全文获取类型
收费全文 | 20708篇 |
免费 | 441篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 226篇 |
综合类 | 14篇 |
化学工业 | 2603篇 |
金属工艺 | 229篇 |
机械仪表 | 335篇 |
建筑科学 | 893篇 |
矿业工程 | 42篇 |
能源动力 | 452篇 |
轻工业 | 1949篇 |
水利工程 | 263篇 |
石油天然气 | 29篇 |
无线电 | 1705篇 |
一般工业技术 | 2375篇 |
冶金工业 | 7285篇 |
原子能技术 | 142篇 |
自动化技术 | 2624篇 |
出版年
2023年 | 68篇 |
2022年 | 152篇 |
2021年 | 265篇 |
2020年 | 136篇 |
2019年 | 199篇 |
2018年 | 266篇 |
2017年 | 246篇 |
2016年 | 271篇 |
2015年 | 253篇 |
2014年 | 387篇 |
2013年 | 660篇 |
2012年 | 676篇 |
2011年 | 917篇 |
2010年 | 634篇 |
2009年 | 663篇 |
2008年 | 697篇 |
2007年 | 674篇 |
2006年 | 566篇 |
2005年 | 552篇 |
2004年 | 507篇 |
2003年 | 469篇 |
2002年 | 428篇 |
2001年 | 343篇 |
2000年 | 319篇 |
1999年 | 514篇 |
1998年 | 2545篇 |
1997年 | 1508篇 |
1996年 | 1009篇 |
1995年 | 612篇 |
1994年 | 572篇 |
1993年 | 557篇 |
1992年 | 215篇 |
1991年 | 216篇 |
1990年 | 205篇 |
1989年 | 213篇 |
1988年 | 215篇 |
1987年 | 152篇 |
1986年 | 146篇 |
1985年 | 199篇 |
1984年 | 139篇 |
1983年 | 102篇 |
1982年 | 113篇 |
1981年 | 125篇 |
1980年 | 97篇 |
1979年 | 93篇 |
1978年 | 83篇 |
1977年 | 193篇 |
1976年 | 237篇 |
1975年 | 79篇 |
1974年 | 71篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
F van Rhee RM Szydlo J Hermans A Devergie F Frassoni W Arcese T de Witte HJ Kolb D Niederwiser N Jacobsen G Gahrton G Bandini E Carreras A Bacigalupo M Michallet T Ruutu J Reiffers JM Goldman J Apperley A Gratwohl 《Canadian Metallurgical Quarterly》1997,20(7):553-560
The purpose of this study was to determine the long-term results of allogeneic bone marrow transplantation for chronic myeloid leukemia. A retrospective analysis was carried out of the outcome of 373 consecutive transplants performed at 38 European institutions between 1980 and 1988 and reported to the registry of the European Group for Blood and Marrow Transplantation. All transplants were carried out for first chronic phase of chronic myelogenous leukemia using unmanipulated marow cells from HLA-identical sibling donors. The probability of survival and leukemia-free survival at 8 years were 54% (95% CI: 49-59) and 47% (95% CI: 41-52) respectively. The probabilities of developing acute GVHD (II-IV) at 100 days and chronic GVHD at 4 years after transplant were 47% (95% CI: 41-53) and 52% (95% CI: 46-58) respectively. The probabilities of transplant-related mortality and leukemic relapse 8 years after BMT were 41% (95% CI: 36-48) and 19% (95% CI: 14-25), respectively. Transplant within 12 months of diagnosis was associated with reduced transplant-related mortality (34 vs 45%, P = 0.013) and resulted in improved leukemia-free survival (52 vs 44%, P = 0.03). The probability of relapse was significantly reduced in patients who developed chronic GVHD (RR = 0.33, P = 0.004). The probability of relapse occurring more than 2 years after transplant was increased more than five-fold in patients transplanted from a male donor (RR = 5.5, P = 0.006). Sixty-seven patients in hematologic remission were studied for residual disease by two-step RT/PCR for BCR-ABL mRNA and 61 (91%) tested negative. We conclude that bone marrow transplantation can induce long-term survival in approximately one-half of CML patients; the majority of survivors have no evidence of residual leukemia cells when studied by molecular techniques. The probability of late relapse is increased with use of a male donor. 相似文献
52.
JF Weel RW van der Hulst Y Gerrits GN Tytgat A van der Ende J Dankert 《Canadian Metallurgical Quarterly》1996,34(9):2158-2162
Combination therapies that include metronidazole (MTZ) are the most successful therapies used in eradicating Helicobacter pylori. In this study, the prevalence and the relevance of heterogeneity in susceptibility to MTZ among H. pylori populations of 156 patients were evaluated. The results of this study show that 37 patients (24%) were infected with MTZ-resistant H. pylori (MIC > or = 8 micrograms/ml). Furthermore, 33% (52 of 156) of the patients were found to be infected with H. pylori populations heterogeneous for their susceptibility to MTZ. The reassessment of the MICs of MTZ for these 52 H. pylori populations revealed MTZ resistance in 28 of them, increasing the number of MTZ-resistant H. pylori populations among the 156 patients to 65 (42%). Out of 20 isolates, 2 (10%) heterogeneous in their susceptibility to MTZ also appeared to be heterogeneous at the genome level as determined by randomly amplified polymorphic DNA fingerprinting. In conclusion, the results show the limitations and risk of possible misinterpretations when only a single colony, picked from the primary H. pylori populations isolated from patients, is analyzed for its susceptibility to MTZ. 相似文献
53.
M Yazdanbakhsh WA Paxton YC Kruize E Sartono A Kurniawan A van het Wout ME Selkirk F Partono RM Maizels 《Canadian Metallurgical Quarterly》1993,167(4):925-931
To establish the relationships among T and B cell responses, active infection, and clinical manifestations in lymphatic filariasis, filarial-specific lymphocyte proliferation, IgG antibody isotypes, and IgE levels were determined in an exposed population: 31 asymptomatic amicrofilaremics, 43 microfilaremics, 12 symptomatic amicrofilaremics, and 52 elephantiasis patients. Lymphocyte proliferation was higher in elephantiasis patients and asymptomatic amicrofilaremics than in microfilaremics (P < .004). A proportion of asymptomatic amicrofilaremics (32%), elephantiasis patients (37%), and symptomatic amicrofilaremics (58%) showed antigen-specific lymphocyte unresponsiveness, and lymphocyte proliferation to filarial antigens correlated negatively with specific IgG4 levels (rho = -0.315, P < .001). As elevated specific IgG4 is an indicator of active infection, it is argued that active infection may result in lymphocyte hyporesponsiveness irrespective of clinical category. Of those with elevated specific IgE levels and high T cell proliferative responses, 70% had elephantiasis, suggesting these factors have a role in pathology. However, the existence of a proportion of elephantiasis patients with low anti-filarial IgE and T cell unresponsiveness to filarial antigens suggests that elephantiasis can be caused by distinct processes. 相似文献
54.
A general numerical model is described for the dissolution kinetics of spherical particles in binary systems for any combination of first order reactions at the particle-matrix interface and long distance diffusion within the matrix. The model is applicable to both finite and infinite media and handles both complete and partial particle dissolution. It is shown that interfacial reactions can have a strong effect on the dissolution kinetics, the solute concentration at the particle-matrix interface and the solute concentration profile in the matrix. 相似文献
55.
56.
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
57.
D.A. van Beek K.L. Man M.A. Reniers J.E. Rooda R.R.H. Schiffelers 《The Journal of Logic and Algebraic Programming》2006,68(1-2):129
The hybrid χ (Chi) formalism integrates concepts from dynamics and control theory with concepts from computer science, in particular from process algebra and hybrid automata. It integrates ease of modeling with a straightforward, structured operational semantics. Its ‘consistent equation semantics’ enforces state changes to be consistent with delay predicates, that combine the invariant and flow clauses of hybrid automata. Ease of modeling is ensured by means of the following concepts: (1) different classes of variables: discrete and continuous, of subclass jumping or non-jumping, and algebraic; (2) strong time determinism of alternative composition in combination with delayable guards; (3) integration of urgent and non-urgent actions; (4) differential algebraic equations as a process term as in mathematics; (5) steady-state initialization; and 6) several user-friendly syntactic extensions. Furthermore, the χ formalism incorporates several concepts for complex system specification: (1) process terms for scoping that integrate abstraction, local variables, local channels and local recursion definitions; (2) process definition and instantiation that enable process re-use, encapsulation, hierarchical and/or modular composition of processes; and (3) different interaction mechanisms: handshake synchronization and synchronous communication that allow interaction between processes without sharing variables, and shared variables that enable modular composition of continuous-time or hybrid processes. The syntax and semantics are illustrated using several examples. 相似文献
58.
The pulp and paper industry has invested heavily over recent years in cleaner processing, to reduce losses and minimise its impact on the environment. Over the past fifteen years, a New Zealand integrated bleached kraft mill has undergone a comprehensive programme of upgrades to increase production, reduce water consumption and streamline its biological treatment process. Whilst the overall discharge of contaminants from the site decreased, the treatment system performance did not show a concurrent improvement as may have been expected. Reduced BOD removal, low dissolved oxygen levels, and poor solids settlability were symptomatic of phosphorus limitation in the aerated lagoon treatment system. The wastewater entering the system was found to be phosphorus limited at a BOD:P ratio of 100:0.2. Mono-ammonium-phosphate was supplemented, at approximately 30 kg P/d, to raise the phosphorus levels to a BOD:P ratio of 100:0.3. Treatment efficiencies improved very quickly after phosphorus dosage, with a 50% reduction in BOD and TSS discharge, a significant increase in dissolved oxygen levels, and improved BOD removal (85% to 93%). This case study demonstrates that whilst more closed operation can result in reduced discharge of organic loads, there may be negative impacts on the availability of nutrients for balanced biological growth. 相似文献
59.
60.