全文获取类型
收费全文 | 302328篇 |
免费 | 2288篇 |
国内免费 | 919篇 |
专业分类
电工技术 | 5109篇 |
综合类 | 136篇 |
化学工业 | 48053篇 |
金属工艺 | 17124篇 |
机械仪表 | 11587篇 |
建筑科学 | 5524篇 |
矿业工程 | 4044篇 |
能源动力 | 5540篇 |
轻工业 | 15354篇 |
水利工程 | 4719篇 |
石油天然气 | 14062篇 |
武器工业 | 67篇 |
无线电 | 25666篇 |
一般工业技术 | 73312篇 |
冶金工业 | 41836篇 |
原子能技术 | 12662篇 |
自动化技术 | 20740篇 |
出版年
2021年 | 3277篇 |
2019年 | 3167篇 |
2018年 | 6191篇 |
2017年 | 6503篇 |
2016年 | 6896篇 |
2015年 | 3601篇 |
2014年 | 6198篇 |
2013年 | 12617篇 |
2012年 | 8824篇 |
2011年 | 10790篇 |
2010年 | 8868篇 |
2009年 | 9889篇 |
2008年 | 9963篇 |
2007年 | 9649篇 |
2006年 | 7915篇 |
2005年 | 6925篇 |
2004年 | 6797篇 |
2003年 | 6644篇 |
2002年 | 6395篇 |
2001年 | 6224篇 |
2000年 | 6136篇 |
1999年 | 5510篇 |
1998年 | 10460篇 |
1997年 | 8094篇 |
1996年 | 6081篇 |
1995年 | 4968篇 |
1994年 | 4551篇 |
1993年 | 4727篇 |
1992年 | 3957篇 |
1991年 | 4150篇 |
1990年 | 4281篇 |
1989年 | 4138篇 |
1988年 | 3963篇 |
1987年 | 3869篇 |
1986年 | 3785篇 |
1985年 | 3992篇 |
1984年 | 3814篇 |
1983年 | 3699篇 |
1982年 | 3487篇 |
1981年 | 3555篇 |
1980年 | 3547篇 |
1979年 | 3736篇 |
1978年 | 3915篇 |
1977年 | 4033篇 |
1976年 | 4629篇 |
1975年 | 3607篇 |
1974年 | 3664篇 |
1973年 | 3728篇 |
1972年 | 3319篇 |
1971年 | 3064篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
This paper proposes a system based on a parallel genetic algorithm with enhanced encoding and operational abilities. The system, used to evolve feedforward artificial neural networks, has been applied to two widely different problem areas: Boolean function learning and robot control. It is shown that the good results obtained in both cases are due to two factors: first, the enhanced exploration abilities provided by the search-space reducing evolution of both coding granularity and network topology, and, second, the enhanced exploitational abilities due to a recently proposed cooperative local optimizing genetic operator. 相似文献
42.
Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 95–112, March–April, 1994. 相似文献
43.
44.
The electrochemical and corrosion behaviour of a nickel base super alloy (C-263) has been investigated in the deaerated binary and ternary solution mixture of concentrated phosphoric acid, acetic acid, sulphuric acid, nitric acid or water using potentiostatic technique at 35°C. The possibilities of electropolishing of this alloy in these solution mixtures have been also explored. The alloy showed distinct active, passive and transpassive behaviour in the experimental solutions. The alloy remained active and turned passive in the negative potential region. Transpassive dissolution of the alloy is observed and electropolishing is achieved in this region. The best electropolishing is obtained in 50% H3PO4 + 40% CH3COOH + 10% H2SO4. Higher content of water in the electrolytic solution is not useful for electropolishing of the alloy The experimental results also suggest that a current plateau in the transpassive potential region is not a sufficient condition to achieve electropolishing. 相似文献
45.
Several in vivo and in vitro methods for monitoring immunological properties of two allergoids obtained by formaldehyde treatment of ovalbumin (OA) were developed. The calculated molecular weight of allergoids was 80 kD (OA-F1) and 165 kD (OA-F2), respectively. The allergenic activity in vitro of allergoids in mast-cell histamine release assay was 1000 times lower than of OA. Both allergoids showed reduced ability to induce passive cutaneous anaphylaxis in the Sprague-Dawley rats or systemic anaphylaxis in Dunkin-Harley guinea-pigs. The ability of OA and allergoids to bind to the OA-specific IgE antibodies was measured in vivo by the inhibition of passive cutaneous anaphylaxis (PCA-inhibition). Allergoid binding to IgE was 51-66% lower than the native allergen. Moreover, the avidity of OA-specific IgG antibodies, measured by ELISA-inhibition, for allergoids and allergen was of the same order. Allergoids induced a different pattern of humoral immune response from that, induced by the native allergen. Thus, after immunization of BALB/c mouse, both allergoids induced a higher production of IgG and a lower production of IgE than OA, only OA-F2 induced a lower production of IgG1. The differences in the IgA response to the immunogens was not significant. Delayed hypersensitivity studies in the BALB/c mouse showed that allergoids were 5- to 12-times less effective in inducing a cell-mediated immune response than OA. The present study provides a battery of immunological methods for preclinical testing of modified allergens. 相似文献
46.
This paper presents a model of heterogenous diffusion in capillary porous materials during the process of drying. The governing heat and mass transfer equations have been established using the liquid as well as vapor flow. Two models have been presented. Model 1 does not consider the heat conduction while the model 2 has been established by considering the conduction. The developed models and the numerical solutions of the resulting differential equations can take into account the moisture and temperature dependent thermophysical properties of the product. All equations have been established in spherical coordinates but the programme written for the purpose of calculations can be used for other geometries also. Numerical calculations have been performed for gas concrete and tiles using model 1, while model 2 has been used for gas concrete only because of the lack of data for thermophysical properties of the tile. For gas concrete it was seen that conduction has only marginal effect on the drying process and the numerical predictions of the drying process were reasonably accurate. 相似文献
47.
Muralidhar N. Ingale Vijaykumar V. Mahajani 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,64(1):80-86
The effectiveness of the hybrid system sonication followed by wet oxidation (SONIWO) to treat otherwise refractory waste has been demonstrated. In such a hybrid system homogeneous CuSO4 catalyst was found to be very efficient. 相似文献
48.
V. A. Arzamastsev N. L. Sardaev A. S. Kochergin 《Metal Science and Heat Treatment》1996,38(11):477-479
The technological process of cold forging applied for the first time in the production of the casing of the internal joint with races is described. The process operations of cold forging and the annealing and carburizing regimes for this part me described. 相似文献
49.
It is not known whether impaired hematopoiesis noted during human immunodeficiency virus (HIV) infection results from infection of stem/progenitor cells or of cells of the bone marrow microenvironment. Normal adherent primary stromal layers were exposed to HIV to determine which of this mixture of endothelial cells, fibroblasts, and macrophages are susceptible to the virus. Viral p24 in supernatants was noted with monocytotropic HIV-1Ada, HIV-1Ba-L, and HIV-1JR-FL but not with lymphotropic HIV-1LAI nor HIV-1MN strain, and only stromal macrophages expressed the viral antigens. Coculture of the layers with PHA-activated normal lymphocytes failed to rescue lymphotropic virus. No p24 was produced when macrophage-depleted stromal cells were exposed to either HIV-1Ba-L or HIV-1LAI; proviral DNA was then amplified by PCR in cells exposed to either virus, though coculture with lymphocytes rescued only HIV-1Ba-L. Altogether, these data indicate that macrophages are the major targets of HIV in cultured stromal layers. As virus replication in macrophages did not affect the profile of major cytokines involved in regulating hematopoiesis, HIV infection could alter hematopoiesis by other as yet unspecified mechanisms. 相似文献
50.
O. V. Denisenko 《Measurement Techniques》1996,39(11):1092-1094
A method is considered for increasing the immunity from interference of broadband systems for measuring and transmitting information.
It is based on utilizing nonlinear methods to process spread-spectrum signals. The possibility is investigated of using a
quasioptimal receiving device which can be implemented in practice. It is shown that the proposed method makes it possible
to solve the rejection problem at the physical level.
Translated from Izmeritel'naya Tekhnika, No. 11, pp. 13–15, November, 1996. 相似文献