全文获取类型
收费全文 | 85003篇 |
免费 | 6683篇 |
国内免费 | 4902篇 |
出版年
2023年 | 960篇 |
2022年 | 1115篇 |
2021年 | 3812篇 |
2020年 | 2793篇 |
2019年 | 3453篇 |
2018年 | 3442篇 |
2017年 | 2532篇 |
2016年 | 3584篇 |
2015年 | 5314篇 |
2014年 | 6095篇 |
2013年 | 6688篇 |
2012年 | 7816篇 |
2011年 | 6903篇 |
2010年 | 4178篇 |
2009年 | 3688篇 |
2008年 | 4279篇 |
2007年 | 3892篇 |
2006年 | 3398篇 |
2005年 | 2841篇 |
2004年 | 2374篇 |
2003年 | 2071篇 |
2002年 | 1757篇 |
2001年 | 1546篇 |
2000年 | 1539篇 |
1999年 | 1382篇 |
1998年 | 749篇 |
1997年 | 716篇 |
1996年 | 715篇 |
1995年 | 673篇 |
1994年 | 623篇 |
1993年 | 435篇 |
1992年 | 727篇 |
1991年 | 580篇 |
1990年 | 537篇 |
1989年 | 434篇 |
1988年 | 365篇 |
1987年 | 343篇 |
1986年 | 269篇 |
1985年 | 291篇 |
1984年 | 175篇 |
1983年 | 190篇 |
1982年 | 116篇 |
1981年 | 94篇 |
1980年 | 71篇 |
1979年 | 113篇 |
1977年 | 105篇 |
1976年 | 76篇 |
1975年 | 68篇 |
1974年 | 94篇 |
1973年 | 75篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
5.
L. Crispoltoni S. Porcellati A. M. Del Pino A. Orlacchio G. Coata S. Arnone E. Torlone B. Cappuccini G. C. Di Renzo A. Orlacchio 《Cell biochemistry and function》2014,32(1):87-95
Several epidemiological studies showed that gestational diabetes mellitus is the most frequent metabolic disorder of pregnancy, the pathogenesis of which has yet to be completely clarified. The aim of this study was to investigate the presence and processing of caspase 3 (Casp3) and poly(ADP‐ribose) polymerase 1 (PARP1) in cord blood lymphocytes as markers of apoptosis in relation to glycaemic control during intrauterine life. Our results showed a specific positive correlation between the levels of active Casp3 (17–19 kDa) and the inactive form of PARP1 (89 kDa) in lymphocytes isolated from newborn babies of diabetic women with unbalanced glycaemic control, with a direct correlation between the activation of casp3 and the inactivation of PARP1, that makes lymphocytes unresponsive towards lipopolysaccharide stimulation, highlighting an altered functional response. Besides more studies are required to fully correlate the activation of the apoptotic process during the intrauterine life with the foetal health later in life, our study indicates that a cord blood lymphocyte, an easily accessible source, is informative about the activation of apoptotic stimuli in circulating cells of newborn babies in relation to the glycaemic control reached by the mother during pregnancy. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
6.
7.
An experiment was conducted to investigate the effect of phytase transgenic corn (PTC) on intestinal microflora, and the fate of transgenic DNA and protein in the digesta and tissues of broilers. A total of 160 1-day-old Arbor Acres commercial male broilers were randomly assigned to 20 cages (8 chicks per cage) with 10 cages (replicates) for each treatment. Birds were fed with a diet containing either PTC (54.0% during 1–21 days and 61.0% during 22–42 days) or non-transgenic isogenic control corn (CC) for a duration of 42 days. There were no significant differences (P>0.05) between birds fed with the PTC diets and those fed with the CC diets in the quantities of aerobic bacteria, anaerobic bacteria, colibacillus and lactobacilli, or microbial diversities in the contents of ileum and cecum. Transgenic phyA2 DNA was not detected, but phyA2 protein was detected in the digesta of duodenum and jejunum of broilers fed with the PTC diets. Both transgenic phyA2 DNA and protein fragments were not found in the digesta of the ileum and rectum, heart, liver, kidney, and breast or thigh muscles of broilers fed with the PTC diets. It was concluded that PTC had no adverse effect on the quantity and diversity of gut microorganisms; Transgenic phyA2 DNA or protein was rapidly degraded in the intestinal tract and was not transferred to the tissues of broilers. 相似文献
8.
A computer program, which runs on MS-DOS personal computers, is described that assists in the design of synthetic genes coding for proteins. The goal of the program is the design of a gene which (i) contains as many unique restriction sites as possible and (ii) uses a specific codon usage. The gene designed according to the criteria above is (i) suitable for 'modular mutagenesis' experiments and (ii) optimized for expression. The program 'reverse-translates' protein sequences into degenerated DNA sequences, generates a map of potential restriction sites and locates sequence positions where unique restriction sites can be accommodated. The nucleic acid sequence is then 'refined' according to a specific codon usage to remove any degeneration. Unique restriction sites, if potentially present, can be 'forced' into the degenerated nucleic acid sequence by using 'priority codes' assigned to different restriction sequences. 相似文献
9.
10.
A recursive least squares based on Multi-model is proposed for non-uniformly sampled-data nonlinear (NUSDN) systems. The corresponding state space model of an NUSDN system is derived using lifting technique. Taking advantage of the Fuzzy c-Mean Clustering algorithm, NUSDN is divided into several local models. The basic idea is that the NUSDN system is viewed as a model switching system under a given rule. Once the local models are identified, the global model is determined. A pH neutralization process validate the performance of the proposed algorithm. 相似文献