全文获取类型
收费全文 | 44947篇 |
免费 | 4559篇 |
国内免费 | 2615篇 |
专业分类
电工技术 | 3273篇 |
技术理论 | 1篇 |
综合类 | 3796篇 |
化学工业 | 5942篇 |
金属工艺 | 2545篇 |
机械仪表 | 3217篇 |
建筑科学 | 3933篇 |
矿业工程 | 1359篇 |
能源动力 | 1270篇 |
轻工业 | 3887篇 |
水利工程 | 1015篇 |
石油天然气 | 1839篇 |
武器工业 | 563篇 |
无线电 | 5551篇 |
一般工业技术 | 4083篇 |
冶金工业 | 2241篇 |
原子能技术 | 562篇 |
自动化技术 | 7044篇 |
出版年
2024年 | 130篇 |
2023年 | 637篇 |
2022年 | 1363篇 |
2021年 | 2021篇 |
2020年 | 1539篇 |
2019年 | 1124篇 |
2018年 | 1293篇 |
2017年 | 1416篇 |
2016年 | 1213篇 |
2015年 | 2001篇 |
2014年 | 2651篇 |
2013年 | 3051篇 |
2012年 | 3777篇 |
2011年 | 3999篇 |
2010年 | 3729篇 |
2009年 | 3453篇 |
2008年 | 3309篇 |
2007年 | 3050篇 |
2006年 | 2498篇 |
2005年 | 1832篇 |
2004年 | 1319篇 |
2003年 | 1187篇 |
2002年 | 1191篇 |
2001年 | 1019篇 |
2000年 | 693篇 |
1999年 | 529篇 |
1998年 | 486篇 |
1997年 | 354篇 |
1996年 | 276篇 |
1995年 | 217篇 |
1994年 | 154篇 |
1993年 | 151篇 |
1992年 | 86篇 |
1991年 | 41篇 |
1990年 | 41篇 |
1989年 | 39篇 |
1988年 | 37篇 |
1987年 | 18篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 33篇 |
1976年 | 74篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
101.
Because a so-called mandibular whiplash injury requires the absence of short-latency jaw-closing reflexes in order to explain the postulated mechanism of injury (excessive jaw opening); the authors studied the presence and absence and more importantly, the kinematics (duration, displacement, velocity, acceleration) of monosynaptic and possibly, polysynaptic myotatic (stretch) reflexes in the jaw elevator muscles. In six healthy adults jaw jerk maneuvers were elicited through a brisk tap on the chin, and surface electromyography identified elevator reflexes while translational electrognathography identified the kinematics of the reflexes. The maneuvers were done while maintaining the rest position (3% MVC) and moderate clenching of the teeth (30% MVC). Electromyography was also used to identify phasic elevator excitations during a passive brisk neck extension maneuver. A sudden and unexpected elongation of the jaw elevators released autogenic reflex responses that, in conjunction with augmented tissue elasticity (stiffness), elevated the mandible into centric occlusion within approximately 150 milliseconds. In 86% of trials, the responses occurred regardless of the prevailing resting and clenching contractile activities. There was no evidence of a depressor force that consistently would and could anchor the mandible in a position of extreme or moderate depression, the theoretical linchpin of the mandibular whiplash injury. It was concluded that the mandibular locomotor system is very efficient in maintaining the rest and intercuspal positions of the mandible. This study found no evidence corroborating the mechanism claimed to release a so-called mandibular whiplash injury. 相似文献
102.
SV Varha OH Reznikov IS Turchyn VM Demchenko OP Potikha PV Sinitsyn LV Tarasenko LV Cha?kovs'ka 《Canadian Metallurgical Quarterly》1994,40(5-6):105-109
The effect exerted by transplantation of the 5 day culture of testicles from newly born piglets on the hypogonadal state of mature X-ray irradiated (3 Gy) rats was studied. It has been found that a month after transplantation (two months after irradiation) the hypogonadal state disappeared for a while, which is confirmed by normalization of the weight of seminal vesicles, content of testosterone and biologically active lutropine, restoration of the reproductive function of rats. No significant changes in steroidogenesis activity have been found, which proves a substituent character of transplantation. The effect disappears three months later but certain restoration of the content of nucleic acids in the testicles is observed. 相似文献
103.
104.
LV Osadchuk 《Canadian Metallurgical Quarterly》1997,33(11):1534-1538
The level of cortisol in serum and adrenals and its production by adrenals in vitro was studied by the radioimmune method in male and female silver fox embryos, starting from day 30 of pregnancy every five days. Pregnant females from a commercial population and an experimental population, which had been selected for domestic behavior, was used. It was shown that, at the end of the prenatal developmental stage, all investigated parameters of the glucocorticoid function of adrenals were significantly lower in embryos from selected mothers as compared to the unselected control group. The addition of adrenocorticotropic hormone into the incubation medium increased cortisol biosynthesis at all embryogenesis stages, but in the selected population the increase was less than that in the control group. 相似文献
105.
A rapid, multiresidue solid-phase extraction (SPE) technique for determination of organochlorine pesticide and polychlorinated biphenyl (PCB) residues in nonfatty fish was modified for use with fatty fish. In the modified procedures, samples are extracted with acetonitrile, and the extract is cleaned up with both C18 and Florisil SPE columns. Residues are determined by gas chromatography with electron capture detection. The original method was modified for use with fatty fish by reducing the amount of tissue extracted and by using an improved Florisil SPE cleanup. Recovery data are presented for 24 fortified organochlorine pesticide residues (0.12 ppm) and 3 fortified PCB residues (0.80 ppm) from flounder, bluefish, and shad samples, which contained 0.8, 5.4, and 22.6% fat, respectively. For the 3 types of fish, recoveries of 23 of 24 fortified organochlorine pesticide residues ranged from 55 to 129%, and recoveries of 3 fortified PCB residues ranged from 55 to 104%. There were no significant differences in recovery based on fish species and/or fat content for the majority of residues studied. This SPE method and the official AOAC method yielded comparable results for fish containing incurred organochlorine residues. 相似文献
106.
分析了OSI参考模型和B-ISDN协议参考模型之间的关系,为B-ISDN与以OSI为标准的数据网的互联打下了基础。 相似文献
107.
本文首先简述D>0.06mm泥沙的粒析沉降特性及其粒径偏粗的原因。继之对悬沙中粒径大于0.06mm的粒析级配组成机理,及级配组成不同对标准粒径Db与粒析粒径DL关系的影响进行了详细研究。在以上研究工作的基础上,开展了Db与DL的比较试验,得出了粗、中、细型悬沙的Db~DL关系和对DL的改正方法。 相似文献
108.
本文针对金翅岭金矿矿体开采条件极其复杂的情况,在采矿方法试验中,率先在岩金矿山采用了三强作业技术,既保证了安全回采,又取是了较好的技术经济指标。 相似文献
109.
110.
1MotivationsIncreasingdensityofVLSIchipsmakesthecostoftestingveryexpensive.Designfortestabilitycantemperthisproblemdrastically.Therearetwokindsofsolutions:(i)localsolutionl3'2]withlowcomputingcomplexity,whichcannotalwaysgetsatisfactoryresults;(ii)globa.lsolutionwithprohibitivecomputingcomplekityl1'5].T.H.Chen'andM.A.Breuer[1lpresentedanILPmodeltoplacetestpointsglobally.Becauseofitscomputingcomplealty,[1lcanonlydealwithsmallormediumscalecircuits.SCOAPisusedin[1],whichisnotaveryaccuratet… 相似文献