全文获取类型
收费全文 | 4349篇 |
免费 | 109篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 18篇 |
综合类 | 3篇 |
化学工业 | 460篇 |
金属工艺 | 41篇 |
机械仪表 | 46篇 |
建筑科学 | 46篇 |
矿业工程 | 4篇 |
能源动力 | 58篇 |
轻工业 | 371篇 |
水利工程 | 12篇 |
石油天然气 | 5篇 |
无线电 | 157篇 |
一般工业技术 | 298篇 |
冶金工业 | 2641篇 |
原子能技术 | 14篇 |
自动化技术 | 287篇 |
出版年
2023年 | 16篇 |
2022年 | 40篇 |
2021年 | 59篇 |
2020年 | 42篇 |
2019年 | 31篇 |
2018年 | 60篇 |
2017年 | 64篇 |
2016年 | 74篇 |
2015年 | 55篇 |
2014年 | 74篇 |
2013年 | 131篇 |
2012年 | 120篇 |
2011年 | 117篇 |
2010年 | 93篇 |
2009年 | 87篇 |
2008年 | 100篇 |
2007年 | 85篇 |
2006年 | 78篇 |
2005年 | 45篇 |
2004年 | 39篇 |
2003年 | 67篇 |
2002年 | 53篇 |
2001年 | 34篇 |
2000年 | 30篇 |
1999年 | 104篇 |
1998年 | 872篇 |
1997年 | 462篇 |
1996年 | 316篇 |
1995年 | 187篇 |
1994年 | 137篇 |
1993年 | 200篇 |
1992年 | 44篇 |
1991年 | 34篇 |
1990年 | 47篇 |
1989年 | 33篇 |
1988年 | 40篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1985年 | 35篇 |
1983年 | 9篇 |
1982年 | 16篇 |
1981年 | 20篇 |
1980年 | 35篇 |
1979年 | 5篇 |
1978年 | 12篇 |
1977年 | 56篇 |
1976年 | 112篇 |
1973年 | 5篇 |
1966年 | 4篇 |
1955年 | 3篇 |
排序方式: 共有4461条查询结果,搜索用时 15 毫秒
1.
Rosana Fatima Galindo Luis Antonio Barbosa Cortez Telma Teixeira Franco 《化学工程与技术》2020,43(8):1530-1537
An alternative for reducing emissions from marine fuel is to blend bio-oil from lignocellulose non-edible feedstocks to diesel fossil fuels. Phase diagrams of the ternary systems were built to represent the transition from heterogeneous regions to homogeneous regions. Four homogeneous blends of bio-oil of eucalyptus-bioethanol-marine gasoil were experimentally characterized with respect to the most important fuel parameters for marine engines: water content, flash point, low heating value, viscosity, and acidity. Blends with closer properties to marine gasoil replacement, lower costs, and environmental impacts should be tested for large engines. 相似文献
2.
The rapid development of the science and technology of organic semiconductors has already led to mass application of organic light‐emitting diodes (OLEDs) in television monitors of outstanding quality as well as in a large variety of smaller displays found in smartphones, tablets, and other gadgets, while introduction of the technology to the illumination sector is imminent. Notably, the requirements of all such applications for emission in the visible range of the electromagnetic spectrum are well tuned to the optical and electronic properties of typical organic semiconductors, thereby representing relatively “low‐hanging fruits,” in terms of material development and exploitation. However, the question arises as to whether developing materials suited for efficient near‐infrared (NIR, 700–1000 nm) emission is possible, and, crucially, desirable to enable new classes of applications spanning from through‐space, short‐range communications to biomedical sensors, night vision, and more generally security applications to name but a few. Here, the major fundamental hurdles to be overcome to achieve efficient NIR emission from organic π‐conjugated systems are discussed, recent progress is reviewed, and an outlook for further development of both materials and applications is provided. 相似文献
3.
4.
Franco Cataldo 《Fullerenes, Nanotubes and Carbon Nanostructures》2004,12(4):765-779
The polyynes produced by the electric arc between graphite electrodes submerged in hexane are readily reduced to a mixture of polyenes and ene-ynes by a treatment with Zn dust and hydrochloric acid. Experimental evidences of this reduction reaction are presented by electronic absorption spectroscopy, FT-IR spectroscopy, and HPLC analysis with diode-array detector. Some consequences of this simple passage from polyynes to ene-ynes are briefly discussed in a biochemical context. 相似文献
5.
The aim of this study was to assess the association between the length of maternity leave and the quality of mother-infant interactions; 198 employed mothers of 4-month-old infants were interviewed and videotaped in their homes during a feeding time. Hierarchical multiple regression analyses indicated a direct association between shorter length of leave and more negative affect and behavior in maternal interactions with their infants. Infant and mother stressor/protective variables added significantly in predicting the quality of the mother-infant relationship. There were also significant interaction effects between the length of leave and these variables. Mothers who either reported more depressive symptoms or who perceived their infant as having a more difficult temperament and who had shorter leaves, compared with mothers who had longer leaves, were observed to express less positive affect, sensitivity, and responsiveness in interactions with their infants. The public policy implications of the relation between length of maternity leave, maternal and infant individual differences, and the quality of mother-infant interactions are discussed. 相似文献
6.
MH Hennington AM D'Armini JJ Lemasters TM Egan 《Canadian Metallurgical Quarterly》1996,61(7):1009-1014
In an effort to increase the donor pool for lung transplantation (LTX), we have demonstrated the feasibility of LTX from circulation-arrested cadavers in a canine LTX model. We hypothesized that ventilation of the cadaver lung with alveolar gas (20% O2, 5% CO2, balance N2) (AG) would be superior to ventilation with 100% oxygen (O2) after circulatory arrest of the donor. Twelve mongrel dogs were intubated, heparinized and euthanized by pentothal injection and ventilated with AG (n=6) or O2 (n=6). Four hours later, donor animals underwent sternotomy, and the lungs were flushed with cold modified Euro-Collins solution, harvested, and stored inflated in ice slush. Left lung allotransplantation was performed, and recipients were made dependent o n the transplanted lung by occlusion of the contralateral bronchus and pulmonary artery. Recipient animals were ventilated with an FiO2 of 0.4 and followed for 8 hr. Total ischemic time was 7.9 hr for both groups. Pulmonary edema developed in all recipients of AG lungs; one recipient survived the 8-hr observation period with poor oxygenation. In contrast, three of six recipients of O2-ventilated lungs survived for 8-hr with excellent gas exchange. Specimens of donor lungs before and after transplant were evaluated histologically utilizing trypan blue exclusion as an indicator of cell viability. At the time of organ retrieval 4 hr after death, 6% of cells were nonviable in the O2-ventilated cadaver lungs. Circulation-arrested cadaver lungs ventilated with 100% O2 prior to organ retrieval have superior pulmonary function after transplant compared with lungs ventilated with AG. Ventilation of cadaver lungs with AG induces pulmonary injury in this model. retrieval of donor lungs from circulation-arrested cadavers has potential for increasing the pulmonary donor pool. 相似文献
7.
The Department of Veterans Affairs, Social Work Service has designed, developed and implemented the Social Work Information Management System (SWIMS) which provides for the collection and reporting of both administrative and clinical information. This paper describes the implementation of one component of SWIMS, the automated Social Work Data Base/Assessment. The discussion details the implementation process and discusses issues encountered in the implementation of a computerized documentation system. 相似文献
8.
OBJECTIVE: The aim of this study was to demonstrate the MR characteristics of non-Hodgkin lymphoma of the skull base to help in the differential diagnosis of this neoplasm from other conditions. MATERIALS AND METHODS: MR of five patients, 7-64 years old, with pathologically proved lymphomas of the skull base were reviewed. Three cases had primary skull base lesions involving the sphenoid bone and the cavernous sinus. One case with a nasal cavity lesion involving the skull base and one with a relapsing skull base lesion of previously treated tonsillar lymphoma were included. RESULTS: The lesions had signal intensities that were similar to that of gray matter of brain on both T1- and T2-weighted imaging. Bilateral cavernous sinuses were involved with encasement of internal carotid arteries in every case. Postcontrast MR showed homogeneous enhancement of the tumor with dural infiltration along the planum sphenoidale, clivus, or tentorium. The clivus was destroyed or replaced by tumors in adult cases but in two children the clivus was preserved with intact sphenooccipital synchondrosis. In one case the tumor extended to the extracranial portion through the jugular foramen. CONCLUSION: The MR findings of a permeative lesion of the skull base, invasion of the cavernous sinus without arterial narrowing, infiltration along the dural surface, and an iso- or hypointensity with brain on T2-weighted imaging should suggest lymphoma. 相似文献
9.
10.
V. Anjos M.J.V. Bell E.F. da Silva Jr. R.W.A. Franco I.A. Esquef 《Microelectronics Journal》2005,36(11):977-980
In this paper we report the use of photothermal techniques such as Thermal lens (TL) spectrometry, Photoacoustic and heat capacity, ρcp, to determine the thermo-optical parameters, such as thermal conductivity (K), thermal diffusivity (D), specific heat (cp) and the optical path dependence with temperature (ds/dT), of an undoped polycrystalline 3C-SiC. To our knowledge, this is the first time that Thermal lens technique is used for wide band-gap systems. Results obtained for the polycrystalline sample with TL technique indicates that ds/dT is negative at room temperature. Moreover, the obtained values of thermal diffusivity and thermal conductivity are in good agreement with that found in the literature, indicating that the phototermal techniques can be used to obtain the referred parameters in circumstances where other techniques cannot be used, for example, in harsh environments. 相似文献