全文获取类型
收费全文 | 1721篇 |
免费 | 124篇 |
国内免费 | 10篇 |
出版年
2024年 | 2篇 |
2023年 | 23篇 |
2022年 | 45篇 |
2021年 | 67篇 |
2020年 | 40篇 |
2019年 | 31篇 |
2018年 | 51篇 |
2017年 | 47篇 |
2016年 | 72篇 |
2015年 | 86篇 |
2014年 | 88篇 |
2013年 | 122篇 |
2012年 | 164篇 |
2011年 | 157篇 |
2010年 | 98篇 |
2009年 | 64篇 |
2008年 | 88篇 |
2007年 | 72篇 |
2006年 | 74篇 |
2005年 | 63篇 |
2004年 | 71篇 |
2003年 | 46篇 |
2002年 | 45篇 |
2001年 | 36篇 |
2000年 | 30篇 |
1999年 | 24篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1972年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有1855条查询结果,搜索用时 15 毫秒
61.
Michael A. Hardigan Emily Crisovan John P. Hamilton Jeongwoon Kim Parker Laimbeer Courtney P. Leisner Norma C. Manrique-Carpintero Linsey Newton Gina M. Pham Brieanne Vaillancourt Xueming Yang Zixian Zeng David S. Douches Jiming Jiang Richard E. Veilleux C. Robin Buell 《The Plant cell》2016,28(2):388-405
62.
Dae‐Won Ki Maurice Ducret Awouafack Chin Piow Wong Hien Minh Nguyen Quang Minh Thai Lien Huong TonNu Hiroyuki Morita 《化学与生物多样性》2019,16(3)
A new tribromoiododiphenyl ether ( 1 ) and eight known brominated diphenyl ethers ( 2 – 9 ) were isolated from the MeOH extract of the sponge Arenosclera sp. collected in Vietnam, using repeated open column chromatography and preparative thin layer chromatography. The chemical structure of the new compound 1 was determined by analyses of spectroscopic (1D‐ and 2D‐NMR, and MS) data and by comparison of our data with those reported in the literature. Compounds 1 , 3 , and 8 exhibited strong antibacterial activities against the Gram‐positive bacteria Bacillus subtilis and Staphylococcus aureus and the Gram‐negative bacterium Klebsiella pneumoniae with MIC values ranging from 0.8 to 6.3 μm , while compounds 5 and 7 only displayed activities against Gram‐positive bacteria with MIC values from 0.5 to 3.1 μm . Compound 2 showed activities against the four tested bacteria with MIC values ranging from 0.5 to 6.3 μm . 相似文献
63.
Tran Cuong Manh Van Pham Hai Nguyen Hien Thuy Nguyen Thuy Thi Vu Lam Dinh Do Tung Hoang 《Plasmonics (Norwell, Mass.)》2019,14(6):1587-1592
Plasmonics - Since the metamaterial perfect absorber (MPA) is composed of electromagnetic resonance structures, the main operational mechanism of the MPA is electromagnetic resonance. In this work,... 相似文献
64.
Duc Khanh Le Quang Khai Le Thi Thuy Hang Tran Duc Viet Nguyen Thi Hang Dao Thi Thuy Nguyen Xuan Lam Truong Quang Cuong Nguyen Huy Phong Pham Thi Thu Thuy Phan Gajendra Babu Baktavachalam 《Journal of Asia》2019,22(2):493-498
Susceptibility of Asian corn borer (ACB), Ostrinia furnacalis (Guenée) to Bacillus thuringiensis (Bt) Cry1Ab protein was studied between 2015 and 2016 with 11 ACB populations, collected from various geographical regions in Vietnam. A concentration range of Cry1Ab from 0.20 to 26.10 ng/cm2 of diet was evaluated against F1 ACB neonates using diet surface-overlay bioassays. Mortality data was recorded daily until seven days after infestation. Growth inhibition was recorded at the end of seven days. The median lethal concentration (LC50) varied ≈3-fold among the different populations, ranging from 0.58 to 1.83 ng/cm2 of diet with an overall mean of 0.86 ng/cm2 of diet. Even the lowest concentration of 0.20 ng/cm2 caused 73.53% growth inhibition. >90% growth inhibition was achieved at 0.82 ng/cm2 or higher concentrations. The results reflect natural variation in Bt susceptibility among ACB populations rather than variation caused by prior exposure to selection pressures. LC99 value (17.26 ng/cm2) was generated by pooling mortality data across different populations. The upper fiducial limit of LC99 (24.38 ng/cm2) could be a potential diagnostic dose for future resistance monitoring programs. The findings from this study suggest that ACB populations in Vietnam are highly susceptible to Cry1Ab protein. This is the first report of Cry1Ab susceptibility of different ACB populations in Vietnam and will serve as a baseline for future resistance monitoring work. 相似文献
65.
66.
Tsikas D Thum T Becker T Pham VV Chobanyan K Mitschke A Beckmann B Gutzki FM Bauersachs J Stichtenoth DO 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2007,851(1-2):229-239
Dimethylamine [DMA, (CH(3))(2)NH)] is abundantly present in human urine. Main sources of urinary DMA have been reported to include trimethylamine N-oxide, a common food component, and asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthesis. ADMA is excreted in the urine in part unmetabolized and in part after hydrolysis to DMA by dimethylarginine dimethylaminohydrolase (DDAH). Here we describe a GC-MS method for the accurate and rapid quantification of DMA in human urine. The method involves use of (CD(3))(2)NH as internal standard, simultaneous derivatization with pentafluorobenzoyl chloride and extraction in toluene, and selected-ion monitoring of m/z 239 for DMA and m/z 245 for (CD(3))(2)NH in the electron ionization mode. GC-MS analysis of urine samples from 10 healthy volunteers revealed a DMA concentration of 264+/-173 microM equivalent to 10.1+/-1.64 micromol/mmol creatinine. GC-tandem MS analysis of the same urine samples revealed an ADMA concentration of 27.3+/-15.3 microM corresponding to 1.35+/-1.2 micromol/mmol creatinine. In these volunteers, a positive correlation (R=0.83919, P=0.0024) was found between urinary DMA and ADMA, with the DMA/ADMA molar ratio being 10.8+/-6.2. Elevated excretion rates of DMA (52.9+/-18.5 micromol/mmol creatinine) and ADMA (3.85+/-1.65 micromol/mmol creatinine) were found by the method in 49 patients suffering from coronary artery disease, with the DMA/ADMA molar ratio also being elevated (16.8+/-12.8). In 12 patients suffering from end-stage liver disease, excretion rates of DMA (47.8+/-19.7 micromol/mmol creatinine) and ADMA (5.6+/-1.5 micromol/mmol creatinine) were found to be elevated, with the DMA/ADMA molar ratio (9.17+/-4.2) being insignificantly lower (P=0.46). Between urinary DMA and ADMA there was a positive correlation (R=0.6655, P<0.0001) in coronary artery disease, but no correlation (R=0.27339) was found in end-stage liver disease. 相似文献
67.
Distribution dynamics of the Tnt1 retrotransposon in tobacco 总被引:1,自引:0,他引:1
Le QH Melayah D Bonnivard E Petit M Grandbastien MA 《Molecular genetics and genomics : MGG》2007,278(6):639-651
Retrotransposons contribute significantly to the size, organization and genetic diversity of plant genomes. Although many
retrotransposon families have been reported in plants, to this day, the tobacco Tnt1 retrotransposon remains one of the few
elements for which active transposition has been shown. Demonstration that Tnt1 activation can be induced by stress has lent
support to the hypothesis that, under adverse conditions, transposition can be an important source of genetic variability.
Here, we compared the insertion site preference of a collection of newly transposed and pre-existing Tnt1 copies identified
in plants regenerated from protoplasts or tissue culture. We find that newly transposed Tnt1 copies are targeted within or
close to host gene coding sequences and that the distribution of pre-existing insertions does not vary significantly from
this trend. Therefore, in spite of their potential to disrupt neighboring genes, insertions within or near CDS are not preferentially
removed with age. Elimination of Tnt1 insertions within or near coding sequences may be relaxed due to the polyploid nature
of the tobacco genome. Tnt1 insertions within or near CDS are thus better tolerated and can putatively contribute to the diversification
of tobacco gene function.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
68.
69.
Nguyen Mai Cao Hoang Phuong Lan Pham Van Huan Nguyen Huu Thong Duy-Hung Nguyen Nguyen Duc Trung Kien Chu Manh Nhuong Cao Xuan Thang Vuong-Hung Pham 《Luminescence》2022,37(4):577-587
A series of Mn2+-doped zinc germinate ZGO:xMn2+ (x = 0–0.05) nanorods was synthesized successfully using a hydrothermal method. XRD revealed that crystal phases of the ZGO:xMn2+ were rhombohedral and in the R-3 space group. The Williamson–Hall equation was also used to explain the strain, nanocrystalline size, and stacking fault. Green LEDs were successfully fabricated by coating ZGO:Mn2+ nanorods onto UV-LED chips. For high color purity, CIE of the fabricated green LEDs were (0.2404, 0.5428), which made this material a promising candidate for fabrication of UV-based green LEDs. 相似文献
70.
ABSTRACTIn this work, with Ni (110) as a model catalyst surface and CO2 as an adsorbate, a performance study of Density Functional Theory methods (functionals) is performed. CO being a possible intermediate in CO2 conversion reactions, binding energies of both, CO2 and CO, are calculated on the Ni surface and are compared with experimental data. OptPBE-vdW functional correctly predicts CO2 binding energy on Ni (?62?kJ/mol), whereas CO binding energy is correctly predicted by the rPBE-vdW functional (?138?kJ/mol). The difference in computed adsorption energies by different functionals is attributed to the calculation of gas phase CO2. Three alternate reaction systems based on a different number of C=O double bonds present in the gas phase molecule are considered to replace CO2. The error in computed adsorption energy is directly proportional to the number of C=O double bonds present in the gas phase molecule. Additionally, both functionals predict similar carbon–oxygen activation barrier (40?kJ/mol) and equivalent C1s shifts for probe species (?2.6?eV for CCH3 and +1.5?eV CO3?), with respect to adsorbed CO2. Thus, by including a correction factor of 28?kJ/mol for the computed CO2 gas phase energy, we suggest using rPBE-vdW functional to investigate CO2 conversion reactions on different metals. 相似文献