全文获取类型
收费全文 | 87867篇 |
免费 | 7403篇 |
国内免费 | 4806篇 |
出版年
2023年 | 823篇 |
2022年 | 1937篇 |
2021年 | 3812篇 |
2020年 | 2437篇 |
2019年 | 2977篇 |
2018年 | 3032篇 |
2017年 | 2177篇 |
2016年 | 3130篇 |
2015年 | 5009篇 |
2014年 | 5735篇 |
2013年 | 6538篇 |
2012年 | 7646篇 |
2011年 | 7023篇 |
2010年 | 4246篇 |
2009年 | 3822篇 |
2008年 | 4699篇 |
2007年 | 4186篇 |
2006年 | 3704篇 |
2005年 | 3145篇 |
2004年 | 2746篇 |
2003年 | 2423篇 |
2002年 | 2129篇 |
2001年 | 1688篇 |
2000年 | 1672篇 |
1999年 | 1554篇 |
1998年 | 945篇 |
1997年 | 859篇 |
1996年 | 870篇 |
1995年 | 792篇 |
1994年 | 752篇 |
1993年 | 588篇 |
1992年 | 897篇 |
1991年 | 718篇 |
1990年 | 660篇 |
1989年 | 596篇 |
1988年 | 478篇 |
1987年 | 408篇 |
1986年 | 383篇 |
1985年 | 336篇 |
1984年 | 269篇 |
1983年 | 253篇 |
1982年 | 145篇 |
1981年 | 161篇 |
1980年 | 126篇 |
1979年 | 202篇 |
1978年 | 113篇 |
1977年 | 127篇 |
1976年 | 115篇 |
1975年 | 143篇 |
1974年 | 153篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
861.
A. Kleinhofs A. Kilian M. A. Saghai Maroof R. M. Biyashev P. Hayes F. Q. Chen N. Lapitan A. Fenwick T. K. Blake V. Kanazin E. Ananiev L. Dahleen D. Kudrna J. Bollinger S. J. Knapp B. Liu M. Sorrells M. Heun J. D. Franckowiak D. Hoffman R. Skadsen B. J. Steffenson 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1993,86(6):705-712
A map of the barley genome consisting of 295 loci was constructed. These loci include 152 cDNA restriction fragment length polymorphism (RFLP), 114 genomic DNA RFLP, 14 random amplified polymorphic DNA (RAPD), five isozyme, two morphological, one disease resistance and seven specific amplicon polymorphism (SAP) markers. The RFLP-identified loci include 63 that were detected using cloned known function genes as probes. The map covers 1,250 centiMorgans (cM) with a 4.2 cM average distance between markers. The genetic lengths of the chromosomes range from 124 to 223 cM and are in approximate agreement with their physical lengths. The centromeres were localized to within a few markers on all of the barley chromosomes except chromosome 5. Telomeric regions were mapped for the short (plus) arms of chromosomes 1, 2 and 3 and the long (minus) arm of chromosomes 7.This research was also supported by other members of the NABGMP: K. Kasha, Department of Crop Science, University of Guelph, Guelph, Ontario, Canada NIG 2W1; W. Kim, Agriculture Canada Research Station, 195 Dafoe Road, Winnipeg, Manitoba, Canada R3T 2M9; A. Laroche, Agriculture Canada Research Station, P.O. Box 3000 Main, Lethbridge, Alberta, Canada,TU 4B1; S. Molnar, Plant Research Centre Agriculture Canada, Central Experimental farm, Ottawa, Ontario, Canada K1A 0C6; G. Scoles, Department of Crop Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N OWOThis research is part of the North American Barley Genome Mapping Project, R. A. Nilan and K. Kasha, Coordinator and Associate Coordinator, respectively
Permanent address: Department of Plant Genetics, NI Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow 相似文献
862.
863.
Sharon X. Chen Charles C. Hardin Harold E. Swaisgood 《Journal of Protein Chemistry》1993,12(5):613-625
Incubation of -lactoglobulin with immobilized trypsin at 5–10°C results in a time-dependent release of several fragments of the core domain in yields approaching 15%. Digests were fractionated by ion-exchange chromatography with a Mono Q HR5/5 column and analyzed after disulfide reduction by polyacrylamide gel electrophoresis in sodium dodecylsulfate. Three fragments with approximate molecular weights of 13.8, 9.6, and 6.7 kD were identified. The fraction from ion-exchange chromatography yielding the 6.7 kD fraction after disulfide reduction was further characterized because it was most homogeneous and gave the highest yield. The C-terminal cleavage site of the 6.7 kD core fragment appeared to be Lys100 or Lys101 as determined by C-terminal amino acid analysis. The exact masses, after reduction with dithiothreitol, are 6195 and 6926 as determined by laser desorption mass spectrometry, corresponding to residues 48–101 and 41–100. Prior to reduction, -lactoglobulin C-terminal residues 149–162 are connected to these core domain fragments as shown by C-terminal analysis and mass spectrometry. Structural studies indicate that these 7.9 and 8.6 kD core domain fragments released by immobilized trypsin retain much of their native structure. CD spectra indicate the presence of antiparallel -sheet structure similar to the native protein but the -helix is lost. Spectra in the aromatic region indicate the existence of tertiary structure. Moreover, structural transitions in urea are completely reversible as measured by CD spectra, although the extrapolated G
D
H20
and the urea concentration at the transition midpoint are lower than for the native protein. The core domain fragments also display apH-dependent binding to immobilizedtrans-retinal as does intact protein. A single endotherm is obtained for both core domain fragments and native protein upon differential scanning calorimetry, but again, the domain is less stable as indicated by a transition peak maxima of 56.9°C as compared with 81.1°C for native protein.Abbreviations used: CD, circular dichroism; CPG, controlled pore glass; DSC, differential scanning calorimetry; DTT, dithiothreitol; FPLC, fast flow liquid chromatography; HPLC, high-performance liquid chromatography; PITC, phenylisothiocyanate; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; TEA, triethylamine; UV, ultraviolet. 相似文献
864.
865.
866.
867.
本文报道在我国广西隆林壮族中发现一个罕見的HbQ复合α,β地中海贫血家系。先证者女,18岁,贫血面容,肝脾肿大。化学结构分析确证本Hb变异体为HbQ Thailand[α74(EF3)Asp→His]。血红蛋白组成以及α和β珠蛋白基因分析结果表明,先证者的珠蛋白基因型为-α~Q/-α~T复合β°/β°(IVSI-1G→T/Codon17A→T);先证者父的基因型为-‘α~Q/-复合β~O/β~A(IVSI-1G→T/β~A);先证母的基因型为-α~T/αα复合β~O/β~A(Codon17A→T/β~A)。 相似文献
868.
本文报导了薄层层析法及高压液相色谱法定性定量地测定植物油甘油酯的组成,对不同来源的脂肪酶对植物油的水解进行了研究。实验结果表明,不同来源的脂肪酶对植物油(橄榄油)的水解性不同,同一脂肪酶水解不同种类的植物油,脂肪酶的水解率也不同,脂肪酶水解植物油有最适pH和最适温度。 相似文献
869.
利用碘乙酰胺氮氧自由基标记钙调蛋白研究了它与三氟拉嗪(TFP)、酸枣仁皂甙A(JuA)的相互作用。结果表明,每分子CaM分别至少可以结合两分子的TFP及JuA,它们的作用影响了CaM上的Met残基(主要是71,72和76)的环境,使反应自由基运动自由度的旋转相关时间τR值下降。据τR变化的趋势,推测TFP和JuA都是通过疏水作用结合到CaM上的疏水沟区,但两者的结合位点可能不同。 相似文献
870.
本文采用系列凝集素柱层析法,并配合外切糖苷酶处理研究了在视黄酸(RA)作用1—5天过程中人肝癌细胞株SMMC-7721细胞表面N糖链结构的变化。结果表明,RA促进3~H-甘露糖(Man)参入细胞表面N糖链,使高甘露糖型N糖链的百分比下降,复杂型百分比上升,并促进二天线N糖链的生物合成,使多天线特别是四天线和C_2,C_(21)b三天线N糖链的合成减少。结果提示,N糖链结构的这些变化可能是RA诱导SMMC-7721细胞向正常方向分化的结果。 相似文献