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   12116篇
  免费   776篇
  国内免费   8篇
  12900篇
  2024年   22篇
  2023年   49篇
  2022年   152篇
  2021年   232篇
  2020年   131篇
  2019年   205篇
  2018年   295篇
  2017年   244篇
  2016年   424篇
  2015年   615篇
  2014年   745篇
  2013年   797篇
  2012年   1066篇
  2011年   1042篇
  2010年   648篇
  2009年   498篇
  2008年   787篇
  2007年   674篇
  2006年   611篇
  2005年   558篇
  2004年   570篇
  2003年   452篇
  2002年   360篇
  2001年   355篇
  2000年   327篇
  1999年   227篇
  1998年   89篇
  1997年   77篇
  1996年   49篇
  1995年   48篇
  1994年   38篇
  1993年   29篇
  1992年   83篇
  1991年   54篇
  1990年   44篇
  1989年   48篇
  1988年   27篇
  1987年   28篇
  1986年   21篇
  1985年   23篇
  1984年   13篇
  1983年   15篇
  1982年   12篇
  1981年   12篇
  1980年   11篇
  1979年   9篇
  1978年   15篇
  1975年   13篇
  1974年   11篇
  1970年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.

1. 1. The objective of this paper is to investigate the indoor environment from the viewpoint of interaction between physical environment and the human responses. The field survey has been conducted over 1 year.

2. 2. A continuous measurement has been carried out for 1 week and distribution of variables have been measured for 1 day.

3. 3. The attitude of workers was investigated by a questionnaire.

4. 4. As the result, average luminance represented more than 1000 lx in the new building, in contrast with less tha 300 lx in the existing building.

5. 5. There was a significant difference of the occupants' response to the light environment between the two buildings.

6. 6. Measured thermal conditions are on the edge of the ASHRAE comfort envelope in summer, and in the neighborhood of the lower dry limit of the envelope in spring.

7. 7. The occupants' evaluations were remarkably changed before and after the moving. The office environment is better than that of the factory.

Author Keywords: Office; post occupancy evaluation; physical environmental condition; occupants' evaluation  相似文献   

52.
Song  Hyerin  Lee  Won-Kyu  Lee  Jihye  Lee  Seung-Hyun  Song  Young Min  Kim  Kyujung  Choi  Jun-Hyuk 《Plasmonics (Norwell, Mass.)》2020,15(4):941-948

The angle-variable tunable optical filter was strictly fabricated by two strategies of nanoimprint-coupled metal nanopatterning with improved cost-effectiveness and accessibility. The tunable optical properties and the performances of two strategies were experimentally examined and turned out to be well matched to numerical results. Tunable properties are obtained by three factors: size of fabricated Ag nanodisks, incident illumination angle, and fabrication strategies. The resonant extinction peak shifts were identified to show a large increase along with the increase in fabricated Ag disk size and increase in the incidence angle of illumination. When comparing a fabrication strategy, it was confirmed that the sample fabricated by the strip-off method has better stability on color changes with a consistent dependency on the incident angle. The presented strategies of fabrication are technically viable for obtaining well-defined plasmonic nanostructures so that it has the feasibility to apply for fascinating optical applications including display or tunable optical filters.

  相似文献   
53.
Melanoma can develop in a congenital melanocytic nevus (CMN). In fact, a large CMN is associated with a high risk of developing melanoma. Although melanomas arising from CMNs are thought to have a pathogenesis distinct from conventional melanomas, no studies have been conducted on the evolution or tumor heterogeneity of CMN melanomas. We applied multi‐region whole‐exome sequencing to investigate the clonal nature of driver events and evolutionary processes in CMNs and melanomas arising from CMNs. In two patients, we observed an independent subclonal evolution in cancerized fields of CMNs and chromosome 8q amplification in both melanomas arising from CMNs. The amplification of MYC, located in chromosome 8q, was correlated with the percentage of tumor cells expressing high levels of MYC protein detected in melanoma cells by immunohistochemistry. Our analysis suggests that each CMN cell may evolve sporadically and that amplification of MYC might be a key event for melanoma development in CMNs.  相似文献   
54.
Biomolecules, especially proteins and nucleic acids, have been widely studied to develop biochips for various applications in scientific fields ranging from bioelectronics to stem cell research. However, restrictions exist due to the inherent characteristics of biomolecules, such as instability and the constraint of granting the functionality to the biochip. Introduction of functional nanomaterials, recently being researched and developed, to biomolecules have been widely researched to develop the nanobiohybrid materials because such materials have the potential to enhance and extend the function of biomolecules on a biochip. The potential for applying nanobiohybrid materials is especially high in the field of bioelectronics. Research in bioelectronics is aimed at realizing electronic functions using the inherent properties of biomolecules. To achieve this, various biomolecules possessing unique properties have been combined with novel nanomaterials to develop bioelectronic devices such as highly sensitive electrochemical‐based bioelectronic sensing platforms, logic gates, and biocomputing systems. In this review, recently reported bioelectronic devices based on nanobiohybrid materials are discussed. The authors believe that this review will suggest innovative and creative directions to develop the next generation of multifunctional bioelectronic devices.  相似文献   
55.
Molecular Biology Reports - Plant-derived phytochemicals such as flavonoids have been explored to be powerful antioxidants that protect against oxidative stress-related diseases. In the present...  相似文献   
56.
Kim  Juseok  Kim  Joon Yong  Song  Hye Seon  Kim  Yeon Bee  Whon  Tae Woong  Ahn  Seung Woo  Lee  Se Hee  Yoo  SeungRan  Kim  Yu Jin  Myoung  Jinjong  Choi  Yoon-E  Son  Hong-Seok  Roh  Seong Woon 《Antonie van Leeuwenhoek》2021,114(5):507-513

Strain CBA3638T was isolated from the Geum River sediment, Republic of Korea. The cells of strain CBA3638T were Gram-stain-positive, strictly anaerobic, rod-shaped, and 0.5–1.0 μm wide, and 4.0–4.5 μm long. Optimal growth occurred at 37 °C, pH 7.0, and 1.0% (w/v) NaCl. Based on the 16S rRNA gene sequence, the phylogenetic analysis showed that strain CBA3638T belongs to the genus Anaerocolumna in the family Lachnospiraceae, and is most closely related to Anaerocolumna cellulosilytica (94.6–95.0%). The DDH value with A. cellulosilytica SN021T showed 15.0% relatedness. The genome of strain CBA3638T consisted of one circular chromosome that is 5,500,435 bp long with a 36.7 mol% G?+?C content. The genome contained seven 16S-5S-23S rRNA operons and one antibiotic resistance-related transporter gene (mefA). Quinones were not detected. The predominant cellular fatty acids were C16:0 and C14:0 and the polar lipids were diphosphatidylglycerol, phosphatidylcholine, and uncharacterised polar lipids. Based on the polyphasic taxonomic analysis, we propose strain CBA3638T as a novel species in the genus Anaerocolumna, with the name Anaerocolumna sedimenticola sp. nov. The type strain is CBA3638T (=?KACC 21652T?=?DSM 110663T).

  相似文献   
57.
Oak (Quercus spp.) and hornbeam (Carpinus spp.) are one of dominant tree species in East Asian temperate broad leaf deciduous forests and many insect species, including more than 65% of Lepidoptera species, feed on these trees. We sampled lepidopteran caterpillars from two 0.1 ha plots in a temperate forest to investigate the role of dominant trees (oaks and hornbeams) in herbivore community. In total, we identified 738 caterpillars from 223 Lepidopteran species on 34 tree species. Most caterpillar species were from species-rich families such as Geometridae 25% (56 spp.), Noctuidae, and Tortricidae. After excluding dominant trees, plant-herbivore network analyses showed increased network specialization and nestedness and decreased generality and vulnerability. These results suggest that oaks and hornbeams support a large Lepidopteran herbivore community, and co-occurring plant species support diverse but specific herbivores. Geographical distribution and plant community are closely related to diversity of the herbivore community. Future work is needed to investigate the likelihood that specialist herbivores become relatively more abundant in the forest as oaks are succeeded by hornbeams.  相似文献   
58.
Determine if sex differences exist in clinical characteristics and outcomes of adults hospitalized for coronavirus disease 2019 (COVID-19) in a US healthcare system. Case series study. Sequentially hospitalized adults admitted for COVID-19 at two tertiary care academic hospitals in New Orleans, LA, between 27 February and 15 July 2020. Measures included demographics, comorbidities, presenting symptoms, and laboratory results. Outcomes included intensive care unit admission (ICU), invasive mechanical ventilation (IMV), and in-hospital death. We included 776 patients (median age 60.5 years; 61.4% women, 75% non-Hispanic Black). Rates of ICU, IMV, and death were similar in both sexes. In women versus men, obesity (63.8 vs 41.6%, P < 0.0001), hypertension (77.6 vs 70.1%, P = 0.02), diabetes (38.2 vs 31.8%, P = 0.06), chronic obstructive pulmonary disease (COPD, 22.1 vs 15.1%, P = 0.015), and asthma (14.3 vs 6.9%, P = 0.001) were more prevalent. More women exhibited dyspnea (61.2 vs 53.7%, P = 0.04), fatigue (35.7 vs 28.5%, P = 0.03), and digestive symptoms (39.3 vs 32.8%, P = 0.06) than men. Obesity was associated with IMV at a lower BMI (> 35) in women, but the magnitude of the effect of morbid obesity (BMI ≥ 40) was similar in both sexes. COPD was associated with ICU (adjusted OR (aOR), 2.6; 95%CI, 1.5–4.3) and IMV (aOR, 1.8; 95%CI, 1.2–3.1) in women only. Diabetes (aOR, 2.6; 95%CI, 1.2–2.9), chronic kidney disease (aOR, 2.2; 95%CI, 1.3–5.2), elevated neutrophil-to-lymphocyte ratio (aOR, 2.5; 95%CI, 1.4–4.3), and elevated ferritin (aOR, 3.6; 95%CI, 1.7–7.3) were independent predictors of death in women only. In contrast, elevated D-dimer was an independent predictor of ICU (aOR, 7.3; 95%CI, 2.7–19.5), IMV (aOR, 6.5; 95%CI, 2.1–20.4), and death (aOR, 4.5; 95%CI, 1.2–16.4) in men only. This study highlights sex disparities in clinical determinants of severe outcomes in COVID-19 patients that may inform management and prevention strategies to ensure gender equity.  相似文献   
59.
To confirm the beneficial effects of alpha (1,2)-fucosyltransferase (FUT1) M307 A on piglet survival on commercial farms, we performed PCR-RFLP analysis of FUT1 M307 in successfully marketed (n = 245) and disease affected/deceased pigs during weaning (n = 252) at a commercial farm. We also evaluated the FUT1 genotypes of 190 healthy pigs from three different genetic backgrounds. The distribution of genotypes differed between the successfully marketed and disease affected/deceased pig groups. The frequency of the A allele, associated with resistance to edema and post-weaning diarrhea, was higher in the post-weaning survival group (0.21) than in the non-survival group (0.16, P < 0.05). The odds ratio for piglet survival between AA and GG genotypes was 1.98; thus, piglet survival for individuals with the AA genotype was almost two-fold greater than for GG individuals. The FUT1 gene polymorphism can be used as an effective marker for selection programs to improve post-weaning piglet survival.  相似文献   
60.
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