全文获取类型
收费全文 | 8830篇 |
免费 | 92篇 |
专业分类
电工技术 | 71篇 |
综合类 | 1篇 |
化学工业 | 674篇 |
金属工艺 | 87篇 |
机械仪表 | 91篇 |
建筑科学 | 169篇 |
矿业工程 | 19篇 |
能源动力 | 85篇 |
轻工业 | 474篇 |
水利工程 | 53篇 |
石油天然气 | 16篇 |
无线电 | 606篇 |
一般工业技术 | 753篇 |
冶金工业 | 5117篇 |
原子能技术 | 40篇 |
自动化技术 | 666篇 |
出版年
2021年 | 43篇 |
2020年 | 32篇 |
2019年 | 65篇 |
2018年 | 69篇 |
2017年 | 50篇 |
2016年 | 51篇 |
2015年 | 42篇 |
2014年 | 69篇 |
2013年 | 213篇 |
2012年 | 120篇 |
2011年 | 174篇 |
2010年 | 127篇 |
2009年 | 123篇 |
2008年 | 179篇 |
2007年 | 178篇 |
2006年 | 163篇 |
2005年 | 144篇 |
2004年 | 122篇 |
2003年 | 110篇 |
2002年 | 112篇 |
2001年 | 117篇 |
2000年 | 97篇 |
1999年 | 198篇 |
1998年 | 1407篇 |
1997年 | 856篇 |
1996年 | 602篇 |
1995年 | 416篇 |
1994年 | 332篇 |
1993年 | 349篇 |
1992年 | 116篇 |
1991年 | 103篇 |
1990年 | 122篇 |
1989年 | 126篇 |
1988年 | 97篇 |
1987年 | 95篇 |
1986年 | 86篇 |
1985年 | 105篇 |
1984年 | 75篇 |
1983年 | 66篇 |
1982年 | 71篇 |
1981年 | 73篇 |
1980年 | 85篇 |
1979年 | 64篇 |
1978年 | 64篇 |
1977年 | 206篇 |
1976年 | 415篇 |
1975年 | 60篇 |
1974年 | 37篇 |
1973年 | 38篇 |
1972年 | 36篇 |
排序方式: 共有8922条查询结果,搜索用时 31 毫秒
41.
Cigarette smoking continues to be the single, most preventable cause of death and disability in the United States. For individuals who have cancer, continuing to smoke negatively impacts their treatment, survival, and risk for second primary tumors. This review of behavioral and pharmacological approaches to smoking cessation focuses on the recent comprehensive review of cessation interventions by the Agency for Health Care Policy and Research (AHCPR), as well as on new developments in the field. An intervention model is outlined that provides oncologists with a brief and easily implemented method of systematically treating patients who smoke. By assessing patient smoking status, advising smoking patients to quit, and proactively assisting their patients in quitting, oncologists can significantly influence patient health and fulfill their professional and ethical responsibility to address this life-threatening behavior. 相似文献
42.
JA Koutcher AA Alfieri RL Stolfi ML Devitt JR Colofiore LD Nord DS Martin 《Canadian Metallurgical Quarterly》1993,53(15):3518-3523
The combination of N-(phosphonacetyl)-L-aspartate, 6-methylmercaptopurine, and 6-aminonicotinamide has been shown to be an effective antineoplastic regimen and also to enhance the effects of other chemotherapeutic agents. The mechanism of action of this combination of drugs is not known definitively, but one possible mechanism is biochemical modulation of energy metabolism and inhibition of production of tumor ATP. Tumor-bearing mice were treated with N-(phosphonacetyl)-L-aspartate, followed 17 h later by 6-methylmercaptopurine and 6-aminonicotinamide. 31P nuclear magnetic resonance spectroscopic studies demonstrated a significant depletion of high energy phosphates at 10 h post-6-methylmercaptopurine and 6-aminonicotinamide. The addition of radiation at this time was shown to induce a significantly longer tumor growth delay and a greater number of regressions (including durable complete regressions) than either chemotherapy or radiation alone. The combination of chemotherapy and radiation was found to be supra-additive compared to the antineoplastic effects of either modality administered separately, without a measurable increase in host toxicity. 相似文献
43.
J. K. Richard Weber† Collin D. Anderson Dennis R. Merkley Paul C. Nordine† 《Journal of the American Ceramic Society》1995,78(3):577-582
Solidification of aluminum oxide from undercooled melts was investigated in containerless experiments. Specimens were levitated in a gas jet, stabilized with an acoustic positioning device, and melted with cw CO2 laser beams. Cooling curves were obtained by optical pyrometry when the laser intensity was reduced. The materials examined were high-purity Verneuil sapphire, 99.5% polycrystalline alumina, and oxide materials recovered from the effluent of an aluminum-fueled rocket motor. The degree of undercooling, the apparent temperature behavior during the thermal arrest on solidification, and the structure of the materials formed were different in argon and oxygen atmospheres. Undercooling of the sapphire and alumina materials was 360 ± 10 K in an oxygen atmosphere and approximately 450 K in argon. Melting and solidification of high-purity sapphire resulted in a dendritic and porous polycrystalline material in oxygen. Dense, larger crystals were obtained in argon. Products formed from 99.5% alumina were discolored and the cores were white, indicating impurity segregation effects. More reproducible behavior was observed for the sapphire and 99.5% alumina than for the tungstencontaminated rocket motor effluent materials. 相似文献
44.
The interaction of monovalent Fab fragments of NC10, an antiviral neuraminidase antibody, and the anti-idiotype antibody 3-2G12 has been used as a model system to demonstrate experimentally the influence of non-ideal binding effects on BIAcore binding data. Because the association rate constant for these two molecules was found to be relatively high (about 5 x 10(5) M-1 S-1), mass transfer was recognised as a potential source of error in the analysis of the interaction kinetics. By manipulation of the flow rate and the surface density of the immobilised ligand, however, the magnitude to this error was minimised. In addition, the application of site-specific immobilisation procedures was found to improve considerably the correlation of experimental binding data to the ideal 1:1 kinetic model such that the discrepancy between experimental and fitted curves was within the noise range of the instrument. Experiments performed to measure the equilibrium constant (KD) in solution resulted in a value of similar magnitude to those obtained from the ratio of the kinetic rate constants, even those measured with a heterogeneous ligand or with a significant mass transfer component. For this system, the experimental complexities introduced by covalent immobilisation did not lead to large errors in the KD values obtained using the BIAcore. 相似文献
45.
Orthopedists being more engaged in surgery are often asked about problems concerning exercise science. This article will summarize the existing basic knowledge, very close to practice, and put down the leading steps of how to build up a (therapeutical) training programme. A lab block is recommended acting on a preventive as well as on a sportive medical base. 相似文献
46.
AA Skolnick 《Canadian Metallurgical Quarterly》1993,270(11):1283-1284
47.
During the day, there are considerable variations in the climatic factors prevailing in these regions. This is especially so during the 24-hour daily cycle of the long, hot and dry summer (mid-May to midOctober). Such climatic conditions have had a considerable impact on the daily living pattern of family life in the same season, particularly in the urban areas. During the same 24-hour cycle, they have compelled the inhabitants to shift their living activities both vertically in section and horizontally in plan; they do this in pursuit of more acceptable, if not, desirable internal thermal environmental ambience. 相似文献
48.
The MSMIE protocol [SBC89] allows processors in a distributed system to communicate via shared memory. It was designed to meet the reliability and efficiency needs of applications such as nuclear safety systems. We present a formal model of the MSMIE protocol expressed in the notation CCS. Desirable properties of the protocol are expressed in the modal mu-calculus, an expressive modal logic. We show that the protocol lacks an important liveness property. In actual operation, additional operating constraints are checked to avoid potential problems. We present a modified protocol and show that it possesses the liveness property even without checking operating constraints. We also show how parts of the analysis were automated with the Concurrency Workbench. 相似文献
49.
Two hundred thirty-three newly enrolled medical and nursing students at the American University of Beirut, Lebanon, were tested for antibodies to measles and mumps. Antibodies to measles were detected in 95% of the sample, and antibodies to mumps in 84% of the sample. Susceptible individuals were appropriately immunized. 相似文献
50.
In 3 experiments, participants memorized 8 examples, each exemplifying a different rule. Participants were asked to extend these rules to new examples. They practiced applications of the rules to examples over a period of 4 days (Experiment 1) or 5 days (Experiments 2 and 3). Although these rules were bidirectional, an asymmetry gradually built up such that participants became more facile in using the rules in the practiced direction. Participants also showed an advantage when the initial study example was repeated or when test examples were repeated. It is argued that skill acquisition involves development of a complex set of strategies based on use of rules and retrieval of examples. Four overlapping stages of skill acquisition are described. 相似文献