全文获取类型
收费全文 | 6472篇 |
免费 | 36篇 |
专业分类
电工技术 | 7篇 |
综合类 | 1篇 |
化学工业 | 404篇 |
金属工艺 | 13篇 |
机械仪表 | 29篇 |
建筑科学 | 18篇 |
矿业工程 | 2篇 |
能源动力 | 17篇 |
轻工业 | 554篇 |
水利工程 | 1篇 |
石油天然气 | 4篇 |
无线电 | 45篇 |
一般工业技术 | 134篇 |
冶金工业 | 5205篇 |
原子能技术 | 6篇 |
自动化技术 | 68篇 |
出版年
2022年 | 15篇 |
2021年 | 24篇 |
2018年 | 12篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 15篇 |
2014年 | 25篇 |
2013年 | 103篇 |
2012年 | 29篇 |
2011年 | 26篇 |
2010年 | 23篇 |
2009年 | 20篇 |
2008年 | 20篇 |
2007年 | 19篇 |
2006年 | 16篇 |
2005年 | 18篇 |
2004年 | 19篇 |
2003年 | 17篇 |
2000年 | 15篇 |
1999年 | 144篇 |
1998年 | 1537篇 |
1997年 | 877篇 |
1996年 | 595篇 |
1995年 | 351篇 |
1994年 | 320篇 |
1993年 | 341篇 |
1992年 | 65篇 |
1991年 | 102篇 |
1990年 | 76篇 |
1989年 | 103篇 |
1988年 | 113篇 |
1987年 | 101篇 |
1986年 | 92篇 |
1985年 | 58篇 |
1984年 | 26篇 |
1983年 | 34篇 |
1982年 | 47篇 |
1981年 | 53篇 |
1980年 | 69篇 |
1979年 | 25篇 |
1978年 | 51篇 |
1977年 | 164篇 |
1976年 | 365篇 |
1975年 | 42篇 |
1974年 | 25篇 |
1973年 | 24篇 |
1972年 | 29篇 |
1971年 | 28篇 |
1970年 | 22篇 |
1965年 | 14篇 |
排序方式: 共有6508条查询结果,搜索用时 15 毫秒
1.
Maria A. Ospina Monica Pizarro Thierry Tran Julien Ricci John Belalcazar Jorge L. Luna Luis F. Londoño Sandra Salazar Hernan Ceballos Dominique Dufour Luis A. Becerra Lopez-Lavalle 《International Journal of Food Science & Technology》2021,56(3):1343-1353
The objective of this study was to characterise the nutritional potential of leaves and identify a diversity centre with low cyanide and high nutrient content among 178 Latin American cassava genotypes. This field-based collection represents the seven diversity centres, held at The International Center for Tropical Agriculture (CIAT Palmira, Colombia) by the Cassava Program. The cyanide, all-trans-β-carotene and lutein concentrations in cassava leaves ranged from 346 to 7484 ppm dry basis (db), from 174–547 μg g−1 db and 15–181 μg g−1 db, respectively. Cassava leaves also showed significant levels of essential amino acids leucine, lysine, phenylalanine, valine and threonine, and average total protein content of 26.24 g 100 g−1 db. Among seven diversity centres, South American rainforest group showed low cyanide and high carotene content in leaves. In addition, VEN77 and PAN51 genotypes stood out for having low cyanide in leaves and roots and high carotene in leaves. This genetic diversity can be used to select high potential progenitors for breeding purposes. 相似文献
2.
IR与RS-232的匹配技术 总被引:2,自引:0,他引:2
TedSalazar 《电子设计应用》2004,(3):86-87
现代电子设备通常包含最新的数据通信接口,以实现更高的数据率或增进用户的便利性。红外技术(IR)是数据通信接口的一个很好例子,但有时单独使用这种最新接口还是不够的,设备还需要与采用传统接口如RS-232的老设备兼容才会被用户所接受。因此,常见的红外技术和RS-232共存于同一设备中。 相似文献
3.
A fundamental problem for regulatory networks is to understand the relation between form and function: to uncover the underlying design principles of the network. Circadian clocks present a particularly interesting instance, as recent work has shown that they have complex structures involving multiple interconnected feedback loops with both positive and negative feedback. While several authors have speculated on the reasons for this, a convincing explanation is still lacking.We analyse both the flexibility of clock networks and the relationships between various desirable properties such as robust entrainment, temperature compensation, and stability to environmental variations and parameter fluctuations. We use this to argue that the complexity provides the flexibility necessary to simultaneously attain multiple key properties of circadian clocks. As part of our analysis we show how to quantify the key evolutionary aims using infinitesimal response curves, a tool that we believe will be of general utility in the analysis of regulatory networks. Our results suggest that regulatory and signalling networks might be much less flexible and of lower dimension than their apparent complexity would suggest. 相似文献
4.
5.
6.
FJ Overdyk PM Gramling-Babb JR Handy NI Faller MJ Miller 《Canadian Metallurgical Quarterly》1997,84(1):213-215
Robertsonian translocations, although relatively common as a constitutional genetic aberration, are rarely encountered in leukaemia. We report a case of acute myeloid leukaemia which showed an acquired Robertsonian translocation in the form of der(14;21) by cytogenetic analysis of leukaemic cells. This was confirmed by the PHA-stimulated culture of peripheral blood lymphocytes. A review of the literature identifies only eight reported cases of acquired Robertsonian translocations in leukaemia. In the majority of cases the Robertsonian translocation occurs as a secondary change in a complex abnormal clone, whereas in two out of nine patients reported, including ours, it is found as a sole karyotypic abnormality. 相似文献
7.
JB Kamien WK Bickel BJ Smith GJ Badger JR Hughes 《Canadian Metallurgical Quarterly》1997,58(4):983-991
The percentage of long-term survivors after intensive chemotherapy and the outcome of MDS patients who achieve partial remission (PR) with intensive chemotherapy (IC) are not known. Between 1981 and 1996 we treated 99 patients with de novo MDS who had high-risk MDS or progression to AML, with IC. 41 (41%) achieved CR, 16 (16%) achieved partial remission (PR), 26 (26%) had failure, and 16 (16%) died in aplasia. Eight of the patients who achieved CR were autografted, three were allografted and the remaining cases received moderate consolidation chemotherapy. After IC, the 16 PR patients fulfilled the criteria for RA in 15 cases and CMML in one case. Median PR duration was 17 months, and three PR were > 3 years (39, 50+, 82+ months). Median actuarial survival of patients who achieved PR and CR was 18 months and 20 months from the onset of IC, respectively (difference not significant). Of the 71 patients treated before 1993, with sufficient follow-up, 10 (14%) had survived > 4 years (long-term survivors). Four of them were alive in first CR after 49+ to 110+ months and probably cured, two were alive in PR after 50+ and 82+ months and four had died after 49-78 months. Long-term survivors were characterized by a significantly higher incidence of RAEB-T at diagnosis, and with normal or favourable cytogenetic findings. In patients with RAEB-T at diagnosis included before 1993, 8/23 (35%) cases who had no unfavourable karyotype had survived > 4 years. Our findings suggest that MDS patients who achieve PR with IC, and not only those who achieve CR, can benefit from this type of treatment. The percentage of long-term survivors remains low, however, and is almost restricted to patients with RAEB-T at diagnosis and no unfavourable karyotype. 相似文献
8.
Carcinoma of the prostate, that is adenocarcinoma, is one of the most common malignancies in the male with an estimated incidence for 1991 of 122,000 new cases. On the other hand, squamous cell carcinoma of the prostate, with a median incidence of .5%-1% of all prostatic malignancies, has a similar clinical presentation but differs in treatment response and prognosis. We herein present one case of this histological pattern and review the literature pertaining to it. 相似文献
9.
JR Hamilton 《Canadian Metallurgical Quarterly》1997,11(1):94-98
OBJECTIVES: To identify knowledge levels of academic surgeons about Food and Drug Administration (FDA) and Institutional Review Board (IRB) regulations for clinical research and to determine whether being a member in an IRB, conducting or participating in clinical trials, or being a member in surgical societies affected knowledge levels. DESIGN: Survey of surgical department faculty members in 20 universities. RESULTS: Sixty-five responses were received from 14 sites. Overall mean (+/- SEM) correct score was 6.7 +/- 0.2 of a possible 20 points. The best predictor of overall score was being a primary investigator of a clinical trial (P < .001), followed by being or having been a member of an IRB (P < or = .02). The total mean score of members of the Surgical Infection Society (8.2 +/- 0.5) was significantly higher (P < .001) than that of nonmembers (6.1 +/- 0.2), a phenomenon not observed with other surgical societies. In certain hypothetical clinical scenarios, all respondents were mistakenly willing to conduct clinical trials without obtaining appropriate approval from the FDA. Four (22%) of 18 IRB member respondents and 16 (25%) of the 65 respondents were willing to conduct human research without appropriate approval from patients, the IRB, or both. CONCLUSIONS: Knowledge deficits exist in the academic surgical community about the role and requirements of the FDA and local IRBs for conducting clinical research. Further study is required to determine the reasons for this deficit and to identify appropriate interventions. 相似文献
10.
JC Posnick MD Wells JM Drake JR Buncic D Armstrong 《Canadian Metallurgical Quarterly》1993,19(5):260-266
Fibrous dysplasia is an abnormal fibroosseous process of bone of unknown cause. The incidence of skull involvement varies, painless enlargement being the most common presenting symptom. Change in vision is a rare but recognized finding. We report a 3-year-old boy with extreme fibrous dysplasia involving the skull base, who presented with blindness. He underwent exposure osteotomies of the frontal bones and orbits to provide access for skull base tumor removal. The orbital roofs were reconstructed with microplate-fixed cranial grafts. One and one half years after tumor excision followed by immediate reconstruction, the boy retains facial symmetry, and his ocular function has not deteriorated. 相似文献