全文获取类型
收费全文 | 1149篇 |
免费 | 55篇 |
国内免费 | 42篇 |
专业分类
1246篇 |
出版年
2024年 | 3篇 |
2023年 | 5篇 |
2022年 | 15篇 |
2021年 | 12篇 |
2020年 | 18篇 |
2019年 | 11篇 |
2018年 | 16篇 |
2017年 | 18篇 |
2016年 | 22篇 |
2015年 | 16篇 |
2014年 | 19篇 |
2013年 | 92篇 |
2012年 | 22篇 |
2011年 | 25篇 |
2010年 | 26篇 |
2009年 | 32篇 |
2008年 | 32篇 |
2007年 | 41篇 |
2006年 | 53篇 |
2005年 | 34篇 |
2004年 | 31篇 |
2003年 | 35篇 |
2002年 | 49篇 |
2001年 | 35篇 |
2000年 | 37篇 |
1999年 | 61篇 |
1998年 | 69篇 |
1997年 | 62篇 |
1996年 | 40篇 |
1995年 | 30篇 |
1994年 | 36篇 |
1993年 | 26篇 |
1992年 | 33篇 |
1991年 | 31篇 |
1990年 | 25篇 |
1989年 | 17篇 |
1988年 | 21篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 19篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1246条查询结果,搜索用时 31 毫秒
171.
Gennari L Felletti M Blasa M Angelino D Celeghini C Corallini A Ninfali P 《Phytochemical analysis : PCA》2011,22(3):272-279
Introduction – Beta vulgaris var. cicla (BV) leaves contain chemopreventive compounds that have been investigated for new drug discovery. These compounds belong to the family of the apigenin‐glycosides. Since the leaves are seasonal products containing high percentages of water, they are easily degradable during storage in fresh conditions. To be stored they require a drying process, consuming time and a large amount of energy. The extraction of apigenin‐glycosides may also be conveniently performed from BV seeds, which represent a stable and year‐long available biomass. Objectives – The present report was undertaken to find a strategy of purification of bioactive flavonoids from BV seeds and test their ability to inhibit proliferation both on human colon cancer (RKO) cells and normal human fibroblasts (HF). Materials and methods – The ethyl‐acetate extract of BV seeds was fractionated on a Sephadex LH 20 column. A fraction of this extract, labeled as P4, exploited a marked antiproliferative activity on RKO cells. The components of P4 were purified on an RP18 column chromatography and identified by HPLC‐ESI‐MS as 2,4,5‐trihydroxybenzaldehyde, 2,5‐dihydroxybenzaldehyde, vanillic acid, xylosylvitexin, glucopyranosyl‐glucopyrasyl‐rhamnetin and glucopyranosyl‐xylosyl‐rhamnetin. All of them were tested for cytostatic and cytotoxic activity on RKO and HF cells. Results – Xylosylvitexin exhibited the strongest antiproliferative activity on RKO cells, together with an enhancement of the apoptosis, an increase of cells in the G1 phase and a reduction of cells in the S phase; on the contrary, the proliferation of HF was significantly stimulated. Conclusion – Xylosylvitexin is the main and more efficient chemopreventive compound in BV seeds, but the natural cocktail of molecules, represented by P4 fraction, showed a better compromise between the antiproliferative activity on RKO cells and the enhancement of HF proliferation. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
172.
Uta Maier-Maercker 《Journal of plant physiology》1984,115(5):405-418
173.
Muhammad Azhar Nadeem Ephrem Habyarimana Tolga Karaky Faheem Shehzad Baloch 《Physiology and Molecular Biology of Plants》2021,27(7):1609
Common bean is a nutrient‐dense legume crop serving as a source of food for millions of people. Characterization of unexplored common bean germplasm to unlock the phenotypic and genetic variations is still needed to explore the breeding potential of this crop. The current study aimed to dissect the genetic basis having association for days to flowering (DF). A total of 188 common bean accessions collected from 19 provinces of Turkey were used as plant material under five environments and two locations. Analysis of variance (ANOVA) revealed that genotypes and genotype by environment interaction have significant effects on DF. A total of 10 most stable accessions were evaluated from stability analysis. Overall maximum (75) and minimum (54) DF were observed for Hakkari-51 and Mus-46 accessions, respectively. The implemented constellation plot divided studied germplasm according to their DF and growth habit. A total of 7900 DArTseq markers were used for association analysis. Mixed linear model using the Q + K Model resulted a total of 18 DArTseq markers from five environments. DArT-8668385 marker identified in Bolu during 2016 was also associated with DF in Sivas during 2017. Combined data of five years resulted a total of four markers (DArT-22346534, DArT-3369768, DArT-3374613, and DArT-3370801) having significant association ( p < 0.01 ) for DF. DArT-22346534 present on Pv 08 accounted a maximum of 9.89% variation to the studied trait. A total of four putative candidate genes were predicted from sequences reflecting homology to identified four DArTseq markers. We envisage that exploitation of identified DArTseq markers will hopefully beneficial for the development of new common bean varieties having better adaptation ability to changing climatic conditions.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-021-01029-8. 相似文献
174.
Alim Dewan Jihye Kim Rebecca H. McLean Siva A. Vanapalli Muhammad Nazmul Karim 《Biotechnology and bioengineering》2012,109(12):2987-2996
We investigated growth kinetics of microalgae, Chlorella vulgaris, in immobilized arrays of nanoliter‐scale microfluidic drops. These static drop arrays enabled simultaneous monitoring of growth of single as well as multiple cells encapsulated in individual droplets. To monitor the growth, individual drop volumes were kept nearly intact for more than a month by controlling the permeation of water in and out of the microfluidic device. The kinetic growth parameters were quantified by counting the increase in the number of cells in each drop over time. In addition to determining the kinetic parameters, the cell‐size distribution of the microalgae was correlated with different stages of the growth. The single‐cell growth kinetics of C. vulgaris showed significant heterogeneity. The specific growth rate ranged from 0.55 to 1.52 day?1 for different single cells grown in the same microfluidic device. In comparison, the specific growth rate in bulk‐scale experiment was 1.12 day?1. It was found that the average cell size changes significantly at different stages of the cell growth. The mean cell‐size increased from 5.99 ± 1.08 to 7.33 ± 1.3 µm from exponential to stationary growth phase. In particular, when multiple cells are grown in individual drops, we find that in the stationary growth phase, the cell size increases with the age of cell suggesting enhanced accumulation of fatty acids in older cells. Biotechnol. Bioeng. 2012; 109: 2987–2996. © 2012 Wiley Periodicals, Inc. 相似文献
175.
L. K. Ignatova N. S. Novichkova V. A. Mudrik V. Yu. Lyubimov B. N. Ivanov A. K. Romanova 《Russian Journal of Plant Physiology》2005,52(2):158-164
The effects of CO2 concentration (C
a) on growth, photosynthesis, and the activity of enzymes associated with the translocation and assimilation of CO2 were studied in sugar beet (Beta vulgaris L. subsp. saccharifera, cv. Ramonskaya) plants. The plants were grown in controlled-climate chamber to the stage of 3–4 leaves and then used in experiments. Experimental plants were exposed in boxes to doubled C
a (700 µl/l, 2C plants), whereas control plants were kept in a chamber with ambient atmosphere (350 µl/l, 1C plants). As compared with 1C plants, in 3 and 8 days, the leaf area of 2C plants increased by 14 and 26%, respectively. The rate of their photosynthesis (P
n) measured in 3, 6, and 8 days increased by 85, 47, and 52%, respectively, whereas in normal air, the values of P
n in 2C plants were by 12, 19, and 15% lower than in 1C plants. After 8-day growth, the content of soluble carbohydrates in the leaves of 2C plants attained 7.2%, being by 80% greater than in 1C plants; the content of starch did not exceed 3%. The total content of chlorophylls a and b in the leaves of 2C plants was by 14% greater than in 1C plants, but their ratio was essentially the same. The level of protein in 2C plants was by 13.4% lower than in 1C plants. The activity and content of Rubisco in 1C and 2C plants were similar. As compared with 1C plants, in 2C plants the activity of soluble carbonic anhydrase (sCA) was lower by 34% in 3 days and by 18% in 8 days; the activity of carbonic anhydrase of membrane preparations (mCA), was lower by 24 and 77%, respectively. Catalase activity in 2C plants became by 8% lower than in 1C plants only after 8 days. A reduction in the photosynthetic ability of 2C plants in ambient atmosphere, a decrease in activity of sCA and, especially, of mCA observed together with invariable activity and content of Rubisco in the leaf extracts are interpreted as early symptoms of acclimation of young plants of sugar beet to elevated CO2.Translated from Fiziologiya Rastenii, Vol. 52, No. 2, 2005, pp. 184–190.Original Russian Text Copyright © 2005 by Ignatova, Novichkova, Mudrik, Lyubimov, Ivanov, Romanova.This revised version was published online in April 2005 with a corrected cover date. 相似文献
176.
While studying the behavior of profilin from Phaseolus vulgaris seeds under native conditions, a high molecular weight species suggesting a complex of profilin and associated proteins was observed by Western immunoblotting. This putative complex was also observed when enzyme-linked secondary antibodies alone were used, and this apparently resulted from antibody association, through its glycosyl moieties, with the endogenous carbohydrate-binding activity from the seed extracts. This endogenous activity corresponded to that of purified phytohemagglutinin (PHA). In addition, the P. vulgaris lectin activity was very stable and was observed when the extracts were pretreated with varying concentrations of sodium dodecyl sulfate, Triton X-100, urea and β-mercaptoethanol, or when membrane blots were boiled in water before incubation with antibody. The activity was abolished only if the membrane was boiled in 1% sodium dodecyl sulfate. This finding could also be useful to implement assays for carbohydrate-binding activity from cell or tissue extracts using different visualizable reagents bearing particular glycosyl moieties. 相似文献
177.
Felix Lenk Mathias Vogel Thomas Bley Juliane Steingroewer 《Engineering in Life Science》2012,12(6):588-594
This study focuses on the morphological development and secondary metabolite production of the red pigments from the group of betacyanins in hairy roots of Beta vulgaris. We demonstrate a working, medium throughput, customized, automatic image recognition solution for hairy roots on agar plates including the evaluation of 12 experimental samples. Image acquisition is conducted under comparable para‐meters using a tripod with light emitting diode background lighting and a digital single lens reflex camera. The server‐based image recognition system developed together with Wimasis GmbH, Munich, Germany helps to obtain not only quantitative values for morphological parameters, such as segment lengths and widths or metabolite concentrations, but also global parameters of root growth, such as total root length or the number of branching points. Using timed diagrams the development of the total root length, the total number of branching points, and the mean pigment concentration during the cultivation period were determined. The generated data present the basis for detailed mathematical modeling in order to achieve a structured growth model for hairy roots. A mathematical model for growth of hairy roots can be used to decrease experimental efforts as well as to optimize cultivation conditions and the bioreactor design. 相似文献
178.
179.
180.
目的:研究细胞角蛋白K14、K19在寻常型银屑病(PV)发病中的作用机制。方法:选择从2012年1月到2016年12月在西安交通大学第二附属医院皮肤科就诊的PV患者60例纳入本次研究。将PV患者在皮损区及未受累皮肤区分别取1份皮肤,制成存档蜡块,分别记为PV皮损组和PV未受累皮肤组各60例。另选同期在我院接受外伤手术治疗的健康皮肤60例作为对照组,分析K14、K19在PV中的阳性表达率以及表达水平,分析K14及K19在PV皮损区阳性表达的相关性。结果:各组的K14及K19阳性表达率以及表达水平比较差异有统计学意义(P0.05)。PV皮损组和PV未受累皮肤组的K14阳性表达率及表达水平明显高于对照组,K19阳性表达率及表达水平明显低于对照组,差异有统计学意义(P0.05)。PV皮损组的K14阳性表达率及表达水平明显高于PV未受累皮肤组,K19阳性表达率及表达水平明显低于PV未受累皮肤组,差异有统计学意义(P0.05)。根据Spearman法分析相关性发现,K14及K19在PV皮损区阳性表达中呈负相关(r=-0.871,P=0.000)。结论:K14及K19均在PV发病过程中出现异常表达,其中K14阳性表达较强,而K19阳性表达较弱,二者在PV皮损区阳性表达中呈负相关。临床上可考虑监测K14及K19的阳性表达水平,从而更好地辅助临床诊断及病情的预估,值得临床医师关注与重视。 相似文献