全文获取类型
收费全文 | 25234篇 |
免费 | 15525篇 |
国内免费 | 3篇 |
专业分类
40762篇 |
出版年
2023年 | 12篇 |
2022年 | 85篇 |
2021年 | 387篇 |
2020年 | 2183篇 |
2019年 | 3712篇 |
2018年 | 3813篇 |
2017年 | 4094篇 |
2016年 | 4075篇 |
2015年 | 3976篇 |
2014年 | 3616篇 |
2013年 | 4040篇 |
2012年 | 1703篇 |
2011年 | 1422篇 |
2010年 | 3009篇 |
2009年 | 1773篇 |
2008年 | 642篇 |
2007年 | 253篇 |
2006年 | 225篇 |
2005年 | 276篇 |
2004年 | 256篇 |
2003年 | 244篇 |
2002年 | 234篇 |
2001年 | 252篇 |
2000年 | 187篇 |
1999年 | 128篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 18篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1983年 | 3篇 |
1980年 | 5篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1971年 | 3篇 |
1959年 | 4篇 |
1958年 | 3篇 |
1957年 | 7篇 |
1953年 | 2篇 |
1952年 | 9篇 |
1951年 | 3篇 |
1950年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
H. Chaouch O. Hamida‐Ben Abdallah M. Ghorbel O. Jarboui 《Zeitschrift fur angewandte Ichthyologie》2013,29(4):796-800
Annular seabream, Diplodus annularis (Linnaeus, 1758), were caught off the coast of the Gulf of Gabes (Southern Tunisia, Central Mediterranean) between April 2008 and March 2010 by commercial catches. With a total 2066 specimens the fish ranged in size from 7.7 cm to 18.5 cm total length and from 7.5 g to 123.3 g in weight. Changes in biological parameters (weight, length, gonadosomatic index, hepatosomatic index and condition factor) were examined in order to provide information on the spawning period and reproductive cycle in the gulf. Overall sex ratio was 1 : 1.52 in favour of females. The reproductive season extends from March to June, with a spawning activity peak in May. Total length at sexual maturity was 10.5 ± 0.22 cm (males) and 10.6 ± 0.3 cm (females). The results of this study could help to establish a recommended minimum capture size. 相似文献
92.
93.
Lidia Zielińska Julia Byczyk Natalia Rymelska Natasza Borodynko Henryk Pospieszny Beata Hasiów‐Jaroszewska 《Journal of Phytopathology》2012,160(11-12):685-689
Electron microscopy studies were carried out to investigate the cytopathological changes induced in tomato leaves by Tomato torrado virus (ToTV) that infects tomato plants worldwide causing severe necrotic symptoms. Plants infected with one of the Polish isolates of ToTV were used for cytopathological research. The results revealed severe cellular alterations, especially in Solanum lycopersicum. Moreover, it was shown that crystalline aggregates of virions occurred not only within the phloem cells as it has been previously reported. 相似文献
94.
Hyung‐Ju Cho Jae Young Choi Yu‐Mi Yang Jeong Hee Hong Chang‐Hoon Kim Heon Young Gee Hyun Jae Lee Dong Min Shin Joo‐Heon Yoon 《Journal of cellular biochemistry》2010,109(6):1254-1263
Adequate fluid secretion from airway mucosa is essential for maintaining mucociliary clearance, and fluid hypersecretion is a prominent feature of inflammatory airway diseases such as allergic rhinitis. House dust mite extract (HDM) has been reported to activate protease‐activated receptors (PARs), which play various roles in airway epithelia. However, the role of HDM in regulating ion transporters and fluid secretion has not been investigated. We examined the effect of HDM on ion transport in human primary nasal epithelial cells. The Ca2+‐sensitive dye Fura2‐AM was used to determine intracellular Ca2+ concentration ([Ca2+]i) by means of spectrofluorometry in human normal nasal epithelial cells (NHNE). Short‐circuit current (Isc) was measured using Ussing chambers. Fluid secretion from porcine airway mucosa was observed by optical measurement. HDM extract (10 µg/Ml) effectively cleaved the PAR‐2 peptide and induced an increase of [Ca2+]i that was abolished by desensitization with trypsin, but not with thrombin. Apical application of HDM‐induced Isc sensitive to both a cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor and a Ca2+‐activated Cl? channel (CaCC) inhibitor. HDM extract also stimulated fluid secretion from porcine airway mucosa. HDM extract activated PAR‐2 and apical Cl? secretion via CaCC and CFTR, and HDM‐induced fluid secretion in porcine airway mucosa. Our results suggest a role for PAR‐2 in mucociliary clearance and fluid hypersecretion of airway mucosa in response to air‐borne allergens such as HDM. J. Cell. Biochem. 109: 1254–1263, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
95.
Kilyoung Song Sang‐Hwan Hyun Taeyoung Shin Eunsong Lee 《Molecular reproduction and development》2009,76(7):611-619
The objective of this study was to examine the effect of cytochalasin B (CB) and/or demecolcine (Dc) on the remodeling of donor nuclei, nuclear ploidy, and development of somatic cell nuclear transfer (SCNT) and parthenogenetic (PA) pig embryos. SCNT and PA oocytes were either untreated (control), or treated with CB, Dc, or both CB and Dc after electric activation, and then cultured or transferred to surrogates. In SCNT, blastocyst formation was higher after treatment with CB and/or Dc (26–28%) than in the controls (16%). The number of oocytes that formed a single pronucleus (PN) was higher after treatment with Dc (86%) and CB + Dc (86%) than under control conditions (44%) or after treatment with CB (63%). In PA, blastocyst formation was higher after CB treatment (47%) than under control conditions (28%), while the formation of a single PN was higher after treatment with Dc (88%) and CB + Dc (84%) compared to controls (34%). The rate of formation of diploid embryos was higher after treatment with Dc and CB + Dc than under control conditions. Dc treatment resulted in a farrowing rate of 50% with 1.1% production efficiency, while controls showed a farrowing rate of 37.5% and a production efficiency of 0.7%. The results of our study demonstrate that post‐activation treatment with Dc improves preimplantation development and supports normal in vivo development of SCNT pig embryos, probably because Dc induces formation of a single PN and this leads to normal nuclear ploidy. Mol. Reprod. Dev. 76: 611–619, 2009. © 2008 Wiley‐Liss, Inc. 相似文献
96.
97.
98.
Gradients of disturbance and environmental conditions shape coral community structure for south‐eastern Indian Ocean reefs 下载免费PDF全文
Jens Zinke James P. Gilmour Rebecca Fisher Marji Puotinen Joseph Maina Emily Darling Michael Stat Zoe T. Richards Timothy R. McClanahan Maria Beger Cordelia Moore Nicholas A. J. Graham Ming Feng Jean‐Paul A. Hobbs Scott N. Evans Stuart Field George Shedrawi Russ C. Babcock Shaun K. Wilson 《Diversity & distributions》2018,24(5):605-620
99.
Ping Liu Xiaoming Zhang Meigui Huang Shiqing Song John Nsor‐Atindana 《Journal of peptide science》2012,18(10):626-634
The formation mechanism of Maillard peptides was explored in Maillard reaction through diglycine/glutathione(GSH)/(Cys‐Glu‐Lys‐His‐Ile‐Met)–xlyose systems by heating at 120 °C for 30–120 min. Maximum fluorescence intensity of Maillard reaction products (MRPs) with an emission wavelength of 420~430 nm in all systems was observed, and the intensity values were proportional to the heating time. Taken diglycine/GSH–[13C5]xylose systems as a control, it was proposed that the compounds with high m/z values of 379 and 616 have the high molecular weight (HMW) products formed by cross‐linking of peptides and sugar. In (Cys‐Glu‐Lys‐His‐Ile‐Met)–xylose system, the m/z value of HMW MRPs was not observed, which might be due to the weak signals of these products. According to the results of gel permeation chromatography, HMW MRPs were formed by Maillard reaction, especially in (Cys‐Glu‐Lys‐His‐Ile‐Met)–xylose system, the percentage of Maillard peptides reached 52.90%. It was concluded that Maillard peptides can be prepared through the cross‐linking of sugar and small peptides with a certain MW range. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
100.
With the purpose of assessing the status of dormancy in seeds of two Begonia species (Begonia lithophila and Begonia guishanensis), freshly matured seeds were given gibberellic acid and moist chilling and allowed to dry after ripening. The seeds were then germinated on media with or without KNO3 at 15, 20, 25, 30 and 18/25°C. All three treatments significantly increased germination percentages. Examination by X‐ray revealed that seeds of both species have a fully developed embryo and thus have no morphological component of dormancy; seeds readily imbibed water and KNO3 solution. Therefore, we conclude that seeds of the two Begonia species have non‐deep physiological dormancy. Although KNO3 significantly increased germination in both species, alternating temperatures did not, suggesting that the most favorable microhabitat for germination is small‐scale disturbances under the forest canopy. 相似文献