全文获取类型
收费全文 | 5161篇 |
免费 | 393篇 |
国内免费 | 284篇 |
专业分类
5838篇 |
出版年
2024年 | 43篇 |
2023年 | 244篇 |
2022年 | 304篇 |
2021年 | 382篇 |
2020年 | 277篇 |
2019年 | 296篇 |
2018年 | 267篇 |
2017年 | 195篇 |
2016年 | 158篇 |
2015年 | 251篇 |
2014年 | 278篇 |
2013年 | 330篇 |
2012年 | 229篇 |
2011年 | 222篇 |
2010年 | 176篇 |
2009年 | 222篇 |
2008年 | 227篇 |
2007年 | 222篇 |
2006年 | 211篇 |
2005年 | 172篇 |
2004年 | 145篇 |
2003年 | 131篇 |
2002年 | 98篇 |
2001年 | 70篇 |
2000年 | 43篇 |
1999年 | 50篇 |
1998年 | 40篇 |
1997年 | 37篇 |
1996年 | 55篇 |
1995年 | 34篇 |
1994年 | 35篇 |
1993年 | 29篇 |
1992年 | 31篇 |
1991年 | 24篇 |
1990年 | 24篇 |
1989年 | 25篇 |
1988年 | 20篇 |
1986年 | 10篇 |
1985年 | 20篇 |
1984年 | 24篇 |
1983年 | 14篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1980年 | 18篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1976年 | 17篇 |
1975年 | 17篇 |
1974年 | 9篇 |
1973年 | 12篇 |
排序方式: 共有5838条查询结果,搜索用时 15 毫秒
1.
2.
Bacopa monniera Wettst. (BM, syn. Herpestis monniera L; Scrophulariaceae), is an Ayurvedic drug used as a rasayana. Its fresh juice was earlier reported to have significant antiulcerogenic activity. In continuation, methanolic extract of BM (BME) standardized to bacoside-A content (percentage-38.0 ± 0.9), when given in the dose of 10–50 mg/kg, twice daily for 5 days, showed dose-dependent anti-ulcerogenic on various gastric ulcer models induced by ethanol, aspirin, 2 h cold restraint stress and 4 h pylorus ligation. BME in the dose of 20 mg/kg, given for 10 days, twice daily showed healing effects against 50% acetic acid-induced gastric ulcers. Further work was done to investigate the possible mechanisms of its action by studying its effect on various mucosal offensive acid-pepsin secretion and defensive factors like mucin secretion, mucosal cell shedding, cell proliferation and antioxidant activity in rats. BME 20 mg/kg showed no effect on acid-pepsin secretion, increased mucin secretion, while it decreased cell shedding with no effect on cell proliferation. BME showed significant antioxidant effect per se and in stressed animals. Thus, the gastric prophylactic and curative effects of BME may be due to its predominant effect on mucosal defensive factors. 相似文献
3.
《Cell reports》2020,30(1):61-68.e4
- Download : Download high-res image (250KB)
- Download : Download full-size image
4.
5.
6.
Larval hemolymph tyrosinase activity in Drosophila melanogaster was detected with high performance liquid chromatography with electrochemical detection. The enzyme hydroxylated L-tyrosine, and oxidized the diphenol substrates L-dopa and dopamine. In larvae of a selected immune-reactive strain the rates of tyrosine hydroxylation, dopa oxidation, and dopamine oxidation were markedly increased during the early stages of melanotic encapsulation of the eggs of the parasitic wasp Leptopilina boulardi. Tyrosinase activity was not modified in parasitized larvae of a selected susceptible strain of D. melanogaster, in which hosts the parasitoids developed unmolested. During the same period of parasitization, the amount of free tyrosine in immune reactive larvae was approximately three times higher than in susceptible hosts. These data indicate that the tyrosinase system of the immune reactive strain is activated during parasitization, and this results in the synthesis of some precursors which ultimately produce a melanotic and sclerotic capsule around the eggs of the parasite. Based on known genetic information of the enzyme system in Drosophila, it appears that at least two genes may be involved in the activation process, one associated with the proenzyme for monophenol oxidase activity, and the second with the proenzyme for diphenol oxidase activity. 相似文献
7.
《Cell reports》2020,30(5):1530-1541.e4
- Download : Download high-res image (102KB)
- Download : Download full-size image
8.
Ahtiainen Jari J.; Alatalo Rauno V.; Kortet Raine; Rantala Markus J. 《Behavioral ecology》2004,15(4):602-606
A simple version of the immunocompetence handicap hypothesizesthat through condition-dependence, the size of the sexual traitmay be positively related to immune function at the populationlevel. In the present study, we investigated the relationshipbetween sexual advertisement and immune function in a naturalpopulation of male wolf spiders, Hygrolycosa rubrofasciata (Araneae:Lycosidae). Males of H. rubrofasciata have a costly and condition-dependentacoustic signal, courtship drumming. In the mating season, malesdrum against dry leaves while wandering around the habitat searchingfor receptive females. Males increase their mating success byincreasing their drumming rate and mobility. We used drummingrate and mobility measured without female proximity as estimatesof sexual advertisement. As estimates of male immune function,we used encapsulation rate and lytic activity. Encapsulationrate is a common challenging technique, which measures immuneresponse against multicellular parasites. Lytic activity isa monitoring technique, which measures immune response againstpathogens. Our results show that males with higher drummingrate had higher encapsulation rate. This suggests that femalesmight use drumming rate as a signal for choosing males withgood immunocompetence. Moreover, our results show that maleswith higher mobility had higher lytic activity. As females aremore likely to encounter those males that have higher mobility,this might also select males with better immune function. Ourresults suggest that the immunocompetence handicap might workalso among spiders, although we could not assess the causalityof the relationship between sexual selection and immune functionin this correlational study. 相似文献
9.
10.
Sabrina Forveille Heng Zhou Allan Sauvat Lucillia Bezu Kevin Müller Peng Liu Laurence Zitvogel Gérard Pierron ?ystein Rekdal Oliver Kepp Guido Kroemer 《Cell cycle (Georgetown, Tex.)》2015,14(21):3506-3512
The oncolytic peptide LTX-315 has been designed for killing human cancer cells and turned out to stimulate anti-cancer immune responses when locally injected into tumors established in immunocompetent mice. Here, we investigated the question whether LTX-315 induces apoptosis or necrosis. Transmission electron microscopy or morphometric analysis of chromatin-stained tumor cells revealed that LTX-315 failed to induce apoptotic nuclear condensation and rather induced a necrotic phenotype. Accordingly, LTX-315 failed to stimulate the activation of caspase-3, and inhibition of caspases by means of Z-VAD-fmk was unable to reduce cell killing by LTX-315. In addition, 2 prominent inhibitors of regulated necrosis (necroptosis), namely, necrostatin-1 and cycosporin A, failed to reduce LTX-315-induced cell death. In conclusion, it appears that LTX-315 triggers unregulated necrosis, which may contribute to its pro-inflammatory and pro-immune effects. 相似文献