全文获取类型
收费全文 | 2697篇 |
免费 | 156篇 |
国内免费 | 209篇 |
专业分类
3062篇 |
出版年
2024年 | 14篇 |
2023年 | 53篇 |
2022年 | 54篇 |
2021年 | 85篇 |
2020年 | 58篇 |
2019年 | 65篇 |
2018年 | 100篇 |
2017年 | 87篇 |
2016年 | 118篇 |
2015年 | 90篇 |
2014年 | 129篇 |
2013年 | 197篇 |
2012年 | 186篇 |
2011年 | 210篇 |
2010年 | 142篇 |
2009年 | 116篇 |
2008年 | 142篇 |
2007年 | 131篇 |
2006年 | 124篇 |
2005年 | 143篇 |
2004年 | 140篇 |
2003年 | 153篇 |
2002年 | 97篇 |
2001年 | 83篇 |
2000年 | 72篇 |
1999年 | 59篇 |
1998年 | 22篇 |
1997年 | 18篇 |
1996年 | 9篇 |
1995年 | 4篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 14篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1979年 | 5篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1956年 | 3篇 |
排序方式: 共有3062条查询结果,搜索用时 0 毫秒
31.
Laçine Aksoy Erdi Kolay Yasin Ağılönü Zeyneb Aslan Mustafa Kargıoğlu 《Saudi Journal of Biological Sciences》2013,20(3):235-239
Thermopsis turcica, endemic to Turkey, is in danger of extinction. Studies on this species are very few due to the fact that it was only discovered in 1983 and grows in a small circumscribed area in Turkey. In this study, free radical scavenging activity, total phenolic content, total oxidant status (TOS), and total antioxidant status (TAS) of methanol (TTM) and acetone (TTA) extracts of T. turcica were measured spectroscopically. Free radical scavenging activity was determined according to the elimination of DPPH radicals and total phenol content was determined by the Folin–Ciocalteu reaction. Total oxidant status (TOS) and total antioxidant status (TAS) were measured with commercially available kits. Methanol and acetone extracts of T. turcica were found to have a specific radical scavenging effect. This effect was found to be related to the total phenolic content of the extracts. Since the TTA had a higher phenolic content than the methanol extract, it had a stronger radical scavenging effect. In addition, the total antioxidant capacity of the methanol extract was observed to be higher than that of its acetone counterpart. As a result, due to its antioxidative properties, T. turcica is thought to be a natural source of antioxidants. 相似文献
32.
Demir Ersin Nedzvetsky Viktor S. Ağca Can Ali Kirici Mahinur 《Neurochemical research》2020,45(10):2385-2397
Neurochemical Research - Diabetes mellitus is a prevalent metabolic disorder associated with multiple complications including neuropathy, memory loss and cognitive decline. Despite a long history... 相似文献
33.
The development, survival and reproduction of the cabbage aphid, Brevicoryne brassicae (L.) were evaluated at three constant temperatures (20, 25 and 30°C) on cabbage, cauliflower, red cabbage, turnip and radish. The development periods of immature stages ranged from 10.7 d at 20°C to 7.60 d at 30°C for red cabbage. Total percentages of survivorship of immature stages varied from 39.40 and 82.50 within the temperature range of 25–30°C on radish. The average progeny per female was 31.15, 28.95 and 23.77 at 20, 25 and 30°C on cabbage. 相似文献
34.
Ozan Pazvantoğlu Sezgin Güneş Koray Karabekiroğlu Zeynep Yeğin Zehra Erenkuş Seher Akbaş Gökhan Sarısoy Işıl Zabun Korkmaz Ömer Böke Hasan Bağcı Ahmet Rifat Şahin 《Gene》2013
Due to the high heritability of attention-deficit hyperactivity disorder (ADHD), parents of children with ADHD appear to represent a good sample group for investigating the genetics of the disorder. The aim of this study was to investigate the association between ADHD and six polymorphisms in five candidate genes [5-HT2A (rs6311), NET1 (rs2242447), COMT (rs4818), NTF3 (rs6332), SNAP-25 (rs3746544) and (rs1051312)]. We included 228 parents of children diagnosed with ADHD and 109 healthy parents as the control group. The polymorphisms were genotyped using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) assays and analyzed using the chi-square test and the multinomial logit model. SNAP-25 (rs3746544) polymorphism was associated with loading for ADHD, while 5-HT2A (rs6311) and NET1 (rs2242447) polymorphisms were associated with ADHD. On the other hand, there was no significant association between the SNAP-25 (rs1051312), NTF3 (rs6332), or COMT (rs4818) gene polymorphisms and ADHD. 相似文献
35.
36.
Mesut Yeğen 《Ethnic and racial studies》2013,36(1):119-151
This article addresses the ways in which Turkish nationalism has perceived the Kurdish question. It is shown that both Turkish nationalism and the Kurdish question have passed through some paradigmatic moments in the twentieth century. This, I argue, has shaped the way that the Kurdish question has been perceived by Turkish nationalism. While the Kurdish question had been seen by Turkish nationalism mostly in terms of a fatal rivalry between the backward, pre-modern and tribal past and the prosperous present in the first half of the century, it was perceived in terms of a tension between the peripheral economy and national market in the fifties and sixties. In the 1970s, the Kurdish unrest was believed to be a product of communist incitement. Despite this impurity in perception, one thing has remained nearly unchanged for Turkish nationalism: Kurds could become Turkish. In other words, Turkish nationalism of the republican era has principally perceived Kurds as future-Turks. However, the signs in circulation at present indicate that the confidence of Turkish nationalism as to Kurds’ potential of becoming Turkish is not as firm as it used to be. At present, Turkish nationalism seems to be getting prepared to abandon its contention that Kurds are future-Turks. 相似文献
37.
Cenk Saraçoğlu 《Ethnic and racial studies》2013,36(6):1110-1112
This article analyses two dominant discourses of racial politics in Hawai'i and the work they do naturalizing haole (white people or whiteness in Hawai'i) in the islands. The first is the well-worn discourse of racial harmony representing Hawai'i as an idyllic racial paradise with no conflict or inequality. Frequently contrasting the islands with the ‘racist mainland’, this discourse circulates among many communities and is widely referenced. There is also a competing discourse of discrimination against non-locals which contends that haoles and non-local people of colour are disrespected and treated unfairly in Hawai'i. As negative referents for each other, these discourses work to reinforce one another and are historically linked. I suggest that the question of racial politics be reframed towards consideration of the processes of racialization themselves – towards a new way of thinking about racial politics in Hawai'i that breaks free of the not racist/racist dyad. 相似文献
38.
Ahmet R. Oğuz 《The Journal of membrane biology》2013,246(3):183-188
Chalcalburnus tarichi is an anadromous cyprinid fish that has adapted to extreme conditions (salinity 22 ‰, pH 9.8 and alkalinity 153 mEq × l?1) in Lake Van in eastern Turkey. Changes in immunoreactivity of Na+/K+-ATPase in gill tissue and osmolarity and ion levels in plasma were investigated in C. tarichi during reproductive migration. Physicochemical characteristics and ion levels in Lake Van were high compared freshwater. Plasma osmolality and plasma ion concentrations ([Na+], [K+] and [Cl?]) increased after transfer from freshwater to Lake Van. The mitochondria-rich (MR) cells of the gill were stained in both filament and lamellar epithelia of C. tarichi by immunocytochemistry with a specific antiserum for Na+/K+-ATPase in river fish samples. Density and area of MR cells were decreased in lake-adapted fishes. These results indicated that freshwater acclimation capacity is correlated with the size and distribution of MR cells in C. tarichi, in contrast to many teleost fishes. 相似文献
39.
Changes in fatty acid composition, cholesterol and fat‐soluble vitamins were studied during development (fertilized eggs, yolk‐sac larvae, and after yolk resorption of shabbout, Barbus grypus). Significant differences were found in the monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFA), PUFA/saturated fatty acids (SFA), ∑n‐3 and eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA) ratios between eggs and larvae (P < 0.05). Significant differences were also observed in the C14:0, C16:1n‐7, C18:1n‐9, C18:3n‐6, C20:0, C20:4n‐6, C24:0, C24:1, C22:6n‐3 fatty acids between eggs and larvae after yolk‐sac resorption (P < 0.05). Vitamin α‐ Tocopherol and retinol content increased during embryogenesis, but changes were insignificant in retinol acetate, δ‐Tocopherol, K1, K2 and cholesterol content between eggs and larvae after yolk resorption (P > 0.05). 相似文献
40.
Sibel Yılmaz Şerife Tokalıoğlu Serkan Şahan Ahmet Ülgen Ahmet Şahan Cengiz Soykan 《Journal of trace elements in medicine and biology》2013,27(2):85-90
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