全文获取类型
收费全文 | 12409篇 |
免费 | 746篇 |
国内免费 | 573篇 |
专业分类
电工技术 | 1024篇 |
综合类 | 1370篇 |
化学工业 | 1172篇 |
金属工艺 | 637篇 |
机械仪表 | 730篇 |
建筑科学 | 800篇 |
矿业工程 | 470篇 |
能源动力 | 341篇 |
轻工业 | 1051篇 |
水利工程 | 407篇 |
石油天然气 | 366篇 |
武器工业 | 205篇 |
无线电 | 1086篇 |
一般工业技术 | 782篇 |
冶金工业 | 1802篇 |
原子能技术 | 177篇 |
自动化技术 | 1308篇 |
出版年
2024年 | 7篇 |
2023年 | 31篇 |
2022年 | 76篇 |
2021年 | 158篇 |
2020年 | 128篇 |
2019年 | 76篇 |
2018年 | 116篇 |
2017年 | 140篇 |
2016年 | 172篇 |
2015年 | 328篇 |
2014年 | 515篇 |
2013年 | 611篇 |
2012年 | 915篇 |
2011年 | 952篇 |
2010年 | 1059篇 |
2009年 | 1040篇 |
2008年 | 1182篇 |
2007年 | 1187篇 |
2006年 | 1070篇 |
2005年 | 894篇 |
2004年 | 624篇 |
2003年 | 321篇 |
2002年 | 238篇 |
2001年 | 244篇 |
2000年 | 203篇 |
1999年 | 75篇 |
1998年 | 392篇 |
1997年 | 227篇 |
1996年 | 154篇 |
1995年 | 72篇 |
1994年 | 68篇 |
1993年 | 107篇 |
1992年 | 22篇 |
1991年 | 25篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 20篇 |
1987年 | 24篇 |
1986年 | 11篇 |
1985年 | 17篇 |
1982年 | 6篇 |
1981年 | 12篇 |
1980年 | 19篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 31篇 |
1976年 | 98篇 |
1975年 | 5篇 |
1964年 | 2篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
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
3.
4.
介绍了房地产企业项目进度控制的重要性,从事前、事中、事后三个阶段探讨了工程进度的控制,以保证房地产企业的项目顺利完工,从而保证建筑物的施工质量,提高房地产企业的竞争力。 相似文献
5.
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
6.
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
7.
Photosystem II membranes, dialyzed against a Cl(-)-free buffer to remove bound Cl-, lost about 65% of the control activity. A light-intensity study of the Cl(-)-free membranes showed that all PS II centers were able to evolve oxygen at about 35% of the control rate when measured in Cl(-)-free medium. The Cl(-)-depleted membranes were immediately (< 15 s) reactivated to 85-90% of the original activity by the addition of fairly high concentrations of Cl- (Kd = 0.5 mM), but both Cl- and the activity were promptly lost when the membranes immediately after reactivation were diluted in a Cl(-)-free medium. However, stabilization of Cl(-)-binding could be accomplished by prolonged incubation in the presence of Cl-. The transition to stable binding, followed using 36Cl-, occurred over several minutes. The stable binding was further characterized by a Kd of 20 microM and a t1/2 for dissociation of about 1h [Lindberg et al. (1993) Photosynth. Res. 38, 401-408]. The effects on S2 signals of removal of Cl- were studied using EPR. The depletion of Cl- was accompanied by a shift in intensity toward the g = 4.1 signal at the expense of the multiline signal. When Cl- or Br- but not F- was added to the depleted PS II membranes, the original distribution of the signals was immediately (< 30 s) restored. We propose that Cl(-)-binding responsible for high oxygen-evolution activity and normal EPR properties of the S2 state may occur either as high affinity (Kd = 20 microM) and slowly exchanging (t1/2 = 1 h), or as low affinity (Kd = 0.5 mM) and rapidly exchanging (t1/2 < 15 s). Our results suggest that Br- but not F- has a mode of binding similar to that of Cl-. The high-affinity state is the normal state of binding, but once Cl- has been removed, it will first rebind as low-affinity, rapidly exchanging followed by conversion into a high-affinity, slowly exchanging mode of binding. 相似文献
8.
介绍了一种适用于模式识别的新型神经网络模型--局部有监督特征映射(Reglonal Supervised Feature Mapping,RSFM)网络,描述了该网络的拓扑结构和学习算法,研究了网络的基本性能,最后将其应用到了信号滤波中.理论研究和仿真实验表明,该网络结构简单、算法简洁,收敛速度快、识别精度高,适用于需要大样本训练、随机干扰严重的复杂模式的分类与识别. 相似文献
9.
10.
黑河额济纳绿洲地表水与地下水的关系 总被引:1,自引:0,他引:1
在分析额济纳绿洲水资源组成的基础上,研究了地表水和地下水的时空分布特征。结果表明:地下水埋深随地表径流量的增加而加大,地下水埋深的变化滞后于地表径流量的变化。根据绿洲生态需水的特点,从定性和定量上研究了地表水与地下水的关系,经回归分析提出了定量关系表达式。 相似文献