全文获取类型
收费全文 | 18352篇 |
免费 | 489篇 |
国内免费 | 42篇 |
专业分类
电工技术 | 330篇 |
综合类 | 29篇 |
化学工业 | 3282篇 |
金属工艺 | 385篇 |
机械仪表 | 410篇 |
建筑科学 | 891篇 |
矿业工程 | 33篇 |
能源动力 | 363篇 |
轻工业 | 2343篇 |
水利工程 | 142篇 |
石油天然气 | 42篇 |
无线电 | 1654篇 |
一般工业技术 | 2750篇 |
冶金工业 | 3735篇 |
原子能技术 | 224篇 |
自动化技术 | 2270篇 |
出版年
2022年 | 147篇 |
2021年 | 256篇 |
2020年 | 169篇 |
2019年 | 218篇 |
2018年 | 268篇 |
2017年 | 280篇 |
2016年 | 346篇 |
2015年 | 275篇 |
2014年 | 415篇 |
2013年 | 835篇 |
2012年 | 674篇 |
2011年 | 805篇 |
2010年 | 660篇 |
2009年 | 660篇 |
2008年 | 715篇 |
2007年 | 737篇 |
2006年 | 596篇 |
2005年 | 599篇 |
2004年 | 496篇 |
2003年 | 437篇 |
2002年 | 420篇 |
2001年 | 404篇 |
2000年 | 378篇 |
1999年 | 397篇 |
1998年 | 1089篇 |
1997年 | 708篇 |
1996年 | 549篇 |
1995年 | 421篇 |
1994年 | 336篇 |
1993年 | 370篇 |
1992年 | 239篇 |
1991年 | 194篇 |
1990年 | 207篇 |
1989年 | 205篇 |
1988年 | 175篇 |
1987年 | 177篇 |
1986年 | 173篇 |
1985年 | 227篇 |
1984年 | 173篇 |
1983年 | 156篇 |
1982年 | 136篇 |
1981年 | 165篇 |
1980年 | 159篇 |
1979年 | 159篇 |
1978年 | 98篇 |
1977年 | 166篇 |
1976年 | 214篇 |
1975年 | 110篇 |
1974年 | 109篇 |
1973年 | 109篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
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
3.
4.
5.
In advancement of Pyrosil®‐technology a new kind of precursor delivery was developed, build and tested on real substrates. A Lab‐demonstrator was build to demonstrate the resources of the technology. 相似文献
6.
A central event in the life of a cellular system is the interaction between the exterior and the interior compartments. Biochemical signals arrive at the cellular surface, bind to their membrane bound receptor followed by a conformational change triggering the release of an internal chemical or electrical signal.This basic principle is followed by all our perceptive abilities like sense of smell or taste, but also by different signal transduction pathways involved in nerve conductivity, vision, sense of touch or hearing. To follow and mimic this principle of parallel registration is one of the aims of modern nanobiotechnology. If we are able to specifically biofunctionalize small arrays of a solid surface, which could be an electrode or a semiconductor, this approach will enable us to build up devices called “biochips” or “biosensors” that allow the determination of bioactive molecules with high specificity at lowest concentrations. Potential pharmacological active substrates might be screened as well as new receptors may be determined. Applications in genomics as well as proteomics are realistic. The major prerequisite for such a broad spectrum of applications is the fabrication of receptive surfaces. Biomolecules have to be surface‐adsorbed in a highly reproducible, oriented and well organised fashion, a task which in biology is taken by the cellular membranes as external or internal receptive surfaces. The physical principles like hydrogen bonds, electrostatic or hydrophobic interactions that lead to such an organized surface are well known. To synthesize molecular building blocks and to position them onto an otherwise unspecific surface is one of the challenges of nanobiotechnology combining biological knowledge and chemical skills with biophysical techniques that allow to handle or analyze even single molecules. 相似文献
7.
Bart Van der Bruggen 《Membrane Technology》2003,2003(2):6-9
As the requirement for fresh water increases worldwide, there is a need for more and more plants that are able to treat non-conventional water sources. Sea water has become an important source of fresh water in many arid regions. This feature provides an overview of recent process improvements in sea water desalination using reverse osmosis, multi-stage flash, multi-effect distillation and electrodialysis. Areas discussed include the use of alternative energy sources (wind energy, solar energy and nuclear energy) for reverse osmosis or distillation processes, and the impact of the different desalination process on the environment. Also covered are the implementation of hybrid processes in sea water desalination, and the pretreatment of desalination plants by pressure-driven membrane processes. 相似文献
8.
Frank te Beest Ad Peeters Kees van Berkel Hans Kerkhoff 《Journal of Electronic Testing》2003,19(4):397-406
Handshake circuits form a special class of asynchronous circuits that has enabled the industrial exploitation of the asynchronous potential such as low power, low electromagnetic emission, and increased cryptographic security. In this paper we present a test solution for handshake circuits that brings synchronous test-quality to asynchronous circuits. We add a synchronous mode of operation to handshake circuits that allows full controllability and observability during test. This technique is demonstrated on some industrial examples and gives over 99% stuck-at fault coverage, using test-pattern generators developed for synchronous circuits. The paper describes how such a full-scan mode can be achieved, including an approach to minimize the number of dummy latches in case latches are used in the data path of the handshake circuit. 相似文献
9.
Vladimir Rozenshtein Alexander Berg Haim Levanon Uwe Krueger Dietmar Stehlik Yuri Kandrashkin Art Van Der Est 《Israel journal of chemistry》2003,43(3-4):373-381
Light-induced spin-polarized transient EPR spectra are reported for several water-soluble copper porphyrins. The spectra are assigned to the doublet ground state, with emissive spin polarization resulting from photoexcitation and subsequent electronic relaxation. In contrast to other systems for which polarization of a doublet ground state has been observed, the exchange interactions in the copper porphyrins are strong and the geometry is fixed. It is proposed that intersystem crossing from the photoexcited trip-doublet to the trip-quartet state can lead to net polarization of the spin system and that this polarization is maintained during electronic decay, possibly via charge-transfer and exciplex states. The intensity of the observed spin polarization is essentially independent of the molecular orientation in the external field, but is strongly dependent on the nature of the charged peripheral groups. Possible reasons for this behavior are discussed. 相似文献
10.
Montanari D. Van Houdt J. Groeseneken G. Maes H.E. 《Solid-State Circuits, IEEE Journal of》1998,33(7):1090-1095
This paper presents a high-speed, small-area circuit specifically designed to identify the levels in the read out operation of a flash multilevel memory. The circuit is based on the analog computation of the Euclidean distance between the current read out from a memory cell and the reference currents that represent the different logic levels. An experimental version of the circuit has been integrated in a standard double-metal 0.7-μm CMOS process with a die area of only 140×100 μm2. Operating under a 5-V power supply, this circuit identifies the read-out current of a memory cell, and associates it with the appropriate logic level in 9 ns 相似文献