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991.
992.
993.
ES Sills JD Baum X Ling MM Harper DP Levy CJ Lockwood 《Canadian Metallurgical Quarterly》1997,26(7):704-710
The effect of long-term L-thyroxine (LT4) replacement therapy on bone mineral density and on biochemical markers of bone turnover were studied in children with congenital hypothyroidism (CH). Forty-four children and adolescents (mean age 8.5 +/- 3.5 years) with primary CH who began LT4 replacement therapy within the first month of life were studied. Bone mineral density (BMD) of the lumbar vertebrae and the upper femoral bone was measured by dual energy X-ray absorptiometry. Serum osteocalcin (OC) and bone alkaline phosphatase were measured as markers of bone formation and urinary deoxypyridinoline was taken as a marker of bone resorption. Bone mineral densities of CH children were not different from those in age-matched controls. The biochemical markers of bone turnover were normal except for the serum OC levels which were found to be higher than in controls and positively correlated with the free thyroid hormone levels (for FT4 r = 0.42, p = 0.02). Eight CH children demonstrated low BMD values (below -1 SDS) at -2 +/- 0.7 SDS for the lumbar spine and -1.6 +/- 0.5 SDS for the femoral site. These eight children showed lower mean weight (p < 0.05) and their dietary calcium intake tended to be less (p <0.06) than that seen in the normal BMD group. In conclusion, our results show that LT4 replacement therapy for 8 years is not detrimental to the skeletal mineralization of CH children. As in a healthy population, weight and current intake of calcium seem to be major determinants of bone density. Dietary recommendations, especially when calcium intake is below the recommended dietary allowance, may have to be reconsidered. 相似文献
994.
Vascular MADs: two novel MAD-related genes selectively inducible by flow in human vascular endothelium 总被引:2,自引:0,他引:2
JN Topper J Cai Y Qiu KR Anderson YY Xu JD Deeds R Feeley CJ Gimeno EA Woolf O Tayber GG Mays BA Sampson FJ Schoen MA Gimbrone D Falb 《Canadian Metallurgical Quarterly》1997,94(17):9314-9319
Vascular endothelium is an important transducer and integrator of both humoral and biomechanical stimuli within the cardiovascular system. Utilizing a differential display approach, we have identified two genes, Smad6 and Smad7, encoding members of the MAD-related family of molecules, selectively induced in cultured human vascular endothelial cells by steady laminar shear stress, a physiologic fluid mechanical stimulus. MAD-related proteins are a recently identified family of intracellular proteins that are thought to be essential components in the signaling pathways of the serine/threonine kinase receptors of the transforming growth factor beta superfamily. Smad6 and Smad7 possess unique structural features (compared with previously described MADs), and they can physically interact with each other, and, in the case of Smad6, with other known human MAD species, in endothelial cells. Transient expression of Smad6 or Smad7 in vascular endothelial cells inhibits the activation of a transfected reporter gene in response to both TGF-beta and fluid mechanical stimulation. Both Smad6 and Smad7 exhibit a selective pattern of expression in human vascular endothelium in vivo as detected by immunohistochemistry and in situ hybridization. Thus, Smad6 and Smad7 constitute a novel class of MAD-related proteins, termed vascular MADs, that are induced by fluid mechanical forces and can modulate gene expression in response to both humoral and biomechanical stimulation in vascular endothelium. 相似文献
995.
X Liao JD Gunstream MR Lewin RT Ambron ET Walters 《Canadian Metallurgical Quarterly》1999,19(4):1247-1256
Nociceptive sensory neurons (SNs) in Aplysia provide useful models to study both memory and adaptive responses to nerve injury. Induction of long-term memory in many species, including Aplysia, is thought to depend on activation of cAMP-dependent protein kinase (PKA). Because Aplysia SNs display similar alterations in models of memory and after nerve injury, a plausible hypothesis is that axotomy triggers memory-like modifications by activating PKA in damaged axons. The present study disproves this hypothesis. SN axotomy was produced by (1) dissociation of somata from the ganglion [which is shown to induce long-term hyperexcitability (LTH)], (2) transection of neurites of dissociated SNs growing in vitro, or (3) peripheral nerve crush. Application of the competitive PKA inhibitor Rp-8-CPT-cAMPS at the time of axotomy failed to alter the induction of LTH by each form of axotomy, although the inhibitor antagonized hyperexcitability produced by 5-HT application. Strong activation of PKA in the nerve by coapplication of a membrane-permeant analog of cAMP and a phosphodiesterase inhibitor was not sufficient to induce LTH of either the SN somata or axons. Furthermore, nerve crush failed to activate axonal PKA or stimulate its retrograde transport. Therefore, PKA activation plays little if any role in the induction of LTH by axotomy. However, the expression of LTH was reduced by intracellular injection of the highly specific PKA inhibitor PKI several days after nerve crush. This suggests that long-lasting activation of PKA in or near the soma contributes to the maintenance of long-term modifications produced by nerve injury. 相似文献
996.
JD Adachi WG Bensen J Brown D Hanley A Hodsman R Josse DL Kendler B Lentle W Olszynski LG Ste-Marie A Tenenhouse AA Chines 《Canadian Metallurgical Quarterly》1997,337(6):382-387
BACKGROUND AND METHODS: Osteoporosis is a recognized complication of corticosteroid therapy. Whether it can be prevented is not known. We conducted a 12-month, randomized, placebo-controlled study of intermittent etidronate (400 mg per day for 14 days) followed by calcium (500 mg per day for 76 days), given for four cycles, in 141 men and women (age, 19 to 87 years) who had recently begun high-dose corticosteroid therapy. The primary outcome measure was the difference in the change in the bone density of the lumbar spine between the groups from base line to week 52. Secondary measures included changes in the bone density of the femoral neck, trochanter, and radius and the rate of new vertebral fractures. RESULTS: The mean (+/-SE) bone density of the lumbar spine and trochanter in the etidronate group increased 0.61 +/- 0.54 and 1.46 +/- 0.67 percent, respectively, as compared with decreases of 3.23 +/- 0.60 and 2.74 +/- 0.66 percent, respectively, in the placebo group. The mean differences between the groups after one year were 3.72 +/- 0.88 percentage points for the lumbar spine (P = 0.02) and 4.14 +/- 0.94 percentage points for the trochanter (P = 0.02). The changes in the femoral neck and the radius were not significantly different between the groups. There was an 85 percent reduction in the proportion of postmenopausal woman with new vertebral fractures in the etidronate group as compared with the placebo group (1 of 31 patients vs. 7 of 32 patients, P = 0.05), and the etidronate-treated postmenopausal women also had significantly fewer vertebral fractures per patient (P = 0.04). CONCLUSIONS: Intermittent etidronate therapy prevents the loss of vertebral and trochanteric bone in corticosteroid-treated patients. 相似文献
997.
SE Fong JD Greenwood JC Williamson D Derse LA Pallansch T Copeland L Rasmussen A Mentzer K Nagashima G Tobin MA Gonda 《Canadian Metallurgical Quarterly》1997,233(2):339-357
cDNAs encoding the bovine immunodeficiency virus (BIV) transactivator gene (tat) were cloned from virally infected cells and characterized. BIV expresses two distinct tat mRNAs composed of three exons that are derived by alternative splicing. The BIV tat mRNA splice variants encode Tat proteins of 103 (Tat103) and 108 (Tat108) amino acids. The Tat103 coding region is specified only by exon 2, while that of Tat108 is specified by a truncated exon 2 and the first 30 nt of exon 3. Thus, the first 98 amino acids of each Tat are identical, and have amino terminal, cysteine-rich, conserved core, basic, and carboxyl-terminal domains similar to Tats encoded by primate lentiviruses. BIV-infected bovine cells express a 14-kDa phosphorylated Tat protein identical in size to recombinant Tat expressed in bacteria. BIV Tat was shown to localize exclusively in the nucleoli of virally infected and Tat-expressing cells. Reporter gene assays indicated that Tat103 and Tat108 can strongly transactivate the BIV long terminal repeat (LTR) in virally permissive canine Cf2Th and nonpermissive HeLa and mouse NIH 3T3 cells, but not in permissive lapine EREp cells. However, an intact BIV tat gene is required for viral replication in both Cf2Th and EREp cells. Strong LTR activation by BIV Tat requires a TAR (transactivation responsive) element delimited by viral nt +1 to +31 and the Tat basic domain. BIV Tat strongly cross-transactivates the HIV-1 LTR in a TAR-dependent manner in Cf2Th, but not in EREp, HeLa, or NIH 3T3 cells. In contrast, strong, TAR-dependent cross-transactivation of the BIV LTR by HIV-1 Tat could not be demonstrated in any of these cell types. In Cf2Th cells Tat108 effects a moderately stronger transactivation of the BIV LTR than Tat103, indicative of a functional difference in BIV Tat proteins encoded by the mRNA splice variants. The present studies demonstrate that BIV Tat parallels the primate lentiviral Tats in structure and biochemistry but is not interchangeable with the latter. 相似文献
998.
The objective of the current study was to develop an in vitro testing protocol to evaluate semi-rigid pedicle screw devices. A corpectomy model protocol exists to evaluate rigid spinal implants; however, semi-rigid devices are contraindicated for this condition. This paper describes a technique that simulates more closely the conditions a semi-rigid device would see in vivo. Finally, the new testing protocol is used to evaluate the DDS pedicle screw-cable system. Benefits and shortcomings of the new protocol are discussed. 相似文献
999.
RD Abbott DS Sharp CM Burchfiel JD Curb BL Rodriguez AA Hakim K Yano 《Canadian Metallurgical Quarterly》1997,7(6):417-424
PURPOSE: The purpose of this report is to describe levels of total cholesterol and high-density-lipoprotein cholesterol (HDL-C) in a group of elderly men and to compare these levels to those that were observed 20 years earlier. METHODS: From 1965-1968, the Honolulu Heart Program began following 8006 men of Japanese ancestry living on the island of Oahu, Hawaii, in a prospective study of coronary heart disease and stroke. This report presents data for 971 men who participated in a separate fasting study of lipids and lipoproteins that first occurred from 1970-1972 and in those who received repeat examinations 10 and 20 years later. Men were aged 71-93 years at the last examination. RESULTS: Over the 20-year period, total cholesterol declined by 1.6-1.8 mg/dL per year (P < 0.001), from average baseline values of 219-222 mg/dL. Levels of HDL-C rose 0.2-0.3 mg/dL per year (P < 0.001), from average baseline values of 44-46 mg/dL. After adjustment for baseline cholesterol levels, men with prevalent coronary heart disease at the end of the 20-year follow-up experienced significantly greater reductions in total cholesterol levels than men without disease (P < 0.001). Men who developed coronary heart disease within the first 10 years of follow-up had the greatest yearly decline in total cholesterol (1.9 mg/dL), followed by men who developed heart disease later (1.8 mg/dL) and men who remained disease free (1.5 mg/dL). Differences between men with recent and earlier disease were not statistically significant, although men without coronary disease experienced a significantly smaller decrease in total cholesterol than either of these groups (P < 0.05). CONCLUSIONS: Changes in total cholesterol and HDL-C levels with advancing age may be part of a natural aging process. Some changes, however, such as large reductions in total cholesterol, may signal occult disease or declines in overall health. Selective survival may contribute to these findings since improvements in lipid and lipoprotein levels that are beneficial in younger ages were common in this long-lived cohort of men. 相似文献
1000.