全文获取类型
收费全文 | 764篇 |
免费 | 31篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 183篇 |
金属工艺 | 13篇 |
机械仪表 | 16篇 |
建筑科学 | 22篇 |
能源动力 | 30篇 |
轻工业 | 41篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 116篇 |
一般工业技术 | 140篇 |
冶金工业 | 91篇 |
原子能技术 | 4篇 |
自动化技术 | 121篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 20篇 |
2021年 | 29篇 |
2020年 | 14篇 |
2019年 | 14篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 29篇 |
2015年 | 26篇 |
2014年 | 42篇 |
2013年 | 53篇 |
2012年 | 33篇 |
2011年 | 54篇 |
2010年 | 35篇 |
2009年 | 33篇 |
2008年 | 41篇 |
2007年 | 38篇 |
2006年 | 34篇 |
2005年 | 23篇 |
2004年 | 31篇 |
2003年 | 26篇 |
2002年 | 13篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 17篇 |
1997年 | 21篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 10篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1976年 | 14篇 |
1975年 | 3篇 |
1972年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有795条查询结果,搜索用时 15 毫秒
91.
J L Willems P Arnaud J H van Bemmel P J Bourdillon R Degani B Denis F M Harms P W Macfarlane G Mazzocca J Meyer 《Computers and biomedical research》1985,18(5):439-457
As a result of an international cooperative project entitled "Common Standards for Quantitative Electrocardiography" (CSE), an ECG reference data base has been established with the aim of standardizing computer-derived ECG measurements. The objective of the project is to reduce the wide variation in wave measurements currently obtained by ECG analysis programs. A library of 250 ECGs with selective ECG abnormalities was established and a comprehensive reviewing scheme was devised for the visual determination of the onsets and offsets of P, QRS, and T. This task was performed by a board of cardiologists on highly amplified, selected complexes from the library. A subset was examined in order to study beat-to-beat and intraobserver variability. By using a modified Delphi approach, individual outlying point estimates were eliminated in four successive rounds. In this way final referee estimates were obtained which proved to be highly reproducible and precise. A reference library has thereby been developed which allows testing of the performance of ECG measurement programs and is a useful instrument in establishing recommendations for more precise measurement rules and definitions. 相似文献
92.
The success of several constraint-based modeling languages such as OPL, ZINC or COMET, appeals for better software engineering
practices, particularly in the testing phase. This paper introduces a testing framework enabling automated test case generation
for constraint programming. We propose a general framework of constraint program development which supposes that a first declarative
and simple constraint model is available from the problem specifications analysis. Then, this model is refined using classical
techniques such as constraint reformulation, surrogate, redundant, implied, global constraint and symmetry-breaking to form
an improved constraint model that must be thoroughly tested before being used to address real-sized problems. We think that
most of the faults are introduced in this refinement step and propose a process which takes the first declarative model as
an oracle for detecting non-conformities and derive practical test purposes from this process. We implemented this approach
in a new tool called CPTEST that was used to automatically detect non-conformities on classical benchmark programs, such as the Golomb rulers, n-queens,
social golfer and the car-sequencing problems. 相似文献
93.
Peter Kuczynski Arnaud Rigoll Wolfgang H. Gerstacker Johannes B. Huber 《AEUE-International Journal of Electronics and Communications》2004,58(4):256-267
In this paper, a Hidden Markov Modeling (HMM) technique for a fast and accurate simulation of bit errors and soft outputs in wireless communication systems is presented. HMMs with continuous probability distributions are considered. Soft outputs and bit errors are combined to error patterns. We focus on binary phase–shift keying (BPSK) modulation for direct–sequence spread spectrum (code–division multiple access, CDMA) transmission as proposed e.g. for the third generation wireless communication system UMTS (uplink for the frequency division duplex mode (FDD)). Comparisons of simulated bit error rates for HMM models and Rake receivers are shown for AWGN, flat fading, and vehicular channel conditions. In order to assess the ability of the HMM to describe the dynamical behaviour of the channel a comparison for transmission with interleaving and convolutional coding is presented. Furthermore calculated autocorrelation functions of the error patterns and error gap distributions corresponding to the Rake receiver and to the HMM, respectively, are presented. Our investigations show a strong dependence of the required HMM order on Eb/N0 and the channel conditions. The degree of accordance of the HMM outputs and the training data is examined based on calculated statistical scoring indicators. 相似文献
94.
OBJECTIVE: The purpose of our prospective study was to evaluate the contribution of follow-up in resected colorectal cancer. METHODS: One-thousand patients with colorectal adenocarcinoma who underwent radial resection from January 1975 to January 1990 were prospectively divided into two groups: the first group (n = 442, 42%) entered a 5-year follow-up protocol and the second group (n = 558, 56%) was free to make unscheduled visits in case of symptoms. RESULTS: Recurrence was found in 31.5% of the patients in the first group compared with 33% in the second group. Chorioembryonic antigen was the most accurate test detecting recurrence: 77% of the cases (97% for hepatic metastasis). Surgical resection of recurrent tumors was performed in 37% of the group 1 patients (curative resection in 15%) and in 9% (curative resection in 1.5%) of the group 2 patients (p < 0.001). 5-year survival after recurrence in group 1 was 11.5% versus 1% in group 2 (p < 0.01). CONCLUSION: These results emphasize the rational for a follow-up program in patients undergoing surgery for colorectal cancer. 相似文献
95.
The operation of graded-index fibres can be optimised in the neighbourhood of some wavelength whenever two dopants are available. Under the assumption that the index is a linear function of the dopant concentrations, a class of relations between dopants is found, which is related to that given by Olshansky.4 The case of a fibre doped with germanium and fluorine is treated. 相似文献
96.
It is shown experimentally that short samples (about 1 m) of multimode optical fibres can be characterised by measuring the times of flight of tubular modes. There is fair agreement between measured and calculated values. 相似文献
97.
A closed-form expression for pulse broadening in graded-index fibres that have small and circularly symmetric, but otherwise arbitrary, deviations from a square-law, and arbitrary dn/d?, is applied to germania-doped fibres. The range of validity of the theoretical expression is defined by comparison with the results of numerical integration. 相似文献
98.
We analyzed the influence of clinical and psychological factors on the long-term efficacy of botulinum toxin A (BTX) injections in 45 patients with blepharospasm and 66 patients with hemifacial spasm. Injections efficacy (respectively 94.3% and 95.7%) and duration of relief (respectively 14.8 and 18.7 weeks) remained stable over seven successive injections. Clinical improvement was not influenced by patients' sex, age, or disease duration but by psychological background (p < 0.001). Patients who failed to respond after repetitive injections had lower inter-injections intervals (p < 0.05). This data shows: (1) the importance of psychological contexte in subjective evaluation of treatment efficacy with BTX, (2) emphasizes the necessity of avoiding close injections. 相似文献
99.
The spectrum, Sp(), of a sentence is the set of cardinalities of finite structures which satisfy . We prove that any set of integers which is in Func1∞, i.e. in the class of spectra of first-order sentences of type containing only unary function symbols, is also in BIN1, i.e. in the class of spectra of first-order sentences of type involving only a single binary relation.
We give similar results for generalized spectra and some corollaries: in particular, from the fact that the large complexity class cNTIMERAM(cn) is included in Func1∞ for unary languages (n denotes the input integer), we deduce that the set of primes and many “natural” sets belong to BIN1.
We also give some consequences for the image of spectra under polynomials of . 相似文献
100.
RP Bourette S Arnaud GM Myles JP Blanchet LR Rohrschneider G Mouchiroud 《Canadian Metallurgical Quarterly》1998,17(24):7273-7281
The production, survival and function of monocytes and macrophages are regulated by the macrophage colony-stimulating factor (M-CSF or CSF-1) through its tyrosine kinase receptor Fms. Binding of M-CSF results in Fms autophosphorylation on specific tyrosines that act as docking sites for intracellular signaling molecules containing SH2 domains. Using a yeast two-hybrid screen, we cloned a novel adaptor protein which we called 'Mona' for monocytic adaptor. Mona contains one SH2 domain and two SH3 domains related to the Grb2 adaptor. Accordingly, Mona interacts with activated Fms on phosphorylated Tyr697, which is also the Grb2-binding site. Furthermore, Mona contains a unique proline-rich region located between the SH2 domain and the C-terminal SH3 domain, and is apparently devoid of any catalytic domain. Mona expression is restricted to two hematopoietic tissues: the spleen and the peripheral blood mononuclear cells, and is induced rapidly during monocytic differentiation of the myeloid NFS-60 cell line in response to M-CSF. Strikingly, overexpression of Mona in bone marrow cells results in strong reduction of M-CSF-dependent macrophage production in vitro. Taken together, our results suggest an important role for Mona in the regulation of monocyte/macrophage development as controlled by M-CSF. 相似文献