全文获取类型
收费全文 | 4253篇 |
免费 | 264篇 |
国内免费 | 632篇 |
出版年
2023年 | 59篇 |
2022年 | 71篇 |
2021年 | 103篇 |
2020年 | 107篇 |
2019年 | 128篇 |
2018年 | 161篇 |
2017年 | 122篇 |
2016年 | 122篇 |
2015年 | 135篇 |
2014年 | 199篇 |
2013年 | 323篇 |
2012年 | 190篇 |
2011年 | 167篇 |
2010年 | 160篇 |
2009年 | 195篇 |
2008年 | 204篇 |
2007年 | 188篇 |
2006年 | 142篇 |
2005年 | 152篇 |
2004年 | 171篇 |
2003年 | 114篇 |
2002年 | 163篇 |
2001年 | 140篇 |
2000年 | 159篇 |
1999年 | 119篇 |
1998年 | 103篇 |
1997年 | 93篇 |
1996年 | 81篇 |
1995年 | 78篇 |
1994年 | 78篇 |
1993年 | 94篇 |
1992年 | 85篇 |
1991年 | 71篇 |
1990年 | 55篇 |
1989年 | 30篇 |
1988年 | 34篇 |
1987年 | 37篇 |
1986年 | 28篇 |
1985年 | 58篇 |
1984年 | 43篇 |
1983年 | 40篇 |
1982年 | 59篇 |
1981年 | 44篇 |
1980年 | 42篇 |
1979年 | 34篇 |
1978年 | 36篇 |
1977年 | 37篇 |
1976年 | 36篇 |
1975年 | 24篇 |
1973年 | 14篇 |
排序方式: 共有5149条查询结果,搜索用时 31 毫秒
31.
《Harmful algae》2017
Azaspiracids (AZA) are a group of food poisoning phycotoxins that are known to accumulate in shellfish. They are produced by some species of the planktonic dinophycean taxon Amphidomataceae. Azaspiracids have been first discovered in Ireland but are now reported in shellfish from numerous global sites thus showing a wide distribution. In shellfish samples collected in 2009 near Huelva (Spain), AZA was also found along the Andalusian Atlantic coast for the first time. Analysis using LC–MS/MS revealed the presence of two different AZA analogues in different bivalve shellfish species (Chamelea gallina, Cerastoderma edule, Donax trunculus, and Solen vagina). In a number of samples, AZA levels exceeded the EU regulatory level of 160 μg AZA-1 eq. kg−1 (reaching maximum levels of >500 μg AZA-1 eq. kg−1 in Chamelea gallina and >250 μg AZA-1 eq. kg−1 in Donax trunculus) causing closures of some local shellfish production areas. One dinophyte strain established from the local plankton during the AZA contamination period and determined as Amphidoma languida was in fact toxigenic, and its AZA profile disclosed it as the causative species: it contained AZA-2 as the main compound and the new compound AZA-43 initially detected in the shellfish. AZA-43 had the same mass as AZA-3, but produced different collision induced dissociation (CID) spectra. High resolution mass spectrometric measurements indicated that there is an unsaturation in the H, I ring system of AZA-43 distinguishing it from the classical AZA such as AZA-1, -2, and -3. Furthermore, the Spanish strain was different from the previously reported AZA profile of the species that consist of AZA-38 and AZ-39. In molecular phylogenetics, the Andalusian strain formed a monophyletic group together with other strains of Am. languida, but ITS sequences data revealed surprisingly high intragenomic variability. The first Andalusian case of AZA contamination of shellfish above the EU regulatory limit reported here clearly revealed the risk of azaspiracid poisoning (AZP) for this area and also for the Atlantic coast of Iberia and North Africa. The present study underlines the need for continuous monitoring of AZA and the organisms producing such toxins. 相似文献
32.
33.
Yoshinobu Hoashi 《Mycoscience》2008,49(6):385-387
Psathyrella turcosomarginata is described and illustrated as a new species from Japan (Fukuoka Prefecture, Kyushu). This species is assigned to section
Spintrigerae because of its lack of pleurocystidia and basidiome habit. It is characterized by having fairly large basidiomes, a distinct
sulcate-striate pileal margin, and cheilocystidia with mucoid deposits that stain bluish green in ammonia solution. 相似文献
34.
GC Wood 《New Zealand journal of zoology.》2013,40(3):186-195
Abstract The Westland petrel (Procellaria westlandica) is an endemic New Zealand species and one of the very few burrowing seabird species still breeding on mainland New Zealand. It nests only on a series of coastal ridgelines near to Punakaiki on the West Coast of the South Island. Between 2002 and 2005, surveys were undertaken at 28 of the 29 known colonies. The area occupied by the colonies was 73 ha; most colonies had fewer than 50 burrows, but six colonies had 201–500 burrows and four colonies had more than 1000 burrows. We find that the current breeding range of Westland petrel and the location of individual colonies are similar to those reported in both the 1950s and 1970s. Based on total burrow counts at 28 colonies and burrow occupancy rates determined by annual monitoring, the annual breeding population is estimated to be between 2954 and 5137 breeding pairs. 相似文献
35.
36.
《Journal of Asia》2021,24(3):550-554
Diaulota koreana Yoo and Ahn new species is described in the intertidal zones of the southern part of the Korean peninsula and illustrations of diagnostic characters are presented. A cladistic analysis of the Liparocephalini based on 50 adult characters suggests that the new species belongs to the genus Diaulota Casey within the Liparocephalini. Similarities and differences among the liparocephaline genera are presented. Phylogenetic relationships of Diaulota koreana Yoo and Ahn new species among the Liparocephalini are briefly discussed. 相似文献
37.
38.
39.
Two new oleanane-type triterpene saponins, identified as 16α-hydroxy-22-O-angeloyl-23-formyl-28,31-dihydroxymethylene-olean-12-ene-3β-O-{β-d-galactopyranosyl-(1 → 2)[β-d-xylopyranosyl-(1 → 2)-α-l-arabinopyranosyl(1 → 3)]-β-d-glucopyranosiduronic acid} (oleiferasaponin B1, 1) and 22-O-hydrocinnamoyl-23-formyl-28-dihydroxymethylene-olean-12-ene-3β-O-{β-d-glucopyranosyl-(1 → 2)[β-d-xylopyranosyl-(1 → 2)-α-l-arabinopyranosyl(1 → 3)]-β-d-glucopyranosiduronic acid} (oleiferasaponin B2, 2), were isolated from the seed cake of Camellia oleifera Abel. Their structures were established by extensive 1D- and 2D-NMR experiments along with TOF-MS analysis and acid hydrolysis. The cytotoxicity of the isolated compounds was evaluated in four human carcinoma cell lines: A 549, SK-OV-3, SK-MEL-2 and HCT15. Both compounds 1 and 2 exhibited significantly cytotoxic activity with IC50 values of 18.5 μM (A549), 11.3 μM (SK-OV-3), 13.9 μM (SK-MEL-2) and 1.6 μM (HCT15) for 1 and IC50 values of 8.4 μM (A549), 6.3 μM (SK-OV-3), 9.2 μM (SK-MEL-2) and 0.8 μM (HCT15) for 2. In addition, compound 2 showed more effective cytotoxic activity than compound 1. 相似文献
40.
Deena I.J. Newman 《Ethnos》2013,78(1):82-106
Divination has been a well‐studied subject in the field of anthropology. Yet diviners within Western societies have been curiously ignored. Van Dijk's and Pels’ (1996) concept of the ‘politics of perception’ is discussed as a means of under‐standing why this is the case. Redressing this gap, I study the practices and experiences of an American psychic. This ethnographic material helps to move us beyond the patient‐client dialogue to address the internal processes of the diviners themselves. The reflexive exegesis of Elizabeth, an American diviner, reveals the spontaneous, visual nature of her practice and also highlights the role of the senses and emotions in divination. Other examples of sensory experience, such as in cases of blindness, show that those senses deemed lower down’ in the hierarchy of perception can be accurate modes of gaining knowledge of the world. 相似文献