for inflammasome activation. B. cenocepacia efficiently activates the inflammasome and IL-1β release in monocytes and THP-1. Suppression of pyrin levels in monocytes and THP-1 cells reduced caspase-1 activation and IL-1β release in response to B. cenocepacia challenge. In contrast, overexpression of pyrin or ASC induced a robust IL-1β response to B. cenocepacia, which correlated with enhanced host cell death. Inflammasome activation was significantly reduced in cells infected with T6SS-defective mutants of B. cenocepacia, suggesting that the inflammatory reaction is likely induced by an as yet uncharacterized effector(s) of the T6SS. Together, we show for the first time, to our knowledge, that in human mononuclear cells infected with B. cenocepacia, pyrin associates with caspase-1 and ASC forming an inflammasome that upregulates mononuclear cell IL-1β processing and release.  相似文献   
108.
The genes involved in DNA repair system play a crucial role in the protection against mutations. It has been hypothesized that functional deficiencies in highly conserved DNA repair processes resulting from polymorphic variation may increase genetic susceptibility to breast cancer (BC). The aim of the present study was to evaluate the association of genetic polymorphisms in 2 DNA repair genes, XPD (Asp312Asn) and XRCC1 (A399G), with BC susceptibility. We further investigated the potential combined effect of these DNA repair variants on BC risk. Both XPD (xeroderma pigmentosum group D) and XRCC1 (X-ray repair cross-complementing group 1) polymorphisms were characterized in 100 BC Egyptian females and 100 healthy women who had no history of any malignancy by amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) method and PCR with confronting two-pair primers (PCR-CTPP), using DNA from peripheral blood in a case control study. Our results revealed that the frequencies of AA genotype of XPD codon 312 polymorphism were significantly higher in the BC patients than in the normal individuals (P ≤ 0.003), and did not observe any association between the XRCC1 Arg399Gln polymorphism and risk of developing BC. Also, no association between both XPD Asp312Asn and XRCC1 A399G polymorphisms and the clinical characteristics of disease. Finally, the combination of AA(XPD) + AG(XRCC1) were significantly associated with BC risk. Our results suggested that, XPD gene is an important candidate gene for susceptibility to BC. Also, gene–gene interaction between XPD(AA) + XRCC1(AG) polymorphism may be associated with increased risk of BC in Egyptian women.  相似文献   
109.
110.
Response surface methodology (RSM) based on central composite rotatable design was used to investigate the effects of operating variable, mainly, pH, weight of biomass, and initial lead ion concentration on the lead adsorption capacity at ambient temperature using dried cells of Lactobacillius bulgaricus. Using RSM, quadratic polynomial equation was obtained for predicting the percent of lead ion removal. Analysis of variance showed that the effects of pH and weight of dried biomass were concluded to be the key factors influencing the capacity of lead ion removal. At pH lower than 2 (high acidic condition) and in alkaline condition, there is no significant biosorption. The optimum percent of lead ion removal was found at pH of 6.78, biomass concentration of 6.58 g/l and initial lead concentration 36.22 ppm. In this condition, percent of lead ion removal was 86.21%. This study showed RSM effectiveness for modeling of biosorption process.  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