全文获取类型
收费全文 | 3400篇 |
免费 | 262篇 |
专业分类
3662篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 25篇 |
2021年 | 59篇 |
2020年 | 24篇 |
2019年 | 29篇 |
2018年 | 43篇 |
2017年 | 35篇 |
2016年 | 88篇 |
2015年 | 110篇 |
2014年 | 147篇 |
2013年 | 222篇 |
2012年 | 261篇 |
2011年 | 247篇 |
2010年 | 184篇 |
2009年 | 166篇 |
2008年 | 228篇 |
2007年 | 239篇 |
2006年 | 220篇 |
2005年 | 186篇 |
2004年 | 219篇 |
2003年 | 206篇 |
2002年 | 195篇 |
2001年 | 33篇 |
2000年 | 35篇 |
1999年 | 38篇 |
1998年 | 87篇 |
1997年 | 46篇 |
1996年 | 44篇 |
1995年 | 35篇 |
1994年 | 34篇 |
1993年 | 32篇 |
1992年 | 21篇 |
1991年 | 21篇 |
1990年 | 11篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有3662条查询结果,搜索用时 15 毫秒
1.
Using benzo(a)pyrene (BaP) as a probe for aryl hydrocarbon hydroxylase (AHH) activity, differences in mixed-function oxidase (MFO) activity were observed using microspectrofluorimetry in single living cells during long term treatment with 3-methylcholanthrene (3-MC) or carbaryl. Although these two compounds differ in chemical structure, similar effects were observed in 3T3 cell populations. The results suggest that the two compounds activate the same enzymatic system and that individual cells of a supposed homogeneous cell population are not equally sensitive to xenobiotics, i.e. subpopulations were observed which have differences in AHH activity. 相似文献
2.
Krajana Tainchum Wanapa Ritthison Thipwara Chuaycharoensuk Michael J. Bangs Sylvie Manguin Theeraphap Chareonviriyaphap 《Journal of vector ecology》2014,39(2):424-436
We determined the species diversity, blood‐feeding behavior, and host preference of Anopheles mosquitoes in two malaria endemic areas of Tak (Mae Sot District) and Mae Hong Son (Sop Moei District) Provinces, located along the Thai border with Myanmar, during a consecutive two‐year period. Anopheline mosquitoes were collected using indoor and outdoor human‐landing captures and outdoor cow‐baited collections. Mosquitoes were initially identified using morphological characters, followed by the appropriate multiplex AS‐PCR assay for the identification of sibling species within Anopheles (Cellia) complexes and groups present. Real‐time PCR was performed for parasite‐specific detection in mosquitoes (Plasmodium spp. and Wuchereria bancrofti). A total of 7,129 Anopheles females were captured, 3,939 from Mae Sot and 3,190 from Sop Moei, with 58.6% and 37% of all anophelines identified as An. minimus, respectively. All three malaria vector complexes were detected in both areas. One species within the Minimus Complex (An. minimus) was present along with two related species in the Funestus Group, (An. aconitus, An. varuna), two species within the Dirus Complex (An. dirus, An. baimaii), and four species within the Maculatus Group (An. maculatus, An. sawadwongporni, An. pseudowillmori, and An. dravidicus). The trophic behavior of An. minimus, An. dirus, An. baimaii, An. maculatus, and An. sawadwongporni are described herein. The highest An. minimus densities were detected from February through April of both years. One specimen of An. minimus from Mae Sot was found positive for Plasmodium vivax. 相似文献
3.
4.
Sylvie Cablé Michèle Kedinger Michel Dauça 《Differentiation; research in biological diversity》1993,54(2):99-108
Abstract. The development of peroxisomes and expression of their enzymes were investigated in differentiating intestinal epithelial cells during their migration along the crypt-villus axis. Sequential cell populations harvested by a low-temperature method were identified by microscopy, determination of alkaline phosphatase and sucrase activities and incorporation of [3 H]-thymidine into DNA. Ultrastructural cytochemistry after staining for catalase activity, revealed the presence of peroxisomes in undifferentiated stem cells located in the crypt region. Morphometry indicated that the number of these organelles increased as intestinal epithelial cells differentiate. Catalase activity was higher in the crypt cells than in the mature enterocytes harvested from villus tips. On the other hand, an increasing gradient of activity was observed from crypts to villus tips for peroxisomal oxidases, i.e. fatty acyl coA oxidase, D-amino acid oxidase and polyamine oxidase. These findings indicate that biogenesis of peroxisomes occurs during migration of intestinal epithelial cells along the crypt-villus axis and that peroxisomal oxidases contribute substantially to the biochemical maturation of enterocytes. 相似文献
5.
Medicago truncatula,a model plant for studying the molecular genetics of theRhizobium-legume symbiosis 总被引:7,自引:0,他引:7
David G. Barker Sylvie Bianchi François Blondon Yvette Dattée Gérard Duc Sadi Essad Pascal Flament Philippe Gallusci Gérard Génier Pierre Guy Xavier Muel Jacques Tourneur Jean Dénarié Thierry Huguet 《Plant Molecular Biology Reporter》1990,8(1):40-49
Medicago truncatula has all the characteristics required for a concerted analysis of nitrogen-fixing symbiosis withRhizobium using the tools of molecular biology, cellular biology and genetics.M. truncatula is a diploid and autogamous plant has a relatively small genome, and preliminary molecular analysis suggests that allelic
heterozygosity is minimal compared with the cross-fertilising tetraploid alfalfa (Medicago sativa). TheM. truncatula cultivar Jemalong is nodulated by theRhizobium meliloti strain 2011, which has already served to define many of the bacterial genes involved in symbiosis with alfalfa. A genotype
of Jemalong has been identified which can be regenerated after transformation byAgrobacterium, thus allowing the analysis ofin-vitro-modified genes in an homologous transgenic system. Finally, by virtue of the diploid, self-fertilising and genetically homogeneous
character ofM. truncatula, it should be relatively straightforward to screen for recessive mutations in symbiotic genes, to carry out genetic analysis,
and to construct an RFLP map for this plant. 相似文献
6.
Summary As a means to estimate potential oxygen consumption, profiles of elctron transport system (ETS) activity were made along three transects across the Weddell-Scotia Confluence zone (WSC) and the marginal ice zone (which overlapped in part) during the EPOS leg 2 cruise of the RV Polarstern. The integrated ETS activity between 0 and 100 m depth (referred to in situ temperatures) ranged from 261 meq (mili-electron equivalents) m–2 day–1 in the WSC to 45 meq m–2 day–1 in the southernmost stations at 62° S. The temporal changes in the overall distribution of ETS activity were small compared with the spatial variations. The main feature of the ETS activity distribution was the presence of maxima located in the WSC, coinciding with peaks of phytoplankton biomass. Different relationships between ETS and chlorophyll a concentration in these maxima appeared to be related to diatom or flagellate dominance. Vertically integrated ETS activities were significantly correlated with chlorophyll a and paniculate organic carbon concentrations, primary production and bacterial thymidine uptake.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation 相似文献
7.
Sylvie Demignot Malcolm V. Pimm Suzanne R. Thorpe Robert W. Baldwin 《Cancer immunology, immunotherapy : CII》1991,33(6):359-366
Summary Radioiodine-labelled 791T/36 monoclonal antibody (mAb) and its Fab/c fragment, consisting of one Fab arm and the Fc portion, have identical whole-body survival curves in BALB/c mice (t1/2 = 3.75 days). Therefore, these two forms of this antibody provide a suitable model for studying the role of valency in the targeting efficiency of antibodies to tumours in vivo. 791/T36 antibody and its Fab/c fragment were labelled either by direct iodination using the iodogen method (125I) or by dilactitol-125I-tyramine (125I-DLT), a residualizing label, which accumulates in the cells involved in degradation of the carrier protein. In tumour-bearing nude mice, the percentage of injected dose of mAb or Fab/c fragment reaching the specific 791T tumour was similar, and these proteins appeared to be catabolized at a similar rate in this tissue. mAb, but not the Fab/c fragment, was found to be very actively catabolized by the liver and spleen of tumour-bearing mice compared to control nude mice, this probably resulting from clearance of immune complexes. This effect was most pronounced when the mAb was labelled with125I-DLT, the percentage of injected dose of mAb reaching the spleen and liver being higher than the percentage of injected dose reaching the tumour. This effect was not seen with the Fab/c fragment. Autoradiographic studies on tumour sections, which exhibit antigenic sites throughout the tumour mass, showed that the Fab/c fragment was already homogeneously distributed in the tumour 12 h after injection whereas the whole antibody was mainly localized at the periphery of the tumour. Those results suggest a binding site barrier effect. Overall, these results indicate that the highest valency and affinity may not be the optimal choice for mAb to be used for therapeutic purposes. 相似文献
8.
Circadian Rhythms in Competitive Sabre Fencers: Internal Desynchronization and Performance 总被引:1,自引:0,他引:1
Alain Reinberg Sylvie Proux Jean Pierre Bartal Francis L vi Alena Bicakova-rocher 《Chronobiology international》1985,2(3):195-201
During a 7-10 day span, circadian rhythms of sleep-wake, self-rated fatigue and mood, oral temperature, eye-hand skill and right and left hand grip strength were investigated in eight subjects: five males (21-28 years of age), members of the French sabre fencing team selected for the 1984 Olympic Games in Los Angeles, and three females (19-26 years of age) practicing fleuret (foil) fencing as a sports activity. On the average six measurements/day/variable/subject were performed. The single cosinor method showed that a circadian rhythm was detectable for only 26 out of the 56 time series (46.4%). Power spectrum analysis gave almost the same figure (19 out of 48: 39.5%) with regard to rhythms with τ=24hr indicating that with one exception (subject JFL) rhythms were internally desynchronized including differences τ between right and left hand grip strength rhythms for three subjects. Results suggest: (a) a physiologic synchronization of circadian rhythms may be a predictor of good performance; (b) however, internal desynchronization as shown previously may be a trivial phenomenon and thus does not imply in itself alterations of either health or performance; (c) chronobiologic methods should be recommended for a better understanding of changes in performance by those participating in competitive and other sports. 相似文献
9.
Summary The lactose transport carrier from parental (X71/F'W3747) and mutant cells (54/F'5441) was reconstituted into proteoliposomes. Transport by the counterflow assay showed slightly greater activity in proteoliposomes prepared from extracts of the mutant membranes compared with that for the parental cell. The mutant carrier showed a threefold lowerK
m
but similarV
max compared to the parent. On the other hand proteoliposomes from the mutant showed a defect in protonmotive force-driven accumulation, compared with the parent. With a pH gradient (inside alkaline) plus a membrane potential (inside negative) the parental proteoliposomes accumulated lactose 25-fold over the medium concentration while the mutant proteoliposomes accumulated sixfold. In a series of experiments proteoliposomes were exposed to proteolytic enzymes. Chrymotrypsin treatment resulted in 30% inhibition of counterflow activity for the reconstituted carrier from both parent and mutant. Papain produced 84% inhibition of transport by the reconstituted parental carrier but only 41% of that of the mutant. Trypsin and carboxypeptidase Y treatment had no effect on counterflow activity of either parent or mutant. Exposure of purified lactose carrier in proteoliposomes to carboxypeptidase Y resulted in the release of alanine and valine, the two C-terminal amino acids predicted from the DNA sequence. 相似文献
10.