全文获取类型
收费全文 | 35238篇 |
免费 | 2621篇 |
国内免费 | 1355篇 |
专业分类
电工技术 | 1860篇 |
综合类 | 1504篇 |
化学工业 | 7769篇 |
金属工艺 | 1853篇 |
机械仪表 | 2050篇 |
建筑科学 | 1100篇 |
矿业工程 | 630篇 |
能源动力 | 8266篇 |
轻工业 | 3014篇 |
水利工程 | 201篇 |
石油天然气 | 659篇 |
武器工业 | 121篇 |
无线电 | 3418篇 |
一般工业技术 | 3729篇 |
冶金工业 | 1193篇 |
原子能技术 | 478篇 |
自动化技术 | 1369篇 |
出版年
2024年 | 104篇 |
2023年 | 709篇 |
2022年 | 1845篇 |
2021年 | 2162篇 |
2020年 | 1388篇 |
2019年 | 1288篇 |
2018年 | 1059篇 |
2017年 | 1310篇 |
2016年 | 1237篇 |
2015年 | 1178篇 |
2014年 | 2007篇 |
2013年 | 2196篇 |
2012年 | 2224篇 |
2011年 | 3043篇 |
2010年 | 2305篇 |
2009年 | 2007篇 |
2008年 | 1930篇 |
2007年 | 1890篇 |
2006年 | 1687篇 |
2005年 | 1302篇 |
2004年 | 1071篇 |
2003年 | 857篇 |
2002年 | 767篇 |
2001年 | 617篇 |
2000年 | 519篇 |
1999年 | 429篇 |
1998年 | 374篇 |
1997年 | 286篇 |
1996年 | 251篇 |
1995年 | 212篇 |
1994年 | 176篇 |
1993年 | 157篇 |
1992年 | 128篇 |
1991年 | 100篇 |
1990年 | 80篇 |
1989年 | 65篇 |
1988年 | 46篇 |
1987年 | 27篇 |
1986年 | 33篇 |
1985年 | 37篇 |
1984年 | 27篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 14篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1975年 | 2篇 |
1959年 | 2篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
We report a simple processing method to simultaneously improve the efficiency and stability of organic solar cells (OSCs). Poly(4-styrene sulfonate)-doped poly(3,4-ethylenedioxy-thiophene (PEDOT:PSS), widely used as hole transport layer (HTL) in OSCs, tends to accelerate the degradation of devices because of its hygroscopic and acidic properties. In this regard, we have modified PEDOT:PSS to reduce its hygroscopic and acidic properties through a condensation reaction between PEDOT:PSS and poly(ethylene glycol) methyl ether (PEGME) in order to improve the efficiency and stability of OSCs. As a result, the power conversion efficiency (PCE) increased by 21%, from 2.57% up to 3.11%. A better energy level alignment by the reduced work function of the modified PEDOT:PSS with a highest occupied molecular orbital (HOMO) level of poly(3-hexylthiophene-2,5-diyl) (P3HT) is considered the origin of the improved the efficiency. The half-life of OSCs with PEDOT:PSS modified with PEGME buffer layer also increased up to 3.5 times compared to that of devices with pristine PEDOT:PSS buffer layer. 相似文献
3.
Klaus Reinhardt Hans Georg Breunig Aisada Uchugonova Karsten K?nig 《Journal of the Royal Society Interface》2015,12(110)
We explore the possibility of characterizing sperm cells without the need to stain them using spectral and fluorescence lifetime analyses after multi-photon excitation in an insect model. The autofluorescence emission spectrum of sperm of the common bedbug, Cimex lectularius, was consistent with the presence of flavins and NAD(P)H. The mean fluorescence lifetimes showed smaller variation in sperm extracted from the male (tau m, τm = 1.54–1.84 ns) than in that extracted from the female sperm storage organ (tau m, τm = 1.26–2.00 ns). The fluorescence lifetime histograms revealed four peaks. These peaks (0.18, 0.92, 2.50 and 3.80 ns) suggest the presence of NAD(P)H and flavins and show that sperm metabolism can be characterized using fluorescence lifetime imaging. The difference in fluorescence lifetime variation between the sexes is consistent with the notion that female animals alter the metabolism of sperm cells during storage. It is not consistent, however, with the idea that sperm metabolism represents a sexually selected character that provides females with information about the male genotype. 相似文献
4.
5.
Towards a Better Prediction of Cell Settling on Nanostructure Arrays—Simple Means to Complicated Ends 下载免费PDF全文
Nina Buch‐Månson Sara Bonde Jessica Bolinsson Trine Berthing Jesper Nygård Karen L. Martinez 《Advanced functional materials》2015,25(21):3246-3255
Vertical arrays of nanostructures (NSs) are emerging as promising platforms for probing and manipulating live mammalian cells. The broad range of applications requires different types of interfaces, but cell settling on NS arrays is not yet fully controlled and understood. Cells are both seen to deform completely into NS arrays and to stay suspended like tiny fakirs, which have hitherto been explained with differences in NS spacing or density. Here, a better understanding of this phenomenon is provided by using a model that takes into account the extreme membrane deformation needed for a cell to settle into a NS array. It is shown that, in addition to the NS density, cell settling depends strongly on the dimensions of the single NS, and that the settling can be predicted for a given NS array geometry. The predictive power of the model is confirmed by experiments and good agreement with cases from the literature. Furthermore, the influence of cell‐related parameters is evaluated theoretically and a generic method of tuning cell settling through surface coating is demonstrated experimentally. These findings allow a more rational design of NS arrays for the numerous exciting biological applications where the mode of cell settling is crucial. 相似文献
6.
In this paper, a model taking into account the effects of carrier loss mechanisms has been developed. The model simulates the photovoltaic properties of the graphene/n-type silicon Schottky barrier solar cells (G/n-Si_SBSC), and it can reproduce the experimentally determined parameters of the G/n-Si_SBSC. To overcome the low efficiencies of G/n-Si_SBSC, their performances have been optimized by modifying the work function of graphene and Si properties, accounted for variation of its thickness and doping level. The obtained results show that the work function of graphene has the major impact on the device performance. Also, the temperature dependence of the G/n-Si_SBSC performance is investigated. 相似文献
7.
Textured surface is commonly used to enhance the efficiency of silicon solar cells by reducing the overall reflectance and improving the light scattering. In this study, a comparison between isotropic and anisotropic etching methods was investigated. The deep funnel shaped structures with high aspect ratio are proposed for better light trapping with low reflectance in crystalline silicon solar cells. The anisotropic metal assisted chemical etching (MACE) was used to form the funnel shaped structures with various aspect ratios. The funnel shaped structures showed an average reflectance of 14.75% while it was 15.77% for the pillar shaped structures. The average reflectance was further reduced to 9.49% using deep funnel shaped structures with an aspect ratio of 1:1.18. The deep funnel shaped structures with high aspect ratios can be employed for high performance of crystalline silicon solar cells. 相似文献
8.
CO2激光治疗皮肤基底细胞癌14例临床观察 总被引:4,自引:0,他引:4
目的 :探求一种简单 ,安全 ,效果好的基底细胞癌的治疗方法。方法 :对 1 4例基底细胞癌患者在局麻下用CO2 激光行基底细胞癌切除术或切除 +气化术。结果 :患者术中、术后出血少 ,伤口恢复快 ,愈合良好 ,疤痕表浅 ,随访未见复发。结论 :CO2 激光用于治疗基底细胞癌效果良好 ,无明显副作用 ,操作简单值得推广。 相似文献
9.
1 Influence of PAMAon Boundary Fil mFormation and Friction1.1 Experi mental methodsUltra-thin optical interferometry has been used tostudy thinlubricating fil ms for more than a decade and theexperi mental details of this technique have been reportedpreviously[1].The principle of the test setup is shown inFigure1.A polished steel ball is loaded and rolled againstthe flat surface of a glass disc that is coated with a thinsemi-reflecting chromiumlayer and a silica spacer of about500nmthickne… 相似文献
10.
工业管道测厚的几点问题探讨 总被引:2,自引:0,他引:2
超声波测厚在腐蚀监测上应用越来越广泛,为让这项检测技术更准确、更可靠,充分发挥功效,文章就工业管道测厚中测厚数据处理、测厚点选择、高温问题以及其它影响因素等几个方面进行了探讨。 相似文献