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111.
D. E. Spahr K. Friedrich J. M. Schultz R. S. Bailey 《Journal of Materials Science》1990,25(10):4427-4439
Microstructure and fracture mechanical behaviour of injection-moulded, longer glass fibrereinforced polypropylene (Verton* aspect ratio 320) were studied as a function of fibre volume fraction and compared to that of shorter fibre-filled polypropylene (aspect ratio 70). Toughness was measured using instrumented notched lzod and falling weight impact tests, as well as compact tension specimens. It was found that the addition of longer fibres generally increased the toughness of the material, although more significant increases were seen in the impact tests than were seen in the compact tension test. For the latter results, a correlation between toughness improvement and microstructural details was performed on the basis of the microstructural efficiency concept, a semi-empirical approach of the formK
c,C = (a* +nR)K
c,M, where,K
c,C andK
c,M are the fracture toughnesses of the composite and the matrix, respectively,a* is a matrix stress correction factor,n is a scaling parameter andR is a fibre reinforcement effectiveness factor. The latter corrects for differences in the composite microstructures, and incorporates effective fibre orientation factors, layering of injection moulded parts, and fibre volumes in the different layers.Nomenclature
a
crack length
-
a
*
matrix toughness correction factor
-
A
cross-sectional area
-
B
thickness of the sample plaques
-
C
thickness of the composite core regions
-
E
peak
energy adsorbed up to the maximum force in the impact load-displacement curve
-
E
t
tensile modulus
-
F
max
maximum force in impact force-displacement curves
-
f
p
fibre orientation factor
-
f
pe
effective orientation factor
-
f
pe,C
effective orientation parameter, core region
-
f
pe, s
effective orientation parameter, surface region
-
F
critical load in the tensile test load-displacement curves
-
K
c
critical stress intensity factor/fracture toughness
-
K
L
fracture toughness of the composite materials
-
K
d
dynamic fracture toughness
-
K
L
fracture toughness of the matrix
-
L
test with crack parallel to the mould filling direction
-
M
microstructural efficiency factor
-
n
scaling parameter for reinforcement effectiveness factor (energy absorbtion ratio)
-
R
reinforcement effectiveness factor
-
S
thickness of the composite surface regions
- T
test with crack perpendicular to the mould filling direction
-
V
f
fibre volume fraction
-
V
m
matrix volume fraction (= 1 —V
f)
-
W
specimen width
-
W
f
fibre weight fraction
-
W
m
matrix weight fraction (= 1 —W
f)
-
X
n
number average fibre length
-
X
v
volume average fibre length
-
Y(a/ W)
polynomial correction for compact tension specimens
-
variable in effective orientation factor formula
-
variable in effective orientation factor formula
- B
strain to break
- c
density of the composite
- f
fibre density
- m
matrix density
- F
fracture strength
-
fibre angle with respect to a reference direction 相似文献
112.
113.
Schultz S 《Computers in healthcare》1992,13(13):32-4, 36-7
A group of 60 university hospitals and medical centers has evolved from its original goal of gaining greater purchasing clout to a new goal: The University Hospital Consortium is becoming an information corporation, with the enormous information potential to affect treatment outcomes, practice patterns and clinical research. Sam Schultz, UHC's vice president of Information Services, tells Computers in Healthcare his organization is on the verge of a new age of discovery. 相似文献
114.
Farrukh Aqil Jeyaprakash Jeyabalan Radha Munagala Iqbal Ahmad David J. Schultz Ramesh C. Gupta 《International journal of molecular sciences》2021,22(12)
Breast cancer (BC) is a leading cause of cancer deaths in women in less developed countries and the second leading cause of cancer death in women in the U.S. In this study, we report the inhibition of E2-mediated mammary tumorigenesis by Cuminum cyminum (cumin) administered via the diet as cumin powder, as well as dried ethanolic extract. Groups of female ACI rats were given either an AIN-93M diet or a diet supplemented with cumin powder (5% and 7.5%, w/w) or dried ethanolic cumin extract (1%, w/w), and then challenged with subcutaneous E2 silastic implants (1.2 cm; 9 mg). The first appearance of a palpable mammary tumor was significantly delayed by both the cumin powder and extract. At the end of the study, the tumor incidence was 96% in the control group, whereas only 55% and 45% animals had palpable tumors in the cumin powder and extract groups, respectively. Significant reductions in tumor volume (660 ± 122 vs. 138 ± 49 and 75 ± 46 mm3) and tumor multiplicity (4.21 ± 0.43 vs. 1.16 ± 0.26 and 0.9 ± 0.29 tumors/animal) were also observed by the cumin powder and cumin extract groups, respectively. The cumin powder diet intervention dose- and time-dependently offset E2-related pituitary growth, and reduced the levels of circulating prolactin and the levels of PCNA in the mammary tissues. Mechanistically, the cumin powder diet resulted in a significant reversal of E2-associated modulation in ERα, CYP1A1 and CYP1B1. Further, the cumin powder diet reversed the expression levels of miRNAs (miR-182, miR-375, miR-127 and miR-206) that were highly modulated by E2 treatment. We analyzed the composition of the extract by GC/MS and established cymene and cuminaldehyde as major components, and further detected no signs of gross or systemic toxicity. Thus, cumin bioactives can significantly delay and prevent E2-mediated mammary tumorigenesis in a safe and effective manner, and warrant continued efforts to develop these clinically translatable spice bioactives as chemopreventives and therapeutics against BC. 相似文献
115.
The adhesion energy between silicone rubber and glass has been obtained from the Johnson, Kendall and Roberts' test. The specific effect of ammonia on the quasi-equilibrium value has been studied as a function of the degree of crosslinking of the elastomer. For PDMS networks with lower molecular weight between crosslinks, the effect is more pronounced but completely reversible. This has been related to the increase in the non-dispersive part of the surface energy of the silicone due to the imbibed ammonia. In incompletely crosslinked hydroxyl-terminated PDMS, ammonia has a catalytic effect and is responsible for chemical bonding between the unreacted hydroxyl groups of the PDMS and the hydroxyl groups on glass. 相似文献
116.
A new technique of coherent optics, speckle photography, has been applied to the study of the behavior of adhesive joints under shear stress. This technique allows the determination of the in-plane motion by a point-by-point analysis with a sensitivity of about 3 μm. This property has been used to measure the interfacial displacement of model glass-glass joints bonded by different types of adhesive when submitted to shear. The experimental results permit direct verification of Volkersen's theory as well as the determination of the actual shear modull of the thin adhesive layer. The simplicity of use and interpretation of the technique of speckle photography should lead to significant application of this method in the future for the study of adhesive joints. 相似文献
117.
118.
We present a wearable input system which enables interaction through 3D handwriting recognition. Users can write text in the air as if they were using an imaginary blackboard. The handwriting gestures are captured wirelessly by motion sensors applying accelerometers and gyroscopes which are attached to the back of the hand. We propose a two-stage approach for spotting and recognition of handwriting gestures. The spotting stage uses a support vector machine to identify those data segments which contain handwriting. The recognition stage uses hidden Markov models (HMMs) to generate a text representation from the motion sensor data. Individual characters are modeled by HMMs and concatenated to word models. Our system can continuously recognize arbitrary sentences, based on a freely definable vocabulary. A statistical language model is used to enhance recognition performance and to restrict the search space. We show that continuous gesture recognition with inertial sensors is feasible for gesture vocabularies that are several orders of magnitude larger than traditional vocabularies for known systems. In a first experiment, we evaluate the spotting algorithm on a realistic data set including everyday activities. In a second experiment, we report the results from a nine-user experiment on handwritten sentence recognition. Finally, we evaluate the end-to-end system on a small but realistic data set. 相似文献
119.
Dynamic, in situ wide angle X-ray scattering (WAXS) studies of the melt crystallization of injection-molded poly(ether ether ketone) (PEEK) have been carried out using an X-ray diffractometer and a position-sensitive detector. A test cell has been fabricated to fit inside the diffractometer and yet work as a complete injection molding apparatus. The rate of crystallization has been shown to increase with decreasing crystallization temperature and/or increasing flow rate in the mold. The crystallization rate decreases dramatically with increase in melt soak time at 400°C. The crystallinity index, which affects the stiffness, toughness, and fracture behavior of PEEK, has been measured under various processing conditions, by wide angle X-ray scattering, so as to optimize the process parameters: molding time, mold temperature, melt temperature, soak time at melt temperature, and flow rate. It has been shown that the crystallinity and hence the elastic modulus increase with increase in crystallization temperature and/or flow rate. Chain orientation has been shown to be absent in the bulk of the injection-molded specimens under normal molding conditions. 相似文献
120.
The effect of 2,2′-oxydiethanol (diethylene glycol, DEG) content (ranging from 2 to 15 mol %) and of the annealing temperature (in the range from 100 to 260°C) on the density, calorimetric, dynamic- and static-mechanical and small angle X-ray scattering (SAXS) behavior of undrawn and drawn samples (granules, films, and bristles) of poly(ethylene terephthalate) (PET) has been studied. The known dependences on the annealing temperature are confirmed. Some discrepancies with earlier investigations of the dependences on the DEG content are established: constant values for the SAXS intensity and long spacing, for the lamellar thickness and for the volume fraction crystallinity ac. These discrepancies are explained by the variation of the glass transition temperature (Tg) and melting temperature (Tm) of the materials with different DEG contents. The previous hypothesis of the segregation of the comonomer (DEG) units into the amorphous regions is confirmed. 相似文献