全文获取类型
收费全文 | 96409篇 |
免费 | 5827篇 |
国内免费 | 6894篇 |
专业分类
林业 | 11967篇 |
农学 | 6694篇 |
基础科学 | 7102篇 |
13416篇 | |
综合类 | 42626篇 |
农作物 | 4694篇 |
水产渔业 | 2546篇 |
畜牧兽医 | 10110篇 |
园艺 | 2899篇 |
植物保护 | 7076篇 |
出版年
2024年 | 633篇 |
2023年 | 1819篇 |
2022年 | 2815篇 |
2021年 | 3325篇 |
2020年 | 3244篇 |
2019年 | 3701篇 |
2018年 | 2023篇 |
2017年 | 3335篇 |
2016年 | 4257篇 |
2015年 | 3533篇 |
2014年 | 5269篇 |
2013年 | 5261篇 |
2012年 | 7327篇 |
2011年 | 7299篇 |
2010年 | 5739篇 |
2009年 | 5900篇 |
2008年 | 5205篇 |
2007年 | 6019篇 |
2006年 | 5212篇 |
2005年 | 4172篇 |
2004年 | 3438篇 |
2003年 | 3006篇 |
2002年 | 2293篇 |
2001年 | 2158篇 |
2000年 | 1881篇 |
1999年 | 1537篇 |
1998年 | 1247篇 |
1997年 | 1143篇 |
1996年 | 965篇 |
1995年 | 1007篇 |
1994年 | 856篇 |
1993年 | 697篇 |
1992年 | 616篇 |
1991年 | 531篇 |
1990年 | 461篇 |
1989年 | 367篇 |
1988年 | 285篇 |
1987年 | 182篇 |
1986年 | 91篇 |
1985年 | 61篇 |
1984年 | 40篇 |
1983年 | 14篇 |
1982年 | 35篇 |
1981年 | 27篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1978年 | 19篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1955年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
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
952.
953.
The design of multi-controller and multi-mode control law is presented for the three-link Acrobot on horizontal bar by employing Human simulated intelligent control method based on sensory-motor Schema.Imitated the characteristics of gymnast's swing-up and handstand movement,the control process of robot is divided by six sequence phase.Then the sensory cell and motor cell and the group of sensory-motor schema is designed based on the analysis of quality-quantity combination.The simulation results show that the controller ensures the gesture and the energy to the desired goal,farther more the motion control of giant swing backword is realized in the simulation. 相似文献
954.
Control Strategy and Simulation Study on NiMH Battery Quick Charging for Regenerative Braking of HEV
Based on the result of NiMH battery performance experiments, changing trend of maximal temperature and difference in temperature of HEV NiMH battery in different SOC and different charging current is analyzed. Considering the working situation of HEV NiMH battery and the theory of battery quick charging, a control strategy for NiMH battery quick charging is described which adapts to HEV regenerative braking system based on Mascc law. By Modeling and simulating the process of NiMH battery quick charging with this strategy, constant voltage charge method and constant current charge method, validates this control strategy. 相似文献
955.
The purpose of a parallel hybrid electric vehicle(PHEV) is for the best energy distribution between internal-combustion engine(ICE) and electric motor though the appropriate control strategy.It can not only keep the advantage of the ultra-low emission of electric vehicles(EV),but also take advantages of the hyperbaric energy of ICE.Simulation model for PHEV is built based on CRUISE,an auxiliary control strategy is designed,and then parameter simulation study on the control strategy is performed.The simulation results show that according to the different control requirements,the vehicle performance can be improved by adjusting!the corresponding control parameters. 相似文献
956.
The authors analyze the influence in vector controlled induction machine caused by parameter variation and main flux saturation affects speed estimation of adaptive state observer. According to simulation of the modified scheme with saturated induction motor model, it is proved that when the vector control scheme operates in field weakening region, the main flux saturation will obviously influence precision of speed observer and bring great error of speed estimation. Thereby, the main flux saturation should be compensated to improve performance of the vector control system. 相似文献
957.
In urban design, only by continuous and dynamic research work from design to finally putting it into practice, can we made good control on city appearance. This article analyzes nowadays defects in our urban design from two aspects as the result establishment and validated control, and tries to conceive a feasibility plan to solve the problem. 相似文献
958.
In this paper,four models are selected as the representatives and applied to nonlinear dynamic analysis program for space frames which is based on the beam-column elements using the finite element flexibility method and the fiber model.Park's test on combined axial and bending columns under cyclic loading are taken as the calibrations,comparisons to material and structural member level are drawn and the analytical results of various models are discussed. 相似文献
959.
A video Monitor &Control system of tunnel based on DSP/BIOS is proposed,which is different from traditional video Monitor & Control system.It uses DSP to process image,and uses enhanced video input processor to qcquire image.This system satisfies all requirements of video supervision,and is a low cost system.It has a good application foreground.The system has been confirmed as a good veracity and practicability system through testing in the Zhongliang Mountain tunnel of Chongqing. 相似文献
960.
According to the requirements of communication power supply, such as high reliability, wide application and high availability, the authors raise a new remote control design for a multi-output power supply for communication equipment based on TCPIP protocol and embedded technology. Then the hardware design is given for the system is discussed based on Ethernet professional chip PRTL8019AS and related circuits. The firmware software design for the salve-computer based TCPIP technology, and the soft design of communieation and control for the master-computer are proposed based on Winsoek and MFC technology in detail A test machine is built to do the testing, the test results prove that the test machine works stably and well, satisfies the design rules and also provides a feasible method for the remote supervise in communication power supplier whose requirement includes remote supervise, no-people on duty and so on. 相似文献