首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1289篇
  免费   91篇
  国内免费   2篇
  2024年   3篇
  2023年   51篇
  2022年   27篇
  2021年   43篇
  2020年   47篇
  2019年   42篇
  2018年   82篇
  2017年   81篇
  2016年   104篇
  2015年   67篇
  2014年   98篇
  2013年   151篇
  2012年   103篇
  2011年   127篇
  2010年   79篇
  2009年   89篇
  2008年   32篇
  2007年   17篇
  2006年   18篇
  2005年   7篇
  2004年   12篇
  2003年   4篇
  2002年   9篇
  2001年   11篇
  2000年   9篇
  1999年   7篇
  1998年   4篇
  1997年   6篇
  1996年   3篇
  1995年   3篇
  1993年   1篇
  1992年   6篇
  1991年   6篇
  1990年   5篇
  1989年   4篇
  1988年   2篇
  1987年   1篇
  1986年   4篇
  1985年   4篇
  1984年   5篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1977年   2篇
  1976年   2篇
  1974年   1篇
排序方式: 共有1382条查询结果,搜索用时 62 毫秒
41.
The conservation of beetles that depend on dying or dead wood (i.e. saproxylic), has received a great deal of attention in many parts of the world in recent years. Human activities such as urbanization and logging, and their results, e.g. global warming, destroy natural ecosystems and threaten unusual species such as Lucanus cervus (L. 1758), Rosalia alpina (L. 1758), Limoniscus violaceus (Müller 1821) and Osmoderma eremita (Scopoli 1763). Attempts have been made to conserve the habitats upon which these species depend. Although represented by a large number of species, saproxylic beetles in Turkey have not received much attention. Although some Turkish studies have acknowledged their value, comprehensive investigations of these species are very limited. The aim of this study is to make a list, from the literature, of the species that are endangered in Europe and found in Turkey, to highlight the importance of these species. The research includes 151 saproxylic beetle species belonging to the families Bostrichidae, Cerambycidae, Elateridae, Eucnemidae, Scarabaeidae, Euchiridae, Lucanidae and Mycetophagidae. The list of Turkish saproxylic beetles was prepared using the European Red List of Saproxylic Beetles. Information is provided about the IUCN Red List category in Europe, the locations of the species in Turkey, and their global geographic range. We gathered all data about these species from the international literature. Furthermore, we also include in the list certain species whose locations are not specified, but which inhabit Turkey. We obtained their records from some catalogs in Turkey. In addition to the list, we prepared three distribution maps for Turkey. The maps show distribution in Turkey of some species in the Endangered, Vulnerable and Near Threatened categories in the European Red List. It is expected that this study will lead to comprehensive studies on saproxylic beetles from Turkey.  相似文献   
42.
Length–weight relationships were calculated for nine freshwater fish species belonging to two families using 1020 specimens from 15 water sources in the western part of Anatolia, Turkey. This study is the first reference on length–parameters for these species, eight of which are endemic, and with new maximum length records for three of the species.  相似文献   
43.
We developed a high quality reconstruction of May–June precipitation for the interior region of southwestern Turkey using regional tree-ring data calibrated with meteorological data from Burdur. In this study, three new climate sensitive black pine chronologies were built. In addition to new chronologies, four previously published black pine chronologies were used for the reconstruction. Two separate reconstructions were developed. The first reconstruction used all site chronologies over the common interval AD 1813–2004. The second reconstruction used four of the chronologies with a common interval AD 1692–2004. R 2 values of the reconstructions were 0.64 and 0.51 with RE values of 0.63 and 0.51, respectively. During the period AD 1692–1938, 41 dry and 48 wet events were found. Very dry years occurred in AD 1725, 1814, 1851, 1887, 1916, and 1923, while very wet years occurred in AD 1736, 1780, 1788, 1803, and 1892. The longest dry period was 16 years long between 1860 and 1875. We then explored relationships between the reconstructed rainfall patterns and major volcanic eruptions, and discovered that wetter than normal years occurred during or immediately after the years with the largest volcanic eruptions.  相似文献   
44.
In the current study, a series of pyrazole-sulfonamide derivatives (2–14) were synthesized, characterized, and the inhibition effects of the derivatives on human carbonic anhydrases (hCA I and hCA II) were investigated as in vitro. Structures of these sulfonamides were confirmed by FT-IR, 1H NMR, 13C NMR and LC–MS analysis. 1H NMR and 13C NMR revealed the tautomeric structures. hCA I and hCA II isozymes were purified from human erythrocytes and inhibitory effects of newly synthesized sulfonamides on esterase activities of these isoenzymes have been studied. The Ki values of compounds were 0.062–1.278 μM for hCA I and 0.012–0.379 μM for hCA II. The inhibition effects of 7 for hCA I and 4 for hCA II isozymes were almost in nanomolar concentration range.  相似文献   
45.
The Persian Lizard, Iranolacerta brandtii, was until recently considered to be restricted to north-western Iran (Azerbaijan and Esfahan provinces). However, two recent studies have revealed the existence of populations in Eastern Anatolia, extending the range of this species for about 230?km westwards. The fragmented distribution of this species has been considered to be a consequence of the climatic oscillations during the Pleistocene and Holocene, which created events of alternating contact and isolation of populations in distinct glacial refugia. According to our obtained genealogy derived from three mitochondrial fragments (12S rRNA, 16S rRNA and cytb), the Turkish specimens cluster together but form an independent clade, sister to the individuals from Tabriz in Iran. The separation of these two clades is concurrent with the cladogenesis between the Esfahan and Ardabil clades, estimated to have taken place during the late Holocene.  相似文献   
46.
The Greater Flamingo Phoenicopterus roseus is a waterbird commonly found in saline and brackish lagoons throughout the Mediterranean Region. We have gathered existing data on Greater Flamingos in Turkey and carried out field surveys to present the most up to date information on wintering (1999–2014) and breeding (1969– 2014). The wintering population of flamingos shows an increasing trend with 54,947±20,794 individuals mainly concentrated in the Gediz, Büyük Menderes and Çukurova deltas, respectively. Breeding attempts were recorded in at least seven wetlands in Turkey in the past, yet after 1999 most of the colonies were abandoned due to basin scale intensive water management practices in Central Anatolia. Currently, only Tuz Lake and Gediz Delta are used as regular breeding sites, while breeding has been recorded sporadically in Ac?göl and Ak?ehir Lakes. The breeding colony of Tuz Lake is of prime importance at the Mediterranean scale, with the number of young chicks in 2011, 2012 and 2013 accounting for the highest number of fledglings in the Mediterranean Region and West Africa (18,418, 20,274 and 20,292 respectively). Finally, building upon the previous findings about Turkey and the western Mediterranean metapopulation links, recent resightings of Turkish flamingos (despite the limited numbers) confirm post-fledging and natal dispersal reaching the western Mediterranean Basin and West Africa. Flamingos from Turkey were also found to disperse to Israel and to a region outside the known flyways of the western Mediterranean and West African flamingos (i.e. to Israel and UAE). Thus, Turkey, due to its geographic position, appears to be a crossroad between the western and eastern Mediterranean Region and southwest Asia.  相似文献   
47.
Onychopterocheilus sarikamisensis sp. n. is described and illustrated from eastern Turkey. The species is related to O. hellenicus (Morawitz, 1885) but differs by the shape of the clypeus and antennae, and by the pale colouration of the maculations.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:A3E75353-EC16-458F-908FAB9240E8016B  相似文献   
48.
This study aimed to investigate the ability of curcumin to convert asparagine into acrylamide during heating at different temperatures. Binary and ternary model systems of asparagine–curcumin and asparagine–curcumin–fructose were used to determine the role of curcumin on acrylamide formation in competitive and uncompetitive reaction conditions. The results indicated that curcumin could potentially contribute to acrylamide formation under long-term heating conditions as long as asparagine was present in the medium. The amount of acrylamide formed in the ternary system was slightly higher than in the binary system during heating (p < 0.05), because of the higher concentrations of carbonyl compounds initially available. The kinetic trends were similar in both model systems evidencing that fructose reacted with asparagine more rapidly than curcumin. The data reveal that acrylamide formation in the temperature range of 150–200°C obeys Arrhenius law with activation energy of 79.1 kJ/mole. Data of this work showed the possibility that antioxidants having a carbonyl compound can react directly with ASN leading to acrylamide. The addition of antioxidants to foods may increase the formation of acrylamide upon long-term heating if free sugar concentration is low and ASN concentration is relatively high.  相似文献   
49.
An on-line flow injection pre-concentration-flame atomic absorption spectrometry method was developed to determine trace zinc in water (tap, dam, and well water), biological (hair and nail), and liver samples. As a solid phase extractant, a synthesized new chelating resin, poly(2-thiozylmethacrylamide-co-divinylbenzene-co-2-acrylamido-2-methyl-1-propane sulfonic acid) was used. The resin was characterized by Fourier transform infrared spectroscopy, elemental analysis, and surface area by nitrogen sorption. A pre-concentration factor of 40-fold for a sample volume of 12.6 mL was obtained by using the time-based technique. The detection limit for the pre-concentration method was found to be 2.2 μg L?1. The precision (as RSD,%) for 10 replicate determinations at the 0.04 μg mL?1 Zn concentration was 1.2%. The calibration graph using the pre-concentration system for zinc was linear with a correlation coefficient of 0.998 in the concentration range from 0.005 to 0.05 μg mL?1. The applicability and accuracy of the developed method were estimated by the analysis spiked water, biological, liver samples (83–105%), and also certified reference material TMDA-70 (fortified lake water) and SPS-WW1 Batch 111-Wastewater. The results were in agreement with the certified values.  相似文献   
50.
Interferons are important proteins for the immune system because of their antiviral, anti‐proliferating and immunomodulatory activities. Therapeutic value of these proteins against certain types of tumors caused interest and investigations aimed to obtain highly purified interferons. Molecular imprinting is an efficient method for purification with high selectivity, specificity and good reproducibility. In this study, we utilized advantages of molecular imprinting technique for the purification of interferon from human gingival fibroblast culture. For this purpose, interferon α‐2b imprinted poly(hydroxyethyl methacrylate) cryogel (hIFN‐α‐MIP) was prepared. Optimum adsorption conditions were determined, and maximum adsorption capacity of hIFN‐α‐MIP cryogel was found as 254.8 × 104 IU/g from aqueous solution. All interferon measurements are expressed as International Unit (IU), which is a unit measurement used to quantify biologically active substances like interferon based on their biological activity or effect. Selectivity experiments were performed using competitive proteins and repeated adsorption–desorption studies showed that the adsorption capacity maintained almost at a constant value after ten cycles. For the purification of interferon from human gingival fibroblast culture, fast protein liquid chromatography was used and the specific activity of the purified interferon α‐2b on HeLa cell line was found between the values 3.45 × 108 IU/mg and 3.75 × 108 IU/mg. The results are promising, and the molecular imprinting technique is effective for the purification of interferon α‐2b. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号