全文获取类型
收费全文 | 25716篇 |
免费 | 1400篇 |
国内免费 | 1657篇 |
专业分类
28773篇 |
出版年
2024年 | 224篇 |
2023年 | 350篇 |
2022年 | 826篇 |
2021年 | 1311篇 |
2020年 | 961篇 |
2019年 | 1094篇 |
2018年 | 1046篇 |
2017年 | 769篇 |
2016年 | 1092篇 |
2015年 | 1480篇 |
2014年 | 1741篇 |
2013年 | 1911篇 |
2012年 | 2268篇 |
2011年 | 1930篇 |
2010年 | 1178篇 |
2009年 | 1021篇 |
2008年 | 1206篇 |
2007年 | 1068篇 |
2006年 | 928篇 |
2005年 | 812篇 |
2004年 | 694篇 |
2003年 | 629篇 |
2002年 | 547篇 |
2001年 | 483篇 |
2000年 | 417篇 |
1999年 | 403篇 |
1998年 | 254篇 |
1997年 | 270篇 |
1996年 | 257篇 |
1995年 | 242篇 |
1994年 | 220篇 |
1993年 | 136篇 |
1992年 | 206篇 |
1991年 | 146篇 |
1990年 | 130篇 |
1989年 | 109篇 |
1988年 | 73篇 |
1987年 | 94篇 |
1986年 | 56篇 |
1985年 | 54篇 |
1984年 | 43篇 |
1983年 | 31篇 |
1982年 | 30篇 |
1981年 | 19篇 |
1980年 | 8篇 |
1979年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
12.
Yafei Tian Yongping Zhang Shaoyan Hu Lilan Yao Yijian Zhu Shenglong Qiao Daru Lu Junjie Fan 《Blood and Genomics》2021,664(1):63-67
MYH9-related diseases (MYH9-RD) are a group of autosomal dominant diseases caused by mutations in the MYH9 gene, which are featured by thrombocytopenia, giant platelets and granulocyte cytoplasmic inclusion bodies. MYH9-RD patients generally suffer from bleeding syndromes, progressive kidney disease, deafness, or cataracts. Here, we reported on a case of MYH9-RD. A novel heterozygous mutation of MYH9 (c.2344-2345delGTinsTA, p.T782Y) was discovered by targeted sequencing technology. Immunofluorescence analysis of neutrophils confirmed abnormal aggregation of MYH9 protein. The results of this study should expand the MYH9 gene mutation spectrum and provide reference for subsequent researchers and genetic counseling. 相似文献
13.
Micropropagated apple plants of semi-dwarf rootstock M26 (M26) and vigorous
cultivar Gravenstein (GR) on their own roots and different micrograft
combinations were used in the experiment. The combinations included GR
scion on GR root (GR/GR), M26 on M26 (M26/M26), GR on M26 (GR/M26), and M26
on GR (M26/GR). The plants were grown under non-limiting and limiting
relative addition rates of nutrients. Under non-limiting nutrient
conditions, M26 and GR showed a similar relative growth rate
(RGR). Grafting reduced RGR
significantly in the combination of M26/M26 compared to M26. The relative
growth rate for the combination of GR/M26 was similar to the GR/GR plants,
but it increased greatly compared to the M26/M26 plants. For the reverse
combination of M26/GR, the RGR value decreased
significantly compared to either the M26/M26 or the GR/GR plants. The
RGR value and specific root length were lower for
M26/GR than for GR/M26. No clear relationship between carbohydrate
allocation and growth parameters of different plants was found under
non-limiting nutrient conditions. Nutrient limitation resulted in increased
dry weights and soluble sugars in the roots for all plants except for
M26/GR. A reduced leaf area ratio and a lower RGR than
the set relative addition rate of nitrogen were found for M26 and GR/M26
under limiting conditions. These results suggest that the dwarfing effect
is not directly related to RGR of rootstocks or
scions, but rather associated with root morphology of grafted plants and
the ability of roots to absorb nutrients. 相似文献
14.
Organic Solar Cells: Following the Morphology Formation In Situ in Printed Active Layers for Organic Solar Cells (Adv. Energy Mater. 1/2016) 下载免费PDF全文
15.
Molecular mapping of genomic regions underlying barley yellow dwarf tolerance in cultivated oat (Avena sativa L.) 总被引:2,自引:0,他引:2
Zhu S Kolb FL Kaeppler HF 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2003,106(7):1300-1306
Barley yellow dwarf (BYD) is one of the most important viral diseases in small grains, including oat (Avena sativa L.). Breeding for BYD tolerance is an effective and efficient means to control the disease. Characterization of major sources of tolerance, and identification of marker and the trait associations, will directly benefit breeding for BYD tolerance. Genomic regions underlying BYD tolerance were mapped and characterized in an oat population consisting of 152 recombinant inbred lines from the cross of 'Ogle' (tolerant)/MAM17-5 (sensitive). Tolerance was evaluated in replicated field trials across 2 years under artificial inoculation with viruliferous aphids harboring BYD virus isolate PAV-IL. Composite interval mapping was used for quantitative trait loci (QTLs) analysis with a framework map consisting of 272 molecular markers. Four QTLs, BYDq1, BYDq2, BYDq3 and BYDq4, for BYD tolerance were identified on linkage groups OM1, 5, 7 and 24, respectively. All but BYDq2 were consistently detected across both years. Significant epistasis was found between some QTLs. The final model including the epistatic effect explained 50.3 to 58.2% of the total phenotypic variation for BYD tolerance. Some QTLs for BYD tolerance were closely linked to QTLs for plant height and days to heading. Potential problems with QTL mapping for BYD tolerance have been discussed. The identified association of markers and tolerance should be useful to pyramid favorable alleles for BYD tolerance into individual oat lines. 相似文献
16.
The construction of inulin-assimilating and sorbitol-producing fusants was achieved by intergeneric protoplast fusion between Kluyveromyces sp. Y-85 and Saccharomyces cerevisiae E-15. The cells of parental strains were pretreated with 0.1% EDTA (w/v) and 2-mercaptoethanol (0.1%, v/v) and then exposed to 2.0% (w/v) Zymolase at 30 °C for 30–40 min. The optimized fusion condition demonstrated that with the presence of 30% (w/v) polyethylene glycol 6000 (PEG-6000) and 10 mM CaCl2 for 30 min, the fusion frequency reached 2.64 fusants/106 parental cells. The fusants were screened by different characters between two parental strains and further identified by DNA contents, inulinase activity and sorbitol productivity. One of the genetically stable fusants, Strain F27, reached a maximal sorbitol production of 4.87 g/100 ml under optimal fermentation condition. 相似文献
17.
Han Xu Xubin Pan Yun Song Ying Huang Minmin Sun Shuifang Zhu 《Biodiversity and Conservation》2014,23(10):2637-2643
Alien species are brought into countries world wide on a massive scale for agricultural production, ex situ conservation, landscape aesthetics, gardens, and ecosystem restoration. Unfortunately, some of these species have escaped and adversely impacted on regional as well as global biodiversity conservation and agricultural production. To reduce such risks, it is necessary to implement specific and effective measures. Since various government departments and institutions are involved in the management of alien species, it is difficult to prevent native and agroecosystems from being invaded by invited species. We propose the establishment of a supervision and inspection continuum over intentional species introduction, similar to that which exists in some countries over unintentional species introductions. Namely, a justification of the necessity to import, a risk assessment, assurances as to provision of an adequate containment facility assessment, and a damage-limitation protocol should that need to be invoked. These requirements should be satisfied before an alien species is knowingly imported, and the necessary follow-up supervision is important post- importation. 相似文献
18.
Age determination is the basis of determining the postmortem interval using necrophagous fly larvae. To explore the potential of using cuticular hydrocarbons for determining the ages of fly larvae, changes of cuticular hydrocarbons in developing larvae of Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae) were investigated using gas chromatography with flame-ionization detection and gas chromatography-mass spectrometry. This study showed that the larvae produced cuticular hydrocarbons typical of insects. Most of the hydrocarbons identified were alkanes with the carbon chain length of 21-31, plus six kinds of alkenes. The hydrocarbon composition of the larvae correlated with age. The statistical results showed that simple peak ratios of n-C29 divided by another eight selected peaks increased significantly with age; their relationships with age could be modelled using exponential or power functions with R(2) close to or > 0.80. These results suggest that cuticular hydrocarbon composition is a useful indicator for determining the age of larval C. rufifacies, especially for post-feeding larvae, which are difficult to differentiate by morphology. 相似文献
19.
20.
Xiaofei Feng Kangxian Li Fangming Tan Mei Zhu Jieyi Zhou Yongjun Lai Lingfeng Zeng Yingting Ye Jing Huang Xiaosong Wu Shasha Li 《Biochemistry and Biophysics Reports》2018
ObjectiveThe objective of the present study was to investigate the hepatoprotective role of Radix Fici Hirtae on acute alcohol-induced liver injury in mice.MethodsThe component of Radix Fici Hirtae was extracted using petroleum ether, chloroform, ethyl acetate and n-butanol and divided into three dose groups of high, medium and low according to the clinical man's normal dose of the 50 g crude drug/d (0.83 g/kg body weight). Saline in concentration of 10 mg/mL, 5 mg/mL and 2.5 mg/mL and a dose of mouse lavage (0.2 mL/10 g mouse body weight) were added to the solution. Histopathlogical analysis of liver was performed. Finally, liver protection was validated by examining the effect of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AKP), and lactate dehydrogenase (LDH) on the hepatic function of mice in alcohol-induced liver injury model.ResultsExcept for group with saturated n-butyl alcohol, for the rest of the groups, pathological changes of hepatic lipid and inflammatory cells infiltration were alleviated and liver sinus was normal. As compared to model group, the concentrations of AST, ALT, AKP and LDH in chloroform groups and ethyl acetate groups were significantly decreased.ConclusionsExtracts of Radix Fici Hirtae are effective for the prevention of alcohol-induced hepatic damage in mice. The results revealed that extracts of Radix Fici Hirtae could be used as hepatoprotective agent. 相似文献