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   2768篇
  免费   186篇
  国内免费   9篇
  2023年   36篇
  2022年   22篇
  2021年   87篇
  2020年   53篇
  2019年   64篇
  2018年   95篇
  2017年   83篇
  2016年   115篇
  2015年   172篇
  2014年   184篇
  2013年   207篇
  2012年   263篇
  2011年   234篇
  2010年   163篇
  2009年   115篇
  2008年   133篇
  2007年   143篇
  2006年   121篇
  2005年   104篇
  2004年   90篇
  2003年   69篇
  2002年   76篇
  2001年   43篇
  2000年   50篇
  1999年   39篇
  1998年   16篇
  1997年   19篇
  1996年   17篇
  1995年   8篇
  1994年   10篇
  1993年   4篇
  1992年   11篇
  1991年   12篇
  1990年   12篇
  1989年   12篇
  1988年   12篇
  1987年   8篇
  1985年   4篇
  1984年   6篇
  1983年   7篇
  1982年   2篇
  1981年   7篇
  1980年   5篇
  1979年   3篇
  1977年   3篇
  1975年   3篇
  1974年   4篇
  1973年   5篇
  1972年   2篇
  1968年   2篇
排序方式: 共有2963条查询结果,搜索用时 281 毫秒
1.
2.
Multiple HindIII-restriction fragments of Salmonella typhimurium and Salmonella typhi chromosomal DNA exhibited homology with the heat-labile enterotoxin (LT1) gene of Escherichia coli as determined by Southern blot analysis. A 9.4 kb HindIII restriction fragment identified in S. typhimurium and S. typhi chromosomal DNA reacted with both eltA and eltB gene probes. However, the homology of the 9.4 kb DNA fragment from these Salmonella species was greater with eltB than eltA. In addition, a synthetic oligonucleotide probe, made to a portion of the putative GM1-ganglioside binding region of cholera toxin (CT) and LT1, hybridized with the 9.4 kb DNA fragment of S. typhimurium but not with the 9.4 kb fragment found in S. typhi isolates. The hybridization of multiple restriction fragments of Salmonella DNA with eltA and eltB gene sequences further suggests duplication of the stx operon on the chromosome of these bacteria.  相似文献   
3.
Recent investigations have showed that the functional thermogenic adipocytes are present in both infants and adult humans. Accumulating evidence suggests that the coexistence of classical and inducible brown (brite) adipocytes in humans at adulthood and these adipocytes function to generate heat from energy resulting in reducing body fat and improving glucose metabolism. Human thermogenic adipocytes can be differentiated in vitro from stem cells, cell lines, or adipose stromal vascular fraction. Pre-activated human brite adipocytes in vitro can maintain their thermogenic function in normal or obese immunodeficient mice; therefore, they improve glucose homeostasis and reduce fat mass in obese animals. These key findings have opened a new door to use in vitro thermogenic adipocytes as a cell therapy to prevent obesity and related disorders. Thus, this paper intends to highlight our knowledge in aspects of in vitro human brite/brown adipocytes for the further studies.  相似文献   
4.
Through Genome Wide Association Studies (GWAS) many Single Nucleotide Polymorphism (SNP)-complex disease relations can be investigated. The output of GWAS can be high in amount and high dimensional, also relations between SNPs, phenotypes and diseases are most likely to be nonlinear. In order to handle high volume-high dimensional data and to be able to find the nonlinear relations we have utilized data mining approaches and a hybrid feature selection model of support vector machine and decision tree has been designed. The designed model is tested on prostate cancer data and for the first time combined genotype and phenotype information is used to increase the diagnostic performance. We were able to select phenotypic features such as ethnicity and body mass index, and SNPs those map to specific genes such as CRR9, TERT. The performance results of the proposed hybrid model, on prostate cancer dataset, with 90.92% of sensitivity and 0.91 of area under ROC curve, shows the potential of the approach for prediction and early detection of the prostate cancer.  相似文献   
5.
The Indochinese silvered langur (Trachypithecus germaini) is distributed to the west of Mekong River in Cambodia, Lao PDR, Thailand and Vietnam. During a two‐year study, from May 2014 to May 2016, we collected 320.44 hr of behavior, with 17,040 feeding bouts recorded (142 hr) for T. germaini on Chua Hang Karst Mountain, Kien Luong District, Kien Giang Province, Vietnam. Feeding accounted for 45% of the Indochinese silvered langurs’ activity budget. The plant diet of the Indochinese silvered langurs was principally composed of young leaves (58%), followed by mature leaves (9.5%), fruits (22.7%), flowers (4.7%), buds (3.3%), petioles (1.2%), and other (0.5%). A total of 58 plant species were fed on by the silvered langurs, and leaves of eight species (Phyllathus reticulatus, Ficus rumphii, Ficus tinctoria, Ficus microcarpa, Cayratia trifolia, Streblus ilicifolia, Combretum latifolium, and Streblus asper) were fed on throughout the year. P. reticulatus was most frequently eaten (13.9% feeding time, n = 1,733). Food selection differed significantly between months and seasons. The Indochinese silvered langurs ate 27 plant species in the wet season compared with 23 plant species in the dry season. Leaf chemical composition of two food categories, 16 eaten species (with 10 most frequently consumed species and six least consumed species), and four noneaten species, were analyzed. Feeding samples from eaten species in the Indochinese silvered langurs's diet contained lower amounts of condensed tannin, lignin, protein, ash, and lipids, but a higher amount of total sugar compared with samples from noneaten species. Furthermore, the most frequently consumed species contained lower amounts of lignin compared with the less frequently consumed species. Using a generalized linear model with five variables, including neutral detergent fiber (NDF), total sugar, lignin, lipid, and calcium (Ca) indicated that NDF positively correlated and lignin content negatively correlated with feeding records in the diet of these langur.  相似文献   
6.
Neutrophils of patients with Beh?et's syndrome generate increased amounts of oxygen free radicals. This phenomenon is inhibited by superoxide dismutase (SOD) and catalase and is implicated in vasculitis. We treated seven patients with active Beh?et's syndrome by CuZn SOD intramuscularis with dramatic improvement of clinical symptoms.  相似文献   
7.
8.
Calli were induced from 300,000 embryos isolated from immature to mature stage of seeds collected on late September from 14 elite trees. When the embryos were cultured onto plastic Petri-dish containing 20 mL of modified B5 basal medium supplemented with 3% (w/v) sucrose, 500 mg/L casein hydrolysate, 250 mg/L myo-inositol, 0.5% (w/v) polyvinyl polypyrrolidon (PVPP), 2×MS vitamins, 0.5 mg/L gibberellic acid, and 10 mg/L 2,4-D after 2 weeks of culture, yellowish-white calli were immediately formed on the surfaces of embryos, and subcultured for 4 weeks in same culture medium. Because most of calli maintained for more than 3 months were revealed differences in their colors, surface texture, and growth rate, visual selection was made for first round screening. When the size of visually selected calli larger than 19 mm in their diameter were inoculated, persistent proliferation was observed. Among the plating methods tested for the selection of rapid growing cell lines at single cell and/or small cell aggregate level, 2-layer spread plating revealed as the best for single cell cloning. To enhance cell growth and maintain high rate of viability for long-term culture of yew cells in bioreactor, final cell volume less than 50% in SCV seemed to be the best. Time course study revealed that 30% of inoculum density was suitable for fed batch culture. Among the tested conditional media, the rate of 1∶2 (old medium: fresh medium) was recorded at the best for cell growth.  相似文献   
9.
10.
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