全文获取类型
收费全文 | 241242篇 |
免费 | 2626篇 |
国内免费 | 427篇 |
专业分类
电工技术 | 4292篇 |
综合类 | 257篇 |
化学工业 | 39369篇 |
金属工艺 | 9379篇 |
机械仪表 | 7394篇 |
建筑科学 | 5446篇 |
矿业工程 | 1391篇 |
能源动力 | 5152篇 |
轻工业 | 24808篇 |
水利工程 | 2476篇 |
石油天然气 | 5092篇 |
武器工业 | 32篇 |
无线电 | 25044篇 |
一般工业技术 | 44770篇 |
冶金工业 | 45344篇 |
原子能技术 | 5950篇 |
自动化技术 | 18099篇 |
出版年
2021年 | 2107篇 |
2019年 | 2017篇 |
2018年 | 3488篇 |
2017年 | 3424篇 |
2016年 | 3687篇 |
2015年 | 2235篇 |
2014年 | 3898篇 |
2013年 | 10184篇 |
2012年 | 6146篇 |
2011年 | 8297篇 |
2010年 | 6546篇 |
2009年 | 7232篇 |
2008年 | 7583篇 |
2007年 | 7712篇 |
2006年 | 6887篇 |
2005年 | 6045篇 |
2004年 | 5815篇 |
2003年 | 5598篇 |
2002年 | 5673篇 |
2001年 | 5560篇 |
2000年 | 5383篇 |
1999年 | 5302篇 |
1998年 | 12571篇 |
1997年 | 8895篇 |
1996年 | 6856篇 |
1995年 | 5329篇 |
1994年 | 4735篇 |
1993年 | 4624篇 |
1992年 | 3667篇 |
1991年 | 3387篇 |
1990年 | 3593篇 |
1989年 | 3472篇 |
1988年 | 3303篇 |
1987年 | 2895篇 |
1986年 | 2932篇 |
1985年 | 3373篇 |
1984年 | 3219篇 |
1983年 | 2892篇 |
1982年 | 2738篇 |
1981年 | 2821篇 |
1980年 | 2719篇 |
1979年 | 2624篇 |
1978年 | 2684篇 |
1977年 | 2948篇 |
1976年 | 3805篇 |
1975年 | 2368篇 |
1974年 | 2242篇 |
1973年 | 2376篇 |
1972年 | 1970篇 |
1971年 | 1858篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
982.
983.
Is homophobia associated with homosexual arousal? 总被引:1,自引:0,他引:1
The authors investigated the role of homosexual arousal in exclusively heterosexual men who admitted negative affect toward homosexual individuals. Participants consisted of a group of homophobic men (n?=?35 ) and a group of nonhomophobic men (n?=?29); they were assigned to groups on the basis of their scores on the Index of Homophobia (W. W. Hudson & W. A. Ricketts, 1980). The men were exposed to sexually explicit erotic stimuli consisting of heterosexual, male homosexual, and lesbian videotapes, and changes in penile circumference were monitored. They also completed an Aggression Questionnaire (A. H. Buss & M. Perry, 1992). Both groups exhibited increases in penile circumference to the heterosexual and female homosexual videos. Only the homophobic men showed an increase in penile erection to male homosexual stimuli. The groups did not differ in aggression. Homophobia is apparently associated with homosexual arousal that the homophobic individual is either unaware of or denies. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
984.
F Sopracordevole E Campagnutta A Parin C Scarabelli 《Canadian Metallurgical Quarterly》1994,46(3):69-73
The authors report their experience of the use of a vital stain--methylene blue--as a surgical guide in laser cervical conization for CIN2-CIN3/CIS. During the period 1 October 1991-31 December 1992 a total of 40 laser cervical conizations were performed under local anesthesia using a CO2 laser connected to a microhandpiece and colposcope in patients with exo-endocervical lesions which were histologically positive for CIN2-CIN3/CIS. In 33/40 patients an aqueous solution of 1% methylene blue was introduced preoperatively in the endocervix using a cotton-wool bud with consequent impregnation of the pseudoglandular crypts: laser biopsy was performed along the guidelines of the stain itself. This enabled the direction of resection to be varied: in 3 patients due to an anomalous and eccentric direction of cervical canal; in 10 patients to remove glandular structures surrounding or underneath lesions; in 8 patients following pseudoglandular section to carry out deep vaporization (3 patients) or correct cutting edges (5 patients). The apex and edges of the cone were always intact. Fourteen patients completed a 12-month follow-up and a further 6 were followed up for 9 months; only 1/14 patients (with AIDS) showed recidivation after 1 year. In the authors' experience the use of a vital stain as a guide during laser cervical cone biopsy is an easily used method which ensures the greatest possible respect for healthy cervical structures, also in order to preserve fertility in young patients. 相似文献
985.
This paper describes a database model based on the original rough sets theory. Its rough relations permit the representation of a rough set of tuples not definable in terms of the elementary classes, except through use of lower and upper approximations. The rough relational database model also incorporates indiscernibility in the representation and in all the operators of the rough relational algebra. This indiscernibility is based strictly on equivalence classes which must be defined for every attribute domain. There are several obvious applications for which the rough relational database model can more accurately model an enterprise than does the standard relational model. These include systems involving ambiguous, imprecise, or uncertain data. Retrieval over mismatched domains caused by the merging of one or more applications can be facilitated by the use of indiscernibility, and naive system users can achieve greater recall with the rough relational database. In addition, applications inherently “rough” could be more easily implemented and maintained in the rough relational database. 相似文献
986.
Mikhaylov I. E. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2021,55(4):540-548
Power Technology and Engineering - This article describes a new method for calculating settlers for irrigation systems. The proposed method is based on the results of experimental research and... 相似文献
987.
A. N. Cherepanov V. V. Marchenkov V. E. Startsev N. V. Volkenshtein M. Glin'skii 《Journal of Low Temperature Physics》1990,80(3-4):135-151
The field and temperature dependence of the transverse magnetoresistivity and the Hall coefficient for single-crystal tungsten with a resistivity ratio 293K/4.2K varying from 780 to 80800 are measured at temperatures between 4.2 K and 50 K in magnetic fields up to 150 kOe. The role of the static skin effect and the temperature breakdown in the galvanomagnetic properties of the compensated metals is evaluated through experiments with tungsten. The experimental data shows that the galvanomagnetic properties of the compensated metals in the high magnetic fields are not dependent only on the Fermi surface geometry. A substantial role in their formation is played by the processes of the electron-surface and the intersheet electron-phonon scatterings. 相似文献
988.
989.
Yu. Yu. Belous A. G. Kostornov Yu. M. Efimenko L. E. Lunin A. M. Volkhov 《Powder Metallurgy and Metal Ceramics》1990,29(1):71-73
Conclusions Permeable materials based on metallic fibers with porous layers sprayed on by the detonation gas method, in tangential filtering of media with ferromagnetic and abrasive impurities ensure fineness of cleaning 1–2 m with comparatively low hydraulic resistance. The application of a magnetic field to material with sprayed-on layer of magnetic alloy made it possible to increase permeability to ferromagnetic particles by a factor of more than 1.5.Translated from Poroshkovaya Metallurgiya, No. 1(325), pp. 77–80, January, 1990. 相似文献
990.
H. O. Menlove M. M. Fowler E. Garcia M. C. Miller M. A. Paciotti R. R. Ryan S. E. Jones 《Journal of Fusion Energy》1990,9(4):495-506
Experiments using high-efficiency neutron detectors have detected neutron emission from various forms of Pd and Ti metal in pressurized D2 gas cells and D2O electrolysis cells. Four independent neutron detectors based on3He gas tubes were used. Both random neutrons (0.05–0.2 n/s) and time-correlated neutron bursts (10–280 n) of 100-s duration were measured using time-correlation counting techniques. The majority of the neutron burst events occurred at –30°C as the samples were warming up from the liquid nitrogen temperature. 相似文献