全文获取类型
| 收费全文 | 1069篇 |
| 免费 | 40篇 |
| 国内免费 | 2篇 |
专业分类
| 林业 | 12篇 |
| 农学 | 18篇 |
| 基础科学 | 16篇 |
| 43篇 | |
| 综合类 | 528篇 |
| 农作物 | 14篇 |
| 水产渔业 | 12篇 |
| 畜牧兽医 | 291篇 |
| 园艺 | 23篇 |
| 植物保护 | 154篇 |
出版年
| 2022年 | 7篇 |
| 2021年 | 7篇 |
| 2019年 | 9篇 |
| 2018年 | 9篇 |
| 2017年 | 14篇 |
| 2016年 | 10篇 |
| 2015年 | 12篇 |
| 2014年 | 11篇 |
| 2013年 | 40篇 |
| 2012年 | 49篇 |
| 2011年 | 51篇 |
| 2010年 | 26篇 |
| 2009年 | 13篇 |
| 2008年 | 50篇 |
| 2007年 | 47篇 |
| 2006年 | 56篇 |
| 2005年 | 44篇 |
| 2004年 | 59篇 |
| 2003年 | 56篇 |
| 2002年 | 47篇 |
| 2001年 | 38篇 |
| 2000年 | 51篇 |
| 1999年 | 29篇 |
| 1998年 | 7篇 |
| 1997年 | 12篇 |
| 1996年 | 9篇 |
| 1995年 | 11篇 |
| 1994年 | 9篇 |
| 1993年 | 16篇 |
| 1992年 | 25篇 |
| 1991年 | 24篇 |
| 1990年 | 16篇 |
| 1989年 | 15篇 |
| 1988年 | 11篇 |
| 1987年 | 22篇 |
| 1986年 | 10篇 |
| 1985年 | 7篇 |
| 1984年 | 8篇 |
| 1983年 | 9篇 |
| 1982年 | 12篇 |
| 1981年 | 8篇 |
| 1980年 | 9篇 |
| 1973年 | 13篇 |
| 1972年 | 10篇 |
| 1971年 | 11篇 |
| 1970年 | 9篇 |
| 1969年 | 6篇 |
| 1968年 | 8篇 |
| 1967年 | 10篇 |
| 1966年 | 13篇 |
排序方式： 共有1111条查询结果，搜索用时 15 毫秒
81.
Modern laser technology has revolutionized the sensitivity and precision of spectroscopy by providing coherent light in a spectrum spanning the infrared, visible, and ultraviolet wavelength regimes. However, the generation of shorter-wavelength coherent pulses in the x-ray region has proven much more challenging. The recent emergence of high harmonic generation techniques opens the door to this possibility. Here we review the new science that is enabled by an ability to manipulate and control electrons on attosecond time scales, ranging from new tabletop sources of coherent x-rays to an ability to follow complex electron dynamics in molecules and materials. We also explore the implications of these advances for the future of molecular structural characterization schemes that currently rely so heavily on scattering from incoherent x-ray sources. 相似文献
82.
Smith JD Cappa CD Wilson KR Messer BM Cohen RC Saykally RJ 《Science (New York, N.Y.)》2004,306(5697):851-853
A strong temperature dependence of oxygen K-edge x-ray absorption fine structure features was observed for supercooled and normal liquid water droplets prepared from the breakup of a liquid microjet. Analysis of the data over the temperature range 251 to 288 kelvin (-22 degrees to +15 degrees C) yields a value of 1.5 +/- 0.5 kilocalories per mole for the average thermal energy required to effect an observable rearrangement between the fully coordinated ("ice-like") and distorted ("broken-donor") local hydrogen-bonding configurations responsible for the pre-edge and post-edge features, respectively. This energy equals the latent heat of melting of ice with hexagonal symmetry (ice Ih) and is consistent with the distribution of hydrogen bond strengths obtained for the "overstructured" ST2 model of water. 相似文献
83.
Cohen J 《Science (New York, N.Y.)》2008,319(5866):1026-1027
84.
85.
Effects of basal debris on glacier flow 总被引：1，自引：0，他引：1
Iverson NR Cohen D Hooyer TS Fischer UH Jackson M Moore PL Lappegard G Kohler J 《Science (New York, N.Y.)》2003,301(5629):81-84
Glacier movement is resisted partially by debris, either within glaciers or under glaciers in water-saturated layers. In experiments beneath a thick, sliding glacier, ice containing 2 to 11% debris exerted shear traction of 60 to 200 kilopascals on a smooth rock bed, comparable to the total shear traction beneath glaciers and contrary to the usual assumption that debris-bed friction is negligible. Imposed pore-water pressure that was 60 to 100% of the normal stress in a subglacial debris layer reduced shear traction on the debris sufficiently to halt its deformation and cause slip of ice over the debris. Slip resistance was thus less than debris shearing resistance. 相似文献
86.
87.
Cohen J 《Science (New York, N.Y.)》2003,299(5611):1290-1291
88.
89.
Cohen J 《Science (New York, N.Y.)》2007,318(5853):1048-1049
90.
P T Ninan T M Insel R M Cohen J M Cook P Skolnick S M Paul 《Science (New York, N.Y.)》1982,218(4579):1332-1334
The ethyl ester of beta-carboline-3-carboxylic acid has a high affinity for benzodiazepine receptors in the brain. In the rhesus monkey this substance produces an acute behavioral syndrome characterized by dramatic elevations in heart rate, blood pressure, plasma cortisol, and catecholamines. The effects are blocked by benzodiazepines and the specific benzodiazepine receptor antagonist Ro 15-1788. The benzodiazepine receptor may consist of several subsites or functional domains that independently recognize agonist, antagonists, or "active" antagonists such as beta-carboline-3-carboxylic acid ethyl ester. These results suggest that the benzodiazepine receptor is involved in both the affective and physiological manifestations of anxiety, and that the administration of beta-carboxylic acid ethyl ester to monkeys may provide a reliable and reproducible animal model of human anxiety. 相似文献