全文获取类型
收费全文 | 9103篇 |
免费 | 547篇 |
国内免费 | 596篇 |
专业分类
林业 | 470篇 |
农学 | 638篇 |
基础科学 | 213篇 |
1245篇 | |
综合类 | 2557篇 |
农作物 | 632篇 |
水产渔业 | 538篇 |
畜牧兽医 | 2846篇 |
园艺 | 437篇 |
植物保护 | 670篇 |
出版年
2024年 | 34篇 |
2023年 | 106篇 |
2022年 | 181篇 |
2021年 | 230篇 |
2020年 | 220篇 |
2019年 | 234篇 |
2018年 | 228篇 |
2017年 | 296篇 |
2016年 | 259篇 |
2015年 | 262篇 |
2014年 | 331篇 |
2013年 | 476篇 |
2012年 | 566篇 |
2011年 | 641篇 |
2010年 | 548篇 |
2009年 | 478篇 |
2008年 | 525篇 |
2007年 | 519篇 |
2006年 | 427篇 |
2005年 | 359篇 |
2004年 | 325篇 |
2003年 | 365篇 |
2002年 | 494篇 |
2001年 | 479篇 |
2000年 | 321篇 |
1999年 | 197篇 |
1998年 | 44篇 |
1997年 | 47篇 |
1996年 | 35篇 |
1995年 | 46篇 |
1994年 | 46篇 |
1993年 | 39篇 |
1992年 | 50篇 |
1991年 | 40篇 |
1990年 | 54篇 |
1989年 | 52篇 |
1988年 | 36篇 |
1987年 | 40篇 |
1986年 | 31篇 |
1985年 | 34篇 |
1984年 | 51篇 |
1983年 | 27篇 |
1982年 | 26篇 |
1979年 | 28篇 |
1978年 | 28篇 |
1977年 | 27篇 |
1975年 | 25篇 |
1974年 | 37篇 |
1972年 | 30篇 |
1971年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
In the civil industry, quality is a key factor, so quality management and quality control play decisive roles in construction especially. At present, the main method of construction is quality controlling that engineers and technicians consult the standard and norm concerned, then check them one by one, and supervise the construction. It is not only inefficient but also easy to make mistake. Using computer technology in the quality control of construction will promote quality control level and improve management measures. Through the research of the quality control of construction,the system of quality control in construction is studied and developed, the structure of the software and its developed technology are expounded. 相似文献
102.
103.
EEG spot-recording for clinical patients in the bed is always advocated due to easing patients and making them comfortable. But EEG signals recorded in the ward exposed to various noisesand interference is less effective in the EEG analysis. Atemporal-spatial filter is designed for noise removing of clinical EEG signals, the first filtering is temporal filtering using band-pass filter, and the second filtering is spatial filtering with ICA-based spatial filter. Experimental results indicate that various noises and interferences, such as power interference, blinking, eyes movements, muscle moments, ECG artifacts, etc., are removed effectively, individually or simultaneously. 相似文献
104.
FU Hong yuan 《保鲜与加工》2001,(3):67-71
This article studies the opportunities and challenges in housing industry in China and proposes its development tendency. 相似文献
105.
Both total irradiation and diffuse irradiation are necessary to building energy consumption analysis. At the most cases in China,only total irradiation is available. So some method is needed to estimate diffuse irradiation. Relationship between daily diffuse irradiation and daily total irradiation is analyzed, based on data form Beijing and Chengdu.Polynomial models for Beijing and Chengdu are established to estimate K d form K t . Validation tests show good performance of the models. Monthly means of predicted daily diffuse irradiation is not significantly different from that of the original daily diffuse irradiation. Also,the auto_correlation function of the predicted diffuse fraction, K d is coincident with that of the original K d . Beijing model can accurately predict the data of Chengdu,which is significantly different from Beijing as to the climate,so it is recommended as the general model. 相似文献
106.
The method and principle of the parameter design for the power train of EV is explored and discussed,then the parametersof EV. based on SC7101 are reasonably selected.The method of calculating the SOC of Lead_acid battery is provided and the relation among the electromotive force,the interior resistance, the polarized resistance and the SOC are analyzed. The capacity is compensated according to the relation between the capacity and the temperature, which is the basis on which the energy management system is designed and improved. The dynamic model which reflects the dynamic characteristics of the power train is established,then the dynamic performance of the EV based on SC7101 is simulated, and the factors that affect the continuous mileage of EV are analyzed,the measures to increase the continuous mileage are provided.The result shows that the analysis of the electric characteristics of battery and the dynamic model are correct,and the dynamic performance perfectly meets the need of the design target. 相似文献
107.
In order to subdivide the market during the process of project planning and orient the group of client, then determine the sale price; on the condition that the traditional orientation procedure cant grasp the payment capability of the aim client, the anthors can adapt the powerful finance analysis ability of EXEL to design the procedure of determining the purchasing power and payments ability of the aim client, and shape a set of orientation system based on quantitative analysis method. The result is, the character of the aim client can be grasp accurately depend on this orientation system, and providing a scientific gist for the accurate orientation of price and lowing the risk of investment etc. 相似文献
108.
The 99% of all microorganisms in naturecannot be isolated by standard culture methods without conspicuous external characters to classify them morphologically. In addition, classification based on physiological or biochemical features are often fuzzy. Molecular techniques are used for uncultured microorganisms to explore the diversity of microbial communities and novel resources without the need of cultivation. DNA dynamics and cloning of PCR products obtained from environmental DNA is now routinely used to identify microbial populations in microbial ecology. For practical reasons the approach is not suited to study the complex dynamics of microbial communities in environment. Genetic fingerprinting techniques are better tools, which give complement for the traditional microbiological methods. The methods are rapid and relatively easy to perform, and they allow the simultaneous analysis of multiple samples, which makes it possible to compare the genetic diversity of microbial communities from different habitats, or to study the behaviour of individual communities over time. 相似文献
109.
110.
高含沙水流水轮机转轮的改型与抗磨蚀研究 总被引:1,自引:2,他引:1
进行高含沙水流水轮机转轮的改型研究,关键是要从正确确定转轮设计参数和轴面流道型式入手,根据三维水力设计理论,考虑导叶与转轮匹配关系进行叶型设计,针对不同破坏机理选择强磨蚀区采用金属喷涂或非金属保护等综合措施,使水轮机在高舍沙水流中运行时出力增加、抗磨蚀能力提高。 相似文献