全文获取类型
收费全文 | 3401篇 |
免费 | 21篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 194篇 |
金属工艺 | 17篇 |
机械仪表 | 14篇 |
建筑科学 | 36篇 |
矿业工程 | 1篇 |
能源动力 | 14篇 |
轻工业 | 151篇 |
水利工程 | 15篇 |
石油天然气 | 4篇 |
无线电 | 119篇 |
一般工业技术 | 113篇 |
冶金工业 | 2606篇 |
原子能技术 | 4篇 |
自动化技术 | 127篇 |
出版年
2021年 | 11篇 |
2019年 | 9篇 |
2015年 | 8篇 |
2014年 | 26篇 |
2013年 | 38篇 |
2012年 | 18篇 |
2011年 | 39篇 |
2010年 | 42篇 |
2009年 | 29篇 |
2008年 | 18篇 |
2007年 | 20篇 |
2006年 | 21篇 |
2005年 | 24篇 |
2004年 | 13篇 |
2003年 | 21篇 |
2002年 | 17篇 |
2001年 | 23篇 |
2000年 | 19篇 |
1999年 | 79篇 |
1998年 | 740篇 |
1997年 | 419篇 |
1996年 | 292篇 |
1995年 | 176篇 |
1994年 | 150篇 |
1993年 | 187篇 |
1992年 | 47篇 |
1991年 | 31篇 |
1990年 | 38篇 |
1989年 | 39篇 |
1988年 | 52篇 |
1987年 | 52篇 |
1986年 | 46篇 |
1985年 | 60篇 |
1984年 | 29篇 |
1983年 | 15篇 |
1982年 | 25篇 |
1981年 | 28篇 |
1980年 | 48篇 |
1979年 | 21篇 |
1978年 | 25篇 |
1977年 | 89篇 |
1976年 | 215篇 |
1975年 | 19篇 |
1974年 | 6篇 |
1973年 | 13篇 |
1972年 | 8篇 |
1970年 | 7篇 |
1969年 | 8篇 |
1968年 | 8篇 |
1967年 | 6篇 |
排序方式: 共有3423条查询结果,搜索用时 15 毫秒
31.
Data from the Cancer Registry of Slovenia were used in a cohort study to determine whether the incidence of second primary cancers in patients with first primary breast cancer differs from the incidence expected in the general population. Special interest was given to long-term survivors. The expected numbers of second primary cancers were calculated by multiplying the number of appropriate person-years at risk by the corresponding age- and calendar-period-specific cancer incidence rates for women in Slovenia. The risk of a second primary cancer was expressed as the standardized incidence ratio (SIR). Of the 8,917 patients newly diagnosed in the period 1961-85 and followed-up to the end of 1994, 547 (6.2 percent) developed second primary cancers, whereas 410 (4.7 percent) were expected (SIR = 1.3, 95 percent confidence interval [CI] = 1.2-1.4). The risk was higher among younger patients. In long-term survivors, the risk was increased significantly for second primary cancer of the breast (SIR = 1.4, CI = 1.1-1.7), lung cancer (SIR = 1.6, CI = 1.1-2.3), melanoma (SIR = 2.7, CI = 1.5-4.4) and non-melanoma skin cancers(SIR = 2.0, CI = 1.6-2.4), corpus uteri cancer(SIR = 1.6, CI = 1.2-2.1), ovarian cancer(SIR = 2.3, CI = 1.7-3.0), and thyroid cancer (SIR = 2.5, CI = 1.2-4.6). Our results confirm the findings of several cohort studies carried out in Europe, the United States, and Japan, indicating that breast cancer patients should be monitored carefully for the occurrence of second primary cancers. 相似文献
32.
R.B. Pearson 《Food chemistry》1982,8(2):85-96
Manufacture of polyvinyl chloride (PVC) in western Europe for all applications is now almost 4 m tonnes and the UK accounts for about 400 kt of this.The aim of this paper is to illustrate the relative importance of PVC as a packaging material where, in the UK for example, for food packaging it accounts for almost 40 kt (10%) of the PVC used.The different types of PVC packaging material—bottles, foil, cling film and cap sealing—and their method of manufacture are described, together with the range of food packaging applications in which they are used. The physical properties of PVC are described and, additionally, its cost and competitiveness with other materials are compared. The chemical nature of PVC compositions arising from the addition of heat stabilisers and plasticisers to achieve the desired properties is also described, with particular reference to heat stability.With the VCM toxicity issue now behind us, and PVC polymer with a maximum level of 1 ppm vinyl chloride monomer (VCM) being supplied for food packaging, PVC must be the most stringently controlled and thoroughly researched material for food packaging. Recent developments in polymerisation technology and polymer manufacture, which have enabled this level to be achieved, are briefly described.The current situation on the global migration issue, on which attention is currently focused, not only for plasticised PVC, but also other packaging materials as well, is briefly reviewed. 相似文献
33.
Heritabilities were estimated for lactation average log, base 2, somatic cell count from cows with four or more tests in each lactation. Estimates were for first, second, and third or later parities (defined by age at calving) individually and for mixed parities. Estimates were from sire components of variance with numbers of sires and daughters of 406 and 22,140; 337 and 8,659; 311 and 6,122; and 310 and 10,217 for mixed, first, second, and third or later parities, respectively.Both sire and error components of variance increased with parity. Heritabilities were .18, .09, .10, and .29, for mixed, first, second, and third or later parities. 相似文献
34.
RD Robinson 《Canadian Metallurgical Quarterly》1993,4(2):70-76
The safety and pharmacokinetics of L-627, a new injectable carbapenem antibiotic, were evaluated in healthy volunteers. In single-dose studies, 20, 40, 80, 150, 300 and 600 mg of L-627 were administered by i.v. infusions over 1 hour. Plasma concentration-time profiles were well described with a two-compartment open model. The half-life of elimination from plasma was 1.3 +/- 0.8 (mean +/- SD) hour, and the Cmax and AUC paralleled the doses given. The mean urinary recovery of unchanged L-627 within the first 12 hours was 63.1 +/- 2.7% of the dose. In the multiple-dose studies, 300 mg of L-627 (i.v. over 1 hour) was administered every 12 hours, 11 times in total and 600 mg of L-627 was administered every 12 hours, 9 times in total. No discernible accumulation of the drug in plasma was observed. There were no subjective or objective abnormal findings definitely attributable to the drug except that one subject in one of the multiple-dose regimens (300 mg b.i.d.) showed only a slight elevation of transaminase value, although the elevated value promptly recovered after completion of dosing. No abnormality was observed in the other multiple-dose regimen (600 mg b.i.d.). From these results, L-627 was concluded to be safe and well tolerated. 相似文献
35.
36.
RW Sidwell DF Smee RP Warren JH Huffman BJ Gilbert RA Burger FC Pearson 《Canadian Metallurgical Quarterly》1993,20(4):279-292
ImuVert, a sterile preparation composed primarily of Serratia marcescens membrane vesicles and ribosomes, was significantly inhibitory to murine cytomegalovirus (MCMV) infections in BALB/c mice. Antiviral activity was manifested as increased survivor number and decreased recoverable virus titers in spleens, lungs and salivary glands. Treatments were intraperitoneal (i.p.) beginning 24 h pre, 4 h post- or 24 h post-virus inoculation and then repeated 4 days later. Doses of 5, 16 or 50 micrograms/mouse were effective; 160 micrograms/mouse, which caused host weight loss in toxicity controls, was not inhibitory to the infection. A single i.p. treatment of mice substantially augmented natural killer (NK) cell activity and increased total B-cells, while reducing total T- and T-helper cells. A late (48 h) decline in T-cell function and transient increases in B-cell function were observed in the treated animals. Serum interferon was not induced. Mice pretreated with anti-asialo GM1 antibody to reduce their NK cell populations, then infected with MCMV and treated with ImuVert were protected to the same degree as normal animals. Severe combined immunodeficient mice infected with MCMV and treated with ImuVert were not protected from the infection. These data suggest ImuVert to act by a mechanism other than NK cell activation in preventing MCMV infections. 相似文献
37.
38.
RD Spruell ER Ferguson JJ Clymer WV Vicente CP Murrah WL Holman 《Canadian Metallurgical Quarterly》1995,41(3):M636-M641
Intravascular perfluorochemical (PFC) emulsions together with a high oxygen (O2) tension may increase the delivery of dissolved O2 to useful levels. A severely anemic model of cardiopulmonary bypass (CPB) was used to test the hypothesis that a novel PFC emulsion (PFCE; Oxygent [Alliance Pharmaceutical Corp., San Diego, CA] 90% w/v perflubron) used at a high PO2 during bypass delivers sufficient O2 to ameliorate hypoxic myocardial contractile dysfunction. Acutely anemic dogs (N = 42; hematocrit = 15.8 +/- 0.6% [mean +/- SEM] before CPB and 10.9 +/- 0.1% during CPB) were divided into four groups. Group 1 was a control (n = 12). As CPB was initiated, groups 2 (n = 10), 3 (n = 10), and 4 (n = 10) had 1.35 g PFC.kg-1, 2.7 g PFC.kg-1, or 5.4 g PFC.kg-1 added via the venous return cannula. Pre-CPB and post-CPB cardiac function was measured by the first derivative of left ventricular pressure (dP/dtmax). The dP/dtmax on separation from CPB was: group 1, 619 +/- 96; group 2, 738 +/- 56; group 3, 782 +/- 101; and group 4, 828 +/- 100 (p < 0.05 groups 3 and 4 versus group 1). Mortality during the first hour after separation from CPB was higher in group 1 than in PFCE treated dogs; however, this trend did not attain statistical significance (p < 0.065). The PFC dose was higher in survivors than in nonsurvivors (2.6 +/- 0.4 g PFC.kg-1 versus 1.2 +/- 0.5 g PFC.kg-1; p < 0.05). A PFCE used at a high PO2 provides sufficient physically dissolved O2 to relieve myocardial hypoxic injury in a severely anemic model of CPB. Current PFCEs are effective O2 carriers. This finding suggests that they can be used as a temporary erythrocyte substitute to diminish the need for allogeneic transfusions during cardiac operations. 相似文献
39.
John Pearson 《The Visual computer》1988,4(1):19-26
A discussion of the historical and aesthetic questions raised by the Fine Arts community regarding the uses of the computer by artists, its limitations and its potential. Creating a texture and context for this discussion necessitated the weaving into this discussion the role of technology, science, mathematics, the humanities, and aesthetics in the visual arts. 相似文献
40.