全文获取类型
收费全文 | 4875篇 |
免费 | 383篇 |
国内免费 | 137篇 |
专业分类
5395篇 |
出版年
2024年 | 9篇 |
2023年 | 52篇 |
2022年 | 81篇 |
2021年 | 137篇 |
2020年 | 93篇 |
2019年 | 116篇 |
2018年 | 193篇 |
2017年 | 139篇 |
2016年 | 194篇 |
2015年 | 286篇 |
2014年 | 295篇 |
2013年 | 382篇 |
2012年 | 429篇 |
2011年 | 383篇 |
2010年 | 222篇 |
2009年 | 180篇 |
2008年 | 227篇 |
2007年 | 232篇 |
2006年 | 219篇 |
2005年 | 164篇 |
2004年 | 146篇 |
2003年 | 154篇 |
2002年 | 118篇 |
2001年 | 113篇 |
2000年 | 98篇 |
1999年 | 77篇 |
1998年 | 43篇 |
1997年 | 48篇 |
1996年 | 23篇 |
1995年 | 31篇 |
1994年 | 35篇 |
1993年 | 23篇 |
1992年 | 54篇 |
1991年 | 39篇 |
1990年 | 52篇 |
1989年 | 46篇 |
1988年 | 23篇 |
1987年 | 22篇 |
1986年 | 25篇 |
1985年 | 24篇 |
1984年 | 18篇 |
1983年 | 17篇 |
1982年 | 9篇 |
1976年 | 8篇 |
1975年 | 11篇 |
1974年 | 11篇 |
1973年 | 11篇 |
1971年 | 8篇 |
1970年 | 9篇 |
1968年 | 8篇 |
排序方式: 共有5395条查询结果,搜索用时 15 毫秒
91.
Association between the change in body mass index from early adulthood to midlife and subsequent type 2 diabetes mellitus
下载免费PDF全文
![点击此处可从《Obesity (Silver Spring, Md.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yiming Mu Chao Liu Jiajun Zhao Lulu Chen Qiang Li Tao Yang Li Yan Qin Wan Shengli Wu Yan Liu Guixia Wang Zuojie Luo Xulei Tang Gang Chen Yanan Huo Zhengnan Gao Qing Su Youmin Wang Guijun Qin Huacong Deng Xuefeng Yu Feixia Shen Li Chen Liebin Zhao Jichao Sun Lin Ding Yu Xu Min Xu Meng Dai Tiange Wang Di Zhang Jieli Lu Yufang Bi Shenghan Lai Donghui Li Weiqing Wang Guang Ning 《Obesity (Silver Spring, Md.)》2016,24(3):703-709
92.
The paper reports 13 species from Yaoluoping National Nature Reserve,Anhui,China,including a new species and a new subspecies,Tipula (Emodotipula) alexanderi Men,sp.nov.and Nephrotoma impigra anqingensis Men,subsp.nov.The female of Libnotes (Libnotes) pseudonohirai Men,2015 is described and illustrated for the first time.The males of Holorusia henana Yang,1999 and Tipula (Vestiplex)jiangi Yang & Yang,1991 are redescribed and illustrated with new morphological characters.A key to all species is provided. 相似文献
93.
The yellow‐spined bamboo locust, Ceracris kiangsu Tsai (Orthoptera: Oedipodidae), is a notorious defoliator of bamboos in China. In commercial bamboo forests, spraying insecticides to control C. kiangsu is neither convenient nor economic, therefore environmentally acceptable and cost‐effective methods are needed. Ceracris kiangsu adults are known to aggregate and gnaw at human urine‐contaminated materials; NaCl is a strong phagostimulant and NH4HCO3 is an attractant/arrestant. In the present paper, we found that foam plastic containers containing a blend of 0.03% bisultap, 3% NaCl, 3% NH4HCO3, and 0.1% Triton X‐100 (tetrad bait) had a powerful attracticidal effect and could kill a great number of especially female C. kiangsu adults, comparable to those containing a mixture of 0.03% bisultap and 5‐day‐incubated urine. In a field trial, the tetrad bait killed approximately 80% of females and about 9% of males in the treated plots after daily application for five consecutive days. The corrected average reduction rate was 48.2%. Moreover, the sex ratio was decreased from 1.18 before the trial to 0.25 after the experiment in the treated plots. These results indicated that there is the potential to develop a trap using NaCl as a phagostimulant and NH4HCO3 as an attractant that can be used for C. kiangsu control. 相似文献
94.
Daoyong Zhang Xiangliang Pan Guijin Mu Jianlong Wang 《Journal of applied phycology》2010,22(4):479-488
It has been demonstrated that antimony (Sb) at concentrations ranging from 1.0 to 10.0 mg L−1 inhibits O2 evolution. Deeper insight into the influence of Sb on PSII was obtained with measurements of in vivo chlorophyll fluorescence.
The donor and the acceptor sides of PSII were shown to be the target of Sb. Sb treatment induces inhibition of electron transport
from QA− to QB/QB− and accumulation of P680+. S2(QAQB)− charge recombination and oxidation by PQ9 molecules became more important in QA− reoxidation as the electron transfer in PSII was inhibited. Sb exposure caused a steady increase in the proportion of PSIIX and PSIIβ. These changes resulted in increased fluxes of dissipated energy and decreased index of photosynthesis performance, of maximum
quantum yield, and of the overall photosynthetic driving force of PSII. 相似文献
95.
以菠萝22个栽培品种的叶片为实验材料,测定其5种色泽参数(L*、a*、b*、c*和h*值)、5种色素(叶绿素、类胡萝卜素、花青苷、类黄酮和总酚)含量及3种抗氧化活性指标(ABTS、DPPH自由基和亚硝酸盐的清除能力),并进行相关性分析。研究结果显示,色泽参数a*和h*值可以作为菠萝叶片指示色泽、主要色素含量和抗氧化活性变化的重要指标;菠萝叶片主要色素组成是叶绿素、类黄酮和总酚,且含有少量的花青苷,几乎不含类胡萝卜素。相关性分析结果显示,菠萝叶片类黄酮和总酚含量均与3种抗氧化活性指标极显著正相关,而叶绿素含量与其它指标相关性未达到显著水平,类黄酮和总酚是菠萝叶片抗氧化活性的主要功效成分。 相似文献
96.
古丸菌纲(Archaeoglobi)是广古菌门下的纲级分类单元,包含古丸菌(Archaeoglobus)、地丸菌(Geoglobus)和铁丸菌(Ferroglobus)三个属,所属菌株均是严格嗜热厌氧菌,主要分布于海洋、陆地热液系统和油田环境中。Archaeoglobus属下的微生物是一类以硫酸盐、亚硫酸盐或硫代硫酸盐为电子受体代谢生成硫化氢(H2S)的化能自养或氢营养型微生物;而Geoglobus和Ferroglobus的成员则主要还原硝酸盐和铁离子。Archaeoglobi地理分布广泛,在元素生物地球化学循环过程中发挥着重要作用,是目前微生物生态学研究的一个热点。在进化方面,Archaeoglobi菌和产甲烷古菌具有较高的亲缘关系;同时,Archaeoglobi基因组中保留着部分产甲烷途径上的功能基因,最新研究表明部分未培养的Archaeoglobi基因组中含有完整的产甲烷通路。这些证据都表明Archaeoglobi菌的基因组特征可能是产甲烷古菌向硫酸盐还原菌进化的活化石。本文梳理了目前发现的11株Archaeoglobi菌株的生理生化特征和基因组分析结果,从化能自养、化能异养、硫化物呼吸、产乙酸、产甲烷等方面综述了已分离的Archaeoglobi菌的代谢特征,并基于宏基因组信息分析了未培养的Archaeoglobi菌基因组中的潜在代谢功能,为进一步分离培养此类未培养厌氧微生物提供理论指导。 相似文献
97.
核桃属部分种的小孢子发生及核型研究 总被引:9,自引:0,他引:9
穆英林;郗荣庭;吕增仁 《武汉植物学研究》1990,8(4):301-310
本试验采用常规压片法,观察了核桃属(Juglans L.)四个种花粉母细胞(PMC)的减数分裂过程和花粉形态,检测了两个种的花粉生活力,分析研究了七个种的核型。结果表明,普通核桃(J.regia)核桃楸(J.mandskurica Maxim.)和黑核桃(J.nigra L.)的PMC减数分裂基本正常,但河北核桃PMC的减数分裂过程都极不正常,供试的七个种,除普通核桃为2C核型外,其余均为2B核型,仅黑核桃一种带有随体染色体。根据核型特点把七个种分成三组,并探讨了组间与组内种间的亲缘演化关系。作者认为,河北核桃应为一种独立的种,核桃科在系统发育上可能来源于染色体基数为8的两群)不同植物。 相似文献
98.
Brachiaria, predominantly an African genus, contains species, such as B. brizantha, an apomictic C4 grass, that are commercially important forage grasses in tropical America, where they now cover about 55 million hectares. From B. brizantha accession CIAT 6780, we isolated an endophytic fungus that may be economically significant. The fungus was identified as Acremonium implicatum (J. Gilman & E.V. Abott). 18S rDNA and ITS rDNA sequences were used to characterize isolates of the endophyte, and showed that they belonged to the Acremonium genus, being close to A. strictum and A. kiliense. Using the random amplified polymorphic DNA (RAPD) technique, involving arbitrary primers of 10 bases, we showed that the isolates were highly similar to each other. Antiserum produced from a monoconidial culture of A. implicatum isolated from B. brizantha 6780, differentiated the isolates consistently in line with the DNA data. When we compared endophyte-free with endophyte-infected B. brizantha CIAT 6780 plants, both artificially inoculated with the pathogenic Drechslera fungus, we found that the endophyte-infected plants had fewer and smaller lesions than did the endophyte-free plants. Sporulation of Drechslera sp. on artificially inoculated leaf sheath tissues was also much less on tissue infected with the endophyte. 相似文献
99.
营养物质对桑黄菌丝生物量及胞外多糖产量的影响 总被引:2,自引:0,他引:2
研究了不同碳源、氮源和无机盐对桑黄深层培养菌丝生物量和胞外多糖产量的影响,结果表明:在培养温度为26℃、摇床转速为160r/min、发酵时间为10d的条件下,以桑黄菌丝生物量为指标,最适碳源、氮源和无机盐分别是果糖或葡萄糖、酵母粉或酵母膏、KH2P04或MgSO4·7H2O;菌丝生物量分别达到1.51、1.31、1.69、1.52、1.52、1.36g/100mL;以胞外多糖为指标,最适碳源、氮源和无机盐分别是葡萄糖、酵母膏、ZnSO4·7H2O,胞外多糖产量分别达到0.49、0.45、0.22g/100mL。 相似文献
100.
Yuping Li Xiwei Wu Hanlin Gao Jennifer M Jin Arthur X Li Young S Kim Sumanta K Pal Rebecca A Nelson Clayton M Lau Chao Guo Bing Mu Jinhui Wang Frances Wang Jessica Wang Yuanyin Zhao Wengang Chen John J Rossi Lawrence M Weiss Huiqing Wu 《Molecular medicine (Cambridge, Mass.)》2015,21(1):381-388
Piwi-interacting RNAs (piRNAs) are a distinct group of small noncoding RNAs (sncRNAs) that silence transposable genetic elements to protect genome integrity. Because of their limited expression in gonads and sequence diversity, piRNAs remain the most mysterious class of small RNAs. Studies have shown piRNAs are present in somatic cells and dysregulated in gastric, breast and liver cancers. By deep sequencing 24 frozen benign kidney and clear cell renal cell carcinoma (ccRCC) specimens and using the publically available piRNA database, we found 26,991 piRNAs present in human kidney tissue. Among 920 piRNAs that had at least two copies in one specimen, 19 were differentially expressed in benign kidney and ccRCC tissues, and 46 were associated with metastasis. Among the metastasis-related piRNAs, we found three piRNAs (piR-32051, piR-39894 and piR-43607) to be derived from the same piRNA cluster at chromosome 17. We confirmed the three selected piRNAs not to be miRNAs or miRNA-like sncRNAs. We further validated the aberrant expression of the three piRNAs in a 68-case formalin-fixed and paraffin-embedded (FFPE) ccRCC tissue cohort and showed the up-regulation of the three piRNAs to be highly associated with ccRCC metastasis, late clinical stage and poor cancer-specific survival. 相似文献