全文获取类型
收费全文 | 2562篇 |
免费 | 83篇 |
国内免费 | 1篇 |
出版年
2023年 | 23篇 |
2021年 | 22篇 |
2018年 | 69篇 |
2017年 | 69篇 |
2016年 | 72篇 |
2015年 | 89篇 |
2014年 | 98篇 |
2013年 | 125篇 |
2012年 | 129篇 |
2011年 | 117篇 |
2010年 | 110篇 |
2009年 | 71篇 |
2008年 | 39篇 |
2007年 | 39篇 |
2006年 | 37篇 |
2005年 | 143篇 |
2004年 | 108篇 |
2003年 | 83篇 |
2002年 | 24篇 |
2001年 | 31篇 |
1999年 | 21篇 |
1998年 | 21篇 |
1996年 | 27篇 |
1995年 | 30篇 |
1994年 | 22篇 |
1993年 | 25篇 |
1992年 | 22篇 |
1991年 | 34篇 |
1990年 | 26篇 |
1988年 | 28篇 |
1987年 | 24篇 |
1986年 | 25篇 |
1985年 | 28篇 |
1984年 | 37篇 |
1983年 | 41篇 |
1982年 | 28篇 |
1981年 | 31篇 |
1980年 | 32篇 |
1979年 | 59篇 |
1978年 | 31篇 |
1977年 | 24篇 |
1976年 | 24篇 |
1975年 | 35篇 |
1974年 | 33篇 |
1973年 | 31篇 |
1972年 | 31篇 |
1971年 | 21篇 |
1970年 | 24篇 |
1969年 | 35篇 |
1966年 | 23篇 |
排序方式: 共有2646条查询结果,搜索用时 15 毫秒
971.
972.
Carlos A. Aguilar-Trigueros Franz-Sebastian Krah William K. Cornwell Amy E. Zanne Nerea Abrego Ian C. Anderson Carrie J. Andrew Petr Baldrian Claus Bässler Andrew Bissett V. Bala Chaudhary Baodong Chen Yongliang Chen Manuel Delgado-Baquerizo Coline Deveautour Eleonora Egidi Habacuc Flores-Moreno Jacob Golan Jacob Heilmann-Clausen Stefan Hempel Yajun Hu Håvard Kauserud Stephanie N. Kivlin Petr Kohout Daniel R. Lammel Fernando T. Maestre Anne Pringle Jenna Purhonen Brajesh K. Singh Stavros D. Veresoglou Tomáš Větrovský Haiyang Zhang Matthias C. Rillig Jeff R. Powell 《Ecology letters》2023,26(9):1523-1534
Despite host-fungal symbiotic interactions being ubiquitous in all ecosystems, understanding how symbiosis has shaped the ecology and evolution of fungal spores that are involved in dispersal and colonization of their hosts has been ignored in life-history studies. We assembled a spore morphology database covering over 26,000 species of free-living to symbiotic fungi of plants, insects and humans and found more than eight orders of variation in spore size. Evolutionary transitions in symbiotic status correlated with shifts in spore size, but the strength of this effect varied widely among phyla. Symbiotic status explained more variation than climatic variables in the current distribution of spore sizes of plant-associated fungi at a global scale while the dispersal potential of their spores is more restricted compared to free-living fungi. Our work advances life-history theory by highlighting how the interaction between symbiosis and offspring morphology shapes the reproductive and dispersal strategies among living forms. 相似文献
973.
An introduction is presented to a taxonomic evaluation of rich cultivated and herbarium material of the genusTaraxacum from the Caucasus. Sources of the material, a survey of localities, and a preliminary account of the sections and species groups ofTaraxacum described from the Caucasus are given. The introduction is followed by a monograph ofT. sect.Porphyrantha, a section shown (contrary to the original conception and some literature data) to be endemic to the Caucasus. Six new species are described belonging to the section divided in two subsections, subsect.Porphyrantha and subsect.Haemantha, viz.T. pseudoporphyranthum, T. vepallidum, T. haemanthum, T. ignivomum, T. exstinctum andT. deminutum. Lectotypes are selected forT. porphyranthum Boiss. andT. pseudoroseum ?i?kin. 相似文献
974.
Kateřina Štůsková Jakub Pečenka Dorota Anna Tekielska Milan Špetík Zuzana Bytešníková Pavel Švec František Ondreáš Andrea Ridošková Lukáš Richtera Vojtěch Adam Aleš Eichmeier 《The Annals of applied biology》2023,182(2):226-237
Grapevine trunk pathogens (GTPs) cause serious damage to grapevines and have significant economic impacts. There is no effective protection against grapevine trunk diseases. Newly designed AgSe nanoparticles (NPs) and CuSe NPs, single-element Ag NPs, Cu NPs, Se NPs and selected chemicals or chemical agents such as sodium arsenite, 8-hydroxyquinoline, silver nitrate, colloidal silver, Altron Silver fertilizer and silver thiosulfate complex (NH4)3/Ag(S2O3)2 were tested in vitro against two serious GTPs Diaporthe eres, Eutypa lata and Diplodia seriata isolated from walnut. The most significant inhibition of fungal growth was observed for silver nitrate and AgSe NPs, which showed the highest level of half the maximum effective EC50 concentration with the lowest concentrations. In the case of silver nitrate at a concentration of 1000 mg L−1, 79% inhibition of mycelial growth was observed for the pathogen E. lata, 48% for D. seriata and 54% for D. eres. AgSe NPs, in which the concentration of silver is 2588 mg L−1 and that of selenium is 902 mg L−1, showed 68% inhibition of mycelial growth in the pathogen E. lata, 54% in D. seriata and 58% in D. eres. 相似文献
975.
Effect of flooding with sewage water on three wetland sedges 总被引:2,自引:0,他引:2
Hana Končalová Jan Květ Jan Pokorný Václav Hauser 《Wetlands Ecology and Management》1993,2(4):199-211
Plants of three wetland sedges, Carex vesicaria, C. rostrata, and C. gracilis, were subjected to flooding with diluted pig farm sewage water in a sand-culture experiment lasting for one growing season (20 weeks). Sewage water application altered growth dynamics and accumulation of dry matter in all three species; it shifted the distribution of dry matter in favor of above-ground parts; it depressed root growth both in dry mass and length; and it increased percentages of major nutrients (nitrogen, phosphorus, and potassium) in plant dry matter. In the root structure, sewage water application inhibited formation of gas spaces in the cortex, differentiation of exodermis and endodermis, and formation of starch grains in the cortex. The changes in root growth and structure are ascribed to the combination of (1) high nutrient availability, and (2) oxygen deficiency, which developed in the root medium following addition of sewage water. In view of these findings, Carex species are not well suited for use in the treatment of wastewaters rich in both mineral nutrients and organic matter. 相似文献
976.
Lüdemann I Pörtner R Schaefer C Schick K Srámkova K Reher K Neumaier M Franěk F Märkl H 《Cytotechnology》1995,19(2):111-124
A murine hybridoma cell line producing a monoclonal antibody against penicillin-G-amidase and a murine transfectoma cell line secreting a monovalent chimeric human/mouse Fab-antibody fragment were cultivated in three different media (serum-containing, low protein serum-free, and iron-rich protein-free) in flask cultures, stirred reactors and a fixed bed reactor. In static batch cultures in flasks both cell lines showed similar good growth in all three media.In suspension in a stirred reactor, the hybridoma cell line could be cultivated satisfactory only in serum-containing medium. In low protein serum-free medium, Pluronic F68 had to be added to protect the hybridoma cells against shear stress. But even with this supplement only batch, not chemostat mode was possible. In iron-rich protein-free medium the hybridoma cells grew also in continuous chemostat mode, but the stability of the culture was low. The transfectoma cell line did not grow in stirred reactors in any of the three media.Good results with both cell lines were obtained in fixed bed experiments, where the cells were immobilized in macroporous Siran®-carriers. The media, which were optimized in flask cultures, could be used without any further adaptation in the fixed bed reactor. Immobilization improved the stability and reliability of cultures of non-adherent animal cells in serum-free media tremendously compared to suspension cultures in stirred reactors. The volume-specific glucose uptake rate, an, indicator of the activity of the immobilized cells, was similar in all three media. Deviations in the metabolism of immobilized and suspended cells seem to be mainly due to low oxygen concentrations within the macroporous carriers, where the cells are supplied with oxygen only by diffusion.List of symbols c
substrate or product concentration mmol l–1
- c0
substrate or product concentration in the feed mmol l–1
- cGlc
glucose concentration mmol l–1
- cGln
glutamine concentration mmol l–1
- cAmm
ammonia concentration mmol l–1
- cLac
lactate concentration mmol l–1
- cFAB
concentration of Fab# 10 antibody fragment g l–1
- cMAb
monoclonal antibody concentration mg l–1
- D
dilution rate d–1
- q
cell-specific substrate uptake or metabolite production rate mmol cell–1 h–1
- qGlc
cell-specific glucose uptake rate mmol cell–1 h–1
- qGln
cell-specific glutamine uptake rate mmol cell–1 h–1
- qMAb
cell-specific MAb production rate mg cell–1 h–1
- q*
volume-specific substrate uptake or metabolite production rate mmol l–1 h–1
- q*FB
volume-specific substrate uptake or metabolite production rate related to the fixed bed volume mmol lFB
–1 h–1
- q*FB,Glc
volume-specific glucose uptake rate related to the fixed bed volume mmol lFB
–1 h–1
- q*FB,Gln
volume-specific glutamine uptake rate related to the fixed volume mmol lFB
–1 h–1
- q*FB,MAb
volume-specific MAb production rate related to the fixed volume mg lFB
–1 h–1
- q*FB,02
volume-specific oxygen uptake rate related to the fixed bed volume mmol lFB
–1 h–1
- t
time h
- U
superficial flow velocity mm s–1
- V
medium volume in the conditioning vessel of the fixed bed reactor l
- VFB
volume of the fixed bed l
- xv
viable cell concentration cells ml–1
- yAmm,Gln
yield of Ammonia from glutamine
- yLac,Glc
yield of lactate from glucose
-
specific growth rate h–1
- d
specific death rate h–1 相似文献
977.
978.
Pavla Čapková Miroslava Trchová Pavel Matějka Jiri Votinský Henk Schenk 《Journal of molecular modeling》1998,4(9):284-293
Molecular mechanics simulations using Cerius2 modelling environment combined with vibrational spectroscopy (IR and Raman) have been used to study the host-guest interactions in zirconium and vanadyl phosphate intercalated with ethanole. The strategy of investigation is based on the comparison of vibrational spectra for the host compound, intercalate and guest species. This comparison confirmed the rigidity of VOPO4- and Zr(HPO4)2-layers during the intercalation and provided us with the basis for the strategy of modelling. Molecular mechanics simulations revealed the structure of intercalates and enabled to analyse the host-guest interaction energy and bonding geometry. The bilayer arrangement of ethanole molecules in the interlayer space with two differently bonded ethanole molecules has been found in both intercalates. The average interaction energy ethanole-layer for two differently bonded ethanole molecules is : 127.5 and 135.7 kcal·mol-1 in Zr(HPO4)2·2C2H5OH, respectively 94.0 and 104.4 kcal·mol-1 in VOPO4·2C2H5OH. The Coulombic contribution to the ethanole-layer interaction energy is predominant in all cases, but the hydrogen bonding contribution is much higher in Zr(HPO4)2·2C2H5OH than in VOPO4·2C2H5OH. Present results of modelling enabled the interpretation of vibrational spectra and explanation of small changes in positions and shapes of spectral bands, in infrared and Raman spectra, proceeding from the host structure to intercalates. 相似文献
979.
Virus-like particles (VLPs) were isolated from the yeastWickerhamia fluorescens strain CCY61-1-1. The VLPs are approximately 42 nm in diameter and contain only one species of dsRNA molecule. The apparent
length of the dsRNA determined by native agarose gel electrophoresis was 4.6 kbp. Analysis of protein content of the VLPs
showed them to contain one major capsid protein with an apparent molar mass of 74.5 kDa. 相似文献
980.
Josef Kyncl Jaroslav Dobrý Václav Cílek Jiří Kolbek Karol Marhold Jan Kirschner Jan Zima Helena Štorchová František Kotlaba Zdeněk Pouzar L. Marvanová Zdeňka Slavíková Jiří Dostálek V. Zelený J. Minář Denisa Blažková Václav Zelený Denisa Blažková Jindrřich Chrtek jun 《Folia Geobotanica》1996,31(4):529-544