全文获取类型
收费全文 | 7712篇 |
免费 | 41篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 38篇 |
综合类 | 2篇 |
化学工业 | 355篇 |
金属工艺 | 218篇 |
机械仪表 | 63篇 |
建筑科学 | 102篇 |
矿业工程 | 86篇 |
能源动力 | 75篇 |
轻工业 | 230篇 |
水利工程 | 23篇 |
石油天然气 | 3篇 |
无线电 | 289篇 |
一般工业技术 | 442篇 |
冶金工业 | 5472篇 |
原子能技术 | 34篇 |
自动化技术 | 322篇 |
出版年
2021年 | 39篇 |
2020年 | 23篇 |
2019年 | 32篇 |
2018年 | 28篇 |
2017年 | 29篇 |
2016年 | 40篇 |
2015年 | 27篇 |
2014年 | 53篇 |
2013年 | 157篇 |
2012年 | 75篇 |
2011年 | 106篇 |
2010年 | 93篇 |
2009年 | 106篇 |
2008年 | 89篇 |
2007年 | 109篇 |
2006年 | 110篇 |
2005年 | 67篇 |
2004年 | 69篇 |
2003年 | 73篇 |
2002年 | 57篇 |
2001年 | 57篇 |
2000年 | 70篇 |
1999年 | 182篇 |
1998年 | 1662篇 |
1997年 | 1016篇 |
1996年 | 627篇 |
1995年 | 346篇 |
1994年 | 324篇 |
1993年 | 381篇 |
1992年 | 78篇 |
1991年 | 91篇 |
1990年 | 106篇 |
1989年 | 102篇 |
1988年 | 93篇 |
1987年 | 97篇 |
1986年 | 82篇 |
1985年 | 69篇 |
1984年 | 33篇 |
1983年 | 36篇 |
1982年 | 41篇 |
1981年 | 62篇 |
1980年 | 76篇 |
1979年 | 27篇 |
1978年 | 34篇 |
1977年 | 151篇 |
1976年 | 275篇 |
1975年 | 29篇 |
1974年 | 32篇 |
1973年 | 32篇 |
1972年 | 24篇 |
排序方式: 共有7754条查询结果,搜索用时 15 毫秒
91.
A 23-year-old woman suffering from multiple sclerosis (MS) was given a course of 6 injections (0.5 U) of mumps transfer factor (TF) at 2-weekly intervals. The patient's symptoms improved dramatically and during the 10 months since treatment was instituted, no exacerbations have occurred. The possible aetiological role of paramyxoviruses in MS and the use of TF in the treatment of the disease are discussed. MS is however, a disease of exacerbations and spontaneous remissions, and despite our promising findings in this patient we wish to refrain from hailing mumps TF as a possible cure for this notorious disease. 相似文献
92.
Fifty-three patients 3 1/2 to 20 years of age with steroid-dependent idiopathic nephrotic syndrome (INS) were treated with cyclophosphamide and prednisone. Two dosage schedules were used: a short course (SC) at 3 to 5 mg/kg/day for six to eight weeks and a longer course (LC) at 3 to 5 mg/kg/day for eight weeks followed by 1.5 to 2.5 mg/kg for an additional four weeks. Prednisone was administered concurrently at 50 to 75 mg/sq M every other day. Twenty-nine patients were in the SC group and 24 in the LC group. The two groups did not differ significantly as to age at onset of idiopathic nephrosis nor as to the duration of the INS prior to cyclophosphamide therapy. All patients were followed for a minimum of 42 months after cyclophosphamide therapy. The SC was associated with a higher relapse rate during the first year than the LC (42% and 8% respectively, .01 larger than P less than .025). At 42 months 63% of the LC group were in remission compared with 21% in the SC group. 相似文献
93.
The production of tumor-specific cell-mediated cytotoxicity following in vitro sensitization of C57BL spleen cells against a syngeneic 3LL Lewis lung carcinoma was studied. Lymphocytes were sensitized on monolayers of the tumor cells for 4-5 days. The cytotoxicity was assayed by measuring the reduction in 3H-leucine and 3H-thymidine incorporation by target cells after interaction with the sensitized lymphocytes. Spleen lymphocytes sensitized on monolayers of 3LL tumor cells caused a high extent of lysis; such cells tested on C57BL or C3H fibroblast targets evoked only a low level of cytotoxicity. C57BL spleen cells sensitized on C57BL fibroblasts caused a low level of cytotoxicity when tested on a 3LL target. Thus cytotoxicity appeared to be tumor specific. The reduced incorporation into protein and DNA of target tumor cells caused by the sensitized lymphocytes was a measure of cell injury, which was more sensitive than direct cell count or uptake of 51CR. Lymphocytes from syngeneic tumor-bearing mice, tested 13-25 days after tumor inoculation, did not manifest in vitro cytotoxicity. On the contrary, such lymphocytes sometimes appeared to have a promoting effect on the tumor cells. 相似文献
94.
This paper explains the Canadian decision process following the isolation and identification of A/New Jersey/8/76 at Fort Dix, New Jersey in February 1976. The cause for concern was the emergence of a swine-like strain related to that which caused the 1918-19 pandemic, together with proved man-to-man transmission. This concern was reinforced since all new influenza A strains known to have infected the number of persons involved at Fort Dix have become strains of epidemic importance. The Fort Dix outbreak gave sufficient warning to allow implementation of a national vaccination program, to prevent and protect against influenza. In the past such an opportunity had not occurred, and vaccine use had, at best, constituted an intervention in the course of an outbreak. The National Advisory Committee on Immunizing Agents had all available information when it reached its decision to recommend vaccination with bivalent (A/Victoria and A/New Jersey) or with monovalent (A/New Jersey) vaccine for selective, high-risk groups. This was an independent, scientifically based decision. 相似文献
95.
96.
A scheme for attachment of psychiatric nurses from hospital to group practice in Oxford is described. One community psychiatric nurse can work satisfactorily with eight general practitioners covering a population of about 18,000. From analysis of a working year, it is concluded that this arrangement improves the care of patients in the community by providing psychiatric help at times when it was previously unavailable or unacceptable.The implications of such a scheme for the workings of the primary health care team and the hospital psychiatric service are considered, and a case is made for a further study involving a comparison between practices with and without the attachment of a community psychiatric nurse. 相似文献
97.
98.
Lung function and immunologic studies have been performed in 9 patients with bird breeder's hypersensitivity pneumonitis at the time of diagnosis and at intervals from 8 to 30 months after they ceased exposure to the provoking antigen. All 9 patients had evidence of small airway obstruction at the time of diagnosis. Complete recovery of lung function occurred in 4 patients. The other 5 all had evidence of interstitial damage; 3 of them had progressive increase in the degree of airway obstruction, and one had progressive loss of elastic recoil. The patients were nonsmokers, and these progressive changes could not be explained by occult exposure to antigen because the tests of immunologic sensitivity to relevant avian antigens became negative. Neither the nature or degree of lung function abnormality nor the form of clinical presentation was related to the development of residual damage. The period of exposure to antigen after symptoms developed and the age of the patient appeared to be the most important factors determining recovery of lung function. 相似文献
99.
During International Biological Programme studies in Papua New Guinea, on Karkar Island and at Lufa in the Eastern Highlands, information on anthropometric, biochemical and genetic characteristics was collected from the same individuals. Use has been made of this special situation to investigate whether any associations exist between genetic markers and anthropometric and biochemical variation. Those found, and which satisfy criteria established to help in distinguishing real from chance associations, include: P with haemoglobin concentration and serum albumin and cholesterol levels; acid phosphatase with serum albumin level and haemoglobin concentration; anhaptoglobinaemia and serum globulin level; haemoglobin J-Tongariki with serum phosphorus level. The associations are discussed in terms of their arising from the direct result of environmental factors modifying gene expression, chance concordance of environmental and genetic variation, or pleiotropy. 相似文献
100.
The effect of actinomycin-D (AMD) on radiation damage repair was studied in plateau phase V79 Chinese hamster cells. Sublethal radiation damage repair, as demonstrated by survival fluctuations following two x-ray exposures separted by time, was observed in our plateau phase cells. Plateau phase cells exposed to 0.01-0.04 mug/ml AMD (a nontoxic regimen to 8 hours) between x-ray exposures were less able to repair sublethal damage. If plateau phase cells were plated at low dilutions into fresh medium (conditions for resuming exponential growth) immediately after the first x-ray dose, and exposed to 0.01--0.04 mug/ml AMD until the second dose, inhibition of sublethal damage repair and additional cell killing were observed particularly at 0.04 mug/ml AMD. It is suggested that radiation-drug damage interactions should be studied in plateau phase cells and in cells resuming exponential growth after plateau phase (possibly analogous to "recruitment"), as well as in exponential phase cultures. 相似文献