全文获取类型
收费全文 | 117929篇 |
免费 | 5977篇 |
国内免费 | 10558篇 |
专业分类
林业 | 10996篇 |
农学 | 10412篇 |
基础科学 | 5867篇 |
15882篇 | |
综合类 | 56540篇 |
农作物 | 11228篇 |
水产渔业 | 3180篇 |
畜牧兽医 | 10480篇 |
园艺 | 3649篇 |
植物保护 | 6230篇 |
出版年
2024年 | 623篇 |
2023年 | 1743篇 |
2022年 | 3047篇 |
2021年 | 3293篇 |
2020年 | 3191篇 |
2019年 | 3996篇 |
2018年 | 2511篇 |
2017年 | 4111篇 |
2016年 | 5292篇 |
2015年 | 4846篇 |
2014年 | 6294篇 |
2013年 | 6476篇 |
2012年 | 8778篇 |
2011年 | 8602篇 |
2010年 | 7102篇 |
2009年 | 7057篇 |
2008年 | 6411篇 |
2007年 | 7606篇 |
2006年 | 6777篇 |
2005年 | 5661篇 |
2004年 | 4249篇 |
2003年 | 3737篇 |
2002年 | 2852篇 |
2001年 | 2546篇 |
2000年 | 2383篇 |
1999年 | 1872篇 |
1998年 | 1657篇 |
1997年 | 1467篇 |
1996年 | 1428篇 |
1995年 | 1383篇 |
1994年 | 1292篇 |
1993年 | 1148篇 |
1992年 | 1025篇 |
1991年 | 869篇 |
1990年 | 820篇 |
1989年 | 706篇 |
1988年 | 524篇 |
1987年 | 391篇 |
1986年 | 227篇 |
1985年 | 94篇 |
1984年 | 61篇 |
1983年 | 39篇 |
1982年 | 34篇 |
1981年 | 56篇 |
1980年 | 34篇 |
1979年 | 34篇 |
1978年 | 24篇 |
1977年 | 18篇 |
1976年 | 20篇 |
1955年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Zhang Peiyuan Liu Song 《保鲜与加工》1989,(2):10-16
It's recommended that the term coupled in temperature and strain is nonlinear and is significant in thermoelastic theory. Using the solution of linear coupled and uncoupled theory and selecting appropriate general coordinates, authers approach the nonlinear coupled problems with a variational method. A solution to the problem in half space, is given. It is shown that the difference between the nonlinear coupled theory and the linear coupled or uncoupled theory would be notable when the amplitute of temperature is much larger than that of the reference slate. 相似文献
992.
Wang Bingle Song Liquan 《保鲜与加工》1988,(2)
This paper presents a new method by using mass and acceleration parameters for balancing inertial force of mechanism. Compared with other balance methods, this one is simple, clear and superior in regularity when the balancing equation of complex mechanism is established, and its solving procedure is also easy. The new methcd is convenient to learn and use as well as convenient to program. 相似文献
993.
Yang Yudin Liu Dejun 《保鲜与加工》1990,(1):110-118
In this paper, taking a D1201 spindle as an example, we discuss the dynamic analysis of spindle by using the theory of the complex model, we also analyse the factors which effect the dynamic characterics of spindle and give results which arc reference value to improving the structure of spindle, 相似文献
994.
995.
In this paper, the historical reasons of formation of the village inside the city are analyzed. It is indicated that such situation for the villages inside the city are the result of joint action of both the villagers and the government. The foundation of villages inside the city laid on the simple compensation for farmers in confiscating the rural land and lack of intelligence aids. In this paper, the ideas and measures for their reconstruction are put forward based on consideration of the reasons of their formation and difficulties in the reconstruction. 相似文献
996.
This paper analyzes contractor's pricing connotation during bidding period with the implementation of National Standard GB50500-2003 and publish of document JB \206,expatiates the contents of measurements during construction period.Considering the problems derived from expenses of measurements during accounts settlement stage,a classified management method according to the characteristics of these measurements is put forward,and one step further,the rational pricing method of measurement items during the bidding period is suggested. 相似文献
997.
The authors discuss such questions for utility boiler as the complicated flameworks,combined quoting course, long cycle, hardly controlling the quoting veracity and so on. Based on the construction diagram of quoting design for utility boiler, Which is into the boiler sketch's construction and parameter characteristic. They are furnace construction, big screen superheater, high temperature superheater, low temperature superheater, high temperature reheater, low temperature reheater, economy coal implement, common use sign and standard sketch in boiler sketch, etc. According to demand of the quote design for utility boiler, the CAD environment of quoting system based on characteristic construction and parameter are developed. Total construction of this environment , developing characteristics and function of this system are given. 相似文献
998.
In TT&C system,unified spread spectrum framework and adaptive antenna digital beamforming technologies are used to track, telemetry and command objects. Constant modulus array (CMA) and adaptive signal canceller estimate the direction of arrival (DOA) of every signal and use the optimum weighted vector to form the beams. The phase weighted vectors estimated from DOA improve the processing gain as well as being utilized in the transmitting of tele command signal to form the beam of specified object. Its processing performance is researched and simulated in this paper. 相似文献
999.
FENG Wei-min~ 《保鲜与加工》2004,(6):103-108
The society-economy-environment appraisal for construction project can help our government to control macro-economy, make correlation policy and formulate laws and draw up city plan.It has great influence on the sustainable development of our society and it is the demand of the law for the environment evaluation in China.This paper introduced the basic structure of society-economy-environment appraisal system for construction project and the thought of elements transaction.Using the method of AHP, the model of project analyzing and optimizing selection is designed.For the more, the methods of the optimizing models on the selected schemes are put forward.Finally, the integrative analysis has been made on the system design and appliance of this appraisal system. 相似文献
1000.
The analysis of vibration response of structure with TMD is carried out under earthquake ,considering the ground-structure interaction. The varying rule of square difference of displacement of structure with the TMD on or off by changing the first inherent frequency is also presented .It has been proved by comparing and analyzing that a TMDstructure with optimum parameters can efficiently reduce the vibration of structure under strong wind and earthquake,when the main frequency of the ground motion is within the range of TMD vibration reducing frequency. 相似文献