全文获取类型
收费全文 | 26299篇 |
免费 | 1931篇 |
国内免费 | 5篇 |
出版年
2024年 | 31篇 |
2023年 | 253篇 |
2022年 | 323篇 |
2021年 | 628篇 |
2020年 | 480篇 |
2019年 | 538篇 |
2018年 | 982篇 |
2017年 | 812篇 |
2016年 | 1000篇 |
2015年 | 1119篇 |
2014年 | 1247篇 |
2013年 | 1746篇 |
2012年 | 2067篇 |
2011年 | 2151篇 |
2010年 | 1261篇 |
2009年 | 990篇 |
2008年 | 1572篇 |
2007年 | 1499篇 |
2006年 | 1410篇 |
2005年 | 1095篇 |
2004年 | 1060篇 |
2003年 | 964篇 |
2002年 | 844篇 |
2001年 | 610篇 |
2000年 | 676篇 |
1999年 | 426篇 |
1998年 | 222篇 |
1997年 | 159篇 |
1996年 | 143篇 |
1995年 | 137篇 |
1994年 | 122篇 |
1993年 | 117篇 |
1992年 | 161篇 |
1991年 | 152篇 |
1990年 | 115篇 |
1989年 | 100篇 |
1988年 | 92篇 |
1987年 | 83篇 |
1986年 | 75篇 |
1985年 | 77篇 |
1984年 | 65篇 |
1983年 | 53篇 |
1982年 | 59篇 |
1981年 | 51篇 |
1980年 | 47篇 |
1979年 | 54篇 |
1978年 | 46篇 |
1977年 | 31篇 |
1975年 | 40篇 |
1974年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
31.
32.
33.
Rocío García-Pérez Beatriz Revilla-Nuin Carlos M. Martínez Angel Bernabé-García Alberto Baroja Mazo Pascual Parrilla Paricio 《PloS one》2015,10(12)
Associated liver partition and portal vein ligation for staged hepatectomy (ALPPS) is a two-stage hepatectomy technique which can be associated with a hypertrophic stimulus on the future liver remnant (FLR) stronger than other techniques–such as portal vein ligation (PVL). However, the reason of such hypertrophy is still unclear, but it is suggested that liver transection combined with portal vein ligation (ALPPS) during the first stage of this technique may play a key role. The aim of this study is to compare the hypertrophic stimulus on the FLR and the clinical changes associated with both ALPPS and PVL in a rat surgical model. For this purpose, three groups of SD rats were used, namely ALPPS (n = 30), PVL (n = 30) and sham-treated (n = 30). The second stage of ALPPS (hepatectomy of the atrophic lobes), was performed at day 8. Blood and FLR samples were collected at 1, 24, 48 hours, 8 days and 12 weeks after the surgeries. ALPPS provoked a greater degree of hypertrophy of the FLR than the PVL at 48 hours and 8 days (p<0.05). The molecular pattern was also different, with the highest expression of IL-1β at 24h, IL-6 at 8 days, and HGF and TNF-α at 48 hours and 8 days (p<0.05). ALPPS also brought about a mild proliferative stimulus at 12 weeks, with a higher expression of HGF and TGF-β (p<0.05) than PVL. Clinically, ALPPS caused a significant liver damage during the first 48 hours, with a recovery of liver function at day 8. In conclusion, ALPPS seems to induce higher functional hypertrophy on the FLR than PVL at day 8. Such regenerative response seems to be leaded by a complex interaction between pro-mitogenic (IL-6, HGF, TNF-α) and antiproliferative (IL1-β and TGF-β) cytokines. 相似文献
34.
35.
36.
37.
G. N. Reiner L. Delgado-Marín N. Olguín S. Sánchez-Redondo M. Sánchez-Borzone E. Rodríguez-Farré C. Suñol D. A. García 《Cell biochemistry and biophysics》2013,67(2):515-525
Phenol compounds, such as propofol and thymol, have been shown to act on the GABAA receptor through interaction with specific sites of this receptor. In addition, considering the high lipophilicity of phenols, it is possible that their pharmacological activity may also be the result of the interaction of phenol molecules with the surrounding lipid molecules, modulating the supramolecular organization of the receptor environment. Thus, in the present study, we study the pharmacological activity of some propofol- and thymol-related phenols on the native GABAA receptor using primary cultures of cortical neurons and investigate the effects of these compounds on the micro viscosity of artificial membranes by means of fluorescence anisotropy. The phenol compounds analyzed in this article are carvacrol, chlorothymol, and eugenol. All compounds were able to enhance the binding of [3H]flunitrazepam with EC50 values in the micromolar range and to increase the GABA-evoked Cl? influx in a concentration-dependent manner, both effects being inhibited by the competitive GABAA antagonist bicuculline. These results strongly suggest that the phenols studied are positive allosteric modulators of this receptor. Chlorothymol showed a bell-type effect, reducing its positive effect at concentrations >100 μM. The concentrations necessary to induce positive allosteric modulation of GABAA receptor were not cytotoxic. Although all compounds were able to decrease the micro viscosity of artificial membranes, chlorothymol displayed a larger effect which could explain its effects on [3H]flunitrazepam binding and on cell viability at high concentrations. Finally, it is suggested that these compounds may exert depressant activity on the central nervous system and potentiate the effects of general anesthetics. 相似文献
38.
39.
Summary Lactic acid produced by continuous culture of L.casei in an upflow packed bed reactor, was recovered with Amberlite IRA 400 in a fluidized bed column. Bed expansions of 1.25 and 2.25 were applied. Reutilization did not alter the capability of net recovery of 0.048 ± 0.01 g lactic acid/g resin. When 2200 cm/h of ascensional velocity was used, (bed expansion of 2.25), the resin adsorbed 39.3% of the initial lactic acid and 63.5% was eluted. This resin supported the highest exchange capacity of 0.126 g lactic acid/g resin. Applying high flow rates, the process has potential industrial applications due to the short time employed. 相似文献
40.
Frequency of infection by Cryptosporidium sp. in 1,039 faecal smears stained by Ziehl-Neelsen, obtained from undernourished patients of a Nutritional Recovery Center and an ambulatory undernourished center from the Fifth Region, Chile, were studied. All underwent a coproparasitological examination by the modified Telemann method. Thirty eight (3.7%) patients infected by the parasite were detected, with an overall frequency of 8.5% among patients of the Nutritional Recovery Center and 1.9% among the ambulatory patients; this difference was statistically significant. The highest percentage of positive results were detected among the younger milk feeding infants. Also the percentage of difference among these and the older milk feeding infants (3.7%) was statistically significant. Association of Cryptosporidium sp. and Giardia lamblia was observed in 6 ambulatory patients (2.3%). 相似文献