全文获取类型
收费全文 | 9729篇 |
免费 | 456篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 97篇 |
综合类 | 4篇 |
化学工业 | 1999篇 |
金属工艺 | 142篇 |
机械仪表 | 188篇 |
建筑科学 | 616篇 |
矿业工程 | 21篇 |
能源动力 | 321篇 |
轻工业 | 854篇 |
水利工程 | 110篇 |
石油天然气 | 28篇 |
无线电 | 729篇 |
一般工业技术 | 1969篇 |
冶金工业 | 1287篇 |
原子能技术 | 42篇 |
自动化技术 | 1798篇 |
出版年
2023年 | 70篇 |
2022年 | 137篇 |
2021年 | 216篇 |
2020年 | 177篇 |
2019年 | 212篇 |
2018年 | 235篇 |
2017年 | 234篇 |
2016年 | 258篇 |
2015年 | 228篇 |
2014年 | 337篇 |
2013年 | 666篇 |
2012年 | 559篇 |
2011年 | 794篇 |
2010年 | 506篇 |
2009年 | 480篇 |
2008年 | 600篇 |
2007年 | 519篇 |
2006年 | 441篇 |
2005年 | 389篇 |
2004年 | 333篇 |
2003年 | 308篇 |
2002年 | 285篇 |
2001年 | 149篇 |
2000年 | 161篇 |
1999年 | 139篇 |
1998年 | 146篇 |
1997年 | 155篇 |
1996年 | 139篇 |
1995年 | 115篇 |
1994年 | 93篇 |
1993年 | 95篇 |
1992年 | 84篇 |
1991年 | 69篇 |
1990年 | 79篇 |
1989年 | 64篇 |
1988年 | 44篇 |
1987年 | 63篇 |
1986年 | 52篇 |
1985年 | 57篇 |
1984年 | 52篇 |
1983年 | 67篇 |
1982年 | 49篇 |
1981年 | 41篇 |
1980年 | 36篇 |
1979年 | 38篇 |
1978年 | 29篇 |
1977年 | 27篇 |
1976年 | 28篇 |
1975年 | 22篇 |
1974年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Krauss Jurgen; Arndt Michaela A.E.; Martin Andrew C.R.; Liu Huaitian; Rybak Susanna M. 《Protein engineering, design & selection : PEDS》2003,16(10):753-759
A prerequisite for the enrichment of antibodies screened fromphage display libraries is their stable expression on a phageduring multiple selection rounds. Thus, if stringent panningprocedures are employed, selection is simultaneously drivenby antigen affinity, stability and solubility. To take advantageof robust pre-selected scaffolds of such molecules, we graftedsingle-chain Fv (scFv) antibodies, previously isolated froma human phage display library after multiple rounds of in vitropanning on tumor cells, with the specificity of the clinicallyestablished murine monoclonal anti-CD22 antibody RFB4. We showthat a panel of grafted scFvs retained the specificity of themurine monoclonal antibody, bound to the target antigen withhigh affinity (6.49.6 nM), and exhibited exceptionalbiophysical stability with retention of 8993% of theinitial binding activity after 6 days of incubation in humanserum at 37°C. Selection of stable human scaffolds withhigh sequence identity to both the human germline and the rodentframeworks required only a small number of murine residues tobe retained within the human frameworks in order to maintainthe structural integrity of the antigen binding site. We expectthis approach may be applicable for the rapid generation ofhighly stable humanized antibodies with low immunogenic potential. Received June 10, 2003; accepted August 27, 2003. 相似文献
992.
Andrew Hargreaves 《Journal of Housing and the Built Environment》2004,19(1):49-65
Familiar social concepts such ascommunity, home and family are increasinglyredefined in terms of process in contrast to`place', which is often viewed as a ratherinert spatial designation. Definitions ofcommunity do not always coincide with locationbut a lack of distinctive features or socialfocus in many residential housing areas promptsthe question of whether the separation between`place' and `interest' could lead to a more orless sustainable condition for humansettlement.Based on data collected from an ethnographicstudy in Northeast Scotland, this analysis aimsto explore the continuities between `place' and`interest' in constructing a more satisfyingenvironment for housing development.Communities with an awareness of place exhibithabitual patterns of movement around familiarand significant objects in the construction ofboth individual and social identity and memory.Increased identification produces a morepositive `sense of place' as an inherent aspectof what is termed `social sustainability'. This paper argues that a more sustainable sitefor residential development emerges at thecoincidence of movement and socialsignificance.Qualitative improvements to the builtenvironment need to take account of existinglocal distinctiveness and the patterns ofmovement that communicate their significanceand sense of identity. It is argued that agreater awareness of these key social factorsin urban planning would facilitate greaterpotential `social sustainability' inresidential environments. Some of the differentoptions for the design and layout ofresidential areas are considered in relation tothe research findings. 相似文献
993.
Leventhal Adam M.; Waters Andrew J.; Boyd Susan; Moolchan Eric T.; Lerman Caryn; Pickworth Wallace B. 《Canadian Metallurgical Quarterly》2007,15(1):21
Gender differences in tobacco withdrawal are of considerable clinical importance, but research findings on this topic have been mixed. Methodological variation in samples sizes, experimental design, and measures across studies may explain the inconsistent results. The current study examined whether male (n = 101) and female (n = 102) smokers (≥15 cigarettes/day) differed in abstinence-induced changes on a battery of self-report measures (withdrawal, affect, craving), cognitive performance tasks (attention, psychomotor performance), and physiological responses (heart rate, blood pressure, brain electroencephalogram). Participants attended 2 counterbalanced laboratory sessions, 1 following 12 hr of abstinence and the other following ad libitum smoking. Results showed that women reported greater abstinence-induced increases in negative affect, withdrawal-related distress, and urge to smoke to relieve withdrawal distress. In contrast, both genders reported similar abstinence-induced changes in positive affect and urge to smoke for pleasure. Men and women exhibited generally similar abstinence-induced changes in physiological and cognitive performance measures. In addition, gender did not moderate the association between withdrawal symptoms and baseline measures of smoking behavior and dependence. Abstinence-induced changes in withdrawal distress mediated the effect of gender on latency until the 1st cigarette of the day at trend levels ( p 相似文献
994.
995.
Blumenthal James A.; Sherwood Andrew; Gullette Elizabeth C. D.; Georgiades Anastasia; Tweedy Damon 《Canadian Metallurgical Quarterly》2002,70(3):569
Despite recent advances in the medical management of hypertension, chronically elevated blood pressure remains a major health problem in the United States, affecting almost 50 million Americans. It is widely recognized that lifestyle factors contribute to the development and maintenance of elevated blood pressure. This article critically reviews current approaches to the nonpharmacological treatment of high blood pressure and highlights outcome studies of exercise, weight loss and dietary modification, and stress management and relaxation therapies. Methodological issues in the assessment and treatment of hypertension are discussed, along with possible mechanisms by which lifestyle modification may reduce elevated blood pressure. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
996.
Steenbergh Timothy A.; Meyers Andrew W.; May Ryan K.; Whelan James P. 《Canadian Metallurgical Quarterly》2002,16(2):143
The Gamblers' Beliefs Questionnaire (GBQ) is a self-report measure of gamblers' cognitive distortions. GBQ test items were constructed on the basis of theory, empirical evidence, and expert review. Four hundred three adults completed the initial set of items, and 21 items werr selected to make up the final GBQ. The factor structure of the GBQ consisted of 2 closely related factors: Luck/Perseverance and Illusion of Control. The full scale showed good internal consistency (α?=?.92) and adequate test-retest reliability (r?=?.77). Problem and pathological gamblers scored higher than nonproblem gamblers on the GBQ and its factors. GBQ scores were moderately correlated with the duration of gambling sessions among problem and pathological gamblers, and there was no relationship between GBQ scores and social desirability. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
997.
Gerald J Smith Ian J Miller Vincent Daniels Andrew J Smith 《Coloration Technology》1997,113(4):124-126
The possible stimulus to the dye industry in antiquity provided by the breeding of sheep with a white fleece is linked to the development of a colour vocabulary apparent in ancient texts. 相似文献
998.
Jeff T. M. De Hosson Wouter A. Soer Andrew M. Minor Zhiwei Shan Eric A. Stach S. A. Syed Asif Oden L. Warren 《Journal of Materials Science》2006,41(23):7704-7719
As a tribute to the scientific work of Professor David Brandon, this paper delineates the possibilities of utilizing in situ transmission electron microscopy to unravel dislocation-grain boundary interactions. In particular, we have focused on the deformation characteristics of Al–Mg films. To this end, in situ nanoindentation experiments have been conducted in TEM on ultrafine-grained Al and Al–Mg films with varying Mg contents. The observed propagation of dislocations is markedly different between Al and Al–Mg films, i.e. the presence of solute Mg results in solute drag, evidenced by a jerky-type dislocation motion with a mean jump distance that compares well to earlier theoretical and experimental results. It is proposed that this solute drag accounts for the difference between the load-controlled indentation responses of Al and Al–Mg alloys. In contrast to Al–Mg alloys, several yield excursions are observed during initial indentation of pure Al, which are commonly attributed to the collective motion of dislocations nucleated under the indenter. Displacement-controlled indentation does not result in a qualitative difference between Al and Al–Mg, which can be explained by the specific feedback characteristics providing a more sensitive detection of plastic instabilities and allowing the natural process of load relaxation to occur. The in situ indentation measurements confirm grain boundary motion as an important deformation mechanism in ultrafine-grained Al when it is subjected to a highly inhomogeneous stress field as produced by a Berkovich indenter. It is found that solute Mg effectively pins high-angle grain boundaries during such deformation. The mobility of low-angle boundaries is not affected by the presence of Mg.Special title: Advanced Materials and Characterization: Proceedings of the Brandon Symposium; Guest Editors: Wayne D. Kaplan and Srinivasa Ranganathan 相似文献
999.
The effects of methacrylic acid (MAA) on the physical properties of polymer made by emulsion copolymerization of butyl acrylate (BA) and MAA were examined. Emulsion polymerizations were performed with and without MAA and at temperatures of 0.1 and 50 °C, using redox initiation so that the radical flux was essentially independent of temperature. The presence of methacrylic acid had only a small effect on gel fraction and on molecular weight, but a profound effect on the film properties; changing the synthesis temperature was found to slightly alter the properties of the copolymer films. Latexes containing MAA formed much stronger films (from creep tests), and significantly increased tack and peel adhesion. This was attributed to intermolecular dipole-dipole interactions of the acid groups. Conductometric titration measurements revealed that the acid groups were predominantly located inside the latex particles, with only a small proportion in the aqueous phase and on the particle surface. Temperature was found not to affect significantly the partitioning of the acid groups in the latex. 相似文献
1000.
Hardy David J.; Hinkin Charles H.; Levine Andrew J.; Castellon Steven A.; Lam Mona N. 《Canadian Metallurgical Quarterly》2006,20(3):355
Decision making was assessed using a laboratory gambling task in 67 adults with the Human Immunodeficiency Virus (HIV+) and in 19 HIV-seronegative (HIV-) control participants. Neurocognitive test performance across several domains was also analyzed to examine potential cognitive mechanisms of gambling task performance. As predicted, the HIV+ group performed worse on the gambling task, indicating greater risky decision making. Specifically, the HIV+ group selected more cards from the "risky" or disadvantageous deck that included relatively large payoffs but infrequent large penalties. The control group also selected such risky cards but quickly learned to avoid them. Exploratory analyses also indicated that in the HIV+ group, but not in the control group, gambling task performance was correlated with Stroop Interference performance and long delay free recall on the California Verbal Learning Test, suggesting the role of inhibitory processes and verbal memory in the poorer gambling task performance in HIV. These findings indicate the usefulness of the gambling task as a laboratory tool to examine risky decision making and cognition in the HIV population. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献