全文获取类型
收费全文 | 7614篇 |
免费 | 414篇 |
国内免费 | 249篇 |
专业分类
电工技术 | 326篇 |
综合类 | 351篇 |
化学工业 | 1094篇 |
金属工艺 | 377篇 |
机械仪表 | 299篇 |
建筑科学 | 468篇 |
矿业工程 | 125篇 |
能源动力 | 221篇 |
轻工业 | 391篇 |
水利工程 | 84篇 |
石油天然气 | 255篇 |
武器工业 | 37篇 |
无线电 | 668篇 |
一般工业技术 | 912篇 |
冶金工业 | 1841篇 |
原子能技术 | 76篇 |
自动化技术 | 752篇 |
出版年
2024年 | 21篇 |
2023年 | 88篇 |
2022年 | 140篇 |
2021年 | 223篇 |
2020年 | 183篇 |
2019年 | 170篇 |
2018年 | 144篇 |
2017年 | 171篇 |
2016年 | 168篇 |
2015年 | 169篇 |
2014年 | 252篇 |
2013年 | 350篇 |
2012年 | 314篇 |
2011年 | 396篇 |
2010年 | 320篇 |
2009年 | 306篇 |
2008年 | 338篇 |
2007年 | 313篇 |
2006年 | 343篇 |
2005年 | 311篇 |
2004年 | 209篇 |
2003年 | 214篇 |
2002年 | 169篇 |
2001年 | 167篇 |
2000年 | 138篇 |
1999年 | 220篇 |
1998年 | 555篇 |
1997年 | 379篇 |
1996年 | 290篇 |
1995年 | 197篇 |
1994年 | 171篇 |
1993年 | 157篇 |
1992年 | 62篇 |
1991年 | 86篇 |
1990年 | 63篇 |
1989年 | 61篇 |
1988年 | 62篇 |
1987年 | 54篇 |
1986年 | 37篇 |
1985年 | 25篇 |
1984年 | 6篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 42篇 |
1976年 | 97篇 |
1975年 | 11篇 |
排序方式: 共有8277条查询结果,搜索用时 15 毫秒
991.
S Baldus CW Hamm J Reimers W Terres T Münzel C Brockhoff T Meinertz 《Canadian Metallurgical Quarterly》1998,45(4):456-459
Although the association between transverse myelitis (TM) and systemic lupus erythematosus (SLE) has been reported previously, it remains a rare clinical condition. Our experience treating three women with lupus TM within a few months is presented. In each patient, spinal cord dysfunction was accompanied by laboratory or clinical evidence of SLE. Further neurologic manifestations, such as optic neuritis, developed in all patients, suggesting other diagnoses, including multiple sclerosis (MS), Devic's syndrome, and lupoid sclerosis. The outcomes for these three women were severe disability, death, and moderate disability, respectively. The severity of outcome did not seem to correlate with the timing or intensity of treatment. Physiatrists should be aware of the potential for neurologic progression in lupus TM, because patients with this condition invariably require rehabilitation. 相似文献
992.
BACKGROUND: Immediate skin reactions to allergens are influenced by several factors, such as the amount of administered allergen, the level of specific IgE, releasability of mast cells and hyperresponsiveness of the target organ. METHODS: For the evaluation of factors influencing immediate skin response to intradermal allergen administration, we measured the wheal size 15 min after intradermal injection of 0.01-0.02 ml of the following agents: whole-body extract of Dermatophagoides farinae, 1,000 allergy units/ml; histamine, 0.1 mg/ml, and codeine sulfate, 0.09% in saline, and determined total IgE level, specific IgE and IgG subclass antibodies to D. farinae in 53 patients with respiratory allergy. RESULTS: Multiple regression analysis for factors influencing wheal size after intradermal injection of D. farinae, specific IgE antibody level to D. farinae and wheal size after intradermal administration of histamine showed statistically significant results (R2 = 0.42739, p = 0.0000; R2 = 0.50243, p = 0.0185, respectively). Multiple regression analysis for factors influencing wheal size after intradermal administration in the group with high levels of specific IgE to D. farinae (RAST class 3 or more) showed that wheal size after intradermal administration of codeine was the only factor exerting a statistically significant influence (p = 0.0119). CONCLUSION: Based on the above results, we can state that immediate responses to intradermal allergen administration were influenced by the level of specific IgE and hyperresponsiveness of the target organ to histamine, but that the immediate skin allergic responses in the presence of high levels of specific IgE were partially but significantly influenced by the releasability of skin mast cells. 相似文献
993.
ML Wang WB Liao MJ Bullard FC Lin PJ Lin CW Chiang SJ Liaw CH Chiang 《Canadian Metallurgical Quarterly》1997,61(9):767-771
We describe two sibs with chorioretinal dystrophy, hypogonadotrophic hypogonadism, and cerebellar ataxia, Boucher-Neuh?user syndrome, a rare but distinct pleiotropic single gene disorder with an autosomal recessive pattern of inheritance. The cases presented illustrate that this syndrome is still poorly recognised. We provide a review and analysis of previously reported cases and the differential diagnosis, which might aid in the identification of additional cases. 相似文献
994.
995.
STUDY DESIGN: A technique is described for analyzing electromyogram data from lumbar spinal muscles, with special reference to discrimination of people with back pain. The ability to discriminate was evaluated in 99 people (61 healthy and 38 with chronic or acute back pain), and the influence of load was assessed. OBJECTIVES: To evaluate methods of analysis of complex electromyogram data and to assess correlation of electromyogram information with clinical condition in people with and without back pain. SUMMARY OF BACKGROUND INFORMATION: In previous analyses of electromyogram data, only a small part of the data have been used. Spinal muscular decompensation has been postulated in chronic low back pain, but there has been no direct demonstration of this phenomenon. Objective measures are still elusive. METHODS: Lumbar spinal surface electromyograms were recorded during an isometric lifting task. The data were represented graphically as color-coded plots of electromyogram frequency, time, and electromyogram amplitude. Spectral width at half-peak amplitude (spectral half width) was calculated from the digitized, summed data. Ninety-nine people were tested: 48 men (29 with no recent [in the past 2 years] history of back pain, 16 with chronic back pain, 3 with acute back pain) and 51 women (32 with no recent back pain and 19 with chronic back pain). RESULTS: Spectral color maps in people with chronic back pain were markedly different from those in healthy people. Spectral half width was greater in people with chronic back pain than in healthy people (P < 0.01). Blinded analysis of spectral color maps allowed discrimination of people with back pain from healthy people with a sensitivity of 76% and a specificity of 81%. People with a history of back pain had markedly variable half widths. CONCLUSIONS: A new method of analysis of electromyogram data from lumbar spinal muscles has allowed discrimination between people with back pain and healthy people. This provides direct evidence of a correlation between muscular electrical function, measured by electromyogram, and low back pain. This technique may have potential as an objective measurement tool. 相似文献
996.
S K?ster B Th?ny P Macheroux HC Curtius CW Heizmann W Pfleiderer S Ghisla 《Canadian Metallurgical Quarterly》1995,231(2):414-423
Pterin-4a-carbinolamine dehydratase/dimerization cofactor for hepatocyte nuclear factor-1 alpha is a protein with two different functions. We have overexpressed and purified the human wild-type protein, and its Cys81Ser and Cys81Arg mutants. The Cys81Arg mutant has been proposed to be causative in a hyperphenylalaninaemic patient [Citron, B. A., Kaufman, S., Milstien, S., Naylor, E. W., Greene, C. L. & Davis, M. D. (1993) Am. J. Hum. Genet. 53, 768-774]. The dehydratase behaves as a tetramer on gel filtration, while cross-linking experiments showed mono-, di-, tri-, and tetrameric forms, irrespective of the presence of the single Cys81. Sulfhydryl-modifying reagents did not affect the activity, but rather showed that Cys81 is exposed. Various pterins bind and quench the tryptophan fluorescence suggesting the presence of a specific binding site. The fluorescence is destroyed upon light irradiation. Wild-type and the Cys81Ser protein enhance the rate of the phenylalanine hydroxylase assay approximately 10-fold, a value similar to that of native dehydratase from rat liver; the Cys81Arg mutant, in contrast, has significantly lower activity. This is compatible with the hypothesis that the dehydratase is a rate-limiting factor for the in vivo phenylalanine hydroxylase reaction. The three proteins enhance the spontaneous dehydration of the synthetic substrate 6,6-dimethyl-7,8-dihydropterin-4a-carbinolamine approximately 50-70-fold at 4 degrees C and pH 8.5. The results are discussed in view of the recently solved three-dimensional structure of the enzyme [Ficner, R., Sauer, U. W., Stier, G. & Suck, D. (1995) EMBO J. 14, 2032-2042]. 相似文献
997.
J.P. Zhang D.Y. Chu S.L. Wu W.G. Bi R.C. Tiberio R.M. Joseph A. Taflove C.W. Tu S.T. Ho 《Photonics Technology Letters, IEEE》1996,8(4):491-493
A strongly-guided one-dimensional (1-D) waveguide called a photonic wire has high spontaneous emission coupling efficiency, enabling one to realize low-threshold lasers. Combined with the use of 1-D photonic bandgap structures consisting of arrays of holes etched within the photonic wire, novel microcavity lasers can be realized. We report the nanofabrication of a photonic bandgap structure for 1.5 /spl mu/m wavelength along a InGaAsP photonic wire, and discuss numerical simulations for its electrodynamics. 相似文献
998.
In utero varicella-zoster infections, though infrequent, may have significant consequences for the affected infant depending on the gestational timing of the infection. We present a case of infantile zoster in a 5-month-old boy after maternal varicella infection. Also, we review the three major disorders resulting from in utero infection with respect to severity and management. 相似文献
999.
CS Nicoll F Mena CW Nichols SH Green M Tai SM Russel 《Canadian Metallurgical Quarterly》1976,83(3):512-521
Suckling-induced changes in adenohypophyseal prolactin (PRL) concentrations in lactating rats were measured in two experiments by three assays: a disc electrophoretic assay (DEA), a bioassay (BA) and a radioimmunoassay (RIA). Substantial discrepancies among the three assays were found in the absolute amounts of pituitary PRL measured and in the changes in adenohypophyseal PRL concentration that were recorded between suckling intervals. The results indicate that in dynamic states of secretory activity the correspondence among BA, RIA and DEA estimates of pituitary PRL concentration is poor. 相似文献
1000.