全文获取类型
收费全文 | 23318篇 |
免费 | 337篇 |
国内免费 | 122篇 |
专业分类
电工技术 | 498篇 |
综合类 | 64篇 |
化学工业 | 3187篇 |
金属工艺 | 944篇 |
机械仪表 | 659篇 |
建筑科学 | 547篇 |
矿业工程 | 67篇 |
能源动力 | 604篇 |
轻工业 | 1847篇 |
水利工程 | 212篇 |
石油天然气 | 179篇 |
武器工业 | 1篇 |
无线电 | 2595篇 |
一般工业技术 | 4082篇 |
冶金工业 | 6184篇 |
原子能技术 | 422篇 |
自动化技术 | 1685篇 |
出版年
2021年 | 152篇 |
2020年 | 116篇 |
2019年 | 160篇 |
2018年 | 230篇 |
2017年 | 229篇 |
2016年 | 257篇 |
2015年 | 177篇 |
2014年 | 300篇 |
2013年 | 824篇 |
2012年 | 512篇 |
2011年 | 784篇 |
2010年 | 561篇 |
2009年 | 624篇 |
2008年 | 719篇 |
2007年 | 747篇 |
2006年 | 636篇 |
2005年 | 719篇 |
2004年 | 591篇 |
2003年 | 636篇 |
2002年 | 676篇 |
2001年 | 675篇 |
2000年 | 600篇 |
1999年 | 617篇 |
1998年 | 2171篇 |
1997年 | 1411篇 |
1996年 | 1047篇 |
1995年 | 725篇 |
1994年 | 621篇 |
1993年 | 645篇 |
1992年 | 359篇 |
1991年 | 345篇 |
1990年 | 341篇 |
1989年 | 346篇 |
1988年 | 297篇 |
1987年 | 270篇 |
1986年 | 246篇 |
1985年 | 278篇 |
1984年 | 215篇 |
1983年 | 200篇 |
1982年 | 187篇 |
1981年 | 218篇 |
1980年 | 203篇 |
1979年 | 164篇 |
1978年 | 152篇 |
1977年 | 279篇 |
1976年 | 387篇 |
1975年 | 132篇 |
1974年 | 109篇 |
1973年 | 117篇 |
1972年 | 90篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
U Aguglia A Gambardella RL Oliveri G De Sarro M Zappia A Quattrone 《Canadian Metallurgical Quarterly》1995,10(3):233-238
A 80-year-old man with cobalamin deficiency and no history of epilepsy developed a partial complex epileptic confusional status (ECS) unresponsive to acute i.v. diazepam. Brain CT scan and MRI investigation ruled out a focal cerebral lesion. Therapy with high doses (10,000 micrograms i.m. daily) of cobalamin alone was started, and the patient fully recovered in the following 72-hour. Control EEGs repeatedly performed days and weeks later showed progressive disappearance of the frontal interictal spiking, while the patient was on monotherapy with cobalamin (5,000 micrograms i.m. weekly). A month later the patient unfortunately discontinued replacement therapy and 13 weeks later he developed a fatal convulsive epileptic status. To our knowledge the association of ECS and cobalamin deficiency has not been previously reported. 相似文献
33.
34.
SM Kornblau E Estey T Madden HT Tran S Zhao U Consoli V Snell G Sanchez-Williams H Kantarjian M Keating RA Newman M Andreeff 《Canadian Metallurgical Quarterly》1997,15(5):1796-1802
PURPOSE: Expression of the multidrug resistance gene (MDR1) p170 protein is frequent in leukemic blasts from patients with relapsed acute myelogenous leukemia (AML). A phase I study using the nonimmunosuppressive MDR1 blocker SDZ PSC-833 (PSC) in combination with mitoxantrone (MITO) and etoposide (VP) was performed. PATIENTS AND METHODS: Starting doses (LVL0) of MITO (3.25 mg/m2/d on days 1 and 3 to 6) and VP (210 mg/m2/d on days 1 and 3 to 5) were 40% of the maximal-tolerated dose (MTD) from a prior study. A 1.5-mg/kg loading dose of PSC was followed by a 120-hour continuous infusion of 10 mg/kg/d on days 2 to 6. Blood samples for PSC, MITO, and VP pharmacokinetics (PK) were taken on days 1 and 3, and samples for MDR1 expression were taken on day 0. RESULTS: Severe mucositis developed in all patients at LVL0; therefore, MITO and VP doses were reduced to 2.5 and 170 mg/m2 (LVL-1) for the next seven patients, and this dose proved to be MTD. All LVL0 and three LVL-1 patients had transient elevations in the serum bilirubin level to > or = 4 mg/dL. Serum creatinine level increased to greater than 2 mg/dL in one case. There were no other grade 3 or 4 nonhematologic toxicities observed. The peripheral blood was cleared of leukemia in three LVL0 and four LVL-1 patients. The marrow was cleared of leukemic cells in one LVL0 and five LVL-1 patients, and a significant reduction in marrow leukemic infiltrate was observed in eight of 10. No patient achieved complete remission (CR), and all died of progressive disease (n = 8) or infection (n = 2). MDR1 expression was detected by fluorescent-activated cell sorter (FACS) analysis in five of seven cases. An elevated MDR1 mRNA level was detected by quantitative polymerase chain reaction (Q-PCR) in six of eight cases studied. Clearing of leukemia cells from the marrow occurred in four of six MDR1-positive and one of three MDR1-negative patients. Despite the fact that LVL0 doses had to be reduced due to toxicity, coadministration of PSC did not produce a consistent effect on MITO PK; however, it did repeatedly lead to increased levels of VP in the serum. CONCLUSION: We conclude that PSC-MITO-VP is a tolerable regimen with antileukemic activity. Addition of PSC necessitated a 66% reduction in MITO and VP doses from a prior study without PSC. 相似文献
35.
36.
45 patients with occlusive peripheral vascular disease were examined by MR angiography in a retrospective study. A FISP 3D sequence was used by acquiring a rephased and a dephased data set. The individual slices were post-processed by using a maximum-intensity-projection algorithm. The MRA results of the popliteal and tibioperoneal arteries were compared to conventional or digital angiography. In comparing these techniques MR angiography cannot be accepted for pre- and postoperative staging of patients with occlusive peripheral vascular disease. In future new MRA techniques may be useful in postoperative staging of patients with peripheral vascular stenosis. 相似文献
37.
J Lorenz K Wilhelm M Kessler C Peschel U Schwulera R Lissner WG Struff E Huland C Huber WE Aulitzky 《Canadian Metallurgical Quarterly》1996,2(7):1115-1122
Safety, local and systemic immunomodulation, and tumor response to treatment with aerosolized natural interleukin 2 (nIL-2) applied five times a day were studied in a Phase I trial in 16 patients with pulmonary malignancies refractory to conventional therapy. The toxicity of inhaled nIL-2 was different from that observed after systemic administration. Reversible airway irritation causing a nonproductive cough represented the dose-limiting toxicity. Mild to moderate reduction of the vital capacity and forced expiratory volume (FEV1) with minor effects on relative FEV1, peak expiratory flow, airway resistance, and PaO2 was experienced by individual patients. In 14 patients suffering from pulmonary metastases due to renal cell cancer, one durable complete response, one partial response, and one mixed response were observed. Inhalation of nIL-2 aerosol resulted in a dose-dependent expansion of pulmonary immunocompetent cells in bronchoalveolar lavage fluid. Posttreatment bronchoalveolar lavage showed an activated lymphocyte phenotype with increased HLA-DR expression. The only systemic biological effect detectable in peripheral blood was a marked increase of soluble interleukin 2 receptor serum levels. We conclude that treatment with aerosolized nIL-2 is an effective means for site-specific immunomodulation and deserves further investigation for the treatment of malignant and inflammatory lung disease. 相似文献
38.
Poly(ethylene aspartate) [PEA] was synthesized by the melt condensation of D,L-aspartic acid and ethylene glycol. PEA containing pendent amino and carbonyl groups in its repeating chain was used as the polymeric ligand for complexation with transition metal ions, viz. Co(II), Ni(II), Cu(II), Mn(II), Zn(II), Cd(II), Ca(II), Mg(II), Pb(II) and Hg(II). Complexation was found to be most effective in DMSO. The resulting polyester-metal complexes were solid coloured materials which have been characterized by IR spectroscopy, elemental analysis and magnetic susceptibility measurements. The thermal stability of the polyester-metal complexes was investigated by thermogravimetric analysis (TGA). On the basis of the physico-chemical studies, an oxygen and nitrogen coordinated structure for the polyester-metal complexes is proposed. 相似文献
39.
H.U. Khan K.M. Agrawal M. Anwar S.P. Nautiyal B.S. Rawat 《Petroleum Science and Technology》1998,16(1):145-166
Lubricating oil base stocks differ greatly in their chemical composition and consequently in their physical properties and applications. Influence of waxes and various hydrocarbon type constituents viz saturates and aromatic components on the viscosity and shear stress as a function of temperature in different lube oil base stocks has been studied in the present paper. 相似文献
40.
An "Occam algorithm" learning model maintains a tentative hypothesis consistent with past observations and, when a new observation is inconsistent with the current hypothesis, updates to the next-simplest hypothesis consistent with all observations. In previous work, observations were assumed to be stochastically independent. This paper initiates study of such models under weaker Markovian assumptions on the observations, In the special case where the sequence of hypotheses satisfies a monotonicity condition, it is shown that the number of mistakes in classifying the first t observations is O(√t log 1/πi), where πi is the stationary probability of the initial state, i, of the Markov chain. 相似文献