全文获取类型
收费全文 | 4334篇 |
免费 | 227篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 45篇 |
化学工业 | 776篇 |
金属工艺 | 52篇 |
机械仪表 | 86篇 |
建筑科学 | 139篇 |
矿业工程 | 11篇 |
能源动力 | 124篇 |
轻工业 | 373篇 |
水利工程 | 41篇 |
石油天然气 | 10篇 |
无线电 | 411篇 |
一般工业技术 | 798篇 |
冶金工业 | 1084篇 |
原子能技术 | 28篇 |
自动化技术 | 590篇 |
出版年
2023年 | 38篇 |
2022年 | 67篇 |
2021年 | 106篇 |
2020年 | 73篇 |
2019年 | 108篇 |
2018年 | 114篇 |
2017年 | 90篇 |
2016年 | 116篇 |
2015年 | 93篇 |
2014年 | 150篇 |
2013年 | 206篇 |
2012年 | 193篇 |
2011年 | 267篇 |
2010年 | 197篇 |
2009年 | 168篇 |
2008年 | 221篇 |
2007年 | 201篇 |
2006年 | 149篇 |
2005年 | 131篇 |
2004年 | 96篇 |
2003年 | 95篇 |
2002年 | 89篇 |
2001年 | 53篇 |
2000年 | 52篇 |
1999年 | 68篇 |
1998年 | 252篇 |
1997年 | 176篇 |
1996年 | 102篇 |
1995年 | 71篇 |
1994年 | 79篇 |
1993年 | 76篇 |
1992年 | 41篇 |
1991年 | 29篇 |
1990年 | 39篇 |
1989年 | 35篇 |
1988年 | 32篇 |
1987年 | 28篇 |
1986年 | 32篇 |
1985年 | 20篇 |
1984年 | 33篇 |
1983年 | 25篇 |
1982年 | 22篇 |
1981年 | 21篇 |
1980年 | 22篇 |
1979年 | 27篇 |
1978年 | 25篇 |
1977年 | 45篇 |
1976年 | 55篇 |
1975年 | 17篇 |
1971年 | 18篇 |
排序方式: 共有4568条查询结果,搜索用时 9 毫秒
1.
2.
Benjarat Tepsongkroh Kamolwan Jangchud Anuvat Jangchud Pitchayapat Chonpracha Ryan Ardoin Witoon Prinyawiwatkul 《International Journal of Food Science & Technology》2020,55(1):46-54
Effects of mushroom type, seasoning and health benefit information (HBI) on consumers’ saltiness expectation, sensory liking, elicited emotions and purchase intent (PI) of extruded snacks were investigated. Five snacks were evaluated: straw mushroom (Volvariella volvacea) extrudates without (SME) or with seasoning (SMES), phoenix mushroom (Pleurotus pulmonarius) extrudates without (PME) or with seasoning (PMES), and the control without mushroom and seasoning. Hedonic scores and positive emotions were generally higher for seasoned mushroom-containing snacks (SMES and PMES) with 65% and 75.83% of consumers reporting willingness to purchase, respectively, after receiving HBI. Bored, interested and satisfied were identified as significant emotional predictors for PI odds. Flavour, saltiness, overall liking, bored, good and interested were critical attributes, differentiating snacks. This study demonstrated that sensory liking and PI of extruded brown rice-based snacks containing mushroom could be improved through savoury seasoning addition, which also allowed saltiness expectations to be met. 相似文献
3.
In this paper, we first re-examine the previous protocol of controlled quantum secure direct communication of Zhang et al.’s scheme, which was found insecure under two kinds of attacks, fake entangled particles attack and disentanglement attack. Then, by changing the party of the preparation of cluster states and using unitary operations, we present an improved protocol which can avoid these two kinds of attacks. Moreover, the protocol is proposed using the three-qubit partially entangled set of states. It is more efficient by only using three particles rather than four or even more to transmit one bit secret information. Given our using state is much easier to prepare for multiqubit states and our protocol needs less measurement resource, it makes this protocol more convenient from an applied point of view. 相似文献
4.
5.
6.
Kuh S.S. Strozier T.A. Ryan C.R. 《Selected Areas in Communications, IEEE Journal on》1989,7(9):1462-1469
A continuous phase quadrature phase shift keyed (CPQPSK) modulation technique is presented. This method utilizes a conventional QPSK modulator and a phase trajectory converter to approximate M =4, h =1/4 continuous phase signal and allows low cost, low complexity, and high rate (>1 Gbit/s) CPM modem implementation for bandwidth efficient transmission through nonlinear satellite channels. Using a communications analysis computer program it has been found that CPQPSK has 99 percent out-of-band power of 0.8R (MSK has 99 percent out-of-band power of 1.2 R where R is defined as bit rate), continuous phase trajectories, and nearly constant envelope amplitude. Simulation of realistic hardware designs indicate that the CPQPSK will require an Eb /No of 14 dB to achieve a bit error rate (BER) of 10-6. Forward error correcting techniques using block codes with an overhead of 10 percent indicate that the Eb /No requirements can be reduced to 11.2 dB for 10-6 BER 相似文献
7.
SA Morse DL Trees Y Htun F Radebe KA Orle Y Dangor CM Beck-Sague S Schmid G Fehler JB Weiss RC Ballard 《Canadian Metallurgical Quarterly》1997,175(3):583-589
A multiplex polymerase chain reaction (M-PCR) assay for Haemophilus ducreyi, Treponema pallidum, and herpes simplex virus (HSV) was compared with clinical and standard laboratory methods for the diagnosis of genital ulcer disease (GUD) in 105 patients; 36% were human immunodeficiency virus (HIV)-seropositive. Chancroid (80%), syphilis (8%), and genital herpes (8%) were the most frequent diagnoses. H. ducreyi and HSV were isolated from ulcers of 43% and 18% of patients, respectively; in 35%, all cultures were negative and the laboratory diagnosis indeterminate. M-PCR detected H. ducreyi, T. pallidum, and HSV in 56%, 23%, and 26% of patients, respectively; (no definitive diagnosis, 6%). The proportion of patients with more than one agent was 4% by culture and 17% by M-PCR (P = .002). Resolved sensitivities of M-PCR for H. ducreyi and HSV cultures were 95% and 93%, respectively. The sensitivities of H. ducreyi and HSV cultures were 75% and 60%, respectively. HSV, detected in 47% of specimens from HIV-infected versus 16% from HIV-uninfected patients (P < .001), may be emerging as a more frequent cause of GUD. 相似文献
8.
F F?ndrich AM Waaga J Schr?der E Schweizer A Schmid S Jacob HH Wacker P Schroeder 《Canadian Metallurgical Quarterly》1995,27(2):1553-1554
9.
PL Pirie BL Rooney TF Pechacek HA Lando LA Schmid 《Canadian Metallurgical Quarterly》1997,22(1):131-137
Exposure to foreign particles sometimes causes inflammatory reactions through production of cytokines and chemoattractants by phagocytic cells. In this study, we focused on macrophage migration inhibitory factor (MIF) to evaluate its pathophysiological role in the phagocytic process. Immunohistochemical analysis of human pseudosynovial tissues retrieved at revision of total hip arthroplasty showed that infiltrating mononuclear and multinuclear cells were positively stained by both an anti-CD68 antibody and anti-human MIF antibody. For in vitro study, MIF was released from murine macrophage-like cells (RAW 264.7) in response to phagocytosis of fluorescent-latex beads in a particle dose-dependent manner. Northern blot analysis showed marked elevation of the MIF mRNA level in the phagocytic macrophage-like cells. Moreover, pretreatment of RAW 264.7 cells with rat recombinant MIF increased the extent of phagocytosis by 1.6-fold compared with the control. Taken together, these results suggest that MIF plays an important role by activating macrophages in autocrine and paracrine fashion to phagocytose foreign particles. 相似文献
10.
A predictive analogy of turbulent mass transfer across wavy, sheared air-water interface, in deep water bodies is proposed. The theory is based on the formulation of a theoretical eddy diffusivity profile in the surface region, and it applies to the non-breaking wave regime. The predictions for a water-side friction velocity range of 0.5–6 cm/s are in excellent agreement with laboratory data from wind-wave facilities with an average error of 15.4%. 相似文献