全文获取类型
收费全文 | 20877篇 |
免费 | 1591篇 |
国内免费 | 1013篇 |
出版年
2024年 | 33篇 |
2023年 | 285篇 |
2022年 | 509篇 |
2021年 | 887篇 |
2020年 | 623篇 |
2019年 | 753篇 |
2018年 | 767篇 |
2017年 | 659篇 |
2016年 | 921篇 |
2015年 | 1271篇 |
2014年 | 1479篇 |
2013年 | 1534篇 |
2012年 | 1879篇 |
2011年 | 1629篇 |
2010年 | 1084篇 |
2009年 | 985篇 |
2008年 | 1124篇 |
2007年 | 1043篇 |
2006年 | 892篇 |
2005年 | 780篇 |
2004年 | 712篇 |
2003年 | 660篇 |
2002年 | 566篇 |
2001年 | 251篇 |
2000年 | 193篇 |
1999年 | 182篇 |
1998年 | 170篇 |
1997年 | 116篇 |
1996年 | 117篇 |
1995年 | 110篇 |
1994年 | 83篇 |
1993年 | 81篇 |
1992年 | 72篇 |
1991年 | 72篇 |
1990年 | 54篇 |
1989年 | 54篇 |
1988年 | 60篇 |
1987年 | 39篇 |
1986年 | 33篇 |
1985年 | 33篇 |
1984年 | 42篇 |
1983年 | 42篇 |
1982年 | 37篇 |
1981年 | 50篇 |
1980年 | 38篇 |
1979年 | 35篇 |
1978年 | 35篇 |
1976年 | 30篇 |
1974年 | 35篇 |
1973年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
91.
Jose Pontón Fernando L. Hernando Maria Dolores Moragues Pedro L. Barea Mara Gerloni Stefania Conti Paola Fisicaro Cristina Cantelli Luciano Polonelli 《Mycopathologia》1996,133(2):89-94
The presence of heat shock mannoproteins (HSMPs) reactive with sIgA was demonstrated in several C. albicans strains. The subculture of the C. albicans isolated from mucosal surfaces on Sabouraud's dextrose agar at 25 °C switched off the HSMP expression. A re-expression of the HSMPs was obtained in the same medium by shifting the temperature of incubation to 37 °C. However, expression of HSMPs in two strains isolated from deep infections was maintained during several subcultures on Sabouraud's dextrose agar at 25 °C. A glycoprotein of 200 kDa seemed to be the main HSMP reacting with vaginal sIgA. The data presented in this study suggest that factors other than temperature can influence the expression of C. albicans HSMPs and therefore these antigens should be referred as stress mannoproteins.Abbreviations HSMPs
heat shock mannoproteins
- MAb
monoclonal antibody
- sIgA
secretory IgA 相似文献
92.
Thomas Altmann Gisela Felix Alison Jessop Annette Kauschmann Ursula Uwer Hugo Peña-Cortés Lothar Willmitzer 《Molecular genetics and genomics : MGG》1995,247(5):646-652
Using a two-component Ac/Ds system consisting of a stabilized Ac element (Acc1) and a non-autonomous element (DsA), 650 families of plants carrying independent germinal DsA excisions/transpositions were isolated. Progenies of 559 of these Acc1/DsA families, together with 43 families of plants selected for excision/transposition of wild-type (wt)Ac, were subjected to a broad screening program for mutants exhibiting visible alterations. This resulted in the identification of 48 mutants showing a wide variety of mutant phenotypes, including embryo lethality (24 mutants), chlorophyll defects (5 mutants), defective seedlings (2 mutants), reduced fertility (5 mutants), reduced size (3 mutants), altered leaf morphology (2 mutants), dark green, unexpanded rosette leaves (3 mutants), and aberrant flower or shoot morphology (4 mutants). To test whether these mutants were due to transposon insertions, a series of Southern blot experiments was performed on 28 families, comparing in each case several mutant plants with others showing the wild-type phenotype. A preliminary analysis revealed in 4 of the 28 families analyzed a common, novel DsA fragment in all mutant plants, which was present only in heterozygous plants with wt phenotype, as expected for DsA insertion mutations. These four mutants included two showing embryo lethality, one with dark green, unexpanded rosette leaves and stunted inflorescences, and one with curly growth of stems, leaves and siliques. Further evidence for DsA insertion mutations was obtained for one embryo lethal mutant and for the stunted mutant, while in case of the second embryo lethal mutant, the DsA insertion could be separated from the mutant locus by genetic recombination. 相似文献
93.
94.
Research Notes on Avian Biology 1994: Selected Contributions from the 21st International Ornithological CongressGeneral Biology: Migration
Subject: Migration 相似文献95.
A Pleiotropic Phospholipid Biosynthetic Regulatory Mutation in Saccharomyces Cerevisiae Is Allelic to Sin3 (Sdi1, Ume4, Rpd1) 总被引:7,自引:1,他引:6
下载免费PDF全文
![点击此处可从《Genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Three mutants were identified in a genetic screen using an INO1-lacZ fusion to detect altered INO1 regulation in Saccharomyces cerevisiae. These strains harbor mutations that render the cell unable to fully repress expression of INO1, the structural gene for inositol-1-phosphate synthase. The Cpe(-) (constitutive phospholipid gene expression) phenotype associated with these mutations segregated 2:2, indicating that it was the result of a single gene mutation. The mutations were shown to be recessive and allelic. A strain carrying the tightest of the three alleles was examined in detail and was found to express the set of co-regulated phospholipid structural genes (INO1, CHO1, CHO2 and OPI3) constitutively. The Cpe(-) mutants also exhibited a pleiotropic defect in sporulation. The mutations were mapped to the right arm of chromosome XV, close to the centromere, where it was discovered that they were allelic to the previously identified regulatory mutation sin3 (sdi1, ume4, rpd1, gam2). A sin3 null mutation failed to complement the mutation conferring the Cpe(-) phenotype. A mutant harboring a sin3 null allele exhibited the same altered INO1 expression pattern observed in strains carrying the Cpe(-) mutations isolated in this study. 相似文献
96.
Antonio Balas Felix Garcia-Sanchez Fernando Gomez-Reino Jose L. Vicario 《Immunogenetics》1994,39(6):452-452
Correspondence to: J. L. Vicario. 相似文献
97.
R. F. M. van Steveninck A. Babare D. R. Fernando M. E. van Steveninck 《Plant and Soil》1994,167(1):157-164
Plant species adapted to soils enriched with heavy metals often accumulate these metals in their above or below ground organs. In this study, electron probe microanalysis of fractured, quench-frozen root specimens of common crop species shows that an appreciable quantity of Zn can be bound as Zn phytate (myo-inositolkis-hexaphosphate) within small vacuoles of cells in the root elongation zone of lucerne, soybean, lupins, tomato, rapeseed, cabbage, radish, maize and wheat exposed to high levels of Zn (80–300 M). Globular deposits of Zn phytate are most frequently observed in the endodermis of dicotyledonous species and in the pericycle of monocotyledonous species, but may also occur in the stele and inner cortex after prolonged exposure to toxic levels of Zn. The deposits could not be found in Zn-treated sunflower, field peas and Italian ryegrass. In three crop species, lucerne, soybean and maize, Zn-induced phytate globules were frequent, but exposure of roots to 30 M Cd did not induce the formation of Cd-containing globular deposits as observed inLemna minor (Van Steveninck et al., 1990a, 1992). Simultaneous Zn and Cd treatment induced the formation of Zn phytate globules as effectively as Zn alone, and Cd was not detected in the deposits. 相似文献
98.
Iman Abdelmoty Fernando Albericio Louis A. Carpino Bruce M. Foxman Steven A. Kates 《Letters in Peptide Science》1994,1(2):57-67
Summary X-ray structure determinations of HBTU and HATU, well-known reagents for peptide bond formation, show that the solid-state structures of these compounds differ markedly from those commonly presented in the literature. The solid-state structures are isomers of the N,N,N',N'-tetramethyluronium salt formulation commonly written for HBTU and HATU. HBTU and HATU, obtained either directly from synthesis or from CH3CN solution, crystallize as the guanidinium N-oxide isomers. Both compounds crystallize in nearly identical conformations, despite marked differences in crystal packing. 相似文献
99.
水平回转对水稻幼苗叶细胞的影响 总被引:9,自引:0,他引:9
对在模拟微重力装置上回转14 天的水稻幼苗叶细胞进行了亚显微形态、电子探针和细胞酶化学研究。发现叶细胞质膜上Ca2+ -ATP酶活性消失,膜内钙总量上升、膜外钙总量下降,细胞骨架变得疏松,细胞壁变薄并凹凸不平。叶绿体的基粒和线粒体的内嵴亦有部分变化。其变化机制,首先是细胞质膜上Ca2+ -ATP酶活性消失,膜上钙泵停止工作,跨膜钙浓度差减小,膜内钙浓度上升,微管、微丝聚合受阻,细胞骨架疏松,分泌泡移动失去导向,从而导致细胞壁变薄等状态 相似文献
100.
Rui L. Mendes Helena L. Fernandes José A.P Coelho Joaquim M.S Cabral António M. F. Palavra Júlio M. Novais 《Journal of applied phycology》1994,6(3):289-293
Samples of the microalgaBotryococcus braunii were submitted to supercritical fluid extraction with carbon dioxide at 40 °C and pressures of 12.5, 20.0 and 30.0 MPa. The extraction yield and the fraction of the hydrocarbons in the extracts both increased with pressure and at 30 MPa these compounds were obtained rapidly. This behaviour is associated with the localization of the hydrocarbons outside the cell wall. In the extracts, which are fluid, golden and limpid, chlorophyll and phospholipids were not detected.Author for correspondence 相似文献