全文获取类型
收费全文 | 19433篇 |
免费 | 1433篇 |
国内免费 | 1358篇 |
专业分类
22224篇 |
出版年
2024年 | 52篇 |
2023年 | 291篇 |
2022年 | 631篇 |
2021年 | 1066篇 |
2020年 | 710篇 |
2019年 | 893篇 |
2018年 | 803篇 |
2017年 | 616篇 |
2016年 | 883篇 |
2015年 | 1255篇 |
2014年 | 1474篇 |
2013年 | 1509篇 |
2012年 | 1761篇 |
2011年 | 1535篇 |
2010年 | 953篇 |
2009年 | 815篇 |
2008年 | 945篇 |
2007年 | 766篇 |
2006年 | 728篇 |
2005年 | 575篇 |
2004年 | 526篇 |
2003年 | 471篇 |
2002年 | 407篇 |
2001年 | 372篇 |
2000年 | 341篇 |
1999年 | 313篇 |
1998年 | 206篇 |
1997年 | 188篇 |
1996年 | 174篇 |
1995年 | 152篇 |
1994年 | 115篇 |
1993年 | 105篇 |
1992年 | 132篇 |
1991年 | 110篇 |
1990年 | 96篇 |
1989年 | 58篇 |
1988年 | 46篇 |
1987年 | 49篇 |
1986年 | 25篇 |
1985年 | 26篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 4篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1966年 | 1篇 |
1950年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Rhodotorula glutinis, an oil producing strain, can utilize monosodium glutamate (MSG) wastewater as a raw material for lipid production. The effects of ammonium-N in the MSG wastewater (ammonium 15,000–25,000?mg/L, COD 30,000–50,000?mg/L) on cell growth, lipid accumulation and malic enzyme activity of R. glutinis have been studied. Four initial ammonium sulfate concentrations in the medium were set, which were 20, 60, 100, and 140?g/L. With an increase in the ammonium sulfate concentration, the uptake of ammonia nitrogen and lipid accumulation increased while the biomass decreased at 72?h. The maximum value of ammonia nitrogen consumption reached 5.77?g/L for an initial ammonium sulfate concentration of 140?g/L at 72?h. In addition, 60?g/L ammonium sulfate concentration may be an appropriate concentration for R. glutinis cultivation. The activity of the malic enzyme was measured and the results showed that there was a linear relationship between the intracellular lipid content and the total malic enzyme activity. 相似文献
92.
Caragana korshinskii seedlings maintain positive photosynthesis during short-term,severe drought stress 总被引:1,自引:0,他引:1
Seedling performance may determine plant distribution, especially in water-limited environments. Plants of Caragana korshinskii commonly grow in arid and semiarid areas in northwestern China, and endure water shortage in various ways, but little is
known about their performance when water shortage occurs at early growth stages. The water relations, photosynthetic activity,
chlorophyll (Chl) content and proline accumulation were determined in 1-year-old seedlings growing in a 1:1 mixture of Loess
soil and Perlite and subjected to (1) a water deficit for 20 days and (2) kept adequately watered throughout. The water deficit induced low (−6.1 MPa) predawn leaf water potentials (LWP), but did
not induce any leaf abscission. Stomatal conductance (g
s), leaf transpiration rate (E), and net photosynthetic rate (P
N) decreased immediately following the imposition of the water deficit, while the maximal photochemical efficiency of photosystem
II (PSII) (Fv/Fm) and the effective quantum yield of PSII (ΦPSII) decreased 15 days later. An early and rapid decrease in g
s, reduced E, increased Chl (a+b) loss, increased the apparent rate of photochemical transport of electrons through PSII (ETR)/P
N, as well as a gradual increase in non-photochemical quenching of fluorescence (NPQ) and proline may have contributed to preventing
ΦPSII from photodamage. C. korshinskii seedlings used a stress-tolerance strategy, with leaf maintenance providing a clear selective advantage, considering the
occasional rainfall events during the growing season. 相似文献
93.
94.
95.
Xian-Hao Cheng Shun-Xing Guo Chun-Lan Wang 《植物学报(英文版)》2006,48(11):1312-1317
The effects of substrate composition and temperature on myceilal growth and sclerotium production in Grlfola umbellate (Pers.) Pilaet were Investigated In the present study. The Induction of sclerotla of G. umbellate was affected greatly by the type of medium, as well as the type of carbon source. Malt-extract agar was able to induce the production of sclerotia. The production of sclerotia was also observed when the carbon source in the GPC agar medium (glucose 20 g/L, peptone 6 g/L, corn steep liquor 10 g/L, and agar 15 g/L) was replaced with glycerol or mannitol. Altering the composition of the GPC medium with milk powder, thiamine hydrochlorlde, extract of Armlllarla mellea, active clay, dlatomite, kaolin, or arginlne did not induce the production of sclerotla. A temperature range of 18-25 ℃ was suitable for both mycellai growth and sclerotium formation. Glycerol significantly Induced slerotium formation on nutrient supplemented with sawdust substrates In bottle culture. 24S-Polyporusterone A and polyporusterone B were assayed In samples of natural and cultured sclerotla. Both natural and cultured sclerotla contained 24S- polyporusterone A and polyporusterone B. 相似文献
96.
Rui Cheng Xiaoman Zheng Yingmei Wang Xing Ma Xin Liu Wenjun Xu Mengyun Wang Yuanpeng Gao Xupeng Xing Chuan Zhou Hongzheng Sun Zekun Guo Fusheng Quan Jun Liu Song Hua Yongsheng Wang Yong Zhang Xu Liu 《中国科学:生命科学英文版》2022,65(11):2257-2268
Animal cloning can be achieved by somatic cell nuclear transfer(SCNT), but the resulting live birth rate is relatively low. We previously improved the efficiency of bovine SCNT by exogenous melatonin treatment or by overexpression of lysine-specific demethylase 4D(KDM4D) and 4E(KDM4E). In this study, we revealed abundant alternative splicing(AS) transitions during fertilization and embryonic genome activation, and demonstrated abnormal AS in bovine SCNT embryos compared with in vitro fertilized ... 相似文献
97.
Yakai Xin Yu Guo Yanle Li Yujin Ma Liping Li Hongwei Jiang 《Saudi Journal of Biological Sciences》2019,26(2):421-426
To describe the effects of sodium-glucose co-transporter 2 (SGLT2) inhibitors on serum uric acid (SUA) in patients with type 2 diabetes mellitus (T2DM). PubMed, EMBASE, and CENTRAL were searched for randomized controlled trials of SGLT2 inhibitors in patients with T2DM up to Aug 10, 2017, without language or date restrictions. Thirty-one studies totaling 13,650 patients were included. SGLT2 inhibitors significantly decreased SUA levels compared with placebo, canagliflozin WMD –37.02?μmol/L, 95% CI [–38.41, –35.63], dapagliflozin WMD –38.05?μmol/L, 95% CI [–44.47, –31.62], empagliflozin WMD –42.07?μmol/L, 95% CI [–46.27, –37.86]. The drug class effect of SUA reduction suggesting SGLT2 inhibitors might be beneficial for diabetic patients with hyperuricemia. 相似文献
98.
99.
100.
ITMSQ: A software tool for N‐ and C‐terminal fragment ion pairs based isobaric tandem mass spectrometry quantification 下载免费PDF全文
Li‐Qi Xie Lei Zhang Ai‐Ying Nie Guo‐Quan Yan Jun Yao Yang Zhang Peng‐Yuan Yang Hao‐Jie Lu 《Proteomics》2015,15(22):3755-3764
Tandem MS (MS2) quantification using the series of N‐ and C‐terminal fragment ion pairs generated from isobaric‐labelled peptides was recently considered an accurate strategy in quantitative proteomics. However, the presence of multiplexed terminal fragment ion in MS2 spectra may reduce the efficiency of peptide identification, resulting in lower identification scores or even incorrect assignments. To address this issue, we developed a quantitative software tool, denoted isobaric tandem MS quantification (ITMSQ), to improve N‐ and C‐terminal fragment ion pairs based isobaric MS2 quantification. A spectrum splitting module was designed to separate the MS2 spectra from different samples, increasing the accuracy of both identification and quantification. ITMSQ offers a convenient interface through which parameters can be changed along with the labelling method, and the result files and all of the intermediate files can be exported. We performed an analysis of in vivo terminal amino acid labelling labelled HeLa samples and found that the numbers of quantified proteins and peptides increased by 13.64 and 27.52% after spectrum splitting, respectively. In conclusion, ITMSQ provides an accurate and reliable quantitative solutionfor N‐ and C‐terminal fragment ion pairs based isobaric MS2 quantitative methods. 相似文献