全文获取类型
收费全文 | 135篇 |
免费 | 17篇 |
国内免费 | 9篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 10篇 |
2010年 | 1篇 |
2009年 | 9篇 |
2008年 | 11篇 |
2007年 | 9篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1997年 | 4篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有161条查询结果,搜索用时 78 毫秒
71.
重液浮选对花粉浓度计算的影响 总被引:2,自引:0,他引:2
用重液浮选方法可获得富集、清洁的孢粉制片,但在浮选过程中不可避免地会在丢弃的底样中留下相当数量的孢粉。本文定量地探讨这些残留孢粉在重液不同比重条件下对花粉浓度计算的影响,结果表明,在重液浮选中,不同类型孢粉的漂浮率有所不同,并因此造成浓度计算中的误差,误差的大小因孢粉类型和重液比重的不同而不同,大体在1—15%之间。 相似文献
72.
Q. R. Islam 《Hydrobiologia》1996,340(1-3):317-321
Aponogeton undulatus Roxb. grows in abundance throughout the deeply flooded land in the Northeast Region of Bangladesh. The plant has the ability to elongate and tolerate submergence after deep flooding. The elongation ability is expressed chiefly by the elongation of petiole. The rootstock of the plant is an important food item for the low-income people in this deeply flooded area. Rice is the main crop in this area providing the major source of energy and protein. However, the crop is often damaged by floods. The nutrient composition of rootstock of Aponogetan undulatus Roxb. shows that it can provide an adequate supply of carbohydrate, protein and some minerals. This food can be exceptionally useful as a nutrient supplement in many areas where purchasing power is limited because of low incomes. Four species of Aponogeton are found in Bangladesh. The aquatic environment prevailing in the deeply flooded area in Bangladesh has great potential in terms of propagation of these species. If this potential can be realized it would improve the nutrition of the people and maintain biodiversity and traditional ecosystems. Further study on the chemical composition of rootstock, and ecological, morphological and physiological characteristics of all the Aponogeton species would be of great value. 相似文献
73.
74.
Praveen Sher Ganesh Ingavle Surendra Ponrathnam Pankaj Poddar Atmaram P. Pawar 《AAPS PharmSciTech》2009,10(2):547-558
The purpose of this research work was to explore an application of uncoated porous drug carrier prepared by single-step drug
adsorption for a delivery system based on integration of floating and pulsatile principles intended for chronotherapy. This
objective was achieved by utilizing 32 factorial design, solvent volume (X
1) and drug amount (X
2) as selected variables, for drug adsorption using solvents, methanol, and dichloromethane (DCM), of varying polarity. Nitrogen
adsorption (N2), scanning electron microscopy of cross-sections, and atomic force microscopy were done to study adsorption patterns and
their effect on release pattern. Drug release study was customized by performing for 6 h in acidic environment to mimic gastroretention
followed by basic environment akin to transit phase. Correlation between porous data from mercury and N2 adsorption was probably studied for the first time. Observed regression analysis values for pore volume, surface area, and
drug release indicated the influence of selected variables. Total release range in acidic medium was 12.77–24.57% for methanol,
8.79–15.26% for DCM, and final release of 69.45–92.23% for methanol, and 60.16–99.99% for DCM influenced by varying internal
geometries was observed. Present form of drug delivery system devoid of any additives/excipients influencing drug release
shows distinct behavior from other approaches/technologies in chronotherapy by (a) observing desired low drug release (8%)
in acidic medium, (b) overcoming the limitations of process variables caused by multiple formulation steps and different characteristic
polymers, (c) reducing time consumption due to single step process, and (d) extending as controlled/extended release. 相似文献
75.
A novel gastro retentive controlled release drug delivery system of verapamil HCl was formulated in an effort to increase
the gastric retention time of the dosage form and to control drug release. Hydroxypropylmethylcellulose (HPMC), carbopol,
and xanthan gum were incorporated for gel-forming properties. Buoyancy was achieved by adding an effervescent mixture of sodium
bicarbonate and anhydrous citric acid. In vitro drug release studies were performed, and drug release kinetics was evaluated using the linear regression method. The optimized
intragastric floating tablet composed of 3:2 of HPMC K4M to xanthan gum exhibited 95.39% drug release in 24 h in vitro, while the buoyancy lag time was 36.2 s, and the intragastric floating tablet remained buoyant for >24 h. Zero-order and
non-Fickian release transport was confirmed as the drug release mechanism from the optimized formulation (F7). X-ray studies
showed that total buoyancy time was able to delay the gastric emptying of verapamil HCl intragastric floating tablet in mongrel
dogs for more than 4 h. Optimized intragastric floating tablet showed no significant change in physical appearance, drug content,
total buoyancy time, or in vitro dissolution pattern after storage at 40°C/75% relative humidity for 3 months. 相似文献
76.
This investigation describes the development of an intragastric drug-delivery system for cefuroxime axetil. The 32 full factorial design was employed to evaluate contribution of hydroxypropyl methyl cellulose (HPMC) K4M/HPMC K100 LV ratio
(polymer blend) and sodium lauryl sulfate (SLS) on drug release from HPMC matrices. Tablets were prepared using direct compression
technique. Formulations were evaluated for in vitro buoyancy and drug release study using United States Pharmacopeia (USP) 24 paddletype dissolution apparatus using 0.1N HCl as a dissolution medium. Multiple regression analysis was performed for
factorial design batches to evaluate the response. All formulations had floating lag times below 2 minutes and constantly
floated on dissolution medium for more than 8 hours. It was found that polymer blend and SLS significantly affect the time
required for 50% of drug release, percentage drug release at 12 hours, release rate constant, and diffusion exponent (P<.05). Also linear relationships were obtained between the amount of HPMC K100 LV and diffusion exponent as well as release
rate constant. Kinetic treatment to dissolution profiles revealed drug release ranges from anomalous transport to case 1 transport,
which was mainly dependent on both the independent variables.
Published: February 24, 2006 相似文献
77.
Eva Rothäusler Iván Gómez Iván A. Hinojosa Ulf Karsten Fadia Tala Martin Thiel 《Journal of phycology》2009,45(3):547-559
Macroalgal rafts frequently occur floating in coastal waters of temperate regions of the world’s oceans. These rafts are considered important dispersal vehicles for associated organisms with direct development. However, environmental factors may limit the floating potential of kelp and thereby the dispersal of associated organisms. To examine the effect of water temperature and grazing on growth, reproductive output, and survival of floating Macrocystis spp., experiments were conducted in outdoor tanks during austral summer 2006/2007 at three sites along the Chilean Pacific coast (20° S, 30° S, 40° S). At each site, Macrocystis spp. was maintained individually at three different water temperatures (ambient, ambient − 4°C, ambient + 4°C) and in the presence or absence of the amphipod grazer Peramphithoe femorata for 14 d. High water temperatures (>20°C) provoked rapid degradation of Macrocystis spp. rafts. At moderate temperatures (15°C–20°C), algal survival depended on the presence of associated grazers. In the absence of grazers, algal rafts gained in biomass while grazing caused considerable losses of algal biomass. Algal survival was the highest under cooler conditions (<15°C), where raft degradation was slow and grazer-induced biomass losses were compensated by continuing algal growth. Our results indicate that floating kelp rafts can survive for long time periods at the sea surface, but survival depends on the interaction between temperature and grazing. We suggest that these processes limiting the survival of kelp rafts in warmer temperatures may act as a dispersal barrier for kelp and its associated passengers. 相似文献
78.
《Journal of enzyme inhibition and medicinal chemistry》2013,28(5):809-815
AbstractThe aim of this study is to propose an improved computational methodology, which is called Compressed Images for Affinity Prediction-2 (CIFAP-2) to predict binding affinities of structurally related protein–ligand complexes. CIFAP-2 method is established based on a protein–ligand model from which computational affinity information is obtained by utilizing 2D electrostatic potential images determined for the binding site of protein–ligand complexes. The quality of the prediction of the CIFAP-2 algorithm was tested using partial least squares regression (PLSR) as well as support vector regression (SVR) and adaptive neuro-fuzzy ?nference system (ANFIS), which are highly promising prediction methods in drug design. CIFAP-2 was applied on a protein–ligand complex system involving Caspase 3 (CASP3) and its 35 inhibitors possessing a common isatin sulfonamide pharmacophore. As a result, PLSR affinity prediction for the CASP3–ligand complexes gave rise to the most consistent information with reported empirical binding affinities (pIC50) of the CASP3 inhibitors. 相似文献
79.
Iván Gómez Iván A. Hinojosa Ulf Karsten Fadia Tala Martin Thiel 《Journal of phycology》2011,47(2):269-281
Rafts of Macrocystis pyrifera (L.) C. Agardh can act as an important dispersal vehicle for a multitude of organisms, but this mechanism requires prolonged persistence of floating kelps at the sea surface. When detached, kelps become transferred into higher temperature and irradiance regimes at the sea surface, which may negatively affect kelp physiology and thus their ability to persist for long periods after detachment. To examine the effect of water temperature and herbivory on the photosynthetic performance, pigment composition, carbonic anhydrase (CA) activity, and the nitrogen (N) and carbon (C) content of floating M. pyrifera, experiments were conducted at three sites (20° S, 30° S, 40° S) along the Chilean Pacific coast. Sporophytes of M. pyrifera were maintained at three different temperatures (ambient, ambient ? 4°C, ambient + 4°C) and in presence or absence of the amphipod Peramphithoe femorata for 14 d. CA activity decreased at 20° S and 30° S, where water temperatures and irradiances were highest. At both sites, pigment contents were substantially lower in the experimental algae than in the initial algae, an effect that was enhanced by grazers. Floating kelps at 20° S could not withstand water temperatures >24°C and sank at day 5 of experimentation. Maximal quantum yield decreased at 20° S and 30° S but remained high at 40° S. It is concluded that environmental stress is low for kelps floating under moderate temperature and irradiance conditions (i.e., at 40° S), ensuring their physiological integrity at the sea surface and, consequently, a high dispersal potential for associated biota. 相似文献
80.