全文获取类型
收费全文 | 13664篇 |
免费 | 338篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 191篇 |
综合类 | 12篇 |
化学工业 | 3015篇 |
金属工艺 | 224篇 |
机械仪表 | 283篇 |
建筑科学 | 644篇 |
矿业工程 | 97篇 |
能源动力 | 375篇 |
轻工业 | 966篇 |
水利工程 | 130篇 |
石油天然气 | 162篇 |
武器工业 | 1篇 |
无线电 | 828篇 |
一般工业技术 | 2001篇 |
冶金工业 | 3309篇 |
原子能技术 | 138篇 |
自动化技术 | 1647篇 |
出版年
2022年 | 116篇 |
2021年 | 168篇 |
2020年 | 143篇 |
2019年 | 159篇 |
2018年 | 180篇 |
2017年 | 178篇 |
2016年 | 203篇 |
2015年 | 164篇 |
2014年 | 225篇 |
2013年 | 806篇 |
2012年 | 440篇 |
2011年 | 617篇 |
2010年 | 398篇 |
2009年 | 434篇 |
2008年 | 560篇 |
2007年 | 546篇 |
2006年 | 536篇 |
2005年 | 444篇 |
2004年 | 360篇 |
2003年 | 357篇 |
2002年 | 370篇 |
2001年 | 235篇 |
2000年 | 229篇 |
1999年 | 247篇 |
1998年 | 212篇 |
1997年 | 228篇 |
1996年 | 237篇 |
1995年 | 240篇 |
1994年 | 243篇 |
1993年 | 290篇 |
1992年 | 245篇 |
1991年 | 184篇 |
1990年 | 201篇 |
1989年 | 214篇 |
1988年 | 169篇 |
1987年 | 214篇 |
1986年 | 203篇 |
1985年 | 247篇 |
1984年 | 223篇 |
1983年 | 201篇 |
1982年 | 180篇 |
1981年 | 189篇 |
1980年 | 161篇 |
1979年 | 179篇 |
1978年 | 180篇 |
1977年 | 136篇 |
1976年 | 142篇 |
1975年 | 172篇 |
1974年 | 133篇 |
1973年 | 132篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
This paper develops a framework for the consideration of internal markets as an alternative to information systems (IS) outsourcing. It is based on an assessment of the pros and cons of both outsourcing and of insourcing based on the internal markets approach. It is formulated in terms of the operational, tactical, and strategic impacts of the choice among the alternatives. The framework, and the propositions that are developed from it, should be useful both for researchers, who can use it for developing testable research hypotheses, and for practitioners, who may use it as a basis for developing a comprehensive set of criteria for the evaluation of these sourcing options. 相似文献
52.
Evans WJ Yoo CS Lee GW Cynn H Lipp MJ Visbeck K 《The Review of scientific instruments》2007,78(7):073904
We have developed a unique device, a dynamic diamond anvil cell (dDAC), which repetitively applies a time-dependent load/pressure profile to a sample. This capability allows studies of the kinetics of phase transitions and metastable phases at compression (strain) rates of up to 500 GPa/s (approximately 0.16 s(-1) for a metal). Our approach adapts electromechanical piezoelectric actuators to a conventional diamond anvil cell design, which enables precise specification and control of a time-dependent applied load/pressure. Existing DAC instrumentation and experimental techniques are easily adapted to the dDAC to measure the properties of a sample under the varying load/pressure conditions. This capability addresses the sparsely studied regime of dynamic phenomena between static research (diamond anvil cells and large volume presses) and dynamic shock-driven experiments (gas guns, explosive, and laser shock). We present an overview of a variety of experimental measurements that can be made with this device. 相似文献
53.
We show that it is possible to collect data that are useful for collaborative filtering (CF) using an autonomous Web spider. In CF, entities are recommended to a new user based on the stated preferences of other, similar users. We describe a CF spider that collects from the Web lists of semantically related entities. These lists can then be used by existing CF algorithms by encoding them as ‘pseudo-users'. Importantly, the spider can collect useful data without pre-programmed knowledge about the format of particular pages or particular sites. Instead, the CF spider uses commercial Web-search engines to find pages likely to contain lists in the domain of interest, and then applies previously proposed heuristics to extract lists from these pages. We show that data collected by this spider are nearly as effective for CF as data collected from real users, and more effective than data collected by two plausible hand-programmed spiders. In some cases, autonomously spidered data can also be combined with actual user data to improve performance. 相似文献
54.
William M. Fawley 《Journal of Fusion Energy》1991,10(4):299-300
Induction Linac Systems Experiments is the next experiment planned by the Heavy Ion Fusion Accelerator Research (HIFAR) group at LBL, following the recent completion of the MBE-4 experiment. ILSE at 10 MeV will address many of the key physics and technology issues of HIF such as performance of a multiple beam, high voltage injector, high intensity electrostatically-focused transport, beam combining, high intensity magnetically-focused transport, drift-compression and energy-tilt removal, high intensity transport around a magnetic bend, and, possibly, recirculation. Presuming a new start in FY 94, experiments could begin with ILSE in FY 97. 相似文献
55.
56.
William McBride 《Particulate Science and Technology》2006,24(1):59-70
The ability of a granular bulk material to transmit internal shear stress is a fundamental property that is often overlooked or underestimated, yet it is this ability that allows many observed physical phenomena to occur. One such area that continues to be a focus for numerical, theoreticals and experimental researchers is the pressure that a stockpile of granular material places on the supporting surface. While appearing to be a simple problem, the ability of granular materials to transmit shear stress makes this an extremely complex problem. This article presents high-quality data collected under a 2 m high stockpile and full details of the experimental facilities used in the collection of the data.
The work presented is of significant value, having a much greater scale than previous studies (Jotaki & Moriyama, 1979; Lee & Herington, 1971; Smid & Novosad, 1981), and the deliberate inclusion of a central reclaim channel offers insight into stress changes during gravity reclaim and refilling. The results of this work have shown that the so-called 'M' pressure does exist under larger stockpiles both with and without reclaim hoppers; of more significance is the reemergence of the M pressure upon refilling of an emptied stockpile. This clearly illustrates that the M pressure is a robust and natural pressure distribution for a conical stockpile. 相似文献
The work presented is of significant value, having a much greater scale than previous studies (Jotaki & Moriyama, 1979; Lee & Herington, 1971; Smid & Novosad, 1981), and the deliberate inclusion of a central reclaim channel offers insight into stress changes during gravity reclaim and refilling. The results of this work have shown that the so-called 'M' pressure does exist under larger stockpiles both with and without reclaim hoppers; of more significance is the reemergence of the M pressure upon refilling of an emptied stockpile. This clearly illustrates that the M pressure is a robust and natural pressure distribution for a conical stockpile. 相似文献
57.
Zheng Zhang Nuri William Emanetoglu Gaurav Saraf Yimin Chen Pan Wu Jian Zhong Yicheng Lu Jingqiu Chen Oleg Mirochnitchenko Masayori Inouye 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(4):786-792
DNA immobilization enhancement is demonstrated in a structure consisting of ZnO nanotips on 128 degrees Y-cut LiNbO3. The ZnO nanotips are grown by metalorganic chemical vapor deposition (MOCVD) on the top of a SiO2 layer that is deposited and patterned on the LiNbO3 SAW delay path. The effects of ZnO nanotips on the SAW response are investigated. X-ray diffraction and scanning electron microscopy are used to analyze the ZnO nanotips, which are of single crystalline quality, and they are uniformly aligned with their c-axis perpendicular to the substrate surface. The photoluminescence (PL) spectrum of the ZnO nanotips shows strong near bandedge transition with insignificant deep level emission, confirming their good optical property. DNA immobilization enhancement is experimentally validated by radioactive labeling tests and SAW response changes. The ZnO nanotips enhance the DNA immobilization by a factor of 200 compared to ZnO film with flat surface. DNA hybridization with complementary and noncomplementary second strand DNA oligonucleotides is used to study the selective binding of the structure. This device structure possesses the advantages of both traditional SAW sensors and ZnO nanostructures. 相似文献
58.
Lutz Wolfgang; Leach Chris; Barkham Michael; Lucock Mike; Stiles William B.; Evans Chris; Noble Rachael; Iveson Steve 《Canadian Metallurgical Quarterly》2005,73(5):904
This study extended client-focused research by using the nearest neighbor (NN) approach, a client-specific sampling and prediction strategy derived from research on alpine avalanches. Psychotherapy clients (N = 203) seen in routine practice settings in the United Kingdom completed a battery of intake measures and then completed symptom intensity ratings before each session. Forecasts of each client's rate of change and session-by-session variability were computed on the basis of that client's NNs (n = 10-50 in different comparisons). Alternative forecasts used linear or log-linear slopes and were compared with an alternative prediction strategy. Results showed that the NN approach was superior to the alternative model in predicting rate of change, though the advantage was less clear for predicting variability. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
59.
Robust Estimation of Rotation Angles from Image Sequences Using the Annealing M-Estimator 总被引:1,自引:0,他引:1
A robust method is presented for computing rotation angles of image sequences from a set of corresponding points containing outliers. Assuming known rotation axis, a least-squares (LS) solution are derived to compute the rotation angle from a clean data set of point correspondences. Since clean data is not guaranteed, we introduce a robust solution, based on the M-estimator, to deal with outliers. Then we present an enhanced robust algorithm, called the annealing M-estimator (AM-estimator), for reliable robust estimation. The AM-estimator has several attractive advantages over the traditional M-estimator: By definition, the AM-estimator involves neither scale estimator nor free parameters and hence avoids instabilities therein. Algorithmically, it uses a deterministic annealing technique to approximate the global solution regardless of the initialization. Experimental results are presented to compare the performance of the LS, M- and AM-estimators for the angle estimation. Experiments show that in the presence of outliers, the M-estimator outperforms the LS estimator and the AM-estimator outperforms the M-estimator. 相似文献
60.
John E. Rash Timothy J. A. Johnson C. Sue Hudson F. Dennis Giddings William F. Graham Mohyee E. Eldefrawi 《Journal of microscopy》1982,128(2):121-138
Three methods are described for direct post-fracture, post-shadow labelling of individual classes of intramembrane particles (IMPs) in freeze-fracture replicas of biological membranes. The P-face IMPs corresponding to the acetylcholine receptor complexes (AChRs) of vertebrate neuroeffector junctions are identified by post-replication labelling with ferritin-antibody complexes and with neurotoxin-biotin-avidin-colloidal gold affinity ligands. (The freeze-etch nomenclature of Branton et al., 1975, is used in this report.) These post-shadow labelling techniques resemble conventional en bloc labelling techniques except that the labelling reagents must penetrate a thin but discontinuous layer of platinum superimposed on the molecules of interest. In the ‘sectioned labelled-replica technique’, the replicated and labelled tissues are stained, embedded in plastic and sectioned parallel to the replica-tissue interfaces. In the direct ‘labelled-replica techniques’, the replicated and labelled samples are freeze-dried or critical point dried, the labelled surfaces are stabilized by carbon coating, and the underlying tissues are dissolved, allowing the labelled-replicas to be examined as conventional freeze-fracture replicas. The unshadowed side of each AChR IMP is shown to retain sufficient biochemical information to permit both immunospecific and neurotoxin specific labelling despite formaldehyde fixation, freezing, fracturing, platinum shadowing, and thawing in aqueous media. A new mixed ferricyanide-osmium staining method reveals electron opaque structures spanning the membrane bilayer in the same size, number and distribution as the labelled IMPs. These experiments demonstrate the feasibility of identifying individual IMPs in freeze-fracture replicas and may allow the identification of specific membrane lesions in human disease. 相似文献