全文获取类型
收费全文 | 805847篇 |
免费 | 88962篇 |
国内免费 | 527篇 |
出版年
2018年 | 7656篇 |
2017年 | 7186篇 |
2016年 | 10413篇 |
2015年 | 14386篇 |
2014年 | 16772篇 |
2013年 | 23812篇 |
2012年 | 26646篇 |
2011年 | 27026篇 |
2010年 | 18356篇 |
2009年 | 16696篇 |
2008年 | 23879篇 |
2007年 | 24444篇 |
2006年 | 23086篇 |
2005年 | 22251篇 |
2004年 | 22158篇 |
2003年 | 21250篇 |
2002年 | 20454篇 |
2001年 | 38361篇 |
2000年 | 38552篇 |
1999年 | 30503篇 |
1998年 | 10420篇 |
1997年 | 10823篇 |
1996年 | 10195篇 |
1995年 | 9832篇 |
1994年 | 9562篇 |
1993年 | 9345篇 |
1992年 | 24783篇 |
1991年 | 24037篇 |
1990年 | 23423篇 |
1989年 | 22801篇 |
1988年 | 21164篇 |
1987年 | 19752篇 |
1986年 | 18313篇 |
1985年 | 18133篇 |
1984年 | 15058篇 |
1983年 | 12552篇 |
1982年 | 9521篇 |
1981年 | 8498篇 |
1980年 | 7945篇 |
1979年 | 13483篇 |
1978年 | 10490篇 |
1977年 | 9429篇 |
1976年 | 8530篇 |
1975年 | 9497篇 |
1974年 | 10126篇 |
1973年 | 10023篇 |
1972年 | 8951篇 |
1971年 | 8164篇 |
1970年 | 6971篇 |
1969年 | 6733篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
This study is focused on the possible use of Ceratocystis paradoxa MSR2 native biomass for Cr(VI) biosorption. The influence of experimental parameters such as initial pH, temperature, biomass dosage, initial Cr(VI) concentration and contact time were optimized using batch systems as well as response surface methodology (RSM). Maximum Cr(VI) removal of 68.72% was achieved, at an optimal condition of biomass dosage 2g L−1, initial Cr(VI) concentration of 62.5 mg L−1 and contact time of 60 min. The closeness of the experimental and the predicted values exhibit the success of RSM. The biosorption mechanism of MSR2 biosorbent was well described by Langmuir isotherm and a pseudo second order kinetic model, with a high regression coefficient. The thermodynamic study also revealed the spontaneity and exothermic nature of the process. The surface characterization using FT-IR analysis revealed the involvement of amine, carbonyl and carboxyl groups in the biosorption process. Additionally, desorption efficiency of 92% was found with 0.1 M HNO3. The Cr(VI) removal efficiency, increased with increase in metal ion concentration, biomass concentration, temperature but with a decrease in pH. The size of the MSR2 biosorbent material was found to be 80 μm using particle size analyzer. Atomic force microscopy (AFM) visualizes the distribution of Cr(VI) on the biosorbent binding sites with alterations in the MSR2 surface structure. The SEM-EDAX analysis was also used to evaluate the binding characteristics of MSR2 strain with Cr(VI) metals. The mechanism of Cr(VI) removal of MSR2 biomass has also been proposed. 相似文献
3.
Sight is undoubtedly important for finding and appreciating food, and cooking. Blind individuals are strongly impaired in finding food, limiting the variety of flavours they are exposed to. We have shown before that compared to sighted controls, congenitally blind individuals have enhanced olfactory but reduced taste perception. In this study we tested the hypothesis that congenitally blind subjects have enhanced orthonasal but not retronasal olfactory skills. Twelve congenitally blind and 14 sighted control subjects, matched in age, gender and body mass index, were asked to identify odours using grocery-available food powders. Results showed that blind subjects were significantly faster and tended to be better at identifying odours presented orthonasally. This was not the case when odorants were presented retronasally. We also found a significant group x route interaction, showing that although both groups performed better for retronasally compared to orthonasally presented odours, this gain was less pronounced for blind subjects. Finally, our data revealed that blind subjects were more familiar with the orthonasal odorants and used the retronasal odorants less often for cooking than their sighted counterparts. These results confirm that orthonasal but not retronasal olfactory perception is enhanced in congenital blindness, a result that is concordant with the reduced food variety exposure in this group. 相似文献
4.
5.
Nóra Kutszegi ágnes F. Semsei András Gézsi Judit C. Sági Viktória Nagy Katalin Csordás Zsuzsanna Jakab Orsolya Lautner-Csorba Krisztina Míta Gábor Gábor T. Kovács Dániel J. Erdélyi Csaba Szalai 《PloS one》2015,10(10)
L-asparaginase (ASP) is a key element in the treatment of paediatric acute lymphoblastic leukaemia (ALL). However, hypersensitivity reactions (HSRs) to ASP are major challenges in paediatric patients. Our aim was to investigate genetic variants that may influence the risk to Escherichia coli-derived ASP hypersensitivity. Sample and clinical data collection was carried out from 576 paediatric ALL patients who were treated according to protocols from the Berlin—Frankfurt—Münster Study Group. A total of 20 single nucleotide polymorphisms (SNPs) in GRIA1 and GALNT10 genes were genotyped. Patients with GRIA1 rs4958351 AA/AG genotype showed significantly reduced risk to ASP hypersensitivity compared to patients with GG genotype in the T-cell ALL subgroup (OR = 0.05 (0.01–0.26); p = 4.70E-04), while no such association was found in pre-B-cell ALL. In the medium risk group two SNPs of GRIA1 (rs2055083 and rs707176) were associated significantly with the occurrence of ASP hypersensitivity (OR = 0.21 (0.09–0.53); p = 8.48E-04 and OR = 3.02 (1.36–6.73); p = 6.76E-03, respectively). Evaluating the genders separately, however, the association of rs707176 with ASP HSRs was confined only to females. Our results suggest that genetic variants of GRIA1 might influence the risk to ASP hypersensitivity, but subgroups of patients can differ significantly in this respect. 相似文献
6.
Mathias Kaiser Benedikt Kirsch Hannah Hauser Désirée Schneider Ingrid Seu?-Baum Francisco M. Goycoolea 《PloS one》2015,10(10)
Capsaicin has known health beneficial and therapeutic properties. It is also able to enhance the permeability of drugs across epithelial tissues. Unfortunately, due to its pungency the oral administration of capsaicin is limited. To this end, we assessed the effect of nanoencapsulation of capsaicin, under the hypothesis that this would reduce its pungency. Core-shell nanocapsules with an oily core and stabilized with phospholipids were used. This system was used with or without chitosan coating. In this work, we investigated the in vitro release behavior of capsaicin-loaded formulations in different physiological media (including simulated saliva fluid). We also evaluated the influence of encapsulation of capsaicin on the cell viability of buccal cells (TR146). To study the changes in pungency after encapsulation we carried out a sensory analysis with a trained panel of 24 students. The in vitro release study showed that the systems discharged capsaicin slowly in a monotonic manner and that the chitosan coating had an effect on the release profile. The cytotoxic response of TR146 cells to capsaicin at a concentration of 500 μM, which was evident for the free compound, was reduced following its encapsulation. The sensory study revealed that a chitosan coating results in a lower threshold of perception of the formulation. The nanoencapsulation of capsaicin resulted in attenuation of the sensation of pungency significantly. However, the presence of a chitosan shell around the nanoformulations did not mask the pungency, when compared with uncoated systems. 相似文献
7.
8.
9.
10.