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排序方式: 共有3237条查询结果,搜索用时 11 毫秒
891.
Lulu Jia Hairong Xue Fang Xian Yoshiyuki Sugahara Nobuyuki Sakai Jingbo Nan Yusuke Yamauchi Takayoshi Sasaki Renzhi Ma 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(42):2303221
The design and development of efficient catalysts for electrochemical nitrogen reduction reaction (ENRR) under ambient conditions are critical for the alternative ammonia (NH3) synthesis from N2 and H2O, wherein iron-based electrocatalysts exhibit outstanding NH3 formation rate and Faradaic efficiency (FE). Here, the synthesis of porous and positively charged iron oxyhydroxide nanosheets by using layered ferrous hydroxide as a starting precursor, which undergoes topochemical oxidation, partial dehydrogenated reaction, and final delamination, is reported. As the electrocatalyst of ENRR, the obtained nanosheets with a monolayer thickness and 10-nm mesopores display exceptional NH3 yield rate (28.5 µg h−1 mgcat.−1) and FE (13.2%) at a potential of −0.4 V versus RHE in a phosphate buffered saline (PBS) electrolyte. The values are much higher than those of the undelaminated bulk iron oxyhydroxide. The larger specific surface area and positive charge of the nanosheets are beneficial for providing more exposed reactive sites as well as retarding hydrogen evolution reaction. This study highlights the rational control on the electronic structure and morphology of porous iron oxyhydroxide nanosheets, expanding the scope of developing non-precious iron-based highly efficient ENRR electrocatalysts. 相似文献
892.
Hirohiko Fukagawa Munehiro Hasegawa Katsuyuki Morii Kazuma Suzuki Tsubasa Sasaki Takahisa Shimizu 《Advanced materials (Deerfield Beach, Fla.)》2019,31(43)
Molecular n‐dopants that can lower the electron injection barrier between organic semiconductors and electrodes are essential in present‐day organic electronics. However, the development of stable molecular n‐dopants remains difficult owing to their low ionization potential, which generally renders them unstable. It is shown that the stable bases widely used in organic synthesis as catalysts can lower the electron injection barrier similar to that in conventional n‐doping in organic optoelectronic devices. In contrast to conventional n‐doping, which is based on the electron transfer from dopants with low ionization potential, the reduction of the injection barrier caused by adding bases is determined by the formation of hydrogen bonds between the hosts and the bases, providing energy‐level‐independent electron injection. The observation of the efficient electron injection induced by hydrogen bonding affords new perspectives on the method for controlling the behavior of electrons unique to organic semiconductors. 相似文献
893.
For measurements of the total hemispherical emittance
h
of nonconducting materials, a problem of the thermal gradient produced in a sample specimen arises. An improved transient calorimetric technique to reduce the thermal gradient is proposed in this study. Glass sheets (borosilicate), semi-transparent for radiation, are selected as the nonconducting test material. The
h
values of the glass sheets for various thicknesses are measured, and their results are presented as functions of thickness and temperature. The thermal gradients in the specimens are calculated by a three-dimensional analysis, and the corner effect due to them on the measured
h
is estimated. It is shown that the proposed technique is useful for measuring the emittance
h
of nonconducting materials. 相似文献
894.
A new method was developed to produce tensile specimens with pre-machined holes for superplastic zirconia ceramics. Tensile specimens with effective hole sizes of 450 m were successfully produced using graphite fibers. Although the size of the defect introduced is relatively large compared to the grain size enough deformation is obtained for qualitative and quantitative analysis for Y-TZP. 3Y-TZP and 3Y-TZP co-doped with germanium and titanium oxide revealed cavity growth coefficients that varied with strain rate and temperature, unlike metals, as a direct consequence of grain growth induced strain hardening. 相似文献
895.
C. C. Silva A. G. Pinheiro S. D. Figueiró J. C. Góes J. M. Sasaki M. A. R. Miranda A. S. B. Sombra 《Journal of Materials Science》2002,37(10):2061-2070
In this paper we did a study of the physicochemical, dielectric and piezoelectric properties of anionic collagen and collagen-hydroxyapatite (HA) composites, considering the development of new biomaterials which have potential applications in support for cellular growth and in systems for bone regeneration. The piezoelectric strain tensor element d
14, the elastic constant s
55, and the dielectric permittivity 11 were measured for the anionic collagen and collagen-HA films. For the collagen-HA composite film (Col-HACOM) the main peaks associated to the crystalline HA is present. For the nanocrystalline composite, nanometric HA powder (103 nm particle size) (HAN), obtained by mechanical milling were used. For the composite film (Col-HAN) the HA and CaH(PO4)2H2O phases were detected. One can see that the HA powder (HAN) present the main peaks associated to crystalline HA. The IR spectroscopy measurements on HA-COM and HAN powders, Col-HACOM and Col-HAN composite films and collagen film (Col) presents the main resonances associated to the modes of (PO4)3–, (CO3)2–. The IR spectra of Collagen Film (Col) shows the bands associated to amide I (C=O), amide II (N–H) and amide III (C–N) vibrational modes. The scanning electron photomicrography of the Col-HACOM and Col-HAN films, respectively, shows deposits of HA on the surface of collagen. It also shows that HACOM crystals has a dense feature, whereas the HAN crystals has soft porous surface. Energy-dispersive spectroscopy (EDS) analysis showed that the main elements of the hybrid sponge were carbon, oxygen, calcium, and phosphorus. The EDS of HACOM crystal, present in the Col-HACOM composite showed a molar ratio Ca/P = 1.71, whereas the Col-HAN composite the molar ratio of calcium and phosphorus (Ca/P = 2.14) and the amount of carbon were greater. The piezoelectric strain tensor element d
14 obtained for the anionic collagen was around 0.102 pC/N. The collagen composite with nanocrystalline HA crystals (Col-HAN) present a better result (d
14 = 0.040 pC/N) compared to the composite with the commercial ceramic (d
14 = 0.012 pC/N). This is an indication that the nanometric particles of HA present little disturbance on the organization of the collagen fibers in the composite. In this situation the nanometric HA are the best candidates in future applications of these composites. 相似文献
896.
897.
T Morimoto S Uchida H Sakamoto Y Kondo H Hanamizu M Fukui Y Tomino N Nagano S Sasaki F Marumo 《Canadian Metallurgical Quarterly》1998,9(5):811-818
It was hypothesized based on previous laboratory observations and theoretical concepts that astronauts working at the "Mir" station under zero gravity conditions exhibit enhanced sensitivity to geomagnetic disturbances. The result of studies made it possible to reveal the dynamics of changes in cardiovascular characteristics separately in the main phase and the phase of storm restoration. A similar dynamics of cardiac activity was observed in experimental rabbits during geomagnetic storms. 相似文献
898.
N. Yorino A. Funahashi H. Sasaki F.D. Galiana 《International Journal of Electrical Power & Energy Systems》1997,19(8):541-548
The on-load tap-changer (OLTC) is one of the major elements participating in voltage instability. To assess unstable behavior of OLTC, that is, the reverse control action, the sensitivity of load voltage to tap position, dv/ dn, is investigated in two different situations: One is a realistic situation where the exact load characteristics including voltage dependence are used to compute dv/dn. The other is the more ideal situation where dv/dn is calculated assuming constant power loads. It is demonstrated that both sensitivities can be used to assess the occurrence of reverse control action. Line and transformer reactances are the most important factors affecting this condition. The validity of these results is verified through numerical simulations where the dynamic characteristics of OLTC and time varying loads with static nonlinear voltage dependence are taken into account. 相似文献
899.
Hitoshi Yamasaki Yosuke Sasaki Takayoshi Shoudai Tomoyuki Uchida Yusuke Suzuki 《Machine Learning》2009,76(1):137-173
Recently, due to the rapid growth of electronic data having graph structures such as HTML and XML texts and chemical compounds,
many researchers have been interested in data mining and machine learning techniques for finding useful patterns from graph-structured
data (graph data). Since graph data contain a huge number of substructures and it tends to be computationally expensive to
decide whether or not such data have given structural features, graph mining problems face computational difficulties. Let
be a graph class which satisfies a connected hereditary property and contains infinitely many different biconnected graphs,
and for which a special kind of the graph isomorphism problem can be computed in polynomial time. In this paper, we consider
learning and mining problems for
. Firstly, we define a new graph pattern, which is called a block preserving graph pattern (bp-graph pattern) for
. Secondly, we present a polynomial time algorithm for deciding whether or not a given bp-graph pattern matches a given graph
in
. Thirdly, by giving refinement operators over bp-graph patterns, we present a polynomial time algorithm for finding a minimally
generalized bp-graph pattern for
. Outerplanar graphs are planar graphs which can be embedded in the plane in such a way that all of vertices lie on the outer
boundary. Many pharmacologic chemical compounds are known to be represented by outerplanar graphs. The class of connected
outerplanar graphs
satisfies the above conditions for
. Next, we propose two incremental polynomial time algorithms for enumerating all frequent bp-graph patterns with respect
to a given finite set of graphs in
. Finally, by reporting experimental results obtained by applying the two graph mining algorithms to a subset of the NCI dataset,
we evaluate the performance of the two graph mining algorithms. 相似文献
900.
Changes in contractile force were measured during isometric contraction of the bovine middle cerebral artery caused by stimulation of various receptors and by application of high K+, caffeine, and protein kinase C (PKC)-activators. The protein tyrosine kinase (PTK)-inhibitors, such as genistein and tyrphostin, were applied before testing the effect on the contractions or during the maximal plateau of the contraction. The contractions induced by serotonin, prostaglandin F2 alpha, endothelin-1, and thromboxane A2 were significantly and dose-dependently depressed by the PTK-inhibitors (IC50 2-15 microM). In contrast, contractions were significantly augmented by 1 microM pervanadate, an inhibitor of phosphoprotein tyrosine phosphatase. Lineweaver-Burk plotting of the dose-response curves with an increase in inhibitor concentration indicated that the receptor affinity for each agonist remained unchanged in spite of marked depression of the responses. Although the effect was not significant, contractions induced by both high K+ and caffeine were also depressed slightly by PTK-inhibitors in the same range of concentrations used for receptor-induced contractions. Contractions induced by PKC-activators, such as 1-oleoyl-2-acetyl-sn-glycerol and phorbol-12,13-diacetate, were significantly depressed by PTK-inhibitors at concentrations similar to those used for receptor-induced contractions. The results suggest that receptor stimulations which produce sequential activation of phospholipase C and PKC can activate PTK and trigger the so-called "PTK-cascade" causing a sustained or long-lasting contraction similar to the cerebral vasospasm observed clinically. 相似文献