全文获取类型
收费全文 | 391097篇 |
免费 | 4485篇 |
国内免费 | 1104篇 |
专业分类
电工技术 | 7081篇 |
综合类 | 349篇 |
化学工业 | 62688篇 |
金属工艺 | 16140篇 |
机械仪表 | 11658篇 |
建筑科学 | 9350篇 |
矿业工程 | 2157篇 |
能源动力 | 9252篇 |
轻工业 | 38034篇 |
水利工程 | 3938篇 |
石油天然气 | 7596篇 |
武器工业 | 34篇 |
无线电 | 41905篇 |
一般工业技术 | 73126篇 |
冶金工业 | 73760篇 |
原子能技术 | 9222篇 |
自动化技术 | 30396篇 |
出版年
2021年 | 3185篇 |
2019年 | 3032篇 |
2018年 | 5163篇 |
2017年 | 5121篇 |
2016年 | 5450篇 |
2015年 | 3584篇 |
2014年 | 6176篇 |
2013年 | 16925篇 |
2012年 | 9942篇 |
2011年 | 13644篇 |
2010年 | 10804篇 |
2009年 | 12269篇 |
2008年 | 12543篇 |
2007年 | 12606篇 |
2006年 | 11145篇 |
2005年 | 9994篇 |
2004年 | 9640篇 |
2003年 | 9129篇 |
2002年 | 9115篇 |
2001年 | 9047篇 |
2000年 | 8683篇 |
1999年 | 8749篇 |
1998年 | 21379篇 |
1997年 | 15234篇 |
1996年 | 11761篇 |
1995年 | 9012篇 |
1994年 | 7848篇 |
1993年 | 7713篇 |
1992年 | 5879篇 |
1991年 | 5546篇 |
1990年 | 5653篇 |
1989年 | 5551篇 |
1988年 | 5298篇 |
1987年 | 4742篇 |
1986年 | 4705篇 |
1985年 | 5401篇 |
1984年 | 5069篇 |
1983年 | 4609篇 |
1982年 | 4376篇 |
1981年 | 4492篇 |
1980年 | 4225篇 |
1979年 | 4175篇 |
1978年 | 4190篇 |
1977年 | 4751篇 |
1976年 | 6158篇 |
1975年 | 3678篇 |
1974年 | 3541篇 |
1973年 | 3724篇 |
1972年 | 3105篇 |
1971年 | 2899篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
51.
Sugawara F. Aoki K. Yamaguchi H. Sasaki K. Sasaki T. Fujisaki H. 《Electron Device Letters, IEEE》1997,18(10):483-485
A new lateral MOS-gated thyristor, called the Base-Current-Controlled Thyristor, is described. This device is designed so that most holes at the on-stage reach the P base through the floating P+ region adjacent to the P base and the on-state MOSFET. At the turn-off stage, the interruption of the hole current to the P base due to switching off the above MOSFET occurs simultaneously with the conventional turn-off operation. The concept of this device is verified experimentally by using the fabricated lateral device with the external MOSFET. This device exhibits a better trade-off relation between the on-state voltage and the turn-off time compared uith the conventional MOS-gated thyristor 相似文献
52.
53.
Cresswell M.W. Allen R.A. Guthrie W.F. Sniegowski J.J. Ghoshtagore R.N. Linholm L.W. 《Semiconductor Manufacturing, IEEE Transactions on》1998,11(2):182-193
The physical widths of reference features incorporated into electrical linewidth test structures patterned in films of monocrystalline silicon have been determined from Kelvin voltage measurements. The films in which the test structures are patterned are electrically insulated from the bulk-silicon substrate by a layer of silicon dioxide provided by SIMOX (Separation by the IMplantation of OXygen) processing. The motivation is to facilitate the development of linewidth reference materials for critical-dimension (CD) metrology-instrument calibration. The selection of the (110) orientation of the starting silicon and the orientation of the structures' features relative to the crystal lattice enable a lattice-plane-selective etch to generate reference-feature properties of rectangular cross section and atomically planar sidewalls. These properties are highly desirable for CD applications in which feature widths are certified with nanometer-level uncertainty for use by a diverse range of CD instruments. End applications include the development and calibration of new generations of CD instruments directed at controlling processes for manufacturing devices having sub-quarter-micrometer features 相似文献
54.
The capacitive idling converters derived from the Cuk, SEPIC, Zeta, and flyback topologies allow soft commutation of power switches without the need for additional circuitry, making it possible to increase the switching frequency while maintaining high efficiency 相似文献
55.
We present the design of E-kernel, an embedding kernel on the Victor V256 message-passing partitionable multiprocessor, developed for the support of program mapping and network reconfiguration. E-kernel supports the embedding of a new network topology onto Victor's 2D mesh and also the embedding of a task graph onto the 2D mesh network or the reconfigured network. In the current implementation, the reconfigured network can be a line or an even-size ring, and the task graphs meshes or tori of a variety of dimensions and shapes or graphs with similar topologies. For application programs having these task graph topologies and that are designed according to the communication model of E-kernel, they can be run without any change on partitions connected by the 2D mesh, line, or ring. Further, E-kernel attempts the communication optimization of these programs on the different networks automatically, thus making both the network topology and the communication optimization attempt completely transparent to the application programs. Many of the embeddings used in E-kernel are optimal or asymptotically optimal (with respect to minimum dilation cost). The implementation of E-kernel translated some of the many theoretical results in graph embeddings into practical tools for program mapping and network reconfiguration in a parallel system. E-kernel is functional on Victor V256. Measurements of E-kernel's performance on V256 are also included 相似文献
56.
This research was supported under project No. 6.02.02/128-93 as part of the state scientific-technical program on future information
technologies and systems by the Ukrainian State Committee, of Science and Technology. 相似文献
57.
58.
59.
Variations in lipid profile and incidence of vascular events were evaluated. Group 1 had a 29.3% reduction of total and a 38.3% reduction of LDL cholesterol as against reductions of 9% and 9.6% respectively in group 2. No significant difference was observed between the two groups as far as the vascular events considered were concerned. Pravastatin is an effective and safe drug. The lack of influence on the evolution of vascular disease would appear to be correlated to the small number of subjects studied and the short follow-up. 相似文献
60.
Nutrient uptake by the hindlimb was investigated utilising the arteriovenous difference technique in 5 Thoroughbred horses fed to maintenance a diet of 100% roughage or 52% oat grain and 48% roughage. Arterial blood was obtained from a catheter inserted into the carotid artery while venous blood was simultaneously collected from a catheter placed into the iliac vein via the medial saphenous vein. The arteriovenous difference for glucose was significant and represented a mean extraction of 10 +/- 1% with no effect of diet. If fully oxidised, glucose uptake (corrected for lactate and pyruvate arteriovenous difference) was sufficient to account for 78 +/- 13% or 107 +/- 15% of the oxygen consumed by the hindlimb in horses fed a roughage or 52% oat grain diet respectively. Acetate was also a major metabolite of the hindlimb, showing a 39 +/- 5% extraction with no effect of diet. However, the 52% oat grain diet did induce a significant decline in the concentration of acetate in arterial blood. The potential contribution to oxidation in the hindlimb was significantly reduced from 32 +/- 4% in horses fed roughage to 21 +/- 3% when fed 52% oat grain. D-3-Hydroxybutyrate uptake could account for 9 +/- 1% of the oxidation by the hindlimb with no effect of diet. The technique for measuring nutrient uptake across the hindlimb using the arteriovenous difference is relatively simple and would be valuable in investigating fuel use by muscle during exercise. 相似文献