全文获取类型
收费全文 | 4071篇 |
免费 | 199篇 |
国内免费 | 96篇 |
专业分类
电工技术 | 216篇 |
综合类 | 111篇 |
化学工业 | 209篇 |
金属工艺 | 118篇 |
机械仪表 | 120篇 |
建筑科学 | 161篇 |
矿业工程 | 35篇 |
能源动力 | 50篇 |
轻工业 | 313篇 |
水利工程 | 57篇 |
石油天然气 | 46篇 |
武器工业 | 53篇 |
无线电 | 298篇 |
一般工业技术 | 179篇 |
冶金工业 | 2021篇 |
原子能技术 | 36篇 |
自动化技术 | 343篇 |
出版年
2023年 | 20篇 |
2022年 | 28篇 |
2021年 | 63篇 |
2020年 | 50篇 |
2019年 | 35篇 |
2018年 | 37篇 |
2017年 | 41篇 |
2016年 | 55篇 |
2015年 | 77篇 |
2014年 | 94篇 |
2013年 | 122篇 |
2012年 | 143篇 |
2011年 | 176篇 |
2010年 | 148篇 |
2009年 | 130篇 |
2008年 | 145篇 |
2007年 | 174篇 |
2006年 | 164篇 |
2005年 | 109篇 |
2004年 | 103篇 |
2003年 | 64篇 |
2002年 | 71篇 |
2001年 | 69篇 |
2000年 | 54篇 |
1999年 | 70篇 |
1998年 | 553篇 |
1997年 | 328篇 |
1996年 | 231篇 |
1995年 | 122篇 |
1994年 | 107篇 |
1993年 | 135篇 |
1992年 | 36篇 |
1991年 | 26篇 |
1990年 | 35篇 |
1989年 | 28篇 |
1988年 | 39篇 |
1987年 | 34篇 |
1986年 | 23篇 |
1985年 | 38篇 |
1984年 | 11篇 |
1983年 | 16篇 |
1982年 | 19篇 |
1981年 | 23篇 |
1980年 | 26篇 |
1978年 | 18篇 |
1977年 | 54篇 |
1976年 | 138篇 |
1975年 | 12篇 |
1974年 | 8篇 |
1973年 | 10篇 |
排序方式: 共有4366条查询结果,搜索用时 15 毫秒
1.
Meghelli M. Rylyakov A.V. Zier S.J. Sorna M. Friedman D. 《Solid-State Circuits, IEEE Journal of》2003,38(12):2147-2154
A 43-Gb/s receiver (Rx) and transmitter (Tx) chip set for SONET OC-768 transmission systems is reported. Both ICs are implemented in a 0.18-/spl mu/m SiGe BiCMOS technology featuring 120-GHz f/sub T/ and 100 GHz f/sub max/. The Rx includes a limiting amplifier, a half-rate clock and data recovery unit, a 1:4 demultiplexer, a frequency acquisition aid, and a frequency lock detector. Input sensitivity for a bit-error rate less than 10/sup -9/ is 40 mV and jitter generation better than 230 fs rms. The IC dissipates 2.4 W from a -3.6-V supply voltage. The Tx integrates a half-rate clock multiplier unit with a 4:1 multiplexer. Measured clock jitter generation is better than 170 fs rms. The IC consumes 2.3 W from a -3.6-V supply voltage. 相似文献
2.
IH Bjerkli R Myklebust S R?is?nen S Telimaa LE Stenfors 《Canadian Metallurgical Quarterly》1996,36(3):205-213
Dopaminergic agents and carbidopa/levodopa have become the preferred treatment for both the restless legs (RL) syndrome and for periodic limb movements in sleep (PLMS). For once-nightly treatments with carbidopa/ levodopa, a problem with morning end-of-dose rebound increases in leg movements has been reported to occur in the about one-fourth of the patients. In our clinical studies a previously unreported but far more significant problem of markedly augmented RL symptoms occurred in the afternoon and the evening prior to taking the next nightly dose. A systematic prospective evaluation of this augmentation in 46 consecutive patients treated with carbidopa/ levodopa for RL syndrome or PLMS disorder found this augmentation to be the major adverse effect of treatment. Augmentation occurred for 31% of PLMS patients and 82% of all RL patients. It was greater for subjects with more severe RL symptoms and for patients on higher doses (> or = 50/200 mg carbidopa/levodopa) but was unrelated to gender, age or baseline severity of PLMS. This augmentation was severe enough to require medication change for 50% of the RL patients and 13% of PLMS patients. Augmentation resolved with cessation of the medication and could be minimized by keeping the dose low. 相似文献
3.
Recurrent erosion of the corneal epithelium has been treated successfully by phototherapeutic keratectomy when convention therapy has failed. We present a case of recurrent corneal erosion occurring 1 year after photorefractive keratectomy in a 55-year-old myopic woman. No corneal abnormalities were previously identified in either the affected or the fellow eye. This case demonstrates the potential for ineffective healing of the corneal epithelial basement membrane complex after excimer laser photorefractive keratectomy. 相似文献
4.
LE Lindner 《Canadian Metallurgical Quarterly》1993,41(3):439-445
The silver-staining technique for nucleolar organizer regions (AgNOR) of Ploton et al., as popularized by Crocker, is being widely used for evaluation of nucleolar function, especially in neoplasia. It suffers from limited reliability, background staining, precipitates, and fading of the sections. Factors were identified that affect these problems. The oxidation-reduction level and gelatin used are particularly important. An improved procedure is presented which incorporates pre-reduction of the sections, selection of an optimal gelatin, and post-treatment of the sections to produce a permanent preparation. It is compatible with many fixatives and with other stains used before or after the silver stain. 相似文献
5.
D Averill D Blockus B Brabson J Brom C Jung H Ogren DR Rust M Derrick P Kooijman JS Loos B Musgrave LE Price J Repond K Sugano B Cork C Akerlof J Chapman D Errede MT Ken DI Meyer H Neal D Nitz R Thun R Tschirhart S Abachi P Baringer BG Bylsma R DeBonte D Koltick EH Low RL McIlwain DH Miller CR Ng EI Shibata 《Canadian Metallurgical Quarterly》1989,39(1):123-137
6.
7.
The technique of immunocytochemistry was used to identify myoglobin in kidney, confirming a diagnosis of neuroleptic malignant syndrome following an otherwise obscure autopsy in a decomposed body. The features of neuroleptic malignant syndrome are reviewed with a differential diagnosis of myoglobin renal casts. The report emphasizes a thorough and detailed assessment of deaths which occur during treatment with neuroleptic drugs. 相似文献
8.
We developed a new in vitro model of neuronal injury using NT2-N cells to examine the effects of hydrodynamic loading rate on intraneuronal calcium dynamics and lactate dehydrogenase (LDH) release. Our apparatus consisted of a parallel disk viscometer which induced fluid shear stress with well-defined magnitudes and loading rates to cultured cells. We found that the deformation response of the cells was dependent on the severity of the insult, with increased cellular strains generated for higher shear stresses at a constant loading rate. Peak intracellular free calcium concentration correlated with strain, suggesting that mechanical deformation may regulate calcium response. Slowly applied fluid shear stress elicited no response, whereas high loading rates resulted in peak calcium increases 2.9 to 3.6 times baseline values as injury severity was increased. LDH release measured within 5 min after the insult correlated with loading rate. In addition, LDH release continued to increase out to 24 h following high loading rate conditions, demonstrating that the application of fluid shear stress led to prolonged cell damage. The acute response in NT2-N cells subjected to an insult with the CSID is dependent on the loading rate, and these results suggest that initial membrane deformation may trigger subsequent events. 相似文献
9.
JW Innis JH Asher Y Liang A Wang CM Wilke HA Dierick K Kazen-Gillespie S Sheldon TW Glover TB Friedman 《Canadian Metallurgical Quarterly》1997,71(3):292-297
Cleidocranial dysplasia (CCD) is an autosomal dominant, generalized skeletal dysplasia in humans that has been mapped to the short arm of chromosome 6. We report linkage of a CCD mutation to 6p21 in a large family and exclude the bone morphogenetic protein 6 gene (BMP6) as a candidate for the disease by cytogenetic localization and genetic recombination. CCD was linked with a maximal two-point LOD score of 7.22 with marker D6S452 at theta = 0. One relative with a recombination between D6S451 and D6S459 and another individual with a recombination between D6S465 and CCD places the mutation within a 7 cM region between D6S451 and D6S465 at 6p21. A phage P1 genomic clone spanning most of the BMP6 gene hybridized to chromosome 6 in band region p23-p24 using FISH analysis, placing this gene cytogenetically more distal than the region of linkage for CCD. We derived a new polymorphic marker from this same P1 clone and found recombinations between the marker and CCD in this family. The results confirm the map position of CCD on 6p21, further refine the CCD genetic interval by identifying a recombination between D6S451 and D6S459, and exclude BMP6 as a candidate gene. 相似文献
10.
MJ Glantz PC Burger AH Friedman RA Radtke EW Massey SC Schold 《Canadian Metallurgical Quarterly》1994,44(11):2020-2027
When radiation is used to treat nervous system cancer, exposure of adjacent normal nervous system tissue is unavoidable, and radiation-induced injury may occur. Acute injury is usually mild and transient, but late forms of radiation-induced nervous system injury are usually progressive and debilitating. Treatment with corticosteroids, surgery, and antioxidants is often ineffective. We treated 11 patients with late radiation-induced nervous system injuries (eight with cerebral radionecrosis, one with a myelopathy, and two with plexopathies, all unresponsive to dexamethasone and prednisone) with full anticoagulation. Some recovery of function occurred in five of the eight patients with cerebral radionecrosis, and all the patients with myelopathy or plexopathy. Anticoagulation was continued for 3 to 6 months. In one patient with cerebral radionecrosis, symptoms recurred after discontinuation of anticoagulation and disappeared again after reinstitution of treatment. We hypothesize that anticoagulation may arrest and reverse small-vessel endothelial injury--the fundamental lesion of radiation necrosis--and produce clinical improvement in some patients. 相似文献