全文获取类型
收费全文 | 79907篇 |
免费 | 4285篇 |
国内免费 | 93篇 |
专业分类
林业 | 3265篇 |
农学 | 2105篇 |
基础科学 | 461篇 |
8786篇 | |
综合类 | 15437篇 |
农作物 | 3167篇 |
水产渔业 | 3579篇 |
畜牧兽医 | 42130篇 |
园艺 | 850篇 |
植物保护 | 4505篇 |
出版年
2019年 | 731篇 |
2018年 | 1113篇 |
2017年 | 1240篇 |
2016年 | 1078篇 |
2015年 | 935篇 |
2014年 | 1220篇 |
2013年 | 2732篇 |
2012年 | 2164篇 |
2011年 | 2639篇 |
2010年 | 1639篇 |
2009年 | 1751篇 |
2008年 | 2653篇 |
2007年 | 2483篇 |
2006年 | 2350篇 |
2005年 | 2203篇 |
2004年 | 2119篇 |
2003年 | 2173篇 |
2002年 | 1965篇 |
2001年 | 2428篇 |
2000年 | 2469篇 |
1999年 | 1897篇 |
1998年 | 738篇 |
1997年 | 716篇 |
1996年 | 721篇 |
1995年 | 811篇 |
1993年 | 746篇 |
1992年 | 1565篇 |
1991年 | 1760篇 |
1990年 | 1642篇 |
1989年 | 1658篇 |
1988年 | 1481篇 |
1987年 | 1538篇 |
1986年 | 1602篇 |
1985年 | 1551篇 |
1984年 | 1186篇 |
1983年 | 1060篇 |
1982年 | 705篇 |
1979年 | 1154篇 |
1978年 | 897篇 |
1977年 | 759篇 |
1975年 | 779篇 |
1974年 | 1026篇 |
1973年 | 1026篇 |
1972年 | 1045篇 |
1971年 | 995篇 |
1970年 | 988篇 |
1969年 | 907篇 |
1968年 | 813篇 |
1967年 | 802篇 |
1966年 | 732篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Alexander N. Shikov Ekaterina D. Obluchinskaya Elena V. Flisyuk Inna I. Terninko Yulia E. Generalova Olga N. Pozharitskaya 《Marine drugs》2022,20(5)
In recent years, natural deep eutectic solvents (NADES) have been widely investigated for the extraction of food and medicinal plants as well as seaweeds. However, the ability of NADES for trace elements co-extraction from natural sources is not well investigated. The aim of this study was to investigate the ability of common NADES for trace elements co-extraction from Fucus vesiculosus. All of the tested NADES did not recover As and Co (concentration <LOQ). Moreover, all of the tested NADES provided a low recovery (<9%) of Ba, Ca, Fe, Mg, Mn, Sr, and Zn. The method of extraction had not shown a statistically significant effect on the co-extraction of all elements (excluding Ba and Ca). In contrast, the water content in NADES was significantly affected on the recovery of Ba, Ca, Mg, Mn, Sr, and Zn. The recovery of Al and Cr was relatively high and considerably varied (from 1.5 to 59.9%). NADES comprising lactic acid:glucose:H2O (5:3:1) provided the lowest contents of all elements, and the highest extracted amounts were obtained employing water contents of 60–80%. The calculated daily intake of all the elements contained in NADES extracts were less than the daily dose risk estimators. The hazard quotients, hazard indexes, and carcinogenic risk calculated for all trace elements and their combination were considerably less than 1. This evidences no health risk, and carcinogenic risk after topical application of all studied NADES. For the first time, the results of the current study demonstrated that NADES extracts of F. vesiculosus contain a lower amount of trace metals and are safer than the extracts obtained with water and 70% acetone. This indicates a significant advantage for NADES compared with the other solvents. 相似文献
93.
Ken R. Ito Tomonori Sato Hiro Goto Katsuyoshi Sato Jun Watanabe Masaki Yokoo 《The Journal of Poultry Science》2022,59(3):247
Increasing food loss and waste (FLW) is a global problem, and efforts are being made to use waste food as potential livestock feed material. The amount of self-supplied feed is lower in Japan than in other countries, and the government recommends FLW use for animal feed. Sake (Japanese rice wine) is a traditional alcoholic beverage. During the sake manufacturing process, large amounts of squeezed solids or “lees” (sake lees) are generated. Sake lees are nutritious and functional, but are prone to spoilage. In this study, we investigated whether sake lees should be mixed with animal feed immediately or after drying. To assess the usefulness of sake lees as a poultry feed ingredient and determine the effect of sake lees on intestinal immunity, we performed a feeding trial with three treatments: a raw sake lees (RSL) diet, dried sake lees (DSL) diet, and control diet. Three-week-old broilers were fed these diets (n=8 per group) for two weeks. We then calculated feed efficiency and performed RT-qPCR to assess the effects of diet on intestinal immunity. The growth performance in the RSL diet group was equivalent to that in the control diet group. The DSL diet became difficult for broilers to eat, resulting in decreased growth performance. In the ileum of RSL-diet broilers, the mRNA expression levels of TGF-β1 and avian β-defensin (AvBD)12 were significantly increased compared to those of control diet broilers (p<0.05), and a significant correlation was observed between the two genes (p<0.05). Our results indicated that sake lees should not be dried and should be mixed immediately with feed, and this sake lees when fed to chicken activates the intestinal immunity. However, sake lees have a lower fat content than corn, and it is thus important to combine sake lees with high-energy feed. 相似文献
94.
95.
C.E. Epifanio 《Aquaculture (Amsterdam, Netherlands)》1979,16(3):187-192
Four species of bivalve molluscs were fed diets consisting of varying proportions of the yeast Candida utilis and the diatom Thalassiosira pseudonana. Juvenile Argopecten irradians, Mercenaria mercenaria, and Mytilus edulis grew as fast or faster than controls when fed diets containing as much as 50% yeast. Growth of soft tissue in Crassostrea virginica, however, decreased with the amount of yeast in the diet. The relative food values of the different diets were not closely correlated with gross chemical composition or amino acid composition. 相似文献
96.
A proton magnetic resonance spectroscopic method for determining disulfiram in the bulk drug product and in the formulated material was collaboratively studied. The method depends on the use of chloroform-d as a solvent and hexamethylcyclotrisiloxane as the internal standard. No interference from tablet excipients was observed. The method is rapid and specific. Eighteen laboratories analyzed duplicate samples of a bulk drug product, a 250 mg tablet composite, and a 500 mg tablet composite. The average per cent results and standard deviations were 99.7 +/- 1.4, 100.9 +/- 2.0, and 99.9 +/- 2.2, respectively. 相似文献
97.
98.
E J de Vries J Zeeman R J Esser B Borsje F J Mulder 《Journal of the Association of Official Analytical Chemists》1979,62(6):1285-1291
Vitamin D is determined in preparations containing other fat-soluble vitamins by high performance liquid chromatography (HPLC). The unsaponifiable residue is extracted and separated from interferences by reverse phase chromatography; the fraction corresponding to vitamin D3 is collected and quantitated using normal phase chromatography (amylalcohol-n-hexane as mobile phase) by measuring the vitamin D3 and pre-vitamin D3 peaks at 254 nm. Previtamin D3 content is calculated as vitamin D3 with a conversion factor (determined on the equipment used). Application of the method to vitamin AD3 mixtures in oils gives 98-102% recovery. The reproducibility, using an external standard, is 2-3%, calculated as the coefficient of variation; with an internal standard, the coefficient of variation is 1-1.5%. The method measures potential vitamin D3 content in preparations containing greater than or equal to 200 IU/g in the presence of all known vitamin D3 isomers, vitamin A, and vitamin E. 相似文献
99.
100.