全文获取类型
收费全文 | 249篇 |
免费 | 12篇 |
专业分类
林业 | 11篇 |
基础科学 | 1篇 |
23篇 | |
综合类 | 94篇 |
农作物 | 3篇 |
水产渔业 | 26篇 |
畜牧兽医 | 86篇 |
园艺 | 3篇 |
植物保护 | 14篇 |
出版年
2021年 | 3篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2015年 | 6篇 |
2013年 | 10篇 |
2012年 | 10篇 |
2011年 | 9篇 |
2010年 | 11篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 10篇 |
2004年 | 4篇 |
2003年 | 9篇 |
2002年 | 8篇 |
2001年 | 9篇 |
1998年 | 9篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1981年 | 5篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 7篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1969年 | 6篇 |
1968年 | 2篇 |
1967年 | 4篇 |
1966年 | 2篇 |
1963年 | 2篇 |
1956年 | 2篇 |
1902年 | 2篇 |
1898年 | 3篇 |
排序方式: 共有261条查询结果,搜索用时 31 毫秒
101.
Scanning electrochemical microscopy is a scanning probe technique that is based on faradaic current changes as a small electrode is moved across the surface of a sample. The images obtained depend on the sample topography and surface reactivity. The response of the scanning electrochemical microscope is sensitive to the presence of conducting and electroactive species, which makes it useful for imaging heterogeneous surfaces. The principles and instrumentation used to obtain images and surface reaction-kinetic information are discussed, and examples of applications to the study of electrodes, minerals, and biological samples are given. 相似文献
102.
The interaction between tectonism and erosion produces rugged landscapes in actively deforming regions. In the northwestern Himalaya, the form of the landscape was found to be largely independent of exhumation rates, but regional trends in mean and modal elevations, hypsometry (frequency distribution of altitude), and slope distributions were correlated with the extent of glaciation. These observations imply that in mountain belts that intersect the snowline, glacial and periglacial processes place an upper limit on altitude, relief, and the development of topography irrespective of the rate of tectonic processes operating. 相似文献
103.
104.
Pierce HF 《Science (New York, N.Y.)》1934,80(2076):339-341
105.
Dalinsky Sabrina A. Lolya Lewis M. Maguder Jennifer L. Pierce Joshua L. B. Kelting Daniel L. Laxson Corey L. Patrick David A. 《Water, air, and soil pollution》2014,225(6):1-15
Nuisance odors generation from waste and wastewater treatment plants are a cause of public discomfort and complaints. This situation impairs the air quality and represents a growing social and public health problem, especially in developing countries. Several modeling approaches have been developed and successfully implemented in the frame of a wastewater treatment plant for both the biological treatment and physicochemical processes. The mathematical modeling of the odor generation process is still considered a quite complex issue, mainly due to the fact that olfactory nuisance can be caused by many different chemical compounds and the perception of odors is influenced by subjective thresholds. Moreover, the impact of odor sources on air quality is highly conditioned by complex atmospheric dispersion processes. This review presents a critical state-of-art and assessment where information related to odor emissions impact studies as well as modeling applications are compiled and discussed. 相似文献
106.
Henrique Silva Silveira Duarte Laércio Zambolim Alexandre Sandri Capucho Antonio Fernandes Nogueira Júnior André Wilson Campos Rosado Carine Rezende Cardoso Pierce Anderson Paul Eduardo Seiti Gomide Mizubuti 《European journal of plant pathology / European Foundation for Plant Pathology》2013,137(2):249-257
Standard area diagrams (SADs) to assess the severity of potato early blight (Alternaria grandis) on leaves of potato (Solanum tuberosum L.) were developed and validated. The proposed SADs include images of leaves with 10 distinct disease severities (0.1, 1, 3, 5, 10, 20, 40, 60, 80 and 100 %). The SADs were validated by 12 raters who had no previous experience in evaluating plant disease. Lin’s concordance correlation analysis of estimated vs. actual disease severity (based on image analysis) showed that precision and accuracy improved for most raters using the SADs, compared to assessments made without the SADs. The SADs improved accuracy (coefficient of bias, C b ?=?0.97 and 0.99, without and with SADs, respectively) and agreement (Lin’s concordance correlation coefficient, ρ c ?=?0.91 and 0.98 without and with SADs, respectively) of the estimates of severity. Severity estimates were more reliable when using SADs (coefficient of determination, R 2 ?=?0.80 unaided and R 2 ?=?0.95 with SADs, and the intra-class correlation ρ?=?0.86 without SADs and ρ?=?0.97 using the SADs). The SADs improved raters’ ability to accurately, precisely and reliably estimate potato early blight severity, and as such can be used to assess severity for several purposes, including breeding for resistance, fungicide screening, and pathotype characterization. 相似文献
107.
与使用无机矿物质相比,在猪饲料中添加有机矿物质可给养猪生产各个阶段的生产性能和环境带来益处。由于有机矿物质具有较好的养分利用率,因此它不仅能使猪的生产性能不受影响,而且还能使养猪生产的净收益得到提高。 相似文献
108.
F. E. Dowell E. B. Maghirang F. Xie G. L. Lookhart R. O. Pierce B. W. Seabourn S. R. Bean J. D. Wilson O. K. Chung 《Cereal Chemistry》2006,83(5):529-536
The accuracy of using near‐infrared spectroscopy (NIRS) for predicting 186 grain, milling, flour, dough, and breadmaking quality parameters of 100 hard red winter (HRW) and 98 hard red spring (HRS) wheat and flour samples was evaluated. NIRS shows the potential for predicting protein content, moisture content, and flour color b* values with accuracies suitable for process control (R2 > 0.97). Many other parameters were predicted with accuracies suitable for rough screening including test weight, average single kernel diameter and moisture content, SDS sedimentation volume, color a* values, total gluten content, mixograph, farinograph, and alveograph parameters, loaf volume, specific loaf volume, baking water absorption and mix time, gliadin and glutenin content, flour particle size, and the percentage of dark hard and vitreous kernels. Similar results were seen when analyzing data from either HRW or HRS wheat, and when predicting quality using spectra from either grain or flour. However, many attributes were correlated to protein content and this relationship influenced classification accuracies. When the influence of protein content was removed from the analyses, the only factors that could be predicted by NIRS with R2 > 0.70 were moisture content, test weight, flour color, free lipids, flour particle size, and the percentage of dark hard and vitreous kernels. Thus, NIRS can be used to predict many grain quality and functionality traits, but mainly because of the high correlations of these traits to protein content. 相似文献
109.
PO Wennberg TF Hanisco L Jaegle DJ Jacob EJ Hintsa EJ Lanzendorf JG Anderson R Gao ER Keim SG Donnelly LAD Negro DW Fahey SA McKeen RJ Salawitch CR Webster RD May RL Herman MH Proffitt JJ Margitan EL Atlas SM Schauffler F Flocke CT McElroy TP Bui 《Science (New York, N.Y.)》1998,279(5347):49-53
The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3 in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HOx required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production of O3 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about 1 part per billion by volume each day. This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more O3 than expected. 相似文献
110.
Subpolar North Atlantic proxy records document millennial-scale climate variations 500,000 to 340,000 years ago. The cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle. These findings suggest that such climate variations are inherent to the late Pleistocene, regardless of glacial state. Sea surface temperature during the warm peak of Marine Isotope Stage 11 (MIS 11) varied by 0.5 degrees to 1 degrees C, less than the 4 degrees to 4.5 degrees C estimated during times of ice growth and the 3 degrees C estimated for glacial maxima. Coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature. 相似文献