全文获取类型
收费全文 | 661篇 |
免费 | 44篇 |
出版年
2023年 | 4篇 |
2022年 | 5篇 |
2021年 | 13篇 |
2020年 | 5篇 |
2019年 | 9篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 29篇 |
2014年 | 34篇 |
2013年 | 40篇 |
2012年 | 46篇 |
2011年 | 44篇 |
2010年 | 33篇 |
2009年 | 25篇 |
2008年 | 43篇 |
2007年 | 55篇 |
2006年 | 36篇 |
2005年 | 31篇 |
2004年 | 29篇 |
2003年 | 33篇 |
2002年 | 23篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1974年 | 2篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1964年 | 2篇 |
排序方式: 共有705条查询结果,搜索用时 31 毫秒
131.
Hila Shamoon Shlomo Cain Uri Shanas Avi Bar-Massada Yariv Malihi Idan Shapira 《European Journal of Wildlife Research》2018,64(3):35
Recreation activities in developed landscapes may add additional stressors that affect wildlife spatial and temporal activity patterns. We assessed medium to large mammal species response to a tourist scenic route in an agro-ecological mosaic landscape of the Shikma region, Israel. We placed 60 camera traps in an agro-ecological matrix and recorded mammals during three seasons between 2015 and 2017. We used N-mixture models to estimate mammal activity in relation with proximity to the scenic route and additional anthropogenic related factors such as traffic volume and land use. Anthropogenic development and activities had negative effects on large, endangered species, and none or positive on smaller, commensal species. Our results suggest an expansion of human recreation activity may have adverse outcomes on apex predators, which can cause a chain reaction and lead to meso-predator release, ultimately affecting prey species. The results emphasize the need for land managers to be extra cautious when attempting to add additional stressors (i.e., recreation activity) to developed landscapes such as the study area. Such landscapes can function as healthy ecosystems and provide suitable habitats for wildlife given that land managers are aware and account for wildlife-limiting factors in future development plans. 相似文献
132.
Shai Meiri Aaron M. Bauer Allen Allison Fernando Castro‐Herrera Laurent Chirio Guarino Colli Indraneil Das Tiffany M. Doan Frank Glaw Lee L. Grismer Marinus Hoogmoed Fred Kraus Matthew LeBreton Danny Meirte Zoltán T. Nagy Cristiano de C. Nogueira Paul Oliver Olivier S. G. Pauwels Daniel Pincheira‐Donoso Glenn Shea Roberto Sindaco Oliver J. S. Tallowin Omar Torres‐Carvajal Jean‐Francois Trape Peter Uetz Philipp Wagner Yuezhao Wang Thomas Ziegler Uri Roll 《Diversity & distributions》2018,24(2):262-273
Aim
Small geographic ranges make species especially prone to extinction from anthropogenic disturbances or natural stochastic events. We assemble and analyse a comprehensive dataset of all the world's lizard species and identify the species with the smallest ranges—those known only from their type localities. We compare them to wide‐ranging species to infer whether specific geographic regions or biological traits predispose species to have small ranges.Location
Global.Methods
We extensively surveyed museum collections, the primary literature and our own field records to identify all the species of lizards with a maximum linear geographic extent of <10 km. We compared their biogeography, key biological traits and threat status to those of all other lizards.Results
One in seven lizards (927 of the 6,568 currently recognized species) are known only from their type localities. These include 213 species known only from a single specimen. Compared to more wide‐ranging taxa, they mostly inhabit relatively inaccessible regions at lower, mostly tropical, latitudes. Surprisingly, we found that burrowing lifestyle is a relatively unimportant driver of small range size. Geckos are especially prone to having tiny ranges, and skinks dominate lists of such species not seen for over 50 years, as well as of species known only from their holotype. Two‐thirds of these species have no IUCN assessments, and at least 20 are extinct.Main conclusions
Fourteen per cent of lizard diversity is restricted to a single location, often in inaccessible regions. These species are elusive, usually poorly known and little studied. Many face severe extinction risk, but current knowledge is inadequate to properly assess this for all of them. We recommend that such species become the focus of taxonomic, ecological and survey efforts.133.
Jürgen Vahter Kaido Viht Asko Uri Ganesh babu Manoharan Erki Enkvist 《Bioorganic & medicinal chemistry》2018,26(18):5062-5068
A previously disclosed protein kinase (PK) CK2-selective inhibitor 4-(2-amino-1,3-thiazol-5-yl)benzoic acid (ATB) and its selenium-containing counterpart (ASB) revealed remarkable room temperature phosphorescence when bound to the ATP pocket of the protein kinase CK2. Conjugation of these fragments with a mimic of CK2 substrate peptide resulted in bisubstrate inhibitors with increased affinity towards the kinase. Attachment of the fluorescent acceptor dye 5-TAMRA to the conjugates led to significant enhancement of intensity of long-lifetime (microsecond-scale) photoluminescence of both sulfur- and selenium-containing compounds. The developed photoluminescent probes make possible selective determination of the concentration of CK2 in cell lysates and characterization of CK2 inhibitors by means of time-gated measurement of photoluminescence. 相似文献
134.
Pollinator‐mediated selection on floral size and tube color in Linum pubescens: Can differential behavior and preference in different times of the day maintain dimorphism?
下载免费PDF全文
![点击此处可从《Ecology and evolution》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Diversity of flower traits is often proposed as the outcome of selection exerted by pollinators. Positive directional pollinator‐mediated selection on floral size has been widely shown to reduce phenotypic variance. However, the underlying mechanism of maintaining within‐population floral color polymorphism is poorly understood. Divergent selection, mediated by different pollinators or by both mutualists and antagonists, may create and maintain such polymorphism, but it has rarely been shown to result from differential behavior of one pollinator. We tested whether different behaviors of the same pollinators in morning and evening are associated with dimorphic floral trait in Linum pubescens, a Mediterranean annual plant that exhibits variable within‐population frequencies of dark‐ and light‐colored flower tubes. Usia bicolor bee‐flies, the major pollinators of L. pubescens, are mostly feeding in the flower in the morning, while in the evening they are mostly visiting the flowers for mating. In 2 years of studying L. pubescens in a single large population in the Carmel, Israel, we found in one year that dark‐centered flowers received significantly higher fraction of visits in the morning. Fitness was positively affected by number of visits, but no fitness differences were found between tube‐color morphs, suggesting that both morphs have similar pollination success. Using mediation analysis, we found that flower size was under positive directional pollinator‐mediated selection in both years, but pollinator behavior did not explain entirely this selection, which was possibly mediated also by other agents, such as florivores or a‐biotic stresses. While most pollinator‐mediated selection studies show that flower size signals food reward, in L. pubescens, it may also signal for mating place, which may drive positive selection. While flower size found to be under pollinator‐mediated selection in L. pubescens, differential behavior of the pollinators in morning and evening did not seem to explain flower color polymorphism. 相似文献
135.
Developing methods for in vitro synthesis of the carbohydratestructure Gal 相似文献
136.
Grapevine petioles are more sensitive to drought induced embolism than stems: evidence from in vivo MRI and microcomputed tomography observations of hydraulic vulnerability segmentation 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Plant, cell & environment》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Uri Hochberg Caetano Albuquerque Shimon Rachmilevitch Herve Cochard Rakefet David‐Schwartz Craig R. Brodersen Andrew McElrone Carel W. Windt 《Plant, cell & environment》2016,39(9):1886-1894
The ‘hydraulic vulnerability segmentation’ hypothesis predicts that expendable distal organs are more susceptible to water stress‐induced embolism than the main stem of the plant. In the current work, we present the first in vivo visualization of this phenomenon. In two separate experiments, using magnetic resonance imaging or synchrotron‐based microcomputed tomography, grapevines (Vitis vinifera) were dehydrated while simultaneously scanning the main stems and petioles for the occurrence of emboli at different xylem pressures (Ψx). Magnetic resonance imaging revealed that 50% of the conductive xylem area of the petioles was embolized at a Ψx of ?1.54 MPa, whereas the stems did not reach similar losses until ?1.9 MPa. Microcomputed tomography confirmed these findings, showing that approximately half the vessels in the petioles were embolized at a Ψx of ?1.6 MPa, whereas only few were embolized in the stems. Petioles were shown to be more resistant to water stress‐induced embolism than previously measured with invasive hydraulic methods. The results provide the first direct evidence for the hydraulic vulnerability segmentation hypothesis and highlight its importance in grapevine responses to severe water stress. Additionally, these data suggest that air entry through the petiole into the stem is unlikely in grapevines during drought. 相似文献
137.
Moshe Shani Dina Zevin-Sonkin Ora Saxel Yoram Carmon Don Katcoff Uri Nudel David Yaffe 《Developmental biology》1981,86(2):483-492
Cloned cDNA probes were used to measure the accumulation of myosin heavy chain, myosin light chain 2, and actin mRNA during differentiation of rat skeletal muscle cell cultures. This was compared with the changes in the rate of synthesis of the corresponding proteins. Accumulation of those mRNA sequences was detectable a few hours before the onset of the phase of cell fusion; however, the main increase in hybridizable RNA occurred during the phase of rapid cell fusion. A close correlation was found between the amounts of mRNAs coding for these proteins and the rate of synthesis of the proteins. The results suggest that the activation of stored mRNA is not a major mechanism for controlling the time at which these proteins are synthesized. 相似文献
138.
Length of time in polymorphism is investigated as a possible evolutionary criterion for Mendel's laws in the case of two alleles at one locus and finite population. Deterministic models with constant and random segregation schemes are investigated. In deterministic models the optimum segregation system depends on the zygotic selection and is Mendelian only in symmetric models. In finite population models the initial gene frequencies interact with the segregation to determine mean time to fixation. In deterministic models with random distortion reduction of the variance of the distortion is more likely to produce polymorphism. 相似文献
139.
David S. Millar Barbara Zoll Uri Martinowitz Vijay V. Kakkar David N. Cooper 《Human genetics》1991,87(5):607-612
Summary A combination of Southern blotting and the analysis of polymerase chain reaction (PCR) amplified DNA fragments was used to screen the factor VIII genes of 527 haemophilia A patients for point mutations within TaqI restriction sites. Since this directed search strategy yielded only four gene lesions, it was concluded that its efficacy is less than that originally predicted. One novel point mutation was however found in a moderately severe haemophiliac; a CGA (Arg) to CTA (Leu) transversion at codon 2209, an evolutionarily conserved residue in the C2 domain of the factor VIII protein. The remaining three detected lesions, CGA (Arg)TGA (Term) transitions at codons 2116, 2147 and 2307, respectively, have been reported before and are consistent with recurrent mutation at these hypermutable sites. A number of TaqI restriction site polymorphisms/rare variants were also noted. These variants appear to be population-specific but are nevertheless potentially useful in individual cases as intragenic markers for carrier detection and antenatal diagnosis. 相似文献
140.
Uri Shalom Shalom W. Applebaum M. Paul Pener 《Archives of insect biochemistry and physiology》1988,9(4):313-322
Injection of azadirachtin into females of Locusta migratoria at the beginning of the last nymphal instar prevented molting to the adult stage, and many of these locusts survived for long periods as overage fifth-instar nymphs. Overage female nymphs synthesized vitellogenin; maximum vitellogenin content in their hemolymph was 6–7 times higher than that found in normal adult females. The overage female nymphs developed vitellogenic oocytes, but development was retarded to some extent: although vitellogenin did accumulate in the proximal oocytes, their maximum average length was only about 2.8 mm (compared to 6.2 mm in normal adult females) and extensive oocyte resorption was observed. Thus, attainment of adult competence of the organs and processes involved in female reproduction is independent to a considerable extent from the process of overt adult morphogenesis. 相似文献