全文获取类型
收费全文 | 5714篇 |
免费 | 290篇 |
国内免费 | 624篇 |
专业分类
林业 | 730篇 |
农学 | 812篇 |
基础科学 | 398篇 |
826篇 | |
综合类 | 1693篇 |
农作物 | 372篇 |
水产渔业 | 236篇 |
畜牧兽医 | 1029篇 |
园艺 | 182篇 |
植物保护 | 350篇 |
出版年
2024年 | 35篇 |
2023年 | 87篇 |
2022年 | 235篇 |
2021年 | 288篇 |
2020年 | 216篇 |
2019年 | 229篇 |
2018年 | 159篇 |
2017年 | 220篇 |
2016年 | 209篇 |
2015年 | 242篇 |
2014年 | 259篇 |
2013年 | 311篇 |
2012年 | 358篇 |
2011年 | 358篇 |
2010年 | 355篇 |
2009年 | 310篇 |
2008年 | 252篇 |
2007年 | 311篇 |
2006年 | 301篇 |
2005年 | 230篇 |
2004年 | 137篇 |
2003年 | 119篇 |
2002年 | 158篇 |
2001年 | 136篇 |
2000年 | 131篇 |
1999年 | 127篇 |
1998年 | 110篇 |
1997年 | 96篇 |
1996年 | 99篇 |
1995年 | 91篇 |
1994年 | 82篇 |
1993年 | 77篇 |
1992年 | 64篇 |
1991年 | 78篇 |
1990年 | 41篇 |
1989年 | 34篇 |
1988年 | 28篇 |
1987年 | 13篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1963年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有6628条查询结果,搜索用时 15 毫秒
61.
62.
我国高等学校审计制度变迁分析 总被引:1,自引:0,他引:1
新制度经济学中的制度变迁理论对我国高等学校审计制度变迁具有重大理论指导价值。在回顾历史的基础上,对我国高校审计制度供求变化进行分析,挖掘影响我国高等学校审计制度变迁的成因,提出我国高等学校审计制度的变迁方式将是强制性制度变迁和诱致性制度变迁相结合。改变以往只对制度进行静态研究和比较研究的传统方式,以动态的视角对我国高等学校审计制度进行研究,以期能对现阶段我国的高校审计改革提供有益的借鉴。 相似文献
63.
64.
65.
高原鼠兔喜欢刈割茂密高寒草甸中高大植物而影响植物群落内的种间关系。采用方差比率法、χ2检验和Spearman秩相关分析相结合的方法,分析了高原鼠兔刈割行为对高山嵩草草甸植物群落种间关联的影响。结果表明:高原鼠兔刈割会促进植物群落的种间总体联结从不显著正关联变为显著负关联,降低植物群落稳定性,减少植物群落内正关联和正相关的种对数量,增加负关联、无关联和负相关的种对数量。而综合χ2检验结果、AC值和OI指数,洞口植物群落大部分种对的种间关联均不显著,种间联结程度不强。这表明χ2检验和Spearman秩相关分析能够评价小型草食动物对植物群落种间关联的影响,为全面解析高原鼠兔整体干扰驱动植物群落结构变化提供了基础信息。 相似文献
66.
Waterless live fish transportation is an alternative and promising transport strategy, which may reduce shipping costs, increase stocking density and improve survival of some species. Spotted sea bass is one of the most economically important marine fish in China. However, waterless transportation has not yet been studied on spotted sea bass. To explore the possibility of waterless transportation of spotted sea bass and its sublethal stress responses, the survival rate and dynamics of blood biochemical parameters were evaluated in the present study by preserving it under no water, less water and water (control) conditions for 9 hr. The serum biochemical parameters including total protein, cortisol, glucose, lactate, alanine aminotransferase (ALT), aspartate aminotransferase (AST), total carbon dioxide (TCO2), creatinine, blood urea nitrogen (BUN), ammonia, superoxide dismutase (SOD) activity and malonaldehyde (MDA) were investigated. Results showed that the survival rates of fish in all groups gradually declined with time increasing. At the end of transportation, the survival rates in the control group, less‐water group and no‐water group decreased to 49.11%, 15.60% and 23.96% respectively. Significant changes were observed in several selected serum biochemical parameters, including glucose, lactate, ALT, TCO2, BUN and ammonia during simulated waterless transportation, which might negatively affect the physiological homeostasis of fish, leading to the high mortality in present study. In general, waterless transportation of spotted sea bass was possible, but it might be rather suitable for short time than long time. 相似文献
67.
Apparent digestibility coefficients of animal and plant feed ingredients for juvenile Pseudobagrus ussuriensis 下载免费PDF全文
A study was conducted to determine apparent digestibility coefficients (ADCs) of dry matter (DM), crude protein (CP), lipid, gross energy, phosphorus and amino acids (AAs) from Peruvian fish meal (PFM), native fish meal (NFM), meat bone meal (MBM), dried daphnia meal (DDM), soybean meal (SBM), full‐fat soybean (FSBM), cottonseed meals (CSM), rapeseed meal (RSM) and corn gluten meal (CGM) for Pseudobagrus ussuriensis (7.8 ± 0.06 g). Test diets were formulated to contain a 70:30 mixture of reference diet to test ingredient with chromic oxide (5 g kg–1) serving as the inert marker. ADCs of DM ranged from 49.94% (CGM) to 87.11% (PFM), the highest ADCs of DM were observed in PFM and the lowest was found in CGM. ADCs of CP in the test ingredients ranged from 74.92% (CGM) to 93.41% (SBM). ADCs of crude lipid ranged from 51.80% (CGM) to 94.07% (PFM) for fish. ADCs of energy ranged from 56.42% (CGM) to 90.09% (PFM). ADCs of phosphorus ranged from 21.81% (CSM) to 65.70% (PFM). AA availability for the test ingredients followed a similar pattern to ADCs of CP, in which values for PFM, NFM and MBM were generally higher (p < .05) than those of other protein ingredients. Among all plant meals, the AA availability values in SBM were higher (p < .05) than those in CGM, CSM and RSM. The availability of most AAs in CGM was the lowest (p < .05) among all tested ingredients. In conclusion, PFM and NFM are good sources of available protein and AAs. When fishmeal supply is limited, MBM and DDM are substitutes for fishmeal reduction in P. ussuriensis diets; at the same time, SBM and FSBM are also very acceptable protein feedstuffs. However, CSM, RSM and CGM could not be used at high levels in P. ussuriensis diets because of their inferior digestibilities. 相似文献
68.
69.
70.