全文获取类型
收费全文 | 6259篇 |
免费 | 529篇 |
国内免费 | 640篇 |
专业分类
林业 | 678篇 |
农学 | 469篇 |
基础科学 | 291篇 |
1290篇 | |
综合类 | 2570篇 |
农作物 | 166篇 |
水产渔业 | 658篇 |
畜牧兽医 | 551篇 |
园艺 | 101篇 |
植物保护 | 654篇 |
出版年
2024年 | 67篇 |
2023年 | 221篇 |
2022年 | 279篇 |
2021年 | 291篇 |
2020年 | 351篇 |
2019年 | 371篇 |
2018年 | 224篇 |
2017年 | 312篇 |
2016年 | 309篇 |
2015年 | 270篇 |
2014年 | 360篇 |
2013年 | 388篇 |
2012年 | 475篇 |
2011年 | 442篇 |
2010年 | 350篇 |
2009年 | 376篇 |
2008年 | 291篇 |
2007年 | 359篇 |
2006年 | 280篇 |
2005年 | 216篇 |
2004年 | 199篇 |
2003年 | 153篇 |
2002年 | 143篇 |
2001年 | 106篇 |
2000年 | 88篇 |
1999年 | 70篇 |
1998年 | 67篇 |
1997年 | 37篇 |
1996年 | 40篇 |
1995年 | 52篇 |
1994年 | 44篇 |
1993年 | 31篇 |
1992年 | 38篇 |
1991年 | 28篇 |
1990年 | 20篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1984年 | 6篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 3篇 |
排序方式: 共有7428条查询结果,搜索用时 62 毫秒
61.
62.
63.
The externality of surrounding is introduced into the 2-capital of economical increasing models, which includes human factors, to explore the influences of circumstances contradiction on the human capital formation. The normal and special nash equilibrium of environmental and human capital is presented through a limited boundary model of overlapping generations. The character of equilibrium trail and its economical meaning are examined. The study on the model shows that laissez faire economy will be either stagnant,growing,or collapsing in the long-run,depending on the returns of the learning technology with respect to the two kinds of capital,the initial state of economy,and the relative price of the environmental and consumption goods. 相似文献
64.
Mathematical model of power frequency electric field is established based on Charge Simulation Method(CSM) to analyze power frequency electric field caused by EHV lines with overhead ground wires and its effect, which are entering the megalopolis. Calculative method on the electric field under the transmission lines is analyzed and validated. According to the criterion of environmental evaluation, the distributing characteristic of electric field is summarized, in case of various arrangement manners of lines. At last, some advice and methods of eliminating electric field under the transmission lines entering the megalopolis is proposed with regard to protecting environment. 相似文献
65.
In this paper we concider the problem of stability of stochastic evolution systemsin Hilbert space drived by a cylindrical Brownian mothin. We regard the stochestic evolutionequation dXt = AXtdt +G(Xt)dBt as a deterministic system of the form dXt=AXtdt under randomperturbation,and obtain stability of its solution. It is shown that under certain assumptions,itsevolution solution and L2-contimuous evulution solution are exponertially stable. 相似文献
66.
JIA Yan-yan 《保鲜与加工》2004,(2):106-109
In this paper, the problems of bringing natural resources and environmental condition into accounting are discussed and lay emphasis on object measurement, imaging and disclosure in accounting report of environmental accounting. The author suggests that the environmental accounting is the necessary production of global economy for sustainable development in modern society; it is also a new ecological accounting subject formed by the result of environmental economies and accounting penetrating into each other. As a contribution of accounting circles to sustainable development, environmental accounting has become a hot topic in recent years. 相似文献
67.
68.
The basic principle of infinite-dimensional dynamic system is to try to reduce the original infinite-dimensional system to an infinite-dimensional system. However,due to the unknown structure of the reduced system, it is difficult to describe its dynamical behaviour. To overcome this difficulty, the idea of approximate inertial manifolds is introduced, for NSE, the existence of AIM was studied, it is shown that the global attractor lies within a neighborhood of the graph of an Lipschitz function by the squeezing property. In this paper, by constructing a finite dimensional solution sequence, we will prove that it tends to the global attractor, theoretically, this provides a metod of constructing the asymptotic attractors, theoretically, this provides a method of constructing the asymptotic attractors for the evolution equations. 相似文献
69.
This papar presents an evolution model in business behaviors-the L-S Business Strategies,gives some examples and predictions which support these strategies,and analyzes the relationship between the industrial organizations in China and the L-S Business strategies. 相似文献
70.
Gao Shixian 《保鲜与加工》1988,(3)
The problem of fuzzy evaluation of environmental pollution is importantboth in environment science and in environmental protection.Usual evaluationmethods have their own characteristics.This paper puts forward a mathematicalmodel of fuzzy evaluation method in grades by means of systematic analysisfor environmental pollution.At the same time,it assigns weighted values byordering based on paired comparison. 相似文献