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M Hartmann O Jansen T Egelhof M Forsting FK Albert K Sartor 《Canadian Metallurgical Quarterly》1998,38(11):948-953
PURPOSE: To assess the influence of initial preoperative brain edema in malignant gliomas on regrowth patterns. SUBJECTS AND METHODS: 79 patients with histologically verified supratentorial malignant glioma were prospectively studied by magnetic resonance imaging (MRI) before and every 2-3 months after surgery. The median follow-up time was 11 months. We correlated the configuration of the initial vasogenic edema on T2-weighted images with tumor regrowth patterns on contrast-enhanced T1-weighted images. RESULTS: 35/47 tumor regrowths (75%) imitated the initial edema configuration, while 11/47 occurred within the initial tumor bed; in one case tumor recurrence was multilocal. CONCLUSION: In glioblastoma, tumor regrowth patterns correlate positively with the configuration of the initial vasogenic brain edema. The initial, "presurgical" peritumoral edema should thus be considered when planning further treatment. 相似文献
54.
Ron Koster Albert C. Van der Woerd Wouter A. Serdijn Jan Davidse Arthur H. M. Van Roermund 《Analog Integrated Circuits and Signal Processing》1996,9(3):207-214
In this paper design rules for a circuit topology in which there is an inseparable combination of an amplifier and a filter characteristic, are presented. By intentionally using the capacitance of an already present input sensor for the filtering, the total required integrated capacitance is much less than that in circuits, which have a separately designed amplifier and filter function. Consequently, it is possible to have the advantage of a better integratability. Moreover, less complexity in the design is achieved. The presented circuit shows a current-to-voltage conversion and an inherently controllable second-order low-pass filter characteristic. A discrete realization has been designed to test the circuit. This circuit operates down to a 1 V supply voltage and the transfer shows a 1.8 M currentto-voltage conversion with a bandwidth of 6 kHz. Measurement results of this circuit show that a 63 dB dynamic range can be achieved with a total required integrated capacitance of only 31 pF. 相似文献
55.
Behnke B Schlotterbeck G Tallarek U Strohschein S Tseng LH Keller T Albert K Bayer E 《Analytical chemistry》1996,68(7):1110-1115
Coupling HPLC and NMR is one of the most powerful techniques for simultaneous separation and structural elucidation of unknown compounds in mixtures. To date, however, minimizing the detection volume, as is required when coupling NMR with miniaturized separation techniques, has been accompanied by a dramatic loss in resolution of the NMR spectra. Here, we report on the coupling of gradient capillary HPLC with on-column, high-resolution NMR detection. On-line stopped-flow and static (1)H NMR spectra were acquired with capillary columns of 75-315 μm i.d. With detection over a length of 1.2 cm, cell volumes cover a range of 50-900 nL. An on-line-detected NMR separation of dansylated amino acids was carried out in a 315 μm i.d. fused silica capillary packed to a length of 12 cm with C(18) stationary phase. The low solvent consumption makes the use of fully deuterated solvents economically feasible. NMR spectra with resolution on the order of 3 Hz were obtained using a 50 nL detection cell to measure 1.1 nmol of dansylated γ-aminobutyric acid under static conditions in a 75 μm i.d. capillary. 相似文献
56.
A SIMD-efficient 14 instruction shader program for high-throughput microtriangle rasterization 总被引:1,自引:0,他引:1
Jordi Roca Victor Moya Carlos Gonzalez Vicente Escandell Albert Murciego Agustin Fernandez Roger Espasa 《The Visual computer》2010,26(6-8):707-719
This paper shows that breaking the barrier of 1 triangle/clock rasterization rate for microtriangles in modern GPU architectures in an efficient way is possible. The fixed throughput of the special purpose culling and triangle setup stages of the classic pipeline limits the GPU scalability to rasterize many triangles in parallel when these cover very few pixels. In contrast, the shader core counts and increasing GFLOPs in modern GPUs clearly suggests parallelizing this computation entirely across multiple shader threads, making use of the powerful wide-ALU instructions. In this paper, we present a very efficient SIMD-like rasterization code targeted at very small triangles that scales very well with the number of shader cores and has higher performance than traditional edge equation based algorithms. We have extended the ATTILA GPU shader ISA (del Barrioet al. in IEEE International Symposium on Performance Analysis of Systems and Software, pp. 231–241, 2006) with two fixed point instructions to meet the rasterization precision requirement. This paper also introduces a novel subpixel Bounding Box size optimization that adjusts the bounds much more finely, which is critical for small triangles, and doubles the 2×2-pixel stamp test efficiency. The proposed shader rasterization program can run on top of the original pixel shader program in such a way that selected fragments are rasterized, attribute interpolated and pixel shaded in the same pass. Our results show that our technique yields better performance than a classic rasterizer at 8 or more shader cores, with speedups as high as 4× for 16 shader cores. 相似文献
57.
Extracting reliable image edge information is crucial for active contour models as well as vascular segmentation in magnetic
resonance angiography (MRA). However, conventional edge detection techniques, such as gradient-based methods and wavelet-based
methods, are incapable of returning reliable detection responses from low contrast edges in the images. In this paper, we
propose a novel edge detection method by combining B-spline wavelet magnitude with standard deviation inside local region.
It is proved theoretically and demonstrated experimentally in this paper that the new edge detection method, namely BWLSD,
is able to give consistent and reliable strengths for edges with different image contrasts. Moreover, the relationship between
the size of local region with non-zero wavelet magnitudes and the scale of wavelet function is established. This relationship
indicates that if the scale of the adopted wavelet function is s, then the size of a local region, from which the standard deviation is estimated, should be 2s−1. The proposed edge detection technique is embedded in FLUX, namely, BWLSD-FLUX, for vascular segmentation in MRA image
volumes. Experimental results on clinical images show that, as compared with the conventional FLUX, BWLSD-FLUX can achieve
better segmentations of vasculatures in MRA images under same initial conditions. 相似文献
58.
We propose and study quantitative measures of smoothness f ? A(f) which are adapted to anisotropic features such as edges in images or shocks in PDE’s. These quantities govern the rate of approximation by adaptive finite elements, when no constraint is imposed on the aspect ratio of the triangles, the simplest example being \(A_{p}(f)=\|\sqrt{|\mathrm{det}(d^{2}f)|}\|_{L^{\tau}}\) which appears when approximating in the L p norm by piecewise linear elements when \(\frac{1}{\tau}=\frac{1}{p}+1\). The quantities A(f) are not semi-norms, and therefore cannot be used to define linear function spaces. We show that these quantities can be well defined by mollification when f has jump discontinuities along piecewise smooth curves. This motivates for using them in image processing as an alternative to the frequently used total variation semi-norm which does not account for the smoothness of the edges. 相似文献
59.
60.
Albert A. Groenwold L. F. P. Etman Derren W. Wood 《Structural and Multidisciplinary Optimization》2010,41(1):39-56
We propose to replace a number of popular approximations by their diagonal quadratic Taylor series expansions. The resulting
separable quadratic approximations are easily convexified, and are well suited for use in dual sequential approximate optimization
(SAO) algorithms. Global convergence of the resulting SAO algorithms may be enforced in a natural way using conservatism.
The approximated approximation approach is explicitly illustrated for (i) reciprocal and exponential intervening variables,
(ii) the intervening variables used in the method of moving asymptotes (MMA), (iii) the intervening variables used in CONLIN,
and (iv) the TANA-3 approximations. The use of intermediate responses for use in, for example, truss and frame-like structures,
is also discussed. Key advantages of replacing nonlinear approximations by their diagonal quadratic approximations are that
these approximated approximations can all be used simultaneously in a single dual statement; the dual does not depend on the form of the original approximations. In addition, in a dual setting, the resulting subproblems
yield simple analytical relationships between the primal and dual variables, which is often not the case with the original
nonlinear approximations. An important example hereof is the exponential approximation. Although the diagonal quadratic approximations
may differ notably from their original counterparts, they typically are quite similar in a sufficiently small search subregion,
which relates to the move limits commonly used in SAO anyway. 相似文献