全文获取类型
收费全文 | 281篇 |
免费 | 4篇 |
专业分类
林业 | 96篇 |
农学 | 4篇 |
91篇 | |
综合类 | 22篇 |
农作物 | 8篇 |
水产渔业 | 2篇 |
畜牧兽医 | 36篇 |
园艺 | 4篇 |
植物保护 | 22篇 |
出版年
2020年 | 3篇 |
2014年 | 3篇 |
2013年 | 15篇 |
2012年 | 11篇 |
2011年 | 14篇 |
2010年 | 3篇 |
2009年 | 9篇 |
2008年 | 15篇 |
2007年 | 13篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 10篇 |
2003年 | 13篇 |
2002年 | 8篇 |
2001年 | 3篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1981年 | 3篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1965年 | 2篇 |
1959年 | 3篇 |
1958年 | 2篇 |
1957年 | 2篇 |
1956年 | 2篇 |
1955年 | 2篇 |
1954年 | 2篇 |
1950年 | 2篇 |
1942年 | 2篇 |
1938年 | 8篇 |
1936年 | 6篇 |
1935年 | 4篇 |
1931年 | 5篇 |
1930年 | 6篇 |
1929年 | 5篇 |
1928年 | 5篇 |
1927年 | 5篇 |
1926年 | 10篇 |
1925年 | 4篇 |
1907年 | 2篇 |
1895年 | 4篇 |
排序方式: 共有285条查询结果,搜索用时 109 毫秒
11.
Sahab Hedjazi Othar Kordsachia Rudolf Patt Ahmad Jahan Latibari Ulrike Tschirner 《Industrial Crops and Products》2009,29(1):27-36
Alkaline sulfite–anthraquinone (AS/AQ) pulping of wheat straw and totally chlorine free (TCF) bleaching of resulting pulps was investigated. Wheat straw was supplied by the Ferdosii University Experimental Station in Northeastern Iran, cleaned and chopped into about 3–5 cm long pieces. In the AS/AQ pulping experiments, the active alkali charge on oven dry wheat straw, heating time to maximum cooking temperature, AQ dose and liquor to straw ratio were kept constant at 16%, 60 min, 0.1% and 4/1, respectively. The alkali ratio, Na2SO3/NaOH, calculated as NaOH, was varied from 20/80 to 80/20. Cooking time at maximum temperature was varied from 30 to 90 min and maximum cooking temperature was adjusted between 152 and 160 °C. Reference soda and soda/AQ pulps were produced.AS/AQ and soda/AQ pulps with kappa numbers below 15 were produced easily. Cooking of corresponding soda pulps under comparable conditions stopped at a kappa number of 25. The characteristics of unbleached AS/AQ, soda/AQ and soda pulps were compared. AS/AQ and soda/AQ pulps had similar tensile strength but tear was in favor to AS/AQ. The latter had much higher yield and brightness.TCF bleaching of AS/AQ pulp was performed in O Q (OP) or O Q (OP) P sequences. Oxygen delignification (O) resulted in a delignification degree of approximately one third. Followed by a chelating treatment (Q) and a subsequent (OP) stage under drastic conditions a brightness of 82.7% ISO was achieved in an O Q (OP) sequence. The sequence O Q (OP) P, with 2% H2O2 in the final P stage, improved brightness from 77.2% ISO after the OP stage to 83.6% ISO. Bleaching led to only small losses in tensile and burst strength but enhanced tear strength. Short beating in a Jokro mill was sufficient to attain good pulp strength. The results of this study indicate that AS/AQ pulping and TCF bleaching is a convincing alternative to produce high-quality pulp from wheat straw for writing and printing paper. 相似文献
12.
Rudolf Geiger 《Forstwissenschaftliches Centralblatt》1935,57(24):789-794
Ohne Zusammenfassung 相似文献
13.
Rudolf Geiger 《Forstwissenschaftliches Centralblatt》1927,49(19):665-675
Ohne Zusammenfassung 相似文献
14.
Rudolf Geiger 《Forstwissenschaftliches Centralblatt》1928,50(13):437-448
Ohne Zusammenfassung 相似文献
15.
Huber Bernhart M. postner Rudolf Mayer H. Mayer Ernst 《European Journal of Forest Research》1959,78(3-4):122-128
16.
17.
Jürg Andreas Stückelberger Hans Rudolf Heinimann Edouard Charles Burlet 《European Journal of Forest Research》2006,125(4):377-390
Cost estimation is probably the most decisive factor in the process of computer-aided, preliminary planning for low-volume road networks. However, the cost of construction is normally assumed to be route-independent for a specific project area, resulting in sub-optimal layouts. This is especially true for mountainous terrain and in areas with unstable subsoil. Here, we present a model for more accurately estimating spatial variability in road life-cycle costs, based on terrain surface properties as well as geological properties of the subsoil. This parametric model incorporates four structural components: embankment, retaining structures, pavement, and drainage and stream-crossing structures. It is linked to a geo-database that allows users to derive location-specific parameter values as input. In applying this model, we have demonstrated that variability in costs ranges widely for mountainous areas, with the most expensive construction being approximately five times greater there than on more favorable sites. This variability strongly affects the optimal layout of a road network. First, when location-specific slope gradients are considered, costs are reduced by about 17% from those calculated via currently available engineering practices; when both slope gradient and geotechnical formations are included, those costs are decreased by about 20%. Second, the length of the road network is increased by about 4% and 10% respectively, compared with current practices. 相似文献
18.
Huber Bernhart M. postner Rudolf Mayer H. Mayer und Ernst 《Forstwissenschaftliches Centralblatt》1959,78(3-4):122-128
Ohne Zusammenfassung 相似文献
19.
A preliminary trial of the sedation induced by intranasal administration of midazolam alone or in combination with dexmedetomidine and reversal by atipamezole for a short‐term immobilization in pigeons
下载免费PDF全文
![点击此处可从《Veterinary anaesthesia and analgesia》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Slavomir Hornak Tomas Liptak Valent Ledecky Rudolf Hromada Jan Bilek David Mazensky Vladimir Petrovic 《Veterinary anaesthesia and analgesia》2015,42(2):192-196
ObjectiveTo assess the sedative and immobilization effect of intranasal administration (INS) of midazolam (MID) without or with INS dexmedetomidine (DXM), and some physiological changes induced by the drugs. The ability of INS atipamezole to reverse the DXM component was also assessed.Study designProspective ‘blinded’ experimental study.AnimalsIn total, 15 pigeons.MethodsPigeons were sedated by INS MID alone at a dose of 5 mg kg−1 (group MID, n = 6) or in combination with INS DXM at a dose 80 μg kg−1 (group MID-DXM, n = 6). Measurements were made of heart rate (HR), respiratory rate (fR) and cloacal temperature (CT). The degree of sedation was assessed at 15 minutes prior to, immediately after, and at intervals until 100 minutes after drug administrations. Following MID-DXM, INS atipamezole (250 μg kg−1) was administered and the same indices measured 5 and 10 minutes later.ResultsMID had no effect on HR and fR, and although CT decreased, it remained within physiological range. MID-DXM caused significant falls in HR, fR and CT that persisted until the end of sedation. Atipamezole antagonized sedation and cardiorespiratory side effects of MID-DXM within 10 minutes of application. In addition, for MID compared to MID-DXM, the lowest sedation scores [10 (7–14) and 10.5 (5–14) versus 2 (1–4) and 2 (1–5)] were achieved in the 10th and 20th minute versus the 20th and 30th minute of the sedation, respectively.Conclusions and clinical relevanceMID alone, given INS had minimal side effects on vital functions but caused inadequate immobilization of pigeons for restraint in dorsal recumbency. MID-DXM caused an effective degree of immobilization from 20 to 30 minutes after administration, at which time birds tolerated postural changes without resistance. Atipamezole antagonized both side effects and sedation, but complete recovery had not occurred within 10 minutes after its application. 相似文献
20.
LoCascio RG Ninonuevo MR Freeman SL Sela DA Grimm R Lebrilla CB Mills DA German JB 《Journal of agricultural and food chemistry》2007,55(22):8914-8919
The molecular basis by which human breast milk supports the development of a protective intestinal microbiome in infants is unknown. After lactose and lipids, human milk oligosaccharides (HMOs) are quantitatively the third largest and most diverse component of breast milk. In this work, glycomic profiling of HMO consumption by bifidobacteria using Fourier transform ion cyclotron resonance mass spectrometry reveals that one species, Bifidobacterium longum biovar infantis ATCC 15697, an isolate from the infant gut, preferentially consumes small mass oligosaccharides, representing 63.9% of the total HMOs available. These HMOs were detected in human breast milk at the onset and constantly through the first month of lactation by use of high performance liquid chromatography-chip time-of-flight mass spectrometry. Further characterization revealed that strain ATCC 15697 possesses both fucosidase and sialidase activities not present in the other tested strains. This work provides evidence that these small mass HMOs are selectively metabolized by select bifidobacterial strains and represent a potential new class of bioactive molecules functioning as prebiotics to facilitate a protective gut colonization in breast-fed newborns. 相似文献