全文获取类型
收费全文 | 197789篇 |
免费 | 2114篇 |
国内免费 | 632篇 |
专业分类
电工技术 | 4060篇 |
综合类 | 123篇 |
化学工业 | 26696篇 |
金属工艺 | 7507篇 |
机械仪表 | 5460篇 |
建筑科学 | 4037篇 |
矿业工程 | 747篇 |
能源动力 | 4657篇 |
轻工业 | 14383篇 |
水利工程 | 1695篇 |
石油天然气 | 2842篇 |
武器工业 | 7篇 |
无线电 | 27290篇 |
一般工业技术 | 37383篇 |
冶金工业 | 45380篇 |
原子能技术 | 3560篇 |
自动化技术 | 14708篇 |
出版年
2021年 | 1244篇 |
2019年 | 1280篇 |
2018年 | 2124篇 |
2017年 | 2105篇 |
2016年 | 2171篇 |
2015年 | 1489篇 |
2014年 | 2617篇 |
2013年 | 7950篇 |
2012年 | 4461篇 |
2011年 | 6109篇 |
2010年 | 4930篇 |
2009年 | 5771篇 |
2008年 | 6145篇 |
2007年 | 6195篇 |
2006年 | 5633篇 |
2005年 | 5303篇 |
2004年 | 5249篇 |
2003年 | 5088篇 |
2002年 | 4898篇 |
2001年 | 5305篇 |
2000年 | 4916篇 |
1999年 | 5435篇 |
1998年 | 15617篇 |
1997年 | 10311篇 |
1996年 | 7931篇 |
1995年 | 5784篇 |
1994年 | 5013篇 |
1993年 | 5021篇 |
1992年 | 3385篇 |
1991年 | 3260篇 |
1990年 | 3216篇 |
1989年 | 3039篇 |
1988年 | 2784篇 |
1987年 | 2234篇 |
1986年 | 2301篇 |
1985年 | 2606篇 |
1984年 | 2312篇 |
1983年 | 2063篇 |
1982年 | 1901篇 |
1981年 | 2043篇 |
1980年 | 1790篇 |
1979年 | 1659篇 |
1978年 | 1656篇 |
1977年 | 2021篇 |
1976年 | 2702篇 |
1975年 | 1422篇 |
1974年 | 1369篇 |
1973年 | 1316篇 |
1972年 | 1124篇 |
1971年 | 956篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
T. A. Chernyshova T. V. Lyul'kina L. M. Tribunskii 《Metal Science and Heat Treatment》1992,34(4):258-263
A. A. Baikov Institute of Metallurgy, Moscow. Ulyanovsk Polytechnic Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 22–25, April, 1992. 相似文献
993.
The major goal of this investigation was to collect statistically-based anthropometry describing the kinematics of the human hand and to model this anthropometry as a function of external hand measurements, so that it may be predicted noninvasively. Joint centres were anatomically estimated as the centre of curvature of the head of the bone proximal to the given joint. Joint centres determined using Reuleaux's method for PIP and DIP were within 1.4 mm of this anatomical estimate. Models using bone length as the independent variable explain more than 97% of the variability in the anatomically estimated joint centre position along the mid-line of the bone. Models for estimating the lengths of the kinematic segments using external hand length as the independent variable account for between 49 and 99% of the variability in segment length. Models for estimating the axial location of the finger MCP and thumb CMC joints with respect to the distal wrist crease using external hand length as the independent variable account for between 82 and 96% of the variability in these locations. Models for estimating the radio-ulnar location of the finger MCP and thumb CMC joints with respect to the long axis of the third metacarpal using external hand breadth as the independent variable account for between 30 and 74% of the variability in these locations. 相似文献
994.
Osteoclastic features of multinucleated giant cells responding to synthetic hydroxyapatite implanted in rat jaw bone. 总被引:2,自引:0,他引:2
N Takeshita T Akagi M Yamasaki T Ozeki T Nojima Y Hiramatsu N Nagai 《Journal of electron microscopy》1992,41(3):141-146
Multinucleated giant cells (MGCs) that responded to synthetic hydroxyapatite (HAP) implanted in rat mandibles were studied with electron microscopy. HAP used in this study sintered at 200 degrees C (HAP200) and at 125 degrees C (HAP1250) after the synthesis by a wet method. One to three weeks after the intraosseous implantation of HAP, MGCs responding to HAP200 had not only well-developed ruffled border and the clear zone but well-developed perinuclear Golgi complex, many mitochondria and vesicles in their cytoplasms. MGCs responding to HAP1250 had the clear zone, but not the ruffled border although they showed similar cytoplasmic features to those of MGCs responding to HAP200. They merely extended short slender cytoplasmic processes to HAP1250. These results suggest that although osteoclast-like MGCs respond to HAP implanted in the bone, the development of the ruffled border-clear zone system depends on physicochemical properties of HAP. 相似文献
995.
I Hirata S Kimura T Michihata H Osawa M Kume T Kashima 《Canadian Metallurgical Quarterly》1997,45(8):1173-1177
A 66-year-old male with Beh?et's disease admitted again with hemoptysis. He underwent the resection and direct closure of descending aortic aneurysm 3 years ago, followed without the use of steroid. Chest CT scanning demonstrated a recurrent aneurysm of the descending aorta which was could not be detected on the previous CT only 23 days before. In the current operation, we performed resection, direct closure and wrapping of the aneurysm. The pathological examination showed a true aneurysm of Beh?et's disease. The patient is free from recurrence for 17 months since the operation under steroid therapy. 相似文献
996.
T Kawano 《Canadian Metallurgical Quarterly》1997,55(11):3025-3029
According to the definition of the ICD-10 or DSM-III, sexual dysfunction is not caused by organic disorder or disease, and psychogenic. But, the patient who is suffered from sexual dysfunction caused by organic disorder or disease, has many psycho-social problems. So, in this article, all types of sexual dysfunction are subjected. Especially sexual hypofunction is mentioned. And the new type of sexual dysfunctions such as computer sex are also explained. Sex therapy of the Masters and Johnson method and the new sex therapy of Kaplan, H. are explained. 相似文献
997.
H Matsubara N Oya Y Suzuki S Kajiura K Suzumori Y Matsuo T Suzuki T Hashimoto 《Canadian Metallurgical Quarterly》1997,12(5):306-308
Both choledochal cyst and congenital biliary atresia (type I cyst) may share the same ultrasonographic pattern. We report 2 cases which were shown to have cystic structures on the upper abdomen by antenatal ultrasonography. The size of the choledochal cyst found at 24 weeks' gestation increased steadily as gestational age advanced. But the size of the cyst in congenital biliary atresia found at 29 weeks' gestation remained unchanged throughout the remaining pregnancy. Cyst enlargement, therefore, may suggest the possibility of a choledochal cyst. 相似文献
998.
The author discusses the modeling of a 3-D indoor scene from a single view using a generic object model. It is assumed that an image is made by a well-calibrated camera, and that the camera height above the floor is known. The image is assumed to be a projection of a natural corridor scene from which a generic model is known, but the specific model is unknown. This system can model any corridor that satisfies the following conditions: (1) the corridor is a rectangular parallelepiped, (2) there are several lines along each axis of the rectangle parallelepiped, (3) there are not many parallel lines in directions other than along the principal axes, and (4) corridor height is within a known range. The system for 3-D modeling from a single view of such a corridor consists of a robust bottom-up image processing part and a top-down, model-based interpretation part. Experimental results show that specific corridor models can be recovered from a single view with an approximately 1% estimation error 相似文献
999.
Handschin E. Hoffmann W. Reyer F. Stephanblome T. Schlucking U. Westermann D. Ahmed S.S. 《Power Systems, IEEE Transactions on》1994,9(1):533-539
The synthesis of the structure of the power system stabiliser (PSS) and its parametrization are based entirely on methods of linear system theory. Thus the desired effect of the PSS is limited to a bounded area around one system operating point. The use of a controller based on fuzzy set theory introduces an event controlled excitation of the synchronous machine taking into account the power system operation. The desired response of the fuzzy controller is given by a set of rules which are obtained from the limits of the voltage regulator and the undesired performance of the conventional excitation control. A fuzzy controller has been developed for which simulation results are provided. These results support the concept of a fuzzy controller for the purpose of excitation control. They show that a well designed fuzzy controller is superior to a fast excitation control with an additional PSS 相似文献
1000.
The paper addresses the design of two-level power system stabilizers using an optimal reduced order model whose state variables are torque angles and speeds. The reduced order model retains their physical meaning and is used to design a two-level linear feedback controller that takes into account the realities and constraints of electrical power systems. The two-level control strategy is used, and a global control signal is generated from the output variables to minimize the effect of interactions. The effectiveness of this controller is evaluated and a multimachine system is given as an example to illustrate the advantages of the proposed method. Responses of the system with a two-level scheme and an optimal reduced order scheme are included for comparative analysis. 相似文献