首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   65172篇
  免费   3393篇
  国内免费   50篇
林业   3768篇
农学   2439篇
基础科学   397篇
  8346篇
综合类   7115篇
农作物   2592篇
水产渔业   3581篇
畜牧兽医   35680篇
园艺   914篇
植物保护   3783篇
  2018年   1075篇
  2017年   1214篇
  2016年   1170篇
  2015年   1083篇
  2014年   1216篇
  2013年   2468篇
  2012年   2224篇
  2011年   2494篇
  2010年   1542篇
  2009年   1442篇
  2008年   2098篇
  2007年   2080篇
  2006年   1980篇
  2005年   2539篇
  2004年   2328篇
  2003年   2101篇
  2002年   1646篇
  2001年   2443篇
  2000年   2219篇
  1999年   1839篇
  1998年   693篇
  1997年   627篇
  1996年   607篇
  1995年   677篇
  1994年   579篇
  1993年   562篇
  1992年   1348篇
  1991年   1507篇
  1990年   1567篇
  1989年   1434篇
  1988年   1353篇
  1987年   1306篇
  1986年   1277篇
  1985年   1191篇
  1984年   984篇
  1983年   779篇
  1982年   545篇
  1979年   889篇
  1978年   687篇
  1977年   536篇
  1976年   579篇
  1975年   597篇
  1974年   719篇
  1973年   690篇
  1972年   724篇
  1971年   687篇
  1970年   661篇
  1969年   613篇
  1968年   549篇
  1967年   592篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Lymphangiosarcoma (LAS) is an uncommon malignant neoplasia arising from lymphatic endothelium; little information exists regarding therapy. Single institutional retrospective review for canine LAS histopathology diagnoses over a 15‐year period yielded 12 dogs. Ten dogs were presented for a mass and/or swelling at cervical, trunk or limb regions. Prior to diagnosis, 10 dogs received empiric wound therapy. Cytology performed in 10 consisted of mild inflammation. Survival ranged from 60, 168 and 876 days for three dogs with palliation; 90 days with prednisone in one; 182 days with chemotherapy in one; 240, 267, 487, 630 and 941 days for five receiving surgery; and 574 days for one receiving surgery, radiation and chemotherapy. One dog is alive with recurrence at 243 days following surgery and carboplatin chemotherapy. Clinical improvement existed in LAS dogs receiving multimodal therapies. Early tissue biopsies are recommended for progressive oedematous lesions of unknown origin.  相似文献   
993.
Canine transmissible venereal tumour (CTVT) is a contagious venereal tumour of dogs, commonly observed in dogs that are in close contact with one another, or in stray and wild dogs that exhibit unrestrained sexual activity. CTVT represents a unique, naturally transmissible, contagious tumour, where the mutated tumour cell itself is the causative agent and perpetuates as a parasitic allograft in the host. Clinical history, signalment and cytological features are often obvious for establishing a diagnosis though biopsy and histological examination may be needed in atypical cases. Most cases are curable with three intravenous injections of vincristine sulphate at weekly intervals. The role of stray and wild dogs makes the disease difficult to control and necessitates sustained animal birth control in stray dogs along with prompt therapy of the affected dogs. This review captures the manifold developments in different areas embracing this fascinating tumour, including its biology, diagnosis and therapeutic alternatives.  相似文献   
994.
The immunological biomarkers profiles were evaluated using Luminex as putative measures to monitor canine mammary carcinomas (MCs). Forty female dogs were categorized into benign mixed tumour (MC‐BMT = 28) and mammary carcinoma (MC=12). The ascendant biomarker signatures were used to compare the groups. For example, a higher frequency of MC‐BMT animals producing IL‐6, CXCL‐8 and CXCL‐10 was observed, whereas for the MC group IL‐2 and CXCL‐8 were detected. MC‐BMT animals without metastasis had an increase in the levels of IL‐2, CXCL‐8, CXCL‐10, IL‐6, TNF‐α, IL‐15 and a decrease in IL‐10 and CXCL‐8. MC‐BMT animals with metastasis showed only an increase in CXCL‐10 and a decrease in IL‐18. After comparing the ascendant signatures following the presence of metastasis in both groups, a higher frequency of dogs exhibiting IL‐10 production was observed. Pearson correlation (P = 0.0273) and receiver operating characteristic (ROC) curve analysis revealed that this pattern was associated with worse outcome and lower survival rates in MC animals.  相似文献   
995.
996.
The primary study objective was to determine whether clinical examination and magnetic resonance imaging (MRI) can underestimate canine gliomatosis cerebri (GC); we also investigated immunohistochemical features. Seven dogs with GC were studied; four recruited specifically because of minimal MRI changes. Neuroanatomic localization and the distribution of MRI, gross and sub‐gross lesions were compared with the actual histological distribution of neoplastic cells. In six cases, clinical examination predicted focal disease and MRI demonstrated a single lesion or appeared normal. Neoplastic cells infiltrated many regions deemed normal by clinical examination and MRI, and were Olig2‐positive and glial fibrillary acid protein‐negative. Four dogs had concurrent gliomas. GC is a differential diagnosis for dogs with focal neurological deficits and a normal MRI or a focal MRI lesion. Canine GC is probably mainly oligodendrocytic. Type II GC, a solid glioma accompanying diffuse central nervous system neoplastic infiltration, occurs in dogs as in people.  相似文献   
997.
998.
999.
1000.
The permeable nature of frog skin presents an alternative route for the delivery of therapeutic chemicals to treat disease in frogs. However, although therapeutic chemicals are often topically applied to the skin of frogs, their pharmacokinetics have rarely been reported. To provide evidence to guide both candidate drug and formulation selection, we highlight factors expected to influence percutaneous absorption through frog skin, including the anatomy and physiology of the skin and the physicochemical properties of applied therapeutic chemicals. Importantly, we also highlight the effects of the formulation on percutaneous absorption, especially the inclusion of potential penetration enhancers as excipients. Finally, we collate empirical data on the topical application of various therapeutic chemicals in postmetamorphic frogs and show that, in contrast to mammalian species, even large chemicals (i.e. >500 Da) and those with a wide range of log P values (?4 through +6) are likely to be absorbed percutaneously. Topical application in frogs thus promises a convenient and effective method for delivering systemic treatments of a diverse range of chemicals; however, further experimental quantification is required to ensure optimal outcomes.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号