全文获取类型
收费全文 | 1719篇 |
免费 | 242篇 |
国内免费 | 174篇 |
出版年
2024年 | 5篇 |
2023年 | 51篇 |
2022年 | 46篇 |
2021年 | 107篇 |
2020年 | 112篇 |
2019年 | 137篇 |
2018年 | 83篇 |
2017年 | 89篇 |
2016年 | 67篇 |
2015年 | 103篇 |
2014年 | 142篇 |
2013年 | 169篇 |
2012年 | 80篇 |
2011年 | 95篇 |
2010年 | 67篇 |
2009年 | 80篇 |
2008年 | 79篇 |
2007年 | 70篇 |
2006年 | 81篇 |
2005年 | 51篇 |
2004年 | 45篇 |
2003年 | 46篇 |
2002年 | 35篇 |
2001年 | 27篇 |
2000年 | 26篇 |
1999年 | 22篇 |
1998年 | 13篇 |
1997年 | 28篇 |
1996年 | 17篇 |
1995年 | 18篇 |
1994年 | 19篇 |
1993年 | 20篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有2135条查询结果,搜索用时 31 毫秒
71.
Hongsheng Wang Zuoting Yan Xiaohu Wu Yong Zhang Yubing Wei Xingxu Zhao 《Animal Reproduction》2021,18(1)
Clinical endometritis (CE) is a major cause in affecting the reproductive performance of dairy cows. The objectives of this study were to ascertain the prevalence of CE and to evaluate the effect of CE on reproductive performance in dairy cows using vaginal discharge score (VDS) grading system. 803 dairy cows were examined by vaginoscope with 4-point VDS at 26 ± 3 days in milk (DIM) and classified into six groups: non-endometritis with VDS 0 (control; CON), endometritis with VDS 1 (MEM), non-treated endometritis with VDS 2 (NTME), treated endometritis with VDS 2 (TME), non-treated endometritis with VDS 3 (NTPE), and treated endometritis with VDS 3 (TPE). Cows in TME and TPE groups were treated with 200 mL of 50% dextrose solution by intrauterine infusion. The prevalence of CE was 33% at 26 ± 3 DIM. Binary logistic regression analysis revealed cows in MEM, NTME and NTPE groups had a less likelihood of first artificial insemination (AI) pregnancy than those in CON group (P < 0.05). Kaplan-Meier survival curves for days open were statistically different (P = 0.004). In Cox regression model, cows in NTME and NTPE groups had a reduced pregnancy rate than those in CON group (P < 0.05). The hazard of pregnancy in NTME group was lower than that in TME group (P = 0.044). Similarly, it was lower for the hazard of pregnancy in NTPE group than in TPE group (P = 0.048). Cows in MEM, NTME, and NTPE groups required more services per pregnancy than those in CON group (P < 0.05). In conclusion, CE examined by the VDS grading system impaired reproductive performance, and mild endometritis with VDS 1 should be treated in the early postpartum period to ameliorate fertility in dairy herds. 相似文献
72.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel betacoronavirus, caused a pandemic leading to a standstill of nearly all global activities. There are some controversies on the production of specific immunoglobulin M (IgM) and IgG antibodies after the infection with SARS-CoV-2. This paper seeks to elaborate on the potential application of IgM and IgG antibodies and the viral antigens for the diagnosis and the course of the disease as well as the recurrence of positive nucleic acid tests after discharge. 相似文献
73.
《IRBM》2021,42(5):345-352
Available clinical methods for heart failure (HF) diagnosis are expensive and require a high-level of experts intervention. Recently, various machine learning models have been developed for the prediction of HF where most of them have an issue of over-fitting. Over-fitting occurs when machine learning based predictive models show better performance on the training data yet demonstrate a poor performance on the testing data and the other way around. Developing a machine learning model which is able to produce generalization capabilities (such that the model exhibits better performance on both the training and the testing data sets) could overall minimize the prediction errors. Hence, such prediction models could potentially be helpful to cardiologists for the effective diagnose of HF. This paper proposes a two-stage decision support system to overcome the over-fitting issue and to optimize the generalization factor. The first stage uses a mutual information based statistical model while the second stage uses a neural network. We applied our approach to the HF subset of publicly available Cleveland heart disease database. Our experimental results show that the proposed decision support system has optimized the generalization capabilities and has reduced the mean percent error (MPE) to 8.8% which is significantly less than the recently published studies. In addition, our model exhibits a 93.33% accuracy rate which is higher than twenty eight recently developed HF risk prediction models that achieved accuracy in the range of 57.85% to 92.31%. We can hope that our decision support system will be helpful to cardiologists if deployed in clinical setup. 相似文献
74.
The ability to add or delete specific genes in swine will likely provide considerable benefits not just to agriculture but also to medicine, where pigs have potential as models for human disease and as organ donors. Here we have transferred nuclei from a genetically modified fibroblast cell line to porcine oocytes, matured in vitro under defined culture conditions, to create piglets expressing enhanced green fluorescent protein. The nuclear transfer-derived piglets were of normal size, although some mild symptoms of “large offspring syndrome” were evident. These experiments represent a next step towards creating swine with more useful genetic modifications. 相似文献
75.
《Expert review of proteomics》2013,10(2):131-133
This special focus issue of Expert Review of Proteomics invites key opinion leaders to report their recent findings and views on the important topic of translating potential proteomic biomarkers to clinically useful, regulator-approved biomarkers: a challenging journey. The issue also highlights the difficulties associated with and the way forward in the discovery of proteomic cancer biomarkers for clinical applications, as well as presenting recent original research in the field. 相似文献
76.
77.
Takashi Sakamoto Akio Kobori Masako Shigezawa Yasutaka Amitani Maiko Higuchi Akira Murakami 《Nucleosides, nucleotides & nucleic acids》2013,32(10-12):1659-1664
We developed a bispyrene-conjugated 2 ′-O-methyloligoribonucleotide as an RNA-specific RNA-probe. The probe hybridized with the complementary RNA, greatly enhancing fluorescence and discriminating RNA from DNA. The assay was carried out in homogeneous aqueous media without removing the unbound probe from the detection solution. This homogeneous fluorescence assay also discriminated mismatch sequences in the target RNA. These pyrene probes could possess high potential to detect RNA in biological specimens simply. 相似文献
78.
《Biomarkers》2013,18(7):668-670
With the recent progresses of the information and communication technologies, biosensors and nanotechnologies, the access to continuing health monitoring is becoming real. The development of efficient, accurate and interactive solutions integrating biomarkers for continuing health monitoring might contribute to an improved care of some chronic diseases like hypertension, diabetes or heart failure. Continuing health monitoring might also enhance the efficiency and safety of patient’s treatments. 相似文献
79.
80.
《Biomarkers》2013,18(6):539-544
Introduction: Elevated neutrophil to lymphocyte ratio has been identified as a prognostic indicator in malignancies whereas; its association with extremity and trunk soft tissue sarcoma remain unclear. The aim of this study is to determine the utility of full blood neutrophil lymphocyte ratio (NLR) in preoperative diagnosis and its predictive value for survival in patients managed for soft tissue sarcoma of the trunk and extremities.Method: 223 patients who presented with a soft tissue tumor were retrospectively reviewed. The study period was from January 2002–December 2009. Preoperative NLR as well as demographics, clinical and histopathological data were analysed.Results: Full blood NLR was significantly higher in patient with a soft tissue sarcoma compared to benign soft tissue tumors (p < 0.001). Cox regression analysis demonstrated that elevated NLR >5 (p < 0.05) may be an adverse prognostic factor for Overall Survival.Conclusion: The preoperative NLR is a simple, investigation predicting the preoperative diagnosis of a soft tissue sarcoma and a predictor of worse overall survival for patient with a soft tissue sarcoma. 相似文献