全文获取类型
收费全文 | 97274篇 |
免费 | 6219篇 |
国内免费 | 3634篇 |
专业分类
电工技术 | 10366篇 |
技术理论 | 21篇 |
综合类 | 10197篇 |
化学工业 | 5412篇 |
金属工艺 | 1410篇 |
机械仪表 | 4756篇 |
建筑科学 | 16152篇 |
矿业工程 | 4116篇 |
能源动力 | 3061篇 |
轻工业 | 3638篇 |
水利工程 | 5437篇 |
石油天然气 | 2322篇 |
武器工业 | 494篇 |
无线电 | 8320篇 |
一般工业技术 | 5846篇 |
冶金工业 | 5742篇 |
原子能技术 | 729篇 |
自动化技术 | 19108篇 |
出版年
2024年 | 141篇 |
2023年 | 755篇 |
2022年 | 1497篇 |
2021年 | 2173篇 |
2020年 | 2337篇 |
2019年 | 1619篇 |
2018年 | 1549篇 |
2017年 | 2029篇 |
2016年 | 2554篇 |
2015年 | 2906篇 |
2014年 | 7776篇 |
2013年 | 6366篇 |
2012年 | 7294篇 |
2011年 | 7533篇 |
2010年 | 5776篇 |
2009年 | 6188篇 |
2008年 | 6120篇 |
2007年 | 7446篇 |
2006年 | 6556篇 |
2005年 | 5540篇 |
2004年 | 4829篇 |
2003年 | 4171篇 |
2002年 | 3231篇 |
2001年 | 2449篇 |
2000年 | 1933篇 |
1999年 | 1442篇 |
1998年 | 1010篇 |
1997年 | 748篇 |
1996年 | 606篇 |
1995年 | 524篇 |
1994年 | 382篇 |
1993年 | 286篇 |
1992年 | 222篇 |
1991年 | 174篇 |
1990年 | 116篇 |
1989年 | 135篇 |
1988年 | 101篇 |
1987年 | 55篇 |
1986年 | 77篇 |
1985年 | 100篇 |
1984年 | 93篇 |
1983年 | 100篇 |
1982年 | 39篇 |
1981年 | 24篇 |
1980年 | 16篇 |
1979年 | 16篇 |
1977年 | 14篇 |
1975年 | 7篇 |
1961年 | 9篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
31.
Kang Zhang Rong‐rong Wang Kai‐rui Zhang Fei Cheng Yu Tian Yi Lin Mi Zhou Pu‐xin Zhu 《Polymer International》2020,69(3):274-279
A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry 相似文献
32.
Smart grid has opened up a new role of “prosumer” in an energy value network, transforming many conventional energy consumers into prosumers, who not only generate green energy but also share the surplus with utilities and other consumers. The concept of a goal-oriented prosumer community group (PCG) has emerged recently as an effective way to fulfill sustainable energy exchange. Such community-based energy sharing networks comprise multiple irreconcilable objectives such as demand constraints, cost constraints, and income maximization. In many cases, one goal may be achievable only at the expense of other goals. This necessitates the development of an effective framework to manage the multiple goals and reduce the gap with their achievement levels. Therefore, in this research paper, an effective framework is developed to negotiate among the multiple goals and thus to define optimal mutual goals for each PCG in a more sustainable manner using multiple-criteria goal programming techniques. Simulation results are presented to illustrate how the methods work in practical situations, where each of the objective measure is given a target value and the unwanted deviations from this set are minimized in an achievement function. 相似文献
33.
电网的安全水平主要取决于其使用产品的质量是否过关。如果产品的质量较好,则能建造出优质的电网,电网的安全水平便会随之提高。因此,应加强对产品质量的监督管理,从而提高电网的安全水平。我们可建立质量监督管理系统,及时抽检出质量不过关的产品,从而消除电网运行过程中潜在的安全隐患。 相似文献
34.
为将我国最严格水资源管理制度的实践与二元水循环理论相结合,提高“三条红线”控制指标的科学性与合理性,本文以SWAT模型为基础,通过改进子流域划分方法、添加经济社会模块和人工用水模块,对其人工侧支循环模拟进行了系统的完善,开发了基于SWAT的水量-水质-水效联合调控模型SWAT_WAQER。以广西南流江流域为例,从国民经济用水量、河道径流与水质等方面对模型进行校验,并在此基础上划分了2030年“三条红线”控制指标。结果表明:该模型性能良好,能够用于不同节水情景下的国民经济用水量、污染物排放量、水功能区水质达标结果分析,可以作为科学制定“三条红线”控制指标的有力支撑工具。 相似文献
35.
36.
Hitoshi Muta 《Journal of Nuclear Science and Technology》2019,56(5):367-368
Recent activities in the field of Nuclear Operational Management and Nuclear Safety Engineering, the studies related to risk analysis methodology, design, and operational management, physical phenomena, and emergency preparedness and nuclear security, have been progressed. Especially, ‘risk analysis methodology’ and ‘design and operational management’ are the main categories of the field, in which more than half of published articles on Journal of Nuclear Science and Technology are related to these categories. 相似文献
37.
Previous experimental results indicate that the humidification conditions at the anode have an impact on the liquid water distribution in the cathode gas diffusion layer. Numerical simulations are developed to reproduce and analyze this effect. Results consistent with the experimental results are first obtained by playing with the partition coefficients of an advanced pore network model computing the liquid water formation and transfer in the cathode gas diffusion layer (GDL) for a large range of operating conditions. Then, a model for the full anode – cathode assembly is developed by combining the pore network model of the cathode GDL and a 1D model describing the heat and water transfer in the various components of the anode-cathode assembly. This enables one to generalize the dry – wet regime diagram introduced in a previous work by incorporating the effect of the humidity condition at the anode. 相似文献
38.
以转基因水稻中最常用的CaMV35S启动子、NOS终止子、Cry1Ab/Ac基因、HPT基因及SPS水稻内标基因为研究对象,利用5 种不同的荧光信号(FAM、HEX、Taxas Red、Cy5、Cy5.5)进行多重实时聚合酶链式反应(real-time polymerase chain reaction,real-time PCR)检测方法的研究。通过引物组合筛选、反应体系优化、特异性测试、灵敏度测试、适用性测试等一系列实验,建立了5 重real-time PCR方法,灵敏度可达0.032%。此方法具有灵敏度高、结果准确、通量大等优点,可实现水稻中转基因成分的快速、高效检测。 相似文献
39.
This article theoretically and empirically analyzes backtesting portfolio value-at-risk (VaR) with estimation risk in an intrinsically multi-variate framework. It particularly takes into account the estimation of portfolio weights in forecasting portfolio VaR and its impact on backtesting. It shows that the estimation risk from estimating portfolio weights and that from estimating the multi-variate dynamic model make the existing methods in a univariate framework inapplicable. It proposes a general theory to quantify estimation risk applicable to the present problem and suggests practitioners a simple but effective way to implement valid inference to overcome the effect of estimation risk in backtesting portfolio VaR. In particular, we apply our theory to the efficient mean-variance-skewness portfolio for a multi-variate generalized autoregressive conditional heteroscedasticity model with multi-variate general hyperbolic distributed innovations. Some Monte Carlo simulations and an empirical application demonstrate the merits of our method. 相似文献
40.
WRESTORE (Watershed Restoration Using Spatio-Temporal Optimization of Resources) is a web-based, participatory planning tool that can be used to engage with watershed stakeholder communities, and involve them in using science-based, human-guided, interactive simulation–optimization methods for designing potential conservation practices on their landscape. The underlying optimization algorithms, process simulation models, and interfaces allow users to not only spatially optimize the locations and types of new conservation practices based on quantifiable goals estimated by the dynamic simulation models, but also to include their personal subjective and/or unquantifiable criteria in the location and design of these practices. In this paper, we describe the software, interfaces, and architecture of WRESTORE, provide scenarios for implementing the WRESTORE tool in a watershed community's planning process, and discuss considerations for future developments. 相似文献