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991.
H Villalobos ES Canales A Zárate J Soria C MacGregor 《Canadian Metallurgical Quarterly》1976,83(2):236-242
Serum levels of prolactin (PRL), FSH, LH and oestradiol-17 beta were determined by radioimmunoassay in 57 lactating women and in 20 women in whom lactation was inhibited by ergocryptine (CS-154). Women who breast fed their infants exhibited high PRL levels which abruptly declined within 48 h post-partum, and remained low for the duration of the study. Serum FSH was undetectable during the first week post-partum in lactating as well as in CB-154 treated women. Thereafter, lactating women showed increasing FSH levels which reached a maximum by the third week post-partum. These FSH values were higher in lactating women than in the CBS-154 treated group. In contrast, LH levels were higher in those women receiving CB-154. Serum oestradiol-17 beta remained in low levels throughout the study, and no difference was observed between the two groups of subjects. From these results it seems that: 1) inhibition of PRL secretion leads to a faster recovery of gonadotrophin secretion toward the "menstrual type", and 2) PRL suppression produces no effect on the ovarian oestrogen production. 相似文献
992.
G. Morell A. González-Berríos B. R. Weiner S. Gupta 《Journal of Materials Science: Materials in Electronics》2006,17(6):443-451
The synthesis and properties of sulfur-doped nanocrystalline diamond films were investigated. The films were deposited by
hot-filament chemical vapor deposition on Mo substrates using methane, hydrogen, and hydrogen disulfide. The nanocrystalline
nature of the material arises from the induction of continuous secondary nucleation in the chemical vapor deposition environment.
Complementary characterization tools were employed in order to obtain a comprehensive and coherent understanding of the correlations
between the structural and electronic properties. In particular, sulfur-doped nanocrystalline diamond films show n-type Hall
conductivity, enhanced field emission properties, and insensitivity to ion radiation. It was found that n-type doping of the
tetragonally-bonded carbon matrix together with a nano network of trigonally-bonded carbon are crucial elements for enhanced
field emission from nanocrystalline diamond. These conclusions and the corresponding supporting evidence are discussed. 相似文献
993.
Scientific
activity has been increasing in Puerto Rico in recent years, a development
mirrored not only by the amount of papers published, but by the international
links established for scientific co-operation. The purpose of the present study
is to identify and discuss the patterns of such co-operation, along with the
trends in scientific research conducted in that context at Puerto Rican
institutions. The methodology includes an analysis of the main areas of
research addressed, defined as the area of specialization of the journals
publishing papers indexed in the Science Citation Index (CD-ROM version) from
1980 to 1999. A total of 7271 studies, appearing in 1240 scientific journals,
were selected to study the co-operation established between Puerto Rican institutions
and organizations in other countries. The findings showed a high rate of
international co-operation: 46.07% of the papers published were co-authored by
researchers from other countries. The country accounting for the highest
percentage of joint research was the USA, followed by Germany, United Kingdom,
Canada and Italy. The close relationship between the Puerto Rican and US
scientific systems is not unusual, inasmuch as the economic and socio-political
bonds between them play an essential role in Puerto Rican scientific activity.
The results also revealed substantial differences between the nineteen eighties
and the nineties in terms of the nature of the links established, as well as
growing internationalization of scientific research conducted on the island
over the twenty-year period studied. 相似文献
994.
Stones belong to porous materials where water in pores plays an important role during the freeze–thaw process. A thermophysical analysis based on the pulse transient method has been used to study an ageing cycle, namely the freeze–thaw cycle. Thermophysical analysis is based on measuring the thermophysical properties under specific thermodynamic conditions. The transient method determines the specific heat, thermal diffusivity, and thermal conductivity by a single measurement. A specimen of Sander sandstone was analyzed in both dry and water-saturated states. Typical anomalies of all thermophysical parameters at the freeze–thaw point as well as differences for the dry and saturated states were found. The changes of thermophysical parameters measured when using freeze–thaw cycles correspond to stone ageing. The freeze–thaw cycle can often be encountered in building physics, concrete construction, etcPaper presented at the Seventh Asian Thermophysical Properties Conference, August 23–28, 2004, Hefei and Huangshan, Anhui, P. R. China. 相似文献
995.
Four low alloy steels with different contents of molybdenum and vanadium were investigated. The steels were annealed at 773,
793, 853, 873, 933, 973, and 993 K for 500, 1000, 3000, and 10000 h. Techniques of transmission electron microscopy and thermodynamic
calculations (ThermoCalc) were used to characterise influence of the steel bulk composition and the annealing conditions on
evolution of carbides M3C, M2C, M7C3, M23C6, M6C, and MC (M=metallic element). Changes in structure types and metal compositions of the carbides were characterised in detail.
The work was done with the intention to obtain more information about the secondary phase evolution in low alloy steels used
in energy industries. 相似文献
996.
Yvonne Hitchcock Colin Boyd Juan Manuel González Nieto 《Applicable Algebra in Engineering, Communication and Computing》2006,16(6):405-438
Various optimizations in the Canetti–Krawczyk model for secure protocol design are proven to preserve security. In particular
it is shown that multiple authenticators may be safely used together; that certain message components generated by authenticators
may be reordered (to be sent at a different time) or replaced with other values with certain precautions; and that protocols
may be defined in the ideal world with session identifiers constructed during protocol runs. Consequently protocol designers
now have a set of clear rules to optimize and customize their designs without fear of breaking the security proof. In order
to obtain the required proofs, we find it necessary to slightly revise the authenticated links part of the Canetti–Krawczyk
model.
Research funded by Australian Research Council through Discovery Project DP0345775 相似文献
997.
We try to reproduce experimental mobility curves in ultrathin silicon-on-insulator inversion layers using a Monte Carlo simulator
and a bulk model for the electron scattering with acoustic phonons. While it is possible to reproduce the experimental behavior
for the thicker samples, the electron mobility is strongly overestimated when the thinnest samples are considered. The mobility
curves for the thinnest samples can be reproduced using the same model if the deformation potential parameter increases as
the silicon thickness decreases. This fact shows that acoustic phonons are also confined in ultrathin silicon on insulator
layers. We then study confined phonons in single and three layer structures in order to give a physical motivation to the
increase of acoustic phonon scattering rate for in ultrathin silicon layers. 相似文献
998.
Mauricio Areiza-Hurtado Carlos Vega-Posada J. Darío Aristizábal-Ochoa 《Canadian Metallurgical Quarterly》2005,131(7):752-762
The second-order stiffness matrix and corresponding loading vector of a prismatic beam–column subjected to a constant axial load and supported on a uniformly distributed elastic foundation (Winkler type) along its span with its ends connected to elastic supports are derived in a classical manner. The stiffness coefficients are expressed in terms of the ballast coefficient of the elastic foundation, applied axial load, support conditions, bending, and shear deformations. These individual parameters may be dropped when the appropriate effect is not considered; therefore, the proposed model captures all the different models of beams and beam–columns including those based on the theories of Bernoulli–Euler, Timoshenko, Rayleigh, and bending and shear.The expressions developed for the load vector are also general for any type or combinations of transverse loads including concentrated and partially nonuniform distributed loads. In addition, the transfer equations necessary to determine the transverse deflections, rotations, shear, and bending moments along the member are also developed and presented. 相似文献
999.
Miklósi áam; Pongrácz Péter; Lakatos Gabriella; Topál József; Csányi Vilmos 《Canadian Metallurgical Quarterly》2005,119(2):179
Dogs' (Canis familiaris) and cats' (Felis catus) interspecific communicative behavior toward humans was investigated. In Experiment 1, the ability of dogs and cats to use human pointing gestures in an object-choice task was compared using 4 types of pointing cues differing in distance between the signaled object and the end of the fingertip and in visibility duration of the given signal. Using these gestures, both dogs and cats were able to find the hidden food; there was no significant difference in their performance. In Experiment 2, the hidden food was made inaccessible to the subjects to determine whether they could indicate the place of the hidden food to a naive owner. Cats lacked some components of attention-getting behavior compared with dogs. The results suggest that individual familiarization with pointing gestures ensures high-level performance in the presence of such gestures; however, species-specific differences could cause differences in signaling toward the human. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
1000.
Weaver Kathryn E.; Llabre María M.; Durán Ron E.; Antoni Michael H.; Ironson Gail; Penedo Frank J.; Schneiderman Neil 《Canadian Metallurgical Quarterly》2005,24(4):385
The authors tested a structural model that incorporated age, time since diagnosis, social support, coping, and negative mood as predictors of medication adherence and HIV viral load on 188 men and 134 women on highly active antiretroviral therapy (HAART). The authors used psychosocial latent factors formed from baseline measures to predict latent factors of adherence, as assessed by electronic monitoring and self-report, and viral load defined by indicators assessed over a 15-month period. Results from the model indicate that greater negative mood and lower social support are related to greater use of avoidance-oriented coping strategies. Use of these coping strategies by patients on HAART is related to poorer medication adherence and, subsequently, higher viral load. This model advances researchers' understanding of the contribution of psychosocial variables in predicting treatment adherence and disease progression in HIV-positive men and women. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献