全文获取类型
收费全文 | 147100篇 |
免费 | 14240篇 |
国内免费 | 9169篇 |
专业分类
电工技术 | 11797篇 |
技术理论 | 2篇 |
综合类 | 18149篇 |
化学工业 | 16474篇 |
金属工艺 | 6324篇 |
机械仪表 | 10635篇 |
建筑科学 | 18254篇 |
矿业工程 | 6646篇 |
能源动力 | 4902篇 |
轻工业 | 8278篇 |
水利工程 | 6515篇 |
石油天然气 | 6364篇 |
武器工业 | 2013篇 |
无线电 | 10193篇 |
一般工业技术 | 18665篇 |
冶金工业 | 5742篇 |
原子能技术 | 2335篇 |
自动化技术 | 17221篇 |
出版年
2024年 | 604篇 |
2023年 | 1692篇 |
2022年 | 3292篇 |
2021年 | 3839篇 |
2020年 | 4366篇 |
2019年 | 3797篇 |
2018年 | 3654篇 |
2017年 | 4639篇 |
2016年 | 5165篇 |
2015年 | 5381篇 |
2014年 | 8780篇 |
2013年 | 8426篇 |
2012年 | 11166篇 |
2011年 | 11372篇 |
2010年 | 8829篇 |
2009年 | 9190篇 |
2008年 | 8549篇 |
2007年 | 10617篇 |
2006年 | 9282篇 |
2005年 | 7799篇 |
2004年 | 6425篇 |
2003年 | 5541篇 |
2002年 | 4595篇 |
2001年 | 3828篇 |
2000年 | 3383篇 |
1999年 | 2908篇 |
1998年 | 2308篇 |
1997年 | 2013篇 |
1996年 | 1697篇 |
1995年 | 1524篇 |
1994年 | 1283篇 |
1993年 | 946篇 |
1992年 | 834篇 |
1991年 | 587篇 |
1990年 | 480篇 |
1989年 | 488篇 |
1988年 | 344篇 |
1987年 | 201篇 |
1986年 | 161篇 |
1985年 | 72篇 |
1984年 | 72篇 |
1983年 | 37篇 |
1982年 | 45篇 |
1981年 | 58篇 |
1980年 | 31篇 |
1979年 | 39篇 |
1978年 | 19篇 |
1977年 | 16篇 |
1975年 | 18篇 |
1959年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
闩体的刚度和强度必须满足设计要求。用有限元法对复杂结构件进行力学性能分析是非常有效的方法。采用ANSYS软件对闩体进行了刚度和强度分析,得出了有用的结论,可供相关设计借鉴。 相似文献
62.
固定床吸附器透过曲线参数优化方法 总被引:3,自引:1,他引:2
开发了一种固定床吸附器透过曲线参数估值的优化方法,用Basic语言编制了运算程序,并在普及型286微机上考核了该法的可靠性,相对误差在1%以下,运算机时7.5min。 相似文献
63.
Jos A. Grimbergen Koen Visscher Daniel S. Gomes De Mesquita G. J. Brakenhoff 《Yeast (Chichester, England)》1993,9(7):723-732
Individual yeast cells can be successfully isolated and recultured on plates with a new isolation method making use of optical trapping with infrared laser light. The cells can be selected on morphological criteria by high resolution microscopy. The isolation device is constructed from two coverslips separated by spacers, in which selected cells are transferred to a plastic capillary, using the optical trap. To test the procedure, selection experiments were done with a mixture of two Saccharomyces cerevisiae strains, distinguishable both in fluorescence microscopy and on agar plates. These experiments showed that only selected cells were isolated, and close to 100% of the isolated stationary-phase cells formed colonies on agar plates, indicating a high recovery. A lower recovery was obtained with exponential-phase cells, possibly because of a higher sensitivity to laser irradiation. Applications for this method may include the isolation of mutants with altered morphology and the isolation of subpopulations of yeast cultures, for their separate investigation or for the initiation of pure cultures. 相似文献
64.
Kosuke Kurokawa 《Electrical Engineering in Japan》1993,113(4):54-65
Solar radiation has an irregularly varying factor due to a basic day and night cycle and climatic conditions. For such conditions a data sampling interval is important to ensure the accuracy of energy monitoring in a photovoltaic system. While treating a system monitoring equipment as a black box. the author has developed the method of calibrating an energy-integrating function. At first for various input waveforms, the relationship between sampling intervals and quasi-integration outputs have been examined by trapezoidal rule. In the numerical simulation the phases of the sampling clock also are considered Then it is concluded that a sampling interval can be inspected through outside observation only by using a rectangular single pulse. By applying the pulse to the energy-integrating process, two kinds of integrated outputs can be obtained for different sampling phases. The calculated difference between both outputs can uniquely give the sampling interval being inspected. Conditions to ensure measuring accuracy are discussed and the validity of this method has been demonstrated experimentally. Practical calibrating procedures also are proposed for the integrating function of PV system monitoring. 相似文献
65.
密集平行束孔落矿的底盘漏斗采矿方案的特点是:用密集严行束孔落矿;凿岩与出矿水平合二为一;实行“掘井、劈漏、落矿三位一体”的回采工艺。该方案结构简单、采切比低、工人劳动强度低,适于开采缓倾斜顶底围岩不稳固的中厚以上矿体。 相似文献
66.
G.Y. Sha F.C. Jiang D. Wang D.K. Liu and R.T.Department of Mechanical Engineering Harbin Engineering University Harbin ChinaShenyang National Laboratory for Materials Science Institute of Metal Research The Chinese Academy of Sciences Shenyang China 《金属学报(英文版)》2002,15(6):556-560
An experimental-numerical method for measuring dynamic crack propagating velocities under stress wave loading is established in this paper. The experiments of the three-point bend specimen are done on the improved Hopkinson bar. Deflection of loading point, dynamic load and instantaneous crack length are measured, then crack propagating velocities are calculated. Experiments on 40Cr steel show that the results given by this method have a good agreement with that obtained by the resistance fracture gage method. Therefore this method is feasible for measuring crack propagating velocities under high loading rate and will have wide application. 相似文献
67.
Distortion as a result of the quenching process is predominantly due to the thermal gradient and phase transformations within
the component. Compared with traditional liquid quenching, the thermal boundary conditions during gas quenching are relatively
simple to control. By adjusting the gas-quenching furnace pressure, the flow speed, or the spray nozzle configuration, the
heat-transfer coefficients can be designed in terms of both the component geometry and the quenching time. The purpose of
this research is to apply the optimization methodology to design the gas-quenching process. The design objective is to minimize
the distortion caused by quenching. Constraints on the average surface hardness, and its distribution and residual stress
are imposed. The heat-transfer coefficients are used as design variables. DEFORM-HT is used to predict material response during
quenching. The response surface method is used to obtain the analytical models of the objective function and constraints in
terms of the design variables. Once the response surfaces of the objective and constraints are obtained, they are used to
search for the optimum heat-transfer coefficients. This process is then used instead of the finite-element analysis. A one-gear
blank case study is used to demonstrate the optimization scheme. 相似文献
68.
萃取预分离法分离富铕中钇矿新工艺 总被引:2,自引:0,他引:2
采用一种新的串级萃取方式--萃取预分离法分离富铕中钇矿的新工艺.原料首先流入十几的三出口预先粗分离工艺,其萃余液La~Gd(TbDy)直接流入Nd/Sm工艺;中间出口流入(Gd)Tb~HoY(Er)Gd~Dy/Ho~LuY细分离工艺;出口负载有机相(Ho)Er~LuY流入Gd~Dy/Ho~LuY的洗涤段.结果表明,新工艺的粗分离工艺将占原料约70%的La~Gd(TbDy)预分离掉,使流入Gd~Dy/Ho~LuY工艺的稀土量减少约70%;由于Gd~Dy/Ho~LuY分组的萃余液GdTbDy含Ho2O3小于0.03%,省去原工艺的GdTbDy/HoY分离;新工艺的处理能力提高30%,酸碱消耗减少20%以上,贵重稀土元素Eu和Tb的存槽量大大减少. 相似文献
69.
70.