全文获取类型
收费全文 | 7457篇 |
免费 | 176篇 |
国内免费 | 15篇 |
学科分类
工业技术 | 7648篇 |
出版年
2023年 | 25篇 |
2022年 | 50篇 |
2021年 | 113篇 |
2020年 | 66篇 |
2019年 | 79篇 |
2018年 | 103篇 |
2017年 | 84篇 |
2016年 | 119篇 |
2015年 | 80篇 |
2014年 | 174篇 |
2013年 | 372篇 |
2012年 | 248篇 |
2011年 | 380篇 |
2010年 | 270篇 |
2009年 | 303篇 |
2008年 | 313篇 |
2007年 | 291篇 |
2006年 | 289篇 |
2005年 | 253篇 |
2004年 | 224篇 |
2003年 | 245篇 |
2002年 | 216篇 |
2001年 | 150篇 |
2000年 | 134篇 |
1999年 | 186篇 |
1998年 | 543篇 |
1997年 | 383篇 |
1996年 | 295篇 |
1995年 | 175篇 |
1994年 | 178篇 |
1993年 | 174篇 |
1992年 | 81篇 |
1991年 | 80篇 |
1990年 | 82篇 |
1989年 | 77篇 |
1988年 | 61篇 |
1987年 | 53篇 |
1986年 | 71篇 |
1985年 | 80篇 |
1984年 | 55篇 |
1983年 | 63篇 |
1982年 | 57篇 |
1981年 | 62篇 |
1980年 | 64篇 |
1979年 | 41篇 |
1978年 | 22篇 |
1977年 | 34篇 |
1976年 | 57篇 |
1975年 | 18篇 |
1973年 | 17篇 |
排序方式: 共有7648条查询结果,搜索用时 15 毫秒
991.
The significant increase of output energy of a UV-preionized KrF laser has been obtained by a change of electrode separation. This fact is explained by the measured impedance and deposit energy in a discharge. The efficient amplification has been performed by using a exactly synchronized amplification system. The maximum output energy was 0.75 J/pulse with a pulsewidth of 40 ns and a total efficiency of 0.8 percent. The saturation intensity and small-signal gain coefficient for KrF laser have been measured. The saturation intensity was 1.7 MW/cm2and the small-signal gain coefficient reached 4.7 percent/cm at a charging voltage of 35 kV. 相似文献
992.
We investigated the current/voltage characteristics of n+GaAs/undoped AlxGa1?xAs (200 A)/n+GaAs heterostructures grown by the metalorganic chemical vapour deposition (MOCVD) method between 77 K and 300 K. Both the voltage dependence and the temperature dependence of the current were in good agreement over a wide current range with the calculated results of the tunnelling and thermionic emission current. 相似文献
993.
Shoichi Nasu Takaaki Tanifuji Katsuya Uchida Kenji Noda Toshimasa Kurasawa Tadashi Takahashi Masahiko Isshiki Takejiro Miyauchi Kohji Tanuma Fumio Sasajima 《Journal of Nuclear Materials》1980,91(1):121-126
The center temperature of Li2O pellets under neutron irradiation was measured using an encapsuled pin. The surface temperatures of the pellets and the pellet/cladding heat transfer coefficients were estimated on the basis of the well-known conductivity integral. 相似文献
994.
Zhong-Wen Liu Xiaohong Li Kenji Asami Kaoru Fujimoto 《Applied Catalysis A: General》2006,300(2):162-169
The direct synthesis of gasoline-range iso-paraffins from synthesis gas (CO + H2, syngas) via a modified Fischer–Tropsch (FT) reaction was intensively studied under a wide range of reaction conditions by the combination of Co/SiO2 and Pd/beta in a consecutive dual reactor system. Results indicate that high selectivity of gasoline-range iso-paraffins (iso-paraffins relative to C4+ hydrocarbons was about 80%) could be achieved with the presence of Pd/beta catalyst in the lower reactor. Moreover, the performance of the Pd/beta catalyst for the titled reaction and the product composition can be significantly regulated by independently changing the reaction conditions such as catalyst amount, reaction temperature, and hydrogen partial pressure in the lower reactor. It was found that the Pd/beta catalyst used in this work was very active and stable even at a reaction temperature as low as 503 K. With the increase of hydrogen partial pressure in the lower reactor, the long-term stability of the Pd/beta catalyst was significantly enhanced. 相似文献
995.
The effects of irrelevant differences as a function of the relations between relevant and irrelevant dimensions in the same–different task were examined. Form, size, and orientation were used as task conditions in Experiment 1, and form, size, and color were used in Experiment 2. In each experiment, 6 subjects were instructed to report same or different according to a relevant dimension, irrespective of two irrelevant dimensions. In Experiment 3, the degree of integrality was examined in all the combinations of dimensions involved, in the restricted-classification task. The results of the three experiments suggested that (a) effects of irrelevant differences depended on the degree of integrality between relevant and irrelevant dimensions, and (b) two irrelevant dimensions were processed by the subjects serially. Neither the relevance rechecking model (Miller & Bauer, 1981) nor the response competition model (e.g., Williams, 1974) alone could explain all the types of effects of irrelevant dimensions obtained in this study. Instead, a modified relevance rechecking model, in which the degree of integrality was introduced to the original relevance rechecking model, could predict and explain all types of effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
996.
Five bacterial strains isolated from the intestine of deep sea fish were shown to produce docosahexaenoic acid (22∶6n−3; DHA)
at a level of 6.4 to 11.6% of total fatty acids when incubated in DHA-free medium. In all of the strains examined, other polyunsaturated
fatty acids were barely detectable, except for eicosapentaenoic acid (20∶5n−3). A typical strain, such as T3615, produced
DHA at a concentration of about 0.8 mg/L within six days of aerobic incubation at 5°C and under atmospheric pressure. The
T3615 strain, belonging to the genusVibrio, is rod-shaped, Gram-negative, motile and facultatively anaerobic. 相似文献
997.
Kenji Asami Qianwen Zhang Xiaohong Li Sachio Asaoka Kaoru Fujimoto 《Catalysis Today》2005,106(1-4):247-251
Efficient conversion of dimethyl ether (DME) into liquefied petroleum gas (LPG) with a hybrid catalyst is a novel method for semi-indirect synthesis of LPG fuel from syngas. The hybrid catalysts consisting of zeolite and hydrogenation catalyst were investigated in a fixed bed reactor. Experimental results demonstrated that the hybrid catalyst consisting of (Pd/SiO2) and USY efficiently converted DME into LPG and restrained decomposition of DME into CO and H2. With that catalyst, the one through conversion of DME reached about 100%, almost no CO and CO2 were produced and selectivity for LPG was more than 65%. 相似文献
998.
Akira Matsumoto Takayuki Nakagawa Masatoshi Sato Yasunori Kimura Kenji Nishida Atsuhiro Goto 《New Generation Computing》1991,9(2):149-169
The parallel inference machine (PIM) is now being developed at ICOT. It consists of a dozen or more clusters, each of which
is a tightly coupled multiprocessor (comprising about eight processing elements) with shared global memory and a common bus.
Kernel language 1 (KL1), a parallel logic programming language based on Guarded Horn Clauses (GHC), is executed on each PIM
cluster.
This paper describes the memory access characteristics in KL1 parallel execution and a locally parallel cache mechanism with
hardware lock. The most important issue of locally parallel cache design is how to reduce common bus traffic. A write-back
cache protocol having five cache states specially optimized for KL1 execution on each PIM cluster is described. We introduced
new software controlled memory access commands, named DW, ER, and RP. A hardware lock mechanism is attached to the cache on
each processor. This lock mechanism enables efficient word-by-word locking, reducing common bus traffic by using the cache
states. 相似文献
999.
Furuyama T. Ohsawa T. Nagahama Y. Tanaka H. Watanabe Y. Kimura T. Muraoka K. Natori K. 《Solid-State Circuits, IEEE Journal of》1989,24(2):388-393
A multiple-level 2-bit/cell storage technique for DRAMs (dynamic random-access memories) has been developed. The total RAM area is reduced and the cell array is cut in half. Since the memory cell area is especially defect-sensitive, this technique is highly effective for process yield improvement. Reasonable access time has been realized with this technique: 170 ns is still fast enough for many ASIC (application-specific integrated circuit) memory applications. This technique meets the requirement of high density and moderate speed. It was found that the 2-bit/cell storage technique is suitable for macrocell or memory-on-logic type application 相似文献
1000.
Tadanori Shimoto Kazuhiro Baba Koji Matsui Jun Tsukano Takehiko Maeda Kenji Oyachi 《Microelectronics Reliability》2005,45(3-4):567-574
An ultra-thin high-density LSI packaging substrate, called multi-layer thin substrate (MLTS), is described. It meets the demand for chip scale packages (CSPs) and systems in a package (SiPs) for use in recently developed small portable applications with multiple functions. A high-density build-up structure is fabricated on a Cu plate, which is then removed, leaving only an ultra-thin, high-density multi-layer substrate. MLTS has (1) excellent registration accuracy, which enables higher density and finer pitch patterning due to the use of a rigid, excellent-flatness Cu base plate; (2) a thinner multi-layer structure due to the use of a core-less multi-layer structure; (3) excellent reliability, supported by the use of an aramid-reinforced epoxy resin dielectric layer; and (4) a cost-effective design due to the use of fewer layers fabricated using a conventional build-up process. A prototype high-density CSP (0.4-mm pitch/288 pins/4 rows/10 mm2) was fabricated using a 90-μm-thick MLTS (with a solder resist layer). Testing demonstrated that it had excellent long-term reliability. A prototype ultra-thin, high-density SiP (0.5-mm pitch/225 pins/11 mm2/0.93 mm thick) was also fabricated based on MLTS. MLTS consists of only two conductor layers (total thickness: 90 μm) while an identical-function build-up printed wiring board needs four conductor layers (total thickness: 300 μm). With its thinner core-less multi-layer structure, MLTS enables the fabrication of ultra-thin, high-density SiPs. 相似文献