全文获取类型
收费全文 | 4916篇 |
免费 | 551篇 |
国内免费 | 386篇 |
专业分类
5853篇 |
出版年
2023年 | 32篇 |
2022年 | 87篇 |
2021年 | 161篇 |
2020年 | 146篇 |
2019年 | 179篇 |
2018年 | 185篇 |
2017年 | 157篇 |
2016年 | 192篇 |
2015年 | 287篇 |
2014年 | 296篇 |
2013年 | 313篇 |
2012年 | 441篇 |
2011年 | 396篇 |
2010年 | 271篇 |
2009年 | 256篇 |
2008年 | 306篇 |
2007年 | 258篇 |
2006年 | 224篇 |
2005年 | 239篇 |
2004年 | 237篇 |
2003年 | 241篇 |
2002年 | 223篇 |
2001年 | 170篇 |
2000年 | 116篇 |
1999年 | 105篇 |
1998年 | 51篇 |
1997年 | 42篇 |
1996年 | 28篇 |
1995年 | 18篇 |
1994年 | 27篇 |
1993年 | 8篇 |
1992年 | 21篇 |
1991年 | 15篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 13篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1983年 | 5篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1967年 | 5篇 |
排序方式: 共有5853条查询结果,搜索用时 15 毫秒
991.
992.
993.
Yan HU Li‐Wei SUN Mokgolodi Neo C. Yan‐Xia ZHANG Chun‐Xiu WEN Xiao‐Liang XIE Yu‐Jun LIU 《植物分类学报:英文版》2010,48(2):133-145
Unresolved controversies concerning classification of the monotypic genus Perilla L. have hindered the complete understanding and subsequent sustainable use of these vital food, oil and medicinal plants to their full potential. We attempted to use scanning electron microscopy to obtain palynological evidence from Perilla plants of 21 samples from seven provinces in China as a potential extra attribute in classification. The findings showed that pollen grains from plants of 11 samples were oblate, while those of the other 10 were suboblate in shape, and there were no any type of prolate pollen grains being observed. Pollen grains of all the samples had diverse exine ornamentations. Based on whether having continuous tecta on the ornamentations, all of the pollen grains derived from the 21 samples were classified into two categories, fourteen of them with irregular reticulates, seven with continuous tecta with no perforations. None of the samples were bireticulates. The ornamentation pattern and size of pollen grains jointly provided evidence that it is appropriate to classify the genus Perilla into five varieties of one species. Furthermore, by comparison, it is concluded that shapes and exine ornamentations of Perilla are unique among those of the seven genera already investigated in the subfamily Lamioideae. Using these pollen features, Perilla could be easily distinguished from two other subtribes (Menthinae Briq. and Thyminae Briq.) in the same tribe, supporting the view that Perilla and other four related genera were divided into one subtribe (Perillinae). 相似文献
994.
995.
Feng J Chen Y Pu J Yang X Zhang C Zhu S Zhao Y Yuan Y Yuan H Liao F 《Analytical biochemistry》2011,(1):144-149
The classical malachite green (MLG) assay of phosphate, which added MLG after molybdate to the acidified reaction solutions of phosphate, tolerated interference from papaverine, sildenafil, and some similar hydrophobic amines. Resonance Rayleigh scattering signals, the alleviation of interference by poly(vinyl alcohol), and the precipitation of some yellow complexes supported that the irreversible aggregation of the complexes of a hydrophobic amine of interference and phosphomolybdate reduced the amounts of phosphomolybdate accessible to MLG and caused the interference. By adding MLG before molybdate to the acidified reaction solutions of phosphate, the complexes of phosphomolybdate and MLG were preferentially formed before the complexes of phosphomolybdate and such a hydrophobic amine effectively aggregated; thereby, an improved MLG assay of phosphate with the resistance to common hydrophobic amines was developed. Using the improved MLG assay of phosphate and a phosphatase to release phosphate from AMP, a spectrometric method successfully estimated the half-inhibition concentrations of papaverine on the recombinant human cyclic nucleotide phosphodiesterase (PDE) isozyme 4 and the mixture of PDE isozymes from rabbit brain. Therefore, the improved MLG assay of phosphate was a favorable and universal technique for developing spectrometric methods for characterizing and screening inhibitors of enzymes that release phosphate during their actions. 相似文献
996.
de Carvalho LP Ling Y Shen C Warren JD Rhee KY 《Archives of biochemistry and biophysics》2011,(1):90-99
Succinic semialdehyde dehydrogenases (SSADHs) are ubiquitous enzymes that catalyze the NAD(P)+-coupled oxidation of succinic semialdehyde (SSA) to succinate, the last step of the γ-aminobutyrate shunt. Mycobacterium tuberculosis encodes two paralogous SSADHs (gabD1 and gabD2). Here, we describe the first mechanistic characterization of GabD1, using steady-state kinetics, pH-rate profiles, 1H NMR, and kinetic isotope effects. Our results confirmed SSA and NADP+ as substrates and demonstrated that a divalent metal, such as Mg2+, linearizes the time course. pH-rate studies failed to identify any ionizable groups with pKa between 5.5 and 10 involved in substrate binding or rate-limiting chemistry. Primary deuterium, solvent and multiple kinetic isotope effects revealed that nucleophilic addition to SSA is very fast, followed by a modestly rate-limiting hydride transfer and fast thioester hydrolysis. Proton inventory studies revealed that a single proton is associated with the solvent-sensitive rate-limiting step. Together, these results suggest that product dissociation and/or conformational changes linked to it are rate-limiting. Using structural information for the human homolog enzyme and 1H NMR, we further established that nucleophilic attack takes place at the Si face of SSA, generating a thiohemiacetal with S stereochemistry. Deuteride transfer to the Pro-R position in NADP+ generates the thioester intermediate and [4A-2H, 4B-1H] NADPH. A chemical mechanism based on these data and the structural information available is proposed. 相似文献
997.
Park DH Thapa SP Choi BS Kim WS Hur JH Cho JM Lim JS Choi IY Lim CK 《Journal of bacteriology》2011,193(2):586-587
The Japanese Erwinia strain Ejp617 is a plant pathogen that causes bacterial shoot blight of pear in Japan. Here, we report the complete genome sequence of strain Ejp617 isolated from Nashi pears in Japan to provide further valuable insight among related Erwinia species. 相似文献
998.
Park JH Cho YJ Chun J Seok YJ Lee JK Kim KS Lee KH Park SJ Choi SH 《Journal of bacteriology》2011,193(8):2062-2063
Vibrio vulnificus is the causative agent of life-threatening septicemia and severe wound infections. Here, we announce the complete annotated genome sequence of V. vulnificus MO6-24/O, isolated from a patient with septicemia. When it is compared with previously known V. vulnificus genomes, the genome of this bacterium shows a unique genetic makeup, including phagelike elements, carbohydrate metabolism-related genes, and the superintegron. 相似文献
999.
Lee JH Chae JP Lee JY Lim JS Kim GB Ham JS Chun J Kang DK 《Journal of bacteriology》2011,193(18):5030-5031
Lactobacillus johnsonii PF01, an autochthonous bacterium of the gastrointestinal tract, was isolated from a fecal sample from a piglet. The strain adhered specifically to the duodenal and jejunal epithelial cells of the piglet and had high bile resistance activity. Here we report the genomic sequence of L. johnsonii PF01. 相似文献
1000.
Genome sequence of Lactobacillus ruminis SPM0211, isolated from a fecal sample from a healthy Korean
Lactobacillus ruminis SPM0211 is a potential probiotic strain that shows antimicrobial activity against emerging pathogens. Here we present the draft genomic sequence of L. ruminis SPM0211, isolated from a fecal sample from a healthy Korean and describe both the common and unique features of this strain. 相似文献