全文获取类型
收费全文 | 568篇 |
免费 | 38篇 |
专业分类
林业 | 37篇 |
农学 | 14篇 |
163篇 | |
综合类 | 32篇 |
农作物 | 46篇 |
水产渔业 | 53篇 |
畜牧兽医 | 229篇 |
园艺 | 7篇 |
植物保护 | 25篇 |
出版年
2023年 | 12篇 |
2022年 | 22篇 |
2021年 | 33篇 |
2020年 | 25篇 |
2019年 | 38篇 |
2018年 | 25篇 |
2017年 | 25篇 |
2016年 | 21篇 |
2015年 | 16篇 |
2014年 | 29篇 |
2013年 | 27篇 |
2012年 | 42篇 |
2011年 | 29篇 |
2010年 | 10篇 |
2009年 | 19篇 |
2008年 | 24篇 |
2007年 | 24篇 |
2006年 | 16篇 |
2005年 | 8篇 |
2004年 | 19篇 |
2003年 | 18篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1992年 | 2篇 |
1991年 | 10篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有606条查询结果,搜索用时 31 毫秒
41.
Endotoxin-stimulated opioid peptide secretion: two secretory pools and feedback control in vivo 总被引:3,自引:0,他引:3
D B Carr R Bergland A Hamilton H Blume N Kasting M Arnold J B Martin M Rosenblatt 《Science (New York, N.Y.)》1982,217(4562):845-848
Small doses of endotoxin evoked a dramatic biphasic response of opioid peptide secretion into blood in sheep. The first phase began within minutes and coincided with a brief hypertensive response to endotoxin well before the appearance of fever or hypotension. The ratio of beta-endorphin to beta-lipotropin fell abruptly at the onset of the second phase of release, suggesting early depletion of a pool rich in beta-endorphin and subsequent emergence of a pool rich in unprocessed precursor. The concentration of cerebrospinal fluid opioids increased tenfold during the second phase. Naloxone administration augmented endotoxin-induced opioid secretion in both early and late phases, suggesting a short-loop feedback regulation of stress-induced endorphin secretion. 相似文献
42.
Fritz DM Reis DA Adams B Akre RA Arthur J Blome C Bucksbaum PH Cavalieri AL Engemann S Fahy S Falcone RW Fuoss PH Gaffney KJ George MJ Hajdu J Hertlein MP Hillyard PB Horn-von Hoegen M Kammler M Kaspar J Kienberger R Krejcik P Lee SH Lindenberg AM McFarland B Meyer D Montagne T Murray ED Nelson AJ Nicoul M Pahl R Rudati J Schlarb H Siddons DP Sokolowski-Tinten K Tschentscher T von der Linde D Hastings JB 《Science (New York, N.Y.)》2007,315(5812):633-636
Intense femtosecond laser excitation can produce transient states of matter that would otherwise be inaccessible to laboratory investigation. At high excitation densities, the interatomic forces that bind solids and determine many of their properties can be substantially altered. Here, we present the detailed mapping of the carrier density-dependent interatomic potential of bismuth approaching a solid-solid phase transition. Our experiments combine stroboscopic techniques that use a high-brightness linear electron accelerator-based x-ray source with pulse-by-pulse timing reconstruction for femtosecond resolution, allowing quantitative characterization of the interatomic potential energy surface of the highly excited solid. 相似文献
43.
44.
Marion A. Sonnleitner Madeleine S. Günthardt-Goerg Inga K. Bucher-Wallin Werner Attinger Sybille Reis Rainer Schulin 《Water, air, and soil pollution》2001,126(3-4):271-290
Sixteen open-top chambers, each equipped with two non-weighablegravity-drained lysimeter compartments, were used to investigate the impacts of elevated atmospheric carbon dioxide (CO2) concentration and nitrogen (N) deposition on the water relations and growth of young model forest ecosystems on two different types of soils. The same vegetation of a mixed spruce and beech overstorey and various herbs in the understorey was planted in all treatments on both soils. The soils were repacked on top of a drainage layer. Four combinations of treatments were applied in four replicates each: ambient (370 cm3 m-3) CO2 + low (7 kg N ha-1 a-1) N deposition, ambient CO2 + high(70 kg N ha-1 a-1) N deposition, elevated (590 cm3 m-3) CO2 + low N deposition, and elevated CO2 + high N deposition. After canopy closure, treatment effects on evapotranspiration and growth during the third year of study were very different for the two soils.On the acidic sandy loam, elevated CO2 enhanced growth(leaf biomass +21%, roots +27%) at reduced evapotranspiration (–9%). High N deposition increased aboveground growth even more strongly (+50%), but also increased evapotranspiration (+16%). Together, elevated CO2 and high N had a more than additive fertilizer effect on growth, while their effects on evapotranspirationcompensated. On the calcareous loamy sand, elevated CO2not only tended to enhance growth (leaf biomass +17%, roots +20%), but also increased evapotranspiration (+5%).On this soil, aboveground growth was stimulated by N only incombination with elevated CO2, but less than on the acidic soil, while evapotranspiration (–6.5%) and root growth into the subsoil (–54%) were decreased by increased N deposition at both CO2 concentrations, in contrast to the N treatments on the acidic sandy loam. The influence of the soil on the observed ecosystem responses canbe interpreted in terms of the concept of optimal resource allocation. 相似文献
45.
H.-P. Blume 《植物养料与土壤学杂志》1995,158(3):307-308
46.
47.
Conception soil maps for urban areas The demand for soil maps increased strongly during the last years. This concerns urban soils, too. Conception soil maps constructed from a lot of basic informations (basic maps and point data) are the alternative to traditional soil mapping, which is expensive in time and money for urban areas. Further informations are to evaluate maps from these conception soil maps. Using graphic information-systems is advantageous for construction and evaluation. 相似文献
48.
49.
50.
Luis Alvarez-Lajonchegre Vinicius R. Cerqueira Israel D. Silva Jaqueline Araujo Marcosdos Reis 《Journal of the World Aquaculture Society》2002,33(4):506-516
A pilot‐scale trial to rear fat snook Centropomus parallelus through larval, weaning and nursery phases was conducted in Florianópolis, Brazil. Eggs (96% fertilization) from captive broodstock, induced to spawn using 50 μg/kg LHRHa were stocked in two 4,000‐L cylindrical fiberglass tanks at a mean density of 19.2 eggs/L. Nannochloropsis oculata was stocked with the eggs and maintained at a mean density of 0.5–1.0 ± 106 cells/mL up to 31 dph (31 dph). Hatching averaged 90%. Larvae were fed rotifers Brachionus rotundiformis enriched with an oil emulsion from 3 dph to 36 dph (30–40 rotifers/mL) and Artermia meta‐nauplii enriched with Selco from 22 dph to 60 dph (mean 2.9 meta‐nauplii/mL). Weaning began at 45 dph with an artificial dry diet NRG (50% protein), supplied together with concentrated and enriched Artemia meta‐nauplii. No critical period of mortality was observed during larval rearing. During the 43 days of weaning and nursery, less than 1% mortality was recorded. Food conversion rate during nursery was 1.17, with a change in the coefficient of variation of mean total length of 1.3%. Specific total growth rate in weight was 13.0 %/d and mean growth in total length and total weight were 0.65 mm/d and 24.0 mg/d over the whole rearing trial respectively. Mean total length and total weight of juveniles were 57.6 ± 0.1 mm and 2.11 ± 0.12 g, respectively, and the length‐weight relationship was W = 8.29931 ± 10–5 TL3.049607 (r= 0.9986). on 88 dph when the trial was terminated. The condition factor on 88 dph was 1.104. On 88 dph a total of 35,000 juveniles were harvested, overall survival was 25.5% with mean final density of 4.4 fishn and biomass of 6.9 kg/m3. The present trial demonstrated the feasibility of mass production of fat snook. Possible improvements necessary for commercial cultivation of fat snook C. parallelus are discussed. 相似文献