全文获取类型
收费全文 | 33858篇 |
免费 | 1077篇 |
国内免费 | 111篇 |
专业分类
电工技术 | 375篇 |
综合类 | 230篇 |
化学工业 | 5099篇 |
金属工艺 | 625篇 |
机械仪表 | 594篇 |
建筑科学 | 974篇 |
矿业工程 | 94篇 |
能源动力 | 942篇 |
轻工业 | 3886篇 |
水利工程 | 247篇 |
石油天然气 | 151篇 |
武器工业 | 6篇 |
无线电 | 2250篇 |
一般工业技术 | 4122篇 |
冶金工业 | 11462篇 |
原子能技术 | 239篇 |
自动化技术 | 3750篇 |
出版年
2023年 | 150篇 |
2022年 | 499篇 |
2021年 | 787篇 |
2020年 | 533篇 |
2019年 | 599篇 |
2018年 | 689篇 |
2017年 | 776篇 |
2016年 | 724篇 |
2015年 | 556篇 |
2014年 | 853篇 |
2013年 | 1416篇 |
2012年 | 1266篇 |
2011年 | 1597篇 |
2010年 | 1156篇 |
2009年 | 1211篇 |
2008年 | 1101篇 |
2007年 | 968篇 |
2006年 | 788篇 |
2005年 | 843篇 |
2004年 | 907篇 |
2003年 | 816篇 |
2002年 | 786篇 |
2001年 | 689篇 |
2000年 | 543篇 |
1999年 | 690篇 |
1998年 | 3641篇 |
1997年 | 2223篇 |
1996年 | 1479篇 |
1995年 | 927篇 |
1994年 | 755篇 |
1993年 | 833篇 |
1992年 | 254篇 |
1991年 | 340篇 |
1990年 | 293篇 |
1989年 | 248篇 |
1988年 | 270篇 |
1987年 | 223篇 |
1986年 | 216篇 |
1985年 | 238篇 |
1984年 | 130篇 |
1983年 | 100篇 |
1982年 | 143篇 |
1981年 | 147篇 |
1980年 | 168篇 |
1979年 | 94篇 |
1978年 | 88篇 |
1977年 | 293篇 |
1976年 | 562篇 |
1975年 | 85篇 |
1973年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
MC Bueno Jayme Gallani RC Rodrigues Colombo E de Araújo Cintra S Brunelli Rigacci 《Canadian Metallurgical Quarterly》1996,4(2):179-199
The overall purpose of this study was to explore nurses' feelings about the applicability and adequacy of a pilot model of nursing assessment (PMNA) developed for coronary care units (CCU) in order to obtain data that could help in establishing a definitive model. The evaluation, performed by 11 CCU nurses, showed that they considered the development and implementation of PMNA as valuable, and that its design was adequate for interviewing cardiac patients. These results will be employed in the elaboration of a definitive model of nursing assessment. 相似文献
72.
73.
Elevated extracellular potassium concentration ([K+]e) has been shown to induce reversal of glial Na+-dependent glutamate uptake in whole-cell patch clamp preparations. It is uncertain, however, whether elevated [K+]e similarly induces a net glutamate efflux from intact cells with a physiological intracellular milieu. To answer this question, astrocyte cultures prepared from rat and mouse cortices were incubated in medium with elevated [K+]e (by equimolar substitution of K+ for Na+), and glutamate accumulation was measured by HPLC. With [K+]e elevations to 60 mM, medium glutamate concentrations did not increase during incubation periods of 5-120 min. By contrast, 45 min of combined inhibition of glycolytic and oxidative ATP production increased medium glutamate concentrations 50-100-fold. Similar results were obtained in both rat and mouse cultures. Studies were also performed using astrocytes loaded with the nonmetabolized glutamate tracer D-aspartate, and parallel results were obtained; no increase in medium D-aspartate content resulted from [K+]e elevation up to 90 mM, whereas a large increase occurred during inhibition of energy metabolism. These results suggest that a net efflux of glutamate from intact astrocytes is not induced by any [K+]e attainable in brain. 相似文献
74.
75.
RA Newman JC Vidal LJ Viskatis J Johnson MA Etcheverry 《Canadian Metallurgical Quarterly》1993,11(2-3):151-159
Two purified animal venom toxins, crotoxin and cardiotoxin, have been combined to produce a unique natural product (VRCTC-310) currently under investigation as an antitumor agent by the National Cancer Institute. In vitro, it has demonstrated cytotoxic disease specificity and a unique mechanism of action when submitted to COMPARE analysis. In vivo, tolerance was developed to the neurotoxic properties of crotoxin which allowed comparison of several schedules of fixed and escalating daily i.m. doses to mice bearing s.c. Lewis Lung carcinoma. An 83% inhibition of tumor growth was achieved using an escalating dose schedule starting at 1.8 mg/kg and reaching 6.3 mg/kg/day on day 20. Although some irritation around the sites of i.m. injection was noted, animal weight loss was negligible and there were no other signs of adverse toxicity. This natural product represents a new, membrane interactive anticancer agent which produces a unique spectrum of cytotoxicity in vitro and which has demonstrated interesting in vivo antitumor efficacy. 相似文献
76.
EJ Velthuis-te Wierik H van den Berg JA Weststrate KH van het Hof C de Graaf 《Canadian Metallurgical Quarterly》1996,50(4):214-219
Plasma levels of fibrinogen, factor VIIc and prothrombin fragment F1 + 2, a marker of thrombin generation in vivo, were studied in 68 subjects with serum total cholesterol (TC) levels between 135 and 349 mg/dl but without clinical evidence of cardiovascular disease and other atherosclerotic risk factors. F1 + 2 plasma levels were directly correlated with TC (p < 0.0004), low-density lipoprotein cholesterol (LDL-C; p < 0.0018) and factor VIIc (p < 0.024). Thirty-five subjects with TC greater than 249 mg/dl (median value of the whole group) showed higher levels of F1 + 2 (p < 0.0001) and fibrinogen (p < 0.0015) than those with TC lower than 249 mg/dl. In subjects with TC > 249 mg/dl and F1 + 2 > 1.2 nM (median value of the whole group), a cholesterol-lowering drug (simvastatin) was able to reduce F1 + 2 (p < 0.009) as well as TC and LDL-C. This study shows a relationship between serum cholesterol and the rate of thrombin generation supporting the hypothesis that a hypercoagulable state may occur in hypercholesterolemic subjects before the onset of clinical evidence of atherosclerotic cardiovascular disease. 相似文献
77.
Bone marrow transplantation (BMT) using HLA-partially matched family donors has produced disappointing results (25-30% of long-term survivors) in patients with severe aplastic anemia. We describe two children affected by severe aplastic anemia, not responsive to immunosuppressive therapy, who underwent allogeneic bone marrow transplantation using a HLA-partially matched family donor. Both cases presented 2 first class HLA-antigens (A and B) disparity between donor and recipient. The pretransplant conditioning regimen consisted of cyclophosphamide, thoracoabdominal irradiation, cytosine-arabinoside, and antilymphocyte globulin. As graft versus host disease (GVHD) prophylaxis, Cyclosporine-A was administered at usual dosages for 6 months. A full marrow engraftment was observed in both cases. Only grade I acute GVHD, promptly responsive to corticosteroid therapy, developed with no chronic GVHD. Five months after transplant, both children progressively developed hypertension, renal function impairment, thrombocytopenia, and severe normochromic anemia, with erythropoietin serum levels lower than expected for the haematocrit. After antihypertension treatment and supportive therapy, the clinical picture progressively improved, while treatment with recombinant human erythropoietin completely corrected the long-lasting anemia. The two children are alive and well 28 months after the transplant, with a Karnofsky score of 100% and a normal peripheral blood count. The authors suggest that, once immunosuppressive therapy has failed, BMT from donors other than HLA-identical sibling is a feasible approach in children affected by severe aplastic anemia, not having an HLA-identical donor. 相似文献
78.
Cristiane Vieira Helm Alicia de Francisco Salete Aparecida Gaziola Ricardo Francisco Fornazier Georgia Bertoni Pompeu Ricardo Antunes Azevedo 《Food Biotechnology》2005,18(3):327-341
Barley (Hordeum vulgare L.) has had an important impact on human nutrition. Hull-less barley is a genetically improved type that has been widely used in recent years. Six Brazilian hull-less barley varieties (IAC-IBON 214-82; IAC 8612-421; IAC 8501-31; IAC 8501-12; IAPAR 39-ACUMAI; IAC 8501-22) were analyzed for storage protein constituents, amino acid contents, and similarity among the hull-less barley varieties. Albumins, globulins, prolamins I and II, and glutelins were extracted and separated by SDS-PAGE. The total protein amino acid contents of the flour were also determined for each variety by TLC and HPLC. Variations in intensity and appearance and disappearance of protein bands were observed among the varieties suggesting genetic variability. However, the amino acid profile did not indicate any major variations in the amino acid concentrations. The high lysine and threonine total concentrations detected in the seeds of the hull-less barley varieties encouraged an investigation into the regulation of amino acid metabolism and storage protein synthesis. 相似文献
79.
We describe a method for computing solutions of multi-point boundary value problems, where the polychotomic structure of the underlying solution space is specifically exploited. After the system is integrated in a multiple shooting way, the resulting linear system is solved by a special decoupling algorithm that takes into account the fact that the dichotomy on each interval is potentially different (in contrast to the two point case). A number of examples sustains the theory. 相似文献
80.
Jing Wang Walker D.M. Xiang Lu Majhi A. Kruseman B. Gronthoud G. Villagra L.E. van de Wiel P.J.A. Eichenberger S. 《Design & Test of Computers, IEEE》2007,24(3):226-234
Excessive power supply noise during test can cause overkill. This article discusses two models for supply noise in delay testing and their application to test compaction. The proposed noise models avoid complicated power network analysis, making them much faster than existing power noise analysis tools. can cause performance degradation and 相似文献